Water and Soil Pollution from Rail Transportation: State of Knowledge and Environmental Concerns

Abstract

This review synthesizes current knowledge on water and soil pollution attributed to drainage of conventional rail transportation infrastructure (RTI) considered in three categories: (i) tracks and associated structures, (ii) rail yards, and (iii) passenger stations. Pollutants arise from rolling-stock operation, rainwater washoff of infrastructure materials, and maintenance. Resulting runoff can convey metals, polycyclic aromatic hydrocarbons (PAHs), oil and grease, and herbicides. Among metals, zinc is washed off from galvanized steel structures, whereas iron, copper, manganese, and chromium are largely generated by abrasion of rails, wheels, brakes, and overhead wires. PAHs originate in operation of diesel-powered units. Oil and grease loads reflect lubrication of wheel–rail interfaces, switches, and other mechanical components. Herbicides, and particularly glyphosate, remain a focal concern due to potential leaching to groundwater used for drinking water. Experimental evidence and regulatory reviews indicate that risks from glyphosate can be managed with careful applications and exclusion of sensitive zones. Spatially, the highest track-related pollution is typically confined to narrow corridors (< 20 m) running along tracks. Aside from localized exceedances (e.g., herbicides in groundwater immediately beneath tracks, or metals/PAHs in near-track soils), concentrations of pollutants in soils are commonly low. In contrast, rail yards are high-risk industrial sites, with stormwater requiring on-site treatment to prevent releases of petroleum hydrocarbons, metals, and other contaminants to surface water and groundwater. Large urban stations present retrofitting challenges, necessitating drainage upgrades and compliant integration with existing sewer systems. Overall, rails represent an environmentally efficient transport mode, which can be further improved by targeted source controls and site-appropriate stormwater management not interfering with track drainage.

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