آب و فاضلاب (Mar 2019)
Cadmium, Lead and Arsenic Remediation in Urban Wastewater by Sorghum Bicolor L.
Abstract
The use of wastewater and gray water for agribusiness is recently growing, and it is essential to investigate the risks associated with its use. Heavy metals in wastewater, even in small quantities, are among problems limiting the use of wastewater in agriculture. This is due to the high agglomeration coefficient in the environment, degradability and long shelf-life which cause the severity of toxicity and contamination of the soil during irrigation. In this regard, the Phytoremediation technology can be advantageous due to its environmental compatibility and environmental refining power. In order to investigate the power of sweet sorghum, urban wastewater was used to irrigate the plant. First, wastewater was analyzed in terms of 38 factors. By adding cadmium, lead and arsenic to wastewater, three treatments of 0.1, 1 and 10 mg/l of these metals were created in urban wastewater and for 12 weeks the respective pots were irrigated with appropriate replication. Samples of root, stem, leaf, seed, soil and drainage of pots were collected separately for analysis of acid digestion and grafting to the atomic absorption system and the results were compared by statistical methods. The results showed that accumulation of cadmium and lead in sorghum is more than ten times higher than that of arsenic. On the other hand, the absorption coefficient or ability of the plant to absorb the elements has decreased rapidly for cadmium and lead with increasing concentration in the soil. In the case of arsenic, the absorption coefficient increased with increasing concentration in the soil. Regarding the amount of material accumulation, the ability of all tissues in the accumulation of cadmium and lead was the same and in the case of arsenic, the root accumulated more than aerial parts. This study showed that the heavy metals accumulation pattern in sorghum, the final amount of accumulation, the absorption coefficient and its changes relative to the environmental concentration are different for various elements. According to the final concentration of accumulation and absorption coefficient, the sorghum plant is suitable for the purification of cadmium and lead from low concentration effluents which are commonly found in urban wastewater. This can prevent the accumulation of these pollutants in soil.
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