硫素对水稻根系铁锰胶膜形成及吸收镉的影响

添加外源镉污染水稻土进行池栽试验,施入不同形态及数量的硫肥(单质硫、石膏),研究硫素对水稻根系铁锰胶膜的形成及对水稻吸收镉的影响.结果表明,整个水稻生育期内,土壤溶液Eh范围在-200~100 m V之间;p H在6.9~7.9之间;pe+p H在4~10之间.水稻根表胶膜以Fe膜为主,其质量分数达到5 000~13 000 mg·kg-1,Mn膜的质量分数相对较小,为170~580 mg·kg-1.在孕穗期高硫量处理与低硫量处理的铁胶膜质量分数分别为9 400 mg·kg-1和8 600 mg·kg-1,高硫量处理比低硫量处理可生成更多的铁胶膜;而根表锰胶膜的数量差异主要表现在分蘖期,单质硫和石膏硫处理的锰胶膜质量分数分别为600 mg·kg-1和400 mg·kg-1,达到显著差异水平,单质硫比石膏硫更易促进水稻根表锰胶膜的形成.胶膜对于Fe2+过量吸收有一定阻控作用,对Mn2+作用不显著.水稻根表胶膜吸附Cd的质量分数在分蘖期为78.8~131.1 mg·kg-1,孕穗期16.6~21.1mg·kg-1,成熟期3.0~9.2 mg·kg-1.在分蘖期与孕穗期,高硫量处理比低硫量处理的吸附量高,在成熟期反之.采用ACA方法浸提铁锰胶膜内的Cd测定值并不能真实地表明胶膜实际固定Cd的质量分数.水稻体内各部位Cd的质量分数表现为根茎叶籽粒.一定量的施硫能有效减少水稻各器官中Cd的质量分数.对于根和茎叶,单质硫在成熟期以前效果好于石膏硫;对于籽粒,石膏硫效果更佳.一定量的硫肥,能有效阻碍Cd从水稻根部向茎叶与籽粒的转移.对于茎叶,在孕穗期单质硫和石膏硫的Cd转移系数分别为0.13和0.25,差异显著,单质硫能更好地阻碍Cd的转移;对于籽粒,石膏硫的阻碍效果更好.     

醌基功能型高分子生物载体(PET-AQS)制备及催化生物反硝化特性研究

通过化学合成,将蒽醌磺酸钠(AQS)固定在聚对苯二甲酸乙二醇酯(PET)上形成醌基功能型高分子生物载体并研究其在生物反硝化上的应用.通过红外光谱衰减全反射法(ATR-IR)和能谱(EDS)分析,醌基基团成功固定在高分子表面,且醌基质量摩尔浓度为0.140 6 mmol·g-1.醌基功能型高分子生物载体(PET-AQS)能加速生物反硝化,且速率常数Kx与载体投加浓度呈零级反应动力学.在投加PET-AQS 0.056 2 mmol的反硝化体系中,循环使用10次,反硝化速率均是空白体系的1.2倍以上,表明PET-AQS具有良好的重复利用稳定性,有利于实际应用.     

Methane emissions from rice fields under continuous straw return in the middle-lower reaches of the Yangtze River

A three-year experiment was conducted in the middle-lower reaches of the Yangtze River in China to study the influence of continuous wheat straw return during the rice season and continuous rice straw return in wheat on methane (CH 4 ) emissions from rice fields in which, the rice-wheat rotation system is the most dominant planting pattern. The field experiment was initiated in October 2009 and has continued since the wheat-growing season of that year. The analyses for the present study were conducted in the second (2011) and third (2012) rice growing seasons. Four treatments, namely, the continuous return of wheat straw and rice straw in every season (WR), of rice straw but no wheat straw return (R), of wheat straw but no rice straw return (W) and a control with no straw return (CK), were laid out in a randomized split-plot design. The total seasonal CH 4 emissions ranged from 107.4 to 491.7 kg/ha (2011) and 160.3 to 909.6 kg/ha (2012). The increase in CH 4 emissions for treatments WR and W were 289% and 230% in the second year and 185% and 225% in the third year, respectively, in relation to CK. We observed less methane emissions in the treatment R than in CK by 14%-43%, but not statistically significant. Treatment R could increase rice productivity while no more CH 4 emission occurs. The difference in the total CH 4 emissions mainly related to a difference in the methane flux rate during the first 30-35 days after transplant in the rice growing season, which was caused by the amount of dissolved oxygen in paddy water and the amount of reducible soil materials.     

Transformation of N-, O-, and S- heterocycles (NOSHs) in estuarine sediments: Effects of redox potential and sediment particle size

The transformation of 19 N-, O-, and S- heterocycles (NOSHs) was examined in estuarine sediment-water microcosms. The effects of redox potential (Eh) and sediment particle size on compound transformation rates were evaluated, and stable products were identified. Results from stirred, controlled Eh/pH microcosms (CEPMs) showed that most of the NOSHs were significantly transformed under oxidized and reduced conditions over 15 week incubations, and the resulting product distributions were similar. In general, the rates and extent of transformation were greater in oxidized sediments of low surface area vs. those with high particle surface area and reduced redox conditions. Further experiments in sealed, unstirred microcosms also showed that NOSH transformation proceeded more slowly and on fewer compounds in fine vs. coarser grained sediments under oxidized conditions. Unlike the stirred systems, however, NOSH transformation rates were similar or greater under reduced vs. oxidized conditions. Thus, reduced, methanogenic clay of high surface area displayed some of the fastest rates of NOSH transformation. Data from liquid-liquid partitioning experiments suggested that this effect was related to the formation of NOSH complexes with iron and perhaps other redox-active metals in sediments.     

Iron oxidation-reduction and its impacts on cadmium bioavailability in paddy soils: a review

Redox conditions in paddy soils may vary as they are submerged and drained during rice growth. This change may bring about reductive dissolution of iron (Fe) oxides and subsequent formation of secondary Fe-bearing minerals in rice paddies. The mobility and bioavailability of metal contaminants such as cadmium (Cd) in paddy soils are closely related to the chemical behaviors of Fe. Therefore, in this paper, advances in the study of paddy Fe redox transformations and their effects on Cd availability to rice are briefly reviewed. Current concepts presented in this review include the forms of Fe in paddy soils, the reactions involved in Fe oxidation-reduction, chemical factors affecting Fe redox processes, Cd availability to rice and the impacts of Fe transformation on Cd uptake and translocation in rice. Prospects for future research in this area are also discussed.     

Fe2+/Fe3+氧化还原系统预处理色酚废水的试验

介绍了采用Fe2+/Fe3+氧化还原系统对色酚废水进行预处理的工艺流程,确定了最佳工艺参数。研究结果表明,当还原反应的pH为9~11,反应时间20 min;氧化反应的pH为5.5~6,反应时间为30 min;FeSO4.7H2O加入量为5 kg/t废水时,CODCr去除率为75%~80%,并且处理后出水的色度、苯胺含量有明显改善,可生化性大大提高,十分有利于后续的生化处理。     

沈阳黄家傍河水源地河水入渗过程中氧化还原分带规律

在分析沈阳市黄家傍河水源地地质及水文地质条件的基础上,通过场地监测-室内实验相结合的方法,对黄家水源地河水入渗过程孔隙水氧化还原分带规律进行研究.结果表明：辽河河床沉积带在河水入渗途径上存在氧化还原分带,在水流垂向入渗的初始0~20cm、20~80cm、80~90cm及后续范围内依次存在O₂-NO₃^-混和还原带、锰氧化物还原带和铁氧化物还原带;反应中河水中溶解有机碳不能提供足够的电子还原氧化剂,溶解至入渗水流中的沉积物有机碳与河水溶解有机碳一起作为碳源参与了氧化还原反应.     

河水-地下水交互带内砷及金属的自然衰减过程

在简单介绍污染物自然衰减作用定义的基础上,重点分析了河水-地下水交互带内As和以矿山废水为来源的金属污染物的自然衰减行为:主要包括吸附作用,氧化还原作用,生物转化作用等。其中详细介绍了金属Fe、Al的氢氧化物/氧化物对As化合物和其他金属如Cd、Cu和Zn等的吸附作用;Ca2+、Fe2+、磷酸盐、重碳酸盐等阴阳离子和天然有机质对吸附作用的影响;金属微生物氧化还原作用以及微生物作用下As(V)与As(III)的相互转化过程。研究发现,阳离子可以增强金属的吸附作用,阴离子主要是参与竞争吸附;天然有机质对金属吸附过程的抑制作用阻碍金属的固定;交互带内氧化还原条件的变化可以引起一系列的氧化还原反应;微生物催化还原不利于As的自然衰减。最后指出目前河水-地下水交互带内金属污染物衰减过程研究存在的问题以及今后的发展方向。     

垃圾渗滤液污染含水层不同氧化还原带沉积物的pH缓冲能力

通过砂柱模拟实验研究含水层沉积物的pH缓冲能力及其在不同氧化还原带中的变化.结果表明,pH缓冲容量的本底值为324.93.pH-1mmol/kg,其中阳离子交换缓冲容量、碳酸钙缓冲容量、硅酸盐缓冲容量和次级缓冲容量的本底值分别为41.77.pH-1、86.53.pH-1、47.33.pH-1和149.31.pH-1mmol/kg.产甲烷带/硫酸盐还原带(MGZ/SRZ)、铁还原带(IRZ)、硝酸盐还原带(NRZ)和氧还原带(ORZ)中总的pH缓冲容量相对于本底值依次分别增加了12.4%、10.8%、19.8%和11.1%;各氧化还原带沉积物中的交换性阳离子(CEC)和交换性盐基离子(BEC)均小于本底值的11.59.pH-1和8.52.pH-1mmol/kg,各氧化还原带沉积物的盐基饱和度先升高后降低,都高于本底值的63.47%.因此,含水层沉积物有较强的pH缓冲能力.对垃圾渗滤液污染含水层不同氧化还原带沉积物pH缓冲能力的研究可为污染场地的修复提供理论依据.     

含水层介质对垃圾渗滤液污染缓冲性研究

通过土柱模拟实验研究含水层介质对垃圾渗滤液污染的pH缓冲和氧化还原缓冲性能.结果表明,碳酸钙对pH缓冲起重要作用,随着污染程度的加重,碳酸钙缓冲体系的缓冲容量逐渐增大,从背景值的1.62·pH^-1 mmol/kg增加到41.3·pH^-1 mmol/kg.随着污染程度的加重,含水层介质的氧化容量（OXC）减小,而还原容量（RDC）升高.在未受污染的介质中,Fe³⁺是OXC的主要组成,约占OXC的70.5％;TOC是RDC的主要组成,约占RDC的98.7％.物质的存在形态也与污染程度有关,在污染源附近大部分无定型态和部分晶体态Fe³⁺被还原,而且还原产物主要以FeCO₃和FeS形式沉淀;生成Fe²⁺的沉积使得可离子交换态Fe²⁺含量由未受污染的介质中的0.5％升高至3％.因此,Fe³⁺是含水层介质中主要的氧化还原缓冲剂.