环境科学  2025, Vol. 46 Issue (1): 442-452   PDF    
单县表层土壤重金属污染特征、健康风险及溯源解析
赵庆令1,2,3, 李清彩1,2,3, 马龙1,2, 贾琛1,2, 陈娟1,2     
1. 山东省鲁南地质工程勘察院(山东省地质矿产勘查开发局第二地质大队), 济宁 272100;
2. 自然资源部采煤沉陷区综合治理与生态修复工程技术创新中心, 济宁 272100;
3. 山东农业大学资源与环境学院, 泰安 271018
摘要: 掌握土壤重金属污染风险特征及定量解析潜在来源, 对精准防控、科学管理与安全利用土壤资源具有重要意义.以单县表层土壤为研究对象, 采集并测定了330件表层土壤样品As、Cd、Cr、Cu、Hg、Ni、Pb和Zn等8种重金属含量, 借助地累积指数和富集指数评价了重金属污染程度, 利用生态环境部指定的健康风险模型评价了重金属所产生的致癌风险和非致癌风险, 运用绝对主成分得分-多元线性回归模型(APCS-MLR)定量解析了表层土壤中重金属的来源.结果表明, 单县表层土壤样品中8种重金属的平均值均低于菏泽市表层土壤背景值和国家农用地土壤污染风险筛选值, Hg含量的变异系数达40.26%, 其他7种元素含量的变异系数均低于15.2%;经Igeo和EF评价, 仅Hg元素约5%的样点为轻微污染, 其他7种重金属均为无污染或轻微污染状态;表层土壤中As对成人及儿童的致癌风险和非致癌风险为可耐受水平, 其他7种重金属对成人及儿童的致癌风险和非致癌风险均可忽略;表层土壤中Cd、Cu、Zn、Ni和As的主要物质来源为自然背景源, Cr和Hg的主要物质来源分别为农业养殖源和工业燃煤源, Pb的主要污染来源包括其他未知源和自然背景源, 自然背景源、农业养殖源、工业燃煤源和其他未知源平均贡献率分别为51.69%、27.18%、6.83%和14.31%, 说明单县表层土壤中重金属来源主要为自然背景源, 其次为农业养殖源.
关键词: 重金属(HMs)      地累积指数      富集指数      健康风险      源解析     
Characteristics, Health Risks, and Source Analysis of Heavy Metal Pollution in Surface Soil in Shanxian County
ZHAO Qing-ling1,2,3 , LI Qing-cai1,2,3 , MA Long1,2 , JIA Chen1,2 , CHEN Juan1,2     
1. Lunan Geo-engineering Exploration Institute of Shandong Province (Shandong Provincial Bureau of Geology and Mineral Resources No.2 Geology Group), Jining 272100, China;
2. Technology Innovation Center of Integrated Management and Ecological Restoration for Mining Subsidence Area, Ministry of Natural Resources, Jining 272100, China;
3. College of Resources and Environment, Shandong Agricultural University, Tai'an 271018, China
Abstract: Soil heavy metal (HM) pollution is a prominent global environmental problem. Understanding the risk characteristics and quantitative analysis of potential sources of soil HM pollution is of great significance for accurate prevention and control, scientific management, and safe utilization of soil resources. In the surface soil of Shanxian County, the contents of eight HMs, such as As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn, were collected and identified in 330 surface soil samples. The HM pollution degree was evaluated using the accumulation index and enrichment index. The carcinogenic and non-carcinogenic risks of HMs were evaluated using the health risk model designated by the Ministry of Ecology and Environment. The sources of HMs in topsoil were analyzed using correlation analysis, principal component analysis, cluster analysis, absolute principal component score-multiple linear regression (APCS-MLR), and other qualitative and quantitative methods. The results showed that all eight HM elements in the surface soil samples were lower than the background values and the screening values of agricultural land soil pollution risk in Heze City. According to Igeo and EF evaluation, only approximately 5% of Hg samples were slightly polluted, and the other seven HMs were non-polluted or slightly polluted. The carcinogenic risk and non-carcinogenic risk of As for adults and children in surface soil were at tolerable levels, and the carcinogenic risk and non-carcinogenic risk of the other seven HMs for adults and children could be ignored. The main sources of Cd, Cu, Zn, Ni, and As in the surface soil were natural background sources; the main sources of Cr and Hg were agricultural breeding sources and industrial coal sources, respectively; and the main pollution sources of Pb included other unknown sources and natural background sources. The average contribution rates of natural background sources, agricultural breeding sources, industrial coal sources, and other unknown sources were 51.69%, 27.18%, 6.83%, and 14.31%, respectively, indicating that the main sources of heavy metals in the surface soil of Shanxian County were natural background sources, followed by agricultural breeding sources.
Key words: heavy metals(HMs)      geo-accumulation index      enrichment index      health risks      source analysis     

土壤不仅是人类赖以生存的自然环境和农业生产的重要资源, 还是各种污染物的缓冲带和过滤器[1].重金属(heavy metals, HMs)是典型的土壤污染物, 可以通过自然过程或人为输入在土壤介质中积累和转移, 威胁农产品质量、生态安全和人类健康[1,2].随着社会经济的迅速发展, 土壤HMs污染问题已经引起了全世界的高度重视和深入研究[3~5].中国作为全球经济发展最快且人口分布最密集的国家之一, 我国土壤污染面积已达100万km2, 其中70%是HMs污染[3,6].十八大以来, 中国政府高度重视土壤HMs污染防治[7,8], 将其列为了优先控制污染物[9,10].土壤中HMs的来源多种多样, 主要来自母质风化的自然成土过程[11,12];大气沉降[13,14]、矿山尾矿[15,16]、垃圾填埋场处置不当[17,18]、石油及石化产品的开发使用[19,20];化肥[21,22]、动物粪便[23,24]和煤炭燃烧[25,26]等人为来源.近年来, 尤其在人口密度高和工农业活动丰富的发展中国家, 人为来源对HMs成因的贡献已经超过自然来源, 逐渐成为土壤介质中HMs积累的主要贡献者[27~31].因此, 在调查与评价HMs的污染特征及健康风险基础上, 追踪土壤中HMs的污染源和途径, 对于精准防控、科学管理与安全利用土壤资源至关重要.

单县属于典型的传统平原农区县, 经济以农业和养殖业为主, 是著名的国家商品粮和生猪生产基地.该县工业化、城镇化起步较晚, 经济实力较弱, 长期处在山东省经济洼地[32].土壤环境质量关系到农业生产安全, 但目前对于当地土壤HMs污染特征、健康风险和溯源解析研究却罕见报道.本文以单县表层土壤为研究对象, 采集并测定了330件表层土壤样品As、Cd、Cr、Cu、Hg、Ni、Pb和Zn等8种HMs的含量.采用多元统计法分析了HMs的含量特征及相关性, 借助地累积指数和富集指数对该8种HMs的污染程度进行了评估, 利用健康风险模型评价了HMs所产生的致癌风险和非致癌风险, 运用APCS-MLR模型定量解析了单县表层土壤中HMs的来源, 以期为单县土地资源安全利用提供基础性指导.

1 材料与方法 1.1 研究区概况

单县位于山东省与苏、豫、皖三省的结合部, 辖4个街道办事处和18个乡镇, 如图 1所示.该区属暖温带半湿润大陆性季风气候区, 近5 a年均降水量为848.6 mm, 年均蒸发量为1 809.7 mm.区内河流水系属淮河流域南四湖水系, 南侧为黄河故道, 浮龙湖是区内大型地表水体.总体地势由西南向东北微倾斜, 第四系-新近系松散堆积物深厚.表层土壤以潮土(壤质潮土和砂质潮土)为主, 而脱潮土、盐化潮土和半固定风砂土则零散分布于环浮岗水库及南侧黄河故道区域.单县是国家商品粮棉基地县和国家级生猪调出大县, 另具有一定的工业基础, 经多年探索, 逐步形成了以精细化工、生物医药、机械制造、新材料新能源和农副产品精深加工为主导的产业体系.

图 1 单县表层土壤采样点分布示意 Fig. 1 Sampling sites of topsoil in Shanxian County

1.2 样品采集与测试

对单县辖区进行系统布点(图 1), 截取地表至20 cm深度的表层土柱样, 每个样点由5个子样混合组成1件样品, 原始新鲜样品质量≥1 500 g, 共采集了330件表层土壤样品.

将土壤样品风干后过10目尼龙筛, 四分法取100 g样品研磨至过200目尼龙筛, 用于HMs分析:①Ni和Cr采用X射线荧光光谱法测定(PW4400, Axios PANalytical, Holland).称取4.00 g样品于低压聚乙烯塑料杯中, 置于高压压力机将粉末压成结实的圆饼后用于测定. ②Cd、Cu、Pb和Zn采样电感耦合等离子体质谱仪测定(ICP-MS7900, Agilent, U.S.A).称取0.250 0 g样品于聚四氟乙烯坩埚中, 分步加入HF、HNO3和HClO4进行消解, 消解及赶酸完毕后定容至100 mL摇匀用于测定. ③Hg和As采用氢化物-原子荧光光谱仪测定(AFS-8330, 北京吉天, 中国).称取0.500 0 g样品于50 mL比色管中, 加入王水后水浴加热消解, 用5%的盐酸定容后摇匀用于测定.化验过程中, 每32件样品插入4件密码平行样和4件土壤国家标准物质用于质量控制.平行检验合格率 > 90%, 标准物质检验合格率 > 98%.

1.3 评价方法 1.3.1 地累积指数法

地累积指数(geo-accumulation index, Igeo), 是一种研究土壤及沉积物中HMs污染程度、评判人为影响程度的重要参数[33~35].其公式为:

(1)

式中, Ci为样品中i类HMs的测量含量;Bi为对应HMs的地球化学背景值, 在本研究中Bi由菏泽市表层土壤背景值代替[36];1.5修正了由地质因素和极小的人为活动影响引起的可能变化[34,35]. Igeo从低到高分为7个等级[34,35], 分别为:无污染(Igeo < 0)、轻微污染(0 ≤ Igeo < 1)、中度污染(1 ≤ Igeo < 2)、中强污染(2≤Igeo < 3)、强污染(3 ≤ Igeo < 4)、较强污染(4 ≤ Igeo < 5)和极强污染(Igeo ≥ 5).

1.3.2 富集因子法

富集因子(enrichment factor, EF), 是通过将土壤中HMs含量与背景组分进行比对, 以此判断表生环境中HMs富集程度的重要参数[37].其计算公式如下:

(2)

式中, (Ci/ CFe样品为土壤样品中i类HMs与参比组分Fe测量含量的比值, (Bi/ BFe背景为土壤中i类HMs与参比组分Fe背景值含量的比值, 本文采用了菏泽市表层土壤元素背景值[36]. EF从低到高分为6个等级[37,38], 分别为:无污染(EF < 1)、轻微污染(1 ≤ EF < 2)、中度污染(2 ≤ EF < 5)、强污染(5 ≤ EF < 20)、较强污染(20 ≤ EF < 40)、极强污染(EF ≥ 40).

1.3.3 绝对主成分得分-多元线性回归模型

绝对主成分得分-多元线性回归(absolute principal component score-multiple linear regression, APCS-MLR)模型被认为是量化表生环境不同物质来源贡献率的可靠受体模型[39], 其计算公式如下:

(3)
(4)
(5)

式中, Cii类HMs含量估计值;X0i为对应HMs多元线性的常数项;Xki为污染源ki类HMs的多元回归系数;APCSk为绝对主成分因子得分;为污染源kCi的贡献量;PCki为已知源的贡献率;PCUi为其他未知源的贡献率.

1.3.4 健康风险评价

采用HJ 25.3-2019标准[40]推荐的计算方法对单县表层土壤中8种HMs进行健康风险评价, 主要考虑经口摄入、皮肤接触和吸入颗粒物这3种暴露途径, 并按照毒理学性质分为潜在致癌风险和非致癌风险分别进行评价.致癌风险计算方法如公式(6)~(9)所示, 非致癌风险计算方法如公式(10)~(13)所示.

(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)

式中, CR为致癌风险;HQ为非致癌危害商;ois、dcs、pis和n分别为经口摄入、皮肤接触、吸入颗粒物和累积暴露途径;Csur为土壤中HMs实测含量;mg·kg-1. 8种HMs的3类暴露途径的致癌斜率因子和非致癌参考剂量如表 1所示, 风险计算所涉及的相关参数含义及取值如表 2所示.

表 1 重金属的致癌斜率因子和非致癌参考剂量1)/mg·(kg·d)-1 Table 1 Carcinogenic slope factors and non-carcinogenic reference doses of HMs/mg·(kg·d)-1

表 2 人体健康风险评价相关参数取值[40] Table 2 Values of relevant parameters in human health risk assessment

HJ 25.3-2019标准规定当致癌风险商大于10-6时, 存在致癌风险;当非致癌风险商大于1时, 存在非致癌风险[40].但是目前较多研究表明, 对土壤HMs致癌风险评价过程中, 若致癌风险商介于10-6~10-4范围内同样可以接受[42,43].

1.4 数据处理

本研究采用Excel 365、Origin 2022和SPSS Statistics 26进行HMs测试数据的处理和相关性分析;运用SPSS Statistics 26和Excel 365进行表层土壤HMs污染源的解析;利用ArcGIS Pro 3.0、Origin 2022和PowerPoint 365软件进行图件的绘制与编辑.

2 结果与讨论 2.1 土壤重金属含量特征

对单县330件表层土壤样品中8种HMs含量进行统计分析, 结果如表 3所示.研究区Hg含量变化幅度较大, ω(Hg)范围为0.011~0.096 mg·kg-1, 变异系数达40.26%;而其他7种HMs含量变化幅度较小, 变异系数均低于15.2%.就平均值而言, Cu含量平均值仅为菏泽市背景值[36]的0.88倍, 反映了研究区Cu土壤环境状况相对较好;而其他7种HMs的含量平均值与菏泽市背景值[36]的比值介于0.90~1.00, 反映了该7种HMs的平均值与菏泽市背景基本一致.与GB 15618-2018标准筛选值[10]相比, 单县表层土壤样品中8种HMs含量的平均值均未超出筛选值, 表明对农产品质量安全的风险可以忽略. Hg和Pb的峰度均高于4.0, 概率密度分布曲线较正态分布更为陡峭, 表明存在极端值;Hg和Pb的偏度均大于1.0, 呈右偏态, 表明存在部分异常高值数据, 反映了单县表层土壤中的Hg和Pb受人为活动的干扰影响较大.

表 3 表层土壤重金属元素含量统计1) Table 3 Statistics of HMs content in surface soil

2.2 土壤重金属污染评价

以菏泽市表层土壤背景值数据作为基准值[36]计算地累积指数[图 2(a)], 研究区表层土壤8种HMs的Igeo平均值由大至小的顺序为:Pb(-0.599) > Cr(-0.604) > Cd(-0.621) > Zn(-0.643) > Ni(-0.690) > As(-0.732) > Cu(-0.791) > Hg(-0.832).经污染程度分级[图 2(b)], As、Cd、Cr、Ni、Pb和Zn等6种HMs全部为无污染;Cu存在0.3%的样点为轻微污染;而Hg分布有0.6%和5.2%的样点为中度污染及轻微污染.

(a)地累积指数分布箱线图;(b)地累积指数污染评价等级占比;(c)富集指数分布箱线图;(d)富集指数污染评价等级占比 图 2 研究区表层土壤重金属污染特征 Fig. 2 Heavy metal pollution characteristics of surface soil in the study area

仍以菏泽市表层土壤背景值数据[36]作为基准值, 采用Fe作为校准元素进行对比计算富集系数[图 2(c)].研究区表层土壤8种HMs的EF平均值由大至小的顺序为:Pb(1.070) > Cr(1.068) > Cd(1.058) > Zn(1.038) > Ni(1.003) > As(0.977) > Hg(0.962) > Cu(0.937).经污染程度分级[图 2(d)], As、Cd、Cr、Cu、Ni、Pb和Zn等7种HMs全部为无污染或轻微污染;而Hg分布有2.7%的样点为中度污染.

结合富集系数及地累积指数的分析数据, 可见EF与Igeo的评价结果基本一致, 均反映了研究区个别点位Hg的富集程度相对偏高, 表明研究区表层土壤中Hg在人为活动的影响下积累明显, 需引起重视.而其他7种HMs污染程度均为无污染或轻微污染, 说明它们主要来自于土壤母质的侵蚀风化.

2.3 土壤健康风险评价 2.3.1 非致癌健康风险评价

考虑到部分输入参数和HMs含量的不确定性, 采用了蒙特卡罗模拟(Monte Carlo simulation, MCS)风险指数的累积频率分布方法.研究区表层土壤非致癌健康风险评估结果如表 4图 3所示.Cd、Cr、Cu、Hg、Ni、Pb和Zn等7种HMs的非致癌危害商(HQ)均小于HJ 25.3指定的阈值1[40], 儿童非致癌健康风险高于成人.尽管As对儿童和成人的HQ最大值分别为1.34和1.24, 但是As对儿童和成人HQ的95%累积频率分位值分别为0.998和0.935, 均小于阈值1[40], 说明单县表层土壤HMs对儿童和成人的非致癌健康风险总体可忽略.

表 4 表层土壤重金属健康风险评价统计 Table 4 Health risk assessment statistics of HMs in surface soil

图 3 基于蒙特卡罗模拟的非致癌危害商累积频率分布 Fig. 3 Cumulative frequency distribution of non-carcinogenic hazard quotient based on Monte Carlo simulation

2.3.2 致癌健康风险评价

在所研究的8种HMs中, As、Cd和Ni是已知的致癌物, 因此对该3种HMs的致癌风险进行了评估.如表 4所示, 3种HMs致癌风险指数(CR)均值由大至小分别为:As > Ni > Cd, 其中As对儿童的致癌风险高于成人.对成人而言, Ni和Cd的CR最大值分别为2.00E-07和8.07E-09, 均小于1.00E-6, 说明Cd和Ni对成人致癌健康风险可忽略;As的成人CR值介于5.21E-06~1.41E-05, CR值虽均超出了1.00E-6, 似乎是As重金属的高毒性导致了其相对较高的CR值, 意味着As含量的小幅增加将导致致癌风险的显著增加[13], As存在一定风险, 但处于1.00E-6~1.00E-4范围内也是可以接受[42,43].对儿童而言, Ni和Cd的CR最大值分别为8.33E-08和3.36E-09, 同样均小于1.00E-6, 说明Cd和Ni对儿童致癌健康风险可忽略;As的儿童CR值均介于7.57E-06~2.05E-05, CR值均超出了1.00E-6, 存在一定风险, 但处于1.00E-6~1.00E-4范围内, 同样表明对儿童存在可耐受的致癌风险[42,43].

虽然总体上As对儿童和成人的致癌风险均可耐受, 但不应被忽视.在As的暴露途径中, 经口摄入途径的风险贡献率高达81.9%.鉴于儿童卫生观念较弱, 手、口易沾染到外界的污染物, 相较于成人更容易遭受HMs的危害[13,43].因此, 应注意督促儿童养成良好的生活习惯, 在户外环境中避免“手-嘴”接触行为暴露途径.另外, 应确定研究区内表层土壤中HMs的主要来源及其成因, 以利于采取针对性控源措施.

2.4 土壤HMs来源鉴定 2.4.1 相关性分析和聚类分析

对单县330件表层土壤样品的8种HMs进行相关分析, 如图 4(a)所示, As、Cd、Cu、Ni和Zn等5种HMs之间的相关系数普遍大于0.75, 表现出极显著正相关性, 存在极显著共同变化的趋势;Pb与As、Cd、Cu、Ni和Zn之间的相关指数介于0.63~0.73, 表现出显著正相关;而Cr和Hg与As、Cd、Cu、Ni、Zn和Pb等6种HMs之间的相关指数分别介于0.40~0.50和0.10~0.30, 反映了Hg、Cr与其余6种HMs不存在明显的共同来源.另外, 对330件土壤样品的8种HMs进行聚类分析, 如图 4(b)所示, 8种HMs可分为4类, Hg、Cr和Pb等3种HMs各自为一类, 其他5种HMs共同为一类.由此可见, 聚类分析结果与相关分析结论基本保持一致.

(a)相关关系矩阵, 椭圆窄宽和色柱深浅表示相关性系数的大小, 红色表示正相关, 蓝色表示负相关, *表示P < 0.05, **表示P < 0.01, ***表示P < 0.001;(b)聚类分析热图 图 4 研究区表层土壤重金属的相关关系矩阵与聚类分析热图 Fig. 4 Correlation matrix and cluster analysis heat map of HMs in surface soil

2.4.2 PCA/APCS矩阵源识别

在SPSS中进行KMO度量值(0.896 > 0.5)和Bartlett球形度(0.000 < 0.05)检验, 结果表明样本数据能够较好地反映表层土壤中HMs之间的联系, 可较好地适用于PCA分析[44].首先将PCA分析的主因子得分转化为绝对主因子得分(APCS), 构建APCS因子载荷矩阵进一步识别表层土壤HMs的来源, 提取了Kaiser特征值大于1的3个APCS因子(贡献率分别为57.32%、15.26%和13.35%), 结果如表 5图 5所示, 可定性识别出表层土壤中HMs累计85.93%的成因信息.

表 5 主成分分析/绝对主成分分析因子载荷矩阵 Table 5 Factor load matrix of PCA/APCS

不同的颜色圆圈表示不同绝对主成分因子的主要载荷重金属 图 5 绝对主成分分析因子载荷分解 Fig. 5 Factor load decomposition of absolute principal component analysis

第一主成分(APCS1)中, As、Cd、Cu、Ni、Pb和Zn等6种HMs具有较大的载荷值, 其权重系数分别为0.810、0.838、0.912、0.905、0.822和0.895, 方差贡献率为57.32%.这与相关分析和聚类分析所得结果相一致, 说明该6种HMs具有高度同源性.有大量研究认为, 土壤中As、Cd、Cu、Ni、Pb和Zn等6种HMs的强相关分布与成土母质或者成土过程关系紧密[45~48].并且, 经统计分析该6种HMs的含量平均值, 基本与菏泽市表层土壤背景值[36]相互吻合.因此, 可认为APCS1为自然背景源.

第二主成分(APCS2)中, 仅Cr具有较大的载荷值, 其权重系数为0.944, 方差贡献率为15.26%.大量研究认为, Cr的积累与长期的矿产采冶[49]、污水灌溉[50]和畜禽有机肥施加[51]等生产活动密切相关.矿产采冶容易造成Cr的点状污染[49], 污水灌溉会造成Cr的带状污染[50], 该两种情形所造成的污染通常较为严重.单县是畜牧业大县和农业大县, 截至2020年底, 单县生猪年出栏37.47万头, 2020年畜牧业总产值20.64亿元, 约占全县农业总产值的30%.然而在畜禽养殖中, 人们通常在饲料中添加有机铬(如烟酸铬、吡啶羧酸铬、氨基酸铬、酵母铬、草酸铬、醋酸铬等)以提高畜禽的瘦肉率、生长速率、免疫力和繁殖性能[52~54], 被认为是抗生素的潜在替代物[55].富含Cr的畜禽有机肥长期大面积施加于农田后, 通常产生面状分布的Cr环境影响, 但是并不会造成Cr的严重污染[56~58].因此, 推断APCS2为农业养殖源.

第三主成分(APCS3)中, 仅Hg具有较大的载荷值, 其权重系数高达0.983, 方差贡献率为13.35%.经统计分析, 研究区Hg含量的峰度及偏度分别为9.534和2.502(表 3), 离群高值数据较多;Igeo指数及EF指数分别显示Hg有0.6%和2.7%的样点为中度污染状态[图 2(b)图 2(d)].有研究认为, Hg的污染来源包括矿产采冶[59,60]、污水灌溉[61]和燃煤排放[62,63]等, 均与人类生产生活活动密切相关.单县表层土壤高Hg异常区主要分布在县城北部及西北部的化工工业园(单县华能生物发电有限公司、单县深能热电有限公司、单县深能环保有限公司、菏泽永舜环保科技有限公司等涉及燃煤焚烧)附近, 企业燃煤排放烟尘在主导风向的控制下, 致使局部范围表层土壤中Hg发生富集.因此, 推断APCS3为工业燃煤源.

2.4.3 APCS-MLR模型源解析

PCA/APCS矩阵源识别可以定性判别HMs来源, 而APCS-MLR模型则可以定量解析各种来源对8种HMs的成因贡献率.将PCA/APCS矩阵源识别得到的3个主因子得分和1个其他未知因子得分, 汇总标准化后得到4个APCS得分, 并结合表层土壤8种HMs含量分别对4个APCS进行多元线性拟合, 从而计算出表层土壤中8种HMs的来源贡献率.8种HMs的拟合度R2由大至小分别为:0.988(Hg)、0.975(Cr)、0.917(Ni)、0.901(Cu)、0.876(Zn)、0.767(As)、0.727(Cd)和0.713(Pb), 均大于0.70, 表明线性拟合度良好[43,45], 分析结果具有较高的可信度.

图 6所示, Cd、Cu、Zn、Ni和As等5种HMs的主要物质来源为自然背景源, 其源贡献率分别为72.29%、69.97%、62.78%、61.44%和57.38%;Cr的主要物质来源为农业养殖源, 其源贡献率为66.64%;Hg的主要物质来源为工业燃煤源, 其源贡献率为42.61%;Pb的主要物质来源包括其他未知源和自然背景源, 其源贡献率分别为46.30%和43.80%, 自然背景源稍低于其他未知源, 二者对Pb的总贡献率超出了90%水平.由各个源平均贡献率由大至小排列分别为:自然背景源(51.69%)、农业养殖源(27.18%)、其他未知源(14.31%)和工业燃煤源(6.83%), 自然背景源平均贡献率超出了50%水平, 说明单县表层土壤中8种HMs的来源主要为自然背景源, 其次为农业养殖源.

(a)各因子对重金属总含量贡献率;(b)重金属源解析弦图 图 6 表层土壤重金属的APCS-MLR模型源解析 Fig. 6 APCS-MLR model source analysis of HMs in surface soil

3 结论

(1)单县表层土壤中8种HMs含量的平均值均低于菏泽市表层土壤背景值和国家农用地土壤污染风险管控标准筛选值.经Igeo和EF评价, 仅Hg约5%的样点为轻微污染, 其他7种HMs均为无污染或轻微污染状态.

(2)人体健康风险评价表明, 单县表层土壤中As对成人及儿童的致癌风险和非致癌风险为可耐受水平, 其他7种HMs对成人及儿童的致癌风险和非致癌风险均可忽略.应注意教育儿童养成良好的卫生观念和生活习惯, 在户外环境中避免“手-嘴”接触行为暴露途径.

(3)APCS-MLR模型定量源解析结果显示, 表层土壤中HMs主要涉及4种来源. Cd、Cu、Zn、Ni和As的主要物质来源为自然背景源(51.69%, 贡献率, 下同), Cr和Hg的主要物质来源分别为农业养殖源(27.18%)和工业燃煤源(仅为6.83%), Pb的主要污染来源包括其他未知源(14.31%)和自然背景源.目前, 尽管自然背景源仍为研究区HMs的主要来源, 但是不容忽视畜禽养殖添加剂中Cr和工业燃煤烟尘中Hg的监测监管工作, 提防Cr和Hg对局部区域表层土壤的累积影响.

参考文献
[1] Weil R R, Brady N C. The nature and properties of soils (15th ed[M]. Harlow: Pearson Education, Inc., 2017.
[2] Nieder R, Benbi D K, Reichl F X. Soil components and human health[M]. Dordrecht: Springer, 2018.
[3] 石航源, 王鹏, 郑家桐, 等. 中国省域土壤重金属空间分布特征及分区管控对策[J]. 环境科学, 2023, 44(8): 4706-4716.
Shi H Y, Wang P, Zheng J T, et al. Spatial distribution of soil heavy metals and regional control strategies in China at province level[J]. Environmental Science, 2023, 44(8): 4706-4716.
[4] Wang Y Z, Duan X J, Wang L. Spatial distribution and source analysis of heavy metals in soils influenced by industrial enterprise distribution: case study in Jiangsu Province[J]. Science of the Total Environment, 2020, 710. DOI:10.1016/j.scitotenv.2019.134953
[5] Shi J D, Zhao D, Ren F T, et al. Spatiotemporal variation of soil heavy metals in China: the pollution status and risk assessment[J]. Science of the Total Environment, 2023, 871. DOI:10.1016/j.scitotenv.2023.161768
[6] 陈能场, 郑煜基, 何晓峰, 等. 《全国土壤污染状况调查公报》探析[J]. 农业环境科学学报, 2017, 36(9): 1689-1692.
Chen N C, Zheng Y J, He X F, et al. Analysis of the report on the national general survey of soil contamination[J]. Journal of Agro-Environment Science, 2017, 36(9): 1689-1692.
[7] Chen R S, De Sherbinin A, Ye C, et al. China's soil pollution: farms on the frontline[J]. Science, 2014, 344(6185). DOI:10.1126/science.344.6185.691-a
[8] Yang H, Huang X J, Thompson J R, et al. Soil pollution: urban brownfields[J]. Science, 2014, 344(6185): 691-692.
[9] GB 36600-2018, 土壤环境质量建设用地土壤污染风险管控标准(试行)[S].
[10] GB 15618-2018, 土壤环境质量农用地土壤污染风险管控标准(试行)[S].
[11] Huang S, Xiao L S, Zhang Y C, et al. Interactive effects of natural and anthropogenic factors on heterogenetic accumulations of heavy metals in surface soils through geodetector analysis[J]. Science of the Total Environment, 2021, 798. DOI:10.1016/j.scitotenv.2021.147937
[12] Komuro R, Kikumoto M. IntraPD model: leaching of heavy metals from naturally contaminated soils[J]. Environmental Pollution, 2024, 340. DOI:10.1016/j.envpol.2023.122861
[13] Ghaffari H R, Norouzi S, Heidari M. Different pollution levels and source profiles of heavy metals in the soil and surface dust of children's playgrounds in a coastal city; source-specific health risk assessment[J]. Atmospheric Pollution Research, 2023, 14(10). DOI:10.1016/j.apr.2023.101869
[14] 折开浪, 李萍, 刘景财, 等. 碳酸化对不同碱度飞灰中重金属的长期影响[J]. 中国环境科学, 2022, 42(8): 3832-3840.
She K L, Li P, Liu J C, et al. Long-term effect of carbonation on heavy metals in fly ash of different alkalinity[J]. China Environmental Science, 2022, 42(8): 3832-3840.
[15] Liu L H, Li Y, Gu X, et al. Priority sources identification and risks assessment of heavy metal(loid)s in agricultural soils of a typical antimony mining watershed[J]. Journal of Environmental Sciences, 2025, 147: 153-164. DOI:10.1016/j.jes.2023.11.007
[16] 杨爱萍, 王小燕, 肖细元, 等. 锌冶炼废渣重金属在地块土壤中的垂向迁移特征及归趋[J]. 环境科学, 2023, 44(11): 6297-6308.
Yang A P, Wang X Y, Xiao X Y, et al. Vertical migration characteristics and fate of heavy metals from zinc smelting slag in soil profile[J]. Environmental Science, 2023, 44(11): 6297-6308.
[17] El Fadili H, Ben Ali M, Touach N, et al. Ecotoxicological and pre-remedial risk assessment of heavy metals in municipal solid wastes dumpsite impacted soil in Morocco[J]. Environmental Nanotechnology, Monitoring & Management, 2022, 17. DOI:10.1016/j.enmm.2021.100640
[18] Baldo de Souza V, Hollas C E, Bortoli M, et al. Heavy metal contamination in soils of a decommissioned landfill southern Brazil: ecological and health risk assessment[J]. Chemosphere, 2023, 339. DOI:10.1016/j.chemosphere.2023.139689
[19] Nezat C A, Hatch S A, Uecker T. Heavy metal content in urban residential and park soils: a case study in Spokane, Washington, USA[J]. Applied Geochemistry, 2017, 78: 186-193. DOI:10.1016/j.apgeochem.2016.12.018
[20] Wang X S, Wang X N, Wu F, et al. Microbial community composition and degradation potential of petroleum-contaminated sites under heavy metal stress[J]. Journal of Hazardous Materials, 2023, 457. DOI:10.1016/j.jhazmat.2023.131814
[21] Salem M A, Bedade D K, Al-Ethawi L, et al. Assessment of physiochemical properties and concentration of heavy metals in agricultural soils fertilized with chemical fertilizers[J]. Heliyon, 2020, 6(10). DOI:10.1016/j.heliyon.2020.e05224
[22] 夏文建, 张丽芳, 刘增兵, 等. 长期施用化肥和有机肥对稻田土壤重金属及其有效性的影响[J]. 环境科学, 2021, 42(5): 2469-2479.
Xia W J, Zhang L F, Liu Z B, et al. Effects of long-term application of chemical fertilizers and organic fertilizers on heavy metals and their availability in reddish paddy soil[J]. Environmental Science, 2021, 42(5): 2469-2479.
[23] Sun W C, Ye J, Lin H, et al. Dynamic characteristics of heavy metal accumulation in agricultural soils after continuous organic fertilizer application: field-scale monitoring[J]. Chemosphere, 2023, 335. DOI:10.1016/j.chemosphere.2023.139051
[24] 程宇航, 李合莲, 徐国豪, 等. 猪场粪污中典型重金属和抗生素的去除及农用风险评估[J]. 农业环境科学学报, 2022, 41(1): 183-192.
Cheng Y H, Li H L, Xu G H, et al. Agricultural risk assessment and removal of typical heavy metals and antibiotics from piggery wastes[J]. Journal of Agro-Environment Science, 2022, 41(1): 183-192.
[25] Yi S Y, Li X N, Chen W P. High-resolution risk mapping of heavy metals in soil with an integrated static-dynamic interaction model: a case study in an industrial agglomeration area in China[J]. Journal of Hazardous Materials, 2023, 455. DOI:10.1016/j.jhazmat.2023.131650
[26] Yao C, Shen Z J, Wang Y M, et al. Tracing and quantifying the source of heavy metals in agricultural soils in a coal gangue stacking area: Insights from isotope fingerprints and receptor models[J]. Science of the Total Environment, 2023, 863. DOI:10.1016/j.scitotenv.2022.160882
[27] Wang C, Wang J H, Zhong C, et al. Divergent temporal changes of heavy metals in the soil induced by natural versus anthropogenic forces: a case study in the Yangtze River delta area, China[J]. Science of the Total Environment, 2023, 894. DOI:10.1016/j.scitotenv.2023.165054
[28] Qiao P W, Wang S, Li J B, et al. Quantitative analysis of the contribution of sources, diffusion pathways, and receptor attributes for the spatial distribution of soil heavy metals and their nested structure analysis in China[J]. Science of the Total Environment, 2023, 882. DOI:10.1016/j.scitotenv.2023.163647
[29] Luo X S, Yu S, Zhu Y G, et al. Trace metal contamination in urban soils of China[J]. Science of the Total Environment, 2012, 421-422: 17-30. DOI:10.1016/j.scitotenv.2011.04.020
[30] 梁家辉, 田亦琦, 费杨, 等. 华北典型工矿城镇土壤重金属来源解析及潜在生态风险评价[J]. 环境科学, 2023, 44(10): 5657-5665.
Liang J H, Tian Y Q, Fei Y, et al. Source apportionment and potential ecological risk assessment of soil heavy metals in typical industrial and mining towns in North China[J]. Environmental Science, 2023, 44(10): 5657-5665.
[31] Li R H, Wang J Z, Zhou Y F, et al. Heavy metal contamination in Shanghai agricultural soil[J]. Heliyon, 2023, 9(12). DOI:10.1016/j.heliyon.2023.e22824
[32] 王林, 田健, 曾坚, 等. 传统平原农区县域村镇聚落多维形态演变特征及定量归因——鲁西南单县实证[J]. 中国农业资源与区划, 2024, 45(4): 103-115.
Wang L, Tian J, Zeng J, et al. Multidimensional morphological evolution characteristics of rural settlements and quantitative attribution in traditional plain agricultural area: a case of Shanxian county, southwest Shandong[J]. Chinese Journal of Agricultural Resources and Regional Planning, 2024, 45(4): 103-115.
[33] Müller G. Index of geoaccumulation in sediments of the Rhine River[J]. Geojournal, 1969, 2: 108-118.
[34] 赵庆令, 李清彩, 安茂国, 等. 基于PMF-PCA/APCS与PERI的菏泽油用牡丹种植区表层土壤重金属潜在来源识别及生态风险评估[J]. 环境科学, 2023, 44(9): 5253-5263.
Zhao Q L, Li Q C, An M G, et al. Potential source identification and ecological risk assessment of heavy metals in surface soil of Heze oil peony planting area based on PMF-PCA/APCS and PERI[J]. Environmental Science, 2023, 44(9): 5253-5263.
[35] Zheng F, Guo X, Tang M Y, et al. Variation in pollution status, sources, and risks of soil heavy metals in regions with different levels of urbanization[J]. Science of the Total Environment, 2023, 866. DOI:10.1016/j.scitotenv.2022.161355
[36] 庞绪贵, 代杰瑞, 陈磊, 等. 山东省17市土壤地球化学背景值[J]. 山东国土资源, 2019, 35(1): 46-56.
Pang X G, Dai J R, Chen L, et al. Soil geochemical background value of 17 cities in Shandong Province[J]. Shandong Land and Resources, 2019, 35(1): 46-56.
[37] 赵庆令, 李清彩, 谢江坤, 等. 应用富集系数法和地累积指数法研究济宁南部区域土壤重金属污染特征及生态风险评价[J]. 岩矿测试, 2015, 34(1): 129-137.
Zhao Q L, Li Q C, Xie J K, et al. Characteristics of soil heavy metal pollution and its ecological risk assessment in South Jining District using methods of enrichment factor and index of geoaccumulation[J]. Rock and Mineral Analysis, 2015, 34(1): 129-137.
[38] 冯于耀, 史建武, 钟曜谦, 等. 有色冶炼园区道路扬尘中重金属污染特征及健康风险评价[J]. 环境科学, 2020, 41(8): 3547-3555.
Feng Y Y, Shi J W, Zhong Y Q, et al. Pollution characteristics and health risk assessment of heavy metals in road dust from non-ferrous smelting parks[J]. Environmental Science, 2020, 41(8): 3547-3555.
[39] 石震宇, 卢俊平, 刘廷玺, 等. 典型生态脆弱区水库周边大气降尘重金属风险评价及APCS-MLR模型溯源[J]. 环境科学, 2023, 44(10): 5344-5355.
Shi Z Y, Lu J P, Liu T X, et al. Risk assessment of heavy metals in dust fall around reservoirs in typical ecologically fragile areas and traceability based on APCS-MLR model[J]. Environmental Science, 2023, 44(10): 5344-5355.
[40] HJ 25.3-2019, 建设用地土壤污染风险评估技术导则[S].
[41] USEPA. Regional screening levels (RSLs) – equations[EB/OL]. https://www.epa.gov/risk/regional-screening-levels-rsls-equations, 2023-01-01.
[42] 车凯, 陈崇明, 郑庆宇, 等. 燃煤电厂重金属排放与周边土壤中重金属污染特征及健康风险[J]. 环境科学, 2022, 43(10): 4578-4589.
Che K, Chen C M, Zheng Q Y, et al. Heavy metal emissions from coal-fired power plants and heavy metal pollution characteristics and health risks in surrounding soils[J]. Environmental Science, 2022, 43(10): 4578-4589.
[43] 彭超月, 任翀, 申浩欣, 等. 黄河下游悬河段饮用水源地土壤重金属污染、来源及健康风险[J]. 环境科学, 2023, 44(12): 6710-6719.
Peng C Y, Ren C, Shen H X, et al. Soil heavy metal contamination, sources, and health risk of typical drinking water sources in the suspended reach of the Lower Yellow River[J]. Environmental Science, 2023, 44(12): 6710-6719.
[44] 于林松, 万方, 范海印, 等. 姜湖贡米产地土壤重金属空间分布、源解析及生态风险评价[J]. 环境科学, 2022, 43(8): 4199-4211.
Yu L S, Wan F, Fan H Y, et al. Spatial distribution, source apportionment, and ecological risk assessment of soil heavy metals in Jianghugongmi Producing Area, Shandong Province[J]. Environmental Science, 2022, 43(8): 4199-4211.
[45] 王美华. PCA-APCS-MLR和地统计学的典型农田土壤重金属来源解析[J]. 环境科学, 2023, 44(6): 3509-3519.
Wang M H. Source analysis of heavy metals in typical farmland soils based on PCA-APCS-MLR and geostatistics[J]. Environmental Science, 2023, 44(6): 3509-3519.
[46] 冯韶华, 俞一帆, 张旭峰, 等. 中国农田土壤重金属污染源解析研究进展[J]. 环境污染与防治, 2023, 45(9): 1300-1306.
Feng S H, Yu Y F, Zhang X F, et al. Source apportionment of heavy metals in agricultural soil in China: a review[J]. Environmental Pollution & Control, 2023, 45(9): 1300-1306.
[47] Pellinen V, Cherkashina T, Gustaytis M. Assessment of metal pollution and subsequent ecological risk in the coastal zone of the Olkhon Island, Lake Baikal, Russia[J]. Science of the Total Environment, 2021, 786. DOI:10.1016/j.scitotenv.2021.147441
[48] Lopes Zinn Y, Amaral de Faria J, Alessandra de Araujo M, et al. Soil parent material is the main control on heavy metal concentrations in tropical highlands of Brazil[J]. CATENA, 2020, 185. DOI:10.1016/j.catena.2019.104319
[49] Huang S H, Peng B, Yang Z H, et al. Chromium accumulation, microorganism population and enzyme activities in soils around chromium-containing slag heap of steel alloy factory[J]. Transactions of Nonferrous Metals Society of China, 2009, 19(1): 241-248. DOI:10.1016/S1003-6326(08)60259-9
[50] Batool F, Hussain M I, Nazar S, et al. Potential of sewage irrigation for heavy metal contamination in soil-wheat grain system: ecological risk and environmental fate[J]. Agricultural Water Management, 2023, 278. DOI:10.1016/j.agwat.2023.108144
[51] 徐凤伟, 吴文强, 朱长军, 等. 海河流域典型畜禽养殖场土壤污染调查评价[J]. 中国农村水利水电, 2019, 44(2): 84-88.
Xu F W, Wu W Q, Zhu C J, et al. Investigation and evaluation of soil pollution in typical livestock and poultry farms in Haihe River Basin[J]. China Rural Water and Hydropower, 2019, 44(2): 84-88.
[52] Pollard G V, Richardson C R, Karnezos T P. Effects of supplemental organic chromium on growth, feed efficiency and carcass characteristics of feedlot steers[J]. Animal Feed Science and Technology, 2002, 98(1-2): 121-128. DOI:10.1016/S0377-8401(02)00010-X
[53] 谢小利, 王敏奇. 有机铬对畜禽肉品质影响的研究[J]. 饲料工业, 2008, 29(16): 55-57.
Xie X L, Wang M Q. Study of the effect of organic chromium on meat quality of animal[J]. Feed Industry, 2008, 29(16): 55-57.
[54] Han M M, Tian Y, Li Z, et al. Quantitative determination of chromium picolinate in animal feeds by solid phase extraction and liquid chromatography-tandem mass spectrometry[J]. Journal of Chromatography B, 2017, 1070: 37-42. DOI:10.1016/j.jchromb.2017.10.039
[55] 邝声耀, 唐凌, 张纯, 等. 烟酸铬在猪营养中的应用研究[J]. 中国畜牧杂志, 2010, 46(22): 67-69, 72.
Kuang S Y, Tang L, Zhang C, et al. The research and application of chromium nicotinate in swine's nutrition[J]. Chinese Journal of Animal Science, 2010, 46(22): 67-69, 72.
[56] Liu B R, Huang Q, Cai H J, et al. Distribution and speciation of chromium and cadmium in an organic and inorganic fertilized chernozem[J]. Pedosphere, 2017, 27(6): 1125-1134.
[57] 周靖, 栾雅珺, 王流通, 等. 不同水肥管理稻田土壤铬生物有效性及吸收富集特征[J]. 灌溉排水学报, 2022, 41(2): 35-43.
Zhou J, Luan Y J, Wang L T, et al. The impact of irrigation and fertilization on bioavailability of chromium and its absorption and enrichment in paddy rice[J]. Journal of Irrigation and Drainage, 2022, 41(2): 35-43.
[58] 李顺江, 李鹏, 李新荣, 等. 不同肥源、施氮量对土壤-作物系统中铬、镉含量的影响[J]. 农业资源与环境学报, 2015, 32(3): 235-241.
Li S J, Li P, Li X R, et al. The influence of concentration of chromium, cadmium in soil-crop system under different fertilizers and fertilization amount[J]. Journal of Agricultural Resources and Environment, 2015, 32(3): 235-241.
[59] Wang C C, Zhang Q C, Yan C A, et al. Heavy metal(loid)s in agriculture soils, rice, and wheat across China: status assessment and spatiotemporal analysis[J]. Science of the Total Environment, 2023, 882. DOI:10.1016/j.scitotenv.2023.163361
[60] Yang H X, Li R R, Li J S, et al. Changes of heavy metal concentrations in farmland soils affected by non-ferrous metal smelting in China: a meta-analysis[J]. Environmental Pollution, 2023, 336. DOI:10.1016/j.envpol.2023.122442
[61] Yin R S, Feng X B, Shi W F. Application of the stable-isotope system to the study of sources and fate of Hg in the environment: a review[J]. Applied Geochemistry, 2010, 25(10): 1467-1477.
[62] Wang X Y, Liu E F, Yan M X, et al. Contamination and source apportionment of metals in urban road dust (Jinan, China) integrating the enrichment factor, receptor models (FA-NNC and PMF), local Moran's index, Pb isotopes and source-oriented health risk[J]. Science of the Total Environment, 2023, 878. DOI:10.1016/j.scitotenv.2023.163211
[63] Liang Y C, Zhu S Q, Liang H D. Mercury enrichment in coal fire sponge in Wuda coalfield, Inner Mongolia of China[J]. International Journal of Coal Geology, 2018, 192: 51-55.