周丛生物腐解驱动水稻土溶解性有机质、铁、磷转化及耦合

周丛生物在稻田土-水界面上广泛存在,可通过多种途径影响土壤养分转化,但其生物质的腐烂分解对土壤中溶解性有机质(DOM)、铁和磷耦合关系的影响尚不清楚。通过开展微宇宙实验向水稻土中添加不同量的周丛生物,利用傅里叶变换离子回旋共振质谱法(FT-ICR MS)表征DOM分子组成,分析周丛生物腐解对水稻土DOM组分、Fe^(2+)含量、氧化铁活化度(Fe_(o)/Fe_(d))、不同形态磷含量的影响。结果表明,周丛生物的腐解显著提高土壤DOM含量,改变DOM不同组分占比,其中,单宁类物质相对丰度增加1.97%~9.74%。同时,土壤Fe^(2+)含量显著增加,Fe_(o)/Fe_(d)升高,土壤还原性增强。此外,土壤无机磷含量增加,其中,磷酸铁盐(Fe-P)变化幅度最大,土壤磷的有效性增加。周丛生物腐解改变土壤DOM组分和铁形态,而DOM中单宁类物质等惰性组分可以通过影响矿物对磷的吸附来影响磷的有效性。主成分分析(PCA)结果表明,添加周丛生物腐解处理与对照之间DOM含量、单宁类物质相对丰度、磷酸铝盐(Al-P)含量、Fe^(2+)含量和Fe_(o)/Fe_(d)等指标存在显著差异。相关性结果表明,Fe^(2+)含量与Fe-P含量、Fe_(o)/Fe_(d)与Al-P含量之间呈显著正相关,且单宁类物质相对丰度与Fe_(o)/Fe_(d)和Al-P之间呈显著正相关,土壤DOM组分、铁形态及磷形态之间相互影响,其中,单宁类DOM增加和铁形态的转化都对土壤磷有效性增加有积极影响。上述结果揭示周丛生物腐解对土壤DOM、铁、磷耦合关系的影响,为利用周丛生物调控土壤碳、铁、磷耦合过程,提高土壤中磷的有效性提供理论支撑。

Mutagenicity and Induction of Drug-metabolizing Enzyme Activity by LPG Combustion Particulates in Rats

Methylene chloride extracts of particulates from liquefied petroleum gas (LPG) combustion appliance were studied by using Ames test, micronucleus test and inducibility of pulmonary and hepatic aryl hydrocarbon hydroxylase (AHH) and glutathione S-transferase (GST) in rats. The extracts showed mutagenicity for Salmonella typhimurium strain TA98 and its derivatives TA98NR and TA98/1,8-DNP6 with or without S9 mix. The revertants in strains TA98NR and TA98/1,8-DNP6 were less than 40% and 50% of that in strain TA98 without S9 mix, respectively. Positive results were obtained in mouse bone marrow micronucleus assay. Intratracheal instillation of the extracts led to increase in pulmonary (but not hepatic) AHH and GST activities in rats. It was seen that AHH was more sensitive than GST to induction by the extracts

Mutagenicity of Urine From Individuals Exposed to LPG Combustion Products

The mutngenicity of urine from individua1s exposed to the combustion products of liquefied petroleum gas (LPG) was detected with Salmonella typhimurium TA98 and its newly developed derivatives YG1021 (nitroreductase overproducing) and YG1024 (O-acetyltransferase overproducing). The detection showed significantly increased mutagenicity for the two YG strains and increased positive rates for all three stralns in the presence of both rat liver S9 and β-glucuronidase. Further analysis demonstrated that urine samples taken from smoking and non-smoking exposed individuals exhibited significantly higher mutagenic potency (revertants/10 μl urine concentrate) than their corresponding controls. These results indicate that the increased urine mutagenicity is caused by the exposure to LPG combustion products or smoking. The mutagenic potency of urine samples of all exposed individuals tested with YG1024 was found to be about 7 times higher than with TA98. The difference in mutagenic potency was smaller for the sarne samples when comparison was made between YG1021 and TA98. This suggests that the mutagenic compounds present in the urine samples contaln mainly arotnatic compounds as glucuronide conugates. our results demonstrate that YG1024 is more sensitive than TA98 in detecting the mutagenicity of these samples. In addition, no significant difference in the mutagenic poency between the' pure' exposed (non-srnokers') and the ' pure' smokers' (unexpeed) samples was found in all three tester strains. This might mean that the exopure extent Of mutagens/carcinogens in LPG combustion products for exmped individuals roughly corresponds to the smoking level of smokers who smoke 20-40 cigarettes per day. Furthermore, the results also suggest that sguergism might exist in the mutagenic effects of exposure to LPG combustion products and cigarette smoking.