Naturally-assisted metal phytoextraction by Brassica carinata: Role ofroot exudates

Due to relatively high chelant dosages and potential environmental risks it is necessary to explore different approaches in the remediation of metal-contaminated soils. The present study focussed on the removal of metals (As, Cd, Cu, Pb and Zn) from a multiple metal-contaminated soil by growing Brassica carinata plants in succession to spontaneous metallicolous populations of Pinus pinaster, Plantago lanceolata and Silene paradoxa. The results showed that the growth of the metallicolous populations increased the extractable metal levels in the soil, which resulted in a higher accumulation of metals in the above-ground parts of B. carinata. Root exudates of the three metallicolous species were analysed to elucidate their possible role in the enhanced metal availability. The presence of metals stimulated the exudation of organic and phenolic acids as well as flavonoids. It was suggested that root exudates played an important role in solubilising metals in soil and in favouring their uptake by roots.     

Contamination from electrically conductive silicone tubing during aerosol chemical analysis

Electrically conductive silicone tubing is used to minimize losses in sampling lines during the analysis of airborne particle size distributions and number concentrations. We report contamination from this tubing using gas chromatography–mass spectrometry (GC–MS) of filter-collected samples as well as by particle mass spectrometry. Comparison of electrically conductive silicone and stainless steel tubing showed elevated siloxanes only for the silicone tubing. The extent of contamination increased with length of tubing to which the sample was exposed, and decreased with increasing relative humidity.     

Polycyclic aromatic hydrocarbon exhaust emissions from different reformulated diesel fuels and engine operating conditions

The study of light-duty diesel engine exhaust emissions is important due to their impact on atmospheric chemistry and air pollution. In this study, both the gas and the particulate phase of fuel exhaust were analyzed to investigate the effects of diesel reformulation and engine operating parameters. The research was focused on polycyclic aromatic hydrocarbon (PAH) compounds on particulate phase due to their high toxicity. These were analyzed using a gas chromatography–mass spectrometry (GC–MS) methodology.Although PAH profiles changed for diesel fuels with low-sulfur content and different percentages of aromatic hydrocarbons (5–25%), no significant differences for total PAH concentrations were detected. However, rape oil methyl ester biodiesel showed a greater number of PAH compounds, but in lower concentrations (close to 50%) than the reformulated diesel fuels. In addition, four engine operating conditions were evaluated, and the results showed that, during cold start, higher concentrations were observed for high molecular weight PAHs than during idling cycle and that the acceleration cycles provided higher concentrations than the steady-state conditions. Correlations between particulate PAHs and gas phase products were also observed.The emission of PAH compounds from the incomplete combustion of diesel fuel depended greatly on the source of the fuel and the driving patterns.     

Reactive transport modeling of remedial scenarios to predict cadmium,copper, and zinc in north fork of Clear Creek,Colorado

The North Fork of Clear Creek (NFCC), Colorado, is an acid‐mine‐drainage‐impacted stream typical of many mountain surface waters affected by historic metal mining in the western United States. The stream is devoid of fish primarily because of high metal concentrations in the water (e.g., copper and zinc) and has large amounts of settled iron oxyhydroxide solids that coat the streambed. The NFCC is part of the Central City/Clear Creek Superfund site, and remediation plans are being implemented that include treatment of three of the main point‐source inputs and cleanup of some tailings and waste rock piles. This article examines dissolved (0.45‐μm filterable) concentrations of cadmium, copper, and zinc following several potential remediation scenarios, simulated using a reactive transport model (WASP4/META4). Results from modeling indicate that for cadmium, remediation of the primary point‐source adit discharges should be sufficient to achieve acute and chronic water‐quality standards under both high‐ and low‐flow conditions. To achieve standards for copper and zinc, however, the modeling scenarios suggest that it may be necessary to treat or remove contaminated streambed sediments in downstream reaches, as well as identify and treat nonpoint sources of metals. Recommendations for improvements to the model for metal transport in acid‐mine drainage impacted streams are made. These recommendations are being implemented by the U.S. Environmental Protection Agency. © 2009 Wiley Periodicals, Inc.     

The content of butyl- and phenyltin derivatives in the sediment from the Port of Gdansk

Harbor sediments containing large deposits of organotin compounds constitute a potential threat to the marine environment. Samples of harbor sediments were collected twice in the years 2003 and 2005 from the following locations: Zió?kowskiego, Siarkowe, Wi?lane, Weglowe, Chemików and Paliw P?ynnych Quays. The cores of 25cm length sliced into 2- and 5-cm segments were analyzed. After drying and homogenization, samples were split into two granulometric fractions, i.e. <2.00 and <0.063mm. The dominant fraction in whole sediment, i.e. fraction grain diameter <2.00mm, was sand (grain diameter 2.00-0.063mm). However, the highest concentrations of butyltin (BT) and phenyltin (PT) compounds were found in the fine sediment fraction. The mean values of tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) in the analyzed samples in the <2.00mm fraction were 2144.9, 434.7 and 148.1ngSng(-1)d.w., respectively, while the corresponding mean values in the <0.063mm fraction were 6556.4, 1593.7 and 450.0ngSng(-1)d.w. The mean concentrations of monophenyltin (MPhT) have been estimated at 29.0 and 49.9ngSng(-1)d.w. for the <2.00 and <0.063mm fraction sizes, respectively. The estimated content levels of diphenyltin (DPhT) and triphenyltin (TPhT) were in most cases below the detection limit of the applied method. The sediment cores collected from the locations characterized by high industrialization and intense exploitation (Wi?lane, Weglowe Quays) contained the highest concentrations of BT and PT.     

Monitoring of the total content of polycyclic aromatic hydrocarbons (PAHs) in arable soils in Poland

The paper provides comprehensive information on the level of contamination of arable soils in Poland with polycyclic aromatic hydrocarbons (PAHs). Extensive monitoring studies were carried out to determine the content of the 16 priority PAHs in 216 soil samples collected in 2005 throughout arable lands (0-20 cm layer) in Poland. Locations of sampling points reflected the differences in regional industrialisation and urbanisation as well as in the characteristics of soils. The content of Sigma16PAHs ranged from 80 to 7264 microg kg(-1) with a median of 395 microg kg(-1) and with a dominance of 4-6 rings hydrocarbons (74% of total PAHs). Soil properties affected the PAHs content to a limited extend. The organic matter content was the only parameter correlated significantly (although weakly) with the concentrations of Sigma16PAHs; the strength of this relationship was more pronounced in soils with elevated OM content. The various molecular markers pointed to a prevailing pyrogenic origin of the PAHs in Polish arable soils, with minor contribution from liquid fuels combustion and traffic emissions. Two different Polish systems for classification of agricultural soils (providing for the content of Sigma9PAHs and Sigma13PAHs) indicate that the percentage of contaminated arable soils in Poland does not exceed 10%. Multivariate methods enabled an evaluation of spatial trends in Sigma16PAHs concentrations, an identification of regions with very low PAHs content (East part of the country), and a recognition of small industrial/urbanised areas of higher risk.     

Likelihood Ratio Analysis of Skin Cancer Prevalence Associated with Arsenic in Drinking Water in the USA

Several published studies have examined skin-cancer prevalence in regions of the USA that have concentrations of arsenic above the USA drinking-water standard. Those studies with adequate exposure and health outcome data did not report any skin cancer cases. Because the USA's arsenic concentrations are relatively low compared to some other countries and the study populations are small, the absence of reported skin-cancer cases could be due to an absence of risk in USA populations or random variability from a predicted risk. We used the current EPA arsenic cancer slope factor (CSF) model, which is derived from Taiwanese populations exposed to high levels of arsenic, to predict the expected number of skin cancers. We then conducted a likelihood ratio analysis, which showed that a null hypothesis (no additional skin cancer risk from arsenic) was approximately 2.2 times more likely than the hypothesis that ingested arsenic causes the predicted rate of skin cancers. Although based on small numbers, our analysis of USA populations indicates that the CSF derived from arsenic exposure in Taiwanese populations may be an overestimate when applied to USA populations.     

Quantification of biotransformation of chlorinated hydrocarbons in a biostimulation study: added value via stable carbon isotope analysis

Stable carbon isotope analysis of chlorinated aliphatic compounds was performed at an in situ biostimulation pilot test area (PTA) at a site where 1,2-dichloroethane (1,2-DCA) and trichloroethene (TCE) were present in groundwater. Chlorinated products of TCE reductive dechlorination (cis-dichloroethene (cDCE) and vinyl chloride (VC)) were present at concentrations of 17.5 to 126.4 micromol/L. Ethene, a potential degradation product of both 1,2-DCA dihaloelimination and TCE reductive dechlorination was also present in the PTA. Emulsified soybean oil and lactate were added as electron donors to stimulate anaerobic dechlorination in the PTA. Stable carbon isotope analysis provided evidence that dechlorination was occurring in the PTA during biostimulation, and a means of monitoring changes in dechlorination efficiency over the 183 day monitoring period. Stable carbon isotope analysis was also used to determine if ethene production in the PTA was due to dechlorination of TCE, 1,2-DCA, or both. Fractionation factors (alpha) were determined in the laboratory during anaerobic biotransformation of 1,2-DCA via a dihaloelimination reaction in four separate enrichment cultures. These alpha values (as well as the previously published ranges of alpha for the dechlorination of TCE, cDCE and 1,2-DCA) were used, along with isotopic values measured during the pilot test, to derive quantitative estimates of biotransformation during the pilot test. Dechlorination was found to account for 10.7 to 35.9%, 21.9 to 74.9%, and 54.4 to 67.8% of 1,2-DCA, TCE and cDCE concentration loss respectively in the PTA. Stable carbon isotope analysis indicates that dechlorination of 1,2-DCA, TCE and cDCE were all significant processes during the pilot test, while ethene production during the pilot test was dominated by 1,2-DCA dihaloelimination. This study demonstrates how stable carbon isotope analysis can provide more conservative estimates of the extent of biotransformation than do conventional protocols. In addition, in a complex mixed plume such as this, compound specific isotope analysis is shown to be one of the few methods available for clarifying dominant biotransformation pathways where breakdown products are non-exclusive (i.e. ethene).     

Dilution-based emissions sampling from stationary sources: Part 2--Gas-fired combustors compared with other fuel-fired systems

With the recent focus on fine particle matter (PM2.5), new, self-consistent data are needed to characterize emissions from combustion sources. Such data are necessary for health assessment and air quality modeling. To address this need, emissions data for gas-fired combustors are presented here, using dilution sampling as the reference. The dilution method allows for collection of emitted particles under conditions simulating cooling and dilution during entry from the stack into the air. The sampling and analysis of the collected particles in the presence of precursor gases, SO2 nitrogen oxide, volatile organic compound, and NH3 is discussed; the results include data from eight gas fired units, including a dual-fuel institutional boiler and a diesel engine powered electricity generator. These data are compared with results in the literature for heavy-duty diesel vehicles and stationary sources using coal or wood as fuels. The results show that the gas-fired combustors have very low PM2.5 mass emission rates in the range of approximately 10(-4) lb/million Btu (MMBTU) compared with the diesel backup generator with particle filter, with approximately 5 x 10(-3) lb/MMBTU. Even higher mass emission rates are found in coal-fired systems, with rates of approximately 0.07 lb/MMBTU for a bag-filter-controlled pilot unit burning eastern bituminous coal. The characterization of PM2.5 chemical composition from the gas-fired units indicates that much of the measured primary particle mass in PM2.5 samples is organic or elemental carbon and, to a much less extent, sulfate. Metal emissions are quite low compared with the diesel engines and the coal- or wood-fueled combustors. The metals found in the gas-fired combustor particles are low in concentration, similar in concentration to ambient particles. The interpretation of the particulate carbon emissions is complicated by the fact that an approximately equal amount of particulate carbon (mainly organic carbon) is found on the particle collector and a backup filter. It is likely that measurement artifacts, mostly adsorption of volatile organic compounds on quartz filters, are positively biasing "true" particulate carbon emission results.     

Responses of the flea beetles Phyllotreta nemorum and P. cruciferae to metabolically engineered Arabidopsis thaliana with an altered glucosinolate profile

Summary. Insects feeding on Cruciferae recognize their host plants at least partially by means of specific responses to glucosinolates. However, the effects of variations in glucosinolate levels on the acceptability of plants for specialized insects are not well understood. A survey of the literature demonstrated positive, no, as well as negative correlations between plant acceptability and glucosinolate levels. The present study took advantage of the presence of transgenic Arabidopsis thaliana plants with increased glucosinolate levels. Transgenic A. thaliana contain the CYP79A1 gene from Sorghum bicolor. This gene encodes an enzyme which converts L-tyrosine into p-hydroxyphenylacetaldoxime in the biosynthesis of cyanogenic glycosides in S. bicolor. In transgenic A. thaliana plants, endogenous enzymes convert p-hydroxyphenylacetaldoxime into p-hydroxybenzylglucosinolate (sinalbin), which is not found naturally in this plant. The introduction of CYP79A1 resulted in a four-fold increase in total glucosinolate levels in transgenic A. thaliana plants. Although these changes in glucosinolate levels were rather dramatic, they did not have any effects on the acceptability of A. thaliana for the two flea beetle species, Phyllotreta nemorum and P. cruciferae. The flea beetles did not discriminate between transgenic and wildtype plants. Furthermore, they did not discriminate between leaf discs of wildtype plants where different concentrations of p-hydroxybenzylglucosinolate had been applied topically on the leaf surface. Feeding in P. nemorum was stimulated by extremely high levels of allylglucosinolate while this compound had no effect on P. cruciferae. It is concluded that the effect of glucosinolates on adapted insects depends on the chemical or physical environment in which the glucosinolates are found.