自制ZSM-5分子筛对甲苯气体的吸附-脱附性能

考察了自制ZSM-5分子筛对甲苯气体的吸附-脱附性能,并与市售MCM-22分子筛进行了对比实验。实验结果表明:在吸附温度为25℃、进口甲苯质量浓度为840mg/m3、吸附气体流速为0.016m/s、床层高度为15cm的条件下,出口甲苯质量浓度达到0.8mg/m3时的穿透时间为82min,吸附效率为4.26mg/g;在脱附温度为80℃、脱附气体流速为0.016m/s的条件下,脱附35min时出口甲苯质量浓度达到最大,为1220mg/m3。自制ZSM-5分子筛的吸附-脱附性能优于市售MCM-22分子筛。     

苯系物降解单菌间的协同耦合作用

针对BTEX降解混菌间协同耦合作用不明的问题,以稳定的BTEX降解混菌为研究对象,通过分离纯化,从混菌中分离得到的8株BTEX降解单菌,将对BTEX有降解效果和没有降解效果的单菌分别组合,采用摇瓶实验研究不同体系对BTEX的降解效果,试图找到单菌在BTEX降解过程中的作用,并探寻菌间的协同耦合作用。实验结果表明,B2、B4、B6单菌主要的作用是降解BTEX,并且B2菌可以解除B4菌和B6菌混合后对X降解的抑制,并提高了B、T和E的降解速率;B1、B3、B5、B7和B8单菌无BTEX降解功能,B1、B3和B5菌可能利用B、T和E降解过程中产生的代谢产物(各单菌没有降解能力,但在混菌中依然存在,推测单菌可以利用降解过程中产生的代谢产物),并从48 h开始降解B、T和E;B7、B8两株菌互相协同,共同完成对BTEX的降解。由优势菌群和非优势菌群组成的混合系统,促使有些没有降解功能的菌株混合后具有降解功能,还导致有些菌株混合后降解率和降解速率降低,对降解BTEX既有促进作用又有拮抗作用。混菌48 h对BTEX的总降解率为91.6%,说明一个稳定存在的天然混合群落,其内部菌种经过长期的优胜劣汰,保持了很高的降解率和降解速率。     

Alleviating versus stimulating effects of bicarbonate on the growth of Vallisneria natans under ammonia stress

Bicarbonate plays a crucial role in limiting the growth of submersed aquatic macrophytes in eutrophic lakes, and high ammonia is often toxic to macrophytes. In order to evaluate the combined effect of HCO₃ ^? and total ammonia (i.e., the total of NH₃ and NH₄ ⁺) on submersed macrophytes Vallisneria natans, the growth and physiological response of V. natans in the presence of HCO₃ ^? and ammonia were studied. The results showed that with the increase of ammonia, morphological parameters of V. natans declined. In contrast, increased HCO₃ ^? concentration stimulated the growth of V. natans, especially when the NH₄ ⁺-N/NO₃ ^?-N ratio was 1:7. High ammonia concentration induced excess free amino acids (FAA) accumulation and soluble carbohydrates (SC) depletion in plant tissues. However, the elevated HCO₃ ^? promoted the synthesis of SC and rendered the decrease of FAA/SC ratio. The results also suggested that HCO₃ ^? could partially alleviate the stress of ammonia, as evidenced by the decrease of FAA/SC ratio and the growth enhancement of V. natans when the ammonia concentration was 0.58 mg?L^?1. Given the fact that HCO₃ ^? is probably the dominant available carbon source in most eutrophic lakes, the ability of V. natans to use HCO₃ ^? for SC synthesis may explain the alleviating effect of HCO₃ ^? on V. natans under ammonia stress.     

A comparison of phosphorus speciation and potential bioavailability in feed and feces of different dairy herds using 31p nuclear magnetic resonance spectroscopy

An experiment was conducted to examine how potential phosphorus (P) bioavailability (inferred from speciation) differs in feed and feces collected in spring from four dairy herds representing different management systems: (i) total confinement with cows fed total mixed ration (TMR), (ii) total confinement with TMR plus P mineral supplement, (iii) a hybrid of confinement with TMR and pastoral grazing, and (iv) predominantly grazing with supplemental grains. A treatment was included that air dried feces to simulate conditions after dung deposition. Wet chemical techniques and solution (31)P nuclear magnetic resonance spectroscopy ((31)P-NMR) were used to identify P concentrations and compounds present in water (a surrogate for P in overland flow), dilute acid (0.012 M HCl, an estimate of P utilization by cattle), or NaOH-EDTA (a solution that maximizes the organic P extraction) extracts of feed and feces. In general, P concentration in feces paralleled P in feed. Air drying feces decreased water-extractable P by 13 to 61% largely due to a decrease in orthophosphate, whereas NaOH-EDTA-extractable P increased by 18 to 48%. Analysis of dilute HCl was unsuccessful due to orthophosphate precipitation when pH was adjusted to 12 for (31)P-NMR. In water extracts, more P was in bioavailable diester-P forms, undetectable by colorimetry, than in NaOH-EDTA extracts. In feed, orthophosphate dominated (46-70%), but myo-IHP varied with feed (<10% in forage samples but 43% in a TMR sample). The proportion of myo-IHP decreased in feces compared with feed via mineralization but decreased less in systems with a greater proportion of available P input (e.g., orthophosphate and phospholipids). Feed and drying effect the concentrations and forms of P in feces and their potential impact on soil and water quality. Although bioavailable P in feces from pasture-based and confined systems can be similar in spring, dung-P is distributed on a lower kg P ha(-1) rate in grazing systems. The best method to mitigate P loss from feces is to decrease P in feed.     

Zeolite/ZnAl-layer double hydroxides with different Zn/Al ratios and intercalated anions as the substrate of constructed wetlands: synthesis,characterization and purification effect of Hexavalent chromium

Environmental Science and Pollution Research - The study aimed to synthesize novel zeolite substrates modified with four types of ZnAl-LDHs including Cl-LDHs(1:1), Cl-LDHs(3:1), CO3-LDHs(1:1), and...     

用动态的观点进行环境综合质量评价

强调用动态的观点进行环境质量评价,着重对如何从方法上体现这种观点进行了探索,提出了“变权”思想,设计了“权”调整公式,并依此对新疆库尔勒市环境综合质量进行了评价,其结果表明该方法在实际应用中是可行的,也是较合理的。     

高价离子还原菌还原机理及研究进展

高价离子还原菌普遍存在于自然环境中,它们在环境的原位修复中起着非常重要的作用。本文主要介绍了三种典型的高价离子还原菌：异化Fe（III）还原菌（IRB）、硝酸盐还原菌及硫酸盐还原菌（SRB）,分别以Fe3＋、N03-和SO4^2-为电子受体,以有机物作为电子供体,在将高价离子还原的同时,达到对污染环境的修复作用。文章综述了此类细菌的特性、作用机理、影响因素以及在国内外实际中的应用,分析了异化Fe（III）还原菌、硝酸盐还原菌及硫酸盐还原菌的异同点,并对该类细菌在环境污染治理中的发展趋势进行了评述。     

Characteristics of volatile compounds removal in biogas slurry of pig manure by ozone oxidation and organic solvents extraction

Biogas slurry is not suitable for liquid fertilizer due to its high amounts of volatile materials being of complicated composition and peculiar smell. In order to remove volatiles from biogas slurry efficiently, the dynamic headspace and gas chromatography-mass spectrometry were used to clear the composition of volatiles. Nitrogen stripping and superfluous ozone were also used to remove volatiles from biogas slurry. The results showed that there were 21 kinds of volatile compounds in the biogas slurry, including sulfur compounds, organic amines, benzene, halogen generation of hydrocarbons and alkanes, some of which had strong peculiar smell. The volatile compounds in biogas slurry can be removed with the rate of 53.0% by nitrogen stripping and with rate of 81.7% by the oxidization and stripping of the superfluous ozone. On this basis, the removal rate of the volatile compounds reached 99.2% by chloroform and n-hexane extraction, and almost all of odor was eliminated. The contents of some dissolved organic compounds decreased obviously and however main plant nutrients had no significant change in the biogas slurry after being treated.     

高效降解黑臭废水细菌的筛选及鉴定

以筛选出能够高效降解黑臭废水的更多细菌为目的,从不同重污染水体和底泥中筛选获得了多种细菌,并对其降解能力进行检测。净化实验结果表明,筛选出的50多株细菌中有12株对废水COD有明显的降解效果,降解率在45%以上;有4株菌对废水氨氮有明显的降解效果,降解率在30%以上,其中4号菌株对COD和氨氮都有很高的降解能力。经16SrRNA基因鉴定,4号菌株为不动杆菌属,由单因子优化实验得出4号菌株生长的最适条件为:温度30℃,pH7.5,转速180r/min,培养时间为22h时,微生物达到稳定期。在此条件下,4号菌株对自然黑臭废水COD和氨氮的降解率可达到92%和72%。     

常用家用电器的防火方法

目前,家用电器种类繁多,使用面广,电视机、电冰箱、收录机、洗衣机、电熨斗、电饭锅、空调器,录像机等。这些家用电器确实丰富和改善了人们的生活条件,但又