氢基质生物膜反应器去除对氯硝基苯的影响因素分析

基于MBfR(氢基质生物膜反应器)研究进水中ρ(p-CNB)(p-CNB为对氯硝基苯)和氢气压力对氢基质自养微生物还原降解p-CNB的影响,同时分析在ρ(p-CNB)和氢气压力影响下生物膜内电子受体生物还原的当量电子通量和还原动力学. 结果表明:提高进水中的ρ(p-CNB),p-CNB、p-CAN(对氯苯胺)的去除通量分别由0.014、0.011 g/(m2·d)升至0.099、0.060 g/(m2·d),但p-CNB的去除率由95.9%降至68.4%;提高氢气压力,p-CNB、p-CAN的去除通量分别由0.027、0.019 g/(m2·d)升至0.028、0.022 g/(m2·d),p-CNB去除率由93.1%升至95.1%,升幅均不大,说明进水ρ(p-CNB)比氢气压力更能直接影响p-CNB和p-CAN的去除通量及p-CNB去除率. 当量电子通量分配和还原动力学结果表明,p-CNB和p-CAN的还原对氢气压力升高的敏感性不强烈,进一步揭示降低进水中ρ(p-CNB)比提高氢气压力更能明显地促进微生物对p-CNB和p-CAN的去除效果. 氢气压力变化对硫酸盐还原和反硝化的影响程度高于p-CNB或p-CAN的还原,当氢气可利用率受限时,p-CNB或p-CAN的还原会由于电子供体的竞争而受到抑制.      

基于TASCC的典型农田溪流氨氮滞留及吸收动力学模拟

为揭示农田溪流氨氮滞留的动态变化性,选择NaCl为保守示踪剂、NH4Cl为添加营养盐开展野外瞬时投加示踪实验.在此基础上,采用TASCC方法和养分螺旋指标定量刻画 滞留动态,并以Michaelis-Menten模型(M-M方程)模拟 吸收动力学特性.结果表明:背景浓度的 吸收长度Sw-amb变化范围为93.94~295.54m,平均值为177.41m;质量传输系数Vf-amb变化范围为0.16~0.38mm/s,平均值为0.26mm/s;吸收速率Uamb变化范围为0.16~0.38mg/(m2×s),平均值为0.26mg/(m2×s).由M-M方程模拟得到的 最大吸收速率Umax为0.59~1.38mg/(m2×s),半饱和常数Km为1.10~5.03mg/L. 在从背景浓度到饱和浓度区间范围内展现出的Sw-add-dyn、Utot-dyn和Vf-tot-dyn动态变化性,验证了TASCC解析 滞留动态和吸收动力学特征的可行性和有效性.     

Preparation,characterization of sludge adsorbent and investigations on its removal of hydrogen sulfide under room temperature

To recycle the sludge resource from sewage treatment plants and solve the problem of odor pollution, the sludge was converted into an adsorbent by carbonized pyrolysis and the process was optimized by orthogonal experiments. The capability for odor removal as well as the structure of the adsorbent was studied with H₂S as a target pollutant. The results indicate that the main factor affecting the deodorization performance of the adsorbent is the activating time. The sludge adsorbent sample SAC1 prepared under optimum conditions exhibits the best deodorization performance with a H₂S breakthrough time of 58 min and an iodine value nearly that of the coal activated carbon. The breakthrough time of H₂S is much longer than that on the coal activated carbon. On the other hand, characterization results from X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS) and scanning electron microscope (SEM) techniques show that SAC1 is composed of mainly graphite carbon with lower oxygen content on the surface. The bulk of SAC1 exhibits a honeycomb structure with well developed porosity and a high specific surface area of 120.47 m²·g^-1, with the average pore diameter being about 5 nm. Such a structure is in favor of H₂S adsorption. Moreover, SAC1 is detected to contain various metal elements such as Zn, Fe, Mg, etc., leading to a superior deodorization property to that of coal activated carbon.     

Source and Distribution of Heavy Metals in Food†

Diet is the major route of exposure to contaminants, therefore food monitoring programs are essential to estimate the degree of human risk. We present a study undertaken in Austria dealing with the total uptake of mercury, cadmium, arsenic and lead. The dates were calculated from diet as well as from commercial food. Higher contaminated foodstuffs are registered and a comparison was made between body burden of babies and adults on the basis of bodyweight. It was pointed out, that cooked or washed food ready to eat has a lower burden of lead and cadmium than non prepared food due to household processing, which may decontaminate food to some extent’ Arsenic content was not reduced, because it is bound chemically and not primarily deposited on the surface of food such as in the case of lead. It was mentioned that the type of compound plays an important role in the assessment of action of those elements on humans.

Their biological activity is not necessarily related to their concentration in food. As in the case of selenium and chromium one has to take into consideration that there is a narrow range between benefit and harm, toxicity, and minor supply.

Therefore we conclude, that due to interactions of elements, their different biological activity and due to the difference of compounds present in food, we have to relativate the terms toxicity and essentiality. Then we can get a more profound insight into the problems of trace elements in food.     

Chromium accumulation,transport and toxicity in plants∗

The predominant pathway for human exposure to chromium in non‐occupationally exposed individuals is via food with a daily intake of around 30–100 μgd^–1, with vegetables providing a major contribution. Unlike reports of chromium essentiality to man and animals, plants appear not to require chromium in spite of some early reports of a stimulatory growth effect.

Most reports on chromium in plants have been concerned with their growth on soils amended with sewage sludge, pF‐ash, tannery waste, or on ultra basic soils, which contain extreme concentrations of the element. Experimental studies with plants grown in hydroponic solution have often been undertaken at unrealistically high concentrations to examine the uptake of chromium in various forms, either as CrIII or CrVI at different pHs. In most cases, reports on chromium in plants deal with element concentrations and plant/soil relationships rather than detailed biochemical and physiological processes.

In general, chromium is largely retained in the roots of plants, although the oxidation state of chromium, pH, presence of humates and fulvates and plant species, affect plant uptake and transport. Leaves usually contain higher concentrations than grains. The uptake of CrIII is largely a passive process, whereas CrVI uptake is a metabolically mediated process via the sulphate pathway and is thus readily transported around the plant. The presence of a compound similar to trioxalate CrIII has been recorded while little chromium has been reported to be associated with cell organelles or soluble proteins.     

Cadmium uptake by a phytoplankton species in the presence of different inhibitors&

The uptake of cadmium by the Haptophyceae Hymenomonas elongata was studied as regards the energetic processes and Ca‐transport. For this purpose, experiments were carried out in the presence of an uncoupler of the phosphorylation : CCCP and of an inhibitor of calcium channels and also of Ca²⁺‐ATPase : verapamil. To reduce the number of assays, a factorial experimental design was used, in which all variables:— concentration of Cd in the medium—incubation time and—the presence of the inhibitor, are at two levels. In the absence of inhibitor, Cd uptake was found to vary as a function of metal concentration in the medium and of incubation time. CCCP significantly increased Cd uptake by H. elongata at sufficient incubation time. Therefore Cd uptake seemed linked to an energy‐dependent process, involving an ATPase. Verapamil immediately increased Cd uptake, implying an interaction between Cd and Ca.     

Effects of cucl2 on UV‐mutagenesis and on DNA damage in a restriction fragment of E. Coli gpt∗

CuCl₂ does not cause Trp⁺ reversion in E. coli WP2. However, when the bacteria are exposed to CuCl₂ and UV‐irradiated, a greater than 3‐fold enhancement of mutagenesis (compared to UV alone) is seen at 30 μMCuCl₂, and significant enhancement is seen even at 3 μM. The mechanism for this comutagenic effect was studied using a restriction fragment of the E. coli gpt gene. Whereas UV or CuCl₂ alone caused few strand breaks, UV + CuCl₂ induced breaks at every site. This reaction was blocked by KI, a free radical scavenger. While UV alone induced alkali‐labile sites, UV+ CuCl₂ induced many more such sites and altered the sequence specificity. We suggest that at least some of the comutagenic effect might be due to hydroxyl radical formed via a Fenton reaction.     

氮输入对沼泽湿地植物生长和氮吸收的影响

氮是湿地植物生长必不可少的营养元素之一,但当外源氮输入超出植物生长需要时,氮素将抑制植物生长。不同植物对氮输入的响应不同,同一植物不同器官对氮输入的响应也不一致。为了探讨氮输入对湿地植物生长和氮吸收的影响机制,本文选取滇西北典型湖泊湿地纳帕海湖滨挺水植物茭草（Zizania caduciflora）和水葱（Scirpus validus）为对象,通过控制实验,研究了3个不同氮输入水平[0 g·m-2·a-1（对照,CK）、20 g·m-2·a-1（N20）、40 g·m-2·a-1（N40）]对茭草和水葱生物量积累、根冠比、氮吸收的影响。结果表明：培养期内,茭草地上生物量始终表现为N40〉N20〉CK,即氮输入促进茭草地上生物量积累;而水葱地上生物量随培养时间不同而发生变化,培养早期N20处理促进水葱地上生物量积累,N40处理抑制水葱地上生物量积累。茭草地下生物量表现为N40〉CK〉N20,即氮输入不足抑制茭草地下生物量积累,足够氮输入促进茭草地下生物量积累;水葱地下生物量表现为CK〉N20〉N40,即氮输入抑制水葱地下生物量积累。植物地上部分和地下部分生长对氮输入的响应也不一致,导致植物根冠比发生变化,茭草根冠比表现为N20     

Organic and inorganic phosphorus uptake by bacteria in a plug-flow microcosm

Phosphorus (P) is a vital nutrient for sustaining natural water productivity. Both particulate and dissolved forms of organic and inorganic P are potentially important sources of bioavailable P for primary and secondary producers. A microcosm system to imitate the bacterial community in Plym river sediment and pore water is described and bacterial uptake rates for inorganic and organic phosphorus are presented in this paper. The aim of this study was to investigate the uptake of two organic phosphorus compounds (phytic acid and D-glucose-6-phosphate) by freshwater bacteria. The bioreactors comprise glass columns packed with two types of small glass beads on which bacterial biofilm can develop. The glass beads with different porosity were introduced to simulate River SPM. The selected P compounds spiked into the inflow of the microcosm, and measured the step change of P concentration in the outflow to investigate the behavior of bacterial uptake of nutrients. The results showed that organic phosphorus was converted into inorganic phosphorus but the conversion rate depended on the type of phosphorus species. One experiment suggested that phytic acid (refractory) could displace phosphate from the biofilm surface; the other experiment showed that D-glucose-6-phosphate (labile) could be hydrolysed and utilized easily by the bacteria. The results also suggested that bacteria might break down the C-P bonds to utilize the carbon. Further experiments should investigate the effect of varying the C:N:P ratio in the microcosm system to determine which nutrient limits bacteria uptake.     

Study on removing selenate from groundwater by autohydrogenotrophic microorganisms

Performance of autohydrogenotrophic bacteria for bio-reduction of selenate (Se(VI)) under anaerobic conditions was investigated with batch experiments. Results showed Se(VI) was bio-reduced to selenite (Se(IV)) as an intermediate product, and then to elemental selenium (Se⁰). Reduction kinetics could be described by the pseudo-first-order model. In particular, the influences of pH value and temperature on Se(VI) reduction by autohydrogentrophic organisms were examined. The high degradation rate was achieved at pH 7.0 to 8.0; and the best reduction temperature was between 25°C and 35°C. This study is of help for treating groundwater with selenium contamination by autohydrogenotrophic bacteria as well as its reactor development.