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61.
以连续提取法研究了我国南方主要酸性土壤铝的形态及其分布特点,探讨了不同铝形态之间的关系及其与母质、成土过程、环境条件的联系。还研究了土壤酸化对铝形态转化的影响.并以连续提取法提取的三种铝形态(交换性铝、活性羟基铝,有机络合态铝)来讨论现今常用的Al。(Tamm溶液提取)和Ald(DCB溶液提取)所可能包含的实际土壤铝形态,分析表明,Al0和Ald无明确的形态意义,只是上种由操作定义的多形态组成的混合物。 相似文献
62.
Almeida CM Mucha AP Vasconcelos MT 《Environmental science and pollution research international》2005,12(5):271-277
Goal, Scope and Background The presence or absence of vegetation can condition sediment characteristics. The main aim of this work was to investigate
the influence of the sea rush Juncus maritimus on metal (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) availability to organisms living
on or in estuarine sediments, from Douro River (NW Portugal), by comparing the characteristics and chemical behaviour of rhizosediments
(collected within the plant assemblage) and those of sediment (collected around the plant). In order to evaluate whether and
how sediment characteristics condition the role of plants on metal availability, sandy and muddy sediments colonised by J.
maritimus were studied in parallel.
Methods Metal availability was estimated by enzymatic digestion with pepsin (ED), which may provide an estimate of metal availability
to organisms living at estuarine sediments. Nevertheless, since no consensus exists yet on the most suitable methodologies
to estimate metal bioavailability in sediments, two more conventional approaches, BCR sequential extraction (SE) and AVS/SEM
model, were also used, in parallel, and the information these approaches provided was compared with that provided by ED. Total-recoverable
metal contents were determined by atomic absorption spectrophotometry after sediment digestion using a high-pressure microwave
system.
Results and Discussion Plants could concentrate metals around its roots and rhizomes. In addition, they were capable of oxidizing (release of oxygen
by the roots) the anaerobic medium surrounding their roots in muddy sediment (reducing AVS). As sulphide oxidation renders
metals (Cd, Cu, Ni, Pb and Zn) into more soluble forms, according to the AVS/SEM model, metals from muddy sites would be more
available in rhizosediment than in sediment. The SE approach led to a similar conclusion. Nevertheless, the results provided
by ED pointed at opposite conclusion, particularly for Cd and Zn, indicating less availability at rhizosediments than in the
surrounding sediment. ED results were interpreted as a consequence of an enrichment of the rhizosediment in organic ligands
exuded by the roots or liberated by dead plants. The effect of complexation of metals by organic compounds, which ED could
not decompose/dissolve, seemed to overcome that caused by sediment oxidation. In general, a comparison of the information
about metal availability by ED, SE, AVS/SEM, showed that it did not always match and in few cases it was even contradictory.
Conclusion and Outlook Therefore, a thorough evaluation of the metal availability in sediments requires a combination of different chemical approaches,
so as to take into consideration differences in ways of organism exposure (interstitial water and/or ingestion of sediment
particles).
- * The basis of this peer-reviewed paper is a presentation at the 9th FECS Conference on 'Chemistry and Environment', 29 August
to 1 September 2004, Bordeaux, France. 相似文献
63.
研究了生物废水处理应用于序半连续式反应器(SFBR)工艺中的微生物生长、硝化和反硝化动力学。基于活性污泥1号模型(ASMNo. 1)中的原理和结论,导出了在有氧阶段和缺氧阶段微生物生长速率、铵、硝酸盐、易生物降解基质等的反应速率及它们的物料平衡方程。在实验的基础上,对模型中的各参数采用了合适的方法进行参数估值,即:龙格库塔法解常微分方程组和黄金分割法搜索最小误差,该模型的最小误差ε≈4 799;得出了应用于本工艺中数学模型中的各动力学参数和化学计量系数,如KS 39. 997,KNO 0 .397,KNH 1 997,KOA 0 .404,KOH 0. 297, μA 0 .0026,μH 0. 207,YA 0 .24,YH. 0 6。 相似文献
64.
好氧颗粒污泥实现同步硝化反硝化 总被引:25,自引:0,他引:25
采用人工配制的模拟生活污水,通过对运行条件的调控,在序批式反应器(SBR)中培养出了高活性的好氧颗粒污泥,颗粒污泥浓度达到4.55g/L以上,SVI值在32.5左右,反应器对于COD、NH3—N的去除率分别在83.6%—92.8%和82.3%—98.5%之间。实验结果表明:由于好氧颗粒污泥的存在,SBR反应器内发生了同步硝化反硝化(SND)反应,而不是通常所认为的顺序式硝化反硝化(SQND)反应。 相似文献
65.
Changes in speciation and mobility of As by indigenous bacteria in As-contaminated sediments (339 mg/kg) from an abandoned
Au–Ag mine area in Korea were investigated after biostimulation with a variety of carbon sources, including acetate, lactate
and glucose in batch experiments. Sequential extraction analysis designed to determine the form of As occurrence revealed
that 40 and 47% of As were present in the sediment as Fe-associated and residual fractions, respectively. After 22-day incubation
with acetate and lactate, the presence of indigenous bacteria increased the amount of total dissolved As from both Fe-associated
and residual fractions in the sediment. More than 99% of dissolved As existed as As(V) in biotic slurries in contrast to sterile
controls (less than 50% of total dissolved As), which indicated that indigenous bacteria transformed some dissolved As(III)
to As(V). In real environments, depending on the pH, microbially-produced aqueous As(V) may be either immobilized through
adsorption or reduced to As(III) after migration to the anoxic subsurface. 相似文献
66.
67.
68.
污泥的可生物降解性能由其有机组分的生物可及度和组分分子的复杂度共同决定。通过采用化学分级提取方法研究污泥组分的生物可及度,使用不同强度的提取溶液分离出4种化学可及度不同的提取组分,同时结合三维荧光光谱法对各组分中有机物质的复杂度进行分析。分析结果表明:组分的化学可及度与其生物可及度之间存在正相关关系;生物可及度较高,其成分有机物分子结构简单的组分SPOM(soluble particulate organic matter,SPOM)与REOM(readily extractible organic matter,REOM)在厌氧消化过程中降解率较高,分别为59.2%与46.3%的COD;而生物可及度低,组成复杂的组分SEOM(slowly extractible organic matter,SEOM)与PEOM(poorly extractible organic matter,PEOM)的生物降解率分别只有18.4%和5.8%的COD。 相似文献
69.
南京市城市污泥和工业污泥中典型矿质元素含量和形态分布研究 总被引:1,自引:0,他引:1
采用三态连续提取法研究南京市部分城市污泥和工业污泥中典型矿质元素的含量和形态分布,为污泥资源化的合理利用提供科学参考.结果表明,污泥总体呈高有机质、高氮磷、低K的相似性,但其理化性质如阳离子交换容量(CEC)、pH等有差异.污泥中不同矿质元素含量差异也较大,Fe的浓度最高,其次是Mg、Zn;且不同污泥间同一矿质元素含量的差异也较大.各元素的形态分布有一定差异,Cu主要分布在可氧化态,其酸溶/交换态和可还原态的百分率很低;Zn三态分布均较高;Mg、Mn主要分布在酸溶/交换态;Fe主要分布在残渣态.但三种提取形态百分率之和除Fe外均超过50%.研究同时表明,城市污泥和工业污泥中矿质元素形态分布无显著性差异. 相似文献
70.
ABSTRACT: An auto-regressive model has been developed for hydrologic data simulation. The model is computationally easier, parsimonious in number of model parameters and more stable in statistical characteristics than the existing auto-regressive model. The proposed model was used for synthesizing 10 sequences, each of 100 year length, of monthly flows for the river Beas. The statistical parameters were calculated using 49-year historical record for the river. The data was also synthesized using existing auot-regressive model. The synthesized sequences have been compared. The results indicate that the proposed model is as good as the existing auto-regressive model in preserving the mean and standard deviation of historical record. It is further shown that the proposed model requires less parameters than the auto-regressive model for simulation of long-term dependence. 相似文献