With urbanization and population migration,some Chinese cities fall into decline whereas others prosper.Using nighttime light data,we redefine the city based on economic function and evaluate the city size distributio...With urbanization and population migration,some Chinese cities fall into decline whereas others prosper.Using nighttime light data,we redefine the city based on economic function and evaluate the city size distribution in representative countries.The results provide evidence not only for Zipfs law,but also for a distortion in China s current city size distribution.This study proposes a feasible method to predict urban population distribution based on the role of geographical factors in regional development,following the idea of spatial equilibrium.This prediction suggests that the divergence of city size in China tends to be pronounced,with inter-regional income disparity being narrowed and the city size distribution following Zipfs law.The Chinese government should further relax restrictions on population inflow into large cities and prepare for more migration in the future.展开更多
目的利用地理信息系统(geographic information system,GIS)可视化分析畜牧场中重金属污染的空间分布规律。方法利用优化GIS布点,结合GPS精准采集黑龙江省大庆市杜尔伯特蒙古族自治县整体畜牧场园区内部10 cm,50 cm深度的土壤、地表水...目的利用地理信息系统(geographic information system,GIS)可视化分析畜牧场中重金属污染的空间分布规律。方法利用优化GIS布点,结合GPS精准采集黑龙江省大庆市杜尔伯特蒙古族自治县整体畜牧场园区内部10 cm,50 cm深度的土壤、地表水及园区粪便样品。对主要重金属元素As、Hg、Cd、Pb、Cr、Cu、Ni、Zn依据国标和行标方法进行检测,通过GIS反距离加权插值法和污染指数法对场地超标重金属进行污染空间格局分析和污染评价。结果不同土层的单因子污染指数中As元素均为重度污染级别,其他7种元素属于安全等级,综合污染指数属于重污染等级。畜牧场内外地表水中Ni元素以及牛饮用水中Sb元素单因子污染指数属于警戒线等级,其他元素属于安全等级,其水样的综合污染指数均为轻度污染等级。粪便样品的所有重金属元素的单因子污染指数和综合污染指数均属于安全等级。重金属污染污染呈现垂向由上至下逐渐增大的空间分布特征,水平分布结构相似。结论应用GIS可更加准确更加直观的获得重金属在不同介质,不同深度下的空间分布规律和污染情况。展开更多
基金The authors acknowledge research support from the National Natural Science Foundation of China(Nos.72073094 and 71834005)Shanghai Institute for National Economy,Shanghai Institute of International Finance and Economics,and the China Merchants Charitable Foundation.
文摘With urbanization and population migration,some Chinese cities fall into decline whereas others prosper.Using nighttime light data,we redefine the city based on economic function and evaluate the city size distribution in representative countries.The results provide evidence not only for Zipfs law,but also for a distortion in China s current city size distribution.This study proposes a feasible method to predict urban population distribution based on the role of geographical factors in regional development,following the idea of spatial equilibrium.This prediction suggests that the divergence of city size in China tends to be pronounced,with inter-regional income disparity being narrowed and the city size distribution following Zipfs law.The Chinese government should further relax restrictions on population inflow into large cities and prepare for more migration in the future.
文摘目的利用地理信息系统(geographic information system,GIS)可视化分析畜牧场中重金属污染的空间分布规律。方法利用优化GIS布点,结合GPS精准采集黑龙江省大庆市杜尔伯特蒙古族自治县整体畜牧场园区内部10 cm,50 cm深度的土壤、地表水及园区粪便样品。对主要重金属元素As、Hg、Cd、Pb、Cr、Cu、Ni、Zn依据国标和行标方法进行检测,通过GIS反距离加权插值法和污染指数法对场地超标重金属进行污染空间格局分析和污染评价。结果不同土层的单因子污染指数中As元素均为重度污染级别,其他7种元素属于安全等级,综合污染指数属于重污染等级。畜牧场内外地表水中Ni元素以及牛饮用水中Sb元素单因子污染指数属于警戒线等级,其他元素属于安全等级,其水样的综合污染指数均为轻度污染等级。粪便样品的所有重金属元素的单因子污染指数和综合污染指数均属于安全等级。重金属污染污染呈现垂向由上至下逐渐增大的空间分布特征,水平分布结构相似。结论应用GIS可更加准确更加直观的获得重金属在不同介质,不同深度下的空间分布规律和污染情况。
