Journal of Ecology and Rural Environment ›› 2021, Vol. 37 ›› Issue (1): 39-48.doi: 10.19741/j.issn.1673-4831.2020.0168

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Effects of Watershed Characteristics on Dissolved Organic Matter Concentrations in the South Tiaoxi River Watershed

XU Bing-bing   

  1. Shanghai Taihe Water Environment Technology Development Co., Ltd., Shanghai 200433, China
  • Received:2020-03-12 Online:2021-01-25 Published:2021-01-22

Abstract: Dissolved organic matter (DOM) is an important component of carbon, nitrogen and phosphorus cycle in aquatic ecosystems, and the study of regulatory mechanisms of riverine DOM export by watershed characteristics will help to strengthen our understanding of the biogeochemical behavior of DOM transport through rivers to downstream water bodies, and provide a basis for improving eutrophication and ecological restoration of rivers and their downstream water bodies. To examine the spatial and temporal variation of DOM concentrations and its influence factors controlled by watershed characteristics, nearly one year's field surveys were carried out in 16 sub-catchments of South Tiaoxi River. The concentrations of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), dissolved organic phosphorus (DOP) were measured and ten watershed characteristic factors, such as water temperature, discharge, area, gradient, elevation, percentage of five land use types (natural forest, Phyllostachys praecox forest, farmland, town and water body) in each sub-watershed area were extracted. The results showed that the concentrations of DOC and DOP increased from upstream to downstream, which were consistent with the variations of land use pattern and contamination status. DON concentrations were highest in subcatchments dominated with planted forest land (Phyllostachys praecox, a bamboo species) and increased with an intensive proportion of planted forest land. DOP concentrations were lower in summer and autumn than in spring and winter, which could be attributed to the uptake of phosphorus by aquatic organism. Principal component analysis (PCA) revealed that the landscape characteristics (such as land use patterns, gradient) had a stronger influence on DOM concentrations than hydrological regime (discharge, water temperature). DOM concentrations were lower in subcatchments by natural forest land than in subcatchments by other land uses (i. e., planted forest land, cropland, and residential land), indicating that human activities could cause an increase in DOM concentration. The results of multiple regression analysis showed that the proportion of urban area is the best predictor of DOM concentration, and although urban areas are small (average area is about 5%) and scattered, they are an important source of DOM in the watershed.

Key words: watershed characteristics, land use, dissolved organic carbon, dissolved organic nitrogen, dissolved organic phosphorus, South Tiaoxi River

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