调控pH对于人工湿地中红壤吸附固持锰离子的影响

人工湿地是一项高效的矿山废水重金属污染控制技术。如果能使用当地土壤作为基质,则可以大大降低人工湿地的构建成本。文章比较了不同pH调控措施下红壤对矿山废水中锰离子的吸附效率,并探讨了生物还原作用与植株生长对红壤湿地中锰运移的影响。结果表明:添加碳酸钙比氢氧化钙处理更能显著提高红壤对锰离子的吸附效率。伴随着生物还原作用,红壤土柱间隙水中保持一定的锰浓度,而碳酸钙处理能维持锰离子的吸附固持趋势。在野外红壤基人工湿地中,碳酸钙添加能够显著降低间隙水中锰浓度,但在植株种植与碳酸钙添加共存时,间隙水中锰浓度反而高于对照红壤组。因此,构建处理重金属污染废水的红壤基人工湿地时必须同时优化pH调控与植株种植措施。     

硫酸盐对厌氧生物处理的影响及控制对策

对硫酸盐对厌氧生物处理过程影响机理进行了深入的分析，并由此提出了高浓度硫酸盐废水处理的可行方法及控制对策。     

Anaerobic biodegradation of benzene series compounds by mixed cultures based on optional electronic acceptors

A series of batch experiments were performed using mixed bacterial consortia to investigate biodegradation performance of benzene, toluene, ethylbenzene and three xylene isomers （BTEX） under nitrate, sulfate and ferric iron reducing conditions. The results showed that toluene, ethylbenzene, m-xylene and o-xylene could be degraded independently by the mixed cultures coupled to nitrate, sulfate and ferric iron reduction. Under ferric iron reducing conditions the biodegradation of benzene and p-xylene could be occurred only in the presence of other alkylbenzenes. Alkylbenzenes can serve as the primary subs＇rates to stimulate the transformation of benzene and p-xylene under anaerobic conditions. Benzene and p-xylene are more toxic than toluene and ethylbenzene, under the three terminal electron acceptors conditions, the degradation rates decreased with toluene 〉 ethylbenzene 〉 m-xylene 〉 o-xylene〉 benzene 〉 p- xylene. Nitrate was a more favorable electron acceptor compared to sulfate and ferric iron. The ratio between sulfate consumed and the loss of benzene, toluene, ethylbenzene, o-xylene, m-xylene, p-xylene was 4.44, 4.51, 4.42, 4.32, 4.37 and 4.23, respectively; the ratio between nitrate consumed and the loss of these substrates was 7.53, 6.24, 6.49, 7.28, 7.81, 7.61, respectively; the ratio between the consumption of ferric iron and the loss of toluene, ethylbenzene, o-xylene, m-xylene was 17.99, 18.04, 18.07, 17.97, respectively.     

Variations among rice cultivars on root oxidation and Cd uptake

In order to understand the mechanisms on the variation between rice cultivars in Cd uptake and accumulation, two pot soil experiments were conducted with typical rice cultivars that varied greatly in soil Cd uptake. The experiments with six rice cultivars showed that the root oxidation abilities of rice differed with rice cultivars and also with types of the cultivars, the cultivars with indica consanguinity were significantly higher than the cultivars with japonica consanguinity. Root oxidation abilities of the rice cultivars correlated positively and significantly （P〈0.01） with their Cd concentrations and Cd quantity accumulations in rice plants. The experiments with two rice cultivars showed that significant differences also existed between the two cultivars in pot soil redox potentials, which of Shan you 63 （higher soil Cd accumulator） were significantly higher than that of Wu yun jing 7 （lower soil Cd accumulator） under different soil Cd levels, but the degrees of the differences varied with soil Cd levels. The differences were larger under soil Cd treatments than the control. The results indicate that root oxidation ability, especially in Cd contaminated soil, is one of the main mechanisms which dominate Cd uptake and accumulation by rice plant.     

苦杏仁酸、苹果酸、乳酸对Cr(VI)还原作用的比较

不同温度和pH条件下,通过批式试验研究了苦杏仁酸、苹果酸、乳酸还原Cr(Ⅵ)的反应速率.结果表明,这3种α-OH酸还原Cr(Ⅵ)的能力表现为:苦杏仁酸＞苹果酸＞乳酸.苦杏仁酸对Cr(Ⅵ)的还原作用受pH变化的影响较大,而乳酸受温度变化的影响较大.同时研究了Mn(Ⅱ)对3种α-OH酸还原Cr(Ⅵ)反应速率的影响.结果表明,Mn(Ⅱ)对3种α-OH酸还原Cr(Ⅵ)均有催化作用,其中对苦杏仁酸表现更为明显.     

Fe~0对土壤中硝基苯的还原作用

以恒温培养为方法,GC-MS为检测手段,研究了在常温常压下土壤中硝基苯(NB)在Fe0作用下的还原反应。结果表明:Fe0能将硝基苯苯环上的硝基转化为胺基,从而达到降低毒性、增加可生化性目的。反应条件如时间、零价铁用量、初始pH等均对NB的还原效率有重要影响,特别是当初始pH值控制在偏酸时更有利于反应的进行。在硝基苯浓度约为0.0025mmol/g的2.00g模拟污染土壤中,Fe0加入量50mg、初始pH=4、反应时间5h的条件下,零价铁对土壤中NB的还原效率可达到96.58%。此外,本文还对Fe0还原NB的反应机理进行了初步探讨。     

水性道路沥青养护剂性能试验研究

首先通过沥青薄膜烘箱模拟沥青的老化,测定沥青老化前后性能变化;然后以乙烯釜液为溶剂,选择不同种类还原剂和水性防水剂筛选老化沥青还原剂的主要成分;最后通过正交实验,筛选出复合沥青养护剂的最优配方:乙烯釜液、抗坏血酸、硅醇钠、丁苯乳液的质量分数分别为4%,0.9%,0.5%,1.5%。实验结果发现老化沥青可达到原标准近似状态。     

河水-地下水交互带内砷及金属的自然衰减过程

在简单介绍污染物自然衰减作用定义的基础上,重点分析了河水-地下水交互带内As和以矿山废水为来源的金属污染物的自然衰减行为:主要包括吸附作用,氧化还原作用,生物转化作用等。其中详细介绍了金属Fe、Al的氢氧化物/氧化物对As化合物和其他金属如Cd、Cu和Zn等的吸附作用;Ca2+、Fe2+、磷酸盐、重碳酸盐等阴阳离子和天然有机质对吸附作用的影响;金属微生物氧化还原作用以及微生物作用下As(V)与As(III)的相互转化过程。研究发现,阳离子可以增强金属的吸附作用,阴离子主要是参与竞争吸附;天然有机质对金属吸附过程的抑制作用阻碍金属的固定;交互带内氧化还原条件的变化可以引起一系列的氧化还原反应;微生物催化还原不利于As的自然衰减。最后指出目前河水-地下水交互带内金属污染物衰减过程研究存在的问题以及今后的发展方向。     

淹水条件下土壤还原作用对镉活性消长行为的影响

采用红壤(pH=4.46)和潮黄土(pH=7.10)在氮气(N2)覆盖下进行淹水恒温((25.0±0.5)℃)培养.红壤在淹水60d后pH上升到5.92,潮黄土在淹水3d后pH降至6.62,然后再上升到6.89.2种土壤的pe+pH从14.16下降到5.38.pH和pe+pH的升降导致了土壤固相交换态(Exc-)、碳酸盐结合态(Carb-)、氧化物结合态(Oxide-)、有机质结合态(Org-)Fe再分配比例的增长,并使Exe-Cd向Carb-Cd、Oxide-Cd、Org-Cd转化.土壤Exc-Cd与Exc-Fe之间,Exc-Cd与(Carb-Cd+Oxide-Cd+Org-Cd)、(Caxb-Fe+Oxide-Fe+Org-Fe)之间均显著负相关,由此表明,Fe组分的再分配决定着Cd组分的再分配.Fe、Cd的形态分配还影响着液相中Fe、Cd的浓度.在红壤淹水的1～7d中,固相中Cd以Exc-Cd为主,液相中Cd的浓度随pe+pH的下降而增加;在红壤淹水的中后期及潮黄土的整个淹水期,固相中Cd以Carb-Cd和Oxide-Cd为主,液相中cd的浓度随pe+pH的下降而下降.淹水土壤中DOM对水溶性cd浓度的影响不显著.     

Anoxic biodegradation of dimethyl phthalate （DMP） by activated sludge cultures under nitrate-reducing conditions

Worldwide extensive use of plasticized plastics has resulted in phthalates pollution in different environment. Nitrates from industry and agriculture are also widely disseminated in the soils, natural waters and wastewaters. Dimethyl phthalate (DMP) biodegradation by activated sludge cultures under nitrate-reducing conditions was investigated. Under one optimized condition, DMP was biodegraded from 102.20 mg/L to undetectable level in 56 h under anoxic conditions and its reaction fitted well with the first-order kinetics. Using the high-performance liquid chromatography (HPLC) and liquid chromatography mass spectrometry (LC-MS) analysis, mono-methyl phthalate (MMP) and phthalic acid (PA) were detected as the major intermediates of DMP biodegradation. When combined with the determination of chemical oxygen demand (CODCr) removal capacity and pH, DMP was found to be mineralized completely under anoxic conditions. The biodegradation pathway was proposed as DMP → MMP → PA → … → CO2 H2O.The molar ratio of DMP to nitrate consumed was found to be 9.0:1, which agrees well with the theoretical stoichiometric values of DMP biodegradation by nitrate-reducing bacteria. The results of the non-linear simulation showed that the optimum pH and temperature for the degradation were 7.56 and 31.4℃, respectively.