Fate and distribution of arsenic in laboratory-scale subsurface horizontal-flow constructed wetlands treating an artificial wastewater

Knowledge regarding the fate, accumulation and distribution of arsenic inside constructed wetlands is still insufficient. Based on a complete mass balance analysis, the aim of this study was to investigate the fate and distribution of As in distinct wetland compartments and different segments along the wetland gradient. Experiments were carried out in laboratory-scale wetland systems, two planted with Juncus effusus and one unplanted, using an As-containing artificial wastewater. The obtained results revealed that the planted wetlands have a substantially higher As-mass retention capacity (59–61% of the total As inflow) than wetlands without plantation (only 44%). However, different loads of organic carbon within the inflowing artificial wastewater showed no remarkable influence on As-mass retention in the planted wetlands. Nearly 47–52% of the total inflowing As mass was found to be retained within the first half of the planted wetlands and this retention decreased step by step along the flow path. In contrast, only 28% of the total inflowing As mass was retained within the first half of the unplanted wetland. In general, a different fate and distribution of As was observed inside the planted and unplanted wetlands. Higher As concentrations were exhibited by the plant roots (51.5–161.5 mg As kg^?1 dry wt.) compared to the shoots (1.1–6.4 mg As kg^?1 dry wt.). Analysis of the total As-mass balance in the planted wetlands revealed that nearly 44–49% of the total inflowing As was recovered or concentrated within the plant roots, only 1% was sequestered within the plant shoots, 7–10% were entrapped or deposited within the gravel bed sediments, 2–3% were retained in the standing pore water, 39–41% were flushed out as outflow and the remaining 1–2% is still considered to be unaccountable. Total As accumulation in the plant shoots made a small contribution to the mass balance, and plant root biomass was found to be the most important compartment for As retention. In contrast, nearly 11% of the total inflowing As were found in the sediment, 2% in the standing pore water, 57% in the outflow and a substantially higher portion (nearly 30%) remained unaccountable in the unplanted bed, which might be released as volatile As compounds or lost from the system due to various unknown reasons. The results indicate that plants have a remarkable effect on As retention and stability of already retained As; hence planted wetlands might be a suitable option for treating As-contaminated wastewater.     

Proteomics in radiation research: present status and future perspectives

Rapidly developing postgenome research has made proteins an attractive target for biological analysis. The well-established term of proteome is defined as the complete set of proteins expressed in a given cell, tissue or organism. Unlike the genome, a proteome is rapidly changing as it tends to adapt to microenvironmental signals. The systematic analysis of the proteome at a given time and state is referred to as proteomics. This technique provides information on the molecular and cellular mechanisms that regulate physiology and pathophysiology of the cell. Applications of proteome profiling in radiation research are increasing. However, the large-scale proteomics data sets generated need to be integrated into other fields of radiation biology to facilitate the interpretation of radiation-induced cellular and tissue effects. The aim of this review is to introduce the most recent developments in the field of radiation proteomics.     

Fate of viruses in artificial wetlands

Little is known about the ability of wetlands to remove disease-causing viruses from municipal wastewater. In this study we examined the survival of several indicators of viral pollution (indigenous F-specific bacteriophages, seeded MS2 bacteriophage, and seeded human poliovirus type 1) applied in primary municipal wastewater to artificial wetland ecosystems. Only about 1% of the indigenous F-specific RNA bacteriophages survived flow through the vegetated wetland beds at a 5-cm-day-1 hydraulic application rate during the period from June through December 1985. The total number of indigenous F-specific bacteriophages (F-specific RNA and F-specific DNA phages) was also reduced by about 99% by wetland treatment, with the mean inflow concentration over the period of an entire year reduced from 3,129 to 33 PFU ml-1 in the outflow of a vegetated bed and to 174 PFU ml-1 in the outflow of an unvegetated bed. Such superior treatment by the vegetated bed demonstrates the significant role of higher aquatic plants in the removal process. Seeded MS2 bacteriophage and seeded poliovirus were removed more efficiently than were the indigenous bacteriophages, with less than 0.2% of MS2 and 0.1% of the poliovirus surviving flow at the same hydraulic application rate. The decay rate (k) of MS2 in a stagnant wetlands (k = 0.012 to 0.028 h-1) was lower than that for flowing systems (k = 0.44 to 0.052 h-1), reflecting the enhanced capacity for filtration or adsorption of viruses by the root-substrate complex (and associated biofilm).(ABSTRACT TRUNCATED AT 250 WORDS)     

Metabolomics in pesticide research and development: review and future perspectives

The emerge of metabolomics within functional genomics has provided a new dimension in the study of biological systems. In regards to the study of agroecosystems, metabolomics enables monitoring of metabolic changes in association with biotic or abiotic agents such as agrochemicals. Focusing on crop protection chemicals, a great effort has been given towards the development of crop protection agents safer for consumers and the environment and more efficient than the existing ones. Within this framework, metabolomics has so far been a valuable tool for high-throughput screening of bioactive substances in order to discover those with high selectivity, unique modes-of-action, and acceptable eco-toxicological/toxicological profiles. Here, applications of metabolomics in the investigation of the modes-of-action and ecotoxicological–toxicological risk assessment of bioactive compounds, mining of biological systems for the discovery of bioactive metabolites, and the risk assessment of genetic modified crops are discussed.     

Chromium removal in constructed wetlands: A review

The distribution, mobility and availability of metals in the environment depend not only on their total concentration but also on their formations and bounds with the soil. Hexavalent chromium is a very toxic, metal compound, frequently found in polluted industrial wastewaters, and causes serious environmental problems. The potential application of constructed wetlands in the treatment of chromium bearing wastewaters has been reported recently. This paper reviews research on constructed wetlands treating chromium polluted wastewaters, and focuses on several design and operational parameters. The review highlights the effect of vegetation type, hydraulic residence time and porous media type on wetland performance. Constructed wetlands have been proved to be rather efficient at treating chromium containing wastewaters.     

Clogging in horizontal subsurface flow constructed wetlands: influencing factors,research methods and remediation techniques

The treatment of wastewater in constructed wetlands (CW) has been increasingly applied throughout the world, as it is an efficient technique for the removal of pollutants and presents low construction and operational costs. However, a major operational problem of these systems is clogging of the porous medium. Clogging of CW has therefore attracted the attention in several studies, but there are several gaps in the understanding of this phenomenon, especially with regards to its genesis. In order to evaluate the contribution of the influencing factors and to facilitate remediation, it is important to have methods that favor characterization of the real conditions of CW. In this review, the objective was to gather information on the main factors interfering in the clogging process of horizontal subsurface flow constructed wetlands, the available and the new methods for characterizing the degree of obstruction of the porous medium and the techniques/strategies for unclogging these systems.     

鸟类学研究:过去二十年的回顾和对中国未来发展的建议

为了解中国鸟类学研究的状况和发展趋势,我们利用在线文献数据库(Web of Science)检索了1991-2010年间发表的与鸟类有关的文献,对中国和其他国家的鸟类学研究论文、研究领域、研究机构等进行了分析和比较。结果发现,中国鸟类学研究发展很快,专业研究人员数量在1991-2010年间增长了近四倍,在国际上发表的研究论文的数量近几年年均增长25%;论文数量占世界的比例已经由1991-2000年的0.46%上升到了2001-2010年期间的1.53%,世界排名由第27位上升至第16位,并且研究领域更加多元化,论文水平不断提高。在鸟类系统发育与演化、合作繁殖和婚配、禽流感、巢寄生等领域的许多成果开始在国际相关领域的高水平刊物上发表,在古鸟类以及雉类和鹤类等濒危鸟类的保护研究方面位居世界前列。但从整体而言,中国鸟类学研究与世界上一些发达国家相比还有很大差距。为此我们对中国鸟类学未来的发展提出了一些建议,包括需要更加关注鸟类的生活史对策、气候变化和城市化对鸟类的影响、鸟类迁徙、濒危物种保护生物学等领域的研究,进一步加强国际交流与合作,规范鸟类研究及数据保存和处理的方法,采取更有效措施加大对青年研究人员的支持力度等。     

Narcolepsy research: past, present, and future perspectives

In 1877, Westphal described a patient with hypersomnia and episodic muscle weakness. He did not feel that these weakness attacks could simply be explained by "epileptoid" phenomenon. The next year, Fischer described a similar case. By 1880, Gélineau decided that patients with these symptoms represented a distinct clinical entity and he called it "narcolepsy". In 1902, Loewenfeld noted the importance of cataplexy in this disorder, and in 1934 Daniels published an important review on the topic which helped to galvanize interest in further study. In 1957, Yoss and Daly discussed the "clinical tetrad" which included hypersomnia, cataplexy, hypnagogic hallucinations, and sleep paralysis. In 1960, Vogel noted that patients with narcolepsy had early onset of REM sleep on their electroencephalograms. At the First International Symposium on Narcolepsy in 1975, the symptom of disturbed nocturnal sleep was added to the clinical diagnostic criteria for narcolepsy. For many years the etiology and mechanisms of this disease were poorly understood. It was not until the early 1970s when the exciting animal and human research first started to unravel the mysteries of the genetics and physiology of narcolepsy. This research will be discussed below.     

Fate of viruses in artificial wetlands.

Little is known about the ability of wetlands to remove disease-causing viruses from municipal wastewater. In this study we examined the survival of several indicators of viral pollution (indigenous F-specific bacteriophages, seeded MS2 bacteriophage, and seeded human poliovirus type 1) applied in primary municipal wastewater to artificial wetland ecosystems. Only about 1% of the indigenous F-specific RNA bacteriophages survived flow through the vegetated wetland beds at a 5-cm-day-1 hydraulic application rate during the period from June through December 1985. The total number of indigenous F-specific bacteriophages (F-specific RNA and F-specific DNA phages) was also reduced by about 99% by wetland treatment, with the mean inflow concentration over the period of an entire year reduced from 3,129 to 33 PFU ml-1 in the outflow of a vegetated bed and to 174 PFU ml-1 in the outflow of an unvegetated bed. Such superior treatment by the vegetated bed demonstrates the significant role of higher aquatic plants in the removal process. Seeded MS2 bacteriophage and seeded poliovirus were removed more efficiently than were the indigenous bacteriophages, with less than 0.2% of MS2 and 0.1% of the poliovirus surviving flow at the same hydraulic application rate. The decay rate (k) of MS2 in a stagnant wetlands (k = 0.012 to 0.028 h-1) was lower than that for flowing systems (k = 0.44 to 0.052 h-1), reflecting the enhanced capacity for filtration or adsorption of viruses by the root-substrate complex (and associated biofilm).(ABSTRACT TRUNCATED AT 250 WORDS)     

Assessing hydrogeochemical heterogeneity in natural and constructed wetlands

While water quality function is cited as animportant wetland function to design for and preserve,we demonstrate that the scale at which hydrochemicalsamples are collected can significantly influenceinterpretations of biogeochemical processes inwetlands. Subsurface, chemical profiles for bothnutrients and major ions were determined at a site insouthwestern Wisconsin that contained areas of bothnatural and constructed wetlands. Sampling wasconducted on three different scales: (1) a large scale(3 m between sampling points), (2) an intermediatescale (0.15 m between sampling points), and (3) a smallscale (1.5 cm between sampling points). In mostcases, significant vertical heterogeneity was observedat the 0.15 m scale, which was much larger thanpreviously reported for freshwater wetlands and notdetected by sampling water table wells screened overthe same interval. However, profiles of ammonia andtotal phosphorus showed tenfold changes in the upper0.2 meters of the saturated zone when sampled at thesmall (1.5 cm) scale, that was not depicted bysampling at the intermediate scale. At theintermediate scale of observation, one constructedwetland site differed geochemically from the naturalwetlands and the other constructed wetland site due toapplication of off-site salvaged marsh surface anddownward infiltration of rain. While importantdifferences in dissolved inorganic phosphorus anddissolved inorganic carbon concentrations existedbetween the constructed wetland and the naturalwetlands, we also observed substantial differencesbetween the natural wetland sites for theseconstituents. A median-polishing analysis of our datashowed that temporal variations in constituentconcentrations within profiles, although extensivelyrecognized in the literature, were not as important asspatial variability.     

Building consensus in neuromesodermal research: Current advances and future biomedical perspectives

The development of the vertebrate body axis relies on the activity of different populations of axial progenitors, including neuromesodermal progenitors. Currently, the term ‘Neuromesodermal progenitors’ is associated with various definitions. Here, we use distinct terminologies to highlight advances in our understanding of this cell type at both the single-cell and population levels. We discuss how these recent insights prompt new opportunities to address a range of biomedical questions spanning cancer metastasis, congenital disorders, cellular metabolism, regenerative medicine, and evolution. Finally, we outline some of the major unanswered questions and propose future directions at the forefront of neuromesodermal research.     

Fate of heavy metals in vertical subsurface flow constructed wetlands treating secondary treated petroleum refinery wastewater in Kaduna,Nigeria

This study examined the performance of pilot-scale vertical subsurface flow constructed wetlands (VSF–CWs) planted with three indigenous plants, i.e. Typha latifolia, Cyperus alternifolius, and Cynodon dactylon, in removing heavy metals from secondary treated refinery wastewater under tropical conditions. The T. latifolia-planted VSF–CW had the best heavy metal removal performance, followed by the Cyperus alternifolius-planted VSF–CW and then the Cynodon dactylon-planted VSF–CW. The data indicated that Cu, Cr, Zn, Pb, Cd, and Fe were accumulated in the plants at all the three VSF–CWs. However, the accumulation of the heavy metals in the plants accounted for only a rather small fraction (0.09–16%) of the overall heavy metal removal by the wetlands. The plant roots accumulated the highest amount of heavy metals, followed by the leaves, and then the stem. Cr and Fe were mainly retained in the roots of T. latifolia, Cyperus alternifolius, and Cynodon dactylon (TF < 1), meaning that Cr and Fe were only partially transported to the leaves of these plants. This study showed that VSF–CWs planted with T. latifolia, Cyperus Alternifolius, and Cynodon dactylon can be used for the large-scale removal of heavy metals from secondary refinery wastewater.     

人工湿地污水处理的应用现状及前景展望

本文分析了人工湿地系统在污水处理中的作用,叙述了人工湿地在发展中国家的应用现状及所取得的效果。人工湿地的特点适合我国国情,特别适合广大农村、中小城市的污水处理,在我国具有极其广阔的应用前景。对湿地用于污水处理方面的不足,如缺乏污水对植物影响的研究(特别是对乡土植物的研究)、缺乏对重要工艺的理解、人工湿地占地面积大等也进行了分析。     

Spatial distribution of metals in the constructed wetlands

Investigation of the spatial distribution of metals was conducted for two constructed wetlands used as tertiary treatment in Chia Nan University of Pharmacy and Science (CNU) and Metal Processing Industries (MPI) located in Tainan, Taiwan. These two distinguished sites were selected to compare the distribution of metals for constructed wetlands treating different types of wastewater. Along the distance, samples of water, sediment, and macrophytes were analyzed for metals including Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn. Additionally, measurements of water quality including temperature, pH, EC, ORP, DO, TSS, BOD, COD, and turbidity were performed. Results show that, at CNU, wastewater contained higher organic consititute (BOD 29.3 +/- 11.7 mg/, COD 46.7 +/- 33.6 mg/L) with low metals content. Wastewater at MPI contained low level of organic consititute (BOD 7.1 +/- 3.3 mg/L, and COD 66.0 +/- 56.5 mg/L) and higher metals content. Metals distribution of both sites showed similar results where metals in the sediments in the inlet zone have greater concentrations than other areas. The constructed wetlands can remove Cd, Cu, Ni, Pb, and Zn. However, there was no removal of Al, Cr, Fe, and Mn. A distance along the constructed wetlands had no effect on metal concentrations in macrophyte and water.     

人工湿地研究进展及应用

基于生态学原理的人工湿地污水处理技术已成为人们竞相研究开发的热点。介绍了人工湿地的分类,论述了污染物包括有机物、氮磷污染物、重金属的去除机理的研究进展,分析了湿地植物种类与根系量对污染物去除效果的影响,讨论了湿地结构以及工艺设计的研究情况。最后以人工湿地处理生活用水和工业用水为例综述了人工湿地目前在国内应用的状况。通过以上分析评述发现,人工湿地运行费用低,操作简单,是一种具有前景的污水处理技术,但在污染物去除机理和实践应用方面还需做更深入的研究。     

Development of natural conditions in constructed wetlands: Biological and chemical changes

The main objectives of this study were to determine the biogeochemical changes taking place in wetlands constructed on coal mine spoil, and to determine the rate at which these constructed wetlands would develop the ecological characteristics of natural wetlands. In 1992 a multicell wetland was constructed. The cells were lined with two coal mine spoil types and one topsoil. In 1993, the cells were planted with cattail (Typha latifolia), maidencane (Panicum hemitomon), pickerelweed (Pontederia lanceolota), and soft stem bulrush (Scirpus validus). Pickerelweed spread most rapidly followed by maidencane and bulrush. Cattail did not establish uniformly but spread in an irregular manner. There was no difference in plant establishment between the topsoil or the two mine spoils. The pH of the most acidic spoil increased by more than one unit after flooding. Organic matter content fluctuated in all three substrates from year to year. The concentration of the nutrient and metal elements increased after flooding. Extractable Al, Fe, and Mn increased more than other elements. The data presented here indicate that, except for organic matter accumulation, these constructed wetlands have taken on the botanical and biogeochemical characteristics of natural wetlands within 3–4 years.     

Impacts of engineered nanomaterials on microbial community structure and function in natural and engineered ecosystems

In natural and engineered environments, microorganisms often exist as complex communities, which are key to the health of ecosystems and the success of bioprocesses in various engineering applications. With the rapid development of nanotechnology in recent years, engineered nanomaterials (ENMs) have been considered one type of emerging contaminants that pose great potential risks to the proper function of microbial communities in natural and engineered ecosystems. The impacts of ENMs on microorganisms have attracted increasing research attentions; however, most studies focused on the antimicrobial activities of ENMs at single cell and population level. Elucidating the influence of ENMs on microbial communities represents a critical step toward a comprehensive understanding of the ecotoxicity of ENMs. In this mini-review, we summarize and discuss recent research work on the impacts of ENMs on microbial communities in natural and engineered ecosystems, with an emphasis on their influences on the community structure and function. We also highlight several important research topics which may be of great interest to the research community.     

Bioflocculation in natural and engineered systems: current perspectives

Microorganisms have the tendency to accumulate at interfaces through the release of extracellular polymeric substances to form aggregates such as films or flocs. This physical association leads to different modes of interactions among cells and the subsequent development of functionally and metabolically diverse consortia. Aggregation of cells in aqueous suspensions often results in the formation of flocs, which are hotspots of enhanced microbial processes. This has important implications for the dynamics of organic and inorganic matter in varied ecosystems. These microbial flocs are not only important components in nutrient turnover, decomposition, and sinking flux but also facilitate contaminant removal and treatment of wastewater and biomass harvesting. Greater insight into the multitude of interactions between microorganisms in flocs would be useful to enhance the efficiency of bioflocculation processes. This review covers the fundamental aspects and outlines the role of bioflocculation in controlled industrial processes and in nature.