An investigation into reservoir NOM reduction by UV photolysis and advanced oxidation processes

A comparison of four treatment technologies for reduction of natural organic matter (NOM) in a reservoir water was made. The work presented here is a laboratory based evaluation of NOM treatment by UV-C photolysis, UV/H(2)O(2), Fenton's reagent (FR) and photo-Fenton's reagent (PFR). The work investigated ways of reducing the organic load on water treatment works (WTWs) with a view to treating 'in-reservoir' or 'in-pipe' before the water reaches the WTW. The efficiency of each process in terms of NOM removal was determined by measuring UV absorbance at 254 nm (UV(254)) and dissolved organic carbon (DOC). In terms of DOC reduction PFR was the most effective (88% removal after 1 min) however there were interferences when measuring UV(254) which was reduced to a lesser extent (31% after 1 min). In the literature, pH 3 is reported to be the optimal pH for oxidation with FR but here the reduction of UV(254) and DOC was found to be insensitive to pH in the range 3-7. The treatment that was identified as the most effective in terms of NOM reduction and cost effectiveness was PFR.     

Environmental assessment of different advanced oxidation processes applied to a bleaching Kraft mill effluent

Basic research on remediation of polluted sediment by leaching has, to date, been carried out exclusively with suspended material. For economic reasons, only solid-bed leaching is applicable to large-scale processes. Abiotic and microbial solid-bed leaching were comparatively studied in a percolator system using ripened and therefore permeable heavy metal polluted river sediment. In the case of abiotic leaching, sulfuric acid was supplied to the sediment by circulating water; the lower the pH of the percolating water, the higher the percolation flow, and the lower the solid-bed height was, the faster the heavy metals were solubilized. However, the pH and percolation flow are subjected to restrictions: strongly acidic conditions result in dissolution of mineral components, and the percolation flow must not exceed the bed permeability. And a high solid bed is an economic requirement. In the case of bioleaching, elemental sulfur added to the sediment was oxidized to sulfuric acid within the package which, in turn, solubilized the heavy metals. Here, the percolation flow and the solid-bed height did not affect the rate of metal solubilization. Solid-bed leaching on a larger scale will thus be much more efficient applying bioleaching with sulfur as the leaching agent than abiotic leaching with sulfuric acid.     

Sources of errors in assessing ozone visible symptoms on native vegetation

This paper aims to identify the problems regarding the evaluation of ozone (and ozone-like) symptoms, by examining the results of the 4th UN/ECE ICP-Forests Intercalibration Course for the assessment of ozone-induced visible symptoms. Trees, shrubs and herbaceous species were evaluated in a tree nursery, at Lattecaldo (Switzerland) and under open field conditions at Moggio (Italy). The main findings were: (i) the most expert surveyors tended to be grouped in the same cluster and, during the field exercises, they tended to assess in a more conservative manner compared to the less trained participants; (ii) the agreement was greater in assessing the absence rather than the presence of symptoms; (iii) typical interveinal stippling on the upper leaf surface was more accurately evaluated than discoloration; (iv) uncertainties resulted mainly for species which showed greater variability in their symptom manifestation, and for certain herbaceous species.     

Determination of potential sources of PCBs and PBDEs in sediments of the Niagara River

Sediments from Niagara River, an important waterway connecting two of the Great Lakes (Lake Erie to Lake Ontario), were analyzed for 14 congeners of polychlorinated biphenyls (PCBs) and 9 congeners of polybrominated diphenyl ethers (PBDEs) using accelerated solvent extraction and gas chromatography/mass spectrometry. Total concentrations of PCBs ranged from 1.7 to 124.6 ng/g were PCBs 138 and 153 were found in all samples. All sites but one showed PBDE in sediments with total concentrations as high as 148 ng/g, suggesting that PBDE is becoming an important class of POP. A land-use and coverage map was used to trace potential localized sources of PCB and PBDE contamination. Results indicate that the highest levels of PCBs and PBDEs were found in sediments collected from areas closest to the discharge locations of municipal wastewater treatment plants (WWTP) and local industries. This is the first study that suggests the importance of WWTP discharges as a potential source of PBDE contamination in the Great Lakes.     

Factors inhibiting bioremediation of soil contaminated with weathered oils and drill cuttings

Oily drill cuttings and a soil contaminated with weathered crude oils were treated by enhanced biodegradation under tropical conditions in industrial scaled experiments. Oil contaminants were characterized by gas chromatography and mass spectrometry. This allowed for the identification of a mixture of two crude oils in the contaminated soil. After 12 months of bioremediation process, the removal of hydrocarbons reached by biodegradation an extent of 60% although nutrient amendment with elevated concentration of N-urea had highly detrimental effects on the hydrocarbon degrading fungal populations due to the production of toxic concentration of ammonia gas by nitrification. The saturated hydrocarbons were extensively assimilated, though n-alkanes were not completely removed. Aromatic hydrocarbons were less degraded than saturated whereas resin and asphaltene fractions were, surprisingly, partly assimilated. In laboratory conditions, the residual hydrocarbons in the field-treated materials were 15-20% further degraded when metabolic byproducts resulting from biodegradation were diluted or removed.     

Sorption of pesticides on kaolinite and montmorillonite as a function of hydrophilicity

Pesticides and other organic species are adsorbed by soil via different mechanisms, with bond strengths that depend on the properties of both the soil and the pesticide. Since the clay fraction in soil is a preferential sorbent for organic matter, reference kaolinite and montmorillonite are useful models for studying the mechanism and the strength of sorption. This paper presents the results of batch experiments to investigate the interactions of kaolinite KGa-1 and montmorillonite SWy-1 with the following pesticides and organic species resulting from the natural degradation of pesticides in the environment: atrazine (1-chloro-3-ethylamino-5-isopropylamino-2,4,6-triazine), simazine (1-chloro-3,5-bisethylamino-2,4,6-triazine), diuron [1,1-dimethyl-3-(3,4-dichlorophenyl)urea], aniline, 4-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol. Each of these chemicals has different hydrophilicity. Systems containing 2.0 g of clay were put in contact with 100.0 mL of solutions of the pesticides at known concentration ranging from 1.0 to 5.0 mg/L, and the amount of solute adsorbed was evaluated through RP-HPLC analysis of the pesticide still present in the aqueous suspension. To test for electrostatic interactions between the clay surface and the pesticides, potentiometric titration was used to determine the permanent surface charge of clays. Experiments were performed at different pH values. The results indicate that, for the chemicals studied, neutral molecules are preferentially retained relative to ionized ones, and that montmorillonite is a more effective sorbent than kaolinite.     

Increased nitrogen in runoff and soil following 13 years of experimentally increased nitrogen deposition to a coniferous-forested catchment at Gårdsjön, Sweden

Beginning in 1991, we have added nitrogen (N) to the 0.5-ha, N-poor, coniferous-forested catchment G2 NITREX at G?rdsj?n, Sweden, to investigate the consequences of chronic elevated N deposition. We have added 40 kg N ha-1 yr-1 in fortnightly doses of NH4NO3 to the ambient 15 kg N ha-1 yr-1 by means of a sprinkling system. NO3 concentrations in runoff increased during 13 years from<1 to 70 microeq L-1, and in 2004 comprised about 10% of N input. Inhibition of NO3 immobilisation due to increased availability of NH4 might explain the increased leaching of NO3. C and N pools in the forest floor increased but C/N ratio has not changed. The increase in NO3 leaching thus occurred independently of change in C/N ratio. The results from G?rdsj?n demonstrate that increased leaching of inorganic N and decrease in C/N ratio respond to increased N deposition at greatly different time scales.     

Behaviour of alpha-, beta-, gamma-, and delta-hexachlorocyclohexane in the soil-plant system of a contaminated site

The behaviour of the organochlorine pesticide hexachlorocyclohexane (HCH) is investigated. The concentrations of alpha-, beta-, gamma-, and delta-HCH isomers were measured in soils, rhizosphere and vegetation in a contaminated area in Galicia (NW Spain). The total concentration of HCH in soils reached values close to 20,000 mgkg(-1). The plants analysed (Avena sativa L., Chenopodium spp., Solanum nigrum L., Cytisus striatus (Hill) Roth, and Vicia sativa L.) accumulated HCH, especially the beta-HCH isomer, in their tissues. The most likely mechanisms of HCH accumulation in plants were sorption of soil HCH on roots and sorption of volatilized HCH on aerial plant tissues. The concentrations of HCH obtained from the bulk and rhizosphere soils of selected plant species suggest that roots tend to reduce levels of the HCH isomers in the rhizosphere. The results reflect the importance of vegetation in the distribution of organochlorine compounds in the soil-plant system.     

Vegetational and mycorrhizal successions at a metal polluted site: Indications for the direction of phytostabilisation?

Plant communities on plots with different metal pollution levels were compared in a field study in order to select the most suitable plant species for the direction of secondary succession toward the targeted grassland vegetation. The vegetational succession showed a gradual increase in plant cover and the number of plant species on the less polluted locations. Two predominant grass species Calamagrostis varia and Sesleria caerulea were selected for phytostabilisation, but a severely reduced seed germination capacity obstructed their use in practice. The mycorrhizal succession showed a gradual replacement of non-mycorrhizal with mycorrhizal plant species. Similar levels of arbuscular mycorrhizal colonisation of a particular plant species may be developed within each growing season regardless of the levels of pollution, with the exception of vesicle/intraradical spore formation. The results suggest that lower overall mycorrhizal colonisation levels and increased vesicle/spore formation may be a part of a mycorrhizal strategy at the most polluted locations.     

Assessment of intermittent trace element pollution by moss bags

Moss bags of the aquatic bryophyte Rhynchostegium riparioides (Hedw.) C. Jens. were transplanted into an irrigation ditch in the Province of Vicenza (NE Italy), affected by intermittent trace element contamination due to galvanics. The study aimed at: (a) testing the ability of mosses to detect different patterns of pollution, (b) providing information about intensity and temporal extension of pollution events, and (c) localising the main sources. Moss bags were collected after 20, 34, 48 and 62 days of exposure. The concentrations of As, Cd, Cr, Cu, Hg, Mn, Ni, Pb and Zn in the desiccated apical shoots of mosses were determined by atomic absorption spectrophotometry. The mean concentrations measured in non-contaminated stations of a previous work were adopted as background values, to calculate the contamination factor (CF). Transplants were able to: (a) detect spatial patterns of bioaccumulation, (b) reveal chronic contamination by Pb and Cu, intermittent contamination by Cr, Zn, and Ni, and a release of Cd by moss bags, and (c) localise the main emission sources.