Department of Physics, Federal University of Agriculture, Abeokuta, Ogun State, Nigeria.
Department of Environmental Management and Toxicology, Federal University of Agriculture, Abeokuta, Ogun State, Nigeria.
Environ Geochem Health. 2023 Aug;45(8):6407-6433. doi: 10.1007/s10653-023-01644-2. Epub 2023 Jun 14.
This report presents the findings of the concentrations, distributions and health risks assessment of heavy metals (HMs) and volatile organic compounds (VOCs) in topsoils of two typical automobile mechanic villages (MVs) situated within Ogun State, Nigeria. One of the MVs is located in basement complex terrain (Abeokuta), while the second is in the sedimentary formation (Sagamu). Ten composite samples were collected at depth of 0-30 cm with the aid of soil auger from spent oil-contaminated spots within the two MVs. The chemical parameters of interest were Pb, Cd, benzene, ethylbenzene, toluene, total petroleum hydrocarbon (TPH) as well as oil and grease (O&G). In addition, soil pH, cation exchange capacity (CEC), electrical conductivity (EC) and particle size distribution were also evaluated in order to find out their impacts on assessed soil pollutants. Results revealed that the soils in both MVs are of sandy loam texture, slight acidic to neutral pH, mean CEC < 15 cmol/kg and mean EC > 100 μS/cm. The mean concentration of each of analyzed HMs and VOCs in soils from the two MVs was < 5 mg/kg, while the mean values of TPH and O&G content were > 50 mg/kg. The mean Cd values in soils of both MVs were higher than the national soil screening level of 0.8 mg/kg, but lower than the Canadian and Italian guidelines. There is no significant correlation between each of HMs/VOCs and any of assessed soil physicochemical variables. The non-cancer risk expressed in terms of hazard index (HI) was > 1 via oral ingestion route for adults and children at the two MVs, indicating adverse non-carcinogenic health risk. The HI > 1 value was obtained for adults only through the dermal absorption pathway in Abeokuta MV. However, HI values for the two age groups at the two MVs via inhalation route were < 1, indicating no likelihood of any non-carcinogenic effects via the breathing exposure. The potential of non-cancer risk via oral ingestion route in both MVs was derived from the contributive ratios of HMs and VOCs in the order: Cd > benzene > Pb > toluene. The carcinogenic risk (CR) values due to ingested Cd, benzene and Pb for both age groups at the two MVs exceed the safe limit range of 10 to 10. Cadmium, benzene and lead made considerable contributions to the estimation of CR through dermal exposure for adults only in Abeokuta MV. The CR values via inhalation pathway for adults and children in both MVs were within the threshold range. Artisans and children should circumvent accidental ingestion of contaminated soils in addition to wearing of protective clothes during routine vehicle maintenance activities.
本报告介绍了尼日利亚奥贡州两个典型汽车修理工村（MV）表层土壤中重金属（HM）和挥发性有机化合物（VOC）的浓度、分布和健康风险评估结果。其中一个 MV 位于基底复杂地形（阿贝奥库塔），另一个位于沉积地层（萨迦穆）。在两个 MV 内的受污染油区，使用土壤螺旋钻采集了 10 个深度为 0-30cm 的混合样本。关注的化学参数包括 Pb、Cd、苯、乙苯、甲苯、总石油烃（TPH）以及油和油脂（O&G）。此外，还评估了土壤 pH 值、阳离子交换容量（CEC）、电导率（EC）和粒度分布，以了解它们对评估土壤污染物的影响。结果表明，两个 MV 中的土壤均为砂壤土质地，呈微酸性至中性 pH 值，平均 CEC<15cmol/kg，平均 EC>100μS/cm。两个 MV 土壤中每种分析的 HM 和 VOC 的平均浓度均<5mg/kg，而 TPH 和 O&G 含量的平均值均>50mg/kg。两个 MV 土壤中的 Cd 平均值均高于国家土壤筛选值 0.8mg/kg，但低于加拿大和意大利的标准。HM/VOC 中的每一种与任何评估的土壤理化变量之间均无显著相关性。通过口服途径，成人和儿童在两个 MV 中的非致癌风险以危害指数（HI）表示均>1，表明存在不利的非致癌健康风险。在 Abeokuta MV 中，成人仅通过皮肤吸收途径获得 HI>1 值。然而，两个 MV 中两个年龄组通过吸入途径的 HI 值均<1，表明通过呼吸暴露不会产生任何非致癌影响。两个 MV 中通过口服途径的非致癌风险源于 HM 和 VOC 的贡献比例，顺序为：Cd>苯>Pb>甲苯。两个 MV 中两个年龄组因摄入 Cd、苯和 Pb 而导致的致癌风险（CR）值超过了 10 到 10 的安全范围。在 Abeokuta MV 中，仅对成人而言，Cd、苯和 Pb 通过皮肤接触对 CR 的估算有较大贡献。两个 MV 中成人和儿童通过吸入途径的 CR 值均在阈值范围内。技工和儿童在进行日常车辆维修活动时，除了穿着防护服外，还应避免意外摄入受污染的土壤。
