Editing Road runoff contaminant load (section)

== Boundary Conditions ==
Boundary inclusions encompass all pollutants mobilized from road surfaces and transported by runoff into surface waters, including heavy metals, hydrocarbons, nutrients, suspended sediments, and semivolatile organic compounds. The spatial boundary includes the catchment areas draining road surfaces to receiving water bodies. Boundary exclusions are pollutants originating from non-road sources such as agricultural runoff, atmospheric deposition unrelated to roads, and groundwater inputs. Additionally, direct discharges not mediated by runoff processes, such as illegal dumping or point-source industrial effluents, are excluded. Temporal boundaries align with annual aggregation of pollutant loads to capture seasonal variability and cumulative impacts.