Spatial Changes in Soil Organic Matter and Waste Elements in Contaminated Agricultural Fields at Anthropogenically Transformed Areas within the East Calcutta Wetlands Ecosystem

Abstract

Physical and chemical properties of soil were compared between different agricultural fields of multi-metal waste contaminated East Calcutta Wetlands (ECW) sites and uncontaminated control study sites. Soil organic matter (SOM) contents were significantly different between contaminated ECW and control sites. Agricultural fields at ECW sites were characterized by higher contents of SOM, porosity, moisture, particle size (sandy >63 µm) and metals; while the control sites had higher bulk density, pH and electrical conductivity (EC). Metal accumulation in soils of ECW showed the trend Fe>Zn>Mn>Cr>Pb>Cu; while at control sites like Fe>(Zn=Mn)>Cr>(Pb=Cu). Post-Hoc analyses (with Tukey HSD) clearly pointed out site-wise significant differences (at p<0.05) in soil metal contents between ECW and control sites. The results of this study pointed out the importance of chelates like SOM and easily biodegradable organic acids in the waste contaminated soils of ECW to arrest metals in significant amount reducing phytoavailability and, thereby, sustained agricultural practices at the concerned areas without any health hazard for nearly a century.