Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
Center for Water Quality Research (CWQI), Institute for Environmental Research (IER), Tehran University of Medical Sciences, Tehran, Iran.
Biol Trace Elem Res. 2019 Apr;188(2):514-520. doi: 10.1007/s12011-018-1422-y. Epub 2018 Jun 29.
Heavy metals are a group of pollutants in biological sludge. Many agencies regulated guidelines for heavy metal concentrations for various applications of sludge such as agricultural application. In this study, we tried to determine heavy metal fate after anaerobic digestion. Additionally, we determined the bioaccumulation rate of heavy metals in lettuce cultivated on a sludge-applied land. Heavy metal (As, Pb, Hg, Cd) contents of solid and liquid parts of raw and anaerobically digested sludge were separately measured by ICP-OES. For this purpose, the samples were digested using nitric acid, hydrochloric acid, and boric acid. Then, the raw and anaerobically digested sludge were used for cultivation of lettuce in separate farms. The heavy metal concentrations in the harvested lettuce were measured by the same procedure. The results showed that the main part of heavy metals in the raw sludge was in the liquid part (67%), while, the main part of heavy metals in the anaerobically digested samples was in the solid part of the sludge. Because of washout of dissolved heavy metals in the liquid part of the sludge, the lettuce cultivated by anaerobically digested sludge had higher content of the heavy metals in comparison to that of the lettuce cultivated by the raw sludge. This study showed that application of anaerobically digested sludge can increase the bioaccumulation rate of heavy metals in the crops and induce more human health risk.
重金属是生物污泥中的一类污染物。许多机构都制定了有关污泥各种应用（如农业应用）中重金属浓度的规定指南。在本研究中，我们试图确定厌氧消化后重金属的归宿。此外，我们还测定了在施用过污泥的土地上种植的生菜中重金属的生物累积率。采用电感耦合等离子体发射光谱法（ICP-OES）分别测定原污泥和厌氧消化污泥的固、液部分中的重金属（砷、铅、汞、镉）含量。为此，使用硝酸、盐酸和硼酸对样品进行消解。然后，在单独的农场中使用原污泥和厌氧消化污泥来种植生菜。采用相同的程序测定收获的生菜中的重金属浓度。结果表明，原污泥中重金属的主要部分在液体部分（67%），而厌氧消化样品中的重金属主要部分在污泥的固体部分。由于污泥液体部分中溶解态重金属的洗脱，与用原污泥种植的生菜相比，用厌氧消化污泥种植的生菜中重金属含量更高。本研究表明，施用厌氧消化污泥会增加作物对重金属的生物累积率，并导致更大的人类健康风险。
