流域特征对南苕溪溶解有机质浓度的影响

doi:10.19741/j.issn.1673-4831.2020.0168

摘要/Abstract

摘要： 溶解有机质（DOM）是水域生态系统中碳、氮、磷循环的重要组成部分，开展流域尺度上流域特征对河流DOM输出的调控机制研究，有助于加深对DOM经由河流向下游水体迁移的生物地球化学行为的认识，为改善河流及其下游水体富营养化状况和进行生态修复提供依据。选取南苕溪流域为研究对象，在其16个子流域开展近一年的采样调研，提取各子流域水温、流量、面积、平均坡度、平均高程以及5种土地利用类型〔天然林、经济林（雷竹林）、农田、城镇、水域〕面积占流域面积比例共10个流域特征变量，同时测定溶解有机碳（DOC）、溶解有机氮（DON）和溶解有机磷（DOP）浓度，分析DOM浓度的空间分布及季节动态，并结合多元分析方法，探讨流域特征对DOM浓度的影响机制。结果表明，DOC、DOP浓度呈由上游河源到下游河口递增的趋势，与流域内土地利用格局及相应的污染梯度变化一致。DON浓度受到流域内雷竹林集约经营活动的影响，就空间而言，在用地类型以雷竹林为主的子流域，DON浓度最高；就季节而言，春季DON浓度最高。夏、秋季DOP浓度小于春、冬季，此与水生生物对水中磷素吸收作用有关。主成分分析结果表明，流域地形地貌特征（土地利用类型、坡度等）对DOM浓度的影响要强于河流水文状况（流量、温度）。在主成分样点得分图中，以天然林为主的子流域与其他受人为影响的子流域（经济林、农田、城镇）分开分布，表明人为活动会引起DOM浓度的增加。多元回归分析结果表明，城镇用地占比是DOM浓度的最优预测变量，虽然城镇面积小（平均面积占比约为5%）、分布散，但却是流域内DOM重要的"源"。

关键词: 流域特征, 土地利用, 溶解有机碳, 溶解有机氮, 溶解有机磷, 南苕溪

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

中图分类号:

X522
X835

徐兵兵. 流域特征对南苕溪溶解有机质浓度的影响[J]. 生态与农村环境学报, 2021, 37(1): 39-48.

XU Bing-bing. Effects of Watershed Characteristics on Dissolved Organic Matter Concentrations in the South Tiaoxi River Watershed[J]. Journal of Ecology and Rural Environment, 2021, 37(1): 39-48.

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