Immobilization of Cd, Pb and Zn through Organic Amendments in Wastewater Irrigated Soils

Abstract

Due to the scarcity of water, raw sewage effluents are often used to irrigate arable suburban soils in developing countries, which causes soil contamination with toxic metals. Soil microorganisms involved in biochemical transformations are sensitive to heavy metals contamination. The study was designed to investigate the effect of organic amendments on the microbial activity of cadmium (Cd), lead (Pb) and zinc (Zn) fractions and their bioavailability in soils contaminated with wastewater irrigation. Three metal contaminated soils under wastewater irrigation were collected, ground, sieved and added to incubation jars. Two organic amendments: wheat straw and chickpea straw, were applied (1% w/w) to the soil before incubation for 84 days at 25 °C. The CO2-C evolution after 1, 2, 3, 5, 7, 10 and 14 days was measured and thereafter was also measured weekly. Soil samples collected at 0, 14, 28, 42, 56, 70 and 84 days after incubation were analyzed for microbial biomass carbon (MBC). Sequential extraction for metal fractionation of samples was carried out collected at 0, 28, 56 and 84 days. Three soils differed significantly in evolved MBC and ∑CO2-C. Chickpea straw addition significantly increased soil MBC as compared to the wheat straw. Organic amendments significantly increased ∑CO2-C evolution from the soils, which was higher from chickpea straw. The addition of crop residues did not affect total Pb, Cd and Zn contents in soils. The concentration of exchangeable, carbonate bound and residual fractions of Pb, Cd and Zn decreased (6–27%), while the organic matter bound fraction increased (4–75%) with straw addition. Overall, the organic amendments improved microbial activity and reduce the bioavailability of toxic metals in wastewater irrigated soils. Furthermore, organic amendments not only reduce economic losses as they are cheap to produce but also minimize human health risks from heavy metals by hindering their entry into the food chain.

Effect of Manure and Compost on the Phytostabilization Potential of Heavy Metals by the Halophytic Plant Wavy-Leaved Saltbush

“…The addition of compost significantly affected the distribution of Cd, Zn, Cu, and Pb in soils in this study. Organic fertilizers have crucial roles in minimizing the bioavailability of Zn, Cu, Pb, and Cd in contaminated soils due to their high CEC and complexing ability [36]. In the current study, compost increased the soil CEC and SOC; on the other hand, it reduced the availability of Zn, Cu, Pb, and Cd.…”

“…Soil characteristics, e. g., clay content, cation exchange capacity (CEC), soil pH, and organic matter (SOC), play important roles in changing heavy metals' bioavailability [35]. The use of organic amendments is another viable option to cultivate crop in soils contaminated with Zn, Cu, Pb, and Cd [36]. The nature and quantity of organic matter in the soil affect many soil properties, e g., there is an increase in the adsorption of Zn, Cu, Pb, and Cd by soil components with increasing amounts of organic matter [37][38][39].…”

Application of sewage sludge combined with thiourea improves the growth and yield attributes of wheat (Triticum aestivum L.) genotypes under arsenic-contaminated soil

“…Among abiotic stresses (i.e., drought, salinity, nutrition), heavy metals contamination deteriorate a large agricultural area [2][3][4][5][6][7][8][9]. Soil metal contamination is widespread worldwide in huge land areas, especially in Asian countries, including Pakistan [10][11][12][13][14][15][16][17][18][19][20]. Arsenic (As) is a toxic metalloid ubiquitously present in the soil at trace quantities normally [21].…”

Application of Zinc Fertilizer and Mycorrhizal Inoculation on Physio-Biochemical Parameters of Wheat Grown under Water-Stressed Environment

“…It has a vital physiological role in protein and enzyme functions associated with essential biochemical pathways, photosynthetic processes, protein synthesis, and enzyme activation. Zinc application increases the photosynthetic rate and chlorophyll content [11][12][13][14] and enhances photochemical reactions in thylakoid membranes and electron transport in PSII [15].…”