The drivers of risk to water security in Shanghai

Big cities are often said to have big water problems, and Shanghai is no exception. In this paper, we examine and compare the influence of the major factors that give rise to the risk of water insecurity in Shanghai. There is an extensive and diverse literature on these issues, dealt with in isolation, and here, we provide a synthesis of the literature, together with our own assessments and calculations, to assess what are the risks to Shanghai’s water supply and what is our degree of confidence in this assessment. We describe the systems that supply water to the city, and past and future changes in the systems, including changes in the glaciers that supply some water to the river, changes in climate, changes in land use, the construction of dams, and water diversions. We show how, at the same time as Shanghai is increasing its dependence on the Yangtze river, water diversions and sea level rise are increasing the risk that this water will be too saline to consume at certain times of the year. This analysis suggests that most of the major drivers of the risk to water security in Shanghai are within the power of environmental managers to control.     

Marine aquaculture regulates dissimilatory nitrate reduction processes in a typical semi-enclosed bay of southeastern China

Marine aquaculture in semi-enclosed bays can significantly influence nutrient cycling in coastal ecosystems. However, the impact of marine aquaculture on the dynamics of dissimilatory nitrate reduction processes (DNRPs) and the fate of reactive nitrogen remain poorly understood. In this study, the rates of DNRPs and the abundances of related functional genes were investigated in aquaculture and non-aquaculture areas. The results showed that marine aquaculture significantly increased the denitrification (DNF) and dissimilatory nitrate reduction to ammonium (DNRA) rates and decreased the rate of anaerobic ammonium oxidation (ANA), as compared with non-aquaculture sites. DNF was the dominant pathway contributing to the total nitrate reduction, and its contribution to the total nitrate reduction significantly increased from 66.72% at non-aquaculture sites to 78.50% at aquaculture sites. Marine aquaculture can significantly affect the physicochemical characteristics of sediment and the abundances of related functional genes, leading to variations in the nitrate reduction rates. Although nitrate removal rates increased in the marine aquaculture area, ammonification rates and the nitrogen retention index in the aquaculture areas were 2.19 and 1.24 times, respectively, higher than those at non-aquaculture sites. Net reactive nitrogen retention exceeded nitrogen removal in the aquaculture area, and the retained reactive nitrogen could diffuse with the tidal current to the entire bay, thereby aggravating N pollution in the entire study area. These results show that marine aquaculture is the dominant source of nitrogen pollution in semi-enclosed bays. This study can provide insights into nitrogen pollution control in semi-enclosed bays with well-developed marine aquaculture.     

Erratum to: Estimating urban water demand under conditions of rapid growth: the case of Shanghai

Regional Environmental Change - Many of the world’s major cities are expected to face significant water shortages in coming decades, largely due to increased demand arising from economic and...     

垃圾填埋场衬垫对Cr(Ⅵ)和Zn(Ⅱ)吸附的动力学研究

通过静态平衡吸附试验对垃圾填埋场衬垫土壤材料对Cr(Ⅵ)和Zn(Ⅱ)的吸附进行了观察.在试验中考察了溶液的初始浓度、pH值和溶液的温度对吸附的影响,通过动力学实验确定了动力学参数,并探讨了天然黏土材料对重金属Cr(Ⅵ)和Zn(Ⅱ)的吸附机理.结果显示,黏土对重金属的吸附过程可以通过伪二阶动力模式来描述.根据对lnk2与1/T线形图斜率的计算,可以确定Cr(Ⅵ)和Zn(Ⅱ)的活化能(Ea)分别为22.7 kJ·mol1-和26.88 kJ·mol-1.活化能的计算结果说明,温度的升高能促进黏土材料对Cr(Ⅵ)和zn(Ⅱ)的吸附,同时也表明吸附很可能是一个化学吸附.热力学参数(△H0,△S0,△G0)值可以通过图1gKD与1/T的斜率与截距来计算.热力学参数值的结果表明,天然黏土材料对Cr(Ⅵ)和Zn(Ⅱ)的吸附是吸热反应.