The Relationship between Heavy Metal Contents of Soils and Rice in Coastal Areas, Fujian Province, including Influencing Factors
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摘要: 福建沿海地区土壤Pb含量远高于我国其他地区及全国背景值,其对农产品安全、生态环境的影响值得关注。本文采集该地区典型耕作区58套土壤-水稻样品,查明Pb、Cd等重金属元素含量特征及其关键控制因素。研究表明从水稻根→茎叶→稻谷,重金属元素含量和富集系数呈现明显的下降趋势,有害重金属As、Pb等的递减速率远大于植物营养元素Cu、Zn,指示水稻根部对重金属元素具有一定的阻截作用。土壤-稻谷间Pb具有显著正相关性,显示土壤Pb是稻谷Pb的重要来源;稻谷Pb含量与土壤有机碳呈负相关关系,与土壤pH呈弱负相关关系,说明富含有机碳、相对碱性的土壤环境可降低土壤Pb的生物有效性,减少稻谷对土壤Pb的吸收富集。土壤理化条件对稻谷Cd富集系数有显著影响,富含有机碳、Al2O3、Fe2O3、CaO、MgO、S的土壤条件有利于阻断稻谷对土壤Cd的吸收,降低土壤Cd污染的生态风险。本项研究为开展水田土壤重金属污染治理修复、预测稻谷食用安全提供了依据。Abstract: Lead content of soil in coastal areas of Fujian Province is higher than that of soil in other areas and in the background level of China, and is therefore of significant influence on food safety and the ecological environment. Based on Pb and Cd contents of 58 suites of soil and rice samples, the characteristic of content and its influencing factors are discussed. Results show that the concentrations and BCF values of heavy metals decrease rapidly from root to stem leaf to rice, and concentrations of toxic elements like arsenic and lead decrease more obviously than those of plant nutrients such as copper and zinc, indicating that rice root has a barrier effect for toxic element uptake. Lead content of rice is positively correlated with that of soil, indicating the soil is the main source of lead in rice. Lead content of rice is negatively correlated with organic carbon contents and pH of soil. This indicates that the abundance of organic carbon and neutral-alkaline soil conditions may reduce bioavailability of lead in soils. The bio-concentration factor of cadmium has a good correlation with physicochemical conditions of soil. Abundance of organic carbon, Al2O3, Fe2O3, CaO, MgO and S can hinder the uptake of cadmium by rice and reduce its eco-risk. This research provides the foundation for restoring paddy fields polluted by heavy metals and contributes in predicting the impact of heavy metal pollution of soil on the safety of rice.
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Key words:
- rice /
- soil /
- heavy metal content /
- BCF /
- influencing factors /
- coastal areas in Fujian Province
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表 1 水稻样品分析方法、检出限及其分析质量
Table 1. Analytical methods, detection limits and analytical quality for vegetable samples
指标 提取方法 检测方法 方法检出限(mg/kg) 报出率 (%) 标样|RE|最大值*(%) 双份分析|RE|最大值**(%) 合格率(%) As 微波消解 ICP-MS 0.03 100 6.81 15.42 100 Cd 微波消解 ICP-MS 0.002 100 1.93 15.46 100 Cr 微波消解 ICP-MS 0.005 100 5.33 13.85 100 Cu 微波消解 ICP-MS 0.005 100 2.47 13.32 100 Hg 微波消解 ICP-MS 0.0005 100 1.32 15.03 100 Ni 微波消解 ICP-MS 0.005 100 0.60 14.11 100 Pb 微波消解 ICP-MS 0.005 100 4.35 15.55 100 Se 微波消解 ICP-MS 0.01 100 4.79 17.81 100 Zn 微波消解 ICP-OES 0.05 100 2.60 14.61 100 F 扩散法 ISE 0.5 100 20.18 13.33 100 注:*表示插入标样9件,插入标样分析相对误差绝对值要求低于10%;**表示水稻根、茎叶、稻谷样品各58件全部进行双份分析,即重复分析样174件,其相对误差绝对值要求低于20%。 表 2 土壤样品分析方法、检出限及其分析质量
Table 2. Analytical methods, detection limits and analytical quality for soil samples
指标 检测方法 方法检出限 报出率(%) 一级标准物质合格率(%) 重复样合格率(%) SiO2 XRF 0.1% 100 100 100 Al2O3 XRF 0.1% 100 100 100 TFe2O3 XRF 0.1% 100 100 100 MgO XRF 0.05% 100 100 100 CaO XRF 0.05% 100 100 100 Na2O XRF 0.05% 100 100 100 K2O XRF 0.05% 100 100 100 CEC 乙酸铵交换法 0.25 cmol(+)/kg 100 100 100 pH 电位法 0.1 100 100 100 有机碳 POT 0.1% 100 100 100 As HG-AFS 0.2 mg/kg 100 100 100 Cd ICP-MS 20 ng/g 100 100 100 Cr XRF 2 mg/kg 100 100 100 Cu ICP-MS 1 mg/kg 100 100 100 Hg CV-AFS 2 ng/g 100 100 100 Ni ICP-MS 2 mg/kg 100 100 100 Pb ICP-MS 2 mg/kg 100 100 100 Se HG-AFS 0.01 mg/kg 100 100 100 Zn ICP-MS 2 mg/kg 100 100 100 注:XRF为压片-X射线荧光光谱法;POT为氧化热解-电位法;HG-AFS为氢化物-原子荧光光谱法;CV-AFS为冷蒸气-原子荧光光谱法。 表 3 水稻土重金属含量统计参数及超标情况(n=58)
Table 3. Statistical parameters of heavy metal concentration in paddy soils (n=58)
项目 As Cd Cr Cu Hg Ni Pb Zn pH 平均值 6.8 210 35 27.5 315 15.1 68 122 5.8 中位数 6.7 200 33 25.4 175 14.3 62 117 5.8 标准差 5.6 100 16 16.3 329 8.0 30 51 0.8 变异系数 0.81 0.47 0.46 0.59 1.04 0.53 0.45 0.42 0.13 最小值 0.9 72 11 7.2 35 3.5 20 27 4.5 最大值 43.0 738 87 119.0 1612 38.5 205 353 7.8 超标样数* 1 6 0 2 16 0 0 4 超标率(%) 1.7 10.3 0 3.4 27.6 0 0 6.9 注:Cd、Hg单位为ng/g,其他为mg/kg。超标是指其含量大于土壤环境质量评价标准(GB15618—1995)中水田土壤二级标准值。 表 4 水稻根、茎叶、稻谷中重金属含量及其统计特征(n=58)
Table 4. The mean values of heavy metal content in root, stem leaf and rice (n=58)
项目 介质 As Cd Cr Cu Hg Ni Pb Se Zn 平均值 稻谷 0.14 0.15 0.25 6.14 0.006 0.67 0.17 0.060 34.13 茎叶 1.32 0.61 0.53 23.93 0.028 0.39 1.77 0.203 101.22 稻根 9.28 1.07 1.42 31.43 0.030 1.17 10.72 0.242 121.26 稻谷安全标准 - 0.2 1 0.02 0.2 稻谷超标率(%) - 20.7 0 0 17.2 富集系数 稻谷 0.03 0.81 0.009 0.28 0.04 0.064 0.003 0.27 0.34 茎叶 0.26 3.42 0.019 1.09 0.19 0.038 0.026 0.89 0.98 稻根 1.59 5.85 0.048 1.43 0.18 0.094 0.168 1.03 1.26 注:Cd、Hg单位为ng/g,其他为mg/kg。 -
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