土壤溶解性有机质的生态环境效应

土壤生态环境是一个复杂的多介质多界面体系。现有的研究表明，DOM作为环境中重要的天然配位体和吸着载体，是一种非常活跃的化学物质，它将土壤中的矿物质、有机质与生物成分联系在一起，通过物理或化学作用改变金属与外源性化合物的环境行为，促进温室气体的排放，调节土壤养分流失，指示土壤质量，并对成土过程、微生物的生长代谢过程、土壤有机质分解和转化过程有着重要作用，已经成为土壤科学、生态科学和环境科学交叉领域的研究热点。文章系统地评述了DOM的组成特点及其环境效应，同时介绍了未来的研究方向及一些有待于进一步研究的问题。     

乙烯菌核利在水溶液中的光解动力学

以高压汞灯和太阳光为光源，研究乙烯菌核利在重蒸水、自来水、湖水及pH缓冲液中的光解动力学。高压汞灯下，乙烯菌核利在重蒸水中的光解半衰期约为28min，而在太阳光下为3．86h。自来水和湖水中溶解性物质对乙烯菌核利在高压汞灯下的光解动力学仅有微弱的淬灭效应，但在太阳光下表现出显著的敏化效应，照光3h的敏化效率分别为138％和126％。2种光源下，pH5．0和pH7．0缓冲液对乙烯菌核利的光解均表现为光淬灭效应，高压汞灯照光60min的淬灭效率分别为69％和57％，太阳光照光7h的淬灭效率分别为77％和33％；pH9．0缓冲液则表现出显著的敏化效应，高压汞灯照光20min的敏化效率为58％，而太阳光照光1h的敏化效率则达到了415％。     

邻苯二甲酸二丁酯对大型蚤(Daphnia magna)的毒性作用研究

本研究选用大型蚤(Daphnia magna)作为实验生物,研究了邻苯二甲酸二丁酯(DBP)对其急性毒性作用和慢性毒性作用,同时还研究了环境因素(温度、硬度、腐殖酸)对DBP24h-EC(50)的影响.结果表明DBP对大型蚤的24h-EC_(50)为10.35mg·1~(-1),温度、硬度和腐殖酸对DBP24h-EC_(50)均有一定影响.DBP对大型蚤的捕食行为产生抑制,EC_(50)在 6—7mg·1~(-1)之间.慢性毒性实验结果表明DBP对大型蚤的生长繁殖产生一定影响,低浓度DBP对大型蚤生长繁殖有一定的刺激作用,高浓度DBP对大型蚤生长繁殖存在抑制作用,BDP的最大允许安全浓度为1—2mg·1~(-1).     

广西土地利用变化及对粮食生产的影响

在统计软件SPSS支持下,深入分析了广西土地利用现状及1996—2001年土地利用结构变化的原因,在此基础上探讨了土地利用变化对粮食生产的影响,并提出了一些保障粮食安全的对策及建议。     

Co-present Pb(II) accelerates the oxidation of organic contaminants by permanganate: Role of Pb(III)

• Simultaneous removal of organic contaminants and Pb(II) was achieved by Mn(VII). • Pb(II) enhanced Mn(VII) oxidation performance over a wide pH range. • Pb(II) did not alter the pH-rate profile for contaminants oxidation by Mn(VII). • Mn(VII) alone cannot oxidize Pb(II) effectively at pH below 5.0. • Pb(III) plays important roles on enhancing Mn(VII) decontamination process. The permanganate (Mn(VII)) oxidation has emerged as a promising technology for the remediation and treatment of the groundwater and surface water contaminated with the organic compounds. Nonetheless, only a few studies have been conducted to explore the role of the heavy metals (especially the redox-active ones) during the Mn(VII) oxidation process. In this study, taking Pb(II) as an example, its influence on the Mn(VII) decontamination performance has been extensively investigated. It was found that, with the presence of Pb(II), Mn(VII) could degrade diclofenac (DCF), 2,4-dichlorophenol, and aniline more effectively than without. For instance, over a wide pH range of 4.5–8.0, the dosing of 10 μmol/L Pb(II) accelerated the DCF removal rate from 0.006–0.25 min⁻¹ to 0.05–0.46 min⁻¹ with a promotion factor of 1.9–9.4. Although the UV-vis spectroscopic and high resolution transmission electron microscopy analyses suggested that Mn(VII) could react with Pb(II) to produce Mn(IV) and Pb(IV) at pH 6.0–8.0, further experiments revealed that Pb(II) did not exert its enhancing effect through promoting the generation of MnO₂, as the reactivity of MnO₂ was poor under the employed pH range. At pH below 5.0, it was interesting to find that, a negligible amount of MnO₂ was formed in the Mn(VII)/Pb(II) system in the absence of contaminants, while once MnO₂ was generated in the presence of contaminants, it could catalyze the Pb(II) oxidation to Pb(IV) by Mn(VII). Collectively, by highlighting the conversion process of Pb(II) to Pb(IV) by either Mn(VII) or MnO₂, the reactive Pb(III) intermediates were proposed to account for the Pb(II) enhancement effect.     

活性炭吸附回收高含量油气的研究

利用3种活性炭吸附分离汽油蒸汽和空气的混合气,研究了其吸附回收油气的动力学、热力学性能.活性炭ACl、AC3在20℃时的吸附容量分别为0.295 g/g、0.189 g/g,30 ℃时为0.284 g/g、0.165 g/g.活性炭吸附高含量油气时,吸附热高,如吸附油气摩尔分数为0.3 mol/mol时,吸附床温升达50～60 ℃.活性炭导热系数为0.15～0.20 W/m·℃,吸附过程可视为绝热吸附.建立了活性炭吸附油气热效应估算式,可用来评价活性炭吸附容量、进料油气摩尔分数、油气回收率与活性炭温升的关系.活性炭解吸宜先采取真空解吸,在解吸后期适当加入微量微热空气吹扫而深度脱附.解吸操作压力应低于1 kPa,解吸时间可控制在60 min内,热空气温度宜控制在50℃以下.油气吸附分离方法将主要用作其他分离方法的深度处理,以确保油气回收设备尾气达标排放.     

Probabilistic approaches in the effect assessment of toxic chemicals. What are the benefits and limitations?

There is an ongoing discussion whether in the environmental risk assessment for chemicals the so called 'deterministic' approach using point estimates of exposure and effect concentrations is still appropriate. Instead, the more detailed and scientifically sounder probabilistic methods that have been developed over the last years are widely recommended. Here, we present the results of a probabilistic effect assessment for the aquatic environment performed for the pesticide methyl parathion and compare them with the results obtained with the common deterministic approach as described in the EU Technical Guidance Document. Methyl parathion was chosen because a sufficient data set (acute toxicity data for about 70 species) was available. The assumptions underlying the probabilistic effect assessment are discussed in the light of the results obtained for methyl parathion. Two important assumptions made by many studies are: (i) a sufficient number of ecologically relevant toxicity data is available, (ii) the toxicity data follow a certain distribution such as log-normal. Considering the scarcity of data for many industrial chemicals, we conclude that these assumptions would not be fulfilled in many cases if the probabilistic assessment was applied to the majority of industrial chemicals. Therefore, despite the well-known limitations of the deterministic approach, it should not be replaced by probabilistic methods unless the assumptions of these methods are carefully checked in each individual case, which would significantly increase the effort for the assessment procedure.     

西南喀斯特流域岩溶水氢氧同位素时空分布特征及水文意义——以后寨河流域为例

受多重导水介质影响,喀斯特流域水循环过程复杂,只以水分为研究对象的水文学方法难以刻画其时空变化特征及其受喀斯特水文地质条件的控制作用。稳定氢氧同位素赋予岩溶水指纹信息,为解译喀斯特流域水循环时空演变与水文功能提供了重要研究手段。论文选取贵州普定后寨河流域为研究对象,基于月尺度的高空间分辨率的水样采集,结合聚类分析和克里金插值方法,分析流域岩溶地下水氢氧同位素和反映蒸发分馏程度的Lc指数时空分布特征及其影响因素。以此为基础,研究喀斯特流域降雨混合、水文连通性及水流路径等水文作用。结果表明,研究区雨季岩溶地下水δ¹⁸O与Lc偏负,枯季岩溶水整体δ¹⁸O与Lc相对偏正,表明雨季湿热条件下,岩溶地下水受“新”、“老”水混合作用与流域蒸发过程的共同影响,枯季地下水混合作用较弱,蒸发作用弱;相较于中下游覆盖型岩溶区,流域上游峰丛区岩溶水δ¹⁸O偏负,Lc偏正,表明流域上游土壤/表层岩溶带浅薄山区,降雨入渗迅速,岩溶水中土壤水成分较低,下游土壤较厚,入渗较慢且蒸发强烈,地下水蓄存时间长,岩溶水中土壤水成分较高。干湿交替期,岩溶水Lc快...     

中国清洁电力发展对二氧化碳排放的空间效应及影响路径研究

有关清洁电力是否有效降低二氧化碳排放,有两种不同观点,本文分析了产生争议的原因,并基于机理分析,选取1998—2018年中国30个省份的相关数据,利用空间面板杜宾模型研究清洁电力发展对区域二氧化碳排放的影响。回归结果显示：(1)二氧化碳排放在省域之间具有显著的正向空间溢出效应。(2)清洁电力发展与二氧化碳排放之间呈倒U形关系并通过了一系列稳健性检验。(3)进一步地通过效应分解发现,清洁电力发展无论是直接效应还是间接效应,均需要达到一定的门槛值之后才会对区域二氧化碳排放产生促减效用。最后,通过中介效应模型检验发现,清洁电力发展带来的能源消费结构调整和能源利用效率改变是影响二氧化碳排放的作用机制。     

衍生T形槽干气密封稳态性能研究

目的 设计具备双向旋转特点的动压型干气密封端面结构,并展现良好的开启性能,以T形槽为优化对象,衍生出一种新型槽型结构。方法 借助有限元软件,计算并对比经典T形槽与衍生槽型在流场特性和稳态性能方面的差异,探讨不同参数对2种槽型干气密封稳态性能的影响规律,揭示衍生槽型的密封机理。结果 衍生槽型的开启力高于经典T形槽,泄漏率也会增加。随着工况参数的升高,2种槽型的稳态性能参数近似线性增加,且差异逐渐增大,最小差异达到6.6%。随着槽深的增加,泄漏率方面的差距在逐渐减小,为扩大衍生槽型的控漏效果,槽深应>5μm。开设有引流槽型结构的衍生槽型稳态性能顺序为发散型>直口型>收敛型,但在文中的工况下,数值差别较小,最大仅为1.2%。结论 相比于经典T形槽,衍生槽型具有更强的动压效应,开启性能明显提升。另外,通过开设不同形式的引流槽可以改变气膜的流动特性和干气密封性能。