Identification and quantification of lead source in sediment in the northern East China Sea using stable lead isotopes

Stable Pb isotopes in surface and core sediments were determined to identify the sources of Pb contaminants in the northern East China Sea(ECS).The Bayesian stable isotope mixing model was used to quantify the contributions of Pb sources.The results show that since the late 1980 s,ratios of^(207)Pb/^(206)Pb and^(208)Pb/^(206)Pb increased in the top 34-cm sediment shown in the coastal core samples,reflecting elevated anthropogenic Pb input in coastal sea.Seaward increase of^(207)Pb/^(206)Pb and^(208)Pb/^(206)Pb ratios in surface sediments reveals that anthropogenic Pb came mainly via atmospheric transmission into the ECS.Anthropogenic sources accounted for 12.0%-21.1%of the total Pb in sediments after the 1990 s.Coal combustion was the largest anthropogenic contributor(47.5%±18.8%),and Pb mining and smelting,cement production,and vehicle exhaust/gasoline contributed 23.2%±7.1%,19.0%±13.0%,and 10.3%±6.9%,respectively.The proportions of the anthropogenic sources gradually increased while geogenic source(riverine sediment)decreased from the coast to the outer shelf.This study demonstrated that the significant influence of atmospheric input of Pb contaminants into the ECS,and also the urgent need to control coal combustion and Pb discharge from industrial dust and fume emission in China.It also highlights the promising application of the Simmr model to quantify the proportions of multiple sources of trace elements in an environment.

Progress on the Use of Stable Isotope Techniques in Catchment Hydrograph Separation: A Review

Hydrograph separation is a fundamental catchment descriptor,revealing information about sources of water in runoff generation processes. The water isotopes are ideal tracers in studying hydrological processes since the isotope fractionation produces a natural labeling effect within the hydrologic cycle. The water isotope technique has become one of effective means for investigating complex hydrologic system on a catchment scale. This paper reviews the progress on the use of stable water isotope techniques in catchment hydrograph separation in last decades. Also,the isotope mixing model for hydrograph separation and its uncertainties are explained in detail. In future research,there are three hot issues in the use of isotopic hydrograph separation（ IHS） ： integrating new approaches into IHS,calibration and verification of IHS model and IHS application in large river basins.

Nile tilapia(Oreochromis niloticus)invasion impacts trophic position and resource use of commercially harvested piscivorous fishes in a large subtropical river

Background Although freshwater ecosystems cover less than 1%of the earth’s surface,they support extremely high levels of biodiversity and provide vital ecosystem services.However,due to the introduction of non-native fishes,aquatic ecosystem functioning has been altered,and in some cases,declined sharply.Quantifying the impacts of invasive species has proven problematic.In this study,we examined the relative trophic position of native piscivorous fishes to estimate the effects of invasive Nile tilapia on food webs in the downstream sections of an invaded large subtropical river,the Pearl River,China.Furthermore,we quantified how native piscivorous fish diets changed as the Nile tilapia invasion progressed.Results The trophic position of the widely distributed and locally important economically harvested piscivorous culter fish(Culter recurviceps),mandarinfish(Siniperca kneri),and catfish(Pelteobagrus fulvidraco)lowered significantly in the invaded Dongjiang River compared to an uninvaded reference Beijiang River.The lower trophic position of these piscivorous fishes was reflected by a major reduction in the proportion of prey fish biomass in their diets following the Nile tilapia invasion.Small fishes in the diet of culter fish from the reference river(33%small fishes,17%zooplankton)shifted to lower trophic level zooplankton prey in the invaded river(36%zooplankton,25%small fish),possibly due to the presence of Nile tilapia.Additionally,small fishes in the diet of mandarinfish in the reference river(46%small fishes,11%aquatic insects)declined in the invaded river(20%aquatic insects,30%small fishes).Similarly,the diet of catfish from the reference river shifted from fish eggs(25%fish eggs,25%aquatic insects)to aquatic insects in the invaded river(44%aquatic insects,5%fish eggs).Conclusions The results of this study contributed to a growing body of evidence,suggesting that Nile tilapia can modify trophic interactions in invaded ecosystems.It is crucial to understand the processes outlined in this study in order to better assess non-native aquatic species,conserve the stability of freshwater ecosystems,and improve current conservation strategies in reaches of the Pearl River and other similar rivers that have experienced invasions of non-native species.