Cranfield University, United Kingdom.
Environ Pollut. 2018 Nov;242(Pt B):1331-1336. doi: 10.1016/j.envpol.2018.08.008. Epub 2018 Aug 6.
Highways are major, open and dynamic sources of contaminants that present a risk to adjacent agricultural soils. Urban and peri-urban soils are particularly at risk because of a greater density of nearby highways with high traffic volumes. In developing economies, these soils support valuable food production and income, while in more developed economies there is a growing interest in urban food production. This commentary highlights the need to better characterise the sources, pathways to and impacts of highway contaminants on agricultural soils and it suggests research priorities. Soil contamination from highways includes metals, toxic organic pollutants and plastics (including large amounts of tyre dust). Contaminants from vehicle emissions and from wear of vehicles and highways are transferred to soil in airborne particulates, dust, splash, spray and runoff. Contamination is greatest near to the highway edge but can extend to >50m. Levels of metals including As, Cd, Cr, Cu, Pb, Ni, Zn in some soils adjacent to highways may exceed thresholds above which there is a potential risk of harm to food production. Elevated levels of non-threshold carcinogens (e.g. polycyclic aromatic hydrocarbons (PAHs)) in soil adjacent to highways are widely reported, with significant attribution to highway emissions. Mitigation options include improved vehicle design and performance, porous asphalt pavements, physical and vegetative barriers and better drainage. Research priorities include: (1) targeted soil monitoring to identify where highway contamination already presents a significant risk of harm to food production and to identify and assess trends in response to mitigation measures; (2) studies to assess the role of tyre particulate in transporting and releasing contaminants that are hazardous to soil (3) assessment of the risk to soil from pesticides used in highway maintenance; (4) analysis to inform a new emphasis on controlling soil pollution by innovative highway design and maintenance.
公路是污染物的主要、开放和动态来源，对邻近的农业土壤构成风险。城市和城郊土壤尤其面临风险，因为附近有更多交通量大的高速公路。在发展中经济体中，这些土壤支持着有价值的粮食生产和收入，而在较发达经济体中，人们对城市粮食生产的兴趣日益浓厚。本评论强调需要更好地描述公路污染物对农业土壤的来源、途径和影响，并提出了研究重点。公路污染包括金属、有毒有机污染物和塑料（包括大量的轮胎尘）。车辆排放物以及车辆和公路磨损产生的污染物通过空气传播的颗粒物、灰尘、溅出物、喷雾和径流转移到土壤中。污染最严重的地方是靠近公路边缘，但可以延伸到 50 米以外。一些靠近公路的土壤中金属含量包括砷、镉、铬、铜、铅、镍、锌等，可能超过潜在危害粮食生产的阈值。广泛报道了邻近公路的土壤中存在非阈值致癌物质（如多环芳烃 (PAHs)) 的水平升高，这主要归因于公路排放。缓解措施包括改进车辆设计和性能、多孔沥青路面、物理和植被屏障以及更好的排水。研究重点包括：(1) 有针对性的土壤监测，以确定公路污染已经对粮食生产造成重大危害的地方，并确定和评估缓解措施的趋势；(2) 评估轮胎颗粒物在运输和释放对土壤有害的污染物方面的作用的研究；(3) 评估用于公路维护的农药对土壤的风险；(4) 分析为创新的公路设计和维护提供控制土壤污染的新重点。
