The Role of a Salt Marsh Plant on Trace Metal Bioavailability in Sediments. Estimation By Different Chemical Approaches * (7 pp)

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.     

Persistence of methyl <Emphasis Type="Italic">tertiary</Emphasis> butyl ether (MTBE) against metabolism by Danish vegetation

BACKGROUND: Methyl tertiary butyl ether (MTBE) is the second most highly produced industrial chemical in the US and a frequent groundwater pollutant. At the same time, MTBE is quite persistent to biotic and abiotic decomposition. The goal of this study was to find plant species that could degrade MTBE and might be used in phytoremediation. METHODS: Excised roots and leaves (0.3 g) from more than 24 Danish plant species out of 15 families were kept in glass vessels with 25 ml spiked aqueous solution for 2 to 4 days. MTBE concentrations were 1 to 5 mg/L. Samples were taken directly from the solution with a needle and injected to a purge and trap unit. MTBE and the main metabolite, TBA, were measured by GC/FID. RESULTS AND DISCUSSION: Solutions with roots of poplar (Populus robusta) and a willow hybrid (Salix viminalis x schwerinii) produced TBA in trace amounts, probably stemming from bacteria. Significant MTBE reduction (> 10%) was not observed in any of the tests. Leaves from none of the species (trees, grasses and herbs) reduced the concentration of MTBE in the solution and no TBA, nor any other known metabolite of MTBE, was detected. CONCLUSION: It was not possible to find plants capable of efficiently degrading MTBE. This gives rise to the conclusion that plants probably cannot degrade MTBE at all, or only very slowly. RECOMMENDATIONS AND OUTLOOK: For phytoremediation projects, this has, as consequence, that the volatilization by plants (except with genetically engineered plants) is the only relevant removal process for MTBE. For risk assessment of MTBE, degradation by the plant empire is not a relevant sink process.     

处理生活污水的植物品种的筛选

以小型碎石床人工湿地生态系统和无土栽培2种方法,模拟研究了广东园林绿化中常用的27种植物对生活污水中氮、磷、COD的降解能力,表明野芋头、花叶万年青、象草、姜花、绿公主、富贵竹、再力花、大花叶万年青、芦苇、花芦苇、美人蕉、文殊兰、水芋头、风车草、红草、蜘蛛兰、千手观音、水葱和花蝴蝶等18种植物,可以作为人工湿地生态系统选种植物,从而扩大了可选植物品种范围,配合适当,可达到美化环境和净化污水2种功能,可适用于面源性水污染的治理.象草的研究表明,它是一种既有强污水降解能力又能作饲料的品种,适用于畜牧场的水污染治理.     

丝瓜对食品废水的净化功能及经济效益

本文研究了丝瓜（Ｌｕｆｆａｃｙｌｉｎｄｒｉｃａ）在水面上的水培技术，对食品工业废水（啤酒废水）的净化功能及其经济效益。其试验结果表明：采用水培技术将丝瓜栽种在水面上是完全成功的。该法已经被应用到无锡市酿酒总厂食品工业废水净化处理。在５月份，丝瓜对啤酒废水中污染物ＴＮ的净化率为７８．６％，ＴＰ７８．０％，ＮＨ＋＿４－Ｎ９９．６％，ＣＯＤ２２．５％，浊度８０．９％。在６月份，丝瓜的净化率为ＴＮ８９．１％，ＴＰ９０．４％，ＮＨ＋＿４－Ｎ９９．２％，ＣＯＤ４４．１％和浊度８６．４％。由此可见，丝瓜是一种对食品废水净化的优良植物，其经济效益也很显著，每亩水面丝瓜（果实）可达２０００ｋｇ～２５００ｋｇ，经济价值达２０００元～２５００元。     

Lead Contamination of Topsoil and Vegetation in the Vicinity of a Battery Factory in Nigeria

Levels of Pb, Zn, Cu, Cr, Ni and Cd were determined in topsoil and vegetation in the vicinity of a factory manufacturing lead- batteries in Ibadan, Nigeria. The samples were collected along five transects in different directions, and varying distances up to 1000m from the factory. Soil lead levels were found to be elevated around the factory, with average levels of about 2000mgkg^–1 close to the fence that declined gradually to about 50mgkg^–1 some 750m away. Soil-lead level around a primary school located about 500m from the factory was as high as 1450mgkg^–1. Lead levels were equally elevated in the vegetation, though average levels in vegetation were slightly lower than in the soil. Cadmium concentrations in soil and vegetation, though low, were more positively correlated with lead levels than any of the other metals are with lead.     

Relationship between Population Size and Fitness

Abstract:  Long-term effective population size, which determines rates of inbreeding, is correlated with population fitness. Fitness, in turn, influences population persistence. I synthesized data from the literature concerning the effects of population size on population fitness in natural populations of plants to determine how large populations must be to maintain levels of fitness that will provide adequate protection against environmental perturbations that can cause extinction. Integral to this comment on what has been done and what needs to be done, sThe evidence suggests that there is a linear relationship between log population size and population fitness over the range of population sizes examined. More importantly, populations will have to be maintained at sizes of >2000 individuals to maintain population fitness at levels compatible with the conservation goal of long-term persistence. This approach to estimating minimum viable population size provides estimates that are in general agreement with those from numerous other studies and strengthens the argument that conservation efforts should ultimately aim at maintaining populations of several thousand individuals to ensure long-term persistence.     

我国利用水生植物监测和净化污水的研究进展

本文综述了我国利用水生植物监测和净化重金属废水、化工废水、生活污水、放射性核素废水以及抑制富营养化水体中藻类研究进展。并讨论了各种生态因子对水生植物净化效率的影响。为建立低投资、高效率、易管理的植物净化处理设施提供参考。     

Emission control strategies of hazardous trace elements from coal-fired power plants in China

China's energy dependents on coal due to the abundance and low cost of coal. Coal provides a secure and stable energy source in China. Over-dependence on coal results in the emission of Hazardous Trace Elements (HTEs) including selenium (Se), mercury (Hg), lead (Pb), arsenic (As), etc., from Coal-Fired Power Plants (CFPPs), which are the major toxic air pollutants causing widespread concern. For this reason, it is essential to provide a succinct analysis of the main HTEs emission control techniques while concurrently identifying the research prospects framework and specifying future research directions. The study herein reviews various techniques applied in China for the selected HTEs emission control, including the technical, institutional, policy, and regulatory aspects. The specific areas covered in this study include health effects, future coal production and consumption, the current situation of HTEs in Chinese coal, the chemistry of selected HTEs, control techniques, policies, and action plans safeguarding the emission control. The review emphasizes the fact that China must establish and promote efficient and clean ways to utilize coal in order to realize sustainable development. The principal conclusion is that cleaning coal technologies and fuel substitution should be great potential HTEs control technologies in China. Future research should focus on the simultaneous removal of HTEs, PM, SOx, and NOx in the complex flue gas.     

太湖流域湖荡湿地水生植物的分布特征

2018年在太湖流域内的87个湖荡湿地调查中共发现64种水生植物,隶属于33科51属.总体来看,太湖流域水生植物种类、数量以及覆盖面积与历史上比较呈下降趋势.根据流域上不同地理区域分区（东、西、南、北4个）,分析太湖流域水生植物的分类和功能多样性,发现太湖流域四个区域的分类α多样性指数分别为4.33、5.58、5.01和3.46, β多样性指数分别为3.46、4.23、1.63和7.02,且北部和西部、北部和南部、东部和西部、东部和南部、西部和南部湖荡湿地的分类α多样性均有显著差异,同时太湖流域北部和东部、北部和西部、北部和南部、西部和南部湖荡湿地间的分类β多样性有显著差异.功能多样性方面,四个区域的β多样性指数分别为0.18、0.14、0.09、0.30,太湖流域各分区部分之间水生植物的功能β多样性均有显著差异.CCA结果表明环境变量对太湖流域湖荡水生植物组成的解释度为21.21%,水体总氮和总磷贡献最大,水体富营养化可能是影响太湖流域水生植物衰退的一个重要原因.