Atmospheric wet deposition of trace elements in Bangladesh: A new insight into spatiotemporal variability and source...

The interaction between water vapor and natural/anthropogenic airborne particles deposits a massive amount of trace elements in the ecosystem. As the principal source region of the Indian monsoon originated from the Bay of Bengal, atmospheric trace elements in Bangladesh have impacted atmospheric wet deposition along the pathway, even reaching the headwaters in the Asian water tower. However, no study reports the atmospheric wet deposition of trace elements at the spatiotemporal scale. Thus, this study investigated the concentration, sources, and deposition of eighteen trace elements (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Rb, Sr, Mo, Cd, Sn, Sb, Ba, and Pb) from 232 precipitation samples at four sites in Bangladesh. Results showed that the VWM concentrations of the eighteen measured trace elements ranged from 0.03 to 535.6 μg L^-1. Zn, Fe, and Al were the principal elements of the atmosphere at four sites with mean values of 207.9 ± 227.8, 18.2 ± 9.3, and 16.3 ± 6.8 μg L^-1, respectively. Besides, the eighteen trace elements showed significant variation in spatial scale with distinct seasonality. Enrichment factors of Zn, Sb, and Cd indicated serious anthropogenic influences. The major sources of trace elements were fossil fuel combustion, brick kilns, crustal dust, fugitive Pb, metal smelters, and battery recycling. Both the concentration and precipitation amount played a pivotal role in the deposition. Most of the air masses during the monsoon season came from marine sources passing over southern India and Sri Lanka. Meanwhile, the air masses during the non-monsoon season were from West Asia and the northwestern Indian subcontinent. The air masses are transported over a long range and deposit massive amounts of particulate matter in the Third Pole Himalayan region. This first-hand work on spatiotemporal variation provides a reference dataset for future targeting of the scientific community and policymakers for the development of strategies and action plans.