多环芳烃在污泥与菜籽饼堆肥中的降解规律

研究了城市污泥和菜籽饼堆肥体系中16种多环芳烃(PAHs)在94 d内的降解演化过程.堆肥体系开始时16种PAHs的总浓度为1.792 mg·kg~(-1),堆肥结束后其总浓度为0.153 mg·kg~(-1).其总降解率为91.5% (p<0.05).堆肥过程中,堆体腐殖酸呈现先上升后下降,最后又稳步上升的趋势;与此同时,PAHs则呈现先下降后上升,最后又明显下降的趋势(第31～61 d).PAHs的微生物降解主要发生在堆肥的第16～31 d,但是苯环数≤3的PAHs降解过程与苯环数≥4的PAHs在堆肥第31～47 d存在差异:苯环数≤3的PAHs(除了菲)存在着一个持续的降解过程,但是苯环数≥4的PAHs和菲在堆肥第31～46 d表现出浓度的上升.这表明苯环数≥4的PAHs和菲存在强吸附作用,它们紧密的吸附使得微生物不易进行生物降解.PAHs化合物降解率与其相对分子质量之间存在正相关的关系,即相对分子质量越大的化合物其降解率越高,苯并(b)荧蒽例外.

Fate of Polycyclic Aromatic Hydrocarbons by Composting of Municipal Sewage Sludge and Rapeseed Meal

The goal of these studies was to determine the fate of 16 polycyclic aromatic hydrocarbons (PAHs) during the 94 days of composting of municipal sewage sludge with rapeseed meal. The total PAHs calculated from the sum of the amounts of the 16 PAHs in the initial mixture of municipal sewage sludge was about 1.792 mg·kg~(-1). Then the content of total 16 PAHs was 0.153 mg·kg~(-1) at the final of composting. The level of total PAHs fell by about 91.5% (p<0.05) at the end of composting. While the content of humic substance increased, the content of PAHs decreased in the intermediate stages (31-61 days) of composting. The treatment by composting led to a decrease of all PAHs mainly in 16-31 d, but some differences could be observed between PAHs with three or fewer aromatic rings (N =3) and those with four or more (N =4). The PAHs with N of three or fewer (except phenanthrene) exhibited a continous decrease, which the PAHs with N of four or more and phenanthrene showed increases between the 31-46 days. This indicates the high potential sorption mainly of PAHs with high molecular weight (N =4) plus phenanthrene, their tight adsorption makes them inaccessible for biodegradation. The high molecular weight PAHs showed a greater reduction of their bioavailability than low molecular weight(except benzob]fluoranthene).