Modeling the photo-oxidation of dissolved organic matter by ultraviolet radiation in freshwater lakes: implications for mercury bioavailability

Uncertainties in projected ultraviolet (UV) radiation may lead to future increases in UV irradiation of freshwater lakes. Because dissolved organic carbon (DOC) is the main binding phase for mercury (Hg) in freshwater lakes, an increase in DOC photo-oxidation may affect Hg speciation and bioavailability. We quantified the effect of DOC concentration on the rate of abiotic DOC photo-oxidation for five lakes (DOC=3.27-12.3 mg L(-1)) in Kejimkujik National Park, Canada. Samples were irradiated with UV-A or UV-B radiation over a 72-h period. UV-B radiation was found to be 2.36 times more efficient at photo-oxidizing DOC than UV-A, with energy-normalized rates of dissolved inorganic carbon (DIC) production ranging from 3.8×10(-5) to 1.1×10(-4) mg L(-1)J(-1) for UV-A, and from 6.0×10(-5) to 3.1×10(-4) mg L(-1)J(-1) for UV-B. Energy normalized rates of DIC production were positively correlated with DOC concentrations. Diffuse integrated attenuation coefficients were quantified in situ (UV-A K(d)=0.056-0.180 J cm(-1); UV-B K(d)=0.015-0.165 J cm(-1)) and a quantitative depth-integrated model for yearly DIC photo-production in each lake was developed. The model predicts that, UV-A produces between 3.2 and 100 times more DIC (1521-2851 mg m(-2) year(-1)) than UV-B radiation (29.17-746.7 mg m(-2) year(-1)). Future increases in UV radiation may increase DIC production and increase Hg bioavailability in low DOC lakes to a greater extent than in high DOC lakes.     

Uranium uptake by hydroponically cultivated crop plants

Hydroponicaly cultivated plants were grown on medium containing uranium. The appropriate concentrations of uranium for the experiments were selected on the basis of a standard ecotoxicity test. The most sensitive plant species was determined to be Lactuca sativa with an EC₅₀ value about 0.1 mM. Cucumis sativa represented the most resistant plant to uranium (EC₅₀ = 0.71 mM). Therefore, we used the uranium in a concentration range from 0.1 to 1 mM.Twenty different plant species were tested in hydroponic solution supplemented by 0.1 mM or 0.5 mM uranium concentration. The uranium accumulation of these plants varied from 0.16 mg/g DW to 0.011 mg/g DW. The highest uranium uptake was determined for Zea mays and the lowest for Arabidopsis thaliana. The amount of accumulated uranium was strongly influenced by uranium concentration in the cultivation medium. Autoradiography showed that uranium is mainly localized in the root system of the plants tested. Additional experiments demonstrated the possibility of influencing the uranium uptake from the cultivation medium by amendments. Tartaric acid was able to increase uranium uptake by Brassica oleracea and Sinapis alba up to 2.8 times or 1.9 times, respectively. Phosphate deficiency increased uranium uptake up to 4.5 times or 3.9 times, respectively, by Brassica oleracea and S. alba. In the case of deficiency of iron or presence of cadmium ions we did not find any increase in uranium accumulation.     

Converging impact assessment discourses for sustainable development: the case of Flanders,Belgium

The scientific field of impact assessment encompasses various ‘traditions’, each reflecting a set of particular policy objectives. This paper analyses two types of impact assessment. Regulatory impact analysis focuses on better regulation and competitiveness, while sustainability assessment fosters a holistic approach centred on the values of sustainable development. Through an analysis of the political discourses at the level of the European Union and at the sub-national level of the Flemish Region of Belgium, elements of convergence between the better regulation and sustainable development discourse are identified. The paper analyses how integrated impact assessment can be an integrative tool that allows to merge both discourses and to implement them in day-to-day decision-making. The potential of the existing Flemish regulatory impact analysis framework to be the starting point of an integrated assessment scheme for sustainable development is advocated and motivated.     

Effects of biochar and the earthworm Eisenia fetida on the bioavailability of polycyclic aromatic hydrocarbons and potentially toxic elements

Polycyclic aromatic hydrocarbons (PAHs) and potentially toxic elements (PTEs) were monitored over 56 days in calcareous contaminated-soil amended with either or both biochar and Eisenia fetida. Biochar reduced total (449 to 306 mg kg⁻¹) and bioavailable (cyclodextrin extractable) (276 to 182 mg kg⁻¹) PAHs, PAH concentrations in E. fetida (up to 45%) but also earthworm weight. Earthworms increased PAH bioavailability by >40%. Combined treatment results were similar to the biochar-only treatment. Earthworms increased water soluble Co (3.4 to 29.2 mg kg⁻¹), Cu (60.0 to 120.1 mg kg⁻¹) and Ni (31.7 to 83.0 mg kg⁻¹) but not As, Cd, Pb or Zn; biochar reduced water soluble Cu (60 to 37 mg kg⁻¹). Combined treatment results were similar to the biochar-only treatment but gave a greater reduction in As and Cd mobility. Biochar has contaminated land remediation potential, but its long-term impact on contaminants and soil biota needs to be assessed.     

On airborne nano/micro-sized wear particles released from low-metallic automotive brakes

The paper addresses the wear particles released from commercially available “low-metallic” automotive brake pads subjected to brake dynamometer tests. Particle size distribution was measured in situ and the generated particles were collected. The collected fractions and the original bulk material were analyzed using several chemical and microscopic techniques. The experiments demonstrated that airborne wear particles with sizes between 10 nm and 20 μm were released into the air. The numbers of nanoparticles (<100 nm) were by three orders of magnitude larger when compared to the microparticles. A significant release of nanoparticles was measured when the average temperature of the rotor reached 300 °C, the combustion initiation temperature of organics present in brakes. In contrast to particle size distribution data, the microscopic analysis revealed the presence of nanoparticles, mostly in the form of agglomerates, in all captured fractions. The majority of elements present in the bulk material were also detected in the ultra-fine fraction of the wear particles.     

A review of biochars' potential role in the remediation, revegetation and restoration of contaminated soils

Biochars are biological residues combusted under low oxygen conditions, resulting in a porous, low density carbon rich material. Their large surface areas and cation exchange capacities, determined to a large extent by source materials and pyrolysis temperatures, enables enhanced sorption of both organic and inorganic contaminants to their surfaces, reducing pollutant mobility when amending contaminated soils. Liming effects or release of carbon into soil solution may increase arsenic mobility, whilst low capital but enhanced retention of plant nutrients can restrict revegetation on degraded soils amended only with biochars; the combination of composts, manures and other amendments with biochars could be their most effective deployment to soils requiring stabilisation by revegetation. Specific mechanisms of contaminant-biochar retention and release over time and the environmental impact of biochar amendments on soil organisms remain somewhat unclear but must be investigated to ensure that the management of environmental pollution coincides with ecological sustainability.     

Emission reductions from woody biomass waste for energy as an alternative to open burning

Woody biomass waste is generated throughout California from forest management, hazardous fuel reduction, and agricultural operations. Open pile burning in the vicinity of generation is frequently the only economic disposal option. A framework is developed to quantify air emissions reductions for projects that alternatively utilize biomass waste as fuel for energy production. A demonstration project was conducted involving the grinding and 97-km one-way transport of 6096 bone-dry metric tons (BDT) of mixed conifer forest slash in the Sierra Nevada foothills for use as fuel in a biomass power cogeneration facility. Compared with the traditional open pile burning method of disposal for the forest harvest slash, utilization of the slash for fuel reduced particulate matter (PM) emissions by 98% (6 kg PM/BDT biomass), nitrogen oxides (NOx) by 54% (1.6 kg NOx/BDT), nonmethane volatile organics (NMOCs) by 99% (4.7 kg NMOCs/BDT), carbon monoxide (CO) by 97% (58 kg CO/BDT), and carbon dioxide equivalents (CO2e) by 17% (0.38 t CO2e/BDT). Emission contributions from biomass processing and transport operations are negligible. CO2e benefits are dependent on the emission characteristics of the displaced marginal electricity supply. Monetization of emissions reductions will assist with fuel sourcing activities and the conduct of biomass energy projects.     

Assessment of exposure to PCB 153 from breast feeding and normal food intake in individual children using a system approach model

Investigators have typically relied on a single or few discrete time points as measures of polychlorinated biphenyl (PCB) body burden, however health effects are more likely to be the result of integrative exposure in time, optionally expressed as an area under the time curve (AUC) of PCB serum concentration. Using data from a subgroup of 93 infants from a birth cohort in eastern Slovakia—a region highly polluted by PCBs—we fit a system type model, customized to our longitudinal measures of serum PCB concentrations in cord, 6, 16, and 45 month blood specimens. The most abundant congener, PCB 153, was chosen for modeling purposes. In addition to currently used methods of exposure assessment, our approach estimates a concentration time profile for each subject, taking into account mean residence time of PCB 153 molecules in the body, duration of breast feeding, hypothetical PCB 153 concentration in steady-state without breast feeding and alternately without normal food intake. Hypothetical PCB 153 concentration in steady-state without normal food intake correlates with AUC (r = 0.84, p < 0.001) as well as with duration of breast feeding (r = 0.64, p < 0.001). It makes possible to determine each subject’s exposure profile expressed as AUC of PCBs serum concentration with a minimum model parameters. PCB body burden in most infants was strongly associated with duration of breast feeding in most, but not all children, was apparent from model output.     

Free and conjugated estrogen exports in surface-runoff from poultry litter-amended soil

Land application of animal manures such as poultry litter is a common practice, especially in states with surplus manure. Past studies have shown that animal manure may contain estrogens, which are classified as endocrine-disrupting chemicals and may pose a threat to aquatic and wildlife species. We evaluated the concentrations of estrogens in surface runoff from experimental plots (5 x 12 m each) receiving raw and pelletized poultry litter. We evaluated the free (estrone, E1; 17beta-estradiol, E2beta; estriol, E3) and conjugate forms (glucuronides and sulfates) of estrogens, which differ in their toxicity. Sampling was performed for 10 natural storm events over a 4-mo period (April-July 2008). Estrogen concentrations were screened using enzyme-linked immunosorbent assay (ELISA), followed by quantification using liquid chromatography with tandem mass spectrometry (LC/MS/MS). Concentrations of estrogens from ELISA were much higher than the LC/MS/MS values, indicating crossreactivity with organic compounds. Exports of estrogens were much lower from soils amended with pelletized poultry litter than the raw form of the litter. No-tillage management practice also resulted in a lower export of estrogens with surface runoff compared with reduced tillage. The concentrations and exports of conjugate forms of estrogens were much higher than the free forms for some treatments, indicating that the conjugate forms should be considered for a comprehensive assessment of the threat posed by estrogens.     

Fluorescent dye tracing for defining chlorinated ethene plume remediation targets

Three fluorescent dye traces were designed by Zapata Incorporated at a large portion of Tinker Air Force Base (AFB) near Oklahoma City, Oklahoma, to replicate the migration of chlorinated ethene plumes from two target source areas and determine if commingling of those plumes has occurred. The target source areas are spatially separated, contributed contaminants into two aquifers, and were to be remediated from two different financial mechanisms. The nature of the shared fiscal responsibility for remediation of the commingled plumes was unclear. Background sampling was performed to verify that the preferred conservative dyes planned for use were suitable for the site. The fluorescent dyes used were fluorescein and eosine. Eosine dye was introduced into two wells in the upper saturated zone (USZ) under Building 3001 in July 2008. Fluorescein dye was introduced into four monitoring wells screened in the lower saturated zone (LSZ) and the lower lower saturated zone (LLSZ) in July 2008 at the industrial wastewater treatment plant. Zapata then conducted a second dye trace using fluorescein dye in a third USZ well to confirm the results of the eosine dye trace in the USZ under Building 3001. © 2010 Wiley Periodicals, Inc.