Influence of hydro-geomorphology, land-use and riparian zone characteristics on herbicide occurrence and distribution in sediments in Songhua River Basin, northeastern China

The Songhua River Basin, the third biggest basin in China, is one of the most important commodity grain bases in China. Agricultural nonpoint source pollution has been listed as one of the leading sources of pollution in rivers and streams in this basin. We examined the residues of herbicides including atrazine and acetochlor in riparian soils and sediment samples from 248 stations throughout this basin, collected from June to August in 2010 before the rainy season. The influence of three aspects was compared using statistical analysis to identify key factors that affected transport of herbicides in such large‐scale basin, including sediment nutrient components (TOC, TN and TP), hydro-geomorphologic variables (slope and annual average runoff depth) and land-use variables (area ratio and edge density of each land use type) in watershed and riparian zones. The results of correlation and factor analysis suggested that agricultural land-use characters and herbicide residues in riparian zones, vegetated buffer setting of watershed and riparian zones, sediment nutrients and hydro-geomorphologic factors were the main factors affecting transport of acetochlor. The main factor for occurrence and distribution of the herbicides in sediment was the interactions between chemistry, hydrology, and land-use. Moreover, the result of the multivariate linear regression indicated that the former two factors were the most important influencing factors. However, the impact factors of atrazine residues in sediments did not agree with those of acetochlor. TOC was the only variable that appeared to have an influence on atrazine residues in sediments. The current study showed serious herbicide pollution and vulnerability in pesticide pollution control of Songhua River Basin. Based on the results, best management practice was suggested to solve this problem.