Phytoaccumulation of heavy metals by aquatic plants

Three aquatic plants were examined for their ability to remove heavy metals from contaminated water: parrot feather (Myriophylhum aquaticum), creeping primrose (Ludwigina palustris), and water mint (Mentha aquatic). The plants were obtained from a Solar Aquatic System treating municipal wastewater. All the three plants were able to remove Fe, Zn, Cu, and Hg from the contaminated water. The average removal efficiency for the three plant species was 99.8%, 76.7%, 41.62%, and 33.9% of Hg, Fe, Cu, and Zn, respectively. The removal rates of zinc and copper were constant (0.48 mg/l/day for Zn and 0.11 mg/l/day for Cu), whereas those of iron and mercury were dependent on the concentration of these elements in the contaminated water and ranged from 7.00 to 0.41 mg/l/day for Fe and 0.0787 to 0.0002 mg/l/day for Hg. Parrot feather showed greater tolerance to toxicity followed by water mint and creeping primrose. The growth of creeping primrose was significantly affected by heavy metal toxicity. The selectivity of heavy metals for the three plant species was the same (Hg>Fe>Cu>Zn). The mass balance preformed on the system showed that about 60.45-82.61% of the zinc and 38.96-60.75% of the copper were removed by precipitation as zinc phosphate and copper phosphate, respectively.     

Greenhouse gases fluxes and soil thermal properties in a pasture in central Missouri

Fluctuations of greenhouse gases emissions and soil properties occur at short spatial and temporal scales, however, results are often reported for larger scales studies. We monitored CO2, CH4, and N2O fluxes and soil temperature (T), thermal conductivity (K), resistivity (R) and thermal di usivity (D) from 2004 to 2006 in a pasture. Soil air samples for determination of CO2, CH4 and N2O concentrations were collected from static and vented chambers and analyzed within two hours of collection with a gas chromatograph. T, K, R and D were measured in-situ using a KD2 probe. Soil samples were also taken for measurements of soil chemical and physical properties. The pasture acted as a sink in 2004, a source in 2005 and again a sink of CH4 in 2006. CO2 and CH4 were highest, but N2O as well as T, K and D were lowest in 2004. Only K was correlated with CO2 in 2004 while T correlated with both N2O (r = 0.76, p = 0.0001) and CO2 (r = 0.88, p = 0.0001) in 2005. In 2006, all gases fluxes were significantly correlated with T, K and R when the data for the entire year were considered. However, an in-depth examination of the data revealed the existence of month-to-month shifts, lack of correlation and di ering spatial structures. These results stress the need for further studies on the relationship between soil properties and gases fluxes. K and R o er a promise as potential controlling factors for greenhouse gases fluxes in this pasture.     

Evaluation of the effectiveness of horizontal subsurface flow constructed wetlands for different media

Two media bed (gravel and Filtralite NR) were tested in a mesocosm to evaluate the removal of organic matter (as chemical oxygen demand (COD)),ammonia (NH4-N),nitrite,nitrate and solid matter (as total suspended solids (TSS)) for a synthetic wastewater (acetate-based) and a domestic wastewater.The use of Filtralite allowed average removal rates (6–16.8 g COD/(m2·day),0.8–1.1 g NH4-N/(m2·day) and 3.1 g TSS/(m2·day)) and removal effciencies (65%–93%,57%–85% and 78% for COD,NH4-N and TSS,respectively),higher than that observed in the experiments with gravel.The applied loads of COD,ammonia,nitrate and TSS seem to influence the respective removal rates but only for the treatment of domestic wastewater with higher correlation coefficients for Filtralite.Regardless the type of media bed and the type of wastewater,nitrate was completely removed for nitrogen loading rates up to 1.3 g NO3-N/(m2·day).There was no evidence of the influence of nitrate loads on the removal of organic matter.     

Development of a loading dock safety evaluation tool

INTRODUCTION: Companies that use forklifts to load and unload trucks at loading docks are well aware of the main danger associated with this type of activity (i.e., the possibility of the forklift falling or tipping over when the truck suddenly moves away from the dock). Even if various truck restraint measures can be implemented to reduce the possibility of this type of accident, a number of hazardous incidents that result in a forklift tipping over from a loading dock still do occur regularly in day-to-day activities. This situation has brought experts to examine and evaluate the effectiveness of different measures and systems depending on the context in which they are used. METHODS: The present study touched upon both the technical and the organizational aspects of the restraint measures that could have an impact on safety. Certain elements were examined very closely, especially the failure of mechanical devices and their relation to the environment in which they are used, as well as the systemic interaction between people and the various restraint measures in use in a given context. CONCLUSION: This article presents a safety evaluation tool regarding restraint measures or systems for trucks docked at loading platforms - a tool that, of course, would take into consideration both the specific contextual aspects related to the docking bay itself, and to the plant. IMPACT ON INDUSTRY: This tool is designed to help companies choose the optimal safety measures to implement, while remaining realistic in terms of the technical and economic aspects of any given situation.     

Safety culture: analysis of the causal relationships between its key dimensions

INTRODUCTION: Several fields are showing increasing interest in safety culture as a means of reducing accidents in the workplace. The literature shows that safety culture is a multidimensional concept. However, considerable confusion surrounds this concept, about which little consensus has been reached. METHOD: This study proposes a model for a positive safety culture and tests this on a sample of 455 Spanish companies, using the structural equation modeling statistical technique. RESULTS: Results show the important role of managers in the promotion of employees' safe behavior, both directly, through their attitudes and behaviors, and indirectly, by developing a safety management system. IMPACT ON INDUSTRY: This paper identifies the key dimensions of safety culture. In addition, a measurement scale for the safety management system is validated. This will assist organizations in defining areas where they need to progress if they wish to improve their safety. Also, we stress that managers need to be wholly committed to and personally involved in safety activities, thereby conveying the importance the firm attaches to these issues.     

Concentrations of PCDD/PCDFs and PCBs in fish and seafood from the Catalan (Spain) market: estimated human intake

The concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs) in samples from 14 fish and seafood species widely consumed by the population of Catalonia, Spain, were measured. These samples were randomly purchased independently of their geographical origin. The intake of PCDD/Fs and PCBs through consumption of these species was also estimated for various age and sex groups of this population. The highest and lowest levels of PCDD/Fs and dioxin-like PCBs (DL-PCBs) were found in red mullet and shrimp, respectively. For a standard adult man (70 kg body weight), the intake of PCDD/Fs plus DL-PCBs through consumption of fish and other seafood was estimated to be 38.0 pg WHO-TEQ/day. Tuna, hake, and sardine were the species with the highest contribution to this intake. The results of this study indicate that, in general terms, the dietary habits of the population of Catalonia (Spain) regarding fish and seafood consumption do not contribute remarkably to increase PCDD/F and DL-PCB intake.     

Methylmercury genotoxicity: a novel effect in human cell lines of the central nervous system

Methylmercury is an important source of environmental contamination and the central nervous system (CNS) is one of the main target organs. Methylmercury genotoxicity was already demonstrated in peripherical tissues but was never detected in the brain. Thus, the objective of this work was to verify its genotoxic effect using brain cell lines. Glioblastoma (U373) and neuroblastoma (B103) human cell lines were exposed to methylmercury (0-10 microM). By measuring cellular viability, concentrations inducing <20% of cellular death (P<0.05) were selected: 1 and 0.1 microM. To detect micronuclei, 200,000 cells were treated with methylmercury for 24 h, and then incubated with cytochalasin B (2 microg/ml) for 72 h (U373) or 48 h (B103). The binucleation index, frequency of micronucleated cells, micronucleation index, metaphasic index and index of nucleoplasmic bridges were determined. Statistical analysis showed indices and percentages significantly higher (P<0.05) in methylmercury-treated cells. Each cell line was shown to be differently sensitive to each biomarker of genotoxic damage, which seems to indicate the existence of different mechanisms of toxicity. This work demonstrates, for the first time, MeHg ability to provoke genotoxicity in cells of brain origin with relatively low levels of exposure.     

Omega-3 fatty acids and the benefits of fish consumption: is all that glitters gold?

In recent years, a number of studies have clearly remarked the nutritional benefits of fish consumption: proteins, vitamins, minerals, and especially omega-3 polyunsaturated fatty acids (PUFAs), which may protect against several adverse health effects, including coronary heart disease mortality and stroke. However, some concerns about potential health risks derived from the environmental contaminants found in fish have been also raised. Therefore, balancing adequately the risks and benefits of fish consumption is currently a nutritional/environmental health key issue. In this paper, the most recent available scientific information concerning this issue is reviewed. It is concluded that although it seems evident that fish must be an important part of a balanced diet, to choose the most suitable species in terms of levels of PUFAs and pollutants, the frequency of consumption, and the meal size are essential aspects to balance benefits and risks of a regular consumption.