Seasonal and diurnal variations of carbonyl compounds in the urban atmosphere of Guangzhou, China

Seasonal and diurnal variations of carbonyl compounds were investigated at two sampling sites (Liwan and Wushan) in the ambient air of Guangzhou, China. Air samples were collected during 2005 from January to November, and carbonyl compounds were analyzed with HPLC. The results show that carbonyls exhibit distinct seasonal variation. The total concentrations of 21 carbonyls detected ranged from 2.64 to 103.6 μg m⁻³ at Liwan and from 5.46 to 89.9 μg m⁻³ at Wushan, respectively. The average total concentrations of carbonyls at both Liwan and Wushan decreased in order of summer>spring>autumn>winter. Formaldehyde, acetaldehyde, and acetone were the most abundant carbonyl compounds, which accounted for more than 60% of the total concentrations of carbonyls. The mean concentration ratios of summer/winter were all > 1.0 for the total concentrations and the individual carbonyl compound. The diurnal variation of carbonyls was not distinct in this study. The average concentration ratios of formaldehyde/acetaldehyde (C₁/C₂) varied from 0.71 to 1.32 and 0.65 to 1.14 at Liwan and Wushan, respectively, and the average concentration ratios of acetaldehyde/propionaldehyde (C₂/C₃) varied from 5.42 to 7.70 and 5.02 to 13.9 in Liwan and Wushan, respectively. Regarding photochemical reactivity of carbonyls and the ozone production, acetaldehyde, butyraldehyde, formaldehyde, and valeraldehyde account for 75-90% to the total propene-equivalent concentrations, while formaldehyde, acetaldehyde, valeraldehyde, butyraldehyde, and propionaldehyde contribute 89-96% to the total ozone formation potentials (ranging from 105 to 274 μg m^-3). The ozone formation potentials in summer were higher by 1-2 times than those in the other seasons.     

A comprehensive assessment of PM emissions from paved roads: Real-world Emission Factors and intense street cleaning trials

Compliance with air quality standards requires control of source emissions: fine exhaust particles are already subject to regulation but vehicle fleets increase whilst the non-exhaust emissions are totally uncontrolled. Emission inventories are scarce despite their suitability for researchers and regulating agencies for managing air quality and PM reduction measures. Only few countries in Europe proposed street cleaning as a possible control measure, but its effectiveness is still far to be determined.This study offers first estimates of Real-world Emission Factors for PM₁₀ and brake-wear elements and the effect on PM₁₀ concentrations induced by intense street cleaning trials.A straightforward campaign was carried out in the city of Barcelona with hourly elemental composition of fine and coarse PM to detect any short-term effect of street cleaning on specific tracers of non-exhaust emissions. Samples were analyzed by Particle Induced X-Ray Emission.Real-world Emission Factor for PM₁₀ averaged for the local fleet resulted to be 97 mg veh^− 1 km^− 1. When compared to other European studies, our EF resulted higher than what found in UK, Germany, Switzerland and Austria but lower than Scandinavian countries. For brake-related elements, total EFs were estimated, accounting for the sum of direct and resuspension emissions, in 7400, 486, 106 and 86 μg veh^− 1 km^− 1, respectively for Fe, Cu, Sn and Sb. In PM_2.5Fe and Cu emission factors were respectively 4884 and 306 μg veh^− 1 km^− 1.Intense street cleaning trials evidenced a PM₁₀ reduction at kerbside of 3 μg m^− 3 (mean daily levels of 54 μg m^− 3), with respect to reference stations. It is important to remark that such benefit could only be detected in small time-integration periods (12:00-18:00) since in daily values this benefit was not noticed. Hourly PM elemental monitoring allowed the identification of mineral and brake-related metallic particles as those responsible of the PM₁₀ reduction.     

Yield of trihalomethanes and haloacetic acids upon chlorinating algal cells, and its prediction via algal cellular biochemical composition

The major objective of the present study was to investigate the contribution of major biomolecules, including protein, carbohydrates and lipids, in predicting DBPs formation upon chlorination of algal cells. Three model compounds, including bovine serum albumin (BSA), starch and fish oil, as surrogates of algal-derived proteins, carbohydrates and lipids, and cells of three algae species, representing blue-green algae, green algae, and diatoms, were chlorinated in the laboratory. The results showed that BSA (27 μg mg⁻¹ C) and fish oil (50 μg mg⁻¹ C) produced more than nine times higher levels of chloroform than starch (3 μg mg⁻¹ C). For the formation of HAAs, BSA was shown to have higher reactivity (49 μg mg⁻¹ C) than fish oil and starch (5 μg mg⁻¹ C). For the algal cells, Nitzschia sp. (diatom) showed higher chloroform yields (48 μg mg⁻¹ C) but lower HAA yields (43 μg mg⁻¹ C) than Chlamydomonas sp. (green algae) (chloroform: 34 μg mg⁻¹ C; HAA: 62 μg mg⁻¹ C) and Oscillatoria sp. (blue-green algae) (chloroform: 26 μg mg⁻¹ C; HAA: 72 μg mg⁻¹ C). The calculated chloroform formation of cells from the three algal groups, based on their biochemical compositions, was generally consistent with the experimental data, while the predicted values for HAAs were significantly lower than the observed ones. As compared to humic substances, such as humic and fulvic acids, the algal cells appeared to be important precursors of dichloroacetic acid.     

The influence of disinfection on aquatic biodegradable organic carbon formation

The aim of this paper was to assess the extent of biodegradable dissolved organic carbon formation upon disinfection of water with chlorine dioxide. Wide diversity of natural waters has been subjected to reactions with various amounts of ClO₂. For comparison examined waters have also been treated with ozone and chlorine. The application of chlorine dioxide and ozone significantly changed the molecular weight distribution of aquatic organic matter. As a result significant amounts of biodegradable carboxylic acids and aldehydes were generated. The formic, acetic, oxalic and ketomalonic acids as well as formaldehyde, acetaldehyde, glyoxal, methylglyoxal were identified. The productivity of aldehydes calculated for all examined waters and disinfectants amounted 12.7-47.7 μg mg⁻¹ DOC in the case of ozonation, 1.3-8.1 μg mg⁻¹ DOC after chlorination and 1.7-9.4 μg mg⁻¹ DOC for ClO₂ treatment. The highest total concentration of carboxylic acids was determined after the ozonation processes. In this case the organic acids' formation potential was in the range 10.8-62.8 μg mg⁻¹ DOC. Relatively high formation potential (5.3-17.9 μg mg⁻¹ DOC) was determined after the oxidation with ClO₂ as well. In the case of chlorination, the productivity of organic acids was low and did not exceed 3.4 μg mg⁻¹ DOC. The relatively high correlation between BDOC formation and carboxylic acids' formation potential was observed. Thus, carboxylic acids' formation potential may be used as a measure of water potential to form BDOC.     

Atmospheric NH3 and NO2 concentration and nitrogen deposition in an agricultural catchment of Eastern China

To assess the atmospheric environmental impacts of anthropogenic reactive nitrogen in the fast-developing Eastern China region, we measured atmospheric concentrations of nitrogen dioxide (NO₂) and ammonia (NH₃) as well as the wet deposition of inorganic nitrogen (NO₃⁻ and NH₄⁺) and dissolved organic nitrogen (DON) levels in a typical agricultural catchment in Jiangsu Province, China, from October 2007 to September 2008_. The annual average gaseous concentrations of NO₂ and NH₃ were 42.2 μg m⁻³ and 4.5 μg m⁻³ (0 °C, 760 mm Hg), respectively, whereas those of NO₃⁻, NH₄⁺, and DON in the rainwater within the study catchment were 1.3, 1.3, and 0.5 mg N L⁻¹, respectively. No clear difference in gaseous NO₂ concentrations and nitrogen concentrations in collected rainwater was found between the crop field and residential sites, but the average NH₃ concentration of 5.4 μg m⁻³ in residential sites was significantly higher than that in field sites (4.1 μg m⁻³). Total depositions were 40 kg N ha⁻¹ yr⁻¹ for crop field sites and 30 kg N ha⁻¹ yr⁻¹ for residential sites, in which dry depositions (NO₂ and NH₃) were 7.6 kg N ha⁻¹ yr⁻¹ for crop field sites and 1.9 kg N ha⁻¹ yr⁻¹ for residential sites. The DON in the rainwater accounted for 16% of the total wet nitrogen deposition. Oxidized N (NO₃⁻ in the precipitation and gaseous NO₂) was the dominant form of nitrogen deposition in the studied region, indicating that reactive forms of nitrogen created from urban areas contribute greatly to N deposition in the rural area evaluated in this study.     

Evidences of non-reactive mercury-selenium compounds generated from cultures of Pseudomonas fluorescens

This work was designed to determine chemically inert mercury-selenium (Hg-Se) compounds formed in a culture of Pseudomonas fluorescens exposed to Hg²⁺ and Se^IV (selenite). To isolate these compounds, different digestion methods were studied and sodium dodecyl sulfate (SDS) lysis was selected. The Hg⁰ and non-reactive Hg were determined in two series of cultures containing 0.0-6.00 μg L⁻¹ Se^IV (0.0-76.0 μmol L⁻¹) in combination with low 5.00 μg L⁻¹ (0.025 μmol L⁻¹) or high 100 μg L⁻¹ (0.500 μmol L⁻¹) Hg²⁺. It was found that Hg⁰ formed in the culture decreased with the increase of initial Se^IV, while the non-reactive Hg increased with the Se^IV. In cultures with low initial [Hg²⁺], a median Se^IV (2.0 μg L⁻¹ or 25.3 μmol L⁻¹) resulted in about 70% of the added Hg²⁺ sequestered as non-reactive Hg, and in culture with high initial Hg²⁺, about 40% was sequestered. P. fluorescens was proved to be indispensible for the formation of the non-reactive Hg-Se compounds. The Hg:Se molar ratio in the non-reactive Hg-Se compounds was close to 1, suggesting the existence of mercuric selenide in cells. Mechanisms for the formation of the non-reactive Hg-Se compounds are proposed.     

Measurement of surface mercury fluxes at active industrial gold mines in Nevada (USA)

Mercury (Hg) may be naturally associated with the rock units hosting precious and base metal deposits. Active gold mines are known to have point source releases of Hg associated with ore processing facilities. The nonpoint source release of Hg to the air from the large area (hundreds to thousands of hectares) of disturbed and processed material at industrial open pit gold mines has not been quantified. This paper describes the field data collected as part of a project focused on estimating nonpoint source emissions of Hg from two active mines in Nevada, USA. In situ Hg flux data were collected on diel and seasonal time steps using a dynamic flux chamber from representative mine surfaces. Hg fluxes ranged from < 1500 ng m⁻² day⁻¹ for waste rock piles (0.6-3.5 μg g⁻¹) to 684,000 ng m⁻² day⁻¹ for tailings (2.8-58 μg g⁻¹). Releases were positively correlated with material Hg concentrations, surface grain size, and moisture content. Highest Hg releases occurred from materials under active cyanide leaching and from tailings impoundments containing processed high-grade ore. Data collected indicate that as mine sites are reclaimed and material disturbance ceases, emissions will decline. Additionally local cycling of atmospheric Hg (deposition and re-emission) was found to occur.     

Multiple site study of recent atmospheric metal (Pb, Zn and Cu) deposition in the NW Iberian Peninsula using peat cores

In order to estimate atmospheric metal deposition in Southern Europe since the beginning of the Industrial Period (~ 1850 AD), concentration profiles of Pb, Zn and Cu were determined in four ²¹⁰Pb-dated peat cores from ombrotrophic bogs in Serra do Xistral (Galicia, NW Iberian Peninsula). Maximum metal concentrations varied by a factor of 1.8 for Pb and Zn (70 to 128 μg g⁻¹ and 128 to 231 μg g⁻¹, respectively) and 3.5 for Cu (11 to 37 μg g⁻¹). The cumulative metal inventories of each core varied by a factor of 3 for all analysed metals (132 to 329 μg cm⁻² for Pb, 198 to 625 μg cm⁻² for Zn and 22 to 69 μg cm⁻² for Cu), suggesting differences in net accumulation rates among peatlands. Although results suggest that mean deposition rates vary within the studied area, the enhanced ²¹⁰Pb accumulation and the interpretation of the inventory ratios (²¹⁰Pb/Pb, Zn/Pb and Cu/Pb) in two bogs indicated that either a record perturbation or post-depositional redistribution effects must be considered. After correction, Pb, Zn and Cu profiles showed increasing concentrations and atmospheric fluxes since the mid-XX^th century to maximum values in the second half of the XX^th century. For Pb, maximum fluxes were observed in 1955-1962 and ranged from 16 to 22 mg m⁻² yr⁻¹ (mean of 18 ± 1 mg m⁻² yr⁻¹), two orders of magnitude higher than in the pre-industrial period. Peaks in Pb fluxes in Serra do Xistral before the period of maximum consumption of leaded petrol in Europe (1970s-1980s) suggest the dominance of local pollutant sources in the area (i.e. coal mining and burning). More recent peaks were observed for Zn and Cu, with fluxes ranging from 32 to 52 mg m⁻² yr⁻¹ in 1989-1996, and from 4 to 9 mg m⁻² yr⁻¹ in 1994-2001, respectively. Our results underline the importance of multi-core studies to assess both the integrity and reliability of peat records, and the degree of homogeneity in bog accumulation. We show the usefulness of using the excess ²¹⁰Pb inventory to distinguish between differential metal deposition, accumulation or anomalous peat records.     

Temporal variations in arsenic uptake by rice plants in Bangladesh: The role of iron plaque in paddy fields irrigated with groundwater

The transfer of arsenic to rice grains is a human health issue of growing relevance in regions of southern Asia where shallow groundwater used for irrigation of paddy fields is elevated in As. In the present study, As and Fe concentrations in soil water and in the roots of rice plants, primarily the Fe plaque surrounding the roots, were monitored during the 4-month growing season at two sites irrigated with groundwater containing ∼ 130 μg l^− 1 As and two control sites irrigated with water containing < 15 μg l^− 1 As. At both sites irrigated with contaminated water, As concentrations in soil water increased from < 10 μg l^− 1 to > 1000 μg l^− 1 during the first five weeks of the growth season and then gradually declined to < 10 μg l^− 1 during the last five weeks. At the two control sites, concentrations of As in soil water never exceeded 40 µg l^− 1. At both contaminated sites, the As content of roots and Fe plaque rose to 1000-1500 mg kg^− 1 towards the middle of the growth season. It then declined to ∼ 300 mg kg^− 1 towards the end, a level still well above As concentration of ∼ 100 mg kg^− 1 in roots and plaque measured throughout the growing season at the two control sites. These time series, combined with simple mass balance considerations, demonstrate that the formation of Fe plaque on the roots of rice plants by micro-aeration significantly limits the uptake of As by rice plants grown in paddy fields. Large variations in the As and Fe content of plant stems at two of the sites irrigated with contaminated water and one of the control sites were also recorded. The origin of these variations, particularly during the last month of the growth season, needs to be better understood because they are likely to influence the uptake of As in rice grains.     

Study of atmospheric mercury budget in East Asia using STEM-Hg modeling system

East Asia is the largest source region of global anthropogenic mercury emissions, and contributes to atmospheric mercury concentration and deposition in other regions. Similarly, mercury from the global pool also plays a role in the chemical transport of mercury in East Asia. Annual simulations of atmospheric mercury in East Asia were performed using the STEM-Hg modeling system to study the mass budgets of mercury in the region. The model results showed strong seasonal variation in mercury concentration and deposition, with signals from large point sources. The annual mean concentrations for gaseous elemental mercury, reactive gaseous mercury and particulate mercury in central China and eastern coastal areas were 1.8 ng m^− 3, 100 pg m^− 3 and 150 pg m^− 3, respectively. Boundary conditions had a strong influence on the simulated mercury concentration and deposition, contributing to 80% of the concentration and 70% of the deposition predicted by the model. The rest was caused by the regional emissions before they were transported out of the model domain. Using different oxidation rates reported for the Hg⁰-O₃ reaction (i.e., by Hall, 1995 vs. by Pal and Ariya, 2004) led to a 9% difference in the predicted mean concentration and a 40% difference in the predicted mean deposition. The estimated annual dry and wet deposition for East Asia in 2001 was in the range of 590-735 Mg and 482-696 Mg, respectively. The mercury mass outflow caused by the emissions in the domain was estimated to be 681-714 Mg yr^− 1. This constituted 70% of the total mercury emission in the domain. The greatest outflow occurred in spring and early summer.     

Determination of arsenic leaching from glazed and non-glazed Turkish traditional earthenware

Glazed and non-glazed earthenware is traditionally and widely used in Turkey and most of the Mediterranean and the Middle East countries for cooking and conservation of foodstuff. Acid-leaching tests have been carried out to determine whether the use of glazed and non-glazed earthenware may constitute a human health hazard risk to the consumers. Earthenware was leached with 4% acetic acid and 1% citric acid solutions, and arsenic in the leachates was measured using hydride generation atomic absorption spectrometry. Arsenic concentrations in the leach solution of non-glazed potteries varied from 30.9 to 800 μg L^− 1, while the glazed potteries varied generally from below the limit of detection (0.5 μg L^− 1) to 30.6 μg L^− 1, but in one poorly glazed series it reached to 110 μg L^− 1. Therefore, the risk of arsenic poisoning by poorly glazed and non-glazed potteries is high enough to be of concern. It appears that this is the first study reporting arsenic release from earthenware into food.     

Biomonitoring of Cd, Cr, Hg and Pb in the Baluarte River basin associated to a mining area (NW Mexico)

With the purpose of knowing seasonal variations of Cd, Cr, Hg and Pb in a river basin with past and present mining activities, elemental concentrations were measured in six fish species and four crustacean species in Baluarte River, from some of the mining sites to the mouth of the river in the Pacific Ocean between May 2005 and March 2006. In fish, highest levels of Cd (0.06 μg g^− 1 dry weight) and Cr (0.01 μg g^− 1) were detected during the dry season in Gobiesox fluviatilis and Agonostomus monticola, respectively; the highest levels of Hg (0.56 μg g^− 1) were detected during the dry season in Guavina guavina and Mugil curema. In relation to Pb, the highest level (1.65 μg g^− 1) was detected in A. monticola during the dry season. In crustaceans, highest levels of Cd (0.05 μg g^− 1) occurred in Macrobrachium occidentale during both seasons; highest concentration of Cr (0.09 μg g^− 1) was also detected in M. occidentale during the dry season. With respect to Hg, highest level (0.20 μg g^− 1) was detected during the rainy season in Macrobrachium americanum; for Pb, the highest concentration (2.4 μg g^− 1) corresponded to Macrobrachium digueti collected in the dry season. Considering average concentrations of trace metals in surficial sediments from all sites, Cd (p < 0.025), Cr (p < 0.10) and Hg (p < 0.15) were significantly higher during the rainy season. Biota sediment accumulation factors above unity were detected mostly in the case of Hg in fish during both seasons. On the basis of the metal levels in fish and crustacean and the provisional tolerable weekly intake of studied elements, people can eat up to 13.99, 0.79 and 2.34 kg of fish in relation to Cd, Hg and Pb, respectively; regarding crustaceans, maximum amounts were 11.33, 2.49 and 2.68 kg of prawns relative to levels of Cd, Hg and Pb, respectively.     

Effects of lanthanum and lanthanum-modified clay on growth, survival and reproduction of Daphnia magna

The novel lanthanum-modified clay water treatment technology (Phoslock^®) seems very promising in remediation of eutrophied waters. Phoslock^® is highly efficient in stripping dissolved phosphorous from the water column and in intercepting phosphorous released from the sediments. The active phosphorous-sorbent in Phoslock^® is the Rare Earth Element lanthanum. A leachate experiment revealed that lanthanum could be released from the clay, but only in minute quantities of 0.13-2.13 μg l⁻¹ for a worst-case Phoslock^® dosage of 250 mg l⁻¹. A life-history experiment with the zooplankton grazer Daphnia magna revealed that lanthanum, up to the 1000 μg l⁻¹ tested, had no toxic effect on the animals, but only in medium without phosphorous. In the presence of phosphorous, rhabdophane (LaPO₄ · nH₂O) formation resulted in significant precipitation of the food algae and consequently affected life-history traits. With increasing amounts of lanthanum, in the presence of phosphate, animals remained smaller, matured later, and reproduced less, resulting in lower population growth rates. Growth rates were not affected at 33 μg La l⁻¹, but were 6% and 7% lower at 100 and 330 μg l⁻¹, respectively, and 20% lower at 1000 μg l⁻¹. A juvenile growth assay with Phoslock^® tested in the range 0-5000 mg l⁻¹, yielded EC₅₀ (NOEC) values of 871 (100) and 1557 (500) mg Phoslock^® l⁻¹ for weight and length based growth rates, respectively. The results of this study show that no major detrimental effects on Daphnia are to be expected from Phoslock^® or its active ingredient lanthanum when applied in eutrophication control.     

Water, vegetation and sediment gradients in submerged aquatic vegetation mesocosms used for low-level phosphorus removal

Gradients in phosphorus (P) removal and storage were investigated over 6 years using mesocosms (each consisting of three tanks in series) containing submerged aquatic vegetation (SAV) grown on muck and limerock (LR) substrates. Mean inflow total P concentrations (TP) of 32 μg L⁻¹ were reduced to 15 and 17 μg L⁻¹ in the muck and LR mesocosms, respectively. Mesocosm P loading rates (mean = 1.75 g m⁻² year⁻¹) varied widely during the study and were not correlated with outflow TP, which instead varied seasonally with lowest monthly mean values in December and January.The mesocosms initially were stocked with Najas guadalupensis, Ceratophyllum demersum, and Chara zeylanica, but became dominated by C. zeylanica. At the end of the study, highest vegetative biomass (1.1 and 1.4 kg m⁻² for muck and LR substrates) and tissue P content (1775 and 1160 mg kg⁻¹) occurred in the first tank in series, and lowest biomass (1.0 and 0.2 kg m⁻²) and tissue P (147 and 120 mg kg⁻¹) in the third tank. Sediment accretion rates (2.5, 1.9 and 0.9 cm yr⁻¹ on muck substrates), accrued sediment TP (378, 309 and 272 mg kg⁻¹), and porewater soluble reactive P (SRP) concentrations (40, 6 and 4 μg L⁻¹) in the first, second and third tanks, respectively, exhibited a similar decreasing spatial trend. Plant tissue calcium (Ca) near mesocosm inflow (19-30% dry weight) and outflow (23-26%) were not significantly different, and sediment Ca was also similar (range of 24 to 28%) among sequential tanks.Well-defined vegetation and sediment enrichment gradients developed in SAV wetlands operated under low TP conditions. While the mesocosm data did not reflect deterioration in treatment performance over 6 years, accumulation of P-enriched sediments near the inflow could eventually compromise hydraulic storage and P removal effectiveness of these shallow systems.     

Exposure and cancer risk assessment for formaldehyde and acetaldehyde in the hospitals,Fortaleza-Brazil

The levels of internal and external concentrations of formaldehyde and acetaldehyde, as well as occupational risk based on individual exposure to and potential carcinogenic effects of these, were evaluated in eight environments of two hospitals in the city of Fortaleza-CE during September and October of 2009. The results depicted a variation of 1.98–24.87 μg m⁻³ formaldehyde and of 9.38–55.10 μg m⁻³ acetaldehyde; the main sources of emissions were internal. The exposure levels showed values above the allowable limits for some of the environments studied (permissible exposure limits estimated as an 8-h time-weighted average (PEL-TWA)). The estimation of total cancer risk is of a similar magnitude to other studies, and the risk is 12–18% greater for women than men.     

Sublethal toxicity of commercial insecticide formulations and their active ingredients to larval fathead minnow (Pimephales promelas)

Toxic effect concentrations of insecticides are generally determined using the technical grade or pure active ingredient. Commercial insecticide formulations, however, contain a significant proportion (> 90%) of so-called inert ingredients, which may alter the toxicity of the active ingredient(s). This study compares the sublethal toxicity of two insecticides, the pyrethroid bifenthrin, and the phenylpyrazole fipronil, to their commercial formulations, Talstar® and Termidor®. Both insecticides are used for landscape treatment and structural pest control, and can be transported into surface water bodies via stormwater and irrigation runoff. We used larval fathead minnow (Pimephales promelas), to determine effects on growth and swimming performance after short-term (24 h) exposure to sublethal concentrations of pure insecticides and the respective formulations. Significantly enhanced 7 d growth was observed at 10% of the 24 h LC₁₀ (53 μg L⁻¹) fipronil. Swimming performance was significantly impaired at 20% of the 24 h LC₁₀ (0.14 μg L⁻¹) of bifenthrin and 10% of the 24 h LC₁₀ of Talstar® (0.03 μg L⁻¹). Fipronil and Termidor® led to a significant impairment of swimming performance at 142 μg L⁻¹ and 148 μg L⁻¹ respectively, with more pronounced effects for the formulation. Our data shows that based on dissolved concentrations both formulations were more toxic than the pure active ingredients, suggesting that increased toxicity due to inert ingredients should be considered in risk assessments and regulation of insecticides.     

Changes in water quality of the River Frome (UK) from 1965 to 2009: is phosphorus mitigation finally working?

The water quality of the River Frome, Dorset, southern England, was monitored at weekly intervals from 1965 until 2009. Determinands included phosphorus, nitrogen, silicon, potassium, calcium, sodium, magnesium, pH, alkalinity and temperature. Nitrate-N concentrations increased from an annual average of 2.4 mg l^− 1 in the mid to late 1960s to 6.0 mg l^− 1 in 2008-2009, but the rate of increase was beginning to slow. Annual soluble reactive phosphorus (SRP) concentrations increased from 101 μg l^− 1 in the mid 1960s to a maximum of 190 μg l^− 1 in 1989. In 2002, there was a step reduction in SRP concentration (average = 88 μg l^− 1 in 2002-2005), with further improvement in 2007-2009 (average = 49 μg l^− 1), due to the introduction of phosphorus stripping at sewage treatment works. Phosphorus and nitrate concentrations showed clear annual cycles, related to the timing of inputs from the catchment, and within-stream bioaccumulation and release. Annual depressions in silicon concentration each spring (due to diatom proliferation) reached a maximum between 1980 and 1991, (the period of maximum SRP concentration) indicating that algal biomass had increased within the river. The timing of these silicon depressions was closely related to temperature. Excess carbon dioxide partial pressures (EpCO₂) of 60 times atmospheric CO₂ were also observed through the winter periods from 1980 to 1992, when phosphorus concentration was greatest, indicating very high respiration rates due to microbial decomposition of this enhanced biomass. Declining phosphorus concentrations since 2002 reduced productivity and algal biomass in the summer, and EpCO₂ through the winter, indicating that sewage treatment improvements had improved riverine ecology. Algal blooms were limited by phosphorus, rather than silicon concentration. The value of long-term water quality data sets is discussed. The data from this monitoring programme are made freely available to the wider science community through the CEH data portal (http://gateway.ceh.ac.uk/).     

Emission of trace gases and organic components in smoke particles from a wildfire in a mixed-evergreen forest in Portugal

On May 2009, both the gas and particulate fractions of smoke from a wildfire in Sever do Vouga, central Portugal, were sampled. Total hydrocarbons and carbon oxides (CO₂ and CO) were measured using automatic analysers with flame ionisation and non-dispersive infrared detectors, respectively. Fine (PM_2.5) and coarse (PM_2.5-10) particles from the smoke plume were analysed by a thermal-optical transmission technique to determine the elemental and organic carbon (EC and OC) content. Subsequently, the particle samples were solvent extracted and fractionated by vacuum flash chromatography into different classes of organic compounds. The detailed organic speciation was performed by gas chromatography-mass spectrometry. The CO, CO₂ and total hydrocarbon emission factors (g kg⁻¹ dry fuel) were 170 ± 83, 1485 ± 147, and 9.8 ± 0.90, respectively. It was observed that the particulate matter and OC emissions are significantly enhanced under smouldering fire conditions. The aerosol emissions were dominated by fine particles whose mass was mainly composed of organic constituents, such as degradation products from biopolymers (e.g. levoglucosan from cellulose, methoxyphenols from lignin). The compound classes also included homologous series (n-alkanes, n-alkenes, n-alkanoic acids and n-alkanols), monosaccharide derivatives from cellulose, steroid and terpenoid biomarkers, and polycyclic aromatic hydrocarbons (PAHs). The most abundant PAH was retene. Even carbon number homologs of monoglycerides were identified for the first time as biomarkers in biomass burning aerosols.     

Exposure of children to airborne particulate matter of different size fractions during indoor physical education at school

Although moderate regular aerobic exercise is recommended for good health, adverse health consequences may be incurred by people who exercise in areas with high ambient pollution, such as in the centres of large cities with dense traffic. The exposure of children during exercise is of special concern because of their higher sensitivity to air pollutants. The size-segregated mass concentration of particulate matter was measured in a naturally ventilated elementary school gym during eight campaigns, seven to ten days long, from November 2005 through August 2006 in a central part of Prague (Czech Republic). The air was sampled using a five-stage cascade impactor. The indoor concentrations of PM_2.5 recorded in the gym exceeded the WHO recommended 24-hour limit of 25 μg m⁻³ in 50% of the days measured. The average 24-h concentrations of PM_2.5 (24.03 μg m⁻³) in the studied school room did not differ much from those obtained from the nearest fixed site monitor (25.47 μg m⁻³) and the indoor and ambient concentrations were closely correlated (correlation coefficient 0.91), suggesting a high outdoor-to-indoor penetration rate. The coarse indoor fraction concentration (PM_2.5–10) was associated with the number of exercising pupils (correlation coefficient 0.77), indicating that human activity is its main source. Considering the high pulmonary ventilation rate of exercising children and high outdoor particulate matter concentrations, the levels of both coarse and fine aerosols may represent a potential health risk for sensitive individuals during their physical education performed in naturally ventilated gyms in urban areas with high traffic intensity.     

The distribution of depleted uranium contamination in Colonie, NY, USA

Uranium oxide particles were dispersed into the environment from a factory in Colonie (NY, USA) by prevailing winds during the 1960s and '70s. Uranium concentrations and isotope ratios from bulk soil samples have been accurately measured using inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) without the need for analyte separation chemistry. The natural range of uranium concentrations in the Colonie soils has been estimated as 0.7-2.1 μg g^− 1, with a weighted geometric mean of 1.05 μg g^− 1; the contaminated soil samples comprise uranium up to 500 ± 40 μg g^− 1. A plot of ²³⁶U/²³⁸U against ²³⁵U/²³⁸U isotope ratios describes a mixing line between natural uranium and depleted uranium (DU) in bulk soil samples; scatter from this line can be accounted for by heterogeneity in the DU particulate. The end-member of DU compositions aggregated in these bulk samples comprises (2.05 ± 0.06) × 10^− 3235U/²³⁸U, (3.2 ± 0.1) × 10^− 5236U/²³⁸U, and (7.1 ± 0.3) × 10^− 6234U/²³⁸U. The analytical method is sensitive to as little as 50 ng g^− 1 DU mixed with the natural uranium occurring in these soils. The contamination footprint has been mapped northward from site, and at least one third of the uranium in a soil sample from the surface 5 cm, collected 5.1 km NNW of the site, is DU. The distribution of contamination within the surface soil horizon follows a trend of exponential decrease with depth, which can be approximated by a simple diffusion model. Bioturbation by earthworms can account for dispersal of contaminant from the soil surface, in the form of primary uranium oxide particulates, and uranyl species that are adsorbed to organic matter. Considering this distribution, the total mass of uranium contamination emitted from the factory is estimated to be c. 4.8 tonnes.