Estimating sediment transport capacity of overland flow is essential to the development of physically based soil erosion models.Correlation analysis indicates that stream power is a dominant factor for sediment transp...Estimating sediment transport capacity of overland flow is essential to the development of physically based soil erosion models.Correlation analysis indicates that stream power is a dominant factor for sediment transport in overland flows and a new sediment transport capacity equation is proposed based on dimensional analysis.The coefficients of the new equation are calibrated using the published laboratory data,and rainfall impact is taken into consideration by adding an empirical factor on the dimensionless critical stream power.The new sediment transport capacity equation is a function of stream power,rainfall impacted critical stream power and slope.The new equation is applied in a one-dimensional soil erosion model to simulate field data of a runoff plot and the simulation results are reliable.展开更多
Urban sprawl has been a prevailing phenomenon in developing countries like China,potentially resulting in significant carbon dioxide(CO_(2))emissions from the transport sector.However,the impact of urban sprawl on tra...Urban sprawl has been a prevailing phenomenon in developing countries like China,potentially resulting in significant carbon dioxide(CO_(2))emissions from the transport sector.However,the impact of urban sprawl on transport CO_(2) emissions(TCEs)is still not fully understood and remains somewhat rudimentary.To systematically investigate how urban sprawl influences TCEs,we employ panel regression and panel threshold regression for 274 Chinese cities(2005-2020),and obtain some new findings.Our results affirm that the degree of urban sprawl is positively associated with TCEs,and this holds true in different groups of city size and geographical region,while significant heterogeneity is observed in terms of such impact.Interestingly,we find urban sprawl nonlinearly impacts TCEs—with an equal increase in urban sprawl degree,TCEs are even lower in cities with larger population size and better economic condition,particularly in East China.Furthermore,the low-carbon city pilot policy shows potential in mitigating sprawl's impact on TCEs.Drawing on our findings,we argue that to achieve the target of TCEs reduction in China by curbing urban sprawl,more priority should be placed on relatively small,less developed,and geographically inferior cities for cost-efficiency reasons when formulating future urban development strategies.展开更多
The source-receptor matrix of PM_(2.5)concentration from local and regional sources in the Beijing-Tianjin-Hebei(BTH)and surrounding provinces has been created in previous studies.However,because the spatial distribut...The source-receptor matrix of PM_(2.5)concentration from local and regional sources in the Beijing-Tianjin-Hebei(BTH)and surrounding provinces has been created in previous studies.However,because the spatial distribution of concentration does not necessarily match with that of the population,such concentration-based source-receptor matrix may not fully reflect the importance of pollutant control effectiveness in reducing the PM_(2.5)-related health impacts.To demonstrate that,we study the source-receptor matrix of the PM_(2.5)-related deaths instead,with inclusion of the spatial correlations between the concentrations and the population.The advanced source apportionment numerical model combined with the integrated exposure-response functions is used for BTH and surrounding regions in 2017.We observed that the relative contribution to PM_(2.5)-related deaths of local emissions was 0.75%to 20.77%larger than that of PM_(2.5)concentrations.Such results address the importance of local emissions control for reducing health impacts of PM_(2.5)particularly for local residents.Contribution of regional transport to PM_(2.5)-related deaths in rural area was 22%larger than that in urban area due to the spatial pattern of regional transport which was more related to the rural population.This resulted in an environmental inequality in the sense that people staying in rural area with access to less educational resources are subjected to higher impacts from regional transport as compared with their more resourceful and knowledgeable urban compatriots.An unexpected benefit from the multi-regional joint controls is suggested for its effectiveness in reducing the regional transport of PM_(2.5)pollution thus mitigating the associated environmental inequality.展开更多
基金supported by the National Basic Research Program of China ("973" Program) (Grant No. 2007CB407202)
文摘Estimating sediment transport capacity of overland flow is essential to the development of physically based soil erosion models.Correlation analysis indicates that stream power is a dominant factor for sediment transport in overland flows and a new sediment transport capacity equation is proposed based on dimensional analysis.The coefficients of the new equation are calibrated using the published laboratory data,and rainfall impact is taken into consideration by adding an empirical factor on the dimensionless critical stream power.The new sediment transport capacity equation is a function of stream power,rainfall impacted critical stream power and slope.The new equation is applied in a one-dimensional soil erosion model to simulate field data of a runoff plot and the simulation results are reliable.
基金National Key Research and Development Program of China,No.2022YFC3800101。
文摘Urban sprawl has been a prevailing phenomenon in developing countries like China,potentially resulting in significant carbon dioxide(CO_(2))emissions from the transport sector.However,the impact of urban sprawl on transport CO_(2) emissions(TCEs)is still not fully understood and remains somewhat rudimentary.To systematically investigate how urban sprawl influences TCEs,we employ panel regression and panel threshold regression for 274 Chinese cities(2005-2020),and obtain some new findings.Our results affirm that the degree of urban sprawl is positively associated with TCEs,and this holds true in different groups of city size and geographical region,while significant heterogeneity is observed in terms of such impact.Interestingly,we find urban sprawl nonlinearly impacts TCEs—with an equal increase in urban sprawl degree,TCEs are even lower in cities with larger population size and better economic condition,particularly in East China.Furthermore,the low-carbon city pilot policy shows potential in mitigating sprawl's impact on TCEs.Drawing on our findings,we argue that to achieve the target of TCEs reduction in China by curbing urban sprawl,more priority should be placed on relatively small,less developed,and geographically inferior cities for cost-efficiency reasons when formulating future urban development strategies.
基金National Natural Science Foundation of China(Grant Nos.41907190&21625701)Beijing Municipal Commission of Science and Technology(Z191100009119001&Z191100009119004)Tsinghua-Toyota Research Center.This work was completed on the“Explorer 100”cluster system of Tsinghua National Laboratory for Information Science and Technology.
文摘The source-receptor matrix of PM_(2.5)concentration from local and regional sources in the Beijing-Tianjin-Hebei(BTH)and surrounding provinces has been created in previous studies.However,because the spatial distribution of concentration does not necessarily match with that of the population,such concentration-based source-receptor matrix may not fully reflect the importance of pollutant control effectiveness in reducing the PM_(2.5)-related health impacts.To demonstrate that,we study the source-receptor matrix of the PM_(2.5)-related deaths instead,with inclusion of the spatial correlations between the concentrations and the population.The advanced source apportionment numerical model combined with the integrated exposure-response functions is used for BTH and surrounding regions in 2017.We observed that the relative contribution to PM_(2.5)-related deaths of local emissions was 0.75%to 20.77%larger than that of PM_(2.5)concentrations.Such results address the importance of local emissions control for reducing health impacts of PM_(2.5)particularly for local residents.Contribution of regional transport to PM_(2.5)-related deaths in rural area was 22%larger than that in urban area due to the spatial pattern of regional transport which was more related to the rural population.This resulted in an environmental inequality in the sense that people staying in rural area with access to less educational resources are subjected to higher impacts from regional transport as compared with their more resourceful and knowledgeable urban compatriots.An unexpected benefit from the multi-regional joint controls is suggested for its effectiveness in reducing the regional transport of PM_(2.5)pollution thus mitigating the associated environmental inequality.
