Department of Forest Environment Protection, College of Forest & Environmental Sciences, Kangwon National University, Chuncheon 200-701, Republic of Korea.
Environ Sci Technol. 2010 Dec 15;44(24):9324-9. doi: 10.1021/es102109a. Epub 2010 Nov 18.
Although atmospheric Pb is known to accumulate in forest soils over time, little is known about the hydrologic Pb export from mountain forest soils. Short-term changes in Pb release and its sources during monsoon rainfall events were investigated in a mountainous watershed in the northern extreme of South Korea by combining intensive storm sampling with measurements of Pb concentrations and isotope ratios in soils and size-fractionated sediments. Biweekly monitoring of forest and agricultural streams showed relatively low dissolved Pb concentrations compared to those found in precipitation. Particulate Pb concentrations in both streams were higher than the dissolved concentrations and increased rapidly during rainfall events. Particulate Pb concentrations were substantially higher in the agricultural stream; the highest concentrations were associated with silt-size sediment followed by sand. A comparison of (206)Pb/(207)Pb and (208)Pb/(206)Pb among sediment fractions and source soils indicated that major sources for silt- and sand-associated Pb in the agricultural stream change between streambank and cropland soils, whereas Pb in the forest stream is primarily derived from forest floors. The results suggest that Pb isotopes can be efficiently applied to tracing short-term changes in sediment and Pb sources and that extreme rainfall events can significantly increase Pb mobilization from erosion-prone mountain soils.
尽管大气中的 Pb 随着时间的推移会在森林土壤中积累，但人们对山地森林土壤中 Pb 的水文输出知之甚少。本研究通过在韩国最北部的山区流域进行密集的风暴采样，并测量土壤和不同粒径沉积物中 Pb 浓度和同位素比值，研究了季风降雨事件中 Pb 释放及其来源的短期变化。两周一次的森林和农业溪流监测显示，溶解态 Pb 浓度相对较低，低于降水。两种溪流中的颗粒态 Pb 浓度均高于溶解态浓度，且在降雨事件中迅速增加。农业溪流中的颗粒态 Pb 浓度显著更高；最高浓度与粉砂粒径沉积物有关，其次是砂。对沉积物各粒级和源土壤之间的 (206)Pb/(207)Pb 和 (208)Pb/(206)Pb 进行比较表明，农业溪流中粉砂和砂相关 Pb 的主要来源在溪岸和农田土壤之间发生变化，而森林溪流中的 Pb 主要来自林地。研究结果表明，Pb 同位素可有效地用于追踪沉积物和 Pb 来源的短期变化，且极端降雨事件会显著增加易侵蚀山地土壤中 Pb 的迁移。
