The effect of the herbicide diuron on soil microbial activity

The inhibitory effect of the herbicide diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] on microbial activity in red Latosol soil was followed using microcalorimetry. The activity of the micro-organisms in 1.50 g of soil sample was stimulated by addition of 6.0 mg of glucose and 6.0 mg of ammonium sulfate under 35% controlled humidity at 298.15 (+/- 0.02) K. This activity was determined by power-time curves that were recorded for increasing amounts of diuron, varying from zero to 333.33 micrograms g-1 soil. An increase in the amount of diuron in soil caused a decrease of the original thermal effect, to reach a null value above 333.33 micrograms g-1 of herbicide. The power-time curve showed that the lag-phase period and peak time increased with added herbicide. The decrease of the thermal effect evolved by micro-organisms and the increase of the lag-phase period are associated with the death of microbial populations caused by diuron, which strongly affects soil microbial communities.     

腐殖酸对低浓度百菌清的缓释增效作用

【目的】 明确腐殖酸对低浓度（5 mg·L ^-1）百菌清（chlorothalonil）的缓释增效作用,为减少农药使用量、延长农药药效提供新的科学思路,为选择新的农药增效剂提供理论依据。【方法】 将腐殖酸（50 mg·L ^-1）添加至低浓度百菌清中,进行尖镰孢（Fusarium oxysporum）的体外平板及液体培养,通过菌丝体生长试验及血球计数板、等温微量热技术,测定相应的抑菌率（inhibition rate,IR）、孢子体数量以及生长代谢过程中的热量排放。【结果】 将对照抑菌率设定为0,腐殖酸-百菌清复配处理较百菌清处理的IR显著提高了10.29%（P<0.05）,相对增效达到25.33%。液体摇菌培养过程中,摇菌培养的第3天,百菌清处理与腐殖酸-百菌清复配处理的孢子数无显著差异;摇菌培养第7天,百菌清处理的孢子数极显著低于其他处理（P<0.01）;摇菌培养的第14天,腐殖酸-百菌清复配处理的孢子数显著低于其他处理（P<0.05）,而百菌清处理与对照之间无显著差异,表明腐殖酸延长了低浓度百菌清对尖镰孢孢子数增加的抑制效应。各处理的热功率-时间曲线图显示,腐殖酸-百菌清复配处理热量排放曲线在监测的72 h内未检测到热排放峰;而单独添加百菌清的处理在试验的后期重新出现热排放峰;单独添加腐殖酸处理的热排放曲线与对照曲线接近。对热功率-时间曲线相关参数进一步分析,结果显示百菌清处理的P_max（最大热功率）显著低于对照和腐殖酸处理（P<0.05）,而T_max（最大热功率时间）显著高于对照和腐殖酸处理（P<0.05）;腐殖酸-百菌清复配处理的P_max、Q（整体发热量）、k（生长速率常数）均显著低于其他处理（P<0.05）,表明该处理病原菌的生长代谢活性显著低于其他处理,即病原菌生长代谢受到抑制的程度最大;腐殖酸处理与对照曲线各参数之间无显著差异,表明病原菌的生长代谢活性没有受到抑制,同时说明腐殖酸-百菌清复配处理中生长代谢受到的抑制作用与腐殖酸本身无关。【结论】 添加腐殖酸可以显著提高低浓度百菌清对尖镰孢菌丝体生长、孢子体数量增加以及生长代谢过程中能量排放的抑制能力。将腐殖酸作为低浓度百菌清的农药增效剂,是降低百菌清用量及延长百菌清药效的有效措施。     

异丙基黄原酸钠和Pb~(2+)对土壤微生物活性的影响

通过微量热技术研究重金属铅(Pb2+)和异丙基黄原酸钠对土壤微生物活性的影响,配制不同浓度的Pb(NO3)2和异丙基黄原酸钠溶液,并且进行正交组合,设计8个样品组和一个空白对照。Pb2+浓度越高对土壤微生物的抑制性越强,Pb2+浓度为0.6 g/kg时抑制率I为15.51%,Pb2+浓度为1.2 g/kg时抑制率I为36.21%。反应前期异丙基黄原酸钠对土壤微生物的抑制率也随着浓度升高而增加,反应后期异丙基黄原酸钠对土壤微生物的影响降低。两种物质同时存在比单一物质的抑制性强,在铅浓度一定的条件下,高浓度的异丙基黄原酸钠会促进微生物放出更多的热量。     

家兔肝脏线粒体微量量热研究——腐植酸对线粒体代谢热谱的影响

利用ＬＫＢ－２２７７生物活性检测系统测定了家兔肝脏线粒体正常代谢的谱及腐植酸对其代谢热谱的影响，发现线粒体从细胞分离出来来后具有一定活性，可存活较长一段时间，其代谢热谱与细菌热谱相似，可分为抑制期，恢复期，稳定期和衰蝎期，腐植酸对线粒体热谱有较大的影响可使产热提前，产热最高峰增大，总产热量增加，探讨了腐植酸影响线粒体产热的原因。     

细菌生长热谱影响因素研究

以LKB-2277生物活性监测系统研究了细菌生长热谱图的影响因素。结果表明，测量温度、培养基、测量方法及供氧状况明显影响细菌生长热谱图的形状，而菌液浓度和存放时间对热谱的影响较小。因此，要从细菌生长热谱中获得细菌代谢的准确信息，必须研究测定的条件。     

植物激素与金属离子对稻种萌发影响的热动力学研究

用自研制的热导式微热量计测定了水稻杂交新品种马协雄性不育系稻种在植物激素和金属离子介质中萌发热功率-时间曲线,获得了该稻种在不同介质中萌发各产热阶段的热数据。计算了马协雄性不育稻种在不同介质中萌发生长动力学参数,建立了相应的动力学经验式。并进一步探讨了激动素(KT)和生长素(IAA)及Zn~(2 )”和Cu~(2 )对稻种萌发过程的影响。     

细菌生长速率与温度关系的微量热法研究

以ＬＫＢ－２２７７生物活性监测系统研究了细菌生长速率与温度的关系。结果表明，在所研究的温度范围内，细菌生长速率与温度之间的关系并不能很好地遵守Ａｒｒｈｅｎｉｕｓ方程。     

等温微量热技术在土壤与环境科学中的应用

Isothermal microcalorimetry provides thermodynamic and kinetic information on various reactions and processes and is thereby a powerful tool to elucidate their mechanisms. Certain improvement in isothermal microcalorimetry with regard to the studies on soil and environmental sciences is briefly described. This review mainly focuses on the use of microcalorimetry in the determination of soil microbial activity, monitoring the toxicity and biodegradation of soil organic pollutants, the risk evaluation of metals and metalloids, the heat effect of ion exchange and adsorption in soil, and environmental researches. Promising prospects for the applications of the technique in the field are also discussed.     

通过微量量热法研究Cd2+在针铁矿上的吸附机制

A study on energy changes and mechanisms of Cd sorbed on goethite was performed using the technique of microcalorimetry.The data of the amount of Cd sorpion(Aq) and concentration of Cd in equilibrium solution(Ce),and the data of Aq and the heat effect(AH) caused by Cd^2 sorption on goethite all fitted Langmuir isotherm.The amount of heat released from Cd sorption on goethite increased with the amount of Ce or Aq.The reaction process of Cd sorption on goethite may be divided into five stages and three plateaus,depending on the variation of enthalpy change(ΔaHm) of Cd sorption with Aq,which implied three mechanisms of interaction between Cd and goethite.The experimental results showed that the microcalorimetry may be useful for determination of microcalorie variation in soil.