Sources and routes from terrestrial exogenous pollutants affect phytoplankton biomass in reservoir bays

Reservoir bays, the boundary of terrestrial and water where water fluidity slows down and self-purification ability turn weak, hence they are especially sensitive to terrestrial exogenous pollutants, even resulting in eutrophication. According to N:P, water nutrients types can be divided into N limited, P limited and N + P limited classes. Phytoplankton biomass is represented by chlorophyll a, which is one of the sensitive indicators of water eutrophication. Comprehensively traced non-point pollution from terrestrial exogenous pollutants (fertilizer, soil release, anthropogenic discharge) to water nutrients that happen in reservoir bays is of great significance. This paper identified the dominant environmental variables and nutrients limited types of reservoir bays at storage and discharge periods, constructed partial least squares structural equation model (PLS-SEM) to explore the impacts of terrestrial exogenous pollutants. Results showed that in storage period water contamination mainly came from residential discharge and soil endogenous release, the total contribution rate reached 61%. In discharge period, with the increase of rainfall – runoff erosion, the explanatory ability of land use, topography and landscape pattern to water quality increased, up to 58%. The dominant nutrients limited types of reservoir bays were P limited (35%–47%) and N + P limited (35%–59%) at both stages, N limited situations less than 20% and generally appeared in storage period. Whatever the nutrients limited type was, phosphorus always had a higher effect on phytoplankton biomass. In N limited situation, nitrogen mainly from soil release (total effect = 0.6) and phosphorus from fertilizer (total effect = 0.22) and soil release (total effect = 0.17). In P limited situation, all three sources had almost high effects on nitrogen, phosphorus, and phytoplankton biomass. In N + P limited situation, the anthropogenic discharge was the main source of nutrients and the primary threaten factor for phytoplankton biomass. The approaches employed in this study could be generalized to the other basin and the results were significant to early warning and controlling water eutrophication.

Long-term groundwater recharge rates across India by in situ measurements

Groundwater recharge sustains groundwater discharge, including natural discharge through springs and the base flow to surface water as well as anthropogenic discharge through pumping wells. Here, for the first time, we compute long-term (1996–2015) groundwater recharge rates using data retrieved from several groundwater-level monitoring locations across India (3.3 million km2 area), the most groundwater-stressed region globally. Spatial variations in groundwater recharge rates (basin-wide mean: 17 to 960 mm yr−1) were estimated in the 22 major river basins across India. The extensive plains of the Indus–Ganges–Brahmaputra (IGB) river basins are subjected to prevalence of comparatively higher recharge. This is mainly attributed to occurrence of coarse sediments, higher rainfall, and intensive irrigation-linked groundwater-abstraction inducing recharge by increasing available groundwater storage and return flows. Lower recharge rates (<200 mm yr−1) in most of the central and southern study areas occur in cratonic, crystalline fractured aquifers. Estimated recharge rates have been compared favorably with field-scale recharge estimates (n=52) based on tracer (tritium) injection tests. Results show that precipitation rates do not significantly influence groundwater recharge in most of the river basins across India, indicating human influence in prevailing recharge rates. The spatial variability in recharge rates could provide critical input for policymakers to develop more sustainable groundwater management in India.

Long-term groundwater recharge rates across India by in situ measurements

Groundwater recharge sustains groundwater discharge, including natural discharge through springs and base flow to surface water as well as anthropogenic discharge through pumping wells. Here, for the first time, we compute long-term (1996–2015) groundwater recharge rates using data retrieved from several groundwater level monitoring locations across India (3.3 million km2 area), the most groundwater-stressed region globally. Spatial variations in groundwater recharge rates (basin-wide mean: 17 to 960 mm/yr) were estimated in the 22 major river basins across India. The extensive plains of the Indus–Ganges–Brahmaputra (IGB) river basins are subjected to prevalence of comparatively higher recharge. This is mainly attributed to occurrence of coarse sediments, higher rainfall, and intensive irrigation-linked groundwater abstraction inducing recharge by increasing available groundwater storage and return flows. Lower recharge rates (

Effect of Hg in Jiaozhou Bay Waters - Land Transfer Process

Based on the investigation data of mercury (Hg) in waters in Jiaozhou bay during time peroids of 1979 to 1985 (absent of 1984), this paper tried to analysis the seasonal variations of Hg in Jiaozhou Bay, to reveal the transfer process of Hg, and to provide basis for decision-making of pollution control. Results showed that, there was indistint seasonal variations of Hg content, due to anthropogenic discharge was the major source of Hg, which was not static, but depended on industrial adjustment. The land transfer process of Hg could be divided into three major processes: 1) human discharges of Hg to soil, waters, and atmosphere, etc., 2) Hg is washouted and delivered into streams, and 3) Hg is transferred to ocean via river channel runoff. In order to reconcile economic growth with environmental protection, we should have to improve the use ratio of Hg, and to reduce the discharge load of Hg.