The Yangtze River Delta（YRD） region is one of the most prosperous and densely populated regions in China and is facing tremendous pressure to mitigate vehicle emissions and improve air quality.Our assessment has rev...The Yangtze River Delta（YRD） region is one of the most prosperous and densely populated regions in China and is facing tremendous pressure to mitigate vehicle emissions and improve air quality.Our assessment has revealed that mitigating vehicle emissions of NOx would be more difficult than reducing the emissions of other major vehicular pollutants（e.g.,CO,HC and PM_（2.5）） in the YRD region.Even in Shanghai,where the emission control implemented are more stringent than in Jiangsu and Zhejiang,we observed little to no reduction in NOx emissions from 2000 to 2010.Emission-reduction targets for HC,NOx and PM_（2.5） are determined using a response surface modeling tool for better air quality.We design city-specific emission control strategies for three vehicle-populated cities in the YRD region：Shanghai and Nanjing and Wuxi in Jiangsu.Our results indicate that even if stringent emission control consisting of the Euro 6/VI standards,the limitation of vehicle population and usage,and the scrappage of older vehicles is applied,Nanjing and Wuxi will not be able to meet the NOx emissions target by 2020.Therefore,additional control measures are proposed for Nanjing and Wuxi to further mitigate NOx emissions from heavy-duty diesel vehicles.展开更多
To improve flood control efficiency and increase urban resilience to flooding,the impacts of forest type change on flood control in the upper reach of the Tingjiang River(URTR) were evaluated by a modified model based...To improve flood control efficiency and increase urban resilience to flooding,the impacts of forest type change on flood control in the upper reach of the Tingjiang River(URTR) were evaluated by a modified model based on the Soil Conservation Service curve number(SCS-CN) method. Parameters of the model were selected and determined according to the comprehensive analysis of model evaluation indexes. The first simulation of forest reconstruction scenario,namely a coniferous forest covering 59.35km^2 is replaced by a broad-leaved forest showed no significant impact on the flood reduction in the URTR. The second simulation was added with 61.75km^2 bamboo forest replaced by broad-leaved forest,the reduction of flood peak discharge and flood volume could be improved significantly. Specifically,flood peak discharge of 10-year return period event was reduced to 7-year event,and the reduction rate of small flood was 21%-28%. Moreover,the flood volume was reduced by 9%-14% and 18%-35% for moderate floods and small floods,respectively. The resultssuggest that the bamboo forest reconstruction is an effective control solution for small to moderate flood in the URTR,the effect of forest conversion on flood volume is increasingly reduced as the rainfall amount increases to more extreme magnitude. Using a hydrological model with scenarios analysis is an effective simulation approach in investigating the relationship between forest type change and flood control. This method would provide reliable support for flood control and disaster mitigation in mountainous cities.展开更多
基金sponsored by the National Science&Technology Pillar Program of China(No.2013BAC13B03)the National Natural Science Foundation of China(Nos.51322804 and 91544222)
文摘The Yangtze River Delta（YRD） region is one of the most prosperous and densely populated regions in China and is facing tremendous pressure to mitigate vehicle emissions and improve air quality.Our assessment has revealed that mitigating vehicle emissions of NOx would be more difficult than reducing the emissions of other major vehicular pollutants（e.g.,CO,HC and PM_（2.5）） in the YRD region.Even in Shanghai,where the emission control implemented are more stringent than in Jiangsu and Zhejiang,we observed little to no reduction in NOx emissions from 2000 to 2010.Emission-reduction targets for HC,NOx and PM_（2.5） are determined using a response surface modeling tool for better air quality.We design city-specific emission control strategies for three vehicle-populated cities in the YRD region：Shanghai and Nanjing and Wuxi in Jiangsu.Our results indicate that even if stringent emission control consisting of the Euro 6/VI standards,the limitation of vehicle population and usage,and the scrappage of older vehicles is applied,Nanjing and Wuxi will not be able to meet the NOx emissions target by 2020.Therefore,additional control measures are proposed for Nanjing and Wuxi to further mitigate NOx emissions from heavy-duty diesel vehicles.
基金funded by the National Natural Science Foundation of China (Grants No.51278239)
文摘To improve flood control efficiency and increase urban resilience to flooding,the impacts of forest type change on flood control in the upper reach of the Tingjiang River(URTR) were evaluated by a modified model based on the Soil Conservation Service curve number(SCS-CN) method. Parameters of the model were selected and determined according to the comprehensive analysis of model evaluation indexes. The first simulation of forest reconstruction scenario,namely a coniferous forest covering 59.35km^2 is replaced by a broad-leaved forest showed no significant impact on the flood reduction in the URTR. The second simulation was added with 61.75km^2 bamboo forest replaced by broad-leaved forest,the reduction of flood peak discharge and flood volume could be improved significantly. Specifically,flood peak discharge of 10-year return period event was reduced to 7-year event,and the reduction rate of small flood was 21%-28%. Moreover,the flood volume was reduced by 9%-14% and 18%-35% for moderate floods and small floods,respectively. The resultssuggest that the bamboo forest reconstruction is an effective control solution for small to moderate flood in the URTR,the effect of forest conversion on flood volume is increasingly reduced as the rainfall amount increases to more extreme magnitude. Using a hydrological model with scenarios analysis is an effective simulation approach in investigating the relationship between forest type change and flood control. This method would provide reliable support for flood control and disaster mitigation in mountainous cities.
