Influence of chemical fertilizers on arsenic mobilization in the alluvial Bengal delta plain: a critical review

Abstract

Arsenic contamination of alluvial aquifers of the Bengal delta plain causes a serious threat to human health for over 75 million people. The study aimed to explore the impacts of chemical fertilizer on arsenic mobilization in the sedimentary deposition of the alluvial Bengal delta plain. It selected ten comparatively highly affected districts and the least affected two divisions as a referral study site. The countrywide pooled concentration of arsenic in groundwater was 109.75 μg/L (52.59, 166.91) at a 95% confidence interval, which was double the national guideline value (50 μg/L). The analysis results showed a strong positive correlation (r ≥ 0.5) of arsenic with NO3, NH4, PO4, SO4, Ca, and K, where a portion of those species originated from fertilizer leaching into groundwater. The results showed that PO4 played a significant role in arsenic mobilization, but the role of NO3, SO4, and NH4 was not clear at certain lithological conditions. It also showed that clay, peat, silt-clay, and rich microbial community with sufficiently organic carbon loaded soils could lead to an increase in arsenic mobilization. Finally, the study observed that the overall lithological conditions are the main reason for the high arsenic load in the study area. HIGHLIGHTS The groundwater of the Bengal delta basin is highly contaminated with arsenic.; Arsenic significantly correlated with originated fertilizer species: NO3, NH4, PO4, SO4, Ca, and K.; Clayey, peaty, and silt-clay soil with heavy microbial and organic matters enhanced the arsenic mobilization by fertilizers leaching.; Lithological conditions are the major reasons for arsenic toxicity in groundwater.;

Keywords

• aquifer sediment
• arsenic mobilization
• bengal delta plain
• fertilizer leaching
• lithology
• redox reaction