Major ions and Nutrients loading by atmospheric wet deposition in Mbeya Urban, Tanzania

Abstract

This study aimed to investigate the contributions of the atmospheric wet depositions to the major ions and nutrient loading in the surface water of Mbeya urban. A total of 22 rainwater samples were collected from six different sampling stations (MUST, Mbalizi, Kabwe, Rufaa, Uyole, and Kalobe) using the rain collector buckets installed 2 meters above the ground from December (18.12.2021) to February (06.02.2022). All the rainwater samples were analyzed for the major ions (Na+, K+, Ca2+, Mg2+, HCO3−, Cl−, CO32−, and SO42−) and nutrients (NH4+, PO43−, and NO3−), pH, and temperature. The pH of the rainwater was found to range from 6.8 to 9.3, indicating that in the region there are emissions of alkaline dust into the atmosphere. The temperature was found to range from 17°C to 22°C, with a mean temperature of 19.77°C. The dominance of the major cations and anions was found in the order of Mg2+> Ca2+>Na+ > K+ and HCO3−> Cl−> SO42−> CO32−ions respectively, and the nutrient dominance sequence followed the order of NH4+>SO42−>NO3−>PO43−. Some parameters showed decreasing trends from one rain event to another, and some showed non–uniformity of the trend among the rain events. The non–uniformity of the trend of the parameters was associated with the point source pollution in the specific sampling stations and the non–uniformity of the rain in the region. Despite the non–uniformity of the trend of the parameters, the results have shown the contributions of the atmospheric wet depositions to the major ions and nutrient loading on the surface. In this regard, to get a clear and representative picture of the pollution status of the Mbeya urban area, major ions and nutrients loaded onto the surface of both wet and dry atmospheric depositions need to be analyzed.