基于R语言的非点源颗粒态磷指数构建及应用——以丘陵红壤区小流域为例

Identifying the critical sources areas of non-point particulate phosphorus based on an index approach in R:A case study in red soil hilly micro-watershed

以南方丘陵红壤区典型小流域为例,构建了基于R语言的流域非点源颗粒态磷污染指数并进行应用.结果表明,(1)流域土壤侵蚀模数在0.7~15244.2t/(km2·a)之间,超出南方丘陵红壤区容许土壤侵蚀量的区域占流域面积59%;平均非点源颗粒态磷产生强度为0.86kg/hm2,超出非点源磷流失阈值的区域占流域面积14%.流域侵蚀等级以微、轻度为主,但中度及以上强度区域以较小的面积(7.2%)贡献了较大比例的流域侵蚀产生量(35%)和输出量(43%)、以及非点源颗粒态磷输出量(31%).(2)识别的关键源区占流域面积14%,贡献了65%和58%的侵蚀土壤和颗粒态磷输出负荷;主要分布在近河道的坡地(<25°,水文距离≤800m),林地、耕地、园地是主要土地利用类型组成.(3)过量施肥导致的土壤磷素富集、强降雨条件下低丘缓坡地带的高易蚀性是关键源区形成的主因.研究进一步对关键源区进行分类分区,提出了以水土保持、配方施肥、工程治理为核心的非点源颗粒态磷污染治理组合措施.研究为丘陵红壤区流域非点源颗粒态磷污染的防治提供了较为系统完善的思路.

This study developed a watershed-scale non-point source(NPS)particulate phosphorus(PP)index based on R statistical language and applied it in a red soil hilly subbasin.The results indicated that watershed soil erosion rates ranged from 0.7 to 15244.2 t/(km2·a),and 59%of the watershed area exceeded the regional soil erosion threshold.The average watershed NPS PP load was 0.86 kg/hm2 and approximately 14%of the watershed area exceeded the NPS P loss threshold.Despite the fact that dominate soil erosions in the watershed were slight to mild,the small areas(7.2%)categorized as moderate to severe erosions contributed considerably larger shares to the total watershed loads of erosion and NPS PP loss(31%~43%).The critical sources areas(CSAs)for soil erosion and NPS PP loss were identified as 6.4 km2 in area,mainly consisting of wood land,crop land and orchard land,which were adjacent to streams(≤800m)and with low to gentle slopes(<25°).The soil P enrichment due to excessive fertilization,as well as the high erosion potential facilitated the formation of these CSAs.The CSAs were further divided into zones according to land uses,hydrological distances and slopes,on which different management practices and strategies were recommended to target the erosion and NPS PP loss.