Assessment of global industrial-age anthropogenic arsenic contamination

Arsenic, a carcinogenic trace element, threatens not only the health of millions of humans and other living organisms, but also global sustainability. We present here, for the first time, the global industrial-age cumulative anthropogenic arsenic production and its potential accumulation and risks in the environment. In 2000, the world cumulative industrial-age anthropogenic arsenic production was 4.53 million tonnes. The world-wide coal and petroleum industries accounted for 46% of global annual gross arsenic production, and their overall contribution to industrial-age gross arsenic production was 27% in 2000. Global industrial-age anthropogenic As sources (as As cumulative production) follow the order: As mining production >As generated from coal >As generated from petroleum. The potential industrial-age anthropogenic arsenic input in world arable surface in 2000 was 2.18 mg arsenic kg^–1, which is 1.2 times that in the lithosphere. The development of substitute materials for arsenic applications in the agricultural and forestry industries and controls of arsenic emissions from the coal industry may be possible strategies to significantly decrease arsenic pollution sources and dissipation rates into the environment.     

Simulation of pesticide runoff at Rosemaund Farm (UK) using the SoilFug model

A validation exercise of the SoilFug model using field runoff data from Rosemaund Farm (UK) is described. A comparison has been made of modelled and measured concentrations of several pesticides in surface water and soil during and after specific rain events following application. The field experiments were designed to obtain data on rainfall, outflows of water, pesticide application rates and concentrations in soil and water. The results were satisfactory for the undissociated pesticides (atrazine, carbofuran, dimethoate, isoproturon, lindane, simazine and trifluralin), whose concentrations in water were mostly predicted within an order of magnitude of measured data. The results for the dissociated pesticides (dichlorprop, MCPA, mecoprop) were less satisfactory, giving generally much higher predicted concentrations in water. The use of the SoilFug model is suggested for the calculation of predicted environmental concentrations (PECs) in water, since it generally produces acceptable results from a relatively small set of input data, most of which is generally available.     

In situ modification of an aquifer material by a cationic surfactant to enhance retardation of organic contaminants

Sorption of hexadecyltrimethylammonium chloride (HDTMA), a cationic surfactant, on aquifer material from Columbus AFB, Mississippi, U.S.A., was examined. Transport studies using flow-through columns and a box model aquifer showed that an almost stationary zone of HDTMA-modified aquifer material could be produced in situ without a significant decrease in hydraulic conductivity.Perchloroethylene (PCE) and naphthalene sorption isotherms on the HDTMA-modified aquifer material were linear, and sorption coefficients were increased by over two orders of magnitude relative to the unmodified material. The retardation of PCE by insitu emplaced HDTMA zones within a column was examined. Agreement between batch- and column-derived sorption coefficients and breakthrough curve symmetry indicates that local equilibrium was attained. Significant retardation of a naphthalene plume by an in situ emplaced surfactant zone was demonstrated in the box model aquifer system.The experimental results indicate that it is feasible to create in situ a sorbent zone within an aquifer using cationic surfactants. In most situations, the sorbent zone concept needs to be coupled with contaminant degradation processes for sorbent emplacement to be a practical tool in the remediation of groundwater contamination sites. Sorbent zones may be of benefit in the engineering of suitable environments for microbial or abiotic degradation reactions and by providing time slow reactions to occur.     

Effects of biofilm growth on flow and transport through a glass parallel plate fracture

The effects of biofilm growth on flow and solute transport through a sandblasted glass parallel plate fracture was investigated. The fracture was inoculated using soil microorganisms. Glucose, oxygen and other nutrients were supplied to support growth. The biomass initially formed discrete clusters attached to the glass surfaces, but over time formed a continuous biofilm. From dye tracer tests conducted during biofilm growth, it was observed that channels and low-permeability zones dominated transport. The hydraulic conductivity of the fracture showed a sigmoidal decrease with time. The hydraulic conductivity was reduced by a factor of 0.033, from 18 to 0.6 cm/s, corresponding to a 72% decrease in the hydraulic aperture, from 500 to 140 microm. In contrast, the mass balance aperture, determined from fluoride tracer tests, remained relatively constant, indicating that the impact of biomass growth on effective fracture porosity was much less than the effect on hydraulic conductivity. Analyses of pre-biofilm tracer tests revealed that both Taylor dispersion and macrodispersion were influencing transport. During biofilm growth, only macrodispersion was dominant. The macrodispersion coefficient alpha(macro) was found to increase logarithmically with hydraulic conductivity reduction.     

Screening the wetland plant species Alisma plantago-aquatica, Carex rostrata and Phalaris arundinacea for innate tolerance to zinc and comparison with Eriophorum angustifolium and Festuca rubra Merlin

Several wetland plant species appear to have constitutive metal tolerance. In previous studies, populations from contaminated and non-contaminated sites of the wetland plants Typha latifolia, Phragmites australis, Glyceria fluitans and Eriophorum angustifolium were found to be tolerant to high concentrations of metals. This study screened three other species of wetland plants: Alisma plantago-aquatica, Carex rostrata and Phalaris arundinacea for innate tolerance to zinc. The degree of tolerance was compared to known zinc-tolerant E. angustifolium and Festuca rubra Merlin. It was found that A. plantago-aquatica and P. arundinacea did not posses innate tolerance to zinc, but that C. rostrata was able to tolerate elevated levels of zinc, at levels comparable to those tolerated by E. angustifolium and F. rubra Merlin. The findings support the theory that some wetland angiosperm species tend to be tolerant to exposure to high levels of metals, regardless of their origin.     

Uptake of heavy metals and As by Brassica juncea grown in a contaminated soil in Aznalcóllar (Spain): the effect of soil amendments

Two crops of Brassica juncea (L.) Czern. were grown in a field experiment, at the site affected by the toxic spillage of acidic, metal-rich waste in Aznalcóllar (Seville, Spain), to study its metal accumulation and the feasibility of its use for metal phytoextraction. The effects of organic soil amendments (cow manure and mature compost) and lime on biomass production and plant survival were also assessed; plots without organic amendment and without lime were used as controls. Plots, with or without organic amendment, having pH < 5 were limed for the second crop. Soil acidification conditioned plant growth and metal accumulation. The addition of lime and the organic amendments achieved higher plant biomass production, although effects concerning metal bioavailability and accumulation were masked somewhat by pH variability with time and between and within plots. Tissue metal concentrations of B. juncea were elevated for Zn, Cu and Pb, especially in leaves of plants from plots with low pH values (maxima of 2029, 71 and 55 microg g(-1), respectively). The total uptake of heavy metals in the plants was relatively low, emphasising the problems faced when attempting to employ phytoextraction for clean-up of pluri-contaminated sites.     

Catalytic and electrocatalytic hydrogenolysis of brominated diphenyl ethers

Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental contaminants due to their use as additive flame-retardants. Conventional catalytic hydrogenolysis in methanol solution and electrocatalytic hydrogenolysis in aqueous methanol were examined as methods for debrominating mono- and di-bromodiphenyl ethers, as well as a commercial penta-PBDE mixture, in each case using palladium on alumina as the catalyst. Electrocatalytic hydrogenolysis employed a divided flow-through batch cell, with reticulated vitreous carbon cathodes and IrO2/Ti dimensionally stable anodes. Both methods gave efficient sequential debromination, with essentially complete removal of bromine from the PBDEs, but the electrocatalytic method was limited by the poor solubility of PBDEs in aqueous methanol.     

The fate of estrogenic hormones in an engineered treatment wetland with dense macrophytes.

Recently, the estrogenic hormones 17beta-estradiol (E2) and 17alpha-ethinyl estradiol (EE2) have been detected in municipal wastewater effluent and surface waters at concentrations sufficient to cause feminization of male fish. To evaluate the fate of steroid hormones in an engineered treatment wetland, lithium chloride, E2, and EE2 were added to a treatment wetland test cell. Comparison of hormone and tracer data indicated that 36% of the E2 and 41% of the EE2 were removed during the cell's 84-h hydraulic retention time (HRT). The observed attenuation was most likely the result of sorption to hydrophobic surfaces in the wetland coupled with biotransformation. Sorption was indicated by the retardation of the hormones relative to the conservative tracer. Biotransformation was indicated by elevated concentrations of the E2 metabolite, estrone. It may be possible to improve the removal efficiency by increasing the HRT or the density of plant materials.     

Structure elucidation of four possible biogenic organohalogens using isotope exchange mass spectrometry

The molecular structures of four unknown bioaccumulating halogenated compounds, C10H6N2Br3Cl3, C10H6N2Br4Cl2, C10H6N2Br5Cl, and C10H6N2Br6 were characterized using isotope exchange positive chemical ionization (IE-PCI) mass spectrometry (MS) and identified by comparison to synthesized standards. NH3 and ND3 were used as reagent gases for the IE-PCI-MS experiment. The shift in mass of the quasimolecular ion between the NH3 and ND3 PCI obtained spectra indicated the number of exchangeable hydrogens attached to the two nitrogen atoms in C10H6N2Br4Cl2, and thus the type of amines present (primary, secondary, or tertiary). 19 compounds (13 amines of varying degree of substitution; six containing no nitrogen) were used as reference compounds and controls in the experiment to validate the IE-PCI technique. The results of the IE-PCI-MS indicated the presence of two tertiary amine functional groups. The molecular structures of the four hexahalogenated compounds were then proposed to be 1,1'-dimethyl-3,3',4,-tribromo-4',5,5'-trichloro-2,2'-bipyrrole, 1,1'-dimethyl-3,3',4,4'-tetrabromo-5,5'-dichloro-2,2'-bipyrrole, 1,1'-dimethyl-3,3',4,4',5-pentabromo-5'-chloro-2,2'-bipyrrole, and 1,1'-dimethyl-3,3',4,4',5,5'-hexabromo-2,2'-bipyrrole and subsequently synthesized. Comparison of retention times and electron capture negative ionization (ECNI) full scans on various gas chromatography (GC) columns between the synthesized bipyrroles and the corresponding unknown compounds in biota indicated that three of the unknown compounds--possible marine natural products--were the proposed halogenated dimethyl bipyrroles. The placement of the halogen atoms on the fourth compound, C10H6N2Br3Cl3 could not be unequivocally determined since the synthesized standard could not be fully characterized.     

Growth and nutrition of Quercus rubra L. seedlings and mature trees after three seasons of ozone exposure

Seedling growth and nutritional status have been shown to be sensitive to ozone, but the influence of multi-season ozone exposure on mature tree growth and nutrition has not been examined. To determine if seedlings and mature trees were similarly affected by ozone exposure, growth and nutrient concentrations in northern red oak (Quercus rubra L.) 4-year-old seedlings and 32-year-old mature trees were examined after treatment with subambient, ambient and twice ambient concentrations of ozone for three growing seasons. SUM00 values summed over the three growing seasons were 147, 255 and 507 ppm-h, respectively, for the subambient, ambient and twice ambient exposures. For mature trees, no influence of ozone treatment on lower stem diameter growth, stem growth within the mid-canopy and foliar biomass was observed. Seedling height was increased by ozone, but biomass and diameter were unaffected. A reduction in the specific leaf weight of leaves in response to ozone coincident with the loss of recurrent flushing was observed in seedlings. Ozone exposure reduced foliar nitrogen concentrations and increased woody tissue nutrient concentrations in seedlings and mature trees at the end of the third growing season. These results suggest an influence of ozone on retranslocation processes in seedlings and mature trees.