Spatial distribution of trace elements associated with organic carbon along the Beiyun River basin,Beijing,China

Pollution resulting from terrestrial and aquatic trace elements has become a severe problem across the world.Organic carbon (OC) content has a high affinity for metallic contaminants and it acts as a sig-nificant sink for trace elements.The decomposition of OC content directly influences the bioavailability of trace elements.The decomposition of OC content and OC distribution vary spatially,these processes affect the release of trace elements and need further research.In the current study,sediment samples from the surface sediment along Beiyun River (Section 1 to Section 4 from upper to lower reaches),which is situated in the rapidly urbanized Beijing metropolis,were measured for OC,moisture,hardness,and trace elements.The OC contents were found to have a substantial difference among all four river sections along the urbanized river gradient.Whereas the higher OC contents were found in Sections 2(Urbanized uplands) and 3 (farmland) compared to those in Sections 1 (forest) and 4 (farmland and part of constructed areas).On the other hand,the highest value of the correlation coefficient was found among the different values of trace elements and OC content in the riverine zone of the Beiyun River basin.OC contents play a vital role in the transformation and origin of trace elements in the surface sediment of the Beiyun River basin.The One-way Analysis of Variance (ANOVA) was applied to compare the means of OC and trace elements at different sections indicating no significant difference.However,source identification of trace elements indicated that a geogenic source was responsible for higher contents of As and (69.95％).Simultaneously,the natural OC,agricultural activities,and industrial waste contributed about (21.10％) towards the Cd and Zn,and about 10％ for Cr and Cu.The current study concludes that the absolute principle component analysis multiple linear regression (APCA-MLR)method can be successfully used to investigate the trace elements (Zn,Ni,Pb,Mn,Cd,Cu,and As) in-teractions through OC content resulting in determination of the various sources of contamination to cause negative environmental impacts on the ecosystem and human health.So,the current study provides a baseline for a quantitative evaluation of trace elements under different sediment of OC contents.