Said Muhammad

Soil contamination by potentially harmful elements (PHEs) has become a pressing environmental concern in arid and semi-arid regions, where natural processes and human activities intensify the accumulation of these elements. Understanding the spatial variability, contamination and eco-toxicological implications of PHEs is vital for safeguarding ecosystem integrity, biodiversity and public health. This study highlights the need for a comprehensive analysis of the contamination levels, spatial distribution, potential sources and eco-toxicological status of PHEs in soils across various land-use types in the Sistan Basin, eastern Iran. Soil samples were analyzed for PHEs to assess the contamination factor (C_f), pollution load index (PLI), and ecological risk, supported by spatial mapping and health risk assessment. Results revealed that aluminum (Al) and iron (Fe) were major elements sourced from geogenic origin, whereas cadmium (Cd), arsenic (As), and lead (Pb) exhibited considerable enrichment in agricultural lands and dusty roads due to the use of agrochemicals, fertilizers, vehicle emissions and combustion activities. C_f values indicated low contamination in most sites, while PLI generally revealed low soil pollution levels. Based on Håkanson's classification, Cd was identified as the principal contributor to ecological risk. Health risk assessment revealed ingestion as the primary exposure route, with children being more vulnerable than adults, while non-carcinogenic and cancer risks remained within acceptable ranges, although the health risks in agricultural and dusty road zones suggest potential long-term effects. The integration of contamination indices, geospatial mapping, ecological and health risk underscores the importance of sustainable agricultural practices, regular monitoring and strategic management in conserving soil quality and wetland ecosystems in Sistan.

The Thrace Region of Türkiye hosts diverse lacustrine habitats (LH) that are particularly vulnerable to potentially toxic elements (PTEs). This study investigated 25 PTEs in 33 LH, including 19 irrigation ponds, 12 reservoirs, and 2 natural lakes, across dry and wet seasons. Concentrations varied considerably, with Na and Mg showing the highest levels across all sites and seasons. Seasonal changes were pronounced: several PTEs, including Li, B, Na, and Mg, were strongly diluted during the wet season (up to 99%), while others, such as Cu, Zn, Sr, and Fe, were enriched under these conditions. Ecological risk indices e.g., heavy metal pollution index (HPI < 100) and, heavy metal evaluation index (HEI < 10) indicated generally low contamination levels in the LH, whereas irrigation water quality indices revealed high-risk conditions in Gala and Pamuklu lakes. Human health risk assessment showed that non-carcinogenic risks were within acceptable limits, hazard index (HI < 1) for all age groups, and the carcinogenic risks (CR > 10⁻⁴) slightly exceeded the threshold for children, primarily due to Ni, As, and Pb. Principal component analysis (PCA) explained 72.5% of the total variance and attributed PTEs to three dominant source categories: industrial, agricultural, and geogenic. Cluster analysis further grouped the habitats into three clusters reflecting similarities in their PTE profiles.