Influences of soil properties on chromium [III] sorption

Soil adsorbing properties reduce sorption ability of the metal, which in turn may influence decision for remediation at contaminated sites. The objective of this study is presentation of a model based on soil properties to estimate the sorption of Cr[III] in chromium contaminated soils. Twenty uncontaminated soil samples, with properties similar to the contaminated soils were selected from around of city of Tabriz and treated with Cr and CrCl[3]. A multiple regression analysis with statgraph software was used to drive an expression that related Cr sorption to common soil properties. The results showed that four soil properties were important in determining the amount of Cr adsorbed by the soils including pH, cation exchange capacity, total inorganic carbon and clay content with nearly 80% variability in Cr sorption and a reasonable level of confidence by this model. The obtained model suggested that Cr[III] sorption was enhanced by higher soil pH, more total inorganic carbon, more clay, and higher cation exchange capacity

Pollution of south of Tehran ground waters with heavy metals

The reuse of nutrients and organic matter in wastewater sludge via on agricultural lands application is a desirable goal. However, trace or heavy metals present in sludge pose the risk of human or phytotoxicity from land application. The aim of this research is possibility of ground water pollution of south of Tehran because of ten years irrigation with Ni, Cd and Pb borne waste water. For this purpose, 6 soil samples from southern parts of Tehran city and 2 ones from Zanjan city without lime and organic matter were selected. The soils differed in their texture from sandy to clayey. Each soil sample in duplicate and uniformly packed into PVC columns. Soil samples were irrigated with Cd, Pb and Ni-added wastewater. After irrigating, the columns were cut and the soils separated from sectioned pieces and their heavy metal concentrations [Pb, Cd and Ni] were measured by atomic absorption spectrophotometer by use of HNO[3] 4N solution. Because of high sorption capacity of these elements by soils, these metals were accumulated in surface layer of the soils. Movement in the soils without lime and organic matter were as low as other samples. Ni has had the most accumulation or the least vertical movement, and Pb the opposite ones

Using different amendments to reduce heavy metals movement in soils

With long-term use of sewage waste, heavy metals can accumulate to phytotoxic levels and resulted in reduced plant growth and/or enhanced metal concentrations in plants, as a result food chain. If these metals penetrate too rapidly in a particular soil, especially with high water table, they can pollute ground water supplies. The aim of this research is prevention of movement of waste water-borne heavy metals in soils of southern parts of Tehran. These waste waters are used for irrigation of agricultural lands at southern regions since many years ago. For this purpose, 6 soil samples from southern parts of Tehran city and 2 ones from Zanjan city without lime and organic matter were selected. In laboratory, sorption capacities of the soils for Ni, Cd and Pb were compared with those of calcite, Na-bentonite, zeolite, illite and hematite amendments. The method was carried out by equilibration of known quantities of these adsorbents and soils with solutions containing these elements. The results showed that among the 5 amendments, calcite and Na-bentonite had the greatest sorption percentages of the 3 elements and illite had the least one. The retention capacity of calcite and Na-bentonite for Cd was highest in all 8 soils. However, retention capacities of these 2 minerals for Pb and Ni were higher than those of loamy soils without lime and organic matter and also sandy soils. Because of abundance and low price of calcite, this amendment is preferred to Na-bentonite. Therefore, calcite is recommended for adding to soils with low sorption capacity of Ni, Cd and Pb