论文部分内容阅读
调查分析了两块不同重金属污染水平下的水稻田土壤有机碳活性组分的含量,以评价重金属胁迫条件下有机碳基质的微生物有效性。结果显示,重污染水稻土的总有机碳(TOC)、0·5mol·L-1K2SO4溶解态有机碳(K2SO4-C)、微生物生物量碳(MBC)、1~7d(CO2-C1~7d)和8~28d矿化的有机碳(CO2-C8~28d)的含量均显著低于轻污染土壤(p<0·001)。碳有效性指标中,微生物商(MBC/TOC比)和8~28d的有机碳矿化率(CO2-C8~28d·TOC-1d-1))在轻污染土壤中较高,而K2SO4-C/TOC和代谢商(qCO2)在重污染土壤较高(p<0·001)。1~7d的有机碳矿化率(CO2-C1~7d·TOC-1d-1)在两种土壤中差异不显著。两种土壤培养初期的有机碳矿化率远高于培养后期(p<0·001)。逐步回归分析显示,CO2-C1~7d与活性组分K2SO4-C和MBC显著相关(r2=0·83,p<0·001),而CO2-C8~28d只与TOC显著相关(r2=0·70,p<0·001)。研究表明,尽管K2SO4溶解态有机碳在供试的重金属污染的水稻土中是较易被分解的活性碳基质,但重金属污染抑制了微生物数量及其呼吸活性,降低了活性有机碳库的矿化率,这是导致土壤中K2SO4溶解态碳积累的原因。溶解性有机碳又能提高重金属的有效性,进一步抑制微生物对有机碳的矿化。因此,评价重金属污染的水稻土有机碳的有效性,应当综合考虑不同有机碳库的活性、微生物的矿化能力和碳基质在不同阶段的供应潜力。
The content of soil organic carbon in paddy soils under two different levels of heavy metal pollution was investigated and analyzed to evaluate the microbial bioavailability under heavy metal stress. The results showed that total organic carbon (TOC), dissolved organic carbon (K2SO4-C) and microbial biomass carbon (MBC) of 0-5 mol·L-1 K2SO4 in the heavily polluted paddy soils for 1 to 7 days (CO2-C1 to 7 days) And the contents of mineralized organic carbon (CO2-C8 ~ 28d) in 8 ~ 28d were significantly lower than those in light-polluted soil (p <0 · 001). Among the carbon availability indicators, MBC / TOC ratio and organic carbon mineralization rate (CO2-C8 ~ 28d · TOC-1d-1) of 8 ~ 28d were higher in lightly polluted soils while K2SO4- / TOC and qCO2 were higher in heavily polluted soils (p <0.001). The organic carbon mineralization rate (CO2-C1 ~ 7d · TOC-1d-1) from January to July was not significantly different between the two soils. The organic carbon mineralization rate in the early stages of soil incubation was much higher than that in the later period (p <0.001). Stepwise regression analysis showed that CO2-C1-7d was significantly correlated with K2SO4-C and MBC (r2 = 0.83, p <0.001), while CO2-C8-28d was only significantly correlated with TOC (r2 = 0 · 70, p <0 · 001). The results show that although K2SO4 dissolved organic carbon is a more active matrix decomposable in paddy soils polluted by heavy metals, heavy metal pollution inhibits the microbial population and respiration activity and reduces the mineralization of active organic carbon pools This is the reason that leads to the accumulation of K2SO4 dissolved carbon in the soil. Dissolved organic carbon can improve the effectiveness of heavy metals, further inhibiting the mineralization of organic carbon. Therefore, to evaluate the effectiveness of organic carbon in paddy soil polluted by heavy metals, the activity of different organic carbon pools, the mineralization ability of microorganisms and the potential supply of carbon matrix in different stages should be considered.