Spatial distribution characteristics of carbon, nitrogen and phosphorous and pollution status evaluation of sediments in the Haihe River Basin, China.

Abstract

Studying the distribution of carbon, nitrogen and phosphorus of sediments on a whole-watershed scale is important to the research and management of water resources in the Haihe River Basin (HRB). In this study, total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) of 163 samples were investigated in the HRB. Based on these data, the pollution le-vels of sediments were assessed by using different quantitative indices. The results showed that the concentrations of TOC, TN, and TP in the HRB were heterogeneous at different locations. A decreasing trend of concentrations was found from downstream plains (e.g., the Beisihe River and the Heilonggang River) to mountain areas (e.g., the Yongdinghe River, the Beisanhe River, and the Luanhe River). In addition, the concentration of TOC in river sediments was higher than that of reservoir sediments. The statistical analyses showed that TN was significantly (P<0.01) correlated to TOC and TP, with a correlation coefficient of 0.704 and 0.250, respectively. The pollution level based on organic indices was classified as the clean level in the HRB. However, the areas with a relatively high pollution level were still found in some spots, such as the Beisihe River, and the Heilonggang River. Sediments of rivers and reservoirs were similar in the pollution intensity. The average C/N value of sediments in the HRB was 12.71, indicating that the TOC was derived from algae, phytoplankton flora and fauna, followed by higher plants. The C/N value of reservoir sediments was higher than that of river sediments, indicating that the contribution of terrigenous material inputs to TOC was larger in reservoirs than in rivers.