龙游硫铁矿区农田土壤重金属污染的空间变异及在水稻中的积累

Spatial Variation of Eight Heavy Metals in Farmland Soils and Their Accumulation in Rice Grains in Longyou Pyrite Mine, Zhejiang Province

为了解浙江龙游硫铁矿区农田重金属污染状况,采集矿区265件农田土壤样品,分析8种重金属Cu、As、Hg、Zn、Cd、Ni、Pb、Cr元素全量,利用地统计学软件GS+9.0对研究区土壤各元素指标进行半变异函数拟合,并利用普通克里格法进行插值并绘制空间分布图。采集30件水稻籽粒样品,分析重金属在研究区中水稻籽粒的累积特征,并进行了健康风险评价。结果表明:矿区土壤中8种重金属元素的变异系数从0.72到1.76,离散程度较高。8种重金属的土壤空间半变异函数Cu、As、Hg元素符合指数模型,Zn、Cd、Ni、Pb符合球状模型,Cr符合高斯模型。元素Cu、Pb、Zn、Cr、Ni的块金值与基台值的比值C0/C0+C都小于0.25,说明空间变化主要受地质背景等因素影响;元素Cd、Hg和As的块金值与基台值的比值C0/C0+C在0.25~0.75之间,说明除了地质背景因素,人为活动等随机因素也有影响。矿区水稻籽粒中重金属Ni和Cd的变异系数最高,分别为0.95和0.87,说明Ni和Cd元素可能存在异常积累。矿区水稻籽粒对重金属的富集能力由大到小依次为Cd、Zn、Cu、Ni、As、Hg、Cr、Pb。健康风险评价结果表明矿区农田水稻籽粒中元素As、Cd的风险商大于1,存在潜在健康风险;而其他6种重金属Cu、Hg、Zn、Ni、Pb和Cr基本属于安全范围。

To investigate the current state of heavy metal pollution in farmland soils in Longyou Pyrite Mine, Zhejiang Province, 265 farmland soils samples were collected, Cu, As, Hg, Zn, Cd, Ni, Pb and Cr contents in soils were measured and the spatial variation of the heavy metals were studied by using GS＋9.0 and Kriging interpolation. 30 rice grain samples were collected, the accumulation characters and health risk of heavy metals were studied and assessment. The results showed that variation coefficient of eight heavy metals ranged from 0.72 to 1.76, indicating uneven distribution of heavy metals in the study area. The half variant function of Cu, As and Hg fit exponential model, those of Zn, Cd and Ni fit spherical model, that of Cr fit Gaussian model. The C0/C0＋C of Cu, Pb, Zn, Cr and Ni were less than 0.25, indicating their spatial variation were influenced by geological factors, while those of Cd, Hg and As were from 0.25 to 0.75, indicating their spatial variation were influenced by geological and human activity factors. The variation coefficients of Ni and Cd in rice grains were 0.95 and 0.87, respectively, which possibly indicating abnormal accumulation of Ni and Cd. The enrichment capacity was in an order of CdZnCuNiAsHgCrPb. Health risk assessment showed that HQs of As and Cd were higher than 1, suggesting potential risk, while the other six heavy metals were generally safe.