Assessment of water quality degradation, ecological stress, and associated risks in aquatic ecosystems exposed to cigarette manufacturing effluents

Abstract

Aquatic contamination is a growing global concern due to rapid agricultural and industrial expansion. This study quantified the impacts of tobacco-manufacturing effluents on adjacent aquatic ecosystems and assessed the associated ecotoxicological risks to aquatic biota using integrated multi-index approaches. A total of 12 effluent samples were collected from a tobacco industry, along with 48 water samples from industry-adjacent crop fields (ICFs) and non-tobacco crop fields (NCFs) across four sampling campaigns conducted during the before cropping season (BCS) and after cropping season (ACS). All samples were analyzed for 28 parameters. The results demonstrated that during ICF-ACS, turbidity (94.61 ± 28.21 NTU), TSS (132.67 ± 24.40 mg L⁻¹), COD (269 ± 79.88 mg L⁻¹), BOD₅ (153 ± 59.33 mg L⁻¹), NO₃–N (18.87 ± 4.87 mg L⁻¹), PO₄–P (3.21 ± 1.12 mg L⁻¹), and major heavy metals frequently exceeded aquatic ecosystem quality (AEQ) guidelines. The chloro-alkaline indices (CAI-1 and CAI-2) indicated relatively stable ion-exchange conditions across the studied aquatic ecosystems. The water quality and health indices illustrated that values declined up to 321% from BCS to ACS, shifting suitability from ‘good’ to ‘extremely poor’, with 1.56 to 2.54-fold greater degradation in ICF waters than in NCF waters. Similarly, toxicity increased by 94.7% in ICFs compared with 52.8% in NCFs, and the Potential Ecological Risk (RI) rose to the ‘very high risk’ category, nearly doubling in ICFs. Hazard Quotient (HQ) analyses identified Cd, Ni, Cr, and Pb as priority contaminants in ICF waters, posing significant risks to aquatic organisms. Tobacco-manufacturing effluents significantly impaired water quality and elevated ecotoxicological risks. Implementing effective pre-discharge treatment can mitigate these impacts and safeguard the health of adjacent aquatic ecosystems.