污泥中重金属和多环芳烃(PAHs)的存在特性及其相互关系

在深入研究9种不同污水处理厂污泥中重金属存在形态和15种PAHs含量水平的基础上,讨论了污泥中PAHs和重金属含量之间的相互关系.结果表明,生活污水污泥中Zn的含量最高,其次为Cu,而As和Cd含量较低;工业废水污泥中各重金属含量差异较大,制革污泥的Cr含量超过15000 mg·kg-1.污泥中As、Cr、Cu、Pb主要以可氧化态和残渣态存在;Ni和Zn的酸溶态及可还原态的比例较高;Cd在不同污泥中的形态分布变化较大.生活污水和工业废水污泥中∑PAHs的平均含量相差不大,分别为13.74 mg·kg-1和13.95 mg·kg-1.不同污泥中各PAHa呈现4环>3环>2环>5环>6环的分布特征,化石燃料不完全燃烧和石油类污染是污泥中PAHs的主要来源.污泥中低分子量(2环和3环)PAHs与Cd、Ni、Zn等重金属含量存在显著的相关关系,这种相关关系与重金属作用于污泥中的微生物并最终影响微生物对PAHs的降解有关.

The characteristics of heavy metals and PAHs in sewage sludges and their relationships

Polycyclic aromatic hydrocarbons (PAHs) and heavy metals are among the most widespread pollutants found in sewage sludge and impart tremendous potential hazard to human health. Here, we studied the characteristics of PAHs and heavy metals in the sewage sludge from nine different wastewater treatment plants. Zn is the most abundant heavy metal in domestic sewage sludge, followed by Cu, As and Cd. In industrial sewage sludge, the heavy metal profile varies dramatically depending on the source. In tannery sludge, the Cr concentration exceeds 15000 mg·kg^-1. The state of heavy metals in sewage sludge varies as well. Cr, Cu and Pb exist predominantly in oxidizable and residual states; Ni and Zn exist mainly in acid soluble and reducible states, whereas Cd can exist in a variety of states. No significant difference in the total content of PAHs was observed between domestic and industrial sewage sludge. The levels of different PAHs follow a pattern of 4 rings > 3 rings > 2 rings > 5 rings > 6 rings. Fuel spills and incomplete combustion of carbon-containing fuels are the major sources of PAHs in sewage sludge. Our results revealed a correlation between heavy metals (e.g. Cd, Ni, and Zn) and low molecular weight PAHs (e.g. 2 or 3-ring PAHs) in sewage sludge. This correlation may be explained by the influence of heavy metals on the bioactivity of microorganisms that are capable of degrading PAHs.