Distribution Characteristics of Total Nitrogen and Organic Matter and Its Sources in Core Sediments from the Guangzhou Reach of the Pearl River

The vertical distributions of the Total Nitrogen (TN) and Organic Matter (OM) in the core sediments within 50 cm depth in the Guangzhou Reach of the Pearl River were characterized. In all 6 tested sections, the concentrations of TN ranged from 0.91 to 3.55 g.kg(-1), with an average of 2.11 g.kg(-1) to an abundant level (TN>1.50 g.kg(-1)). And, the concentrations of OM ranged from 4.51 to 79.69 g.kg(-1), with an average of 50.93 g.kg(-1), approximately twice of the average OM concentration of Guangdong soils (26 g.kg(-1)). The TN and OM concentrations in upper layer sediments (0-30 cm) were slightly higher than in lower layer sediments (30-50 cm), but there were not significantly different. These results clearly indicated that the Reach had been heavily polluted by the organic pollutants, and more than 90% samples exceeded the limited OM value (OM < 34 g.kg(-1)) in the sediments. Positive correlation between concentrations of TN and OM (p<0.01) was found as well as water content and OM, TN. Furthermore, the samples had the relatively high ratio of total organic carbon (TOC) to TN (8-33), which indicated potential sources of OM were mostly from terrestrial sources, and partly from aquatic sources.