摘要
土壤重金属空间分布与污染状况对山地生态系统安全和人体健康具有重要意义。热带山地是生物多样性的中心和动植物的主要避难所,但它的重金属污染情况却鲜有研究。本文以非洲第一高峰乞力马扎罗山为研究对象,采集703~4512 m海拔范围内共12个海拔高度的132个表层土壤,测定As、Sb、Cr、Mn、Ni和Cu等14种重金属,采用相关性分析、主成分分析、潜在生态风险指数等方法对重金属进行源解析和生态风险评价。结果表明,Cr、Mn、Fe、Ni、Cu等10种重金属含量高于中国、美国和亚撒哈拉地区土壤背景浓度均值,其中Fe含量最高,均值高达72915.56 mg/kg;Tl含量最低,为0.09 mg/kg。据坦桑尼亚共和国《环境管理条例》土壤质量标准,As、Cr、Mn、Mo、Ni和Zn等6种重金属呈现污染状态,其中As污染最为普遍,88.64%的土壤样点呈污染状态。整体上,重金属呈现显著的垂向分布模式(P<0.05,Cd除外),其中As、Sb、Mo、Tl和Pb随海拔升高呈驼峰型分布,Cr随海拔梯度线性降低,而V、Mn、Fe等7种重金属呈U型分布。重金属与气候因子(温度、降水)显著相关,含量分布特征还受到土壤理化性质(例如pH和总有机碳等)调控。主成分分析表明,包括母岩和大气沉降等在内的自然过程与人类活动的混合源为重金属最主要来源,其次为农业源。综合潜在生态风险指数(RI)均值为71.69,总体上属于低生态风险;但是,小于2000 m的低海拔区域,RI最高可达330.36,其中Ni和Cu存在中等以上生态风险,污染样点占比分别为25.2%和15.3%,归因于种植和放牧等农业活动导致的重金属额外输入。研究结果可为热带山地重金属污染控制提供数据支撑。
Exploring the spatial distribution and pollution of soil heavy metals was important for soil ecosystem security and human health.Tropical mountains are centers of biodiversity and major refuges for animals and plants,while heavy metals has been little studied in tropical alpine soils.In this study,we sampled 132 surface soil samples at 12 elevations from Mount.Kilimanjaro,Africa,and measured the contents of 14 heavy metals such as V,Cr,Mn,etc.Correlation analysis,principal components analysis(PCA)and potential ecological risk index(RI)were used for source identification and ecological risk assessment.The results showed that contents of 10 heavy metals such as V,Cr,Mn and Fe were higher than the average of the background concentrations in soils of China,America and sub-Saharan Africa.Six heavy metals including As,Cr,Mn,Mo,Ni and Zn did not meet the soil quality standards of Environmental Management Regulations issued by the Repulic of Tanzania,with As being the widest pollution found in 88.64%samples.Almost all heavy metals showed significant elevational patterns(P<0.05,except Cd).For instance,As,Sb,Mo,Tl and Pb showed hump-shaped elevational patterns,with a decreasing pattern for Cr and a U-shaped pattern for other seven heavy metals with increasing elevation.Correlation analysis showed that contents of soil metal were significantly correlated with the effects of climatic factors such as temperature and precipitation.The bioavailability of metals was significantly regulated by soil physicochemical properties such as pH and total organic carbon.Principal component analysis showed that a mixture of agricultural sources and natural sources including soil parent materials and atmospheric deposition was the most dominant source,followed by agricultural source.The mean of RI was 71.69 and showed a low ecological risk situation for study area.However,the maximum RI of the area below 2,000 m was 330.36,where Ni and Cu showed a medium-high ecological risk situation,and the proportion of Ni and Cu contaminated samples were 25.2%and 15.3%,respectively.These were mainly due to the additional inputs of heavy metals attributed to agricultural activities such as cultivation and grazing.The results provided scientific basis for heavy metal pollution control in tropical alpine soils.The regulation of agricultural activities is needed to be strengthen in the future.
作者
徐佳宁
张路
杨飞
许妍
王建军
XU Jianing;ZHANG Lu;YANG Fei;XU Yan;WANG Jianjun(School of Civil Engineering,Southeast University,Nanjing 211189,China;Key Laboratory of Lake and Watershed Science for Water Security,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences,Nanjing 210008,China;State Key Laboratory of Soil and Sustainable Agriculture,Institute of Soil Science,Chinese Academy of Sciences,Nanjing 211135,China)
出处
《地球与环境》
北大核心
2025年第3期353-364,共12页
Earth and Environment
基金
国家自然科学基金项目(42225708)
中国科学院中-非联合研究中心(151542KYSB20210007)。
关键词
乞力马扎罗山
垂向分异
重金属
源分析
生态风险
Mount.Kilimanjaro
vertical differentiation
heavy metal
source analysis
ecological risks
