重金属影响下有机物料分解与转化的研究

Effect of Heavy Metals on Decomposition and Turnover of Organic Materials

通过室内培养实验,初步研究了重金属Cd、Pb影响下,猪粪和玉米秸秆在土壤中的分解与转化规律。结果表明:添加重金属后,有机物料的分解与转化和有机物料种类、用量以及重金属类型有关。一般来看,与不添加重金属的非污染土相比,有机物料低用量(1%用量)条件下,单加Cd有抑制其分解的趋势,单加Pb则有促进其分解的趋势,同时加Cd、Pb也有抑制其分解的趋势;而高用量(5%用量)条件下,无论单加还是同时加Cd、Pb都有抑制其分解的趋势。有机物料低用量时更有利于胡敏酸(HA)形成,而高用量时则更有利于富里酸(FA)形成。有机物料低用量使HA、FA的分子结构都变得复杂化。从环境保护和提高经济效益两方面综合考虑,重金属污染土壤中有机物料施用量不宜过高。

A submerged incubation experiment was carried out to study the effect of the Cd or Pb application on decomposition and turnover of two organic materials（a pig manure （PM） and a corn stalk （CS）） in soil. The soil was sampled from a bottom layer of meadow soil,it was soaked in aqueous CdCl2·2.5H2O （Cd）, Pb （NO3）2 （Pb） or combined CdCl2· 2.5H2O and Pb （NO3）2 （Cd ＋Pb） solution for 14 d before organic materials application. The added concentration of Cd and Pb was 50 mg/kg and 500 mg/kg, respectively. Organic carbon content of total soil, humic acid （HA）, fulvic acid （FA）, and optical property （Alogk = logE400- logE600） of HA, FA were determined. The results showed that the decomposition and turnover of organic materials was relative to the application type and level of organic materials and heavy metals. In general, when compared with uncontaminated soil without heavy metals application, the decomposition of organic materials was restricted by the addition of Cd or Cd＋Pb, but it was accelerated by the addition of Pd under lower application level of organic materials; whereas the decomposition of organic materials was all restricted by the addition of both alone Cd, Pb and combined Cd＋ Pb under higher application level of organic materials. It was more beneficial to the formation of HA under lower application level of organic materials. The molecular structure of both HA and FA became more complicated under lower application level of organic materials. It was concluded that the amount of organic materials added should not be very high.