Physicochemical and Microbiological Assessment of Low Rainfall and Extreme Weather Conditions: A Case Study on Tropic of Cancer in Bangladesh

The recent drop in groundwater levels and decreased rainfall alarm the water scarcity and its potential impacts on agriculture, drinking water, and ecological balance, which is growing particularly in Bangladesh's northwest and southwest regions. Rainwater is the most crucial water source in drought-prone areas like the Northwest and Southwestern regions. Under the Tropic of Cancer, three extreme weather regions' rainwater samples were investigated. The microbial load obtained as in Faridpur 3.17×106 CFU/mL, Kushtia 3.31×106 CFU/mL, and Chuadanga 1.51×106 CFU/mL. The highest bacterial growth was investigated in the Kushtia region, and the biggest fungus colony formations were obtained in the Chuadanga and Faridpur region samples. The physicochemical condition of rainwater samples was found most contaminated in the Faridpur region may be due the air pollution by anthropogenic sources. The rainwater of Faridpur was found acidic with a pH of 4.87 and the trace metal Arsenic (As) 0.22 mg/l was recorded as higher than the standard value of both ECR 2023 and WHO. The other sampling region investigated the contamination within tolerable limits (). This type of trace metals and microbial contamination is alarming for the health of that region's civilians. The PCA analysis revealed that TDS, EC, As, and Ca significantly influenced water quality variations across the study sites, with Faridpur exhibiting elevated levels of TDS, EC and As, Kushtia showing the highest Ca concentration, and Chuadanga displaying lower iron concentration with a notable Association with resistivity and Zn; while other trace elements like Mg, Ni, Cr, Hg, Mn, Cu, Pb, Cd forms similar pattern and cluster for three sampling sites. The PCA analysis captures 73.49 % of the variance in PC1 and 26.51 % in PC2. This study highlighted the physicochemical and microbiological pollution of rainwater under the Tropics of Cancer regions, namely Kushtia, Chuadanga, and Faridpur.