Assessing heavy metal contamination and nutrient status in coastal soils of Bangladesh

Abstract

Heavy metals (HMs) and soil nutrient imbalances pose a significant threat to agricultural productivity in the coastal zones of Bangladesh. This study assessed the spatial variability of essential plant nutrients and heavy metals in soils and explored their interactions with soil acidity and salinity. Thirty-five topsoil samples (0–15 cm) were collected across Kalapara upazila of Patuakhali district, a salinity-affected coastal ecosystem of the Bay of Bengal. The soils were strongly acidic to moderately alkaline (pH 4.3–8.1) and highly saline (mean ECe 9.60 dS m⁻¹). Potassium (K), sodium (Na), calcium (Ca), and magnesium (Mg) concentrations of soils were high to very high, whereas available phosphorus (P) was critically low in more than 90% of samples. Micronutrient analysis revealed very high levels of iron (Fe) and manganese (Mn), and medium levels of zinc (Zn) and medium to high levels of boron (B). Heavy metals such as cadmium (Cd), lead (Pb), and chromium (Cr) were well below the WHO’s threshold limits; however, nickel (Ni) exceeded the permissible level in ~50% of samples, indicating an emerging Ni contamination. Moreover, we observed a strong positive association between HMs (Ni, Cr, Cd) and soil pH, Ca, Mg, B, Zn, Fe, and Mn, whereas EC showed a negative association with Cd. Overall, the soils of Kalapara are constrained by strong acidity, high salinity, and severe P deficiency, while Ni shows  a potential contamination risk in coastal Bangladesh.

J. Bangladesh Acad. Sci. 50(3); 431–445: September 2026