Abstract

The contamination of soils due to traffic-related activities has been an ever-growing concern since the mid-20th century. This global issue impacts both rural soils often used for agriculture and grazing, and urban soils in densely populated urban areas. Therefore, this work aimed to evaluate the distribution of catalytic converters-related elements (Pd, Pt, Rh, Mo, and Ni) in roadside soils from the state of Rio de Janeiro, Brazil. Four highways, Linha Vermelha, Avenida Brasil, Via Dutra, and BR-465, were selected according to their daily traffic volume and urban/non-urban settings. Linha Vermelha and Avenida Brasil cross areas with high population density, while Via Dutra and BR-465 intersect non-urban locations. In addition to several physicochemical parameters, soil concentrations of three platinum group elements (Pd, Pt, and Rh), Mo and Ni were determined in samples collected at different distances from each highway (1, 3, 5, 10, and 15 m). While the results for Mo, Ni, Pt, and Rh are within reference levels in all highways, alarming concentrations of Pd were found, especially in soils bordering urbanized areas – note that Pd emissions to roadside soils are unique to automobile catalytic converters. Hence, as per the calculated geoaccumulation indexes, soils adjacent to Linha Vermelha and Avenida Brasil are either highly polluted or extremely polluted by Pd at all sampling points (averaging concentrations of 376 and 112 μg kg⁻¹, respectively). The high traffic volume, frequent traffic congestion, and incidence of anthropogenic processes are the most probable roots for greater metal pollution in soils neighboring the selected urban highways. Contrariwise, soil metal levels in the non-urban areas are mainly dependent on traffic emissions and thereby in agreement with the pertaining literature, as concentrations decline with increasing distances from the road. Moreover, in comparison with the soils adjoining the urban highways, the acidic pH, reduced exchange capacity, and high organic matter content, suggest an insignificant contribution from other anthropic activities at Via Dutra and BR-465.

摘要

自 20 世纪中叶以来，与交通有关的活动对土壤造成的污染一直是人们日益关注的问题。这一全球性问题既影响经常用于农业和放牧的农村土壤，也影响人口稠密城市地区的城市土壤。因此，这项工作旨在评估巴西里约热内卢州路边土壤中催化转化器相关元素（Pd、Pt、Rh、Mo 和 Ni）的分布。根据每日交通量和城市/非城市环境选择了四条高速公路，即 Linha Vermelha、Avenida Brasil、Via Dutra 和 BR-465。Linha Vermelha 和 Avenida Brasil 穿过人口密度高的地区，而 Via Dutra 和 BR-465 则与非城市地区相交。除了几个物理化学参数外，土壤中三种铂族元素（Pd、Pt 和 Rh）的浓度， 米）。虽然所有高速公路的 Mo、Ni、Pt 和 Rh 的结果都在参考水平范围内，但发现了惊人的 Pd 浓度，尤其是在与城市化地区接壤的土壤中——请注意，向路边土壤排放的 Pd 是汽车催化转换器独有的。因此，根据计算的地积累指数，在 Linha Vermelha 和 Avenida Brasil 附近的土壤在所有采样点都受到 Pd 的高度污染或极度污染（平均浓度为 376 和 112 μg kg ^-1， 分别）。高交通量、频繁的交通拥堵和人为过程的发生是选定城市高速公路附近土壤中金属污染严重的最可能根源。相反，非城市地区的土壤金属水平主要取决于交通排放，因此与相关文献一致，因为浓度随着与道路距离的增加而下降。此外，与毗邻城市高速公路的土壤相比，酸性 pH 值、降低的交换容量和高有机质含量表明 Via Dutra 和 BR-465 的其他人为活动的贡献微不足道。