Recent trends in chemical composition of bulk precipitation at Estonian monitoring stations 1994–2001

Monthly and annual means of main anions (SO₄²⁻, NO₃⁻, Cl⁻) and summed base cations (Ca²⁺, Mg²⁺, K⁺, Na⁺) in bulk precipitation were studied at 10 stations during an 8-year monitoring period. The data showed statistically significant decreasing trends in most cases. Average declines of mean annual volume-weighted concentrations for both anions and cations were about two-fold. Despite the decrease, the loads of S and cations are still relatively high in Estonia (about 4–14 kg S ha⁻¹ and 0.6–1.2 keq ha⁻¹, respectively) compared with the loads in Finland and Sweden. Estimated linear decline trends followed the same pattern as annually combusted oil shale from Estonian power plants and emissions of SO₂ and fly ash. Recent trends in chemical composition of bulk precipitation at the monitoring stations reflected economic changes in Estonia as well as transboundary fluxes from neighbouring countries.     

A detailed field-based evaluation of naphthenic acid mobility in groundwater

An anaerobic plume of process-affected groundwater was characterized in a shallow sand aquifer adjacent to an oil sands tailings impoundment. Based on biological oxygen demand measurements, the reductive capacity of the plume is considered minimal. Major dissolved components associated with the plume include HCO₃, Na, Cl, SO₄, and naphthenic acids (NAs). Quantitative and qualitative NA analyses were performed on groundwater samples to investigate NA fate and transport in the subsurface. Despite subsurface residence times exceeding 20 years, significant attenuation of NAs by biodegradation was not observed based on screening techniques developed at the time of the investigation. Relative to conservative tracers (i.e., Cl), overall NA attenuation in the subsurface is limited, which is consistent with batch sorption and microcosm studies performed by other authors. Insignificant biological oxygen demand and low concentrations of dissolved As (< 10 µg L^− 1) in the plume suggest that the potential for secondary trace metal release, specifically As, via reductive dissolution reactions driven by ingress of process-affected water is minimal. It is also possible that readily leachable As is not present in significant quantities within the sediments of the study area. Thus, for similar plumes of process-affected groundwater in shallow sand aquifers which may occur as oil sands mining expands, a reasonable expectation is for NA persistence, but minimal trace metal mobilization.     

Nitrate reduction during ground-water recharge, Southern High Plains, Texas

In arid and semi-arid environments, artificial recharge or reuse of wastewater may be desirable for water conservation, but NO₃⁻ contamination of underlying aquifers can result. On the semi-arid Southern High Plains (USA), industrial wastewater, sewage, and feedlot runoff have been retained in dozens of playas, depressions that focus recharge to the regionally important High Plains (Ogallala) aquifer. Analyses of ground water, playa-basin core extracts, and soil gas in an 860-km² area of Texas suggest that reduction during recharge limits NO₃⁻ loading to ground water. Tritium and Cl⁻ concentrations in ground water corroborate prior findings of focused recharge through playas and ditches. Typical δ¹⁵N values in ground water (>12.5‰) and correlations between δ¹⁵N and ln C_NO⁻3–N suggest denitrification, but O₂ concentrations ≥3.24 mg l⁻¹ indicate that NO₃⁻ reduction in ground water is unlikely. The presence of denitrifying and NO₃⁻-respiring bacteria in cores, typical soil–gas δ¹⁵N values <0‰, and decreases in NO₃⁻–N/Cl⁻ and SO₄²⁻/Cl⁻ ratios with depth in cores suggest that reduction occurs in the upper vadose zone beneath playas. Reduction may occur beneath flooded playas or within anaerobic microsites beneath dry playas. However, NO₃⁻–N concentrations in ground water can still exceed drinking-water standards, as observed in the vicinity of one playa that received wastewater. Therefore, continued ground-water monitoring in the vicinity of other such basins is warranted.     

Hydrochemical characteristics and identification of groundwater pollution sources in tropical savanna

Groundwater pollution of the watershed is mainly influenced by the multifaceted interactions of natural and anthropogenic processes. In this study, classic chemical and multivariate statistical methods were utilized to assess the groundwater quality and ascertain the potential contamination sources affecting the groundwater quality of Galma sub-watershed in a tropical savanna. For this purpose, the data set of 18 groundwater quality variables covering 57 different sampling boreholes (BH) was used. The groundwater samples essentially contained the cations in the following order of dominance: Ca²⁺ ?>?Na⁺ ?>?Mg²⁺ ?>?K⁺. However, the anions had HCO₃^–?>?Cl^–?>?SO₄^–2?>?NO₃^– respectively. The hydrochemical facies classified the groundwater types of the sub-watershed into mixed Ca–Mg–Cl type of water, which means no cations and anions exceeds 50%. The second dominant water type was Ca–Cl. The Mg–HCO₃ water type was found in BH 9, and Na–Cl water type in BH 29 of the studied area. The weathering of the basement rocks was responsible for the concentrations of these ions in the groundwater chemistry of the sub-watershed. Hierarchical cluster analysis (HCA) grouped the groundwater samples (boreholes) into five clusters that are statistically significant regarding the similarities of groundwater quality characteristics. The principal component analysis (PCA) extracted two major principal components explained around 65% of the variance and suggested the natural and anthropogenic processes especially the agricultural pollutants including synthetic fertilizers, and leaching of agricultural waste as the main factors affecting the groundwater quality. The integrated method proved to be efficient and robust for groundwater quality evaluation, as it guaranteed the precise assessment of groundwater chemistry in the sub-watershed of the tropical savanna. The findings of this investigation could be useful to the policy makers for developing effective groundwater management plans for the groundwater resources and protection of the sub-watershed.

     

Description and evaluation of a model of deposition velocities for routine estimates of dry deposition over North America. Part II: review of past measurements and model results

Numerical sensitivity tests and four months of complete model runs have been conducted for the Routine Deposition Model (RDM). The influence of individual model inputs on dry deposition velocity as a function of land-use category (LUC) and pollutant (SO₂, O₃, SO²⁻₄ and HNO₃) were examined over a realistic range of values for solar radiation, stability and wind speed. Spatial and temporal variations in RDM deposition velocity (V_d) during June – September 1996 time period generated using meteorological input from a mesoscale model run at 35 km resolution over north-eastern North America were also examined. Comparison of RDM V_d values to a variety of measurements of dry deposition velocities of SO₂, O₃, SO²⁻₄ and NHO₃ that have been reported in the literature demonstrated that RDM produces realistic results. Over northeastern NA RDM monthly averaged dry deposition velocities for SO₂ vary from 0.2 to 3.0 cm s⁻¹ with the highest deposition velocities over water surfaces. For O₃, the monthly averaged dry deposition velocities are from 0.05 to 1.0 cm s⁻¹ with the lowest values over water surfaces and the highest over forested areas. For HNO₃, the monthly averaged dry deposition velocities have the range of 0.5 to 6 cm s⁻¹, with the highest values for forested areas. For SO²⁻₄, they range from 0.05–1.5 cm s⁻¹, with the lowest values over water and the highest over forest. The monthly averaged dry deposition velocities for SO₂ and O₃ are higher in the growing season compared to the fall, but this behaviour is not apparent for HNO₃ and sulphate. In the daytime, the hourly averaged dry deposition velocities for SO₂, O₃, SO²⁻₄ and HNO₃ are higher than that in the nighttime over most of the vegetated area. The diurnal variation is most evident for surfaces with large values for leaf area index (LAI), such as forests. Based on the results presented in this paper, it is concluded that RDM V_d values can be combined with measured air concentrations over hourly, daily or weekly periods to determine dry deposition amounts and with wet deposition measurements to provide seasonal estimates of total deposition and estimates of the relative importance of dry deposition.     

Exposure of acid aerosol for schoolchildren in metropolitan Taipei

Metropolitan Taipei, which is located in the subtropical area, is characterized by high population and automobile densities. For convenience, most primary schools are located near major roads. This study explores the exposure of acid aerosols for schoolchildren in areas in Taipei with different traffic densities. Acid aerosols were collected by using a honeycomb denuder filter pack sampling system (HDS). Experimental results indicated that the air pollutants were significantly correlated with traffic densities. The ambient air NO₂, SO₂, HNO₃, NO₃⁻, SO₄²⁻, and aerosol acidity concentrations were 31.3 ppb, 4.7 ppb, 1.3 ppb, 1.9 μg m⁻³, 18.5 μg m⁻³, and 49.5 nmol m⁻³ in high traffic density areas, and 6.1 ppb, 1.8 ppb, 0.9 ppb, 0.7 μg m⁻³, 8.8 μg m⁻³ and 14.7 nmol m⁻³ in low traffic density areas. The exposure levels of acid aerosols for schoolchildren would be higher than the measurements because the sampling height was 5 m above the ground. The SO₂ levels were low (0.13–8.03 ppb) in the metropolitan Taipei. However, the SO₄²⁻ concentrations were relatively high, and might be attributed to natural emissions of sulfur-rich geothermal sources. The seasonal variations of acid aerosol concentrations were also observed. The high levels of acidic particles in spring time may be attributed to the Asian dust storm and low height of the mixture layer. We conclude that automobile contributed not only the primary pollutants but also the secondary acid aerosols through the photochemical reaction. Schoolchildren were exposed to twice the acid aerosol concentrations in high traffic density areas compared to those in low traffic density areas. The incidence of allergic rhinitis of schoolchildren in the high traffic density areas was the highest in spring time. Accompanied by high temperature variation and high levels of air pollution in spring, the health risk of schoolchildren had been observed.     

Chemical composition of rainwater in the northeastern Romania, Iasi region (2003–2006)

Chemical composition of rainwater was studied in the northeastern Romania, Iasi region, and the concentrations of major inorganic and organic ions were measured in samples collected between April 2003 and December 2006. The pH of the rainwater is 5.92 (volume weighted mean average, VWM) suggesting a sufficient load of alkaline components neutralizing its acidity. On average, 97% of the acidity in the collected samples is neutralized by CaCO₃ and NH₃. Clear seasonal variations were observed for some of the identified ions (e.g., SO₄²⁻, NO₃⁻, Ca²⁺, NH₄⁺). The data obtained during this work revealed that both concentrations and fluxes of anthropogenic source-related ions (e.g., SO₄²⁻, NO₃⁻ and NH₄⁺) are among the highest reported for European sites. It is shown that meteorology and long-range transport processes may concur to their high levels.     

Hydrochemistry of urban groundwater, Seoul, Korea: the impact of subway tunnels on groundwater quality

Hydrogeologic and hydrochemical data for subway tunnel seepage waters in Seoul (Republic of Korea) were examined to understand the effect of underground tunnels on the degradation of urban groundwater. A very large quantity of groundwater (up to 63 million m³ year^− 1) is discharged into subway tunnels with a total length of 287 km, resulting in a significant drop of the local groundwater table and the abandonment of groundwater wells. For the tunnel seepage water samples (n = 72) collected from 43 subway stations, at least one parameter among pathogenic microbes (total coliform, heterotrophic bacteria), dissolved Mn and Fe, NH₄⁺, NO₃⁻, turbidity, and color exceeded the Korean Drinking Water Standards. Locally, tunnel seepage water was enriched in dissolved Mn (avg. 0.70 mg L^− 1, max. 5.58 mg L^− 1), in addition to dissolved Fe, NH₄⁺, and pathogenic microbes, likely due to significant inflow of sewage water from broken or leaking sewer pipes.Geochemical modeling of redox reactions was conducted to simulate the characteristic hydrochemistry of subway tunnel seepage. The results show that variations in the reducing conditions occur in urban groundwater, dependent upon the amount of organic matter-rich municipal sewage contaminating the aquifer. The organic matter facilitates the reduction and dissolution of Mn- and Fe-bearing solids in aquifers and/or tunnel construction materials, resulting in the successive increase of dissolved Mn and Fe. The present study clearly demonstrates that locally significant deterioration of urban groundwater is caused by a series of interlinked hydrogeologic and hydrochemical changes induced by underground tunnels.     

Association of the mutagenicity of airborne particles with the direct emission from combustion processes investigated in Osaka, Japan

The association of the direct-acting mutagenicity of soluble organic fraction of airborne particles toward Salmonella typhimurium YG1024 strain with the direct emission was investigated at a roadside and at a residential area in Osaka, Japan. The direct-acting mutagenicity was evaluated as mutagenic activity per unit volume of ambient air (rev m⁻³) and/or that per airborne particulate weight collected on a filter (rev mg⁻¹). The annual or diurnal changes of the mutagenicity of airborne particles at the residential site showed similar patterns to those of some gaseous pollutants such as NO₂ and SO₂, which were emitted from combustion processes. This result indicates that the mutagenicity is mainly attributable to the primary emissions. From the analysis of the relationship between the wind sector and the mutagenic intensity, rev m⁻³ and rev mg⁻¹ values were strongly affected by the emissions from the fixed sources and from the mobile sources, respectively. The rev m⁻³ value and concentration of 1-nitropyrene (1-NP) in unit per m³ at the roadside were a factor of 2.6 and 2.8 higher than those at the residential site, respectively, but the rev mg⁻¹ value and concentration of 1-NP in unit per mg at the roadside were substantially comparable to those at the residential area. These observations suggest that the characteristics of the airborne particles can be attributed to the automotive emissions even at the suburban area.     

Depleted N carryover, leaching and uptake for three years of irrigated corn

Deep percolation of nitrate can contribute to the deterioration of groundwater resources. Leaching of nitrate is a complex process affected by fertilizer and irrigation practices, efficiency of N use by the crop, and how the soil's water holding capacity and water transmission properties are affected by soil texture. Depleted (¹⁵NH₄)₂SO₄ fertilizer at N rates of 0, 125, 250 and 375 kg ha⁻¹ was applied annually for 3 years to continuous corn grown within three different water regimes. This time period and the labeled N permitted an evaluation of N use efficiency by the crop and NO₃ leaching and carryover on a Weld silty clay loam, a fine-textured soil, typical of the “hardland” soils of the semi-arid Great Plains. Three water regimes, W₁ ( 1.5 ET), W₂ ( ET) and W₃ ( 0.8 ET), were used. Beneath each plot within each water regime, Duke-Haise vacuum trough extractors were installed under undisturbed soil profiles at 1.22-m depth to measure weekly percolate and the NO₃ concentration in the percolate. The corn was harvested in the fall in the dent stage to measure the total above-ground biomass N uptake. Soil profiles (1.8 m) were sampled annually in the fall after crop harvest to determine NO₃---N in the soil or carryover.Great variability was encountered in measuring the amount of extractor water and its NO₃ content under each water regime, which made estimates of N03 leaching losses unreliable. Also, the variability demonstrates formidable problems in quantifying percolation losses with vacuum trough extractors under undisturbed fine-textured soil profiles. With the highest N rate of 376 kg ha⁻¹ yr⁻¹ and within the water regime W₁, where leaching was expected to be greatest, only 1% of the cumulative labeled N applied was found in extractor waters and most movement of the labeled N into extractors occurred the third year. The 125-kg-ha⁻¹ yr⁻¹ fertilizer N rate significantly increased the crop yield over the unfertilized plots without increasing residual NO₃---N accumulation; whereas fertilizer N rates of > 125 kg ha⁻¹ yr⁻¹ did not appreciably increase plant yields over the 125-kg-ha⁻¹-N rate, but did appreciably increase residual NO₃.     

Chemical characteristics of precipitation at metropolitan Newark in the US East Coast

To investigate the chemical characteristics of precipitation in the polluted coastal atmosphere, a total of 46 event-based precipitation samples were collected using a wet-only automatic precipitation collector from September 2006 to October 2007 at metropolitan Newark, New Jersey in the US East Coast. Samples were analyzed by ion chromatography for the concentrations of major inorganic ions (Cl⁻, NO₃⁻, SO₄²⁻, F⁻, NH₄⁺, Ca²⁺, Mg²⁺, Na⁺, K⁺) and organic acid species (CH₃COO⁻, HCOO⁻, CH₂(COO)₂²⁻, C₂O₄²⁻). Selected trace metals (Sb, Pb, Al, V, Fe, Cr, Co, Ni, Cu, Zn, Cd) in samples were determined by ICPMS. Mass concentration results show that SO₄²⁻ was the most dominant anion accounting for 51% of the total anions, controlling the acidity of the precipitation. NH₄⁺ accounted for 48.6% of the total cations, dominating the precipitation neutralization. CH₃COO⁻ and HCOO⁻ were the two dominant water-soluble organic acid species, accounting for 42% and 40% of the total organic acids analyzed, respectively. Al, Zn and Fe were the three major trace metals in precipitation, accounting for 34%, 27%, and 25% of the total mass of metals analyzed. The pH values in precipitation ranged from 4.4 to 4.9, indicating an acidic nature. Enrichment Factor (EF) Analysis showed that Na⁺, Cl⁻, Mg²⁺ and K⁺ in the precipitation were primarily of marine origin, while most of the Fe, Co and Al were from crust sources. Pb, V, Cr, Ni were moderately enriched with EFs ranging 43–410, while Zn, Sb, Cu, Cd and F⁻ were highly enriched with EFs > 700, indicating significant anthropogenic influences. Factor analysis suggests 6 major sources contributing to the observed composition of precipitation at this location: (1) nitrogen-enriched soil, (2) secondary pollution processes, (3) marine sources, (4) incinerations, (5) oil combustions, and (6) malonate–vanadium enriched sources. To further explore the source–precipitation event relationships and seasonality, cluster analysis was performed for all precipitation events. Results show that about half of the precipitation events were characterized by mixed sources. Significant influences of nitrogen-enriched soil and marine sources were associated with precipitation events in spring and autumn, while secondary pollution processes, incineration and oil combustion contributed greatly in summer.     

The contribution of dry deposited ammonia and sulphur dioxide to the composition of precipitation from continuously open gauges

A series of experiments using bulk precipitation collectors of the type used in the UK precipitation chemistry network measured the amounts of NH₄⁺, SO₄²⁻ and other ions that could be washed from funnels (diameter 15 cm) exposed to a wide range of NH₃ and SO₂ concentrations over periods from hours to days. In dry conditions, the average deposition flux of NH₃ was between 50 and 120 nmol NH₄⁺ funnel⁻¹ d⁻¹ (0.1–0.3 kg N ha⁻¹ yr⁻¹), and was independent of the concentration of NH₃. Dry deposition of NH₃ to wet funnels at small NH₃ concentrations was almost 5 times that to dry funnels under the same conditions (average 240 nmol funnel⁻¹ d⁻¹; 0.7 kg ha⁻¹ yr⁻¹), and increased with increasing NH₃ concentrations. The amount of NH₄⁺ ions remaining on the funnel surface was inversely proportional to the vapour pressure deficit during the experiment. This result was interpreted as a dependence on the duration of surface wetness, with greater deposition of NH₄⁺ when evaporation rates of surface water were small.The amount of SO₂ deposited on funnel surfaces was closely related to the amount of NH₃ deposited, in both wet and dry conditions, but was not strongly correlated with the SO₂ concentration. At low NH₃ and SO₂ concentrations the average deposition to dry funnels was 70 nmol SO₄²⁻ funnel⁻¹ d⁻¹ (0.5 kg ha⁻¹ yr⁻¹), and to wet funnels was approximately 2.5 times larger. The results are interpreted in terms of the balance between the rate of evaporation of surface water, and the rate of oxidation of SO₂, which leads to the ‘fixing’ of NH₄⁺ ions on the surface as involatile salts.It is predicted that dry deposition of NH₃ to funnel surfaces across the UK Secondary Network could account for as much as one-half of the measured bulk wet deposition at sites where wet deposition of NH₄–N is small. The amount of dry deposition depends on how long and how often funnel surfaces are wetted by rain or dew, and on the air concentrations of NH₃. These predictions are based on funnels being wetted only once per day. More frequent wetting would increase the contribution from dry deposition, and the consequent overestimate of wet deposition of NH₄–N across the UK by using data obtained from bulk collectors. To some extent this overestimate may be offset by microbial degradation and loss of NH₄–N in weekly bulk precipitation samples during collection and storage.     

Spatial character of polychlorinated biphenyls from soil and respirable particulate matter in Taiyuan, China

As one of China’s great metropolises, Taiyuan is affected by heavy chemical industry and manufacture of chemical products, and faces pollution from polychlorinated biphenyls (PCBs). Therefore, this study was conducted to determine the PCB concentrations in various environmental media in Taiyuan. We collected 15 soil samples, 34 respirable particulate matter (PM) samples (17 of PM_2.5 and 17 of PM₁₀) from urban areas of Taiyuan, and measured a total of 144 PCB congeners (including some coeluting PCB congeners). The total PCB concentrations were 51–4.7 × 10³ pg g⁻¹ in soil, 27–1.4 × 10² pg m⁻³ in PM_2.5 and 16–1.9 × 10² pg m⁻³ in PM₁₀. Of the PCB homologues, the dominant PCBs detected in the various media were all tri-CBs. Soil was relatively the most polluted media. Furthermore, principal-component analysis revealed that the major PCB source in Taiyuan may be associated with the main commercial PCB through long-range transmission. Toxic equivalency (TEQ) concentrations (based on ten dioxin-like PCBs) ranged from N.D. to 5.9 × 10⁻³ pg-WHO TEQ g⁻¹ in soil, 2.0 × 10⁻⁴–3.4 × 10⁻³ pg-WHO TEQ m⁻³ and 1.0 × 10⁻⁴–1.2 × 10⁻³ pg-WHO TEQ m⁻³ in PM_2.5 and PM₁₀, respectively. In previous studies, PCBs were not a severe component of contaminant in Taiyuan; however, this study suggested there is a potential threat of human exposure to PCBs for residents of Taiyuan.     

Contamination in Ontario farmstead domestic wells and its association with agriculture:: 1. Results from drinking water wells

Groundwater provides about 30% of water requirements in Ontario, but farm families depend almost entirely on private wells. Major potential contaminants on farms are nitrate (NO₃⁻), pathogenic microorganisms, pesticides and petroleum derivatives. A survey of farm drinking-water wells was conducted throughout the Province of Ontario, Canada, in 1991 and 1992 and tested for these contaminants. The main objectives of the survey were to determine the quality and safety of drinking water for farm families, and determine the effect of agricultural management on groundwater quality at a provincial scale. Four farm wells were chosen in each township where >50% of the land area was used for agricultural production. Elsewhere one well per township was usually sampled. Within each township the types of farming activity and dominant soils were additional criteria for selection. The network comprised 1292 of the estimated 500,000 water-wells in Ontario, and the study conformed to a stratified random survey. A subset of 160 wells, chosen by farm type, soil, and the presence or absence of a fuel storage tank, was investigated for the presence of petroleum derivatives: benzene, toluene, ethyl benzene, and xylene. About 40% of farm wells tested contained one or more of the target contaminants above the maximum acceptable concentration; 34% of wells had more than the maximum acceptable number of coliform bacteria, 14% contained NO₃⁻-N concentrations above 10 mg l⁻¹ limit and about 7% were contaminated with both bacteria and NO₃⁻. Only six wells contained pesticide residues above the interim maximum acceptable concentration (IMAC), but pesticides were detected in 7% of wells in winter and in 11% in summer. No wells contained detectable petroleum derivatives. These results for NO₃⁻ contamination were not significantly different from those reported for a survey of Ontario wells for the period 1950–1954, but the frequency of contamination by Escherichia coli was greater in the present study. None of the point sources investigated contributed significantly to the NO₃⁻ contamination. The percentage of wells contaminated by coliform bacteria decreased significantly with increasing separation of the well from the feedlot or exercise yard on livestock farms. A full statistical model including the type of well construction, depth, age and soil hydrologic group was developed to describe the frequency of NO₃⁻ contamination.     

Adsorption studies of the herbicide simazine in agricultural soils of the Aconcagua valley, central Chile

Simazine is a s-triazine herbicide that has been applied worldwide for agriculture. This herbicide is the second most commonly detected pesticide in surface and groundwater in the United States, Europe and Australia. In this study, simazine adsorption behaviour was studied in two agricultural soils of the Aconcagua valley, central Chile. The two studied soils were soil A (loam, 8.5% organic matter content) and soil B (clay-loam, 3.5% organic matter content). Three times higher simazine adsorption capacity was observed in soil A (68.03 mg kg⁻¹) compared to soil B (22.03 mg kg⁻¹). The simazine adsorption distribution coefficients (K_d) were 9.32 L kg⁻¹ for soil A and 7.74 L kg⁻¹ for soil B. The simazine adsorption enthalpy in soil A was −21.0 kJ mol⁻¹ while in soil B the adsorption enthalpy value was −11.5 kJ mol⁻¹. These results indicate that simazine adsorption process in these soils is exothermic, governing H bonds the adsorption process of simazine in both the loam and clay-loam soils. These results and the potentiometric profiles of both soils, suggest that simazine adsorption in soil A is mainly governed by simazine–organic matter interactions and in soil B by simazine–clay interactions. The understanding of simazine sorption–desorption processes is essential to determine the pesticide fate and availability in soil for pest control, biodegradation, runoff and leaching.     

Chemical composition of fine particles from incense burning in a large environmental chamber

 This study is aimed to characterize the major chemical compositions of PM_2.5 from incense burning in a large environmental chamber. Chemical analyses, including X-ray fluorescence for elemental species, ion chromatography for water soluble inorganic species (chloride, nitrate, sulfate, sodium, potassium, ammonium) and thermal/optical reflectance analysis for carbon species were carried out for combustion of three incense categories (traditional, aromatic and church incense). The average concentrations from incense burning ranged from 139.8 to 4414.7 μg m⁻³ for organic carbon (OC), and from 22.8 to 74.0 μg m⁻³ for elemental carbon (EC), respectively. The average OC and EC concentrations in PM_2.5 of three incense categories were in the order of church incense>traditional incense>aromatic incense. OC/EC ratios ranged from 7.0 to 39.1 for the traditional incense, with an average of 21.7; from 3.2 to 11.9 for the aromatic incense, with an average of 7.7. The concentrations of Cl⁻, SO₄²⁻, Na⁺ and K⁺ were highly variable. On average, the inorganic ion concentration sequence was traditional incense>church incense>aromatic incense. The profiles for elements were dominated by Na, Cl and K. In general, the major components in PM_2.5 fraction from incense burning are OC (especially OC2, OC3 and OC4), EC and K.     

Do aerosols act as catalysts in the OH radical initiated atmospheric oxidation of volatile organic compounds?

Smog chamber/FTIR techniques were used to study the relative reactivity of OH radicals with methanol, ethanol, phenol, C₂H₄, C₂H₂, and p-xylene in 750 Torr of air diluent at 296±2 K. Experiments were performed with, and without, 500–8000 μg m⁻³ (4000–50 000 μm² cm⁻³ surface area per volume) of NaCl, (NH₄)₂SO₄ or NH₄NO₃ aerosol. In contrast to the recent findings of Oh and Andino (Atmospheric Environment 34 (2000) 2901, 36 (2002) 149; International Journal of Chemical Kinetics 33 (2001) 422) there was no discernable effect of aerosol on the rate of loss of the organic compounds via reaction with OH radicals. Gas kinetic theory arguments cast doubt upon the findings of Oh and Andino. The available data suggest that the answer to the title question is “No”. As part of this work the rate constants for reactions of OH radicals with methanol, ethanol, and phenol in 750 Torr of air at 296 K were determined to be: k_OH+CH3OH=(8.12±0.54)×10⁻¹³, k_OH+C2H5OH=(3.47±0.32)×10⁻¹² and k_OH+phenol=(3.27±0.31)×10⁻¹¹ cm³ molecule⁻¹ s⁻¹.     

Atmospheric deposition and canopy exchange processes in alpine forest ecosystems (northern Italy)

Throughfall and bulk precipitation chemistry were studied for five years (June 1994–May 1999) at two high elevation forest sites (Val Gerola and Val Masino) which were known to differ in terms of tree health, as assessed by live crown condition. The ion concentration of bulk precipitation samples did not differ significantly between sites, except for Mg²⁺, while the throughfall concentrations differed in the measured values of H⁺, N-NO₃⁻, Cl⁻, Na⁺, K⁺, DOC and weak organic acids. The results of the application of the canopy exchange model indicated a higher contribution from the dry deposition of N-NO₃⁻, N-NH₄⁺ and H⁺ at Val Gerola, where the damage symptoms were more evident. In addition, the canopy leaching of Ca²⁺, K⁺ and weak organic acids were 47%, 21% and 27% higher at Val Gerola than at Val Masino. Annual SO₄²⁻ deposition fluxes (21.3 kg ha⁻¹ yr⁻¹ at Val Masino and 23.6 kg ha⁻¹ yr⁻¹ at Val Gerola) were similar to those reported for moderately polluted European and U.S. sites. Annual N loads were 13.6 and 13.1 kg ha⁻¹ yr⁻¹ in the bulk input, and 15.0 and 18.0 kg ha⁻¹ yr⁻¹ in throughfall inputs, at Val Masino and Val Gerola, respectively. The contribution of the organic fraction to the total N atmospheric deposition load is significant, constituting 17% of the bulk flux and 40% of the throughfall flux. Measured nitrogen loads exceed the critical nutrient loads by several kg N ha⁻¹ at both stations. In particular the nitrogen throughfall load at Val Gerola was about 3 times higher than the critical values.     

Diffusion of HTO, Cl and I in Opalinus Clay samples from Mont Terri: Effect of confining pressure

Diffusion coefficients (T=23±2 °C) and accessible porosities for HTO, ³⁶Cl⁻ and ¹²⁵I⁻ were measured on Opalinus Clay (OPA) samples from the Mont Terri Underground Rock Laboratory (URL) using the through-diffusion technique. The direction of transport (diffusion) was perpendicular to bedding. Special cells that allowed the application of confining pressure were designed and constructed. The pressures ranged from 1 to 5 MPa, the latter value simulating the overburden at the Mont Terri URL (about 200 m). The test solution used in the experiments was a synthetic version of the Opalinus Clay pore water, which has Na⁺ and Cl⁻ as the main components (I=0.42 M).The measured values of the effective diffusion coefficients (D_e) and rock capacity factors (α) are: D_e=1.2–1.5×10⁻¹¹ m² s⁻¹ and α=0.09–0.11 for HTO, D_e=4.0–5.5×10⁻¹² m² s⁻¹ and α=0.05 for ³⁶Cl⁻ and D_e=3.2–4.6×10⁻¹² m² s⁻¹ and α=0.07–0.10 for ¹²⁵I⁻. For non-sorbing tracers (HTO, ³⁶Cl) the rock capacity factor α is equal to the diffusion-accessible porosity . The experimental results showed that pressure only had a small effect on the value of the diffusion coefficients. Increasing the pressure from 1 to 5 MPa resulted in a decrease of the diffusion coefficient of 17% for HTO, 28% for ³⁶Cl⁻ and 30% for ¹²⁵I⁻. Moreover, the diffusion coefficients for ³⁶Cl⁻ and ¹²⁵I⁻ are smaller than for HTO, which is consistent with an effect arising from anion exclusion.The diffusion coefficients of HTO and ¹²⁵I⁻ measured in this study are in good agreement with recent measurements at three other laboratories performed within the framework of a laboratory comparison exercise. The values of the diffusion-accessible porosities show a larger degree of scatter.     

Quality of roof runoff waters from an urban region (Gda sk, Poland)

The paper presents the results of testing of roof runoff waters from buildings in the city of Gda sk (Poland), carried out as a part of a broader research project aimed at the determination of pollutant levels in precipitation. The analytes determined included volatile organohalogen compounds, petroleum hydrocarbons, Na⁺, K⁺, NH₄⁺, Mg²⁺, Ca²⁺, F⁻, Cl⁻, NO₂⁻, NO₃⁻, PO₄³⁻, SO₄²⁻ ions, as well as organonitrogen, organophosphorus and organochlorine pesticides. In addition, the toxicity and pH of the samples were examined. The samples were collected over a period of six months, during or immediately following precipitation events. More than half of the samples (25) were found to be toxic, with inhibition exceeding 20%. The toxicity was weakly correlated to the levels of organonitrogen and organophosphorus pesticides in runoff waters. It was established that at least in some cases the roofing material affected the levels of the pollutants found in the samples.