还原铁粉去除地下水中硝酸盐氮的研究

地下水中硝酸盐氮的污染问题变得日益突出,为此以100～200目的铁粉为还原剂,采用静态试验方法研究了不同pH值、硝酸盐氮初始浓度、溶解氧、铁粉表面预处理及铁与硝酸盐氮的质量比等因素对硝酸盐氮去除率的影响。结果表明,溶液的初始pH值对硝酸盐氮的去除影响很大,pH>4时,铁粉几乎不与水中硝酸盐氮进行反应;铁粉经过表面处理后在同一时刻内对硝酸盐氮的去除率提高1倍多;铁与硝酸盐氮的最佳质量比为200∶1;溶解氧对硝酸盐氮的去除没有太大影响;反应产物主要是氨氮。     

固体亚硫酸铵肥料在水稻土施用的研究——一种新型氮肥的开发利用

本文讨论固体亚硫酸铵肥料在水稻土施用的肥效、转化和对土壤氧化还原状况的影响。试验结果表明,只要施用量恰当,亚铵与硫铵有同等肥效。亚铵可以利用工业废气中的 SO_2生产,良化生态环境,变废为宝,开发利用很有意义。亚铵在渍水土壤施用,引入的 SO_3~(2-),多数在水层被氧化成 SO_4~(2-),对土壤还原性质影响不大;土层的pe+pH多数在5以上,不足以造成 SO_3~(2-)被还原成 H_2S~0或 S~(2-)而构成对水稻毒害。土壤水溶性亚铁离子约占亚铁离子总量的5%(约28ppm),低于对水稻毒害的临界浓度。亚铰肥料在水稻土合理施用是安全的,肥效良好。     

Effects of dietary ascorbic acid/iron ratio on some production traits, lipid peroxide state and amount/activity of the glutathione redox system in African catfish Clarias gariepinus (Burchell) fingerlings

African catfish Clarias gariepinus (Burchell) fingerlings (3.16–3.92 g initial body weight) were investigated for 30 days in four different groups using different amounts of l ‐ascorbic acid (AA) and iron (supplied as FeC₆H₅O₇) in their feedings. Diet 1 (control): no addition of AA or iron; diet 2 (H‐AA/FE): high (600 mg kg^?1) AA and low (218 mg kg^?1) iron; diet 3 (H‐HE/AA): high (364 mg kg^?1) iron and low (200 mg kg^?1) AA; and an unfed group, which was investigated only for 15 days due to high mortality. The live weight gain, feed intake, specific growth rate (SGR; % body weight day^?1) and feed conversion rate (FCR) were measured or calculated. At the end of the experimental period, the whole body content of AA, iron, reduced glutathione (GSH), glutathione disulphide (GSSG) and malondialdehyde (MDA), as well as the glutathione peroxidase (GSHPx) activity, were measured. The production traits did not differ significantly as a result of the different AA and iron contents of the feed. AA content increased significantly in all the groups as compared with the initial value, except in the unfed group. The difference between the treated groups as compared with the control, with regard to the two AA/iron treated groups, was also significant. The iron content in the fish body increased significantly compared with the initial value, except in the unfed group. The difference compared with the control was significant only in the H‐FE/AA group. The difference between the groups that consumed low and high iron content diets was also significant. The GSH and GSSG content, as well as the GSH/GSSG ratio and GSHPx activity of the fish body, did not differ significantly as compared with the initial value or with the control. The lipid peroxide status, as measured by the MDA content, did not differ significantly either as an effect of the AA and iron supplementation, but decreased as an effect of ageing and starvation. It may be concluded that, under the present experimental conditions, the C. gariepinus fingerling tissue stores of AA and/or iron increased as a result of feed supplementation, but without altering the actual lipid peroxide status and the amount/activity of the glutathione redox system.     

Electrochromic Properties and Electrochemical Behavior of Marennine,a Bioactive Blue-Green Pigment Produced by the Marine Diatom Haslea ostrearia

Marennine has long been known as the unique peculiar pigment responsible for the natural greening of oysters. It is specifically produced by the marine diatom Haslea ostrearia and it is a natural blue molecule indeed promising for food industry because of the rarity of such non-toxic, blue-colored pigments. In the search for its still not defined molecular structure, investigation of the color changes with the redox state has been carried out combining different approaches. Reducing and oxidizing chemicals have been added to purified marennine solutions and a stable blue-green color has been confirmed for the oxidized state, while a yellow color corresponded to the reduced unstable state. Raman spectroscopy has been used to monitor changes in the Raman spectra corresponding to the different colored states, and cyclic voltammetry has allowed the detection of a redox system in which protons and electrons are exchanged. These findings show that marennine is a suitable stable blue pigment for use in food applications and help in the elucidation of the chromophore structure.     

起垄和施肥对冷浸田土壤氧化还原状况的影响

通过起垄和施肥试验, 研究不同措施对冷浸田土壤氧化还原状况的影响, 以期为冷浸田改良提供数据参考。结果表明, 冷浸田土壤氧化还原电位介于 48.5~ 198.0 mV之间, 远低于正常稻田(450~700 mV)。起垄使0~5 cm土层氧化还原电位有升高趋势, 但使>5 cm土层土壤氧化还原电位降低。冷浸田还原性物质总量变化范围为5.7~15.6 cmol·kg^-1(起垄试验)和7.7~16.0 cmol·kg^-1(施肥试验), 起垄在短期内会提高土壤还原性物质总量, 增施钾肥、锌肥和硅肥会降低土壤还原性物质总量, 而磷肥用量对土壤还原性物质基本无影响。0~25 cm和25~50 cm土层土壤Fe2+含量平均为3 388.92 mg·kg^-1和3 356.39 mg·kg^-1; 起垄60 d后, 土壤Fe²⁺含量随着起垄高度增加而逐渐降低; 与不施肥(CK)、氮磷钾(NPK)处理相比, 施钾量增加20%(NPK₂)、增加硅肥(NPK+Si)和增加锌肥(NPK+Zn)可以大幅度降低土壤Fe²⁺含量; 0~25 cm土层土壤Fe²⁺含量高于25~50 cm土层。 起垄和施肥使冷浸田土壤Mn²⁺含量先降低后升高。     

An integrated sampling/speciation method for inorganic arsenic in soil solution

Arsenic mobility, bioavailability, and toxicity in soil‐water systems are strongly affected by species distribution. In spite of species‐selective analytical tools, results may be biased by postsampling oxidation or reduction of compounds. The scope of this study was to delineate a speciation method for inorganic arsenic integrated with pore‐water sampling to prevent problems related to postsampling species transformation. Experiments were performed with exchange cartridges packed with quaternary amine (nitrate‐form) to separate anionic arsenate from uncharged arsenite. Standard solutions with varied As(III) : As(V) ratios as well as groundwater and soil‐solution samples were studied. Analyses were performed by ICP‐MS using either extraction cartridges directly coupled to the instrument or samples obtained by offline speciation tests. Results showed that As(III) passes the packed bed with the rinsing solution, while As(V) is retained on the column and can be released by elution with 0.25 M NH₄NO₃. Recoveries between 98% and 116% were insensitive to pH variation (pH 3–8) and competing anions. Groundwater samples from a contaminated site yielded recoveries between 92% and 125% when the sum of As(III) and As(V) was compared to total As. Integration of the speciation scheme with pore‐water sampling was tested in a soil‐column experiment. Soil material from a fen site with elevated geogenic As contents was subjected to a varying moisture regime. Reducing conditions during prolonged saturation caused a marked increase of As(III) concentrations. Conversely, when the soil was drained, total As levels decreased and were dominated by As(V). Overall, extraction results with standard solutions and natural samples indicate reliable performance of the method in experimental investigations and field studies.     

Competitive Scavenging of Trace Metals by HFO and HMO during Redox-driven Early Diagenesis of Ferromanganese Nodules (11 pp)

-  Dedicated to Prof. Dr. Ulrich Förstner on his 65th birthdayBackground   Surface complexation models (SCM) alone have yet less successfully reproduced sorption isotherms of hydrous manganese oxides (HMO). This is in part due to the fact that the HMO structure may vary with pH, and also because microbially formed natural HMO has an oxidation number O/Mn 〈 2, i.e. is of non-stoichiometrical composition. The former effect has often led to severe artefacts, such as an under-prediction of metal sequestration at low pH, and non-comparable pK and pHZPC values in literature. The latter effect is of particular importance for environments of varying redox conditions like sediments.Objectives   We propose therefore a new sorption model comprising of amphoteric site SCM, ion exchange due to permanent charge compensation, and solid solution formation, in order to comply at least in part with the redox complexity of HMO phases of stable birnessite- and buserite-type structures. Methods   The model is run by a new Gibbs energy minimization code which is shown to be particularly suitable for such a sorption continuum approach. Results and Discussion   Initial calibration of the model was performed by experimental literature data on simple laboratory systems. Thus parameterised, we simulated on the basis of available field data the effect of redox-driven dissolution of a ferromanganese nodule on the partitioning of metals between the interacting HMO, HFO, and marine water phases. Our scenario model suggests that significant fraction of Mn and other metals, probably 50% or more, may be recycled to water column from the surface of the ferromanganese nodule upon gradual development of the bottom water stagnation, except of Zn for which a by far stronger net retention was found.Conclusion and Outlook   Our model, even if only a first approximation, clearly shows that stagnation in the marine bottom water, once occurring, can drastically change primary element proxy records in ferromanganese nodules, smoothing out any anomalous patterns in the most recent record.     

A field experiment on the influence of the postulated global climatic change on coastal marshland soils

A climatic scenario postulates an increase of atmospheric CO₂, 55 cm water‐level rise combined with a 30 cm higher tidal amplitude for the North Sea. Further, more frequent and stronger west storms, a 2.5°C mean‐annual‐temperature increase together with 15% more rainfall during winter time are to be expected until 2050 due to recent human impact. The possible consequences of the postulated changes in temperature and flooding dynamics were studied for soil formation as well as for soil‐ecological attributes and processes of two sites at Hedwigenkoog foreshore in N Germany: a Hypersali‐tidalic Fluvisol (protothionic, calcaric) (1.5 m asl with >500 annual floods) and a Gleyi‐sali‐tidalic Fluvisol (calcaric) under a salt meadow (2.2 m asl with 70 annual floods). Temperature, water, redox, nutrient and gas dynamics were measured at different soil depths for a period of 2 y. The topsoil of the Gleyi‐sali‐tidalic Fluvisol was permanently heated over an area of 14 m² to simulate a temperature rise of 1.5–2.5°C. The results are discussed in relation to two realistic scenarios. If the ground level of the Gleyi‐sali‐tidalic Fluvisol is heaved up (due to sedimentation) as intensively as the sea level rises, it may be assumed that the soil unit including vegetation cover in principle will not noticeably change. Then, the temperature increase will intensify the activity of soil organisms, bioturbation, and formation of a crumb structure, however, there will be no further accumulation of soil humus. If there was no sedimentation during the next 50 y, the salt meadow itself together with the upper part of the Gleyi‐sali‐tidalic Fluvisol would be destroyed by erosion, and a Hypersali‐tidalic Fluvisol would be formed similar to the studied one.     

Impact of glucose on microbial community of a soil containing pyrite cinders: Role of bacteria in arsenic mobilization under submerged condition

Arsenic transformation and mobilization in a pyrite cinder-polluted soil were studied under submerged conditions both in the presence and absence of glucose. The presence of the carbon source enhanced bacterial activity and a reduction in the redox potential, resulting in release of higher amounts of arsenic iron and manganese in the aqueous phase. Since arsenic solubilization was not concomitant to that of iron, desorption rather than dissolution was found to be the main mechanism controlling its release from pyrite cinders. Arsenate was reduced to arsenite whose presence increased during the time course of the experiment. Denaturing gradient gel electrophoresis analysis of 16S rRNA genes of the total bacterial community revealed that the addition of glucose stimulated uncultivable populations of Flavobacterium and Paenibacillus. The isolation technique enabled the characterisation of nineteen arsenic-resistant bacteria, mostly related to the facultative aerobic genera Bacillus, Paenibacillus, Staphylococcus and to Rhodococcus and Micromonospora. Most of them contained putative arsenate reductase and/or arsenite efflux pump as indicated by the presence of ArsC and/or ArsB genes. Four strains showed the ability to reduce arsenate by an intracellular detoxification mechanism, and one strain was able to oxidize arsenite, indicating that bacteria with the ability to oxidize or reduce arsenic are ubiquitous in soils. The findings confirm that bacterial activity was responsible for the arsenic reduction causing the solubilization of the metalloid from pyrite cinders to aqueous phases. Reducing conditions, such as those present in flooded soils in the presence of readily utilizable carbon sources could induce arsenic mobilization.