重庆市奉节县中部土壤硒富集特征及来源分析

Analysis of selenium enrichment characteristics and sources in soils of central Fengjie county,Chongqing

近年来,人们对富硒(Se)资源的需求不断提高,土壤作为农作物生长的基础物质,富Se土地开发利用将是提高Se资源合理利用的首要切入点。选取奉节县中部青龙镇和五马镇一带土壤为研究对象,采集247个土壤样品,对研究区Se元素含量、来源、分布和影响因素特征进行分析。结果表明,研究区土壤Se平均含量为0.462mg/kg,变异程度属于高度变异。根据《天然富硒土地划定与标识》(DZ/T 0380—2021)中规定的富Se土地划分标准,研究区内一般富Se点位占比为17.89%,空间位置上具有连续分布的特点。对Se等元素源解析及影响因素分析结果显示,Se元素与Cd等重金属元素具有较强的伴生关系并且来源相对一致。同时,土壤有机质、硫化物、铁氧化物及磷灰石对Se含量影响显著,并指示受到外源迁入的影响。据正定矩阵因子分析模型定量源解析分析,研究区土壤中Se来源影响顺序为外源迁入>地质背景>人为活动,贡献率分别为70.1%、15.2%和14.7%,主要受河流上游地质背景影响,同时伴随着Cd的迁入。综合分析表明,研究区土壤环境有利于Se元素富集并降低重金属安全风险,具有划定天然富Se土地的条件,建议在后续工作中开展专项农作物调查,进一步评估农产品开发利用潜力。

In recent years,people's demand for selenium(Se)rich resources has been increasing.Soil is the basic material for crop growth,Se rich land development and utilization will be the primary entry point to improve the rational use of Se resources.In this paper,247 soil samples were collected from the areas around Qinglong,Wuma townships in the central part of Fengjie county,and the characteristics of Se content,source,distribution and influencing factors in the study area were analyzed.The results showed that the average Se content of soil in the study area was 0.462 mg/kg,and the degree of variation belonged to high variability.According to the criteria for Delimitation and logo of natural selenium-enriched land(DZ/T 0380-2021),the percentage of general Se-enriched sites in the study area was 17.89%,with a continuous distribution in spatial location.The results of the analysis of Se and other elemental sources and influencing factors showed that Se had a strong association with Cd and other heavy metal elements and the sources were relatively consistent.At the same time,soil organic matter,sulfide,iron oxide and apatite had significant effects on Se content,and indicated that they were influenced by the migration of exogenous sources.According to the quantitative source analysis of positive matrix factorization,the influence of Se sources in the soils of the study area was in the order of exogenous migration > geological background > anthropogenic activities,with the contribution rates of 70.1%,15.2% and 14.7%,respectively.It was mainly affected by the geological background of the upstream river and accompanied by the migration of Cd.The comprehensive analysis shows that the soil environment in the study area is conducive to Se enrichment and reduces the safety risk of heavy metals,and has the conditions for delineating natural Se-enriched land,and it is suggested to carry out special crop surveys in the follow-up work to further evaluate the potential of agricultural products exploitation.