芦溪流域非点源污染物流失的一般规律

以芦溪小流域为研究对象,监测在自然降雨条件下,不同土地利用类型小区、流域出口的污染物流失情况,研究一次降雨径流过程中非点源污染物流失的一般规律,以及不同前期降雨条件下的污染物流失特征.研究表明:随着前期降雨量的增大,SS的流失明显降低,当试验前5天总降雨量为15、115、161mm时,流域出口的SS流失浓度分别为265.6、145.8和124.2mg/L;流域出口的营养物质与COD受前期降雨条件的影响相对较小,波动幅度不大于±15%.小区试验的结果表明:污染物流失浓度的一般规律为:旱地>居民点>草地>林地>水田.植被覆盖可有效地减少泥沙流失,当植被盖度从50%上升到90%时,泥沙流失浓度可减少80%.土壤背景值是决定TN流失浓度的关键因子,旱地、草地、林地的TN流失浓度与土壤背景值的比值为2.75%、2.79%和2.42%.NO₃^--N与NH₄⁺-N的流失浓度随植被盖度的增大而增大.

Regular Pattern of Non-Point Source Pollutants Losses in Luxi Watershed

The losses of non-point pollutant combined with natural rainfall events were monitored at outlets of Luxi watershed and several field plots with different land use. The paper probes characteristics of the sediment and chemical losses during a single rainfall-runoff process. The impact of preceding precipitation is also discussed. The results of field experiments show that the concentration of SS in runoff dropped off obviously with the increase of antecedent rainfall. The observed data were 265.6, 145.8, 124.2mg/L respectively with precipitation of 15, 115, 161 mm in preceding 5 days. Compared to the losses of SS, nutrients and COD were not changed greatly by the preceding rainfalls. The fluctuations of pollutant concentration were less than 15%. The results from plots suggested that land use play an important role in pollutant losses. The following is the list ordered according to concentration of pollutant in runoff, from the highest to the lowest: Dry land,residential area,grassland,woodland and paddy land.Vegetation cover is effective on the reduction of soil erosion and sediment loss.About 80% SS could be cut down when the coverage changed from 50% to 90%.Losses of TN were mainly determined by the TN concentration in soil.The ratios of TN concentration in runoff to that in soil were 2.75%,2.79%,2.42% respectively for the land use of dry land,grassland and woodland.Augment of vegetation overage contributed to increment of N losses,including NO₃^--N and NH₄⁺-N.