Abstract
This study investigates the spatiotemporal dynamics of industrial toxic chemical discharges within the Coosa River watershed from 2000 to 2020 using the U.S. Environmental Protection Agency's Toxics Release Inventory (TRI) dataset and advanced geospatial techniques. Findings reveal a contrasting trend in reported releases: while total on-site emissions to air, water, and land declined over time, reported surface-water discharges exhibited long-term growth and pronounced temporal variability. Nitrate and zinc compounds were among the most frequently reported chemicals released to surface waters. Emerging Hotspot Analysis (EHSA) and Space-Time Cube analysis identified persistent, intensifying, and newly emerging clusters of reported TRI surface-water discharge activity and facility concentration, particularly near long-established industrial centers around Gadsden. These hotspots reflect statistically significant spatial-temporal patterns in reported TRI discharges rather than measured in-stream contamination, exposure, or ecological impact. Despite overall reductions in reported emissions, the number and proportion of TRI facilities discharging to surface waters remained relatively stable, indicating persistent industrial discharge activity within the watershed. The findings demonstrate the value of TRI-based spatiotemporal analyses as screening-level tools for identifying areas of sustained or emerging industrial discharge pressure. Rather than indicating confirmed water quality impairment, the results provide a spatial framework to support future monitoring, data integration, and hypothesis-driven assessments in flood-prone river systems.