Purpose

To study the possible adverse impacts of urbanization on the accumulation of heavy metals in cultivated soils.

Materials and methods

Five hundred thirty-one topsoil samples in the farmland of the peripheral areas of western Ningbo City, Zhejiang Province, Southeast China, were collected. The contents of heavy metal elements, As, Cd, Cr, Cu, Hg, Ni, Pb, Zn, and crustal stable trace elements, Li, Eu, Sc, Sm, in the samples were determined. The stable trace elements, best correlated with the heavy metals, were chosen as the reference elements to calculate the Environmental Geochemical Baselines (EGBs) of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in the soils. Based on the established EGBs, the Enrichment Factors (EF) and Hankson Potential Ecological Risk (HRER) of the heavy metals in the soils were calculated to assess their potential ecological hazard risks.

Results and discussion

As a result, more than 30% of the sampling points of the study area were in moderate, considerable, or high risk of Cd, and 42% in moderate or considerable risk of Hg. The other heavy metals in the soils were mostly in low ecological risk. The BAF (Bio-accumulation Factor) and RAC (Risk Assessment Code) of Cd in the Cd high-risk soils were 12.43% and 45.14% on average, respectively, suggesting its high bio-availability.

Conclusions

About 80% of the rice grain growing on the Cd high-risk soils of the study area exceeded the threshold of Cd for food safety, indicating high edible risk. It implies that the farmland of the study area has been significantly adversely impacted by industrial, vehicular, or other anthropogenic activities.

中文翻译：

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基于环境地球化学基线的城区农田重金属污染评价

目的

研究城市化对耕地土壤重金属积累可能产生的不利影响。

材料和方法

采集了浙江省宁波市西部周边地区农田表土样品531份。测定了样品中重金属元素As、Cd、Cr、Cu、Hg、Ni、Pb、Zn和地壳稳定微量元素Li、Eu、Sc、Sm的含量。选择与重金属相关性最好的稳定微量元素作为参考元素来计算土壤中 As、Cd、Cr、Cu、Hg、Ni、Pb 和 Zn 的环境地球化学基线 (EGBs)。基于已建立的EGBs，计算土壤中重金属的富集因子（EF）和汉克森潜在生态风险（HRER），以评估其潜在的生态危害风险。

结果和讨论

因此，研究区30%以上的采样点处于中度、相当或高度Cd风险，42%处于中度或相当高度Hg风险。土壤中的其他重金属大多处于低生态风险。Cd高风险土壤中Cd的BAF(Bio-accumulation Factor)和RAC(Risk Assessment Code)平均分别为12.43%和45.14%，表明其生物有效性较高。

结论

研究区Cd高危土壤上生长的稻谷约有80%超过了食品安全Cd阈值，表明其食用风险较高。这意味着研究区的农田受到工业、车辆或其他人为活动的显着不利影响。