混凝土灌注桩中混含硫酸盐的时变分布规律

硫酸盐环境下,为模拟混凝土灌注桩施工时混入的硫酸盐在桩中的时变分布行为,基于Fick第二定律并结合初始条件与边界条件,应用分离变量法,建立硫酸盐在桩中的时变分布模型。通过算例将本文解与传统解进行比较,并进一步探讨了硫酸盐扩散分布的影响因素和影响规律。结果表明,传统解用于分析混凝土灌注桩桩中硫酸盐扩散有局限性,而本文解相对于传统解具有一定的优势。混凝土灌注桩半径越小,应用传统解分析灌注桩中硫酸盐时变分布误差较大,同时,误差随时间增大。硫酸盐在混凝土灌注桩中的时变分布呈沙漏形,沿半径方向x=0处和桩表面处扩散行为明显,在x=0处附近区域,初始第一年扩散速率较快,在后续的50 a内扩散速率显著减小,但每10 a的平均速率基本相同。扩散系数和初始浓度梯度对硫酸盐在混凝土灌注桩中的时变分布影响较大。     

集中排水甘蔗地酸性硫酸盐土壤酸化的减缓

Recent research results suggest that acidification of acid sulfate soils may be inhibited in well-drained estuarine floodplains in eastern Australia by the absence of natural creek levees,The lack of natural levees has allowed the inuudation of the land by regular tidal flooding prior to the construction of flood mitigation work.Such physiographical conditions prevent the development of pre-draingae pyrite-derived soil acidifica-tion that possibly occurred at many levee-protected sites in eastern Australian estuarine floodplains during extremely dry spells.Pre-drainage acidification is considered as an important condition for accumulation of soluble Fe and consequently,the creation of favourable environments for catalysed pyrite oxidation.Under current intensively drained onditions,the acid materials produced by ongoing pyrite oxidation can be rapidly removed from soil pore water by lateral leaching and acid buffering,resulting in low concentrations of soluble Fe in the pyritic layer,which could reduce the rate of pyrite oxidation.     

电解质阴离子和pH对可变电荷土壤硫酸盐吸附的影响

The effects of three electrolyte anions, ionic strength and pH on the adsorption of sulfate by two variable charge soils, with different surface charge properties were studied. Under the conditions of the same pH and ionic strength the effect of electrolyte anions on the adsorption of sulfate was in the order of Cl^- > NO₃^- > ClO₄^-, indicating the difference of the nature among these three anions. For Ferralsol in the same concentration of chloride and perchloride solutions, the two sulfate adsorption-pH curves could intersect at certain pH value. When pH was higher than the intersecting point, more sulfate was adsorbed in the perchloride solution, while when it was lower than the intersecting point, more sulfate was adsorbed in the chloride solution. In different concentrations of electrolyte solution, the curves of the amount of oxy-acid anion adsorbed, which changed with pH, could intersect at a certain pH, which is termed point of zero salt effect (PZSE) on adsorption. The nature of electrolyte anions influenced obviously the appearance of PZSE for sulfate adsorption. For ferralsol the curves of adsorption converged to about pH 7 in NaCl solution seemed to intersect in NaNO₃ solution and to have a typical PZSE for sulfate adsorption in NaClO₄ solution. For Acrisol the three curves of adsorption were nearly parallel in NaCl and NaNO₃ solutions and converged to pH 6.5 in NaClO₄ solution.     

几种利用方式下酸性硫酸盐土的环境风险及其连锁效应

研究并比较了不同利用方式下酸性硫酸盐土酸形态和铝形态的结构特征,分析了硫形态与酸形态、酸形态与铝形态之间的相关性。研究发现,酸性硫酸盐土的不同利用类型中,土壤酸度由大到小依次为:鱼塘塘基、荒稻田>稻田>荒旱地>改良稻田>蔗田>红树林迹地;活性铝含量由高到低依次为:荒旱地>鱼塘塘基、荒稻田>稻田>改良稻田>蔗田>红树林迹地。土壤酸度和铝形态含量的层间差异较为显著,多数随深度增加呈逐渐上升的趋势。酸性硫酸盐土中的硫形态—酸—铝形态之间有明显的连锁关系。     

NaCl和Na2SO4胁迫对蒲公英种子发芽及成苗的影响

以蒲公英种子为试材，在NaCl和Na2SO4盐溶液中发芽，幼苗在持续盐胁迫条件下成苗生长。结果表明，当浓度为3500mg／kg时，NaCl和Na2SO4分别严重抑制了蒲公英种子的发芽，达到极显著水平。NaCl对种子发芽率的抑制强于Na2SO4。蒲公英成苗胁迫试验中，NaCl，Na2SO4浓度分别为5000mg／kg时，严重影响蒲公英成苗率、幼苗根、茎的生长和鲜干重比值，对叶绿素含量影响不大。种子发芽期问适当浓度的NaCl和Na2SO4盐溶液胁迫有助于诱导蒲公英幼苗耐盐性的产生。     

Antifungal effects of iron sulfate on grapevine fungal pathogens

The present study aimed to determine the most efficient experimental conditions of iron sulfate use leading to optimal inhibition in the development of fungal pathogens. Assays have been focused on fungal species inducing severe grapevine diseases. FeSO₄ directly inhibited the in vitro mycelial growth of Botrytis cinerea, Eutypa lata, Phaeomoniella chlamydospora, Phaeoacremonium aleophilum, Diplodia seriata, and Neofusicoccum parvum with variable efficiency in the range of 0.5–10 mM. The development was always completely inhibited at 20 mM. This inhibitory effect was greatly increased at acidic pH values. The anionic moiety of the molecule was of importance since bromide, chloride and sulfate were highly active, whereas acetate and oxalate showed a small effect. Electron microscope observations on E. lata and B. cinerea showed that a treatment with FeSO₄ induced dramatic changes in the hyphal organization leading to cell death. No toxicity was observed on grapevine leaves following repeated FeSO₄ sprays in the antifungal concentration range. Therefore, FeSO₄ may be proposed to effectively replace the long-term pollutant use of CuSO₄ as an antifungal agent, with the additional advantage of iron being an important plant micronutrient.     

乳酸菌富铁的研究

为了使铁离子转化为易被动物体吸收的微量元素,以防治仔猪因缺铁而造成的贫血等病症,本研究用乳酸菌富集铁元素。首先测得乳酸菌在硫酸亚铁和有机铁2种来源的铁元素中所能正常生长的最高铁离子浓度,然后加入适宜浓度的铁离子培养乳酸菌至最高活菌数。菌液离心后冲洗3次并烘干,用原子分光光度法测定乳酸菌干细胞内铁离子的含量,比较乳酸菌对2种形态铁元素的富集能力。最后做饲养试验。结果表明:乳酸菌对有机铁的耐受质量浓度(0.5 g/L)比硫酸亚铁(0.1 g/L)高;乳酸菌对有机铁的富集能力(1.590 mg/g)比硫酸亚铁(0.024mg/g)强。含有机铁的乳酸菌制剂对降低断奶仔猪死亡率有显著效果。     

Arylsulfatase activity in soil and soil extracts using natural and artificial substrates

The arylsulfatase activity of soil and humic arylsulfatase complexes extracted from soil were measured using the substrates p-nitrophenyl sulfate and low molecular weight (500–10000) soil ester sulfate compounds. Soil samples from the Aphorizon of a Podzol from S-amended wheat plots and a Regosol from dykeland hayfield plots were investigated. Soil arylsulfatase activity (assayed with p-nitrophenyl sulfate) in the fall was significantly higher than spring samples; however, no seasonal differences were observed when humic-arylsulfatase complexes were assayed with p-nitrophenyl sulfate. The discrepancy between arylsulfatase activity in soil and soil extracts was probably due to inhibitors which were found in soil materials. These results appear to support the theory that abiotic arylsulfatase is a relatively stable and persistent component of soil. There was a marked difference in the response by humic-arylsulfatase complexes to the artificial substrate p-nitrophenyl sulfate and natural low molecular weight soil substrates. Humic-arylsulfatase complexes hydrolysed 35–80% of added low molecular weight substrates depending on the treatment. The molecular size, concentration, and chemical composition of the low molecular weight ester sulfate compounds affected hydrolysis of the low molecular weight substrates. The response by humic-arylsulfatase complexes to the chromogenic ester sulfate, p-nitrophenyl sulfate did not reflect the ability of these complexes to hydrolyse natural soil substrates. In an experiments we examined arylsulfatase activity and soil S status in relation to the total S in plant tissue and grain from wheat plants grown in the Podzol. Tissue S was more strongly associated with soil S than the wheat grain. Hydriodic acid-S, Ca(H₂PO₄)₂-extractable sulfate, and hydrolysable ester sulfates in the high molecular weight (>10000) and low molecular weight (500–10000) fractions of soil organic matter extracts were strongly positively correlated with tissue S. Arylsulfatase activity in soil and humic-arylsulfatase extracts assayed with p-nitrophenyl sulfate were also strongly correlated with tissue S, while humic-arylsulfatase activity assayed with the low molecular weight substrate was negatively correlated with tissue S.     

Molecular Monitoring of SRB Community Structure and Dynamics in Batch Experiments to Examine the Applicability of in situ Precipitation of Heavy Metals for Groundwater Remediation (15 pp)

Background, Aims and Scope   Sulfate-reducing bacteria (SRB) are known for their capacity to reduce and precipitate heavy metals (HM) as metal sulfides, offering the opportunity to create an in situ reactive zone for the treatment of heavy metal-contaminated groundwater, a process called in situ metal precipitation (ISMP). The applicability of the ISMP technology first has to be investigated at a laboratory scale before going into an on site application. The evaluation and optimization of the ISMP process is facilitated when physical/chemical analysis techniques are combined with molecular tools that specifically monitor the abundance, diversity and dynamics of the indigenous sulfate reducing microbial community. In this study, batch experiments were conducted in order to investigate the feasibility of ISMP as a groundwater remediation strategy for an industrial site contaminated with elevated levels of Zn, Cd, Co and Ni. Methods   The potential of different types of carbon source/ electron donor (lactate, acetate, methanol, ethanol, Hydrogen Release Compound?, molasses) to stimulate the sulfate reduction and metal precipitation activity of the naturally present (or indigenous) SRB community was explored. In addition, the effect of amending vitamin B12 and yeast extract was evaluated. The ISMP process was monitored by combining analytical analyzes of process parameters (SO42-concentration, heavy metal concentrations, pH, Eh) with molecular tools such as SRB subgroup and genus specific PCR, denaturing gradient gel electrophoresis (DGGE), and phylogenetic analysis of clone sequences, based on either the 16S rRNA or the dsr (dissimilatory sulfite reductase) gene. Results and Discussion   The efficiency of different carbon-sources to stimulate the ISMP process followed the order HRC 〉 molasses 〉 methanol 〉 lactate 〉 ethanol 〉 acetate. Within 10 weeks, the highest sulfate and metal removal efficiencies ranged from 85% to 99%. Addition of yeast extract boosted the ISMP process, whereas vitamin B12 negligibly affected SRB activity. Analysis of the sulfate reducing population by SRB subgroup and genus specific PCR demonstrated that members of the genus Desulfosporosinus dominated in all batch tests, while 16S rDNA DGGE profiles additionally revealed the presence in the microbial communities of non-sulfate reducing bacteria within the family Clostridium and the -proteobacteria. The dsrB-based DGGE profiles allowed us to assess the diversity and dynamics of the sulfate reducing community and added to a better understanding of the effects of different batch conditions on the ISMP process. Remarkably, all dsrB sequences affiliated with the dsrB gene sequence cluster found in Desulfotomaculum, which received their xenologous dsrB gene from the -proteobacteria. Conclusions   The batch experiments, which aimed at stimulating the activities of the indigenous SRB communities, demonstrated that these communities were present and that their activities could be used to obtain efficient in situ precipitation of the contaminating heavy metals. This opens the possibility to test this concept in the future as an on site demonstration as part of the groundwater strategy for the heavy metal contaminated site. Although batch setups are suitable for preliminary feasibility studies for ISMP, they do not reflect the in situ situation where sulfate and heavy metal and metalloid polluted groundwater are supplied continuously. A sulfate reducing strain JG32A was isolated from whose 16S rRNA gene affiliated with the genus Desulfosporosinus, while its dsrB gene sequence clustered with Desulfotomaculum dsrB gene sequences, which received their xenologous dsr genes from -proteobacteria. Therefore we hypothesize that the batch experiments enrich members of the Desulfosporosinus genus that possess a non-orthologous dsrB gene. Recommendation and Perspective   The next step towards an on site pilot test for ISMP will be the setup of a series of column experiments, with process conditions that are selected based on the above mentioned results. This will allow to define optimal ISMP process conditions and to test its long-term efficacy and sustainability before going into an on site bioremediation application. By applying the described molecular tools together with physical-chemical analyzes, it can be investigated whether the same SRB community is enriched and which type of C-source is most effective in promoting and sustaining its growth and sulfate-reduction activity.     

Redox potential of bulk soil and soil solution concentration of nitrate,manganese, iron,and sulfate in two Gleysols

While the reduction of nitrate‐N, Mn(III,IV), Fe(III), and sulfate‐S in soil has been studied intensively in the laboratory, field research has received only limited attention. This study investigated the relationship between redox potential (E_H) measured in bulk soil and concentrations of nitrate, Mn²⁺, Fe²⁺, and sulfate in the soil solution of two Gleysols differing in drainage status from the Marsh area of Schleswig‐Holstein, Northern Germany. The soils are silty‐sandy and developed from calcareous marine sediments. Redox potentials were monitored weekly with permanently installed Pt electrodes, and soil solution was obtained biweekly by ceramic suction cups from 10, 30, 60, and 150 cm depth over one year. Median E_H at 10, 30, 60, and 150 cm depths was 470, 410, 410, and 20 mV in the drained soil and 500, 480, 30, and –170 mV in the undrained soil, respectively. A decrease in E_H below critical values was accompanied in the soil solutions (pH 7.4 to 7.8) by disappearance of nitrate below 0 to 200 mV, appearance of Mn²⁺ below 350 mV, and Fe²⁺ below 0 to 50 mV. Both metals disappeared from soil solution after aeration. In the sulfide‐bearing environment of the 150 cm depth of the undrained soil, however, the sulfate concentrations were highest at such E_H values at which sulfate should be unstable. This discrepancy was reflected in the fact that at this depth bulk soil E_H was about 400 mV lower than soil solution E_H (250 mV). When investigating the dynamics of nitrate, Mn, and Fe in soils, bulk soil E_H provides semi‐quantitative information in terms of critical E_H ranges. However, in sulfidic soil environments the interpretation of E_H measured in bulk soil is uncertain.