Physical Composition, Nutrients and Contaminants of Typical Waste Dumping Sites

Abstract

Problem statement: The composition of wastes is quite variable depending upon the generating source and mode of collection. Most of the material from the domestic activities will be organic in nature and contains essential plant nutrients, whereas the dumping material of commercial and industrial wastes usually contains appreciable amounts of heavy and potentially toxic metals and organic pollutants. Approach: Objective of the present study was to characterize the physico-chemical properties of the waste material and the distribution and extent of toxic pollutants in three selected typical dumping sites in the state of Haryana, India. Results: 62-65% of the waste fine material consisted of mineral particles and biodegradable organic waste, 20-25% consisted of construction and demolition waste and the remaining 10-15% were other materials such as study, plastic, metals, glass and timber, with an amount of polyethene of 3.4-5.7%. The ratio of the plant available concentrations of P, K and S and their total amounts were 3-7% for P and 1-4% for S, whereas the macronutrient potassium reached values of 29-39%. Metals As, Ba, Cd, Cr, Cu, Ni, Pb and Zn were present in all samples (total concentration in aqua regia extract). As, Ba, Ni and Pb did not show clear differences between the three investigates sites. Cd, Cr and Zn concentrations were high but different at the different sites (Cu maximum: 1,964 mg kg⁻¹, Zn maximum: 2,200 mg kg⁻¹). The mobility of the metals was calculated as the ratio of DTPA/aqua regia extraction. Cd showed the highest ratio (18-22%), while the other calculated metals showed much lower ratios (Cu 6.7, Pb 7.9 Ni 2.1, Zn 3.6 and Cr 0.5%). In general, PAH and benzo(a)pyrene concentrations fell below the detection limit. Also the phenol index did not exceed the detection limit of 1.2 mg kg⁻¹ (with two exceptions). In 14 out of 36 samples a GC-MS screening was conducted in order to get an overview of the organic pollutants usually present in the dumpsites. In all cases there was no relevant amount of organic pollutants that would be capable of measurement. Conclusion: The dumping sites are plant nutrient deposits, particularly for K, which could be used in future in a line with ideas of urban mining. The use of the waste material for fertilizing purposes may be restricted due to the metal contaminant concentrations. The analyzed organic pollutants did not indicate problematical concentrations.