The knowledge about the population dynamics of freshwater snail intermediate host and their roles in disease transmission is little known in Bayelsa State. This study investigated the species composition of fresh wate...The knowledge about the population dynamics of freshwater snail intermediate host and their roles in disease transmission is little known in Bayelsa State. This study investigated the species composition of fresh water snail intermediate host in Amassoma community and the Niger Delta University Campuses during August 2019-October 2019 across five locations (Main campus Hostel, E.T.F Building, Ogboebi-Ama, Efeke-Ama, Ogbopina). Snails were collected from the water bodies with the aid of a scooping net and hand picking. The morphological identification of the snail intermediate host followed standard procedures. From the result, five hundred and seventy-one freshwater snails belonging to four genera and five species were recorded. The presence of <em>Lymnae</em> and <em>Bulinus</em> in the locations highlights foci for fascioliasis and schistosomiasis. The presence of <em>Melanoides</em> spp. is novel in Bayelsa State. The public health implications of these snails have called for timely control intervention.展开更多
Alterations in blood variables of Sarotherodon melanotheron transmitted immediately from brackish water(salinity 13.71‰)to fresh water(salinity 0.12‰)were examined to evaluate the consequence of abrupt alterations i...Alterations in blood variables of Sarotherodon melanotheron transmitted immediately from brackish water(salinity 13.71‰)to fresh water(salinity 0.12‰)were examined to evaluate the consequence of abrupt alterations in the environment on fish blood parameters.The results acquired revealed that significant reduction(p<0.05)in mean values of Haemoglobin(Hb)from 7.37±1.22 to 4.30±0.82dl-1;Packed Cell Volume(PCV)23.48±3.22 to 15.08±2.97%;Red Blood Cell(RBC)5.99±0.72 to 3.31±0.77 Cells x106;Mean Corpuscular Haemoglobin Concentration(MCHC)31.68±3.66 to 28.48±2.03 pg;and Platelets(PLT)195.44±16.77 to 138.99±9.05103 uL-1.However,notable elevation was recorded in the values of Erythrocyte Sedimentation Rate(ESR)from 4.89±0.16 to 10.58±1.48 mm/hr;White Blood Cell(WBC)27.03±2.96 to 33.09±3.72 x 109 L-1;Mean Corpuscular Volume(MCV)39.33±3.07 to 45.88±7.03 fL Neutrophils(NEUT)41.71±3.08 to 48.30±7.99%;Lymphocytes(LYMP)54.60±3.99 to 46.36±9.87%and Monocytes(MON)3.80±1.04 to 5.97±1.99%.These variations in the blood parameters were more perceptible in adult than juvenile fish.Results from this study consequently imply that direct transfer of fish to a region of lower salinity may have damaging effect on the physiology of S.melanotheron as observed in this study.展开更多
The process of air-sea fresh water exchange is included successfully in the Global-Ocean-Atmosphere-Land-System model developed at the State Key Laboratory of Atmospheric Sciences andGeophysical Fluid Dynamics (LASG)....The process of air-sea fresh water exchange is included successfully in the Global-Ocean-Atmosphere-Land-System model developed at the State Key Laboratory of Atmospheric Sciences andGeophysical Fluid Dynamics (LASG). The results of the coupled integration show that the cIimate drift hasbeell controlled successfully. Analyses on the responses of ocean circulation to the changes of surface freshwater or salinity forcing show that the ocean spin-up stage under flux condition for salinity is the key to theimplementation of air-sea fresh water flux coupling. This study also demonstrates that theModified-Monthly-Flux-AnomaIy coupling scheme (MMFA) brought forward by Yu and Zhang (1998)is suitable not only for daily air-sea heat flux coupling but also for daily fresh water flux coupling.展开更多
Using field hydrological data, the relationship between the mixing of salt water and fresh water and the tidal range/ high tidal level in the Changjiang (Yangtze) River estuary is discussed, and the transporting and c...Using field hydrological data, the relationship between the mixing of salt water and fresh water and the tidal range/ high tidal level in the Changjiang (Yangtze) River estuary is discussed, and the transporting and concentrating of suspended sediment in the estuary were also analysed in respect to the circulation, flocculation and stratified interface resulting from mixing.The calculation results by two-dimentional box model have confirmed the effects of the circulation on the concentrating of suspended sediment in the estuary. The conclusions derived from this work have deepened the understanding on the mixing in the Changjiang River estuary and are of significance in bo’th theory and practice.展开更多
Wireless communications from air to fresh water are studied here. Our analysis relies on plane wave propagation mod-els. Specifically, the transmission loss and propagation loss of RF waves penetrating into fresh wate...Wireless communications from air to fresh water are studied here. Our analysis relies on plane wave propagation mod-els. Specifically, the transmission loss and propagation loss of RF waves penetrating into fresh water are calculated for various propagation depths. Even though RF wireless communications are not well suited for seawater due to its high attenuation, our paper illustrates that RF communications from air to fresh water are possible. Finally, this work de-rives the optimum frequencies, which provide minimum attenuation and maximum propagation depth, for RF commu-nications from air to fresh water.展开更多
From the point of view of urban consumption behavior, urban fresh water consumption could be classified as three types, namely, direct, indirect and induced water consumption. A calculation approach of urban fresh wat...From the point of view of urban consumption behavior, urban fresh water consumption could be classified as three types, namely, direct, indirect and induced water consumption. A calculation approach of urban fresh water consumption was presented based on the theory of urban basic material consumption and the input-output method, which was utilized to calculate urban fresh water consumption of China, and to analyze its structural change and causes. The results show that the total urban fresh water consumption increased 561.7×109m3, and the proportion to the total national fresh water resources increased by 20 percentage points from 1952 to 2005. The proportion of direct and induced water consumption had been continuously rising, and it increased by 15 and 35 percentage points separately from 1952 to 2005, while the proportion of indirect water consumption decreased by 50 percentage points. Urban indirect water consumption was mainly related to urban grain, beef and mutton consumption, and urban induced water consumption had a close relationship with the amount of carbon emission per capita. Finally, some countermeasures were put forward to realize sustainable utilization of urban fresh water resources in China.展开更多
The development of urbanization has a close relationship with fresh water resources, especially in the rapid urbanization period. By analyzing the course of the urbanization development and the experience of internati...The development of urbanization has a close relationship with fresh water resources, especially in the rapid urbanization period. By analyzing the course of the urbanization development and the experience of international ur banization development, the paper confirms the starting time of the rapid urbanization. Based on the ecological theo ry, urban fresh water consumption is composed of three types: the direct, the indirect and the induced water consump tion. And the paper constructs calculation model of the indirect and the induced water consumption. Using the related statistics data, the paper makes an empirical research on the changes of the amount and structure of water consumption. Then it discusses the correlation between the water consumption and the amount of urban population, and the result shows that the amount of the water consumption and the urban population have a remarkable correlation with the exception of the amount of the indirect water consumption, and the curves take on quadratic function form. Last, from the urban function point of view, the paper anatomizes the cause of the urban water consumption changes.展开更多
A study based on the spatial variability and contamination levels of fresh water resources by saline intrusion was conducted in the Douala coastal area. The study was aimed at highlighting the associations between maj...A study based on the spatial variability and contamination levels of fresh water resources by saline intrusion was conducted in the Douala coastal area. The study was aimed at highlighting the associations between major ions in ground water from which cause-effect relationships could be inferred. Water samples were collected from 19 stations. 3 stations were selected from the mangrove area and 16 stations were selected from the rest of the area partitioned into four transects (coastal transect, inner transect 1, inner transect 2 and inner transect 3). Sampling was done repeatedly during the dry season and these samples were analysed for physico-chemical parameters. Results show that the samples were acidic (pH: 4.7 - 6.7). Total dissolved solids (TDS) and electrical conductivity (EC) values ranged between 70.3 - 3703 mg/L and 136.4 - 7333 μS/cm respectively indicating medium salt enrichment and brackish waters. High temperatures (T°C) and low dissolved oxygen (DO) values of 26°C - 30.3°C and 0.96 - 3.9 mg/L respectively were observed and this could be interpreted as the acceleration of biological and chemical processes of ground water resources. Major ions were within the WHO limits except for Ca2+ (20.3 - 85 mg/L) and Mg2+ (6.6 - 49.6 mg/L) respectively whose concentrations were slightly higher. The leading cations were Ca2+ > Na+ > Mg2+ > K+ while were the leading anions. The multivariate analysis approach (MAA) values obtained for water variables showed that F1, F2 and F3 accounted for 61.6%, 21.5% and 9.9% respectively of total variance with strong loadings and these were considered to account for the ground and surface water quality of the area. The main water types were 63.2% , 26.3% Ca2+-Cl- and 10.5% Na+-Cl-. 89.5% of the water types had secondary salinity implying that anthropogenic sources were the source of salinity. The water was not fit for drinking. The values calculated for percentage sodium and sodium absorption ratio to determine its suitability for agricultural purposes revealed that 63.15%, 15.5%, 5.3% and 15.8% of sampled water were excellent, good, doubtful and unsuitable respectively for irrigation purposes. The need for water resource monitoring and forecasting regarding deterioration in quality is imperative before hazards of the rise in sea level arise.展开更多
Examining the descriptions of piezometric heads at two points in both the salt water and fresh water zones reveals that when the groundwater flow system is in steady state and satisfies the Dupuit assumption,the locat...Examining the descriptions of piezometric heads at two points in both the salt water and fresh water zones reveals that when the groundwater flow system is in steady state and satisfies the Dupuit assumption,the location of the fresh water—salt water interface in a homogeneous,isotropic,and unconfined coastal aquifer can be estimated based on a piezometric head of fresh water at a point in the fresh water zone(from the water table to the interface) vertically lined up with a piezometric head of salt water at a point in the salt water zone(from the interface down).Research shows that the new method is a general relation and that both the Hubbert relation describing the location of the interface and the Ghyben—Herzberg relation are special cases of this method.The method requires two piezometric wells to be close to each other and each tapping into a different zone.Measurements of piezometric heads at a well cluster consisting of piezometric wells tapping separately into fresh water and salt water zones near Beihai. China at 5-day intervals for 15 months are used to illustrate the estimation of interface location.The depth of the interface for well H5 ranges from 32 to 72 m below the sea level. (?) 2011,China University of Geosciences(Beijing) and Peking University.Production and hosting by Elsevier B.V.All rights reserved.展开更多
Background: A large proportion of Nigerians consume fish as the source of protein in their meals. This may be attributed to health factors, preference and affordability for low income earners. The incidence of Aeromon...Background: A large proportion of Nigerians consume fish as the source of protein in their meals. This may be attributed to health factors, preference and affordability for low income earners. The incidence of Aeromonas hydrophila in fresh catfish may constitute a significant health risk to the consumer if there is a horizontal transfer to man as it has been reported to be pathogenic. This study examined the possibility of fresh water catfish being a reservoir of pathogenic Aeromonas hydrophila. Method: Aeromonas hydrophila was isolated from the different organs of fresh water catfish (Clarias gariepinus and Ictalurus punctatus) obtained from Kporoko river in Lokoja. Aeromonas hydrophila was identified using both phenotypic and genotypic methods. The pathogenic traits of the Aeromonas species such as biofilm formation, production of haemolysin, enterotoxin and enzymes were determined. Results: Aeromonas hydrophila occurred in all the examined fish organs (fish, liver, kidney, skin and gut) of Clarias gariepinus but occurred only in the skin, intestine, kidney and gut of Ictalurus punctatus examined, but the incidence of Aeromonas hydrophila was prevalent in the gut of all the fishes analyzed. All the Aeromonas isolates analysed in this study produced biofilm, haemolysins and lipase enzymes. They also produced enterotoxins with values ranging between 0.069 - 1.138. Conclusion: The occurrence of Aeromonas in fresh catfish possessing these pathogenic traits is of great public health significance to man as it indicates the likelihood of man being predisposed to toxigenicity when the toxin concentration reaches a lethal value. It is therefore recommended that the internal organs of fresh catfish be thoroughly cleaned and cooked before consumption.展开更多
This study aims, first, to examine the limit for tolerance to lower salinity by an oceanic sea skater, Halobates micans, and , second, to make it clear whether exclusively fresh water Halobatinae species, Metrocoris h...This study aims, first, to examine the limit for tolerance to lower salinity by an oceanic sea skater, Halobates micans, and , second, to make it clear whether exclusively fresh water Halobatinae species, Metrocoris histrio has salinity tolerance. Adults of H. micans were collected using Neuston Net from the starboard side of R/V MIRAI on a fixed station at 8°S, 80°E, whereas those of M. histrio were collected from a small pond filled with a spring fresh water in Kochi (33°N, 133°E), Japan. Time in survival was measured in starved condition under several salinity conditions: 0‰, 2‰, 4‰, 6‰, 8‰, 9‰ and 10‰ for H. micans;0‰, 5‰, 10‰, 12.5‰, 15‰ for M. histrio. Half of adults were in coma due to lower salinity under 10‰ and time in survival was less than 10 hours under less than 4‰ for H. micans. Time in survival was half at 5‰ of 80 hours on average at 0‰ as a control and less than 10 hours at 10‰ or higher salinity for M. histrio. Relatively flexible osmo-regulation ability by H. micans would be related to wide variety of salinity condition of surface oceanic water, whereas very limited tolerance even to lower salinity of 5‰ may be permitted by the no chances to be exposed to brackish water in natural habitats of M. histrio. This study showed that salinity tolerance of Halobatinae species would reflect, directly, the salinity condition of their habitats.展开更多
Based on principles of vapor coagulation,a method of extracting fresh water from the atmosphere was put forward. Its principles are simple,and it is easy to make and install the equipment made cheaply. Moreover,there ...Based on principles of vapor coagulation,a method of extracting fresh water from the atmosphere was put forward. Its principles are simple,and it is easy to make and install the equipment made cheaply. Moreover,there is no or much less energy consumed during the extraction process,so there is no environmental pollution. In a word,this method of extracting fresh water from the atmosphere is of great practical value.展开更多
Vibrio parahaemolyticus organisms cause acute gastroenteritis in humans. These bacteria are natural inhabitants of both marine and estuarine ecosystems. In the present study, we investigated the effectiveness of a non...Vibrio parahaemolyticus organisms cause acute gastroenteritis in humans. These bacteria are natural inhabitants of both marine and estuarine ecosystems. In the present study, we investigated the effectiveness of a non-selective enrichment of sediment samples with sodium chloride prior to selective enrichment with alkaline peptone water for a better recovery of V. parahaemolyticus. Sediment samples were collected with or without 1% NaCl from the river Buriganga, located besides Dhaka city and about 400 km away from the Bay of Bengal, and from the estuary of the river Karnaphuli which flows into the Bay of Bengal. Very small number of V. parahaemolyticus (<30 MPN/g) were detected in the sediments of both river and estuary, where NaCl was not added. On the other hand, the number of V. parahaemolyticus increased to more than 40 times (1500 MPN/g) in the river and 32 times (960 MPN/g) in the estuary where NaCl were added. River sediment sample contained the serotype O9:K41 of V. parahaemolyticus and the estuarine sample contained O3:K41 and O3:KUT Our results suggest that a pre-enrichment of environmental samples with 1% NaCl helps V. parahaemolyticus to survive for at least 7 days until they are enriched with alkaline peptone water, for better recovery.展开更多
Culturable faecal coliform, epidemic, clinical, faecal and recreational beach enterococci strains possessing putative virulence genes were enumerated over the course of 5 weeks to comparatively assess their persistenc...Culturable faecal coliform, epidemic, clinical, faecal and recreational beach enterococci strains possessing putative virulence genes were enumerated over the course of 5 weeks to comparatively assess their persistence in tropical marine and fresh waters. For the clinical and epidemic strains tested, it took 2.38 ± 0.45 days for a 1-log reduction (T90) in marine water. A higher T90 average of 2.51 ± 0.08 was observed for the commensal and environmental strains. Generally, lower T90 values of 2.14 ± 0.26 and 2.15 ± 0.16 days respectively were observed for hospital and community acquired enterococci strains in fresh water mesocosms subjected to tropical ambient temperature. Beach water enterococci and enterococci recovered from faeces of humans survived for up to 20 days and 23 days respectively in fresh and marine waters. The epidemic strain, MMH594, an esp-positive clinical bacteremia isolate that previously caused multiple infections in a hospital ward outbreak fares favourably well in tropical marine and fresh aquatic environments. For enterococci, the decay rate was approximately 13% higher in fresh water than was observed for marine water. On the contrary, for E. coli, the decay rate was approximately 17% lower in fresh water than was observed in marine water. Generally, the whole, the population trends of E. coli and enterococci in fresh and marine water mesocosms did not reveal any evidence of growth. Our findings suggest that potentially pathogenic bacteria can resume active growth after three weeks of being harboured by the reservoir-beach sand and still pose threat to public health.展开更多
The European Water Framework (WFD) establishes a framework for the protection and the monitoring condition of all natural superficial waters of the member States. The Italian Legislative Decree n. 156/2006 implements ...The European Water Framework (WFD) establishes a framework for the protection and the monitoring condition of all natural superficial waters of the member States. The Italian Legislative Decree n. 156/2006 implements the WFD establishing a monitoring system which foresees a detailed detection of several physical, chemical and microbiological parameters in order to assess the qualitative status of the water body. This study reports the freshwater quality in the Reno river basin (North Italy) from 2003 to 2011. The Reno superficial water was classified as “good” in the mountain stations and at the closed basin while in all the other stations of the Po plain the quality was from “mediocre” to “poor”. The decrease of water quality was due to the flowing of artificial canals that collect discharges the wastewater of sewage treatment plants, drainage and run-off from the urban, industrial and agricultural lands. In spring-summer 2011, characterized by severe drought, a study on the distribution of pollutants and nutrients in water of the Renoriver and its tributaries highlight the impact of highway (Via Emilia) that closes the mountain basin of water courses. Along this street cities and industrial and craft have developed, increasing discharges of pollutants and nutrients in rivers. An increase of metals and nutrients was found from upstream to downstream, furthermore the concentration of the microbiological faecal indicators were two to three times higher than those determined in the water upstream of urban/industrial settlements. The thresholds of Italian Law for Hg and Pb were exceeding in all most rivers. The sediments analysis was also performed because they can be considered a sink and/or source for pollutants. In many monitoring sites the metals concentrations was higher than the thresholds of Italia Low (data not shown), but the availability of these metals was tested with mixtures of different strength extracting (EDTA, DTPA and water). The coefficient of partition solid/water (Kd) was calculated to evaluate the metals affinity to be in the aqueous phase and it increase as following Cr > Mn > Ni > Pb > Zn > Cu > Cd.展开更多
Wastewater mixed with industrial effluents is used for irrigation in Gadoon Industrial estate and thus contaminating soil. This soil was tested for heavy metal content by using atomic absorption spectrophotometer (per...Wastewater mixed with industrial effluents is used for irrigation in Gadoon Industrial estate and thus contaminating soil. This soil was tested for heavy metal content by using atomic absorption spectrophotometer (perkin elmer 700) and compared with control soil irrigated with tube well water at seven selected spots. Accumulation of the toxic metal was significantly greater in the soil irrigated with industrial effluent than control soil (p < 0.05). Manganese (Mn) was the most significant pollutant, accumulated up to 9.95 ppm in the soil irrigated with industrial waste water. It was found that the samples were containing Zn in the range of 1.596 - 6.288, Cu 0.202 - 1.236, Co 0.074 - 0.115, Ni 0.0002 - 0.544, Cr 0.243 - 0.936, Mn 3.667 - 9.955 and Pb 0.488 - 1.259 ppm. No sample was containing the heavy metal above the critical level mentioned in typical and unsafe heavy metal levels in soil.展开更多
文摘The knowledge about the population dynamics of freshwater snail intermediate host and their roles in disease transmission is little known in Bayelsa State. This study investigated the species composition of fresh water snail intermediate host in Amassoma community and the Niger Delta University Campuses during August 2019-October 2019 across five locations (Main campus Hostel, E.T.F Building, Ogboebi-Ama, Efeke-Ama, Ogbopina). Snails were collected from the water bodies with the aid of a scooping net and hand picking. The morphological identification of the snail intermediate host followed standard procedures. From the result, five hundred and seventy-one freshwater snails belonging to four genera and five species were recorded. The presence of <em>Lymnae</em> and <em>Bulinus</em> in the locations highlights foci for fascioliasis and schistosomiasis. The presence of <em>Melanoides</em> spp. is novel in Bayelsa State. The public health implications of these snails have called for timely control intervention.
文摘Alterations in blood variables of Sarotherodon melanotheron transmitted immediately from brackish water(salinity 13.71‰)to fresh water(salinity 0.12‰)were examined to evaluate the consequence of abrupt alterations in the environment on fish blood parameters.The results acquired revealed that significant reduction(p<0.05)in mean values of Haemoglobin(Hb)from 7.37±1.22 to 4.30±0.82dl-1;Packed Cell Volume(PCV)23.48±3.22 to 15.08±2.97%;Red Blood Cell(RBC)5.99±0.72 to 3.31±0.77 Cells x106;Mean Corpuscular Haemoglobin Concentration(MCHC)31.68±3.66 to 28.48±2.03 pg;and Platelets(PLT)195.44±16.77 to 138.99±9.05103 uL-1.However,notable elevation was recorded in the values of Erythrocyte Sedimentation Rate(ESR)from 4.89±0.16 to 10.58±1.48 mm/hr;White Blood Cell(WBC)27.03±2.96 to 33.09±3.72 x 109 L-1;Mean Corpuscular Volume(MCV)39.33±3.07 to 45.88±7.03 fL Neutrophils(NEUT)41.71±3.08 to 48.30±7.99%;Lymphocytes(LYMP)54.60±3.99 to 46.36±9.87%and Monocytes(MON)3.80±1.04 to 5.97±1.99%.These variations in the blood parameters were more perceptible in adult than juvenile fish.Results from this study consequently imply that direct transfer of fish to a region of lower salinity may have damaging effect on the physiology of S.melanotheron as observed in this study.
文摘The process of air-sea fresh water exchange is included successfully in the Global-Ocean-Atmosphere-Land-System model developed at the State Key Laboratory of Atmospheric Sciences andGeophysical Fluid Dynamics (LASG). The results of the coupled integration show that the cIimate drift hasbeell controlled successfully. Analyses on the responses of ocean circulation to the changes of surface freshwater or salinity forcing show that the ocean spin-up stage under flux condition for salinity is the key to theimplementation of air-sea fresh water flux coupling. This study also demonstrates that theModified-Monthly-Flux-AnomaIy coupling scheme (MMFA) brought forward by Yu and Zhang (1998)is suitable not only for daily air-sea heat flux coupling but also for daily fresh water flux coupling.
文摘Using field hydrological data, the relationship between the mixing of salt water and fresh water and the tidal range/ high tidal level in the Changjiang (Yangtze) River estuary is discussed, and the transporting and concentrating of suspended sediment in the estuary were also analysed in respect to the circulation, flocculation and stratified interface resulting from mixing.The calculation results by two-dimentional box model have confirmed the effects of the circulation on the concentrating of suspended sediment in the estuary. The conclusions derived from this work have deepened the understanding on the mixing in the Changjiang River estuary and are of significance in bo’th theory and practice.
文摘Wireless communications from air to fresh water are studied here. Our analysis relies on plane wave propagation mod-els. Specifically, the transmission loss and propagation loss of RF waves penetrating into fresh water are calculated for various propagation depths. Even though RF wireless communications are not well suited for seawater due to its high attenuation, our paper illustrates that RF communications from air to fresh water are possible. Finally, this work de-rives the optimum frequencies, which provide minimum attenuation and maximum propagation depth, for RF commu-nications from air to fresh water.
基金Under the auspices of Key Project of National Natural Science Foundation of China (No. 40535026)
文摘From the point of view of urban consumption behavior, urban fresh water consumption could be classified as three types, namely, direct, indirect and induced water consumption. A calculation approach of urban fresh water consumption was presented based on the theory of urban basic material consumption and the input-output method, which was utilized to calculate urban fresh water consumption of China, and to analyze its structural change and causes. The results show that the total urban fresh water consumption increased 561.7×109m3, and the proportion to the total national fresh water resources increased by 20 percentage points from 1952 to 2005. The proportion of direct and induced water consumption had been continuously rising, and it increased by 15 and 35 percentage points separately from 1952 to 2005, while the proportion of indirect water consumption decreased by 50 percentage points. Urban indirect water consumption was mainly related to urban grain, beef and mutton consumption, and urban induced water consumption had a close relationship with the amount of carbon emission per capita. Finally, some countermeasures were put forward to realize sustainable utilization of urban fresh water resources in China.
基金supported by the Key Project of National Natural Science Foundation of China (Grant No.40535026)
文摘The development of urbanization has a close relationship with fresh water resources, especially in the rapid urbanization period. By analyzing the course of the urbanization development and the experience of international ur banization development, the paper confirms the starting time of the rapid urbanization. Based on the ecological theo ry, urban fresh water consumption is composed of three types: the direct, the indirect and the induced water consump tion. And the paper constructs calculation model of the indirect and the induced water consumption. Using the related statistics data, the paper makes an empirical research on the changes of the amount and structure of water consumption. Then it discusses the correlation between the water consumption and the amount of urban population, and the result shows that the amount of the water consumption and the urban population have a remarkable correlation with the exception of the amount of the indirect water consumption, and the curves take on quadratic function form. Last, from the urban function point of view, the paper anatomizes the cause of the urban water consumption changes.
文摘A study based on the spatial variability and contamination levels of fresh water resources by saline intrusion was conducted in the Douala coastal area. The study was aimed at highlighting the associations between major ions in ground water from which cause-effect relationships could be inferred. Water samples were collected from 19 stations. 3 stations were selected from the mangrove area and 16 stations were selected from the rest of the area partitioned into four transects (coastal transect, inner transect 1, inner transect 2 and inner transect 3). Sampling was done repeatedly during the dry season and these samples were analysed for physico-chemical parameters. Results show that the samples were acidic (pH: 4.7 - 6.7). Total dissolved solids (TDS) and electrical conductivity (EC) values ranged between 70.3 - 3703 mg/L and 136.4 - 7333 μS/cm respectively indicating medium salt enrichment and brackish waters. High temperatures (T°C) and low dissolved oxygen (DO) values of 26°C - 30.3°C and 0.96 - 3.9 mg/L respectively were observed and this could be interpreted as the acceleration of biological and chemical processes of ground water resources. Major ions were within the WHO limits except for Ca2+ (20.3 - 85 mg/L) and Mg2+ (6.6 - 49.6 mg/L) respectively whose concentrations were slightly higher. The leading cations were Ca2+ > Na+ > Mg2+ > K+ while were the leading anions. The multivariate analysis approach (MAA) values obtained for water variables showed that F1, F2 and F3 accounted for 61.6%, 21.5% and 9.9% respectively of total variance with strong loadings and these were considered to account for the ground and surface water quality of the area. The main water types were 63.2% , 26.3% Ca2+-Cl- and 10.5% Na+-Cl-. 89.5% of the water types had secondary salinity implying that anthropogenic sources were the source of salinity. The water was not fit for drinking. The values calculated for percentage sodium and sodium absorption ratio to determine its suitability for agricultural purposes revealed that 63.15%, 15.5%, 5.3% and 15.8% of sampled water were excellent, good, doubtful and unsuitable respectively for irrigation purposes. The need for water resource monitoring and forecasting regarding deterioration in quality is imperative before hazards of the rise in sea level arise.
基金supported by the Fund for the Special Research of Doctorate Subjects of the Ministry of Education of China (No.20070491522)
文摘Examining the descriptions of piezometric heads at two points in both the salt water and fresh water zones reveals that when the groundwater flow system is in steady state and satisfies the Dupuit assumption,the location of the fresh water—salt water interface in a homogeneous,isotropic,and unconfined coastal aquifer can be estimated based on a piezometric head of fresh water at a point in the fresh water zone(from the water table to the interface) vertically lined up with a piezometric head of salt water at a point in the salt water zone(from the interface down).Research shows that the new method is a general relation and that both the Hubbert relation describing the location of the interface and the Ghyben—Herzberg relation are special cases of this method.The method requires two piezometric wells to be close to each other and each tapping into a different zone.Measurements of piezometric heads at a well cluster consisting of piezometric wells tapping separately into fresh water and salt water zones near Beihai. China at 5-day intervals for 15 months are used to illustrate the estimation of interface location.The depth of the interface for well H5 ranges from 32 to 72 m below the sea level. (?) 2011,China University of Geosciences(Beijing) and Peking University.Production and hosting by Elsevier B.V.All rights reserved.
文摘Background: A large proportion of Nigerians consume fish as the source of protein in their meals. This may be attributed to health factors, preference and affordability for low income earners. The incidence of Aeromonas hydrophila in fresh catfish may constitute a significant health risk to the consumer if there is a horizontal transfer to man as it has been reported to be pathogenic. This study examined the possibility of fresh water catfish being a reservoir of pathogenic Aeromonas hydrophila. Method: Aeromonas hydrophila was isolated from the different organs of fresh water catfish (Clarias gariepinus and Ictalurus punctatus) obtained from Kporoko river in Lokoja. Aeromonas hydrophila was identified using both phenotypic and genotypic methods. The pathogenic traits of the Aeromonas species such as biofilm formation, production of haemolysin, enterotoxin and enzymes were determined. Results: Aeromonas hydrophila occurred in all the examined fish organs (fish, liver, kidney, skin and gut) of Clarias gariepinus but occurred only in the skin, intestine, kidney and gut of Ictalurus punctatus examined, but the incidence of Aeromonas hydrophila was prevalent in the gut of all the fishes analyzed. All the Aeromonas isolates analysed in this study produced biofilm, haemolysins and lipase enzymes. They also produced enterotoxins with values ranging between 0.069 - 1.138. Conclusion: The occurrence of Aeromonas in fresh catfish possessing these pathogenic traits is of great public health significance to man as it indicates the likelihood of man being predisposed to toxigenicity when the toxin concentration reaches a lethal value. It is therefore recommended that the internal organs of fresh catfish be thoroughly cleaned and cooked before consumption.
文摘This study aims, first, to examine the limit for tolerance to lower salinity by an oceanic sea skater, Halobates micans, and , second, to make it clear whether exclusively fresh water Halobatinae species, Metrocoris histrio has salinity tolerance. Adults of H. micans were collected using Neuston Net from the starboard side of R/V MIRAI on a fixed station at 8°S, 80°E, whereas those of M. histrio were collected from a small pond filled with a spring fresh water in Kochi (33°N, 133°E), Japan. Time in survival was measured in starved condition under several salinity conditions: 0‰, 2‰, 4‰, 6‰, 8‰, 9‰ and 10‰ for H. micans;0‰, 5‰, 10‰, 12.5‰, 15‰ for M. histrio. Half of adults were in coma due to lower salinity under 10‰ and time in survival was less than 10 hours under less than 4‰ for H. micans. Time in survival was half at 5‰ of 80 hours on average at 0‰ as a control and less than 10 hours at 10‰ or higher salinity for M. histrio. Relatively flexible osmo-regulation ability by H. micans would be related to wide variety of salinity condition of surface oceanic water, whereas very limited tolerance even to lower salinity of 5‰ may be permitted by the no chances to be exposed to brackish water in natural habitats of M. histrio. This study showed that salinity tolerance of Halobatinae species would reflect, directly, the salinity condition of their habitats.
基金Supported by the National Natural Science Foundation of China(41006070)Educational Commission of Guangdong Province,China(2012KJCX0065)
文摘Based on principles of vapor coagulation,a method of extracting fresh water from the atmosphere was put forward. Its principles are simple,and it is easy to make and install the equipment made cheaply. Moreover,there is no or much less energy consumed during the extraction process,so there is no environmental pollution. In a word,this method of extracting fresh water from the atmosphere is of great practical value.
文摘Vibrio parahaemolyticus organisms cause acute gastroenteritis in humans. These bacteria are natural inhabitants of both marine and estuarine ecosystems. In the present study, we investigated the effectiveness of a non-selective enrichment of sediment samples with sodium chloride prior to selective enrichment with alkaline peptone water for a better recovery of V. parahaemolyticus. Sediment samples were collected with or without 1% NaCl from the river Buriganga, located besides Dhaka city and about 400 km away from the Bay of Bengal, and from the estuary of the river Karnaphuli which flows into the Bay of Bengal. Very small number of V. parahaemolyticus (<30 MPN/g) were detected in the sediments of both river and estuary, where NaCl was not added. On the other hand, the number of V. parahaemolyticus increased to more than 40 times (1500 MPN/g) in the river and 32 times (960 MPN/g) in the estuary where NaCl were added. River sediment sample contained the serotype O9:K41 of V. parahaemolyticus and the estuarine sample contained O3:K41 and O3:KUT Our results suggest that a pre-enrichment of environmental samples with 1% NaCl helps V. parahaemolyticus to survive for at least 7 days until they are enriched with alkaline peptone water, for better recovery.
文摘Culturable faecal coliform, epidemic, clinical, faecal and recreational beach enterococci strains possessing putative virulence genes were enumerated over the course of 5 weeks to comparatively assess their persistence in tropical marine and fresh waters. For the clinical and epidemic strains tested, it took 2.38 ± 0.45 days for a 1-log reduction (T90) in marine water. A higher T90 average of 2.51 ± 0.08 was observed for the commensal and environmental strains. Generally, lower T90 values of 2.14 ± 0.26 and 2.15 ± 0.16 days respectively were observed for hospital and community acquired enterococci strains in fresh water mesocosms subjected to tropical ambient temperature. Beach water enterococci and enterococci recovered from faeces of humans survived for up to 20 days and 23 days respectively in fresh and marine waters. The epidemic strain, MMH594, an esp-positive clinical bacteremia isolate that previously caused multiple infections in a hospital ward outbreak fares favourably well in tropical marine and fresh aquatic environments. For enterococci, the decay rate was approximately 13% higher in fresh water than was observed for marine water. On the contrary, for E. coli, the decay rate was approximately 17% lower in fresh water than was observed in marine water. Generally, the whole, the population trends of E. coli and enterococci in fresh and marine water mesocosms did not reveal any evidence of growth. Our findings suggest that potentially pathogenic bacteria can resume active growth after three weeks of being harboured by the reservoir-beach sand and still pose threat to public health.
文摘The European Water Framework (WFD) establishes a framework for the protection and the monitoring condition of all natural superficial waters of the member States. The Italian Legislative Decree n. 156/2006 implements the WFD establishing a monitoring system which foresees a detailed detection of several physical, chemical and microbiological parameters in order to assess the qualitative status of the water body. This study reports the freshwater quality in the Reno river basin (North Italy) from 2003 to 2011. The Reno superficial water was classified as “good” in the mountain stations and at the closed basin while in all the other stations of the Po plain the quality was from “mediocre” to “poor”. The decrease of water quality was due to the flowing of artificial canals that collect discharges the wastewater of sewage treatment plants, drainage and run-off from the urban, industrial and agricultural lands. In spring-summer 2011, characterized by severe drought, a study on the distribution of pollutants and nutrients in water of the Renoriver and its tributaries highlight the impact of highway (Via Emilia) that closes the mountain basin of water courses. Along this street cities and industrial and craft have developed, increasing discharges of pollutants and nutrients in rivers. An increase of metals and nutrients was found from upstream to downstream, furthermore the concentration of the microbiological faecal indicators were two to three times higher than those determined in the water upstream of urban/industrial settlements. The thresholds of Italian Law for Hg and Pb were exceeding in all most rivers. The sediments analysis was also performed because they can be considered a sink and/or source for pollutants. In many monitoring sites the metals concentrations was higher than the thresholds of Italia Low (data not shown), but the availability of these metals was tested with mixtures of different strength extracting (EDTA, DTPA and water). The coefficient of partition solid/water (Kd) was calculated to evaluate the metals affinity to be in the aqueous phase and it increase as following Cr > Mn > Ni > Pb > Zn > Cu > Cd.
文摘Wastewater mixed with industrial effluents is used for irrigation in Gadoon Industrial estate and thus contaminating soil. This soil was tested for heavy metal content by using atomic absorption spectrophotometer (perkin elmer 700) and compared with control soil irrigated with tube well water at seven selected spots. Accumulation of the toxic metal was significantly greater in the soil irrigated with industrial effluent than control soil (p < 0.05). Manganese (Mn) was the most significant pollutant, accumulated up to 9.95 ppm in the soil irrigated with industrial waste water. It was found that the samples were containing Zn in the range of 1.596 - 6.288, Cu 0.202 - 1.236, Co 0.074 - 0.115, Ni 0.0002 - 0.544, Cr 0.243 - 0.936, Mn 3.667 - 9.955 and Pb 0.488 - 1.259 ppm. No sample was containing the heavy metal above the critical level mentioned in typical and unsafe heavy metal levels in soil.
