It is important to quantitatively understand the methane adsorption and transport mechanism in coal for an evaluation of the reserves and for its production forecast. In this work, a block coal sample was chosen to pe...It is important to quantitatively understand the methane adsorption and transport mechanism in coal for an evaluation of the reserves and for its production forecast. In this work, a block coal sample was chosen to perform the CH4 adsorption experiments using the gravimetric method at temperatures of 293.60 K, 311.26 K, 332.98 K and 352.55 K and pressures up to 19 MPa. The excess adsorption capacity of CH4 in dry block anthracite increased, followed by a sequence decrease with the increasing pressure. High temperature restrained the growth of the excess adsorption due to that the adsorption is an intrinsically physical and exothermic process. The excess adsorption peak decreased slowly with the increase of temperature and intersected at a pressure of more than 18 MPa; meanwhile, the pressure at the excess adsorption peak increased.The existing correlations were examined in terms of density rather than pressure. The DR+k correlation, with an average relative deviation of ±0.51%, fitted our data better than the others, with an average relative deviation of up to 2.29%. The transportation characteristics of CH4 adsorption was also investigated in this study, including the adsorption rate and diffusion in block coal. The kinetic data could be described by a modified unipore model. The adsorption rates were found to exhibit dependence on pressure and temperature at low pressures, while the calculated diffusivities exhibited little temperature dependence. In addition, the kinetic characteristics were compared between CH4 and CO2 adsorption on the block coal. The excess adsorption ratios of CO2 to CH4obtained from the DR+k model decreased with the increasing pressure.展开更多
Polycyclic aromatic hydrocarbons(PAHs) are ubiquitous in the atmosphere and they mostly stem from the imperfect combustion of fossil fuels and biofuels.PAHs are inherently associated with homogenous fine particles or ...Polycyclic aromatic hydrocarbons(PAHs) are ubiquitous in the atmosphere and they mostly stem from the imperfect combustion of fossil fuels and biofuels.PAHs are inherently associated with homogenous fine particles or distributed to different-sized particles during the aging of air masses.PAHs carried by fine particles undergo a long-range transport to remote areas while those adsorbed on coarse particles have a shorter lifetime in ambient air.More importantly, PAHs with higher molecular weights tend to be bound with finer particles and can deeply enter the lungs, posing severe health risks to humans.Thus, the environmental fate and health effects of particulate PAHs are strongly size-dependent.This review summarizes the size distributions of particulate PAHs freshly emitted from combustion sources as well as the distribution patterns of PAHs in ambient particles.It was found that PAHs from stationary sources are primarily bound to fine particles, which are slightly larger than particles to which PAHs from mobile sources are bound.In ambient air, particulate PAHs are distributed in larger size modes than those in the combustion fume, and the particle size decreases with PAH molecular weight increasing.The relevant mechanisms and influencing factors of particle size distribution changes are illustrated in this article, which are essentially attributed to combustion and ambient temperature as well as the physical and chemical properties of PAHs.Overall, the study on the particle size distribution of PAHs will contribute for a full understanding of the origin, atmospheric behaviors and health effects of particulate PAHs.展开更多
This study encompassed the regular observation of nine polycyclic aromatic hydrocarbons(PAHs)and three nitro-PAHs(NPAHs)in particulate matter(PM)in Shanghai in summer and winter from 2010 to 2018.The results showed th...This study encompassed the regular observation of nine polycyclic aromatic hydrocarbons(PAHs)and three nitro-PAHs(NPAHs)in particulate matter(PM)in Shanghai in summer and winter from 2010 to 2018.The results showed that the mean concentrations of∑PAHs in summer decreased by 24.7%in 2013 and 18.1%in 2017 but increased by 10.2%in 2015 compared to the data in 2010.However,the mean concentrations of∑PAHs in winter decreased by 39.7%from 2010(12.8±4.55 ng/m^3)to 2018(7.72±3.33 ng/m^3),and the mean concentrations of 1-nitropyrene in winter decreased by 79.0%from 2010(42.3±16.1 pg/m^3)to 2018(8.90±2.09 pg/m^3).Correlation analysis with meteorological conditions revealed that the PAH and NPAH concentrations were both influenced by ambient temperature.The diagnostic ratios of PAHs and factor analysis showed that they were mainly affected by traffic emissions with some coal and/or biomass combustion.The ratio of 2-nitrofluoranthene to 2-nitropyrene was near 10,which indicated that the OH radical-initiated reaction was the main pathway leading to their secondary formation.Moreover,backward trajectories revealed different air mass routes in each sampling period,indicating a high possibility of source effects from the northern area in winter in addition to local and surrounding influences.Meanwhile,the mean total benzo[a]pyrene-equivalent concentrations in Shanghai in winter decreased by 50.8%from 2010(1860±645 pg/m^3)to 2018(916±363 pg/m^3).These results indicated the positive effects of the various policies and regulations issued by Chinese authorities.展开更多
A three-year sampling campaign was conducted at a roadside air pollution monitoring station in the urban area of Kanazawa, Japan. Due to a new emission regulation, PAHs levels decreased over the sampling campaign, exh...A three-year sampling campaign was conducted at a roadside air pollution monitoring station in the urban area of Kanazawa, Japan. Due to a new emission regulation, PAHs levels decreased over the sampling campaign, exhibiting values of 706 ± 413 pg/m^(3) in 2017, 559 ±384 pg/m^(3) in 2018, and 473 ± 234 pg/m^(3) in 2019. In each year, similar seasonal variations in PAHs levels were observed, with higher levels observed in winter and lower levels in summer. Among the PAHs isomer ratios, we observed that the ratio of benzo[b]fluoranthene(BbF) and benzo[k]fluoranthene(BkF), [Bb F]/([BbF] + [BkF]), and the ratio of indeno[1,2,3-cd]pyrene(IDP) and benzo[ghi]perylene(BgPe), [IDP]/([BgPe] + [IDP]), showed stability over the sampling campaign and were less affected by the new emission regulation, seasonal variations, and regional characteristics. When using the combined ratio ranges of 0.66-0.80([Bb F]/[BbF] + [BkF]) and 0.26-0.49([IDP]/[Bg Pe] + [IDP]), traffic emissions were clearly distinguished from other PAHs emission sources. Principal component analysis(PCA) and positive matrix factorization(PMF) were also performed to further analyse the characteristics of traffic-related PAHs. Overall, this study affirmed the effectiveness of the new emission regulation in the reduction of PAHs emissions and provided a combined range for identifying PAHs traffic emission sources.展开更多
基金supported by Liaoning Provincial Natural Science Foundation of China(201202028)the National Program on the Key Basic Research Project(No.2011CB707304)+1 种基金the National Natural Science Foundation of China(No.51006016)the China Scholarship Council
文摘It is important to quantitatively understand the methane adsorption and transport mechanism in coal for an evaluation of the reserves and for its production forecast. In this work, a block coal sample was chosen to perform the CH4 adsorption experiments using the gravimetric method at temperatures of 293.60 K, 311.26 K, 332.98 K and 352.55 K and pressures up to 19 MPa. The excess adsorption capacity of CH4 in dry block anthracite increased, followed by a sequence decrease with the increasing pressure. High temperature restrained the growth of the excess adsorption due to that the adsorption is an intrinsically physical and exothermic process. The excess adsorption peak decreased slowly with the increase of temperature and intersected at a pressure of more than 18 MPa; meanwhile, the pressure at the excess adsorption peak increased.The existing correlations were examined in terms of density rather than pressure. The DR+k correlation, with an average relative deviation of ±0.51%, fitted our data better than the others, with an average relative deviation of up to 2.29%. The transportation characteristics of CH4 adsorption was also investigated in this study, including the adsorption rate and diffusion in block coal. The kinetic data could be described by a modified unipore model. The adsorption rates were found to exhibit dependence on pressure and temperature at low pressures, while the calculated diffusivities exhibited little temperature dependence. In addition, the kinetic characteristics were compared between CH4 and CO2 adsorption on the block coal. The excess adsorption ratios of CO2 to CH4obtained from the DR+k model decreased with the increasing pressure.
基金supported in part by a Grant in Aid for Scientific Research (Nos.17K08388 and 17H06283) from the Ministry of Education, Culture, Sports, Science and Technologythe cooperative research program of Institute of Nature and Environmental Technology, Kanazawa University (Nos.16007, 17002 and 17037).
文摘Polycyclic aromatic hydrocarbons(PAHs) are ubiquitous in the atmosphere and they mostly stem from the imperfect combustion of fossil fuels and biofuels.PAHs are inherently associated with homogenous fine particles or distributed to different-sized particles during the aging of air masses.PAHs carried by fine particles undergo a long-range transport to remote areas while those adsorbed on coarse particles have a shorter lifetime in ambient air.More importantly, PAHs with higher molecular weights tend to be bound with finer particles and can deeply enter the lungs, posing severe health risks to humans.Thus, the environmental fate and health effects of particulate PAHs are strongly size-dependent.This review summarizes the size distributions of particulate PAHs freshly emitted from combustion sources as well as the distribution patterns of PAHs in ambient particles.It was found that PAHs from stationary sources are primarily bound to fine particles, which are slightly larger than particles to which PAHs from mobile sources are bound.In ambient air, particulate PAHs are distributed in larger size modes than those in the combustion fume, and the particle size decreases with PAH molecular weight increasing.The relevant mechanisms and influencing factors of particle size distribution changes are illustrated in this article, which are essentially attributed to combustion and ambient temperature as well as the physical and chemical properties of PAHs.Overall, the study on the particle size distribution of PAHs will contribute for a full understanding of the origin, atmospheric behaviors and health effects of particulate PAHs.
基金the Ministry of Education,Culture,Sports,Science and Technology,Japan(17K08388)the Sasakawa Scientific Research Grant(2020–3008)from The Japan Science Society+3 种基金the Environment Research and Technology Development Fund(5–1951)of the Environmental Restoration and Conservation Agency of Japanthe Sumitomo Foundation,Japan(183115)the CHOZEN Project of Kanazawa University,Japanthe cooperative research programs of Institute of Nature and Environmental Technology,Kanazawa University,Japan(20016,20062)。
文摘This study encompassed the regular observation of nine polycyclic aromatic hydrocarbons(PAHs)and three nitro-PAHs(NPAHs)in particulate matter(PM)in Shanghai in summer and winter from 2010 to 2018.The results showed that the mean concentrations of∑PAHs in summer decreased by 24.7%in 2013 and 18.1%in 2017 but increased by 10.2%in 2015 compared to the data in 2010.However,the mean concentrations of∑PAHs in winter decreased by 39.7%from 2010(12.8±4.55 ng/m^3)to 2018(7.72±3.33 ng/m^3),and the mean concentrations of 1-nitropyrene in winter decreased by 79.0%from 2010(42.3±16.1 pg/m^3)to 2018(8.90±2.09 pg/m^3).Correlation analysis with meteorological conditions revealed that the PAH and NPAH concentrations were both influenced by ambient temperature.The diagnostic ratios of PAHs and factor analysis showed that they were mainly affected by traffic emissions with some coal and/or biomass combustion.The ratio of 2-nitrofluoranthene to 2-nitropyrene was near 10,which indicated that the OH radical-initiated reaction was the main pathway leading to their secondary formation.Moreover,backward trajectories revealed different air mass routes in each sampling period,indicating a high possibility of source effects from the northern area in winter in addition to local and surrounding influences.Meanwhile,the mean total benzo[a]pyrene-equivalent concentrations in Shanghai in winter decreased by 50.8%from 2010(1860±645 pg/m^3)to 2018(916±363 pg/m^3).These results indicated the positive effects of the various policies and regulations issued by Chinese authorities.
基金supported by the Bilateral Open Partnership Joint Research Projects of the Japan Society for the Promotion of Science, Japan (JPJSBP120219914)the Environment Research and Technology Development Fund (5-1951) of the Environmental Restoration and Conservation Agency of Japan+1 种基金the CHOZEN Project of Kanazawa University, Japanthe cooperative research programs of Institute of Nature and Environmental Technology, Kanazawa University, Japan (21001)。
文摘A three-year sampling campaign was conducted at a roadside air pollution monitoring station in the urban area of Kanazawa, Japan. Due to a new emission regulation, PAHs levels decreased over the sampling campaign, exhibiting values of 706 ± 413 pg/m^(3) in 2017, 559 ±384 pg/m^(3) in 2018, and 473 ± 234 pg/m^(3) in 2019. In each year, similar seasonal variations in PAHs levels were observed, with higher levels observed in winter and lower levels in summer. Among the PAHs isomer ratios, we observed that the ratio of benzo[b]fluoranthene(BbF) and benzo[k]fluoranthene(BkF), [Bb F]/([BbF] + [BkF]), and the ratio of indeno[1,2,3-cd]pyrene(IDP) and benzo[ghi]perylene(BgPe), [IDP]/([BgPe] + [IDP]), showed stability over the sampling campaign and were less affected by the new emission regulation, seasonal variations, and regional characteristics. When using the combined ratio ranges of 0.66-0.80([Bb F]/[BbF] + [BkF]) and 0.26-0.49([IDP]/[Bg Pe] + [IDP]), traffic emissions were clearly distinguished from other PAHs emission sources. Principal component analysis(PCA) and positive matrix factorization(PMF) were also performed to further analyse the characteristics of traffic-related PAHs. Overall, this study affirmed the effectiveness of the new emission regulation in the reduction of PAHs emissions and provided a combined range for identifying PAHs traffic emission sources.
