北部湾钦江流域土壤侵蚀及其硒元素流失评估

以钦江流域2015年的气象数据、遥感数据及数字高程模型、土壤类型以及土壤质地等数据为基础，基于修正的通用土壤流失方程（RUSLE）和GIS空间分析技术，定量分析了广西北部湾钦江流域土壤侵蚀及其硒元素流失的空间分布特征.研究结果表明：（1）北部湾钦江流域2015年土壤侵蚀总量为381.64×104t/a，平均土壤侵蚀模数为14.79t/（hm²·a），小于2010年钦江流域的土壤侵蚀模数，但远大于水利部规定的在南方红壤丘陵区土壤允许流失量；（2）流域土壤侵蚀强度以微度侵蚀为主，侵蚀强度从流域上游到下游依次降低，0~240m之间的高程带以及>15°的坡度带是未来土壤侵蚀防治的重点区域；（3）山地地区的土壤侵蚀模数最高，达23.49t/（hm²·a），高于流域平均土壤侵蚀模数约1.59倍，丘陵地区次之，而冲积平原最小；（4）流域土壤的硒含量介于0.38~0.72mg/kg之间，平均值0.49mg/kg，高于中国土壤硒元素背景值的1.69倍；（5）不同土地利用类型土壤硒含量随着土壤剖面深度的增加均呈现出减低趋势，硒的含量在不同土地利用类型中的排序为林地 > 园地 > 草地 > 水田 > 旱地，而在不同土壤类型中硒含量大小顺序则为：新积土 > 石灰岩土 > 潜育水稻土 > 淹育水稻土 > 赤红壤 > 潴育水稻土 > 砖红壤 > 滨海沙土 > 紫色土 > 咸酸水稻土.（6）流域土壤硒元素的流失总量为8987.05kg/a，平均流失模数为0.0344kg/（hm²·a），其中流域中游的硒元素流失量最大.该项研究成果可为钦江市政府开发富硒农产品、发展富硒农业以及提升钦江流域土地利用的价值提供科学依据.

Soil erosion and Selenium loss in Qinjiang River Basin in Beibu Gulf coastal zone

Based on the meteorological data, remote sensing data, digital elevation model, soil types and soil texture data of Qinjiang River basin in 2015, the spatial distribution of soil erosion and associated Se loss in 2015 in Qinjiang River Basin in Beibu Gulf coastal zone, was quantitatively analyzed by using the modified universal soil loss equation (RUSLE) and GIS spatial analysis technology technique. The results indicated that the total amount of soil erosion in Beibu Gulf Qinjiang River Basin in 2015 was 381.64×104t/a, and the average modulus of soil erosion was 14.79t/(hm²·a). The soil erosion modulus of the Qinjiang River Basin was less than that of the 2010, but far greater than that of the Ministry of water resources in the red soil hilly area of the South China. The soil erosion intensity was mainly slight erosion, which decreased successively from upstream to downstream in the basin. The elevation zone between 0~240m and the slope zone belts of greater than 15degrees were the key areas for soil erosion prevention in the future. The highest modulus of soil erosion in mountainous area was 23.49t/(hm²·a), which was about 1.59times higher than the average modulus of soil erosion in watershed, followed by hilly area and the smallest in alluvial plain. The content of selenium in the soil was between 0.38~0.72mg/kg, with the average value of 0.49mg/kg, which was 1.69times higher than the background value of selenium in Chinese. Selenium content in different land use types decreased with the increase of soil profile depth. The order of Se content in different land use types was forest land > garden land > grassland > paddy field > dry land, and the order of Se content in different soil types was:new accumulated soil > limestone soil > gleying paddy soil > flooded paddy soil > dry land. Lateritic red soil > paddy soil soil > lateritic soil > coastal sandy soil > purple soil > salty acid paddy soil. The total loss of selenium Qinjiang River Basin was 8987.05kg/a. The average loss modulus was 0.0344kg/(hm²·a), and the loss of selenium in the middle reaches of the river basin was the largest. The results can provide scientific basis for the development of selenium-rich agricultural products, the development of selenium-rich agriculture and the promotion of land use value in Qinjiang River Basin.