State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Water and Soil Erosion Conservation, Northwest A&F University, Yangling, Shaanxi, 712100, Peoples Republic of China,
Environ Sci Pollut Res Int. 2015 Jul;22(14):10647-60. doi: 10.1007/s11356-015-4242-z. Epub 2015 Mar 11.
Chinese Loess Plateau is considered as one of the most serious soil loss regions in the world, its annual sediment output accounts for 90 % of the total sediment loads of the Yellow River, and most of the Loess Plateau has a very typical characteristic of "soil and water flow together", and water flow in this area performs with a high sand content. Serious soil loss results in nitrogen and phosphorus loss of soil. Special processes of water and soil in the Loess Plateau lead to the loss mechanisms of water, sediment, nitrogen, and phosphorus are different from each other, which are greatly different from other areas of China. In this study, the modified export coefficient method considering the rainfall erosivity factor was proposed to simulate and evaluate non-point source (NPS) nitrogen and phosphorus loss load caused by soil and water loss in the Yanhe River basin of the hilly and gully area, Loess Plateau. The results indicate that (1) compared with the traditional export coefficient method, annual differences of NPS total nitrogen (TN) and total phosphorus (TP) load after considering the rainfall erosivity factor are obvious; it is more in line with the general law of NPS pollution formation in a watershed, and it can reflect the annual variability of NPS pollution more accurately. (2) Under the traditional and modified conditions, annual changes of NPS TN and TP load in four counties (districts) took on the similar trends from 1999 to 2008; the load emission intensity not only is closely related to rainfall intensity but also to the regional distribution of land use and other pollution sources. (3) The output structure, source composition, and contribution rate of NPS pollution load under the modified method are basically the same with the traditional method. The average output structure of TN from land use and rural life is about 66.5 and 17.1 %, the TP is about 53.8 and 32.7 %; the maximum source composition of TN (59 %) is farmland; the maximum source composition of TP (38.1 %) is rural life; the maximum contribution rates of TN and TP in Baota district are 36.26 and 39.26 %, respectively. Results may provide data support for NPS pollution prevention and control in the loess hilly and gully region and also provide scientific reference for the protection of ecological environment of the Loess Plateau in northern Shaanxi.
中国黄土高原被认为是世界上水土流失最严重的地区之一，其年输沙量占黄河总输沙量的 90%，而且大部分黄土高原都具有非常典型的“土水一起流”的特征，该地区水流含沙量很高。严重的水土流失导致土壤中的氮磷流失。黄土高原特殊的水土过程导致水、沙、氮、磷流失机制彼此不同，与中国其他地区有很大的不同。本研究提出了考虑降雨侵蚀力因子的修正输出系数法，以模拟和评价黄土高原丘陵沟壑区延河流域水土流失引起的非点源（NPS）氮磷流失负荷。结果表明：（1）与传统的输出系数法相比，考虑降雨侵蚀力因子后，NPS 总氮（TN）和总磷（TP）负荷的年际差异明显，更符合流域内 NPS 污染形成的一般规律，能更准确地反映 NPS 污染的年际变化。（2）在传统和修正条件下，1999 年至 2008 年，四县（区）NPS TN 和 TP 负荷的年际变化趋势相似；负荷排放强度不仅与降雨强度密切相关，还与土地利用等污染源的区域分布密切相关。（3）修正法下 NPS 污染负荷的输出结构、源组成和贡献率与传统法基本相同。TN 中土地利用和农村生活的平均输出结构分别约为 66.5%和 17.1%，TP 分别约为 53.8%和 32.7%；TN 的最大源组成（59%）为农田；TP 的最大源组成（38.1%）为农村生活；最大贡献的 TN 和 TP 分别为 36.26%和 39.26%。研究结果可为黄土丘陵沟壑区 NPS 污染防治提供数据支持，为陕北地区黄土高原生态环境保护提供科学参考。
