滇东北高原盆地土壤—苹果作物系统硒时空分布及影响因素

Spatio-temporal distribution and influencing factors of selenium in soil-crop system from the plateau basin region,Northeastern Yunnan.

在滇东北典型高原盆地地区以岩石、土壤和农作物(苹果)为主要研究对象,采用元素赋存形态和生物富集系数等研究方法,对土壤Se元素开展持续监测与分析研究,获取高原盆地土壤Se时空变化规律及其影响因素信息.结果表明:昭阳区富硒土壤集中分布于洒渔和旧圃两镇,土壤Se主要为碳酸盐岩、含煤黏土岩、玄武岩和四纪沉积物的岩石继承性富集,碳酸盐岩和黏土岩区同时受表生富集作用影响强烈.不同母质区土壤表现出在不同深度Se活动态比例变化,在20~60cm深度尤为明显.Se生物累积研究结果显示:玄武岩区>含煤黏土岩区>第四系沉积物区≈碳酸盐岩区,Se在盆地复杂母质区显示更高的生物活性,而土壤Se更倾向于向苹果树叶中累积,其次是根系、树枝和果实.对区内土壤多年持续监测结果表明,成土母质、pH值和有机质是影响土壤及作物Se迁移累积的三个主要因素,土壤Se趋向于在pH值在6.05~7.15向作物内迁移.区内土壤Se随时空变化主要受土地耕作方式差异和非自然来源带入的影响,变化主要发生在“高Se”和“边缘Se”区域.非自然Se源的带入同时伴随其他污染物的累积,建议加强源区监测与污染物风险评估.

The temporal and spatial distribution of soil selenium(Se)and its influencing factors in a typical plateau basin area of northeastern Yunnan are investigated by studying the main objects including rocks,soil,and crops(apples).These objects were monitored using the analytical techniques of elemental speciation and bioconcentration coefficient.The result shows that the selenium-enriched soils were concentrated in the towns of Sayu and Jiupu,and selenium in soil was mainly inherited from carbonate rock,coal-bearing clay rock,basalt,and Quaternary sediments.Soils in carbonate rock and clay rock areas were affected simultaneously by supergene enrichment mechanisms,and soils from different parent material areas showed changes in the active proportion of selenium at different depths,especially at the depth of 20~60cm.The degree of selenium bioconcentration satisfied the relation:basalt>coal-bearing clastic rock>Quaternary sedimentary rock>carbonate rock.In the complex parent material section of the basin,Se demonstrated higher biological activity,and soil Se was more likely to accumulate in apple leaves,followed by roots,branches,and fruits.In addition,organic matter,pH,and soil parent material were the three key variables influencing selenium movement and accumulation in soil and crops,and soil Se tended to migrate into crops Particularly at pH 6.05~7.15.The temporal and spatial changes of soil Se in the area were primarily affected by differences in land cultivation methods and the mixing of unnatural sources,and the changes mostly occurred in the"high Se"and"low Se"regions.The appearance of unnatural Se sources was accompanied by the accumulation of other pollutants;therefore,it is recommended to strengthen source monitoring and pollutant risk assessment in these areas.