Abstract:
Kasur is a district of Central Punjab in Pakistan. It has long standing tradition of tanning and thus it houses more than 240 tanneries. These tanneries produce huge amount of wastewater which contains different obnoxious heavy metal compounds. Cr based carcinogenic compounds may be especially highlighted in this context because it is the major player in chrome tanning process extensively practiced in Kasur.
The tannery wastewater flooded more than 400 acre of land in the vicinity of the tannery cluster. After the installation of the wastewater pretreatment plant installed to dispose of wastewater, the land has been reclaimed but there yet exists the danger that the heavy metals contaminants which might have penetrated in the soil may ultimate become a part of the food chain because some crops are being grown in this area. The physiochemical analysis of affected soil seemed to be of major concern to assess whether the heavy metal content of the soil was suitable for cultivation of agricultural crops. Thus the goal of the research work undertaken here was to conduct analysis of the contaminated soil to judge its suitability for agriculture.
Physicochemical analysis of the tannery contaminated reclaimed soil was carried out by standard methods. The concentrations of various parameters such as pH, EC, OM, OC, P, K, Na, total metal content for Cr, Cd, Cu and extractable/available metal content for Cr, Cu, Cd, Zn and Fe were determined, computed and compared with the various international standards for agriculture recommended by different international organizations and individual or groups of experts. The results revealed that the concentrations of available/extractable Cu (24.66 mg/kg), Zn (10.11 mg/kg), and Fe (44.80 mg/kg) in agricultural soil are above the safe limits while total metal concentrations of heavy metals (Cr, Cd) are within permissible limits with exception of few areas exceeding the limits. The results for other parameters such as pH, EC, OM, OC, K and Na are in accordance with the prescribed limits but P (7.05-148.61 mg/kg) in soil exceeds the satisfactory range of P in agricultural soil.
Thus, it may be concluded that the reclaimed land area around Kasur tanneries is almost appropriate for agricultural practices. However, the problem of the exceeding limits of extractable/available metals (Cu, Fe, Zn) can be addressed by bringing them within permissible limits by phyto-remediation, cultivating metal hyper-accumulator plants, heap leaching using chemicals or bio-remediation with microbes or manure/sludge.
