Iron-based amorphous crystalline powder Fe_(78)Si_(9)B_(13)^(AP)is used as a permeability reaction barrier(PRB)combined with an electrokinetic method(EK-PRB)to study the removal rate of Cu in contaminated soil.After t...Iron-based amorphous crystalline powder Fe_(78)Si_(9)B_(13)^(AP)is used as a permeability reaction barrier(PRB)combined with an electrokinetic method(EK-PRB)to study the removal rate of Cu in contaminated soil.After treating Cucontaminated soil for 5 days under different voltage gradients and soil water content,the soil pH is between 3.1 and 7.2.The increase of voltage gradient and soil water content can effectively promote the movement of Cu^(2+) to the cathode.The voltage gradient is 3 V/cm,and the water content of 40%is considered to be an optional experimental condition.Therefore,under this condition,the effects of Fe_(78)Si_(9)B_(13)^(AP)and zero-valent iron(ZVI)as PRB on the removal rate of total Cu in soil and the transformation of chemical forms of Cu are studied.Compared with ZVI,Fe_(78)Si_(9)B_(13)^(AP)as PRB has a better remediation effect.EK-Fe_(78)Si_(9)B_(13)^(AP)can remove 80.3%of total Cu in soil,and the biologically available Cu is reduced to 3.6%,which effectively reduces the environmental risk of contaminated soil.展开更多
The present study was designed to assess lead levels in playground soil and accumulated dust on playground equipment and then correlate those environmental lead measurements with children’s blood lead in the surround...The present study was designed to assess lead levels in playground soil and accumulated dust on playground equipment and then correlate those environmental lead measurements with children’s blood lead in the surrounding neighborhoods. Soil lead and surface dust were collected from 14 playgrounds in Muncie, Indiana, and blood lead levels were calculated for nearby children. Correlation analyses revealed a moderate positive association between dust Pb and soil Pb with a correlation coefficient r = 0.46 (p = 0.099). The relationship between settled dust on playground equipment and composite blood lead level also showed a medium positive correlation, indicated by r = 0.36 (p = 0.202). A positive correlation was also observed between soil Pb and composite blood lead values, as evidenced by r = 0.51 (p = 0.061). Furthermore, the assessment of spatial autocorrelation using Moran’s I index indicated no significant spatial clustering for the variables studied (dust Pb, soil Pb, and blood Pb). Correlation analysis showed a connection between lead levels in soil and dust, but no significant links were found between soil lead and blood lead and between dust lead and blood lead. These results suggest that environmental lead in parks has a limited impact on children’s blood lead levels nearby. Spatial autocorrelation analysis also revealed no significant spatial patterns among variables—dust, soil, and blood lead. Given these findings, it is recommended to seek expertise from qualified professionals and further perform comprehensive testing and analysis to investigate potential lead sources in children’s blood. The outcomes of this study offer valuable insights into assessing playground environmental lead contamination, contributing to future research priorities in this area. Specifically, future studies could focus on collecting larger sample sizes and characterizing blood lead in children who frequently use playgrounds rather than those who live nearby but may or may not use the playgrounds.展开更多
The purpose of this study was to investigate the pollution level of trace metals As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sb, Se and Zn in agricultural soil around the water reservoir. A total of 36 soil samples were colle...The purpose of this study was to investigate the pollution level of trace metals As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sb, Se and Zn in agricultural soil around the water reservoir. A total of 36 soil samples were collected both during off-season agriculture and pluvial agriculture from April to October 2022. The samples were analyzed for trace metals according to the standard methods of the US EPA 2007 with a microwave plasma atomic emission spectrometer (MP-AES), Agilent Model 4210. The pollution level was assessed using contamination factor (Cf) and modified contamination degree (mCd). During the off-season, the concentration of trace metals followed in descending order as Mn > Cr > Cu > Pb > Zn. As, Cd, Co, Hg, Ni, Sb and Se were below the detectable limits. In pluvial season, the concentration of traces of metal follows the order Mn > Cr > Zn > Cu > Ni > Pb > Hg > As. Cd, Co, Sb and Se remain below the detectable limits. The concentrations of Cr, Mn and Zn were lower in the off-season agriculture than in pluvial agriculture. For Cu and Pb, the concentrations were higher in the off-season than in pluvial agriculture. The Cf ranges from 0.24 to 11.70 depending on the considered trace metal. The Cf values of As, Ni, Pb, Zn and Mn indicated that the agricultural study soil was lowery contaminated by these trace metals. The agricultural study soil was moderately contaminated by Cr and Cu, and highly contaminated by Hg. Globally the agricultural study soil presents a moderate degree of contamination (mCd 2.25) by the eight trace metals studied. This result provides information on understanding the risks of trace metal contamination of agricultural soil. It is important to anticipate the control of soil contamination through regular monitoring of toxic metals in agricultural soils, control the quality of chemicals used in agriculture and regulate their use.展开更多
The long-term oil exploitation in oil fields has led to pollution of surrounding soil, creating a serious ecological problem. In order to promote and improve the application of microbial remediation in oil contaminate...The long-term oil exploitation in oil fields has led to pollution of surrounding soil, creating a serious ecological problem. In order to promote and improve the application of microbial remediation in oil contaminated soil, experiment is carried out in polluted area in Zhongyuan Oilfield. In the experiment, indigenous microorganisms and other physical and chemical methods are employed, ryegrass is grown, and environmental factors in soil are regulated to degrade the oil and treat the polluted soil. Results show that when the average oil content in the soil is about 523.08 mg/kg, 65 days' remediation through plants and microorganisms could help bring the oil content down to 74.61 mg/kg, achieving a degradation rate of 85.74%; through salinity treatment, salt content in soil is reduced by 62.93-82.03% to 399-823 mg/kg from previous 2.22 g/kg. Through this experiment, the bioremediation method is improved and its effectiveness and feasibility are testified. The result has been applied in Zhongyuan Oilfield and has brought fair ecological and economic benefits, providing technical support to the treatment of contaminated soil of the same kind, and offering some insights to the treatment of soil contaminated by other organic pollutants.展开更多
The present work deals with the development of an Ontology-Based Knowledge Network of soil/water physicochemical & biological properties (soil/water concepts), derived from ASTM Standard Methods (ASTMi,n) and rele...The present work deals with the development of an Ontology-Based Knowledge Network of soil/water physicochemical & biological properties (soil/water concepts), derived from ASTM Standard Methods (ASTMi,n) and relevant scientific/applicable references (published papers—PPi,n) to fill up/bridge the gap of the information science between cited Standards and infiltration discipline conceptual vocabulary providing accordingly a dedicated/internal Knowledge Base (KB). This attempt constitutes an innovative approach, since it is based on externalizing domain knowledge in the form of Ontology-Based Knowledge Networks, incorporating standardized methodology in soil engineering. The ontology soil/water concepts (semantics) of the developed network correspond to soil/water physicochemical & biological properties, classified in seven different generations that are distinguished/located in infiltration/percolation process of contaminated water through soil porous media. The interconnections with arcs between corresponding concepts/properties among the consecutive generations are defined by the relationship of dependent and independent variables. All these interconnections are documented according to the below three ways: 1) dependent and independent variables interconnected by using the logical operator “<em>depends on</em>” quoting existent explicit functions and equations;2) dependent and independent variables interconnected by using the logical operator “<em>depends on</em>” quoting produced implicit functions, according to Rayleigh’s method of indices;3) dependent and independent variables interconnected by using the logical operator “<em>related to</em>” based on a logical dependence among the examined nodes-concepts-variables. The aforementioned approach provides significant advantages to semantic web developers and web users by means of prompt knowledge navigation, tracking, retrieval and usage.展开更多
Fe-Si-B amorphous zero-valent iron has attracted wide attention because of its efficient remediation of heavy metals and dye wastewater.In this paper,the remediation effect of amorphous zero-valent iron powder(Fe78Si9...Fe-Si-B amorphous zero-valent iron has attracted wide attention because of its efficient remediation of heavy metals and dye wastewater.In this paper,the remediation effect of amorphous zero-valent iron powder(Fe78Si9-B13^(AP))on Ni contaminated soil was investigated.Results show that the immobilization efficiency of nickel in soil by Fe_(78)Si_(9)B_(13)^(AP)with low iron content is higher than that by ZVI.The apparent activation energies of the reactions of Fe_(78)Si_(9)B_(13)^(AP)with Ni^(2+)ions is 25.31 kJ/mol.After continuing the reaction for 7 days,Ni^(2+)ions is mainly transformed into monoplasmatic nickel(Ni0)and nickel combined with iron(hydroxide)oxides.Microstructure investigations show that the product layer with nano-pore structure is beneficial to improve the reaction activity of Fe_(78)Si_(9)B_(13)^(AP).After that,a magnetic separation process is introduced,in which part of the immobilized Ni are removed to reduce the total Ni content in soil by 58.21%.The results of simulated acid rain leaching experiment showed that the release of Ni in the soil after Fe_(78)Si_(9)B_(13)^(AP)remediation is 62.89%lower than that before remediation.展开更多
Heavy metal(loid)accumulation in agricultural soils is a threat to the soil capacity,quality,and productivity.It also increases human exposure to heavy metal(loid)s via consumption of contaminated plant-based foods.Th...Heavy metal(loid)accumulation in agricultural soils is a threat to the soil capacity,quality,and productivity.It also increases human exposure to heavy metal(loid)s via consumption of contaminated plant-based foods.The detrimental effects of soil contamination also deteriorate the environment of plants and animals.For sustainable agriculture,therefore,the soil must be protected from toxic levels of heavy metal(loid)s.Studies on heavy metal(loid)balances in agricultural soils are important in predicting future risks to sustainable production from agro-ecological zones and human exposure to heavy metal(loid)s.The latest and continuous indexing of the problem seems a prerequisite for sustainable agriculture.This review provides some background information and then summarizes key methodological approaches for studies on indexing and balance of heavy metal(loid)s in agricultural soils.In the end,important soil and health indices are explained that may be useful in understanding the extent of the problem.The provided information would contribute to sustainable heavy metal(loid)management in the agricultural soils,high crop production,better soil protection,and ultimately to human health.展开更多
Diesel contaminated soil(DCS) contained a large amount of the hydrocarbons and salt which was dominated by soluble sodium chloride. Aggregation process which made the desired aggregate size distribution could speed up...Diesel contaminated soil(DCS) contained a large amount of the hydrocarbons and salt which was dominated by soluble sodium chloride. Aggregation process which made the desired aggregate size distribution could speed up the degradation rate of the hydrocarbons since the aggregated DCS had better physical characteristics than the non-aggregated material. Artificial aggregation increased pores >30 μm by approximately 5% and reduced pores <1 μm by 5%, but did not change the percentage of the pores between 1 and 30 μm. The saturated hydraulic conductivity of non-aggregated DCS was 5×10-6 m · s-l, but it increased to 1×10-5 m · s-l after aggregation. The compression index of the non-aggregated DCS was 0.0186; however, the artificial aggregates with and without lime were 0.031 and 0.028, respectively. DCS could be piled 0.2 m deep without artificial aggregation; however, it could be applied 0.28 m deep when artificial aggregates were formed without limiting O2 transport.展开更多
Plant uptake of contaminants provides vital information for the reclamation of large area of contaminated soils.A field experiment was conducted using four plant species growing in four kinds of oil contaminated soils...Plant uptake of contaminants provides vital information for the reclamation of large area of contaminated soils.A field experiment was conducted using four plant species growing in four kinds of oil contaminated soils to estimate the uptake of organic and inorganic contaminants by plants from the oil contaminated soils.The experiment showed that the concentrations of some selected elements,such as B,Co and Ni in plants growing in the oil contaminated soils were significantly higher than those in plants growing in the uncontaminated control soil.The accumulation of metals in plants increased with plant biomass;however,the removal of metals by plants from the oil contaminated soils was not practical.展开更多
Several enzymes catalyze much of the processes that exist in the soil. Enzymes in polluted soils are usually less active due to their exposure to heavy metals. The main goal of this study was to see how bioavailable t...Several enzymes catalyze much of the processes that exist in the soil. Enzymes in polluted soils are usually less active due to their exposure to heavy metals. The main goal of this study was to see how bioavailable types of Cd affected the behavior of catalase, urease, and dehydrogenases, as well as to compare the findings from naturally and artificially polluted samples. An experiment was conducted on two types of farmland (garden) soil: natural soil and soil that had been chemically polluted with Cd. The total content of heavy metal graded these soils as very highly polluted with Cd. The experiment was repeated four times to test the effects of increasing concentration and days (time). Extracellular enzymes from farmland performed enzymatic activity tests that lasted 6 to 29 days after soil sampling. After 0, 5, 10, 20, 30, and 45 days of incubation, soil samples were taken for testing respectively. However, even though no nutrient was added, dehydrogenase and urease activity increased as Cd concentration increased from 0 to 5 mg/L as the days passed. This is a result of enzymes engaging in respiratory and other living activities because of the low cadmium concentration and respiratory soil properties. However, there were significant variations in enzyme activity between naturally polluted and artificially contaminated soils. Dehydrogenases, Urease, and Catalase all showed a common pattern of enzyme sensitivity, which could be ordered as Dehydrogenase > Urease > Catalase. Dehydrogenase enzyme activity has been discovered to be more Cd resistant.展开更多
The objective of this study was to assess the contribution of the spatial organization of cropping systems and the physicochemical properties of surface layers of the agricultural zones soils in tropical hydrosystems ...The objective of this study was to assess the contribution of the spatial organization of cropping systems and the physicochemical properties of surface layers of the agricultural zones soils in tropical hydrosystems to the spatial availability of nitrogen and pesticides during the wet season, such as the Béré watershed (BW) in C<span style="white-space:nowrap;">?</span>te d’Ivoire. For this purpose, after mapping the spatial distribution of the BW cropping systems based on the likelihood classification methodology of satellite images of the study area, 27 samples from the 0 - 20 cm horizon of the soil surface layers of the agricultural areas were taken during the wet and agricultural season of the year 2016. The Kjeldahl method has been used to evaluate the total nitrogen concentration and high-performance liquid chromatography (HPLC) chain made it possible for the analysis of pesticide residues in the soil solutions. Geostatistical analysis and processing of spatial data and physicochemical and agrochemical soil parameters revealed that two major agricultural areas stand out in the BW, namely the Béré upstream watershed (BUW) dominated at 32.65% by annual croppings (maize, cotton, rainfed or lowland rice, market gardening, etc.) and the Béré downstream watershed (BDW) by large areas of perennial croppings (cashew nuts, cocoa, etc.), <em>i.e.</em> 21.47%. Agricultural soils in BW are usually of the moderately desaturated ferralitic type with a low acid pH and a quite strong temperature, such as those of tropical soils’ characteristics. However, agricultural soils in the BUW are characterized by higher proportions of sand and coarse sand. The parameters such as total porosity, cation exchange capacity, clay, organic matter, silt, fine silt, coarse silt, and potassium ions, are higher in the soils of the agricultural area of the BDW. Moreover, soils in the agricultural areas of the BUW are less rich in total nitrogen (0.84 g<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>) in contrast to those of the BDW (1.2 g<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>). On the other hand, the median concentrations of total pesticides remain very high in the BUW (193.80 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>) in front of those of the BDW (94.81 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>). In addition, the biological family of herbicides was the most notable in BW. The chemical families of triazines (100% detection;79.37 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>) are the most important in the agricultural area of the BUW with the very significant presence of active molecules of pesticides such as simazine (92.86% detection;13.17 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>). However, in the BDW, urea substitute (100% detection;44.02 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>) dominate, including the active substance chlortoluron (84.62% detection;10.12 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>). The presence and abundance of nitrogen and pesticides in the soils of the agricultural areas of BW are strongly linked to the intensive use of these agrochemicals in cropping systems in recent decades in West African countries, even though most of the active molecules found are forbidden in several countries, especially in European countries. These are applied to tropical agricultural soils with physicochemical characteristics favorable to their retention in wet weather, as confirmed by the case of BW’s agricultural soils. Therefore, the BW’s water resources present worrying risks of contamination during rainy events that deserve to be assessed and monitored. Hence the need to take mitigating measures to this effect in order to preserve the quality of the environment.展开更多
Surface runoff from rainfall event is an important indicator of metal mobility in soil, which may enhance non-point source contamination of soil. This study is designed to assess the mobility of soil-bound lead throug...Surface runoff from rainfall event is an important indicator of metal mobility in soil, which may enhance non-point source contamination of soil. This study is designed to assess the mobility of soil-bound lead through simulated rainfall runoff experiment and its spatial distribution within the vicinity of a berm at a major military shooting range. Contamination was more significant at the impact area of berm, indicating threefold increase in Pb (17,500 ± 3811 μg/g) within a space of ten years. However, the non-impact area (459 ± 147 μg/g) was less contaminated. Other metals (Cu, Cd, Cr, Ni and Zn) analyzed were about background levels except for Cu at impact area. The enrichment ratio of Pb in runoff sediments was mostly high for the 0.43 mm sediment fractions independent of rainfall condition. Principal component analysis (PCA) biplot showed strong correlation between spatial distributions of metals around the vicinity of the berm (farmlands behind the berm) with concentrations on the impact berm soil. Surface runoff simulated on impact area soil had high concentrations of Pb (40.4 - 65.6 μg/mL) which could further lead to enrichment of soil-Pb levels within the vicinity of the berm. Decontamination measure is therefore required to minimize extensive contamination of surrounding soils of the impact berm due to rainfall runoff events.展开更多
Bioremediation involving bioaugmentation and biostimulation are eco-friendly existing methods for degrading polycyclic aromatic hydrocarbons (PAHs) in contaminated soils. This study investigates the efficiency of Pseu...Bioremediation involving bioaugmentation and biostimulation are eco-friendly existing methods for degrading polycyclic aromatic hydrocarbons (PAHs) in contaminated soils. This study investigates the efficiency of Pseudomonas auriginosa and nutrient-enriched sawdust (SD) in biodegrading ∑PAHs in contaminated soil (CS). Four compost mixtures of CS/SD (1:0, 3:1, 1:1, 1:3) were applied for 2, 4, 6, 8-week bio-cleanup after inoculation. Results show ∑PAHs concentrations decreased with increasing time of treatment for all four compost in experimental and control setups. The removal efficiency of ∑PAHs was clearly associated with nutrient-enriched sawdust and Pseudomonas auriginosa, especially for 3:1, 1:1, and 1:3 ratios. Both factors had a significant effect (p = 0.05) on removal efficiency compared to the control setup. The highest (78.5%) and lowest (37.8%) ∑PAHs removal efficiency were observed for CS/SD ratios of 1:3 and 1:0 respectively after 8-week treatment. In this instance, this study recommends a CS/SD ratio of 1:3 at 8-week treatment to achieve maximum removal efficiency of ∑PAHs in contaminated soils.展开更多
Recently, de la Torre[1] provided an approach for assessing the vulnerability of European soils for tetracyclines, fluoroquinolones and sulfamides contamination using a spatial risk assessment. It allowed identifying ...Recently, de la Torre[1] provided an approach for assessing the vulnerability of European soils for tetracyclines, fluoroquinolones and sulfamides contamination using a spatial risk assessment. It allowed identifying areas where vulnerable soil more occur, providing useful information for policies designed to reduce contamination. In the current study, this approach was applied to a local level, the autonomous region of Castile and León (C&L), located in the north-west part of Spain. High accurate and reliable source data were employed to generate a soil vulnerability map for tetracyclines in the study area, attempting to improve the release and consequence risk prediction. More specifically, pig density, temperature and soil use risk estimators were improved using data from national or local databases. Result comparison between the European and the present approach showed a good agreement demonstrating the utility of the European vulnerability map to be employed not only at global level but also for deciding how to allocate limited resources on national or subnational environmental surveillance programs of antibiotics. The model application at local level using more accurate data from national or local sources, afforded a better understanding of the spatial distribution of the risk, mainly associated with the higher accuracy of the national land use database SIOSE. It could offer a useful tool for local management of the risk, such as the management of animal manures fertilization on soil.展开更多
The effect of soil extraction procedures and/or sample pretreatment (drying, freezing of the soil sample) on the extractability of cadmium and lead was tested in a model experiment, with an employment of optical emiss...The effect of soil extraction procedures and/or sample pretreatment (drying, freezing of the soil sample) on the extractability of cadmium and lead was tested in a model experiment, with an employment of optical emission and atomic ab- sorption spectrometry methods. In the first part, 6 extraction procedures were compared: 2 mol l-1 HNO3, 0.43 mol l-1 CH3COOH, 0.05 mol l-1 EDTA, Mehlich III extraction procedure (0.2 mol l-1 CH3COOH + 0.25 mol l-1 NH4NO3 + 0.013 mol.l-1 HNO3 + 0.015 mol.l-1 NH4F + 0.001 mol.l-1 EDTA), 0.01 mol.l-1 CaCl2, and deionised water. Addi-tionally, two methods of soil solution sampling were compared, and the centrifugation of satu-rated soil and the use of suction cups and dif-ferential pulse anodic stripping voltametry was applied to assess free and complexed metals portions. The results showed that different soil sample extraction methods and/or sample pre-treatments including soil solution sampling can lead to different absolute values of mobile cadmium and lead content in soils. However, the interpretation of the data can lead to similar conclusions as are apparent from the compari- son of the soil solution sampling methods where fairly good correlation was observed (for Cd r = 0.76, and for Pb r = 0.74). The ambiguous results were reported for voltammetric determinations of free and complex portions of Cd and Pb where a different behavior was observed for water extracts of soil and soil solution obtained using suction cups. Moreover, a changing extent of lead complexation was determined with prolonged storage of the samples. The results confirmed that soil and/or soil solution sampling under immediate soil conditions and limitations of pre-extraction operations are necessary.展开更多
Disposal of domestic and industrial waste into the Odaw River and Korle Lagoon in Accra, Ghana, has led to pollution of the lagoon and surrounding soils. This study compared the elemental concentrations of heavy metal...Disposal of domestic and industrial waste into the Odaw River and Korle Lagoon in Accra, Ghana, has led to pollution of the lagoon and surrounding soils. This study compared the elemental concentrations of heavy metals (lead and zinc) and essential plant macronutrients (nitrogen, phosphorus and potassium) in soils from the Korle Lagoon Area to those in baseline soils from the University of Ghana Agricultural Farm (UG Farm), also in Accra. A comparative pot experiment, using maize (Zea mays L.) as test plant, was conducted to assess the effect of each soil type on plant growth. Soil samples from the Korle Lagoon Area were significantly higher (P < 0.001) in lead (Pb), zinc (Zn), nitrogen (N) and potassium (K) concentrations than samples from the UG Farm. Mean plant height and mean leaf width of maize plants harvested 7 weeks after planting (WAP) were both significantly higher (P < 0.003) for samples from the Korle Lagoon Area soil compared to those from the UG Farm soil. Higher accumulation of Zn (448.3 ± 45.5) in maize shoot within 3 weeks of planting in the Korle Lagoon Area soil had phytotoxic effects on growth, resulting in shoot growth inhibition and reduced uptake of P and K in 11-week-old plants. The findings indicate that though nutrient enrichment due to sewage disposal into the lagoon may increase crop production, the nutritional quality of the crop produced could be compromised by heavy metal accumulation in the soil and subsequent uptake by the plant.展开更多
Persulfate is considered a convenient and efficient remediation agent for organic contaminated soil.However,the potential risk of sulfur into the soil remediation by persulfate remains ignored.In this study,glass bott...Persulfate is considered a convenient and efficient remediation agent for organic contaminated soil.However,the potential risk of sulfur into the soil remediation by persulfate remains ignored.In this study,glass bottles with different persulfate dosages and groundwater tables were set up to simulate persulfate remediation of organic pollutants(aniline).The results found sulfate to be the main end-product(83.0%–99.5%)of persulfate remediation after10 days.Moreover,H_(2)S accounted for 93.4%–99.4%of sulfur reduction end-products,suggesting that H_(2)S was the final fate of sulfur.H_(2)S was released rapidly after one to three days at a maximum concentration of 33.0 ppm,which is sufficient to make a person uncomfortable.According to the fitted curve results,H_(2)S concentration decreased to a safe concentration(0.15 ppm)after 20–85 days.Meanwhile,the maximum concentration of methanethiol reached 0.6 ppm.These results indicated that secondary pollution from persulfate remediation could release harmful gases over a long time.Therefore,persulfate should be used more carefully as a remediation agent for soil contamination.展开更多
High energy consumption is a serious issue associated with in situ thermal desorption(TD)remediation of sites contaminated by petroleum hydrocarbons(PHs).The knowledge on the thermophysical properties of contaminated ...High energy consumption is a serious issue associated with in situ thermal desorption(TD)remediation of sites contaminated by petroleum hydrocarbons(PHs).The knowledge on the thermophysical properties of contaminated soil can help predict accurately the transient temperature distribution in a remediation site,for the purpose of energy conservation.However,such data are rarely reported for PH-contaminated soil.In this study,by taking diesel as a representative example for PHs,soil samples with constant dry bulk density but different diesel mass concentrations ranging from 0% to 20% were prepared,and the variations of their thermal conductivity,specific heat capacity and thermal diffusivity were measured and analyzed over a wide temperature range between 0℃ and 120℃.It was found that the effect of diesel concentration on the thermal conductivity of soil is negligible when it is below 1%.When diesel concentration is below 10%,the thermal conductivity of soil increases with raising the temperature.However,when diesel concentration becomes above 10%,the change of the thermal conductivity of soil with temperature exhibits the opposite trend.This is mainly due to the competition between soil minerals and diesel,because the thermal conductivity of minerals increases with temperature,whereas the thermal conductivity of diesel decreases with temperature.The analysis results showed that,compared with temperature,the diesel concentration has more significant effects on soil thermal conductivity.Regardless of the diesel concentration,with the increase of temperature,the specific heat capacity of soil increases,while the thermal diffusivity of soil decreases.In addition,the results of a control experiment exhibited that the relative differences of the thermal conductivity of the soil samples containing the same concentration of both diesel and a pure alkane are all below 10%,indicating that the results obtained with diesel in this study can be extended to the family of PHs.A theoretical prediction model was proposed based on cubic fractal and thermal resistance analysis,which confirmed that diesel concentration does have a significant effect on soil thermal conductivity.For the sake of practical applications,a regression model with the diesel concentration as a primary parameter was also proposed.展开更多
基金This research was funded by the National Natural Science Foundation of China(NSFC)[Grant Nos.51661015 and 52061024]the University Innovation Fund Project of Gansu Provincial Department of Education[Grant No.2021B-553]the Natural Science Foundation of Zhejiang Province,China(4304030).
文摘Iron-based amorphous crystalline powder Fe_(78)Si_(9)B_(13)^(AP)is used as a permeability reaction barrier(PRB)combined with an electrokinetic method(EK-PRB)to study the removal rate of Cu in contaminated soil.After treating Cucontaminated soil for 5 days under different voltage gradients and soil water content,the soil pH is between 3.1 and 7.2.The increase of voltage gradient and soil water content can effectively promote the movement of Cu^(2+) to the cathode.The voltage gradient is 3 V/cm,and the water content of 40%is considered to be an optional experimental condition.Therefore,under this condition,the effects of Fe_(78)Si_(9)B_(13)^(AP)and zero-valent iron(ZVI)as PRB on the removal rate of total Cu in soil and the transformation of chemical forms of Cu are studied.Compared with ZVI,Fe_(78)Si_(9)B_(13)^(AP)as PRB has a better remediation effect.EK-Fe_(78)Si_(9)B_(13)^(AP)can remove 80.3%of total Cu in soil,and the biologically available Cu is reduced to 3.6%,which effectively reduces the environmental risk of contaminated soil.
文摘The present study was designed to assess lead levels in playground soil and accumulated dust on playground equipment and then correlate those environmental lead measurements with children’s blood lead in the surrounding neighborhoods. Soil lead and surface dust were collected from 14 playgrounds in Muncie, Indiana, and blood lead levels were calculated for nearby children. Correlation analyses revealed a moderate positive association between dust Pb and soil Pb with a correlation coefficient r = 0.46 (p = 0.099). The relationship between settled dust on playground equipment and composite blood lead level also showed a medium positive correlation, indicated by r = 0.36 (p = 0.202). A positive correlation was also observed between soil Pb and composite blood lead values, as evidenced by r = 0.51 (p = 0.061). Furthermore, the assessment of spatial autocorrelation using Moran’s I index indicated no significant spatial clustering for the variables studied (dust Pb, soil Pb, and blood Pb). Correlation analysis showed a connection between lead levels in soil and dust, but no significant links were found between soil lead and blood lead and between dust lead and blood lead. These results suggest that environmental lead in parks has a limited impact on children’s blood lead levels nearby. Spatial autocorrelation analysis also revealed no significant spatial patterns among variables—dust, soil, and blood lead. Given these findings, it is recommended to seek expertise from qualified professionals and further perform comprehensive testing and analysis to investigate potential lead sources in children’s blood. The outcomes of this study offer valuable insights into assessing playground environmental lead contamination, contributing to future research priorities in this area. Specifically, future studies could focus on collecting larger sample sizes and characterizing blood lead in children who frequently use playgrounds rather than those who live nearby but may or may not use the playgrounds.
文摘The purpose of this study was to investigate the pollution level of trace metals As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sb, Se and Zn in agricultural soil around the water reservoir. A total of 36 soil samples were collected both during off-season agriculture and pluvial agriculture from April to October 2022. The samples were analyzed for trace metals according to the standard methods of the US EPA 2007 with a microwave plasma atomic emission spectrometer (MP-AES), Agilent Model 4210. The pollution level was assessed using contamination factor (Cf) and modified contamination degree (mCd). During the off-season, the concentration of trace metals followed in descending order as Mn > Cr > Cu > Pb > Zn. As, Cd, Co, Hg, Ni, Sb and Se were below the detectable limits. In pluvial season, the concentration of traces of metal follows the order Mn > Cr > Zn > Cu > Ni > Pb > Hg > As. Cd, Co, Sb and Se remain below the detectable limits. The concentrations of Cr, Mn and Zn were lower in the off-season agriculture than in pluvial agriculture. For Cu and Pb, the concentrations were higher in the off-season than in pluvial agriculture. The Cf ranges from 0.24 to 11.70 depending on the considered trace metal. The Cf values of As, Ni, Pb, Zn and Mn indicated that the agricultural study soil was lowery contaminated by these trace metals. The agricultural study soil was moderately contaminated by Cr and Cu, and highly contaminated by Hg. Globally the agricultural study soil presents a moderate degree of contamination (mCd 2.25) by the eight trace metals studied. This result provides information on understanding the risks of trace metal contamination of agricultural soil. It is important to anticipate the control of soil contamination through regular monitoring of toxic metals in agricultural soils, control the quality of chemicals used in agriculture and regulate their use.
基金funded by The basic scientific research project fund of Chinese Academy of Geological Sciences (Code: YYWF201519)China Geology Survey Work Program (Code: 121201106000150006)+1 种基金The international cooperation project of Ministry of Science and Technology (Code: 2005DFA90200)Mine environment management project of Henan Provincial Department of Land and Resources
文摘The long-term oil exploitation in oil fields has led to pollution of surrounding soil, creating a serious ecological problem. In order to promote and improve the application of microbial remediation in oil contaminated soil, experiment is carried out in polluted area in Zhongyuan Oilfield. In the experiment, indigenous microorganisms and other physical and chemical methods are employed, ryegrass is grown, and environmental factors in soil are regulated to degrade the oil and treat the polluted soil. Results show that when the average oil content in the soil is about 523.08 mg/kg, 65 days' remediation through plants and microorganisms could help bring the oil content down to 74.61 mg/kg, achieving a degradation rate of 85.74%; through salinity treatment, salt content in soil is reduced by 62.93-82.03% to 399-823 mg/kg from previous 2.22 g/kg. Through this experiment, the bioremediation method is improved and its effectiveness and feasibility are testified. The result has been applied in Zhongyuan Oilfield and has brought fair ecological and economic benefits, providing technical support to the treatment of contaminated soil of the same kind, and offering some insights to the treatment of soil contaminated by other organic pollutants.
文摘The present work deals with the development of an Ontology-Based Knowledge Network of soil/water physicochemical & biological properties (soil/water concepts), derived from ASTM Standard Methods (ASTMi,n) and relevant scientific/applicable references (published papers—PPi,n) to fill up/bridge the gap of the information science between cited Standards and infiltration discipline conceptual vocabulary providing accordingly a dedicated/internal Knowledge Base (KB). This attempt constitutes an innovative approach, since it is based on externalizing domain knowledge in the form of Ontology-Based Knowledge Networks, incorporating standardized methodology in soil engineering. The ontology soil/water concepts (semantics) of the developed network correspond to soil/water physicochemical & biological properties, classified in seven different generations that are distinguished/located in infiltration/percolation process of contaminated water through soil porous media. The interconnections with arcs between corresponding concepts/properties among the consecutive generations are defined by the relationship of dependent and independent variables. All these interconnections are documented according to the below three ways: 1) dependent and independent variables interconnected by using the logical operator “<em>depends on</em>” quoting existent explicit functions and equations;2) dependent and independent variables interconnected by using the logical operator “<em>depends on</em>” quoting produced implicit functions, according to Rayleigh’s method of indices;3) dependent and independent variables interconnected by using the logical operator “<em>related to</em>” based on a logical dependence among the examined nodes-concepts-variables. The aforementioned approach provides significant advantages to semantic web developers and web users by means of prompt knowledge navigation, tracking, retrieval and usage.
基金This research was funded by the National Natural Science Foundation of China(NSFC)[Grant Nos.51661015 and 52061024]the Natural Science Foundation of Zhejiang Province[Grant No.LQ20E010002]。
文摘Fe-Si-B amorphous zero-valent iron has attracted wide attention because of its efficient remediation of heavy metals and dye wastewater.In this paper,the remediation effect of amorphous zero-valent iron powder(Fe78Si9-B13^(AP))on Ni contaminated soil was investigated.Results show that the immobilization efficiency of nickel in soil by Fe_(78)Si_(9)B_(13)^(AP)with low iron content is higher than that by ZVI.The apparent activation energies of the reactions of Fe_(78)Si_(9)B_(13)^(AP)with Ni^(2+)ions is 25.31 kJ/mol.After continuing the reaction for 7 days,Ni^(2+)ions is mainly transformed into monoplasmatic nickel(Ni0)and nickel combined with iron(hydroxide)oxides.Microstructure investigations show that the product layer with nano-pore structure is beneficial to improve the reaction activity of Fe_(78)Si_(9)B_(13)^(AP).After that,a magnetic separation process is introduced,in which part of the immobilized Ni are removed to reduce the total Ni content in soil by 58.21%.The results of simulated acid rain leaching experiment showed that the release of Ni in the soil after Fe_(78)Si_(9)B_(13)^(AP)remediation is 62.89%lower than that before remediation.
基金support from the Higher Education Commission,Islamabad(Pakistan)to conduct related research experiments in Pakistan。
文摘Heavy metal(loid)accumulation in agricultural soils is a threat to the soil capacity,quality,and productivity.It also increases human exposure to heavy metal(loid)s via consumption of contaminated plant-based foods.The detrimental effects of soil contamination also deteriorate the environment of plants and animals.For sustainable agriculture,therefore,the soil must be protected from toxic levels of heavy metal(loid)s.Studies on heavy metal(loid)balances in agricultural soils are important in predicting future risks to sustainable production from agro-ecological zones and human exposure to heavy metal(loid)s.The latest and continuous indexing of the problem seems a prerequisite for sustainable agriculture.This review provides some background information and then summarizes key methodological approaches for studies on indexing and balance of heavy metal(loid)s in agricultural soils.In the end,important soil and health indices are explained that may be useful in understanding the extent of the problem.The provided information would contribute to sustainable heavy metal(loid)management in the agricultural soils,high crop production,better soil protection,and ultimately to human health.
文摘Diesel contaminated soil(DCS) contained a large amount of the hydrocarbons and salt which was dominated by soluble sodium chloride. Aggregation process which made the desired aggregate size distribution could speed up the degradation rate of the hydrocarbons since the aggregated DCS had better physical characteristics than the non-aggregated material. Artificial aggregation increased pores >30 μm by approximately 5% and reduced pores <1 μm by 5%, but did not change the percentage of the pores between 1 and 30 μm. The saturated hydraulic conductivity of non-aggregated DCS was 5×10-6 m · s-l, but it increased to 1×10-5 m · s-l after aggregation. The compression index of the non-aggregated DCS was 0.0186; however, the artificial aggregates with and without lime were 0.031 and 0.028, respectively. DCS could be piled 0.2 m deep without artificial aggregation; however, it could be applied 0.28 m deep when artificial aggregates were formed without limiting O2 transport.
文摘Plant uptake of contaminants provides vital information for the reclamation of large area of contaminated soils.A field experiment was conducted using four plant species growing in four kinds of oil contaminated soils to estimate the uptake of organic and inorganic contaminants by plants from the oil contaminated soils.The experiment showed that the concentrations of some selected elements,such as B,Co and Ni in plants growing in the oil contaminated soils were significantly higher than those in plants growing in the uncontaminated control soil.The accumulation of metals in plants increased with plant biomass;however,the removal of metals by plants from the oil contaminated soils was not practical.
文摘Several enzymes catalyze much of the processes that exist in the soil. Enzymes in polluted soils are usually less active due to their exposure to heavy metals. The main goal of this study was to see how bioavailable types of Cd affected the behavior of catalase, urease, and dehydrogenases, as well as to compare the findings from naturally and artificially polluted samples. An experiment was conducted on two types of farmland (garden) soil: natural soil and soil that had been chemically polluted with Cd. The total content of heavy metal graded these soils as very highly polluted with Cd. The experiment was repeated four times to test the effects of increasing concentration and days (time). Extracellular enzymes from farmland performed enzymatic activity tests that lasted 6 to 29 days after soil sampling. After 0, 5, 10, 20, 30, and 45 days of incubation, soil samples were taken for testing respectively. However, even though no nutrient was added, dehydrogenase and urease activity increased as Cd concentration increased from 0 to 5 mg/L as the days passed. This is a result of enzymes engaging in respiratory and other living activities because of the low cadmium concentration and respiratory soil properties. However, there were significant variations in enzyme activity between naturally polluted and artificially contaminated soils. Dehydrogenases, Urease, and Catalase all showed a common pattern of enzyme sensitivity, which could be ordered as Dehydrogenase > Urease > Catalase. Dehydrogenase enzyme activity has been discovered to be more Cd resistant.
文摘The objective of this study was to assess the contribution of the spatial organization of cropping systems and the physicochemical properties of surface layers of the agricultural zones soils in tropical hydrosystems to the spatial availability of nitrogen and pesticides during the wet season, such as the Béré watershed (BW) in C<span style="white-space:nowrap;">?</span>te d’Ivoire. For this purpose, after mapping the spatial distribution of the BW cropping systems based on the likelihood classification methodology of satellite images of the study area, 27 samples from the 0 - 20 cm horizon of the soil surface layers of the agricultural areas were taken during the wet and agricultural season of the year 2016. The Kjeldahl method has been used to evaluate the total nitrogen concentration and high-performance liquid chromatography (HPLC) chain made it possible for the analysis of pesticide residues in the soil solutions. Geostatistical analysis and processing of spatial data and physicochemical and agrochemical soil parameters revealed that two major agricultural areas stand out in the BW, namely the Béré upstream watershed (BUW) dominated at 32.65% by annual croppings (maize, cotton, rainfed or lowland rice, market gardening, etc.) and the Béré downstream watershed (BDW) by large areas of perennial croppings (cashew nuts, cocoa, etc.), <em>i.e.</em> 21.47%. Agricultural soils in BW are usually of the moderately desaturated ferralitic type with a low acid pH and a quite strong temperature, such as those of tropical soils’ characteristics. However, agricultural soils in the BUW are characterized by higher proportions of sand and coarse sand. The parameters such as total porosity, cation exchange capacity, clay, organic matter, silt, fine silt, coarse silt, and potassium ions, are higher in the soils of the agricultural area of the BDW. Moreover, soils in the agricultural areas of the BUW are less rich in total nitrogen (0.84 g<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>) in contrast to those of the BDW (1.2 g<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>). On the other hand, the median concentrations of total pesticides remain very high in the BUW (193.80 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>) in front of those of the BDW (94.81 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>). In addition, the biological family of herbicides was the most notable in BW. The chemical families of triazines (100% detection;79.37 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>) are the most important in the agricultural area of the BUW with the very significant presence of active molecules of pesticides such as simazine (92.86% detection;13.17 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>). However, in the BDW, urea substitute (100% detection;44.02 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>) dominate, including the active substance chlortoluron (84.62% detection;10.12 μg<span style="white-space:nowrap;">·</span>kg<sup>-1</sup>). The presence and abundance of nitrogen and pesticides in the soils of the agricultural areas of BW are strongly linked to the intensive use of these agrochemicals in cropping systems in recent decades in West African countries, even though most of the active molecules found are forbidden in several countries, especially in European countries. These are applied to tropical agricultural soils with physicochemical characteristics favorable to their retention in wet weather, as confirmed by the case of BW’s agricultural soils. Therefore, the BW’s water resources present worrying risks of contamination during rainy events that deserve to be assessed and monitored. Hence the need to take mitigating measures to this effect in order to preserve the quality of the environment.
文摘Surface runoff from rainfall event is an important indicator of metal mobility in soil, which may enhance non-point source contamination of soil. This study is designed to assess the mobility of soil-bound lead through simulated rainfall runoff experiment and its spatial distribution within the vicinity of a berm at a major military shooting range. Contamination was more significant at the impact area of berm, indicating threefold increase in Pb (17,500 ± 3811 μg/g) within a space of ten years. However, the non-impact area (459 ± 147 μg/g) was less contaminated. Other metals (Cu, Cd, Cr, Ni and Zn) analyzed were about background levels except for Cu at impact area. The enrichment ratio of Pb in runoff sediments was mostly high for the 0.43 mm sediment fractions independent of rainfall condition. Principal component analysis (PCA) biplot showed strong correlation between spatial distributions of metals around the vicinity of the berm (farmlands behind the berm) with concentrations on the impact berm soil. Surface runoff simulated on impact area soil had high concentrations of Pb (40.4 - 65.6 μg/mL) which could further lead to enrichment of soil-Pb levels within the vicinity of the berm. Decontamination measure is therefore required to minimize extensive contamination of surrounding soils of the impact berm due to rainfall runoff events.
文摘Bioremediation involving bioaugmentation and biostimulation are eco-friendly existing methods for degrading polycyclic aromatic hydrocarbons (PAHs) in contaminated soils. This study investigates the efficiency of Pseudomonas auriginosa and nutrient-enriched sawdust (SD) in biodegrading ∑PAHs in contaminated soil (CS). Four compost mixtures of CS/SD (1:0, 3:1, 1:1, 1:3) were applied for 2, 4, 6, 8-week bio-cleanup after inoculation. Results show ∑PAHs concentrations decreased with increasing time of treatment for all four compost in experimental and control setups. The removal efficiency of ∑PAHs was clearly associated with nutrient-enriched sawdust and Pseudomonas auriginosa, especially for 3:1, 1:1, and 1:3 ratios. Both factors had a significant effect (p = 0.05) on removal efficiency compared to the control setup. The highest (78.5%) and lowest (37.8%) ∑PAHs removal efficiency were observed for CS/SD ratios of 1:3 and 1:0 respectively after 8-week treatment. In this instance, this study recommends a CS/SD ratio of 1:3 at 8-week treatment to achieve maximum removal efficiency of ∑PAHs in contaminated soils.
基金financially supported by the projects RTA2010-00066-CO2-01 and S2009-AGR-1489.
文摘Recently, de la Torre[1] provided an approach for assessing the vulnerability of European soils for tetracyclines, fluoroquinolones and sulfamides contamination using a spatial risk assessment. It allowed identifying areas where vulnerable soil more occur, providing useful information for policies designed to reduce contamination. In the current study, this approach was applied to a local level, the autonomous region of Castile and León (C&L), located in the north-west part of Spain. High accurate and reliable source data were employed to generate a soil vulnerability map for tetracyclines in the study area, attempting to improve the release and consequence risk prediction. More specifically, pig density, temperature and soil use risk estimators were improved using data from national or local databases. Result comparison between the European and the present approach showed a good agreement demonstrating the utility of the European vulnerability map to be employed not only at global level but also for deciding how to allocate limited resources on national or subnational environmental surveillance programs of antibiotics. The model application at local level using more accurate data from national or local sources, afforded a better understanding of the spatial distribution of the risk, mainly associated with the higher accuracy of the national land use database SIOSE. It could offer a useful tool for local management of the risk, such as the management of animal manures fertilization on soil.
基金The authors wish to thank the Czech Ministry of Agriculture and the Ministry of Education,Youth,and Sports for their financial support of the project MSM 6046070901Ministry of Agriculture,Czech Republic for their financial support of the NAZV project No.QH81167and the GAAVCR for their financial support of the project No.IAA400400806.
文摘The effect of soil extraction procedures and/or sample pretreatment (drying, freezing of the soil sample) on the extractability of cadmium and lead was tested in a model experiment, with an employment of optical emission and atomic ab- sorption spectrometry methods. In the first part, 6 extraction procedures were compared: 2 mol l-1 HNO3, 0.43 mol l-1 CH3COOH, 0.05 mol l-1 EDTA, Mehlich III extraction procedure (0.2 mol l-1 CH3COOH + 0.25 mol l-1 NH4NO3 + 0.013 mol.l-1 HNO3 + 0.015 mol.l-1 NH4F + 0.001 mol.l-1 EDTA), 0.01 mol.l-1 CaCl2, and deionised water. Addi-tionally, two methods of soil solution sampling were compared, and the centrifugation of satu-rated soil and the use of suction cups and dif-ferential pulse anodic stripping voltametry was applied to assess free and complexed metals portions. The results showed that different soil sample extraction methods and/or sample pre-treatments including soil solution sampling can lead to different absolute values of mobile cadmium and lead content in soils. However, the interpretation of the data can lead to similar conclusions as are apparent from the compari- son of the soil solution sampling methods where fairly good correlation was observed (for Cd r = 0.76, and for Pb r = 0.74). The ambiguous results were reported for voltammetric determinations of free and complex portions of Cd and Pb where a different behavior was observed for water extracts of soil and soil solution obtained using suction cups. Moreover, a changing extent of lead complexation was determined with prolonged storage of the samples. The results confirmed that soil and/or soil solution sampling under immediate soil conditions and limitations of pre-extraction operations are necessary.
文摘Disposal of domestic and industrial waste into the Odaw River and Korle Lagoon in Accra, Ghana, has led to pollution of the lagoon and surrounding soils. This study compared the elemental concentrations of heavy metals (lead and zinc) and essential plant macronutrients (nitrogen, phosphorus and potassium) in soils from the Korle Lagoon Area to those in baseline soils from the University of Ghana Agricultural Farm (UG Farm), also in Accra. A comparative pot experiment, using maize (Zea mays L.) as test plant, was conducted to assess the effect of each soil type on plant growth. Soil samples from the Korle Lagoon Area were significantly higher (P < 0.001) in lead (Pb), zinc (Zn), nitrogen (N) and potassium (K) concentrations than samples from the UG Farm. Mean plant height and mean leaf width of maize plants harvested 7 weeks after planting (WAP) were both significantly higher (P < 0.003) for samples from the Korle Lagoon Area soil compared to those from the UG Farm soil. Higher accumulation of Zn (448.3 ± 45.5) in maize shoot within 3 weeks of planting in the Korle Lagoon Area soil had phytotoxic effects on growth, resulting in shoot growth inhibition and reduced uptake of P and K in 11-week-old plants. The findings indicate that though nutrient enrichment due to sewage disposal into the lagoon may increase crop production, the nutritional quality of the crop produced could be compromised by heavy metal accumulation in the soil and subsequent uptake by the plant.
基金supported by the National Key R&D Program of China (No.2018YFC1800506)the Key R&D Program of Zhejiang Province (No.2020C03083)。
文摘Persulfate is considered a convenient and efficient remediation agent for organic contaminated soil.However,the potential risk of sulfur into the soil remediation by persulfate remains ignored.In this study,glass bottles with different persulfate dosages and groundwater tables were set up to simulate persulfate remediation of organic pollutants(aniline).The results found sulfate to be the main end-product(83.0%–99.5%)of persulfate remediation after10 days.Moreover,H_(2)S accounted for 93.4%–99.4%of sulfur reduction end-products,suggesting that H_(2)S was the final fate of sulfur.H_(2)S was released rapidly after one to three days at a maximum concentration of 33.0 ppm,which is sufficient to make a person uncomfortable.According to the fitted curve results,H_(2)S concentration decreased to a safe concentration(0.15 ppm)after 20–85 days.Meanwhile,the maximum concentration of methanethiol reached 0.6 ppm.These results indicated that secondary pollution from persulfate remediation could release harmful gases over a long time.Therefore,persulfate should be used more carefully as a remediation agent for soil contamination.
基金financially supported by the National Key Research and Development Program (project No.2019YFC1805700,program No.2019YFC1805701)。
文摘High energy consumption is a serious issue associated with in situ thermal desorption(TD)remediation of sites contaminated by petroleum hydrocarbons(PHs).The knowledge on the thermophysical properties of contaminated soil can help predict accurately the transient temperature distribution in a remediation site,for the purpose of energy conservation.However,such data are rarely reported for PH-contaminated soil.In this study,by taking diesel as a representative example for PHs,soil samples with constant dry bulk density but different diesel mass concentrations ranging from 0% to 20% were prepared,and the variations of their thermal conductivity,specific heat capacity and thermal diffusivity were measured and analyzed over a wide temperature range between 0℃ and 120℃.It was found that the effect of diesel concentration on the thermal conductivity of soil is negligible when it is below 1%.When diesel concentration is below 10%,the thermal conductivity of soil increases with raising the temperature.However,when diesel concentration becomes above 10%,the change of the thermal conductivity of soil with temperature exhibits the opposite trend.This is mainly due to the competition between soil minerals and diesel,because the thermal conductivity of minerals increases with temperature,whereas the thermal conductivity of diesel decreases with temperature.The analysis results showed that,compared with temperature,the diesel concentration has more significant effects on soil thermal conductivity.Regardless of the diesel concentration,with the increase of temperature,the specific heat capacity of soil increases,while the thermal diffusivity of soil decreases.In addition,the results of a control experiment exhibited that the relative differences of the thermal conductivity of the soil samples containing the same concentration of both diesel and a pure alkane are all below 10%,indicating that the results obtained with diesel in this study can be extended to the family of PHs.A theoretical prediction model was proposed based on cubic fractal and thermal resistance analysis,which confirmed that diesel concentration does have a significant effect on soil thermal conductivity.For the sake of practical applications,a regression model with the diesel concentration as a primary parameter was also proposed.
