-
镉 (Cd) 是人体非必需的有剧毒的重金属元素[1-2],极易在小麦等农作物中富集,并通过食物链对人体健康产生威胁[3-5]。近年来河南[6]、甘肃[7]和陕西[8]等地均相继出现不同程度的小麦Cd含量超标现象。SONG等[9]指出小麦对我国北方人群Cd摄入量的贡献高达29.8%。土壤-小麦系统Cd污染风险识别与评估是小麦Cd污染防治策略制定的前提和重要参考。
近年来国内外研究人员对土壤-小麦污染风险进行了大量研究,多集中于应用不同评价指标对Cd污染土壤和小麦进行污染等级划分与定性评估[5,10-11]。其中,MULLER开发的地积累指数法被广泛用于土壤及河道沉积物Cd污染风险研究[12]。HAKANSON提出的潜在生态风险指数综合考虑了Cd毒性效应和相对贡献度等参数,在农田土壤Cd累积研究中应用较多[13]。ZHUANG等[14]应用地积累指数法对我国主要小麦产区土壤Cd生态风险进行了量化评估。李艳玲等[15]应用潜在生态指数对济源市平原区小麦田Cd污染特征进行了评估分析。美国环保署开发的健康风险评估模型建立了Cd暴露途径与人体Cd摄入量的定量关系,被广泛用于评估污染小麦摄入风险评估的研究中[8,16]。然而土壤Cd累积周期长,影响因素繁杂,不同区域农田土壤Cd空间异质性显著[1,11,17-18]。贵州土壤Cd背景值 (0.66 mg·kg−1) 约为内蒙古土壤Cd背景值 (0.05 mg·kg−1) 的13.2倍[17]。上述评价模型多使用固定评价因子和参考标准,难以对区域农田Cd污染风险进行量化分析[19-20]。同时,我国幅员辽阔,不同地区农田土壤理化性质、社会经济水平和人群生活习惯与国外研究差别较大,固定参数的直接应用使评价结果存在较大偏差[21-22],难以充分反映区域土壤-小麦系统Cd污染风险变化趋势。
基于以上问题,本研究以河南省某地为研究对象,基于部分区域大面积调查和不确定性理论,将Monte-Carlo随机模拟方法引入到区域农田Cd污染风险综合评估中,获取该地区土壤和小麦Cd污染风险概率分布情况,探讨有效可行的污染防控目标,以期为区域小麦Cd污染风险管理提供理论指导。
区域农田镉含量空间变异与综合风险的不确定性评估
Spatial variation of cadmium concentration in regional wheat fields and uncertainty-enabled comprehensive risk assessment
-
摘要: 我国小麦镉 (Cd) 污染格局多样,从不确定性角度评估区域小麦田Cd累积风险有助于提升污染防治决策的准确性。本研究基于不确定性理论,将蒙特卡洛 (Monte-Carlo) 随机模拟方法引入到区域土壤-小麦系统Cd污染综合风险评估中,结合多元统计和空间分析开展实例研究。结果表明河南省某小麦主产区92.8%的土壤样品Cd含量超过农田土壤风险筛选值 (0.6 mg·kg−1) ,84.0%的小麦籽粒样品Cd含量超过国家食品安全限量标准 (0.1 mg·kg−1) 。区域土壤-小麦系统Cd累积水平整体上呈现西北高东南低的空间分布格局。区域Cd生态风险以中度污染为主。区域人群Cd摄入量超过WHO推荐安全值的风险概率为31.6%,控制土壤Cd累积趋势可将该超标风险下降至7.3%。不确定性模拟、空间分析和场景分析的综合应用可准确识别农田Cd污染风险等级和相应概率,为区域Cd污染防治提供决策建议。Abstract: China faces great challenges in protecting its wheat soil from spatial heterogeneity of cadmium (Cd) accumulation. The uncertainty analysis helps improve the accuracy in the risk assessment for Cd in soil-wheat system. Based on the stochastic theory, the Monte-Carlo simulation approach was introduced in the ecological risk assessment and health risk assessment. Together with the multi-statistical technique and spatial analysis, proposed models were used for risk analysis in a certain area of Henan Province. Results showed that about 92.8% of the soil samples had Cd exceeding the national soil threshold value (0.6 mg·kg−1), and 84.0% of the wheat samples had Cd concentrations exceeding the national foodstuff threshold value (0.1 mg·kg−1). The concentration of Cd in the soils in the spatial distribution decreased from northwest to southeast, and the ecological risk of regional Cd is mainly moderate pollution. The ecological risk of Cd in the investigated wheat fields fall into the moderate contamination level. About 31.6% of the adult populations consumed wheat cropping in affected areas risk a daily Cd intake above the WHO limit. This risk was significantly decreased to 7.3%, when the accumulation trend of Cd has been controlled. The integrated application of uncertainty simulation, spatial analysis, and scenario analysis can accurately identify the risk levels and probability of Cd contamination from regional agricultural field, provide decision-making recommendations for the prevention and control of local Cd contamination.
-
Key words:
- spatial heterogeneity /
- Monte Carlo simulation /
- ecological risk /
- health risk /
- cadmium
-
表 1 土壤风险指数分级
Table 1. Grade of of soil risk index
分级 0 1 2 3 4 5 6 Igeo值 <0 0~1 1~2 2~3 3~4 4~5 >5 污染程度 无 轻度 轻~中 中度 中~重 重度 极严重 Er值 — <40 40~80 80~160 160~320 >320 — 生态风险 — 低 中等 中~高 高 极高 — 表 2 区域土壤基本性质及土壤-小麦Cd含量特征
Table 2. Descriptive statistics of soil properties and Cd concentration in the soil-wheat system being investigated
检测参数 最小值 最大值 平均值 中值 标准差 土壤pH 5.44 8.60 8.05 8.23 0.56 土壤有机质/(g·kg−1) 10.90 72.90 23.80 21.80 8.82 黏粒/% 16.50 47.30 28.50 28.00 5.54 阳离子交换量 10.60 27.50 18.20 17.8 3.35 土壤Cd/(mg·kg−1) 0.11 3.89 1.45 1.40 0.63 小麦Cd/(mg·kg−1) 0.04 0.51 0.18 0.17 0.09 小麦Cd-BCF 0.022 3.24 0.16 0.12 0.18 -
[1] ZHAO F J, MA Y, ZHU Y G, et al. Soil contamination in China: Current status and mitigation strategies[J]. Environmental Science & Technology, 2015, 49(2): 750-759. [2] XING W, ZHAO Q, SCHECKEL K G, et al. Inhalation bioaccessibility of Cd, Cu, Pb and Zn and speciation of Pb in particulate matter fractions from areas with different pollution characteristics in Henan Province, China[J]. Ecotoxicology and Environmental Safety, 2019, 175: 192-200. doi: 10.1016/j.ecoenv.2019.03.062 [3] ÅKESSON A, CHANEY R. Cadmium exposure in the environment: Dietary exposure, bioavailability and renal effects[J]. Encyclopedia of Environmental Health, 2019, 1: 465-473. [4] 胡文友, 陶婷婷, 田康, 等. 中国农田土壤环境质量管理现状与展望[J]. 土壤学报, 2021, 58(5): 1094-1109. doi: 10.11766/trxb202009220533 [5] RIZWAN M, ALI S, ABBAS T, et al. Cadmium minimization in wheat: A critical review[J]. Ecotoxicology and Environmental Safety, 2016, 130: 43-53. doi: 10.1016/j.ecoenv.2016.04.001 [6] LI Y L, CHEN W P, YANG Y, et al. Quantifying source-specific intake risks of wheat cadmium by associating source contributions of soil cadmium with human health risk[J]. Ecotoxicology and Environmental Safety, 2021, 228: 112982. doi: 10.1016/j.ecoenv.2021.112982 [7] NAN Z, ZHAO C, LI J, et al. Relations between soil properties and selected heavy metal concentrations in spring wheat (Triticum aestivum L. ) grown in contaminated Soils[J]. Water, Air, and Soil Pollution, 2002, 133(1): 205-213. [8] LEI L M, LIANG D L, YU D S, et al. Human health risk assessment of heavy metals in the irrigated area of Jinghui, Shaanxi, China, in terms of wheat flour consumption[J]. Environmental Monitoring and Assessment, 2015, 187: 647. doi: 10.1007/s10661-015-4884-9 [9] SONG Y, WANG Y, MAO W, et al. Dietary cadmium exposure assessment among the Chinese population[J]. Plos One, 2017, 12: 0177978. [10] WANG Z W, NAN Z R, WANG S L, Accumulation and distribution of cadmium and lead in wheat (Triticum aestivum L. ) grown in contaminated soils from the oasis, north-west China[J]. Journal of the Science of Food and Agriculture, 2011, 91(2): 377-384. doi: 10.1002/jsfa.4196 [11] 李岩, 师华定, 刘孝阳, 等. 耒水流域土壤重金属污染的时空变异对比[J]. 环境工程学报, 2020, 14(3): 842-852. doi: 10.12030/j.cjee.201905097 [12] MULLER G. Index of geoaccumulation in sediments of the Rhine river[J]. Geojournal, 1969, 2(3): 109-118. [13] HAKANSON L. An ecological risk index for aquatic pollution control-a sedimentological approach[J]. Water Research, 1980, 14(8): 975-1001. doi: 10.1016/0043-1354(80)90143-8 [14] ZHUANG Z, WANG Q, HUANG S, et al. Source-specific risk assessment for cadmium in wheat and maize: Towards an enrichment model for China[J]. Journal of Environmental Sciences, 2023, 125(3): 723-734. [15] 李艳玲, 陈卫平, 杨阳, 等. 济源市平原区农田重金属污染特征及综合风险评估[J]. 环境科学学报, 2020, 40(6): 2229-2236. doi: 10.13671/j.hjkxxb.2020.0020 [16] USEPA, Risk assessment guidance for superfund, Volume I: Human health evaluation manual part A [M]. Environmental Protection Agency, Washington, D. C. 1989. [17] 国家环境保护局, 中国环境监测总站. 中国土壤元素背景值[M]. 北京: 中国环境科学出版社, 1990. [18] 陈卫平, 杨阳, 谢天, 等. 中国农田土壤重金属污染防治挑战与对策[J]. 土壤学报, 2018, 55(2): 261-272. [19] CHEN W P, LI L Q, CHANG A C, et al. Characterizing the solid-solution partitioning coefficient and plant uptake factor of As, Cd, and Pb in California croplands[J]. Agriculture Ecosystems & Environment, 2009, 129(1-3): 212-220. [20] YANG Y, LI Y L, DAI Y T, et al. Historical and future trends of cadmium in rice soils deduced from long-term regional investigation and probabilistic modeling[J]. Journal of Hazardous Materials, 2021, 415: 125746. doi: 10.1016/j.jhazmat.2021.125746 [21] SWARTJES F A, VERSLUIJS K W, OTTE P F. A tiered approach for the human health risk assessment for consumption of vegetables from with cadmium-contaminated land in urban areas[J]. Environmental Research, 2013, 126: 223-231. doi: 10.1016/j.envres.2013.08.010 [22] PENG C, WANG, M E, CHEN W P. Modelling cadmium contamination in paddy soils under long-term remediation measures: model development and stochastic simulations[J]. Environmental Pollution, 2016, 216: 146-155. doi: 10.1016/j.envpol.2016.05.038 [23] 鲁如坤. 土壤农业化学分析方法[M]. 北京: 中国农业科技出版社, 2000. [24] 王天齐, 李艳玲, 杨阳, 等. 碱性土壤锌镉比对小麦籽粒镉积累的影响[J]. 环境科学学报, 2021, 41(12): 5143-5149. doi: 10.13671/j.hjkxxb.2021.0209 [25] 张扣扣, 贺婧, 钟艳霞, 等. 基于GIS对宁夏某铜银矿区周边土壤重金属来源解析[J]. 环境科学, 2022, 43(11): 5192-5204. doi: 10.13227/j.hjkx.202201113 [26] 环境保护部. 中国人群暴露参数手册(成人卷)[M]. 北京: 中国环境出版社, 2013: 256. [27] 土壤环境质量农用地土壤污染风险管控标准(试行): GB 15618-2018 [S]. 2018. [28] 国家卫生部, 国家标准化管理委员会. 食品中污染物限量: GB 2762-2005[S]. 2005. [29] 张红振, 骆永明, 章海波, 等. 水稻、小麦籽粒砷、镉、铅富集系数分布特征及规律[J]. 环境科学, 2010, 31(2): 488-495. doi: 10.13227/j.hjkx.2010.02.042 [30] LIU K, LV J L, HE W X, et al. Major factors influencing cadmium uptake from the soil into wheat plants[J]. Ecotoxicology and Environmental Safety, 2015, 113: 207-213. doi: 10.1016/j.ecoenv.2014.12.005 [31] JECFA (Joint FAO/WHO Expert Committee on Food Additives), Joint FAO/WHO Expert Committee on Food Additives Seventy-third Meeting [M]. World Health Organization, Geneva. 2010. [32] 周睿, 魏建宏, 罗琳, 等. 赤泥添加对石灰性土壤中Pb、Cd形态分布及小麦根系的影响[J]. 环境工程学报, 2017, 11(4): 2560-2567. doi: 10.12030/j.cjee.201606191 [33] 曹阳, 李撑娟, 王辉, 等. 施加钝化剂及叶面肥对大田小麦-玉米轮作Cd吸收转运的影响[J]. 农业环境科学学报, 2023, 42(2): 319-326. doi: 10.11654/jaes.2022-0730 [34] GRÜTER R, MEISTER A, SCHULIN R, et al. Green manure effects on zinc and cadmium accumulation in wheat grains (Triticum aestivum L. ) on high and low zinc soils[J]. Plant and Soil, 2017, 422: 437-453. [35] GRÜTER R, COSTEROUSSE B, MAYER J, et al. Long-term organic matter application reduces cadmium but not zinc concentrations in wheat[J]. Science of the Total Environment, 2019, 669: 608-620. doi: 10.1016/j.scitotenv.2019.03.112