Aerosol light-scattering in The Netherlands

The relation between the (midday) aerosol light-scattering and the concentrations of nitrate and sulfate has been assessed at a site near the coast of the North Sea in The Netherlands. Midday was selected for the measurements because this is the time at which the aerosol is most effective in the scattering of solar radiation. Automated thermodenuders were used for the hourly measurement of the concentration of nitrate and sulfate with a lower detection limit of 0.1 μ m⁻³. The site is operational since October 1993. The first-year average dry aerosol light-scattering (measured with an integrating nephelometer at a wavelength of 525 nm) was 0.71 × 10⁻⁴ m^1̄. In arctic marine air the aerosol light-scattering was a factor of 10 lower than the average value, in polluted continental air it was up to a factor of 10 higher. The ratio of the total aerosol light-scattering to the concentration of sulfate was 20 m² g⁻¹. The contribution of nitrate to the aerosol light-scattering was higher than that of sulfate in the winter and of about equal magnitude in the summer period. In November and December of 1993, the humidity dependence of the aerosol light-scattering was investigated. Two types of (continental) aerosol were found with respect to the humidity behavior. One type showed a significant increase in light-scattering at the deliquescence points of ammonium nitrate and ammonium sulfate, with that of ammonium nitrate the most pronounced. The second type of continental aerosol did not show deliquescence, but followed the typical humidity dependence of aerosol in a supersaturated droplet state. In this latter aerosol type, nitrate dominated over sulfate. It was concluded from the study that the aerosol light-scattering in The Netherlands, in particular its humidity dependence, is governed by (ammonium) nitrate.     

Vanadium contamination and the relation between vanadium and other elements in wild birds

There is little information on vanadium (V) contamination in wildlife. In the present study, the mean V contents in liver and kidney from 41 wild Japanese water birds were less than 3.69 and 8.11 microg/g dry wt, respectively. The V contents in the liver and kidney of the spotbill duck were more than two times higher than those of other species in Japan. Spotbill ducks obtained in a residential district had a strong correlation between the V contents in the kidneys and those in the livers (R=0.924), and also between V and Ti, Cd, and Li contents in the liver (R>0.8). These results suggest that V accumulation in wild birds reflects the degree of environmental contamination.     

Biodegradation of 2,4,6-trichlorophenol in the presence of primary substrate by immobilized pure culture bacteria

In this study, pure strains that are capable of utilizing 2,4,6-trichlorophenol have been isolated from the mixed culture grown on substrates containing chlorophenolic compounds. Studies have been carried out on the capability of these isolated pure strains in suspended and immobilized forms to decompose 2,4,6-trichlorophenol. Additionally, the influence of primary substrates (e.g., phenol, 2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol) on the decomposition of 2,4,6-trichlorophenol by the isolated pure strains grown in immobilized form is also investigated. The results are: Through bacterial isolation and identification, three pure strains have been obtained: Pseudomonas spp. strain 01, Pseudomonas spp. strain 02 and Agrobacterium spp. Whether in suspended or immobilized forms, all strains have poor removal efficiencies of 2,4,6-trichlorophenol. However, addition of 200 mg/l phenol will enable the immobilized Pseudomonas spp. strain 01, and Pseudomonas spp. strain 02 to achieve 65% and 48% removal of 2,4,6-trichlorophenol, respectively. Addition of phenol will assist the immobilized Pseudomonas spp. strain 02 in achieving removal of 2,4,6-trichlorophenol but the removal efficiency is not good if the phenol concentration is too low. The optimum phenol concentration should be between 200 and 400 mg/l.     

Uptake rates of semipermeable membrane devices (SPMDs) for PCDDs, PCDFs and PCBs in water and sediment

Uptake rates of several PCDDs, PCDFs and PCBs were measured for semipermeable membrane devices (SPMDs) under controlled conditions in bulk water and sediment. The study was performed at 19 degrees C and 11 degrees C, and water and sediment concentrations were measured during the exposure. Linear uptake rates for specific PCDD/Fs and PCBs in 19 degrees C water varied from 34 to 111 l/m2 day and in 11 degrees C water from 8.8 to 96 l/m2 day for the whole SPMD. Uptake rates at 19 degrees C sediment ranged from 9.0 to 80 mgOC/m2 day and in 11 degrees C sediment, from 3.0 to 31, mgOC/m2 day. Partitioning of the compounds between membrane and lipid was also measured during the linear uptake phase. The membrane-lipid concentration ratios ranged from 0.02 to 1.11 depending on the compound, temperature, and bulk medium.     

The Aerosol Research and Inhalation Epidemiology Study (ARIES): PM2.5 mass and aerosol component concentrations and sampler intercomparisons

The Aerosol Research and Inhalation Epidemiology Study (ARIES) was designed to provide high-quality measurements of PM2.5, its components, and co-varying pollutants for an air pollution epidemiology study in Atlanta, GA. Air pollution epidemiology studies have typically relied on available data on particle mass often collected using filter-based methods. Filter-based PM2.5 sampling is susceptible to both positive and negative errors in the measurement of aerosol mass and particle-phase component concentrations in the undisturbed atmosphere. These biases are introduced by collection of gas-phase aerosol components on the filter media or by volatilization of particle phase components from collected particles. As part of the ARIES, we collected daily 24-hr PM2.5 mass and speciation samples and continuous PM2.5 data at a mixed residential-light industrial site in Atlanta. These data facilitate analysis of the effects of a wide variety of factors on sampler performance. We assess the relative importance of PM2.5 components and consider associations and potential mechanistic linkages of PM2.5 mass concentrations with several PM2.5 components. For the 12 months of validated data collected to date (August 1, 1998-July 31, 1999), the monthly average Federal Reference Method (FRM) PM2.5 mass always exceeded the proposed annual average standard (12-month average = 20.3 +/- 9.5 micrograms/m3). The particulate SO4(2-) fraction (as (NH4)2SO4) was largest in the summer and exceeded 50% of the FRM mass. The contribution of (NH4)2SO4 to FRM PM2.5 mass dropped to less than 30% in winter. Particulate NO3- collected on a denuded nylon filter averaged 1.1 +/- 0.9 micrograms/m3. Particle-phase organic compounds (as organic carbon x 1.4) measured on a denuded quartz filter sampler averaged 6.4 +/- 3.1 micrograms/m3 (32% of FRM PM2.5 mass) with less seasonal variability than SO4(2-).     

Occurrence of UV filter compounds from sunscreens in surface waters: regional mass balance in two Swiss lakes

Consumer care products often contain UV filters, organic compounds which absorb ultraviolet light. These compounds may enter surface waters directly (when released from the skin during swimming and bathing) or indirectly via wastewater treatment plants (when released during showering or washed from textiles). Predicted and measured UV filter concentrations were compared in a regional mass balance study for two Swiss lakes: Lake Zurich, a typical midland lake which is also an important drinking water resource, and Hüttnersee, a small bathing lake. Both lakes are extensively used for recreational activities and considerable direct input of UV filters is thus expected. This input was estimated from the number of visitors at swimming areas around the lakes and a survey of the usage of sunscreen products among these visitors. Possible additional indirect input via wastewater treatment plants was not considered in this study. The quantitatively most important UV filters, as indicated by the survey data, ethylhexyl methoxycinnamate, octocrylene, 4-methylbenzylidene camphor, butyl methoxydibenzoylmethane, and benzophenone-3, all lipophilic compounds, were selected for analysis by gas chromatography-mass spectrometry. Concentrations of individual UV filters in water from Lake Zurich were low, ranging from <2 ng l(-1) (detection limit) to 29 ng l(-1), and somewhat higher at Hüttnersee, ranging from <2 to 125 ng l(-1), with the highest concentrations found in summer, consistent with direct inputs to the lakes during this time. The concentrations were clearly lower than predicted from input estimates based on the surveys. This may be in part due to (i) an overestimation of these inputs (e.g. less than the 50% wash-off of UV filters assumed to occur during swimming), and (ii) some removal of these compounds from the lakes by degradation and/or sorption/sedimentation. UV filters were also detected in semipermeable membrane devices (SPMDs) deployed at Lake Zurich and Greifensee, another midland lake, at concentrations of 80-950 ng SPMD(-1), confirming the presence of the compounds in surface waters and indicating a certain potential for bioaccumulation. SPMD-derived water concentrations were in the range of 1-10 ng l(-1) and thus corresponded well with those determined in water directly. No UV filters were detected above blank levels in SPMDs deployed at a remote mountain lake used for background measurements.     

Photo-Fenton-assisted ozonation of p-Coumaric acid in aqueous solution

The degradation of p-Coumaric acid present in olive oil mill wastewater was investigated as a pretreatment stage to obtain more easily biodegradable molecules, with lower toxicity that facilitates subsequent anaerobic digestion. Thus, photo-Fenton-assisted ozonation has been studied and compared with ozonation at alkaline pH and conventional single ultraviolet (UV) and acid ozonation treatments. In the combined process, the overall kinetic rate constant was split into various components: direct oxidation by UV light, direct oxidation by ozone and oxidation by hydroxyl radicals. Molecular and/or radical ozone reaction was studied by conducting the reaction in the presence and absence of tert-butylalcohol at pHs 2, 7 and 9. Ozone oxidation rate increases with pH or by the addition of Fenton reagent and/or UV radiation due to generation of hydroxyl radicals, *OH. Hydrogen peroxide and ferrous ion play a double role during oxidation since at low concentrations they act as initiators of hydroxyl radicals but at high concentrations they act as radical scavengers. Finally, the additional levels of degradation by formation of hydroxyl radicals have been quantified in comparison to the conventional single processes and an equation is proposed for the reaction rate as a function of studied operating variables.     

Efficient use of Fe metal as an electron transfer agent in a heterogeneous Fenton system based on Fe0/Fe3O4 composites

In this work a novel heterogeneous Fenton system based on Fe(0)/Fe3O4 composites is described. The composites with several Fe(0)/Fe3O4 ratios were prepared by two different methods, i.e. mechanical alloying of Fe(0) and Fe3O4 powders and controlled reduction of Fe3O4 with H2. Reaction studies and detailed Conversion Electron M?ssbauer surface characterization of the composites Fe(0)/Fe3O4, Fe(0), Fe3O4, alpha-Fe2O3 and gamma-Fe2O3 suggested that Fe2+surf species are essential to produce an active Fenton system. Kinetic studies for the oxidation of the dye methylene blue, used as an organic model molecule, and for the peroxide decomposition suggest that the reactions proceed via HO* radicals generated from Fe2+surf species and H2O2 in a Fenton like mechanism. The increase in activity caused by the addition of Fe(0) is discussed in terms of a creation of Fe2+surf species during the preparation of the composite and by an electron transfer mechanism from Fe(0) to Fe3+surf during the Fenton reaction to regenerate the Fe2+surf active species.     

Natural products: seasonal variation in trichome counts and contents in Lycopersicum hirsutum f. glabratum

Wild tomato leaves possess a pest-resistance mechanism in their glandular trichomes and the exudates they produce. Type IV and VI glandular trichomes on the leaves of five wild tomato accessions of Lycopersicum hirsutum f. glabratum (PI 126449, PI 134417, PI 134418, PI 251304, and LA 407) grown under greenhouse conditions were counted. Major chemical compounds from glandular leaf trichomes of the accessions tested were extracted, purified, and quantified at different periods during the growing seasons by gas chromatography (GC) and mass spectrometry (GC/MS). The toxicity of two methylketones (2-undecanone and 2-tridecanone), the major constituents of the accessions tested, to adults of the sweetpotato whitefly, Bemisia tabaci (Gennadius) and fourth instar larvae of the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), was determined using no-choice bioassays. 2-undecanone caused 80% mortality of the fourth instar larvae of the CPB at the highest concentration tested (100 mg 2-undecanone mL(-1) of acetone) while 2-tridecanone caused 72% mortality of whiteflies at 20 mg 2-tridecanone mL(-1) of 65% ethanol. The concentration of 2-undecanone and 2-tridecanone on the leaves of each of the five accessions of L. hirsutum f. glabratum and the mass spectra of 2-undecanone and 2-tridecanone are presented. Overall, the concentration of 2-undecanone on the leaves was significantly higher than 2-tridecanone. Concentration of the two methylketones varied among accessions and sampling season. Plants produced the highest concentration of 2-undecanone during the month of August. On average, each plant of accession PI 251304 provided 354 g fresh leaves (averaging about 52,353 cm2 exposed leaf surface area) and produced 32.5 and 8.7 mg of 2-undecanone and 2-tridecanone, respectively. L. hirsutum f. glabratum accessions may become a valuable source of natural products, which could minimize reliance on synthetic pesticides.     

Growth of Dehalococcoides spp. and increased abundance of reductive dehalogenase genes in anaerobic PCB-contaminated sediment microcosms

Polychlorinated biphenyls (PCBs) contaminate 19% of US Superfund sites and represent a serious risk to human and environmental health. One promising strategy to remediate PCB-contaminated sediments utilizes organohalide-respiring bacteria (OHRB) that dechlorinate PCBs.

However, functional genes that act as biomarkers for PCB dechlorination processes (i.e., reductive dehalogenase genes) are poorly understood. Here, we developed anaerobic sediment microcosms that harbor an OHRB community dominated by the genus Dehalococcoides. During the 430-day microcosm incubation, Dehalococcoides 16S rRNA sequences increased two orders of magnitude to 10⁷ copies/g of sediment, and at the same time, PCB118 decreased by as much as 70%. In addition, the OHRB community dechlorinated a range of penta- and tetra-chlorinated PCB congeners including PCBs 66, 70?+?74?+?76, 95, 90?+?101, and PCB110 without exogenous electron donor. We quantified candidate reductive dehalogenase (RDase) genes over a 430-day incubation period and found rd14, a reductive dehalogenase that belongs to Dehalococcoides mccartyi strain CG5, was enriched to 10⁷ copies/g of sediment. At the same time, pcbA5 was enriched to only 10⁵ copies/g of sediment. A survey for additional RDase genes revealed sequences similar to strain CG5’s rd4 and rd8. In addition to demonstrating the PCB dechlorination potential of native microbial communities in contaminated freshwater sediments, our results suggest candidate functional genes with previously unexplored potential could serve as biomarkers of PCB dechlorination processes.