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Abstract This paper analyzed the environment significance and hydrochemical characteristics of the main ions on the supra-permafrost water from the view of space-time and different ablations. The study is conducted through collected 330 samples from June to September in 2016 and 2017 in the Source Region of the Yangtze River (SRYR). The results showed the pattern of ionic dominance based on mean value was following as: Cl− > Na+ > SO 4 2− > Ca2+ > Mg2+ > K+ > NO 3 − > NO 2 − > NH 4 + > F− > Li+. Cl− alone contributed 40.57%, and Cl−, Na+, SO 4 2− and Ca2+ accounted for 94.06% of the total ionic concentrations. The spatial variation of ionic concentration was larger at the initial stage of ablation, and more stable in strong ablation and the end of the ablation stage. The area with elevation of 4500 m was the region where the control source of ions was more sensitive to the hydrochemical characteristics of supra-permafrost water in the study area. Through the analysis of the sources of ions, the anions and cations in supra-permafrost water in the study area were mainly controlled by crustal sources including evaporates rocks and carbonate rocks. The recharge effect of precipitation and snow-melt water only affected the concentration of Cl−, NH 4 +, NO 3 −, F−, Li+ and K+, but did not affect NO 2 −, SO 4 2−, Mg2+ and Ca2+. The hydrochemical type of supra-permafrost water was Ca2+-SO 4 2− in high elevation (>4800 m). However, the hydrochemical type of middle elevation (from 4400 m to 4700 m) was Na+-Cl−. The type of hydrochemistry at low altitude was more complex than at high and middle elevation. This study provides insights on the construction of hydrological models in the cold regions and scientific basis for water resources management in the Tibet Plateaus. Graphical abstract The area with elevation of 4500 m was the region where the control source of ions was more sensitive to the hydrochemical characteristics of supra-permafrost water in the study area. The anions and cations in supra-permafrost water in the study area were mainly controlled by crustal sources including evaporates rocks and carbonate rocks. The recharge effect of precipitation and snow-melt water only affected the concentration of Cl−, NH 4 +, NO 3 −, F−, Li+ and K+, but did not affect NO 2 −, SO 4 2−, Mg2+ and Ca2+. The hydrochemical type of supra-permafrost water was Ca2+-SO 4 2− in high elevation (>4800 m). However, the hydrochemical type of middle elevation (from 4400 m to 4700 m) was Na+-Cl−. The type of hydrochemistry at low altitude was more complex than at high and middle elevation. Unlabelled Image Highlights • The supra-permafrost water is the most widely distributed groundwater type in study area; • The area with elevation of 4500 m was more sensitive to the hydrochemical characteristics of supra-permafrost water; • The recharge effect of precipitation and snow-melt water only affected the concentration of Cl−, NH 4 +, NO 3 −, F−, Li+ and K+. [ABSTRACT FROM AUTHOR]

This paper presents the first attempt to investigate the emission source control of the Middle Reaches of Yangtze River Urban Agglomerations (MRYRUA), one of the national urban agglomerations in China. An emission inventory of the MRYRUA was developed as inputs to the CAMx model based on county-level activity data obtained by full-coverage investigation and source-based spatial surrogates. A classification technology method for priority control of atmospheric emission sources was introduced and applied in the MRYRUA for the evaluation of the emission sources control on the region-scale and city-scale, respectively. The results demonstrated that the emission sources in the Hefei-centered urban agglomerations contributed the biggest on the mean PM 2.5 concentrations of the MRYRUA and should be taken the priority to control. The emission sources in the Ma'anshan city, Xiangtan city, Hefei city and Wuhan city were the bigger contributors on the mean PM 2.5 concentrations of the MRYRUA among the cities and should be taken the priority to control. In generally, emission sources in cities along the Yangtze River and the tributary should be given the special attention for the regional air quality target attainments. This study can give an understanding of Chinese emissions and provide a valuable preference to policy makers for finding effective mitigation measures and control strategies for reducing national and regional air pollution in China. [ABSTRACT FROM AUTHOR]

Under the background of global warming, occurrence of heat waves has increased in most part of Europe, Asia and Australia along with enhanced ozone level. In this paper, observational air temperature and surface ozone in the Yangtze River Delta (YRD) region of China during summer of 2013, and the regional chemistry-climate model (RegCM-CHEM4) were applied to explore the relationship between heat wave and elevated ground-level ozone. Observations indicated that YRD experienced severe heat waves with maximum temperature up to 41.1 °C, 6.1 °C higher than the definition of heat wave in China, and can last for as long as 27 days. Maximum ozone reached 160.5 ppb, exceeding the national air quality standard (secondary level) as 74.7 ppb. Moreover, ozone was found to increase at a rate of 4–5 ppb K − 1 within the temperature range of 28–38 °C, but decrease by a rate of − 1.3 ~ − 1.7 ppb K − 1 under extremely high temperature. A typical heat wave case (HW: 24/7–31/7) and non-heat wave case (NHW: 5/6–12/6) were selected to investigate the mechanism between heavy ozone and heat waves. It was found that chemical reactions play the most important role in ozone formation during HW days, which result in 12 ppb ozone enhancement compared to NHW days. Chemical formation of ozone can be influenced by several factors. During heat waves, a more stagnant condition, controlled by anti-cyclone with sink airflow, led to less water vapor in YRD from south and contributed to less cloud cover, which favored a strong solar radiation environment and ozone significantly increasing. High temperature also slightly promote the effect of vertical turbulence and horizontal advection, which beneficial to ozone remove, but the magnitude is much smaller than chemical effect. Our study suggests that the chemical reaction will potentially lead to substantial elevated ozone in a warmer climate, which should be taken into account in future ozone related issues. [ABSTRACT FROM AUTHOR]

Unplanned indirect (de facto) wastewater reuse occurs when wastewater is discharged into surface waters upstream of potable drinking water treatment plant intakes. This paper aims to predict percentages and trends of de facto reuse throughout the Yangtze River watershed in order to understand the relative contribution of wastewater discharges into the river and its tributaries towards averting water scarcity concerns. The Yangtze River is the third longest in the world and supports more than 1/15 of the world's population, yet the importance of wastewater on the river remains ill-defined. Municipal wastewater produced in the Yangtze River Basin increased by 41% between 1998 and 2014, from 2580 m 3 /s to 3646 m 3 /s. Under low flow conditions in the Yangtze River near Shanghai, treated wastewater contributions to river flows increased from 8% in 1998 to 14% in 2014. The highest levels of de facto reuse appeared along a major tributary (Han River) of the Yangtze River, where de facto reuse can exceed 20%. While this initial analysis of de facto reuse used water supply and wastewater data from 110 cities in the basin and 11 gauging stations with > 50 years of historic streamflow data, the outcome was limited by the lack of gauging stations at more locations (i.e., data had to be predicted using digital elevation mapping) and lack of precise geospatial location of drinking water intakes or wastewater discharges. This limited the predictive capability of the model relative to larger datasets available in other countries (e.g., USA). This assessment is the first analysis of de facto wastewater reuse in the Yangtze River Basin. It will help identify sections of the river at higher risk for wastewater-related pollutants due to presence of—and reliance on—wastewater discharge that could be the focus of field studies and model predictions of higher spatial and temporal resolution. [ABSTRACT FROM AUTHOR]

This paper compares the distributions of dissolved and particulate forms of Mn, Fe, Ni, Cu, Zn, Cd, and Pb in the estuaries of the largest rivers in East Asia: the Amur River and the Changjiang (Yangtze River). High suspended solid concentrations, elevated pH, and relatively low dissolved trace metal concentrations are characteristics of the Changjiang. Elevated dissolved Fe and Mn concentrations, neutral pH, and relatively low suspended solid concentrations are characteristics of the Amur River. The transfer of dissolved Fe to suspended forms is typical in the Amur River estuary, though Cd and Mn tend to mobilize to solution, and Cu and Ni are diluted in the estuarine system. Metal concentrations in suspended matter in the Amur River estuary are controlled by the ratio of terrigenous riverine material, enriched in Al and Fe, and marine biogenic particles, enriched in Cu, Mn, Cd, and in some cases Ni. The increase in dissolved forms of Mn, Fe, Ni, Cu, Cd, and Pb compared with river end-member is unique to the Changjiang estuary. Particle–solution interactions are not reflected in bulk suspended-solid metal concentrations in the Changjiang estuary due to the dominance of particulate forms of these metals. Cd is an exception in the Changjiang estuary, where the increase in dissolved Cd is of comparable magnitude to the decrease in particulate Cd. Despite runoff in the Amur River being lower than that in the Changjiang, the fluxes of dissolved Mn, Zn and Fe in the Amur River exceed those in the Changjiang. Dissolved Ni, and Cd fluxes are near equal in both estuaries, but dissolved Cu is lower in the Amur River estuary. The hydrological and physico-chemical river characteristics are dominated at the assessment of river influence on the adjoining coastal sea areas despite differences in estuarine processes. [ABSTRACT FROM AUTHOR]

Abstract: Traditional measurements of suspended sediment concentrations (SSC) through in-situ sampling in rivers are expensive and time-consuming to perform. Thus, these methods cannot provide continuous SSC records. Although remote sensing has been used for SSC estimation, little research has been undertaken on inland rivers, especially for highly turbid rivers like the Yangtze. Previous studies have proposed Landsat TM/ETM+ Band 4 as a spectral SSC indicator for the Yangtze, but its limitation on temporal resolution is insufficient for the study of dynamic changes of sediment. This paper presents a method of estimating SSC of the Yangtze at Jiujiang using time-series satellite data of high temporal resolution Terra MODIS. It was found that differences in water reflectance between Band 2 and Band 5 could provide relatively accurate SSC estimation even when in-situ atmospheric conditions were unknown. After cross-validation, mean absolute relative error (ARE) and relative root mean square error (RRMSE) were relatively low (i.e., 25.5% and 36.5%, respectively). This empirical relationship was successfully applied to the estimation of SSC at Datong in the Lower Yangtze River, although the SSC values were generally underestimated. This study suggests that Terra MODIS could be used to estimate SSC in large turbid rivers, although some influencing factors require further study to improve the accuracy of SSC estimation. [Copyright &y& Elsevier]