Spatial Distribution and Ecological Implications of phenolic and chlorinated pesticides in the drainage systems of Alexandria, Egypt

Anthropogenic activities contribute substantially to the release of toxic organic contaminants into aquatic environments. In the present study, selected organochlorine pesticides (OCPs) and phenolic compounds were investigated in twelve hotspot drainage systems in Alexandria, Egypt. The abundance of organochlorine pesticides across the investigated sites followed the sequence ∑HCHs > ∑CDs > ∑DDTs. Total HCH concentrations ranged from non-detectable levels to 84.0 ng L⁻¹, with an overall mean of 24.1 ng L⁻¹. Concentrations of cyclodiene pesticides (CDs) varied from below the detection limit to 18.52 ng L⁻¹ and averaged 9.36 ng L⁻¹. Meanwhile, total DDT levels ranged from Phenolic compounds, including phenol, dichlorophenol, 3,5-dimethylphenol, and 2,4-dichlorophenol, were also detected in the investigated drains. The average concentration of total phenols was 293.47 µg L⁻¹, with the highest concentration (134.70 µg L⁻¹) recorded at El-Qulaa Drain. Mean concentrations of dichlorophenol, 3,5-dimethylphenol, and 2,4-dichlorophenol were 205.35, 268.67, and 114.63 µg L⁻¹, respectively. Ecological risk assessment based on Toxicity Reference Values (TRVs) revealed that the detected phenolic compounds exhibited varying degrees of ecological concer Results from PCA and HCA indicated marked spatial heterogeneity in the concentrations and distribution patterns of OCPs and phenolic compounds across the sampled sites. The observed clustering patterns suggest that agricultural runoff, industrial effluents, and untreated wastewater discharges are the dominant factors governing pollutant distribution. Consequently, the identified hotspot drains represent important pathways for the transport of organic contaminants into the adjacent Mediterranean coastal environment.