Barajas-Aceves M, Corona-Hernández J, Rodríguez-Vázquez R
Department of Biotechnology and Bioengineering, CINVESTAV-IPN, Av. IPN 2508, San Pedro Zacatenco C.P., 07300 México, D.F., Mexico.
J Hazard Mater. 2007 Jul 19;146(1-2):91-7. doi: 10.1016/j.jhazmat.2006.12.001. Epub 2006 Dec 5.
We studied Cr fractionation in three semi-arid soils (cultivated, under-the-canopy, and outside-the-canopy soils). The soils were amended with: Cr3+, Cr6+, tannery sludge, Cr3++tannery sludge, and Cr6++tannery sludge and all soils were incubated for 30 and 120 days at 25 degrees C. The Cr in three semi-arid soils was fractionated using sequential extraction (Tessier scheme). Data of Cr fractionation were used to find the correlations with microbial activities determined in previous work. The microbial activities: CO2-C evolved, dehydrogenase activity and nitrification were determined in the same soils amended with the same treatments. Tannery sludge was added at 0.0125 g g(-1) soil and Cr3+ or Cr6+ at 250 microg g(-1) soils. After 120 days of incubation, higher values of concentration of Cr were found in the residual fraction in the three soils amended with all the treatments, except cultivated and outside-the-canopy soils amended with Cr6++tannery. The non-residual fraction tended to decrease with time except in cultivated and outside-the-canopy soils amended with Cr6++tannery sludge. CO2-C evolved was significantly correlated (p<0.05 and p<0.001) with fractions bound to: Mn oxides, Fe oxides organic matter at 30 and 120 days of incubation (from r=0.827 to 0.979). Dehydrogenase activity was correlated with fractions bound to Fe oxides and bound to organic matter, and nitrification with fraction bound to organic matter at 30 days of incubation (r=0.874, 0.959, and 0.803, respectively). These results suggest that even in a sparingly available Cr fraction in semi-arid soils has effect on microbial activities.
我们研究了三种半干旱土壤（耕地土壤、树冠下土壤和树冠外土壤）中的铬分馏情况。这些土壤用以下物质进行了改良：三价铬（Cr3+）、六价铬（Cr6+）、制革污泥、Cr3++制革污泥以及Cr6++制革污泥，所有土壤在25摄氏度下分别培养30天和120天。采用连续提取法（Tessier法）对三种半干旱土壤中的铬进行分馏。铬分馏数据用于寻找与先前工作中测定的微生物活性之间的相关性。在经过相同处理改良的相同土壤中测定了微生物活性：二氧化碳 - 碳释放量、脱氢酶活性和硝化作用。制革污泥的添加量为0.0125 g g(-1)土壤，Cr3+或Cr6+的添加量为250 μg g(-1)土壤。培养120天后，在所有处理改良的三种土壤中，除了用Cr6++制革污泥改良的耕地土壤和树冠外土壤外，其余土壤中铬的残留部分浓度较高。除了用Cr6++制革污泥改良的耕地土壤和树冠外土壤外，非残留部分的含量随时间趋于下降。在培养30天和120天时，二氧化碳 - 碳释放量与结合到锰氧化物、铁氧化物和有机物质上的部分显著相关（p<0.05和p<0.001，相关系数r从0.827到0.979）。在培养30天时，脱氢酶活性与结合到铁氧化物和有机物质上的部分相关，硝化作用与结合到有机物质上的部分相关（相关系数分别为r = 0.874、0.959和0.803）。这些结果表明，即使在半干旱土壤中有效性较低的铬部分也会对微生物活性产生影响。
