The hidden threat of heavy metal leaching in urban runoff: Investigating the long-term consequences of land use changes on human health risk exposure.

This study evaluated the potential effects of long-term land use and climate change on the quality of surface runoff and the health risks associated with it. The land use change projection 2030 was derived from the main changes in land use from 2009 to 2019, and rainfall data was obtained from the Long Ashton Research Station Weather Generator (LARS-WG) model. The Long-Term Hydrological Impact Assessment (L-THIA) model was then utilized to calculate the rate of runoff heavy metal (HM) pollutant loading from the urban catchment. It was found that areas with heavy development posed a significantly greater public health risk associated with runoff, with higher risks observed in high-development and traffic areas compared to industrial, residential, and commercial areas. Additionally, exposure to Lead (Pb), Mercury (Hg), and Arsenic (As) was found to contribute significantly to overall non-carcinogenic health risks for possible consumers of runoff. Carcinogenic risk values of As, Cadmium (Cd), and Pb were also observed to increase, particularly in high-development and traffic areas, by 2030. This investigation offers important insight into the health risks posed by metals present in surface runoff in urban catchment areas under different land use and climate change scenarios.

Environmental, hydrological, and social impacts of coal and nonmetal minerals mining operations.

Mining and mineral exploration has many effects on the surrounding environment. The present study reviews the hydrological and environmental impacts of coal and nonmetal mining operations by mine lifecycle stages and facility patterns. Further, a critical review of regulations and policies in South Korea focusing on the mining-water interaction, conservation, and management was performed to emphasize the current state of legislation in the country. The counties where mining was the primary employer in Gangwon-do province in South Korea were assessed for the mining impact on the community's social life and com-pared to the non-mining counties in the same province. The results of the comparative study showed the less education, healthcare and employment chances in mining counties than the adjacent counties with no mining activities.

Dynamics of bacterioplankton community structure in response to seasonal hydrological disturbances in Poyang Lake, the largest wetland in China.

Bacterioplankton communities play a critical role in biogeochemical cycling in freshwater environments, but how the hydrological regime impacts the assembly of bacterioplankton communities remains unclear. This study examined differences in bacterioplankton community structures between wet (July and September) and dry (October and November) seasons in two consecutive years (2016 and 2017) in Poyang Lake, the largest seasonal freshwater lake in China. Our results revealed no overall difference in bacterioplankton compositions and their predicted functions among spatially separated sites. However, bacterioplankton communities did show significant temporal shifts, mainly between samples in November and other months. Transitions from the dry to the wet season were observed in October in both sampling years. Meanwhile, insignificant spatial but significant temporal differences were also found for physicochemical variables. Moreover, redundancy analysis indicates that compared with water depth, water temperature was found to better explain changes in the bacterioplankton community. These findings consistently indicate that the bacterioplankton community in Poyang Lake is relatively less sensitive to annual hydrology shifts than water temperature and nutrient conditions.

The impact of the Three Gorges Dam on the fate of metal contaminants across the river-ocean continuum.

The Three Gorges Dam (TGD) is the world's largest hydropower construction. It can significantly impact contaminant transport in the Yangtze River-East China Sea Continuum (YR-ECSC). In addition to evaluating the impact of the TGD on the deposition of contaminants in the reservoir, we also address their cycles in the river below the dam and in the coastal East China Sea. A comprehensive study of metal contaminant transport along the YR-ECSC has not been previously attempted. We quantified the fates of mercury (Hg), arsenic (As), lead (Pb), cadmium (Cd) and chromium (Cr) within the YR-ECSC, and the impacts of the TGD, by sampling water and suspended particles along the Yangtze River during spring, summer, fall, and winter and by modeling. We found that the Yangtze River transports substantial amounts of heavy metals into the coastal ocean. In 2016, riverine transport amounted to 48, 5900, 11,000, 230, and 15,000 megagrams (Mg) for Hg, As, Pb, Cd, and Cr, respectively, while other terrestrial contributions were negligible. Metal flux into the coastal ocean was primarily derived from the downstream portion of the river (84-97%), while metals transported from upstream were largely trapped in the Three Gorges Reservoir (TGR, 72%-96%). For example, 34 Mg of Hg accumulated in the TGR owing to river damming, large-scale soil erosion, and anthropogenic point source releases, while 21 Mg of Hg was depleted from the riverbed downstream owing to the altered river hydrology caused by the TGD. Overall the construction of TGD resulted in a 6.9% net decrease in the Hg burden of the East China Sea, compared to the pre-TGD period.

Distribution and source assessment of polycyclic aromatic hydrocarbons levels from Lake IJssel (the Netherlands) and their responses to hydrology.

Based on field efforts in Lake IJssel (the Netherlands) from 2000 to 2010, dynamics of 15 priority PAHs in suspended particulate matter (SPM) and in seawater were determined. This study examined time-varying changes in PAH concentration and composition, apportioned potential anthropogenic sources, and quantified their linkages to hydrological factors. The sum of individual PAHs (defined as ∑15 PAHs) varied widely throughout the study period in Lake IJssel, ranging from 0.76 to 9.66 mg/kg in SPM and from 0.014 to 0.136 µg/L in seawater. High molecular weight PAHs were the most abundant PAH compounds, responsible for 73%-97%. Seasonal variation in ∑15 PAHs level was distinguished, peaked in late winter and early spring, and reached a minimum in summer. Over site, the heavy contamination was found at the river mouth (e.g., Genemuiden). The driving factors of SPM and water temperature controlled the fate of PAHs. Principal component analysis and diagnostic ratios suggested that PAHs may have been derived from different input sources through various transport pathways, for example, coal combustion source and petroleum source. The findings are useful for filling the knowledge gap of PAH dynamics in Lake IJssel and Wadden Sea, which exerts significant influences on lake's environment. PRACTITIONER POINTS: HMW PAHs (4-6 rings) were the most abundant PAH compounds. Heavy contamination was found in the mouth of IJssel River. Time-varying change in PAHs level was significantly correlated with riverine input. PAHs sources were apportioned via principal component analysis and diagnostic ratios.

Assessing the effectiveness of Sustainable Land Management for large-scale climate change adaptation.

Climate change will strongly affect essential ecosystem services, like the provision of freshwater, food production, soil erosion and flood control. Sustainable Land Management (SLM) practices are increasingly promoted to contribute to climate change mitigation and adaptation, but there is lack of evidence at scales most relevant for policymaking. We evaluated the effectiveness of SLM in a large Mediterranean catchment where climate change is projected to significantly reduce water security. We show that the on-site and off-site impacts of climate change are almost entirely reversed by the large-scale implementation of SLM under moderate climate change conditions, characterized by limited reductions in annual precipitation but significant increased precipitation intensity. Under more extreme reductions of annual precipitation, SLM implementation reduces the impacts on water security, but cannot prevent significant increased plant water stress and reduced water availability. Under these conditions, additional adaptation measures are required considering their interactions and trade-offs regarding water security.

Comparison of baseline period choices for separating climate and land use/land cover change impacts on watershed hydrology using distributed hydrological models.

Separating impacts of land use/land cover change (LUCC) and climate change on hydrology is essential for watershed planning and management. This is typically done via hydrological modelling in combination with the one-factor-at-a-time analysis. However, it remains unclear how large the differences in isolated hydrological impacts would be when selecting different baseline periods. In this study, we compared baseline period choices for separating climate change and LUCC impacts on watershed hydrology in a typical inland river basin in northwest China, i.e. the Upper Heihe River Basin, with two hydrological models, i.e., Soil and Water Assessment Tool and Distributed Hydrology Soil Vegetation Model. In the real LUCC case which considers the actual land use changes between 2000 and 2011, the absolute contributions of LUCC to the variations in water yield and ET are slight and almost have the same magnitude for different baseline period choices, whereas those of climate change are substantial and with varying magnitudes. Compared with the absolute contributions, the relative contributions of climate change and LUCC seem less sensitive to the choices of baseline periods. In the hypothetical LUCC case which assumes an extreme land use conversion (i.e., grassland converts to farmland completely), both climate change and LUCC contribute to the changes in water yield and ET significantly. Moreover, both the absolute and relative contributions diverge noticeably between various baseline period choices. The influences of baseline period choices on the partitioning of hydrological impacts diverge significantly between different hydrological models. This study highlights that baseline period choice is an important source of uncertainty when disentangling the impacts of LUCC and climate change on hydrology. Some useful recommendations regarding baseline period selection have been proposed, which may help to reduce the uncertainties associated with baseline period choices.