环境科学  2023, Vol. 44 Issue (5): 2879-2888   PDF    
山西野生连翘生长地土壤PAHs污染特征及风险评价
郭佳佳1, 王琦2, 康敏捷3, 焦海华2, 茹文明2, 白志辉4     
1. 山西师范大学生命科学学院, 临汾 041004;
2. 长治学院生命科学系, 长治 046011;
3. 山西农业大学资源环境学院, 太谷 030801;
4. 中国科学院生态环境研究中心, 北京 100085
摘要: 山西是我国道地药材连翘的主产地之一, 为探明连翘生长区土壤的安全性, 在连翘成熟期从山西东南部野生连翘生长区采集了70个表层(0~25 cm)土壤样品, 采用化学提取和气相色谱-质谱联用仪(GC-MS)分析方法, 探讨了样品中16种多环芳烃(PAHs)的含量与组成特征;利用比值法确定了PAHs的来源, 并通过计算污染土壤PAHs的苯并[a]芘(BaP)等效毒性当量评估了其潜在风险.结果表明, 样点土壤PAHs总量(Σ16PAHs)的平均值为1.85 μg·g-1, 3环PAHs的占比最高(平均值为76.7%), 其中, 3环的菲(Phe)和蒽(Ant)的样点检出率为100%;该生长区PAHs主要来源于空气传输与沉降的煤、生物质燃烧和车辆排放的污染物;所有样点土壤Σ16PAHs均达到了Maliszewska-Kordybach提出的农用土壤污染水平(Σ16PAHs含量>0.2 μg·g-1), 41.4%的样点达到了重度污染水平(Σ16PAHs含量>1.0 μg·g-1), 其中, 10.0%的样点土壤BaP的含量大于我国农用土壤筛选值(0.55 μg·g-1);11.4%的样点土壤16PAHs(ΣBaPeq16PAHs)和8种致癌性PAHs(ΣBaPeq8BPAHs)的BaP等效毒性当量和均超过农用土壤筛选值(0.55 μg·g-1).研究结果表明, 山西东南部野生连翘生长区土壤存在一定程度的PAHs污染, 潜在的风险不容忽视, 有必要加大研究以保障药用植物的安全生产.
关键词: 多环芳烃(PAHs)      连翘      污染土壤      来源      风险评价     
Pollution Characteristics and Risk Assessment of PAHs in the Soil of Wild Forsythia Suspensa in Shanxi
GUO Jia-jia1 , WANG Qi2 , KANG Min-jie3 , JIAO Hai-hua2 , RU Wen-ming2 , BAI Zhi-hui4     
1. School of Life Science, Shanxi Normal University, Linfen 041004, China;
2. Department of Life Science, Changzhi University, Changzhi 046011, China;
3. College of Resource and Environment, Shanxi Agricultural University, Taigu 030801, China;
4. Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
Abstract: Shanxi is one of the main producing areas of Forsythia suspensa in China. In order to explore the safety of the soil in the areas where Forsythia suspensa grows, 70 surface (0-25 cm) soil samples were collected from the main growing areas of F. suspensa in the eastsouth of Shanxi Province in July 2017. The concentration and composition characteristics of 16 polycyclic aromatic hydrocarbons (PAHs) in the sample soils were analyzed using chemical extraction and gas chromatography-mass spectrometry (GC-MS). The diagnostic ratio method was used to determine the source of PAHs in the areas. The potential ecological risk was assessed by using the method of calculating the equivalent carcinogenic concentration of benzo[a]pyrene. The results showed that the average concentration of total PAHs (Σ16PAHs) in all of the soil samples was 1.85 μg·g-1, which was dominated by three ring number PAHs, accounting for 76.7% of the total PAHs. The detection rates of phenanthrene (Phe) and anthracene (Ant) were both 100% of all the sample sites. The soil PAHs in the wild F. suspensa growing areas mainly originated from coal, biomass burning, and motor vehicle exhaust emissions, which resulted from air transport and sedimentation pathways. In all of the sample sites, the concentration of Σ16PAHs the limit standard level (0.2 μg·g-1) of Maliszewska-Kordybach for agricultural soil pollution and exceeded the soil heavy pollution level limit value (1.0 μg·g-1) in 41.4% of the sample sites. The concentration of BaP was above the risk control standard for soil contamination of agricultural land (0.55 μg·g-1) in 10% of all the soil samples. A total of 11.4% of the sample soil ΣBaPeq16PAHs and ΣBaPeq8BPAHs exceeded the agricultural soil screening value (0.55 μg·g-1). These results indicate that the contamination of PAHs was at a detectable level in the soil of wild F. suspensa growing in Shanxi, and thus their potential ecological risks should not be ignored. It is necessary to enhance the research regarding these areas to ensure the safe production of medicinal plants.
Key words: polycyclic aromatic hydrocarbons (PAHs)      Forsythia suspensa      contaminated soil      source      risk assessment     

多环芳烃(polycyclic aromatic hydrocarbons, PAHs)是环境中广泛存在的一类具有致癌、致畸和致突变毒性的有机污染物, 主要来源于人类的生活、生产活动[1, 2].进入环境中的PAHs大多数通过干湿沉降、灌溉和施肥等多种途径最终进入土壤, 同时, 由于PAHs的疏水性和土壤有机质对PAHs的吸附作用, 其在土壤中的迁移和稀释能力较弱, 因此, 土壤是PAHs的一个重要的贮存库, 尤其是在耕作层滞留较多[3].有研究报道, 滞留在耕作层的PAHs能够通过植物的吸收、迁移转化与富集等作用进入作物体[4], 影响作物品质, 对人类具有较大的潜在风险.

山西是我国林木药材连翘(Forsythia suspensa)的主产地之一, 同时, 山西又是我国的煤炭大省和典型煤化工产业区, 土壤环境中PAHs的污染水平较高. 2014年, 国家环境保护部与国土资源部联合发布的《全国土壤污染状况调查公报》显示, 山西土壤PAHs污染位点超标率高达17.5%.焦海华等[4]研究报道了山西某煤化工产业区周边农田土壤PAHs含量(Σ16PAHs)在3.87~76.0μg·g-1之间, 某钢铁企业周边农田土壤中PAHs含量在0.79~16.9 μg·g-1之间[5].张啸等[6]研究报道了太原盆地某农田表层土壤(0~25 cm)中PAHs含量为0.078~0.325μg·g-1; Duan等[7]研究了山西某焦炭生产基地周边农田土壤, Σ16PAHs含量为0.822 μg·g-1, 60%的样点达到了严重污染的水平(Σ16PAHs含量>1.00 μg·g-1).本文以山西省东南部野生连翘分布较广的区域为主要研究对象, 在连翘采收季采集表层(0~25 cm)土壤样品, 利用超声振荡萃取和气相色谱-质谱联用仪(GC-MS)分析, 测定美国环保署优先控制的16种PAHs的含量, 探讨野生连翘生长区土壤PAHs污染状况、来源及其潜在生态风险, 以期为今后进一步研究药用植物安全生产及潜在污染风险控制提供理论基础.

1 材料与方法 1.1 样品采集与制备

在连翘成熟期, 从野生连翘密集生长区域采集了70个样点的表层土壤样品.图 1为采样点示意, 样点分布在山西东南部的野生连翘生长区.采用网格布点法, 每个土壤样品由20个小格内土样均匀混合而成, 代表100~200 m2的样地范围, 用聚乙烯自封袋密封运至实验室.所有样品在室内进行自然风干, 去除碎石和动植物残体等杂物, 研磨过80目金属筛, -4℃下冷藏待分析.

图 1 山西野生连翘生长区采样点示意 Fig. 1 Map of the wild Forsythia suspensa growing areas and sampling sites in Shanxi

1.2 样品分析 1.2.1 土壤样品PAHs的提取与净化

根据文献[8]方法, 采用超声提取法对土壤样品进行前处理, 即准确称取5.0 g研磨过80目筛的土壤样品和3 g无水Na2SO4(烘箱120℃, 烘干2 h)混合; 加30 mL丙酮∶二氯甲烷(1∶1, 体积比)混合溶剂, 30℃条件下, 超声振荡提取30 min, 用干燥无水Na2SO4硅胶柱过滤, 重复提取2次, 合并两次滤液; 在40℃下, 氮气吹干; 色谱级乙腈定容到1.5 mL, 过0.22 μm有机相滤膜, 成样于棕色样品瓶, 暂置于-20℃冰箱保存待仪器分析.

1.2.2 PAHs的测定

利用气相色谱-质谱联用仪(GC-MS, 美国, Agilent 7890B-5977B型)分析样品.仪器运行条件:进样口温度保持在290℃, 氦气作为载体气体, 不分流进样, 进样体积为1 μL.升温程序:起始温度50℃, 保持1 min, 以20℃·min-1升温至200℃, 保持1 min; 以6℃·min-1升温至260℃并保持1 min; 20℃·min-1升温至290℃, 保持10 min.

每个组分的定性检测通过提取2个典型离子的丰富度和保留时间识别, 含量以峰面积大小与标样峰面积的比值计算.16种PAHs的基本信息和识别离子信息见表 1.采用外标法定量, 16种PAHs混合标样(纯度99.9%, 美国AccuStandard公司).标样含量梯度为0.01、0.1、0.5、1.0、5.0、10.0和50 μg·g-1. 16种PAHs的回收率在84%~106%.采用3个重复计算标准差.

表 1 优先控制的16种多环芳烃(PAHs)基本信息 Table 1 Basic information of the 16 species of priority controlled polycyclic aromatic hydrocarbons (PAHs)

1.3 生态风险评价方法

基于样品土壤中不同PAHs的含量, 利用不同PAHs的毒性系数[11, 12], 计算土壤PAHs单体和总量的BaP等效毒性当量, 评价土壤PAHs潜在的生态风险.不同单体PAHs的BaP等效毒性当量(BaPeqPAHi)根据如下公式计算:

(1)

式中, Ci为土壤中某一类型PAHs(i)的含量(μg·g-1), TEFi为某一类型PAHs(i)的等效毒性系数(toxic equivalent factor), 16种PAHs的TEF值见表 1.

土壤16PAHs总的BaP等效毒性当量(ΣBaPeq16PAHs)计算公式:

(2)
1.4 数据处理

结果采用Orgion 8.5、Microsoft Excel 2010和SPSS 17.0进行数据统计分析和做图.

2 结果与分析 2.1 土壤PAHs含量

根据检出率和含量土壤PAHs可分为5种类型[见图 2(a1)~(a5)]:①检出率高(100%), 含量高.主要包括Phe (0.048~1.43 μg·g-1), 平均值0.465μg·g-1、中位值0.387 μg·g-1, Ant(0.039~2.70 μg·g-1), 平均值为0.382μg·g-1、中位值0.273 μg·g-1[图 2(a1)]; ②检出率较高(58.6%)和含量也较高.仅包含一种Nap (ND~1.58 μg·g-1), 平均值为0.222 μg·g-1、中位值0.063 μg·g-1[图 2(a2)]; ③检出率较高(28.6%~35.7%)和含量较低.包括Flu (ND~0.130 μg·g-1)、Ace (ND~1.34 μg·g-1)、Pyr (ND~1.21 μg·g-1)和Fla (ND~1.36 μg·g-1) [图 2(a3)]; ④检出率较低(11.4%~15.7%)和含量较高.包括InP(ND~1.59 μg·g-1)、BbF (ND~1.87 μg·g-1)、BaP (ND~1.14 μg·g-1)、Chry (ND~1.53 μg·g-1)、BghiP (ND~0.688 μg·g-1)、BkF (ND~1.15 μg·g-1)、DaA (ND~1.26 μg·g-1)、BaA (ND~0.710 μg·g-1) [图 2(a4)]; ⑤检出率最低(< 10%)和含量也最低.仅包括Acy (ND~0.643 μg·g-1)一种类型[图 2(a5)].由此可知, 该区土壤中PAHs主要是低分子量的类型(环数 < 4, LMWPAH), 其中, Phe和Ant分布最广泛, 其次是Nap.

图 2 土壤样品中PAHs含量 Fig. 2 Contents of PAHs in the soil samples

土壤样品中, 16种PAHs的总量(Σ16PAHs)在0.278~11.6 μg·g-1之间, 平均值为1.85 μg·g-1, 中位值为0.889 μg·g-1.8种致癌性多环芳烃(BaP、DaA、BaA、BbF、BkF、Chry、InP和Nap)的总量(Σ8BPAHs)在ND~8.64 μg·g-1之间, 平均值为0.760 μg·g-1、中位值为0.078 μg·g-1.毒性最大的BaP含量为:ND~1.14 μg·g-1, 平均值为0.091 μg·g-1[图 2(b)].表明不同样点土壤Σ16PAHs的含量较高、不同样点之间差异较大, 平均值大于中位值, 且致癌性多环芳烃的含量较高.

2.2 PAHs组成特征

不同样点土壤之间PAHs的绝对含量差异较大, 为了更客观地反映其组成特征, 选用质量分数特征值, 即用土壤中某一单体组分含量占16种PAHs的总量的百分数来计算质量分数, 结果见图 3(a).该区土壤中质量分数最大的是3环PAHs, 最小的是6环组分.3环PAHs质量分数在样点土壤中的最大值为100%, 最小值为7.21%, 平均值为76.7%, 其中, 82.9%的样点中3环PAHs质量分数大于60.0%; 其次是2环PAHs, 该区土壤中质量分数最大值为81.6%, 平均值为11.0%, 37.1%的样点质量分数大于平均值; 样品土壤中4环PAHs质量分数最大值为39.1%、平均值为5.61%, 27.1%的样点中质量分数大于平均值; 5环PAHs质量分数最大值为47.9%, 平均值为4.18%, 17.1%的样点中质量分数大于平均值.

图 3 土壤样品中PAHs组成特征 Fig. 3 Characteristics of PAHs in the soil of the study area

不同样点土壤8种致癌性Σ8BPAHs占Σ16PAH总量的质量分数差异较大, 结果见图 3(b), 质量分数最大值为81.6%, 平均值为19.7%, 其中, 31.4%的样点土壤中Σ8BPAHs质量分数大于平均值.

毒性最大的BaP含量在样点土壤Σ16PAHs总量的质量分数最大值为16.9%, 平均值为1.51%, 其中, 14.3%的样点土壤BaP的质量分数大于平均值.

2.3 PAHs特征比值

本文选取了Phe/Ant、Ant/(Ant+Phe)、Fla/(Fla+Pyr)和高分子量PAHs (环数≥4, HMWPAH)和低分子量PAHs (环数 < 4, LMWPAH)的比值(HMWPAH/LMWPAH)作为特征值[13, 14], 解析该区土壤PAHs的来源, 结果见图 4.有研究报道当Fla/(Fla+Pyr)的比值小于0.4[15], Ant/(Ant+Phe)小于0.1[16], HMWPAH/LMWPAH小于1.0[17]和10 < Phe/Ant < 15[18]时, PAHs主要来源于石油污染物, 而当Fla/(Fla+Pyr)>0.4、Ant/(Ant+Phe)>0.1、HMWPAH/LMWPAH>1.0和Phe/Ant < 10时, PAHs主要来源于不完全燃烧.其中, 当0.4 < Fla/(Fla+Pyr) < 0.5时, PAHs主要来源于化石燃料的燃烧, 而当其比值大于0.5时主要来源于煤和生物质的燃烧过程[19].由图 4(a)可知, 该区98.6%的样点Ant/(Ant+Phe)的比值大于0.1, 98.6%的样点Phe/Ant的比值小于10, 属于燃烧源; 由图 4(b)可知, 该区88.6%的样点HMWPAH/LMWPAH的比值小于1, 67.1%的样点Fla/(Fla+Pyr)的比值小于0.4, 属于化石燃料源, 12.9%的样点0.4 < Fla/(Fla+Pyr) < 0.5, 来源于化石燃料燃烧, 20%的样点Fla/(Fla+Pyr)>0.5, 属于生物质燃烧源.结果表明, 土壤PAHs的主要来源于2个方面, 一是燃烧(化石燃料和生物质), 另一方面来源于石油洒落.

图 4 研究区域土壤中Ant/(Ant+Phe)与Phe/Ant和HMWPAH/LMWPAH与Fla/(Fla+Pyr)双变量源解析 Fig. 4 Bivariate plot of diagnostic ratio for Ant/(Ant+Phe) against Phe/Ant and HMWPAH/LMWPAH against Fla/(Fla+Pyr) in soil of the study area

2.4 毒性当量

依据文献[10, 11]规定的不同PAHs单体的毒性系数(表 1)和样点土壤不同PAHs单体的含量值, 利用式(1)和式(2)计算不同土壤样品中16PAHs和8种致癌性PAHs的BaP等效毒性当量, 结果见图 5.由图 5(a)可知, 不同样点土壤PAHs总的BaP等效致癌毒性当量(ΣBaPeq16PAHs)在0.009~2.82 μg·g-1之间, 平均值为0.178μg·g-1.由图 5(b)可知, 不同样点土壤8种致癌性PAHs总的毒性当量值(ΣBaPeq8BPAHs)在0~2.81 μg·g-1之间, 平均值为0.173μg·g-1.ΣBaPeq8BPAHsΣBaPeq16PAHs的比值在0~99.5之间, 平均值在23.1.表明不同样点之间PAHs的潜在致癌毒性差异较大(p < 0.5), 同时可知, 土壤样品中致癌性PAHs所占比例较高, 个别样点达到99.5%.

图 5 土壤样品中PAHs的毒性当量 Fig. 5 Toxic equivalent of PAHs in soil samples

3 讨论 3.1 土壤PAHs污染风险

PAHs污染土壤的潜在风险, 从土壤的角度分析其主要取决于PAHs总量、PAHs的类型和致癌性PAHs总量及其类型.关于土壤PAHs污染质量标准的划分, 目前, 国际上还没有统一的标准.Maliszewska-Kordybach[20]将农用土壤PAHs污染分为4个等级:Σ16PAHs含量小于0.200 μg·g-1为未受到污染、0.200~0.600 μg·g-1为轻度污染、0.600~1.00 μg·g-1为中度污染和大于1.00 μg·g-1为重度污染.依据此标准, 该区100%的样点土壤Σ16PAHs含量超过0.200 μg·g-1的最低污染限值[图 6(a)], 其中, 34.3%的样点0.200 μg·g-1 < Σ16PAHs含量≤0.600 μg·g-1, 达到轻度污染水平, 35.7%的样点0.600 μg·g-1 < Σ16PAHs含量≤1.00μg·g-1, 达到中度污染水平; 41.4%样点土壤Σ16PAHs含量超过1.00 μg·g-1, 达到重度污染水平[图 6 (a)].

(a)绿线为Σ16PAHs污染土壤的阈值标识(0.2 μg·g-1), 橙黄线为轻度污染的阈值标识(0.6 μg·g-1), 红线为中度污染阈值标识(1.0μg·g-1); (b)黑线为土壤Bap风险筛选阈值标识(0.55 μg·g-1) 图 6 样点土壤多环芳烃的风险特征 Fig. 6 Risk characteristics of PAHs in soil samples

该区土壤Σ16PAHs含量(0.278~11.6μg·g-1)和41.4%的样点达到重度污染水平, 与相关研究相比, 低于山西某煤化工产业区周边农田土壤的(3.87~76.0μg·g-1)[4]和钢铁企业周边农田土壤(0.794~16.9μg·g-1)的含量[5], 也低于山西某焦炭生产基地周边农田土壤60%的样点达到严重污染的水平[21], 但高于山西太原盆地农田土壤(0.078~0.325μg·g-1)[6]和孝义(1.18μg·g-1)、汾阳(1.23μg·g-1)、柳林(0.321μg·g-1)[22]、晋中(0.236μg·g-1)、临汾(0.723μg·g-1)[23]和忻州(0.202μg·g-1)[24]等地的农田土壤Σ16PAHs含量.

BaP是致癌性最强的环境污染物之一.我国土壤环境质量农用地土壤污染风险管控标准[25]规定BaP的风险筛选值是0.55μg·g-1, 即认为土壤中BaP含量低于该值, 是土壤环境质量的理想目标, 风险可以忽略; 高于该值, 认为可能存在不可接受的风险, 需要进行进一步的调查和风险评估.依据此标准值可知, 该区14.3%的样点土壤检测出了BaP, 其中8.57%的样点土壤BaP含量大于筛选值(0.55μg·g-1) [图 6(b)].

土壤中PAHs的种类较多, 其环境毒性的大小也有很大的差异, 为了统一量化标准, 不同PAHs的毒性大小用其BaP毒性当量大小来表示.不同PAHs的BaP毒性当量即是其毒性系数与浓度的乘积.不同PAHs的毒性系数, 目前, 国际上通用的方法是将BaP的毒性列为1, 不同PAHs的毒性与BaP的毒性进行比较, 其比值的大小即为该PAHs的毒性系数[10, 11].根据BaP毒性当量可知70个样点土壤16PAHs和8种致癌性PAHs的苯并[a]芘毒性当量(ΣBaPeq16PAHs)平均值分别为:0.178 μg·g-1和0.173 μg·g-1, 均低于我国土壤环境质量农田地土壤污染的风险筛选标准值(0.55 μg·g-1)[25], 但不同样点之间差异较大, 其中有11.4%的样点其ΣBaPeq16PAHs和ΣBaPeq8BPAHs超过风险筛选值(0.55 μg·g-1).同时, 与文献[3]报道的波兰农用污染土壤的最低限值(ΣBaPeq16PAHs含量 < 0.050 μg·g-1)相比, 该区85.7%的样点土壤超过限值.与加拿大[26]规定的农田土壤指导值(0.10 μg·g-1)相比, 该区12.9%的样点超过了指导值标准; 此外, 有14.3%的样点其ΣBaPeq8BPAHs值大于加拿对农用土壤致癌性的毒性当量限值标准(PAHs含量为0.02 μg·g-1)[2].

综上所述, 虽然该野生连翘生长区大多数样点土壤PAHs含量低于我国的筛选值标准(BaP含量为0.55 μg·g-1), 但因其: ①不同样点之间的差异较大, 且有11.4%的样点土壤中16种PAHs的BaP毒性当量达到了农用土壤污染风险筛选值; ② GB 15618-2018标准仅对毒性最高的BaP给出了筛选值标准(0.55 μg·g-1), 但研究区土壤中存在多种PAHs的复合污染.有研究报道多种复合污染物同时存在于同一介质, 会加大不同污染物的潜在风险[4]; ③该区土壤中致癌性PAHs所占的比例较高(平均值为23.1%), 本研究认为该区土壤PAHs的潜在风险不容忽视, 应引起更多关注.

3.2 PAHs的来源解析

该区土壤PAHs的分布具有如下3个特征:①不具有典型工业集中污染的特征.无论是污染物的种类还是含量, 样点之间均有较大的差异.土壤PAHs单体的检出数量从2种~16种不等; Σ16PAHs含量最小(0.278μg·g-1)和最大(11.6μg·g-1) 之间差异在1~3个数量级; ②典型PAHs主要是生物质、化石燃料不完全燃烧和石油泄漏的产物; ③土壤PAHs以较稳定的、能被大气远距离传输的3环类型为主.样点土壤3环PAHs的质量分数平均值高达76.7%, 其中, Phe和Ant是主要的3环PAHs类型.究其原因:①野生连翘生长地多远离工业区, 因此, 没有典型工业集中污染的特征, 污染物的分布无规律性; ②虽然连翘自然分布区多远离工业污染源, 但周边有村庄和承担繁重运输任务的山间公路穿行.当地居民日常生活和取暖主要依赖燃煤, 农业废弃的秸秆和林木枯枝多以烧荒的方式处理, 因此, 煤和生物质燃烧会排放少量PAHs; ③连翘成熟期, 当地居民进山采摘连翘果实.尤其是近年来, 燃油摩托车和三轮车是他们常用的交通运输工具.车辆尾气排放和漏油事故造成的污染具有局限性和不确定性, 是导致样点之间差异的另一个重要原因; ④ PAHs的大气传输性.山西是我国重要的煤化工产业区, 燃煤工业和煤炭运输车辆尾气排放大量的PAHs进入土壤或粘附颗粒物表面随扬尘或气流长距离运输.该分析也得到了相关研究结果的支持, 如文献[27~31]认为低环组分的PAHs挥发性强, 多以气态形式存在于大气颗粒物中, 随气体进行长距离输送扩散到较远地区.有研究认为2~3环PAHs主要来源于原油和石油产品泄漏、化石燃料不完全燃烧和生物质低温燃烧[32~36].其中, Phe和Ant被作为煤和生物质燃烧源的指示物[37~40], Nap通常作为石油源的指示物[41, 42].同时, 有研究认为燃烧过程中排放的Ant和Phe的量相近[43~45], 但由于Ant比Phe更易于受光的影响而发生光降解, 因此, 环境中Phe/Ant的值, 可以作为判断多环芳烃来源于远距离传输或局部地区排放的一个重要参数.该区84.3%的样点Phe/Ant的值大于1.0, 表明大气传输是该区土壤PAHs的重要来源之一.

4 结论

(1) 山西野生连翘生长区土壤存在一定程度的PAHs污染, 但样点之间差异较大.其中, Phe和Ant是典型的污染物类型.

(2) 该区土壤PAHs可能存在生态环境或农作物生长风险, 11.4%的样点土壤ΣBaPeq16PAHs含量达到了我国农用土壤污染风险筛选限值(0.55 μg·g-1), 应当加强土壤环境和连翘生长质量协同监测.

(3) 该区土壤PAHs主要来源于周边居民的生活、生产活动和大气远距离的传输作用.

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