Estimation of K(OA) values of 209 polychlorinated trans-azobenzenes by PM6 and DFT methods

The octanol-air partition coefficients (K(OA)) of all 209 PCt-ABs were determined computationally to fill gaps on their environmentally relevant physical and chemical properties. These properties have been determined using two computational approaches: the semi-empirical quantum chemistry method for property parameterization (PM6) of the molecular orbital package (MOPAC) and density functional theory (DFT) method using B3LYP functional and 6-311++G** basis set in Gaussian 03 software and artificial neural network (ANN) predicting abilities. Both computational methods enabled estimation of log K(OA) partition coefficients of PCt-ABs with a similar accuracy and precision. The PM6 method compared to DFT was highly superior because it requires much less time, manpower and cost of hardware. The determined log K(OA) values of the investigated PCt-ABs for standard condition (25 °C) varied between 8.30 and 8.75 for Mono-; 8.71 and 9.92 for Di-; 9.58 and 10.72 for Tri-; 10.11 and 11.34 for Tetra-, 10.83 and 11.85 for Penta-; 11.24 and 12.36 for Hexa-; 11.87 and 12.66 for Hepta-; 12.31 and 12.97 for Octa-; 12.89 and 13.21 for Nona-Ct-ABs; and 13.17- and 13.49 for Deca-Ct-AB. PCt-ABs, in view of these log K(OA) values, can be classified as compounds of relatively low (Mono-, Di- and some of Tri- Ct-ABs with values of log K(OA) around 8 to 10) environmental mobility (most of Tri- to Nona-Ct-ABs and Deca-Ct-AB homologues with values of log K(OA) >10), and with a potential to be adsorbed by soil particles.     

Mercury in European Blushers, Amanita rubescens, mushrooms and topsoils: bioconcentration potential and intake assessment

Total mercury content has been determined in fruiting bodies of European Blushers and topsoils collected from 11 sites across Poland in 2006-2008. Mercury analysis was carried out using a validated analytical method and cold-vapour atomic absorption (CV-AAS). The European Blusher effectively accumulated mercury in fruiting bodies. The mean values of total mercury in caps of European Blushers from background (uncontaminated) areas were from 0.22 to 1.0 (0.067-3.2) and in stipes from 0.16 to 0.65 (0.071-2.7) μg/g dry weight. In topsoil beneath to fruiting bodies, the median Hg concentration at 10 sites in Northern Poland varied between 0.030 and 0.072 (0.0096-0.19) μg/g dw, and in one site in Southern Poland was 0.20 (0.079-0.34) μg/g dw. Data on Hg in European Blushers from different countries were reviewed. The mean concentrations of total Hg in caps of European Blushers from two "pristine" sites in northern part of Poland were ～1.0 μg/g dw. A meal made with 300-500 g of fresh caps of European Blushers collected at such sites (assuming 90% water content in caps) can result in Hg intake of 0.0003-0.0005 mg Hg/kg bm (assuming a 60 kg bm), which is a dose equipotent to a new provisional tolerable weekly intake (PTWI) value set for inorganic Hg.     

Co-polymerization of penta-halogenated phenols in humic substances by catalytic oxidation using biomimetic catalysis

Introduction

A synthetic water-soluble meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrinate of iron(III) chloride, Fe-(TDCPPS)Cl, was employed to catalyze the oxidative co-polymerization of penta-halogenated phenols in two humic materials of different origin.

Materials and methods

Co-polymerization of pentachlorophenol (PCP) was followed by high-performance size-exclusion chromatography (HPSEC), the unbound PCP recovered from reacting humic solutions was evaluated by gas-chromatography/electron capture detector, and the oxidative catalyzed coupling of pentafluorophenol (PFP) into humic matter was assessed by liquid-state ¹⁹F-NMR spectroscopy. HPSEC showed that the catalyzed oxidative coupling between PCP and humic molecules increased the apparent weight-average molecular weight (M _w) values in both humic substances.

Results and discussion

HPSEC further indicated that the co-polymerization reaction turned the loosely bound humic supramolecular structures into more stable conformations, which could no longer be disrupted by the disaggregating effect of acetic acid. The occurrence of covalent linkages established between PCP and humic molecules was also suggested by the very little amount of PCP found free in solution after the catalyzed co-polymerization. ¹⁹F-NMR spectroscopy suggested that also PFP could be oxidatively coupled to humic materials. PFP-humic co-polymerization reaction produced ¹⁹F-spectra with many more ¹⁹F signals and wider chemical shifts spread than for PFP alone or PFP subjected to catalyzed coupling without humic matter.

Conclusions

These findings show that biomimetic iron-porphyrin is an efficient catalyst for the covalent binding of polyhalogenated phenols to humic molecules, thereby suggesting that the co-polymerization reaction may become a useful technology to remediate soils and waters contaminated by polyhalogenated phenols and their analogues.     

Concentrations of polychlorinated biphenyls in water from US Lake Ontario tributaries between 2004 and 2008

Research on the environmental fate and transport of PCBs in Lake Ontario basin depends, among other aspects, on the availability of representative data sets for upstream sources, but data are lacking for most US Lake Ontario tributaries. In this study, water samples were collected between September 2004 and October 2008 from five tributaries and were analyzed for 209 polychlorinated biphenyls (PCB) with high-resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) following EPA Method 1668A. Total PCB concentrations ranged between 0.31 and 42.75 ng L⁻¹. Congeners between Di and Hexa PCBs accounted between 70 and 99% of the total PCB. The tributary with highest PCB concentrations presented similar pattern and percentage levels to Aroclor 1242. Total average loads for the sampling events ranged between 1.85 g d⁻¹ and 59.08 g d⁻¹. PCB concentrations were evaluated against other variables and other studies (including different matrices) to better understand their transport. The methodology used is reliable to assess PCB contamination in surface water.     

Role of back diffusion and biodegradation reactions in sustaining an MTBE/TBA plume in alluvial media

A methyl tert-butyl ether (MTBE) / tert-butyl alcohol (TBA) plume originating from a gasoline spill in late 1994 at Vandenberg Air Force Base (VAFB) persisted for over 15 years within 200 feet of the original spill source. The plume persisted until 2010 despite excavation of the tanks and piping within months after the spill and excavations of additional contaminated sediments from the source area in 2007 and 2008. The probable history of MTBE concentrations along the plume centerline at its source was estimated using a wide variety of available information, including published details about the original spill, excavations and monitoring by VAFB consultants, and our own research data. Two-dimensional reactive transport simulations of MTBE along the plume centerline were conducted for a 20-year period following the spill. These analyses suggest that MTBE diffused from the thin anaerobic aquifer into the adjacent anaerobic silts and transformed to TBA in both aquifer and silt layers. The model reproduces the observation that after 2004 TBA was the dominant solute, diffusing back out of the silts into the aquifer and sustaining plume concentrations much longer than would have been the case in the absence of such diffusive exchange. Simulations also suggest that aerobic degradation of MTBE or TBA at the water table in the overlying silt layer significantly affected concentrations of MTBE and TBA by limiting the chemical mass available for back diffusion to the aquifer.     

Impact of the earthworm Lumbricus terrestris (L.) on As, Cu, Pb and Zn mobility and speciation in contaminated soils

To assess the risks that contaminated soils pose to the environment properly a greater understanding of how soil biota influence the mobility of metal(loid)s in soils is required. Lumbricus terrestris L. were incubated in three soils contaminated with As, Cu, Pb and Zn. The concentration and speciation of metal(loid)s in pore waters and the mobility and partitioning in casts were compared with earthworm-free soil. Generally the concentrations of water extractable metal(loid)s in earthworm casts were greater than in earthworm-free soil. The impact of the earthworms on concentration and speciation in pore waters was soil and metal specific and could be explained either by earthworm induced changes in soil pH or soluble organic carbon. The mobilisation of metal(loid)s in the environment by earthworm activity may allow for leaching or uptake into biota.     

Impact of earthworms on trace element solubility in contaminated mine soils amended with green waste compost

The common practice of remediating metal contaminated mine soils with compost can reduce metal mobility and promote revegetation, but the effect of introduced or colonising earthworms on metal solubility is largely unknown. We amended soils from an As/Cu (1150 mgAs kg⁻¹ and 362 mgCu kg⁻¹) and Pb/Zn mine (4550 mgPb kg⁻¹ and 908 mgZn kg⁻¹) with 0, 5, 10, 15 and 20% compost and then introduced Lumbricus terrestris. Porewater was sampled and soil extracted with water to determine trace element solubility, pH and soluble organic carbon. Compost reduced Cu, Pb and Zn, but increased As solubility. Earthworms decreased water soluble Cu and As but increased Pb and Zn in porewater. The effect of the earthworms decreased with increasing compost amendment. The impact of the compost and the earthworms on metal solubility is explained by their effect on pH and soluble organic carbon and the environmental chemistry of each element.     

Indicators of waste management efficiency related to different territorial conditions

The amount of waste produced and the control of separate collection are crucial issues for the planning of a territorial Integrated Waste Management System, enabling the allocation of each sorted waste fraction to the proper treatment and recycling processes. The present study focuses on assessing indicators of different waste management systems in areas characterized by different territorial conditions. The investigated case study concerns the municipalities of Emilia Romagna (northern Italy), which present a rather uniform socioeconomic situation, but a variety of geographic, urban and waste management characteristics. A survey of waste generation and collection rates was carried out, and correlated with the different territorial conditions, classifying the municipalities according to altitude and population density. The best environmental performances, in terms of high separate collection rate, were found on average in rural areas in the plain, while the lowest waste generation was associated with rural hill towns.     

Arsenic uptake and speciation and the effects of phosphate nutrition in hydroponically grown kikuyu grass (Pennisetum clandestinum Hochst)

Background

This work focuses on the accumulation and mobility properties of arsenic (As) and the effects of phosphate (P) on its movement in Pennisetum clandestinum Hochst (kikuyu grass), grown hydroponically under increasing arsenate (As(V)) concentrations. The uptake of both ions and the relative kinetics show that phosphate is an efficient competitive inhibitor of As(V) uptake. The P/As uptake rate ratios in roots indicate that P is taken up preferentially by P/As transporters. An arsenite (As(III)) efflux from roots was also found, but this decreased when the arsenate concentration in the solution exceeded 5???M.

Methods

Increases in both arsenite and arsenate concentrations in roots were observed when the arsenate concentration in the solution was increased, and the highest accumulation of As(III) in roots was found when plants were grown at 5???M As(V). The low ratios of As accumulated in shoots compared to roots suggest limited mobility of the metalloid within Kikuyu plants.

Results

The results indicate that arsenic resistance in kikuyu grass in conditions of moderate exposure is mainly dependent on the following factors: 1) phosphate nutrition: P is an efficient competitive inhibitor of As(V) uptake because of the higher selectivity of membrane transporters with respect to phosphate rather than arsenate; and 2) a detoxification mechanism including a reduction in both arsenate and arsenite root efflux.

Conclusions

The As tolerance strategy of Kikuyu limits arsenate uptake and As translocation from roots to shoots; therefore, this plant cannot be considered a viable candidate for use in the phytoextraction of arsenic from contaminated soils or water.