北京市东南郊灌区土壤和农产品酞酸酯污染风险评估
2017-11-01刘洪禄黄权中黄冠华
李 艳,刘洪禄,顾 华,黄权中,黄冠华,李 垒
北京市东南郊灌区土壤和农产品酞酸酯污染风险评估
李 艳1,2,3,刘洪禄1,2※,顾 华1,2,黄权中3,黄冠华3,李 垒1,2
(1. 北京市水科学技术研究院,北京 100048;2. 北京市非常规水资源开发利用与节水工程技术研究中心,北京 100048;3. 中国农业大学水利与土木工程学院,北京 100083)
为明确北京市东南郊典型灌区土壤和作物酞酸酯PAEs含量和污染水平,2015年利用气象色谱-质谱仪检测了该灌区31个表层土壤样品和38个作物样品的6种优控PAEs含量。研究结果表明灌区表层土壤PAEs质量分数为1.8~12.2 mg/kg,均值5.1 mg/kg。与国内外相比,该研究中土壤PAEs含量处于较高水平。土壤中邻苯二甲酸正二丁酯(DnBP)和邻苯二甲酸二(2-乙基己基)酯(DEHP)含量均值分别占PAEs总量的60.4%和35.9%。土壤样品邻苯二甲酸二甲酯(DMP)和DnBP含量均超美国土壤PAEs控制标准,但总体上未超过美国土壤PAEs治理标准。冬小麦籽粒、夏玉米籽粒和果蔬可食用部位PAEs质量分数分别为2.34~3.66、1.76~3.15和2.26~3.76 mg/kg;与其他研究成果相比,该研究区农产品PAEs含量处于中等水平。不同污灌历史年限区域土壤和粮食作物籽粒PAEs含量均没有显著差异。冬小麦籽粒、夏玉米籽粒和果蔬中DEHP和DnBP含量分别占总量的50.3%和30.5%、45.1%和50.2%、47.16%~63.3%和31.96%~46.36%。农产品PAEs总量及各组分含量均低于欧洲的建议标准值。粮食作物籽粒中PAEs和DnBP含量与土壤中相应含量呈显著正相关,Pearson相关系数()分别为0.74~0.87和0.91~0.92。该研究中农作物对PAEs的迁移系数为0.24~1.65。儿童和成人PAEs致癌风险分别为1.34×10-5和3.87×10-5,非致癌指数分别为9.44×10-1和3.83×10-1,均在可接受范围内;通过口-作物暴露对PAEs 2种风险贡献均最大,DEHP对人体2种风险贡献最大。
土壤;污染;风险评估;冬小麦;夏玉米;蔬菜;酞酸酯
0 引 言
酞酸酯(PAEs),又名邻苯二甲酸酯,是一类人工合成有机化合物,广泛应用于增塑剂、农药载体、化妆品、润滑剂、清洁剂等行业[1]。PAEs能在周围环境中长久存在,可通过食物链干扰动物和人体正常内分泌功能,甚至引起畸形和癌变等,对生态环境和人类健康造成严重危害[2-3]。邻苯二甲酸二甲酯(DMP)、邻苯二甲酸正二丁酯(DnBP)、邻苯二甲酸二乙酯(DEP)、邻苯二甲酸丁基苄基酯(BBP)、邻苯二甲酸正二辛酯(DnOP)和邻苯二甲酸二(2-乙基己基)酯(DEHP)6种PAEs已被美国国家环保署(EPA)列为“优控污染物”[4]。
土壤是PAEs累积和迁移的重要介质,农业土壤中PAEs主要来源是工业污染、大气沉降、地膜棚膜、污水灌溉或污泥肥料等[5-6]。目前国内外已有大量学者对不同区域不同土壤利用类型(菜地、大田、果园、撂荒地等)和不同种植模式(覆膜、露天、大棚等)下土壤和农产品PAEs组分及污染水平进行了调查研究,总体上得出土壤和农作物PAEs各组分中含量最高的为DnBP和DEHP,大部分土壤DnBP浓度超过美国提出的土壤PAEs控制标准,部分土壤DMP浓度也超标,但土壤PAEs及各组分浓度基本低于美国建议的土壤PAEs治理标准;覆膜或大棚种植土壤PAEs含量高于露地种植土壤含量,菜地土壤PAEs含量高于果园、大田含量;农产品PAEs以及各组分含量总体上低于美国和欧洲提出的指标[7-21]。
上述调查研究主要集中在不同土地利用类型和不同种植模式下进行的,关于污水/再生水灌溉条件下土壤和作物PAEs污染情况调查研究还很少[6],而污水/再生水灌溉是土壤中PAEs主要来源之一[22],因此有必要对污水/再生水灌溉农田土壤和作物PAEs污染情况进行调查研究。
北京市东南郊灌区从20世纪50年代开始利用城市污水进行灌溉,从2003年开始逐步利用再生水灌溉农作物。目前对该灌区的研究主要集中在土壤重金属和盐碱性、作物品质和重金属方面[23-24],以及部分区域土壤有机氯农药和PAHs含量[25-27],而关于该灌区土壤和作物PAEs含量的研究还很少,灌区PAEs污染水平还不明确。该灌区是北京主要农产品生产基地之一,其土壤和农产品PAEs含量水平影响着人们健康和环境安全。因此有必要对该灌区土壤和农产品PAEs污染情况进行调查研究,以期为保证农产品安全和控制土壤PAEs含量提供理论支撑。
1 材料与方法
1.1 研究区概况及样品采集
研究区在北京市东南郊,北纬39°26′~40°02′,东经116°32′~116°43′(图1)。该研究区属暖温带半湿润大陆性季风气候,过去50年平均日照时数为2 459 h,平均气温在11~12 ℃之间,平均降水565 mm。研究区表层(0~20 cm)土壤粘粒、粉粒及砂砾含量百分比分别为10.5%~27.5%、46%~78.5%和1.5%~43.5%。该研究区从20世纪50年代陆续利用城市排放的污水进行农业灌溉,从2003年开始,该区域陆续引用黄村、小红门和高碑店污水处理厂的出水(再生水)进行农业灌溉。该研究污水灌溉历史20~40 a,图1中zone1区域为污灌40 a,zone2区域为污灌30 a,zone3区域为污灌20 a。
为探讨研究区不同污灌历史年限区域作物和土壤PAEs含量及污染水平,在各区域内沿主要灌溉渠道和河道布置土壤采样点,土壤采样点基本位于种植面积相对较大的田块内,共设置31个土壤监测点,如图1所示。2015年6月和9月进行土壤和植物采样,采集土样时,从田块里正方形(100 m2)的4个顶点处取表层土壤样品组成混合样品,−4 ℃冷藏,−20 ℃冷冻干燥后研磨,过0.3 mm筛。过筛后的样品置于玻璃瓶中在−20 ℃环境下保存待测。
图1 研究区示意图
作物收获时(6月中旬和9月下旬)在各土壤监测点位采集植物样品,包括冬小麦籽粒、夏玉米籽粒和夏季果蔬可食用部位,某些监测点位仅6月或9月采集到了作物样品,作物采样情况见表1。采集的作物样品放入保温箱中运输至实验室,依次用自来水、蒸馏水冲洗作物样品表面土壤和其他杂质,沾干表面水分,4 ℃保存。用于化验PAEs的土壤和作物采用铝箔纸包裹,避免二次污染。
表1 农作物样品数
1.2 土壤和植物中PAEs的索氏提取与测定方法
样品前处理:取10 g干燥过的土样,加入一定量的PAEs替代物(0.1 mg/kg),搅拌后密闭过夜,用滤纸包好后再放进索氏提取器内,以甲醇和丙酮混合液作为提取液(220 mL)(体积比为1:1)。在65 ℃真空干燥箱中干燥植物12 h,取一定量(小麦籽粒和玉米籽粒取5 g,果蔬取2 g)干燥过的植物样品,加入一定量的PAEs替代物(0.1 mg/kg),搅拌后密闭过夜,用滤纸包好后放入索氏提取器,以220 mL正己烷作为提取液。土样和作物样品索氏提取12 h后,把提取液用50 g无水硫酸钠过滤脱水,用约15 mL的提取液(土壤用液体为丙酮和甲醇混合液,植物用液为正己烷溶液)进行润洗。脱水后的提取液用旋转蒸发仪(50 ℃)和氮吹仪(50 ℃)浓缩至0.8~1.5 mL,用0.22m滤膜过滤,将过滤液倒入1.5 mL的样品瓶(液体最后体积在0.5~1.0 mL之间),放入冰箱保存待测。
PAEs测定:使用气相色谱(7890A)/质谱联用仪(5975C)进行样品分析,包括DMP、DEP、DnBP、BBP、DEHP、DnOP 6种化合物。气相色谱(7890A)-质谱(5975C)联用仪采用DB-5MS毛细管柱:其型号为30 m×0.25 mm×0.25m(美国安捷伦公司生产)。进样口的温度为280 ℃,采用无分流式进样,采用程序控制GC炉温升温,先在40 ℃保持2 min,而后以5 ℃/min升温到290 ℃,在290 ℃保持4 min。采用SIM扫描模式分析样品,定性分析利用保留时间和特征峰分析,定量分析利用基峰面积分析。
质量控制和质量保证:每批次试剂分析试剂空白,每批次样品做3个空白,空白测试结果均低于检出限。空白样品加标样后回收率为70%~120%,样品替代物的回收率在80%~120%范围内;为了检查仪器是否受到污染,每12 h做一次溶剂空白;本研究PAEs组分检出限为0.032~0.191g/kg。
1.3 数据处理
1)土壤-植物系统PAEs迁移系数计算如下:
BCF=Cplant/Csoil (1)
式中BCF为土壤-植物系统中PAEs迁移系数,Cplant为作物中PAEs质量浓度,Csoil为土壤中PAEs质量浓度(均以干质量表示,mg/kg)。
2)人体健康风险评价
采用美国能源部风险评估信息系统化学物质风险模型用户指南里暴露模型计算人群经皮肤接触、口摄入和呼吸吸入途径每天平均暴露剂量[28],计算式如下
皮肤-土壤=(2××1×××2×2)/(×) (2)
口-作物=(1×1×1×1)/(×) (3)
口-土壤=(2×2××2×2)/(×) (4)
呼吸-土壤=(2××(1/)×2×2×3)/(×) (5)
式中为物质日均暴露剂量,mg/(kg·d);其余参数定义和参考值见表2,参数取值参考美国土壤筛选水平补充指导[29]。
根据PAEs组分致癌性,分别进行非致癌风险和致癌风险评价,计算式如下,相应参数参考美国土壤筛选水平补充指导、美国能源部风险评估信息系统中化学物质毒性查询系统和中国污染场地风险评估技术导则[29-31].
HI=/(6)
低剂量暴露Risk=×(7)
高剂量暴露Risk=1-exp(-×) (8)
皮肤=口×ABS(9)
皮肤=口/ABS(10)
呼吸=呼吸×/IRa(11)
式中HI为PAEs各组分非致癌风险指数;为PAEs各组分非致癌参考剂量mg/(kg·d);皮肤和口分别为经皮肤和口途径的摄入参考剂量;Risk为PAEs各组分致癌暴露风险,先利用式(7)计算,若计算结果大于0.01则用式(8)计算;为PAEs各组分的致癌斜率因子,(kg·d)/mg,皮肤、口、呼吸分别为经皮肤、口和呼吸途径的致癌斜率因子;ABS为经肠胃吸收的污染物比例,本文取1.0;3为成人日均空气摄入量,m3/d;为成人体质量,kg;呼吸为经呼吸途径吸入的单位致癌因子。PAEs各组分毒性因子参考值见表3。
表2 健康风险评价暴露参数
表3 PAEs非致癌参考剂量(RfD)和致癌斜率因子(SF)
注:BBP、DEHP、DnBP、DMP、DEP分别代表邻苯二甲酸丁基苄基酯、邻苯二甲酸二(2-乙基己基)酯、邻苯二甲酸正二丁酯、邻苯二甲酸二甲酯和邻苯二甲酸二乙酯,下同。
Note:BBP、DEHP、DnBP、DMP、DEP arebutyl benzyl phthalate, di(2-ethylhexyl) phthalate, di-n-butyl phthalate, dimethyl phthalate and diethyl phthalate, respectively, the same below.
利用Microsoft excel 2010软件对数据进行处理和画图,利用SPSS 20.0软件对数据进行统计分析,包括利用独立样本检验法对2个历史污灌区域冬小麦PAEs含量差异显著性分析,利用方差分析中LSD法对3个历史污灌区域夏玉米PAHs含量差异显著性分析,显著性水平选取0.05。
2 结果与讨论
2.1 灌区表层土壤PAEs空间分布
图2显示灌区表层土壤PAEs质量分数为1.8~12.2 mg/kg,均值为5.1 mg/kg。总体上灌区西南部PAEs含量最高,主要分布在安定镇和长子营镇;其次为灌区东部和西北部部分地区;灌区中部和东南部表层土壤PAEs含量稍低。
表4显示了研究区不同污灌历史区域土壤PAEs含量,总体上污灌历史年限长的区域(zone 1和zone 2)土壤PAEs含量均值稍高,但各区域差异不显著(>0.05)。表4还显示了国内外部分区域关于土壤PAEs含量的研究成果。本研究灌区表层土壤PAEs含量高于贵州农业土壤、广东(中山市、汕头、高州)农业土壤、山东寿光蔬菜基地和花生主产区土壤、北京市大棚土壤、咸阳市郊菜地、南京城郊、长江三角洲农业土壤以及东北部黑土PAEs含量,与珠江三角洲稻田土壤PAEs含量接近,远低于青岛市覆膜花生和棉花土壤PAEs含量[13-17,19-20,32-39]。总体上,与国内土壤PAEs含量相比,本研究中土壤PAEs含量处于相对较高水平。与国外研究成果相比(丹麦、美国、荷兰和捷克共和国农业土壤以及法国和塞尔维亚土壤PAEs含量)[7-8,18,21,40-41],本研究区表层土壤PAEs含量也处于较高水平。Cheng等[35]调查得出北京郊区(4环至6环)表层土壤6种PAEs质量分数为0.02~1.36 mg/kg,其中含量较高值分布在大兴旧宫镇和亦庄西北部。这2个区域位于东南郊典型灌区(历史污灌)以外且属于临近区域,可作为本研究灌区对照点。可以看出本研究灌区土壤PAEs含量明显高于对照点含量,说明研究区土壤PAEs含量高主要是由污灌引起。
图2 灌区表层土壤PAEs空间分布
2.2 灌区表层土壤PAEs各组分含量及占总量比例
表5显示了整个灌区表层土壤PAEs各检测组分含量及占总量比例。灌区表层土壤样品均检测出DMP、DEP、DnBP、BBP、DEHP;土壤DnOP含量低于检出限,均未检测出。检测出的5种PAEs各组分中DnBP占总量比例最高,为60.4%;其次为DEHP,占总量比例35.9%;剩余各组分占总量的比例均低于3%。其他学者研究也得出土壤PAEs各组分中以DnBP和DEHP含量最高[8,11,17,20-21,34],主要是DnBP和DEHP属于高分子化合物,水溶性较差,容易被土壤吸附,不易被生物降解或通过其他途径消失[42];而DMP和DEP等分子量相对较小,容易被降解[43]。
本研究表层土壤DMP、DEP、DnBP、BBP、DEHP含量分别为0.09~0.37、0.03~0.07、0.55~10.8、0.001~0.006和0.42~7.06 mg/kg,均值分别为0.14、0.05、3.07、0.002、1.83 mg/kg。目前,中国还未制订土壤PAEs污染控制标准,参考美国土壤PAEs化合物的控制标准(DMP、DEP、DnBP、BBP、DEHP质量分数限值分别为0.02、0.071、0.081、1.215、4.35 mg/kg)[44],本研究区5%的土壤样品DEHP含量超标,所有采集的土壤样品DMP和DnBP含量均超过控制标准,其均值分别为控制标准的7倍和38倍,说明该灌区土壤受到PAEs污染;土壤样品DEP和BBP含量均未超过控制标准。11%的土壤样品DnBP含量超美国土壤PAEs治理标准(DMP、DEP、DnBP、BBP、DEHP质量分数分别为2.0、7.1、8.1、50、50 mg/kg)[45],但仅为治理标准的1.2~1.3倍,土壤样品其余各组分含量均未超过美国土壤治理标准。其他学者调查研究也发现土壤DMP和DnBP含量超美国土壤PAEs控制标准,如徐雪等[15]研究发现咸阳市郊菜地土壤中分别有100%和85%的土壤样品DMP和DnBP含量超过美国土壤PAEs控制标准;郑顺安等[19]得出山东寿光设施菜地采集的土壤样品DnBP含量均超控制标准,52%的土壤样品DMP含量超控制标准;陈佳袆等[20]调查得出北京设施蔬菜基地95%的土壤样品DnBP含量超过控制标准,且最高超标14倍。Tran等[18]研究得出巴黎土壤DEP和DnBP超控制标准率为40%。
表4 不同地区土壤PAEs含量的比较
表5 灌区表层土壤PAEs各检测组分含量及占总量比例
2.3 灌区各植物PAEs含量
本研究采集的作物均检测出PAEs,其含量见图3。
注:a图横坐标(1)、(2)、(3)分别代表区域1、区域2和区域3。
由图3a可以看出zone 1和zone 2区域冬小麦籽粒PAEs质量分数均值分别为3.66和2.34 mg/kg,zone 1、zone 2和zone 3区域夏玉米籽粒PAEs质量分数均值分别为3.15、1.76和2.47 mg/kg,显著性分析显示不同污灌历史年限区域冬小麦籽粒PAEs含量无显著差异(>0.05),不同区域夏玉米籽粒PAEs含量也无显著差异(>0.05)。由图3b可以看出果蔬可食用部位PAEs质量分数为2.26~3.76 mg/kg,叶菜PAEs含量较茎菜和根菜高。本研究区农作物PAEs含量显著高于山东花生主产区花生和寿光设施菜地黄瓜PAEs质量分数(0.17~1.62 mg/kg)[19,34];高于广东中山市蔬菜PAEs质量分数(均值1.15 mg/kg)[17];与珠江三角洲、南京城郊、广东东升以及广州黄埔、灵山菜地蔬菜PAEs质量分数相当(均值为2.56~3.5 mg/kg)[46-49];低于广东汕头蔬菜样品中PAEs质量分数(均值为7.16 mg/kg)[16]。说明本研究区农产品PAEs含量处于中等水平。
2.4 灌区作物PAEs各组分含量及占总量比例
表6显示了作物PAEs各检测组分检出率、含量以及各组分占总量的比例。
表6 灌区作物PAEs各检测组分含量及占总量比例
注:ND表示组分质量分数低于检出限未检测出。
Note: ND indicates the concentration of component is below the limits of detection.
冬小麦PAEs检出组分中含量最高的为DEHP和DnBP,占总量比例分别为50.3%和30.5%;其次为DMP,占总量的14.8%;其余组分占总量比例均小于5%。夏玉米PAEs检出组分中也以DnBP和DEHP含量最高,占总量比例分别为50.2%和45.1%;其余组分各自占总量比例小于3%。果蔬以DEHP和DnBP含量最高,分别占总量的47.16%~63.3%和31.96%~46.36%,其余组分各自占总量比例小于4%。其他学者在珠江三角洲蔬菜基地、山东寿光设施蔬菜基地等调查研究结果显示农产品中PAEs均以DEHP和DnBP含量为主,两者之和超过总量的50%,其余组分含量均较低[19,47,49],本研究结果与此相似。农产品PAEs以DnBP和DEHP含量最高,主要是DnBP和DEHP分子量相对较大,水溶性较低,容易在土壤中积累(表5)而被作物吸收;而DMP、DEP等由于水溶性较高,容易发生生物降解,故农产品中含量较低。
目前国内没有食品中PAEs含量限制标准,参考欧洲经济共同体食品科学委员会警告和欧洲食品安全局规定,人体每日对PAEs化合物摄入总量不能超过0.3 mg/kg体质量;摄入DnBP最大参考剂量为每日0.01 mg/kg体质量;每日DEHP最大摄入量不超过0.05 mg/kg体质量[50-52]。若按成人体质量60 kg计算,每人每天摄入小麦0.15 kg,玉米0.1 kg,果蔬0.345 kg(鲜质量),则欧洲建议摄入的冬小麦籽粒、夏玉米籽粒和果蔬PAEs质量分数限值分别为120、180、521 mg/kg,DnBP质量分数限值分别为4、6、17 mg/kg,DEHP质量分数限值分别为20、30、87 mg/kg。本研究中农产品PAEs、DEHP和DnBP含量均未超标。
2.5 粮食作物籽粒与土壤PAEs含量相关性分析
利用SPSS 20.0统计软件对土壤和冬小麦籽粒、夏玉米籽粒PAEs含量进行相关分析,结果如表7,粮食作物籽粒PAEs、DnBP均分别与土壤中PAEs和DnBP含量显著正相关(<0.05),Pearson相关系数()分别为0.74~0.87和0.91~0.92;冬小麦籽粒DMP与土壤中DMP含量显著正相关(<0.05),Pearson相关系数()为0.94;粮食作物籽粒-土壤中DEP、BBP、DEHP含量均不相关。总体上粮食作物中PAEs、DnBP含量随土壤中相应含量增加而增加。崔明明等[34]研究证实花生籽粒中PAEs和DnBP均随土壤相应含量增加而增加,吴山等[16]研究也发现蔬菜中PAEs、DEHP、DnOP与土壤中相应含量显著正相关。这说明粮食作物籽粒PAEs及某些组分含量与土壤中相同物质存在一定的线性共变趋势。
表7 土壤PAEs及各组分含量与粮食作物籽粒相应含量的回归关系
注:为冬小麦籽粒或夏玉米籽粒各物质质量浓度,为土壤各物质质量浓度。
Note:is the concentration of wheat grain or maize grain,is the concentration of soil.
2.6 不同作物对PAEs的迁移系数
表8显示PAEs及各组分在土壤-作物系统中的迁移系数。冬小麦籽粒、夏玉米籽粒和果蔬对PAEs的迁移系数分别为0.74~0.82、0.28~0.90和0.24~1.65,对PAEs各组分的迁移系数分别为0~4.83、0~7.62和0~11.0。除BBP和DEHP外,不同污灌年限区域同一作物对PAEs和其余组分迁移系数相近。总体上粮食作物和果蔬对PAEs同一组分迁移能力相似,但对PAEs各组分迁移能力存在差异。
表8 灌区PAEs各检测组分在土壤-作物系统中迁移系数
本研究中农产品对PAEs的迁移系数与山东寿光蔬菜基地蔬菜、珠江三角地区稻田对PAEs的迁移系数相近(分别为0.37~1.5和0.37~1.27)[19,39],低于广东汕头市蔬菜基地农产品、中山市农产品对PAEs的迁移系数(分别为1.23~6.96和1.02~5.91)[16-17],主要可能与作物种类和采样时间、位置等情况有关[46]。
2.7 人体健康风险评估
表9显示了灌区PAEs各组分人体健康致癌风险和非致癌风险水平(作物、土壤PAEs各组分质量分数取灌区均值)。US EPA提出一般可接受的致癌风险水平上限为10-4;当非致癌危害指数大于1时,认为对人体健康产生危害[49,52]。本研究灌区儿童和成人PAEs致癌风险分别为1.34×10-5和3.87×10-5,均低于致癌风险水平上限,在可接受范围内;儿童和成人PAEs非致癌指数分别为9.44×10-1和3.83×10-1,均低于1,说明PAEs未对人群产生明显的非致癌健康危害;从安全角度考虑,应继续关注区域PAEs浓度水平。
从暴露介质和暴露途径分析,对PAEs致癌风险和非致癌风险贡献最大的均为口-作物(小麦、玉米和果蔬),其对成人和儿童致癌总风险贡献率分别为99.96%和99.81%,对成人和儿童非致癌总风险贡献率分别为99.95%和99.85%。从PAEs各组分分析,对人体致癌总风险和非致癌总风险贡献最大的均为DEHP,对成人风险贡献率分别为99.94%(致癌)和84.15%(非致癌),对儿童风险贡献率分别为99.91%(致癌)和84.37%(非致癌),主要是DEHP含量相对较高同时其非致癌参考剂量较低所致(表3)。
表9 PAEs致癌和非致癌健康风险计算结果
3 结 论
本文研究了再生水灌区表层土壤、冬小麦籽粒、夏玉米籽粒和果蔬PAEs含量、组分和迁移规律等,主要结论如下:
1)表层土壤PAEs质量分数为1.8~12.2 mg/kg,均值为5.1 mg/kg,不同污灌历史年限区域土壤PAEs含量没有显著差异。与国内外研究结果相比,本研究中土壤PAEs含量处于较高水平。灌区表层土壤检测出的5种PAEs组分中DnBP占总量比例最高,为60.4%;其次为DEHP,占总量比例35.9%。与美国土壤PAEs控制和治理标准相比,土壤样品DMP和DnBP含量均超控制标准,但未超过治理标准。
2)冬小麦籽粒、夏玉米籽粒和果蔬可食用部位PAEs质量分数分别为2.34~3.66、1.76~3.15和2.06~3.76 mg/kg。不同污灌历史年限对粮食作物籽粒PAEs含量均无显著影响。与其他研究结果相比,本研究区农产品PAEs含量处于中等水平。粮食作物籽粒和果蔬DEHP和DnBP占总量比例分别为45.1%~50.3%和30.5%~50.2%、47.16%~63.3%和31.96%~46.36%。农产品PAEs及各组分含量均低于欧洲的建议指标。
3)粮食作物籽粒中PAEs和DnBP含量均随土壤中相应含量增加而增加。冬小麦籽粒、夏玉米籽粒和果蔬对PAEs的迁移系数分别为0.74~0.82、0.28~0.90和0.24~1.65。
4)儿童和成人PAEs致癌风险分别为1.34×10-5和3.87×10-5,非致癌指数分别为9.44×10-1和3.83×10-1,儿童和成人健康风险均在可接受范围内。
口-作物对PAEs致癌风险和非致癌风险贡献最大,对致癌总风险贡献率为99.81%~99.96%,对非致癌总风险贡献率为99.85%~99.95%。各组分中DEHP对人体致癌总风险和非致癌总风险贡献最大,对成人风险贡献率分别为99.94%(致癌)和84.15%(非致癌),对儿童风险贡献率分别为99.91%(致癌)和84.37%(非致癌)。
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Assessment of contamination risk of PAEs in soils and crops of irrigation district located at southeastern suburbs of Beijing
Li Yan1,2,3, Liu Honglu1,2※, Gu Hua1,2, Huang Quanzhong3, Huang Guanhua3, Li Lei1,2
(1.100048; 2.100048,; 3.100083)
In order to find out the concentration of phthalate acid esters (PAEs) and its pollution characteristics in topsoil and agricultural products in irrigation district at the Southeastern Suburb of Beijing, six kinds of PAEs in 31 topsoil samples and 38 crops samples in the irrigation district were detected by gas chromatography-mass spectrometry (GC-MS) in 2015. Results showed that the total concentration of six PAE compounds (∑PAEs) in topsoil ranged from 1.8 mg/kg to 12.2 mg/kg, with the average concentration of 5.1 mg/kg. There was no significant (>0.05) difference for PAEs in soil among the different sewage irrigation history. Concentration of PAEs in topsoil in this study was relatively higher compared to those reported for other places in literature. The content of di-butyl phthalate (DnBP) and di-(2-ethylhexyl) phthalate (DEHP) in top soils contributed 60.4% and 35.9% to total PAEs, respectively. According to soil allowable concentration of phthalic acid esters compounds in USA, the concentration of dimethyl phthalate (DMP) and DnBP in all soil samples exceeded the control limits, indicating that the topsoil in this district was contaminated by PAEs, but the concentrations of all PAEs compounds were lower than the cleanup objective. The total concentration of PAEs in winter wheat () grain, summer maize () grain, and edible part of vegetables and fruit were 2.34-3.66 mg/kg, 1.76-3.15 mg/kg, and 2.26-3.76 mg/kg, respectively. No significant (>0.05) difference was observed for PAEs in cereals grain among different sewage irrigation history. Concentrations of PAEs in agricultural products in this study were in the middle level compared to the results of other studies. The content of DnBP and DEHP in winter wheat grain contributed 30.5% and 50.3% to the total PAEs, respectively. The content of DnBP and DEHP in summer maize grain contributed 50.2% and 45.1% to the total PAEs, respectively. The content of DnBP and DEHP in vegetable and fruit contributed 31.96%-46.36% and 47.16%-63.3% to the total PAEs, respectively. The concentrations of the total PAEs and each PAE compound in agricultural products were less than the suggested targets in Europe, implying low health risk. The concentrations of PAEs and DnBP in cereal grain showed a significantly (<0.05) positive correlation with those in soils, with Pearson coefficients () of 0.74-0.87 and 0.91-0.92, respectively. The bioaccumulation factors of PAEs in wheat grain, maize grain, and vegetables and fruit were 0.74-0.82, 0.28-0.90, and 0.24-1.65, respectively. The carcinogenic risk of child and adult caused by PAEs were 1.34×10-5and 3.87×10-5, respectively. The non-carcinogenic hazard index of PAHs for child and adult were 9.44×10-1and 3.83×10-1, respectively. All of them were lower than the threshold values. Dietary intake is the major route of human exposure, which accounts for 99.81%-99.96% of the total carcinogenic risk and 99.85%-99.95% of the total non-carcinogenic hazard index, respectively. The carcinogenic risk and non-carcinogenic hazard index caused by DEHP in this study were relative higher, which accounted for 99.91%-99.94% of the total carcinogenic risk and 84.15%-84.37% of the total non-carcinogenic hazard index,respectively.
soil; pollution; risk assessment; winter wheat; summer maize; vegetables; phthalate acid esters
10.11975/j.issn.1002-6819.2017.18.027
X171.5
A
1002-6819(2017)-18-0203-10
2017-05-03
2017-09-06
国家自然科学基金项目、国家科技支撑项目、国家重点研发计划、北京市自然基金(编号51339007、2012BAD08B00、2016YFC0403105、15J00013)
李 艳,博士生,主要从事农业水肥高效利用机理和技术,以及再生水高效安全利用研究。Email:liyan7986@126.com
刘洪禄,博士,教授级高级工程师,主要从事再生水灌溉、农业节水方向的研究。Email:liuhonglu@yeah.net