Soil properties and pollution indices in four designated wetlands in the Sylhet basin of Bangladesh

摘要

A study was conducted on 16 sites in four Ramsar designated wetlands soils regarding soil properties and pollution indices in the Sylhet basin of Bangladesh. The wetlands sites' soil quality remained favorable for agricultural sustainability. Arsenic and cadmium contents were found at minimum detection levels. Rubidium and zirconium were found below critical levels. Pollution indices revealed that zinc and titanium content is slightly higher than the other elements. It was observed that Fe, Ti, Zr, and Mn originate from natural sources or sediments. In contrast, Zn and Cu originate from the artificial fertilizer sources used in and around agricultural lands of the wetland bodies. Moreover, the wetlands are used only for Boro rice crop, and for most of the year, they remain fallow. As a result, grazing activities are predominant. It is assumed that Cu and Zn are often used as additives for animal feed and enter animal wastes through incomplete absorption, and thus, the application of animal wastes in agriculture causes pollution with Zn and Cu. Pollution load index revealed that 42 of the study sites were polluted and 58 remained unpolluted. Principal component analysis and enrichment factors show that anthropogenic activities are responsible for the current pollution, where Zn and Cu predominate. The wetland sites are being polluted at a minor level. The main reasons for the higher level of metal pollution in Balai wetland might be its geomorphic nature and even anthropogenic activities. This wetland is located at the junction point of the Surma-Kushiyara River in Bangladesh, where an international river, Barak, intersects there, which originated from the upper territory. It is urgent to formulate an integrated action plan to prevent the source points of pollution.