Heavy metal and fluoride accumulation in desert shrubs and soil following an industrial wastewater spill: A multi-year assessment in the Ashalim stream, Negev Desert, Israel.

Phosphogypsum spills represent a major environmental risk in arid regions, yet little is known about their long-term ecological legacy after the initial contamination event. This study provides one of the first multi-year assessments of contaminant dynamics following a large phosphogypsum wastewater spill in a protected desert ecosystem. Monitoring conducted two to four years after the 2017 Ashalim Stream spill revealed that cadmium, chromium, and particularly fluoride contamination remained elevated, and in several cases increased, with no evidence of natural attenuation. By 2021, fluoride concentrations in Atriplex halimus leaves were approximately 318 times higher in polluted than in control plants, representing the strongest phosphogypsum-associated contamination signal observed. Species comparisons showed that Atriplex halimus accumulated higher contaminant concentrations than co-occurring desert shrubs, supporting its value as a sensitive, non-destructive biomonitor. Elevated pheophytin concentrations further suggest early physiological responses to persistent contamination. The study also identified contamination at a nominal reference site, emphasizing the challenges of establishing uncontaminated baselines in industrialized arid landscapes. These findings indicate that phosphogypsum spill impacts can persist for years after the initial event and support the use of Atriplex halimus leaf fluoride concentrations as a practical monitoring tool for long-term assessment of contamination in arid environments.