黄河中下游湿地土壤铁还原氧化过程的温度敏感性

土壤中铁的还原氧化过程因与重金属的生物有效性、有机污染的降解及含碳温室气体排放等环境问题关系密切而备受关注。温度可能通过影响铁还原菌或者Fe(II)氧化菌的活性、底物的生物可用性等而影响铁的还原过程。以黄河中下游地区新乡市原阳大米产区的湿地土壤为样品,利用厌氧泥浆控温培养试验方法研究了黄河中下游湿地中土壤铁还原氧化过程的温度敏感性。结果表明:黄河中下游湿地土壤铁的还原容量在16~31℃范围内不受温度影响,但在16~40℃之间升高温度可显著增加铁还原过程的最大速率、速率常数,亦可缩短最大速率出现的时间。铁还原的温度敏感系数介于1.18~3.05之间,且随温度上升而升高。光照可降低铁还原的温度敏感性,平均降幅39.0%。光照时土壤中Fe(II)氧化对温度不敏感。光照条件和铁氧化物的种类和数量可能是影响土壤有机碳矿化的因素之一。研究结果对于深入理解土壤铁的生物地球化学循环及其与土壤呼吸的关系具有重要意义。     

土壤微生物铁循环及其环境意义

铁是土壤中重要的高活性高丰度元素。铁的生物地球化学循环包括铁还原与亚铁氧化两个过程,需要微生物提供基本驱动力,已经成为陆地表层系统研究的国际热点。铁循环控制着土壤有机物矿化、反硝化、甲烷产生、重金属固定等环境过程,是连结土壤养分循环与污染物转化的纽带。从生物地球化学循环的角度,综述了微生物作用下的铁还原、亚铁氧化过程及其主要微生物类群,重点论述了厌氧条件铁还原与亚铁氧化的环境效应及其地球化学机理,以及铁还原与亚铁氧化两个过程的协调及其调控因子。本文将有助于深入理解地球表层的关键环境过程与驱动机制。     

湿地生物地球化学研究概述

湿地有其独特的生物地球化学循环,其间许多化学迁移和转化过程不为其它生态系统所共享。湿地土壤在淹水时形成强还原区,但在水—土界面上常有一氧化薄层。发生于还原环境中的C,N,P,S,Fe,Mn的转化都影响着物质对生态系统的有效性;一些化学转化还会导致毒性环境,许多化学转化由微生物种群来调节。化学物质经降水、地表径流、地下水和潮汐等水文途径被输送至湿地中,降水途径占优势的湿地一般养分较贫乏,经另外3个途径输入湿地的化学物质的浓度变化较大,并非所有的湿地都是养分的汇,而且其季节之间、年际之间的模型也不一致。尽管对毗邻的生态系统的直接影响难以定量化,湿地通过有机物质的输出常与毗邻生态系统进行化学耦合。湿地与陆生、水生生态系统相类似,因为它们都可能是富营养或贫营养系统;当然它们之间也有一些差异,特别是在沉积物贮存养分以及植被在不同养分循环中的功能方面差异较大。     

人工湿地中氨氮反应与pH变化关系的研究

在三江平原气候条件下,配制以NO-3-N、NH+4-N和P(PO-4-P为主要成分的模拟进水,通过间歇运行方式,考察潜流人工湿地模拟系统中氨氮反应与pH变化的关系.结果表明,湿地系统对高pH值进水具有缓冲作用.在运行期间,土壤-炉渣湿地上层pH小于下层pH值,土壤湿地上层pH大于下层pH值.随着停留时间(HRT)的增加和NH+4-N浓度的降低,湿地系统中的pH值呈现规律性变化,土壤-炉渣湿地的氧化还原电位(ORP)与pH值呈负相关.湿地系统中pH值变化曲线的拐点可作为NH+4-N反应结束的指示参数.     

土壤硫的氧化还原及其环境生态效应

硫在土壤中的氧化还原不仅直接影响其在水、大气、生物、岩石圈的交换和循环,而且对生态环境产生影响。综述了土壤中发生的硫的氧化还原过程及硫的氧化还原过程产生的环境生态影响,最后展望了硫的氧化还原及其相关过程的研究前景。     

土壤氧化还原过程及其生态效应

对土壤中发生的主要氧化还原反应进行了概括，详细讨论了土壤氧化还原过程对土壤圈物质循环以及生态环境的影响。     

新书《土壤的氧化还原过程及其研究法》介绍

中国科学院南京土壤研究所丁昌璞、徐仁扣等著的《土壤的氧化还原过程及其研究法》一书已于2011年11月由科学出版社出版。全书44.8万字,327页,每册定价68元,共分十三章,依次是:氧化还原状况;铵的氧化-硝化反应;硝酸盐的还原-反硝化反应;有机还原性物质;铁;锰;硫;砷的氧化还原反应;氧化锰与酚类化合物的氧化还原;铁、锰的有效性与氧化还原状况;稻根和钾与还原性物质的相互作用;氧化还原过程与土壤发生;氧化还原反应与环境污染。本书是国内目前该研究领域的第一部专著。     

沼泽湿地开垦对土壤水热条件和性质的影响

湿地具有重要的生态和环境功能.三江平原沼泽湿地的大面积垦殖,已对区域生态平衡及气候环境产生了一定的影响.湿地开垦后,土壤水、热条件发生较大变化,土壤温度的增高及氧化-还原条件的改变,促进了土壤有机质的分解和土壤呼吸通量的增大.土壤有机碳、氮素含量随湿地开垦及开垦年限的增加而不断降低.沼泽湿地开垦初期5～7年,土壤有机碳及其它营养元素的含量变化幅度较大,持续耕作15～20年后,土壤有机碳损失曲线趋于平缓.湿地开垦后,土壤有机质输入量的减少及分解作用加强导致土壤容重和比重的增大,其变化趋势与土壤有机碳损失趋势相一致.     

湿地土壤微生物群落结构与多样性分析方法研究进展

湿地生态系统在物质循环、能量流动、污染物降解等方面具有重要的生态功能和环境价值。近年来,在气候变化、盐渍化等自然因素以及人类活动的干扰下,湿地生态系统健康受到威胁。微生物是湿地生态系统中的重要组成部分,它在湿地物质循环、能量流动、有机物分解、土壤肥力的形成和污染物的降解等方面起着重要作用。本文通过对微生物多样性分析方法在湿地土壤微生物研究中的应用现状进行综述,以期为微生物多样性分析技术在湿地微生物研究中更好地应用提供理论参考。     

微生物影响稻田土壤中砷转化研究进展

稻田砷污染是一个全球性环境问题。稻米是以大米为主食的人群砷暴露的主要途径，稻米砷含量超标，会对动物和人体健康造成威胁。微生物是影响砷环境生物化学行为的重要角色，在植物-土壤-微生物系统的砷循环中发挥着重要作用。了解微生物对砷在土壤-水稻系统中的生物化学循环的影响，能够为稻田砷污染的有效治理提供理论基础。本文综述了砷氧化微生物、砷还原微生物以及砷甲基化微生物分别对砷氧化、还原和甲基化过程的影响（直接作用），并总结了微生物通过间接影响铁、硫的环境生物化学循环，进而影响稻田-水稻系统中砷的赋存形态及其转化与迁移的过程。最后，本文归纳了砷污染农田微生物修复技术的相关研究进展，并提出了研究展望。     

Effects of Vegetation Removal and Urea Application on Iron and Nitrogen Redox Chemistry in Riparian Forested Soils

Riparian wetlands are subject to nitrogen enrichment from upgradient agricultural and urban land uses and also from flooding by nitrogen-enriched surface waters. The effects of this N enrichment on wetland soil biogeochemistry may be mediated by both the presence of plants and the presence of redox-active compounds, specifically iron oxides in the soil. Despite the extensive research on wetland N cycling, the relative importance of these two factors on nitrogen is poorly known, especially for forested wetlands. This study evaluates the responses of the N and the Fe cycles to N enrichment in a riparian forested wetland, contrasting vegetated field plots with plots where the vegetation was removed to test the role of plants. Furthermore, in vitro anaerobic incubations of the experimental soils were performed to track Fe chemical changes over time under anoxic or flooded conditions. Wetland soils treated with N in form of urea, as expected, had significantly higher amounts inorganic nitrogen. In the soils where vegetation was also removed, in addition to inorganic nitrogen pool, increase in organic nitrogen pool was also observed. The results demonstrate the role of vegetation in limiting the effects excess urea has on different soil nitrogen pools. Results from anaerobic incubation of the experimental soils demonstrated the effects of N enrichment on the wetland Fe cycle. The effects of excess nitrogen and the role of vegetation on the Fe cycle in riparian wetland soil became more evident during anaerobic incubation experiments. At the end of the field experiment, Fe concentrations in the soils under the treatments were not significantly different from the control soils at the 5% confidence level. However, during the anaerobic incubation experiment of soils collected at the end of the experiment from these plots, the N-enriched soils and the unvegetated soils maintained significantly elevated concentrations of reducible Fe(III) for the initial 2-week period of incubation, and the soils collected from the plots with both the treatments had the highest Fe(III) concentrations. After 20 days of incubation, however, the Fe(III) concentrations decreased to the similar concentrations in all the incubated soils. The study clarifies the roles vegetation play in mediating the effects of N enrichment and also demonstrates that N enrichment does affect wetland redox cycle, which has strong implications on ecosystem services such as water quality improvement.     

Photocatalytic Decolorization of Commercial Acid Dyes using Solar Irradiation

Four wetland plants were selected to study the effect of Fe plaque formation on phosphorus (P) accumulation in the rhizosphere and P uptake. There were significant positive correlations between the sorbed Fe content in the rhizosphere and the Fe plaque concentration (r ²?=?0.8454, p?<?0.01) and between P accumulation and the amount of the sorbed Fe in the rhizosphere (r ²?=?0.8460, p?<?0.01). The concentration of the Fe plaque on the root surface of four wetland plants species tested followed the order of Zizania cedu Ciflora Turez > Scirpus tabernaemontani Gmel > Iris pseudacorus Linn > Canna indica Linn. The Fe plaque formation increased P uptake, apparently through enhancing the diffusion of P into the roots of the wetland plants; this resulted in increased P concentration in shoots. However, this effect decreased in the higher Fe plaque concentration status, apparently due to physical blocking and immobilization of P by Fe plaque. Therefore, adequate surface coverage of roots of wetland plant by the Fe plaque would increase the uptake of P by wetland plants, which depend on the optimum amendment of Fe. These effects also varied with wetland plant species.     

湿地植物铅的富集特征及根际铅移动性的影响因素研究

【目的】 揭示湿地植物铅的富集特征及根际铅移动性影响因素的作用机理,为人工湿地修复重金属污染水体提供理论指导和依据。 【方法】 通过根箱法研究了五种挺水湿地植物 (大叶皇冠草、黑籽荸荠、圆币草、草龙、小婆婆纳) 根际 pH、氧化还原电位 (Eh)、Fe2+ 和 Fe3+ 浓度、铅 (Pb) 的化学形态及移动性的变化。 【结果】 与非根际相比,五种植物根际pH下降,Fe2+ 和 Fe3+ 浓度显著下降,Eh显著升高,Pb的移动性显著降低 (P<0.05)。与非根际相比,根际pH下降幅度为 0.1～0.4个单位,根际Fe2+和 Fe3+浓度下降幅度为0.6～2.7 mmol/kg。土壤中铅的存在形态主要以残渣态为主 (36.39%～47.54%),其次是铁锰氧化物结合态 (30.16%～41.64%)、有机质结合态 (8.85%～15.08%) 和碳酸盐结合态 (6.89%～12.46%)。五种湿地植物根际Pb的移动性降低的主要原因是根际碳酸盐结合态Pb含量显著下降,其中大叶皇冠草受根际pH、Eh、Fe3+和Fe2+的影响导致其根际Pb移动性降低效应最为显著。 【结论】 五种供试植物Pb主要分布在根部;根表富集的铁膜数量显著高于锰膜数量;供试植物根际Fe3+含量与Pb的移动性因子呈极显著正相关,湿地植物根系铁氧化能力对降低其根际重金属的移动性有重要作用。本研究为人工湿地修复重金属污染水体提供了有力的理论依据。      

一株在微生物燃料电池中可以利用喹啉发电的产电假单胞杆菌Q1的产电特性研究

A rhizobox experiment was conducted to compare iron (Fe) oxidation and changes of pH, redox potential (Eh) and fractions of zinc (Zn) and lead (Pb) in rhizosphere and non-rhizosphere soils of four emergent-rooted wetland plants (Echinodorus macrophyllus, Eleocharis geniculata, Hydrocotyle vulgaris and Veronica serpyllifolia) with different radial oxygen loss (ROL) from roots. The results indicated that all these wetland plants decreased pH and concentration of Fe(Ⅱ) but increased the Eh in the rhizosphere soils. Pb and Zn were transformed from unstable fractions to more stable fractions in the rhizosphere soils, so decreasing their potential metal mobility factors (MF). Among the four plants, E. macrophyllus, with the highest ROL and root biomass, possessed the greatest ability in formation of Fe plaque and in the reduction of heavy metal MFs in the rhizosphere soil. Wetland plants, with higher ROLs and root biomass, may thus be effective in decreasing potential long-term heavy metal bioavailabilities.     

Elemental composition of the rice plant as affected by iron toxicity under field conditions

Abstract

Iron (Fe) toxicity is a major nutrient disorder affecting the production of wetland rice in the humid zone of West Africa. Little attention has been given to determining the macro‐ and micronutrient composition of rice plants grown on wetland soils where Fe toxicity is present although results from such study could provide useful information about the involvement of other nutrients in the occurrence of Fe toxicity. A field experiment was conducted in the 1997 dry season (January‐May) at an Fe toxic site in Korhogo, Ivory Coast, to determine the elemental composition of Fe tolerant (CK 4) and susceptible (Bouake 189) lowland rice varieties without and with application of nitrogen (N), phosphorus (P), potassium (K), and zinc (Zn). For both Fe‐tolerant and susceptible varieties, there were no differences in elemental composition of the whole plant rice tops, sampled at 30 and 60 days after transplanting rice seedlings, except for Fe. All the other nutrient element concentrations were adequate. Both Fe‐tolerant and susceptible cultivars had a high Fe content, well above the critical limit (300 mg Fe kg^‐1 plant dry wt). These results along with our observations on the elemental composition of rice plant samples collected from several wetland swamp soils with Fe toxicity in West Africa suggest that “real”; iron toxicity is a single nutrient (Fe) toxicity and not a multiple nutrient deficiency stress.     

Responses of nitrogen cycling and related microorganisms to brackish wetlands formed by evapotranspiration

Elevated evapotranspiration due to warmer air temperature could raise salinity and nutrient levels of some inland wetlands, potentially impacting nitrogen cycling. To characterize the impact of high evapotranspiration on soil microbial nitrogen cycling in inland wetlands, we compared freshwater and brackish marsh(or non-marsh) wetlands in terms of sediment ammonia-oxidizing rate(AOR), denitrifying rate(DR), and related microbial communities in a typical inland basin, the Hulun Lake basin, in Chi...     

Root and Leaf Ferric Chelate Reductase Activity in Pond Apple and Soursop

Abstract

Root and leaf ferric chelate reductase (FCR) activity in Annona glabra L. (pond apple), native to subtropical wetland habitats and Annona muricata L. (soursop), native to nonwetland tropical habitats, was determined under iron (Fe)-sufficient and Fe-deficient conditions. One-year-old seedlings of each species were grown with 2, 22.5, or 45 µM Fe in a nutrient solution. The degree of tolerance of Fe deficiency was evaluated by determining root and leaf FCR activity, leaf chlorophyll index, Fe concentration in recently mature leaves, and plant growth. Root FCR activity was generally lower in soursop than in pond apple. Eighty days after plants were put in nutrient solutions, leaf FCR activity of each species was lower in plants grown with low Fe concentrations (2 µM) than in plants grown with high (22.5 or 45 µM) Fe concentrations in the nutrient solution. Leaves of pond apple grown without Fe became chlorotic within 6 weeks. The Fe level in the nutrient solution had no effect on fresh and dry weights of soursop. Lack of Fe decreased the leaf chlorophyll index and Fe concentration in recently matured leaves less in soursop than in pond apple. The rapid development of leaf chlorosis in low Fe conditions and low root and leaf FCR activities of pond apple are probably related to its native origin in wetland areas, where there is sufficient soluble Fe for adequate plant growth and development. The higher leaf FCR activity and slower growth rate of soursop compared to pond apple may explain why soursop did not exhibit leaf chlorosis even under low Fe conditions.     

Assessing the Removal Efficiency of Zn, Cu, Fe and Pb in A Treatment Wetland Using Selective Sequential Extraction: A Case Study

The accumulation and speciation of Zn, Cu, Fe and Pb in the sediments of an artificial surface-flow wetland used to treat domestic wastewater near Christchurch, New Zealand, were examined. Water metal concentrations and total suspended solid (TSS) content were determined at the inflow and outflow both in winter and summer, and metal concentrations were analysed in shoots and roots of selected plants. Water and sediment data suggest that the wetland is acting as a sink for Zn, Cu and Pb, while Fe uptake is minimal and the wetland appears to be releasing Fe in the winter. Metal concentrations in the most mobile fractions (exchangeable and bound to carbonates) are negligible. Cu is mostly associated with the organic/sulphide phase, whereas Zn and Pb show a strong affinity for hydroxides and organics/sulphides. A large fraction of all metals is also present in the residual phase, and is therefore unlikely to be released into the overlying water. Metal concentrations are below the low trigger values of the ANZECC sediment quality guidelines, except for Pb near the inflow. However, results of sequential extraction suggest that a significant proportion of Pb occurs in the detrital phase and is therefore not bio-available. Metal concentrations were higher in the roots than in the shoots of both Juncus sp. and Lythrum hyssopifolia. This study shows that, although metal concentrations are low, TSS and metals, except Fe, are effectively removed by the wetland system. The low removal rate of Fe is possibly due to the young age of the wetland and low loading rates.     

银川平原草甸湿地表层土盐分累积特征

银川平原湿地属于典型的绿洲湿地,不仅是生物多样性的载体,还有具有重要的环境调节功能及较高的生产力,但由于其地处于易发生盐分累积的区域,因此,找出银川平原草甸湿地土壤盐分的空间累积特征,对了解银川平原水盐迁移过程对湿地生态系统的影响十分重要。该文采用野外调查、室内分析的方法,研究了银川平原草甸湿地植被的分布特征,草甸湿地土壤盐化等级的划分,盐分累积状况,该研究共设置样地57个,样方123个,根据传统的分类方法将研究区植物群落划分为3个植被型,8个植被亚型,27个群系。根据土壤表层全盐含量0~20 cm,把研究区土壤划分为5个等级:Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ,它们对应的含盐量分别为≥10、[4~10)、[2~4)、[1~2)和1 g/kg。银川平原草甸湿地土壤盐分呈自南向北逐渐增加的空间变化;不同草甸植被类型的含盐量大小为盐生草甸典型草甸湿生草甸;不同地形部位草甸的盐分含量表现为干湖滩洪泛平原堤外湖滩湿湖滩渠边沙滩,地下水埋深和水盐循环过程是盐分分布特征的决定性因素。     

Effects of artificial aeration and iron inputs on the transformation of carbon and phosphorus in a typical wetland soil

Purpose

Artificial aeration changes the redox conditions at the soil surface. The introduction of iron (Fe) into wetlands can influence carbon (C) and phosphorus (P) cycling under the fluctuating redox conditions. However, artificial Fe introduced into wetlands is uncommon, and there are no Fe dose guidelines. We compared aerobic and anaerobic conditions to test the hypothesis that Fe addition can, although redox-dependent, affect P forms and the coupling of organic C.

Materials and methods

Twenty-four intact soil cores were collected randomly from a lacustrine wetland of Lake Xiaoxingkai. And representative and homogeneous seedlings of Glyceria spiculosa were collected. The incubation was designed with two treatment factors: Fe/P ratio (5 or 10) and high and low dissolved oxygen (DO) concentrations (>?6 and <?2 mg L^?1, respectively). Four groups with three replicates were separated randomly and labeled as aerobic + plant treatment, anaerobic + plant treatment, and aerobic or anaerobic treatment (control).

Results and discussion

The DO concentrations were stratified, decreasing with soil depth and increasing with time, especially under aerobic conditions. The Eh values generally increased with fluctuations under aerobic conditions. The artificial aeration substantially changed the redox environment at the water–soil interface. Of the total P, 45% was in the reactive Fe-bound P, indicating that Lake Xiaoxingkai had high internal P loading. No significant differences were observed in total Fe, amorphous Fe, and organic C at the soil surface between the two Fe/P ratios; however, a significant difference in free Fe was observed. And soil amorphous Fe was found to be a significant correlation with soil organic C, indicating that iron oxides were related with the soil chemical properties.

Conclusions

After short-term incubation, Fe addition can affect the cycling of major elements in wetlands, although this effect is redox dependent. Excessive Fe doses may result in regional environmental risks, such as eutrophication and C sinks of wetland ecosystems. Large-scale controlled experiments are needed to fully understand the behaviors of soil elements in wetlands.