Abstract  The abundant lignocellulosic agricultural waste, coir pith is used to develop ZnCl(2) activated carbon and applied to the removal of toxic anions, heavy metals, organic compounds and dyes from water. Sorption of inorganic anions such as nitrate, thiocyanate, selenite, chromium(VI), vanadium(V), sulfate, molybdate, phosphate and heavy metals such as nickel(II) and mercury(II) has been studied. Removal of organics such as resorcinol, 4-nitrophenol, catechol, bisphenol A, 2-aminophenol, quinol, O-cresol, phenol and 2-chlorophenol has also been investigated. Uptake of acidic dyes such as acid brilliant blue, acid violet, basic dyes such as methylene blue, rhodamine B, direct dyes such as direct red 12B, congo red and reactive dyes such as procion red, procion orange were also examined to assess the possible use of the adsorbent for the treatment of contaminated ground water. Favorable conditions for maximum removal of all adsorbates at the adsorbate concentration of 20 mg/L were used. Results show that ZnCl(2) activated coir pith carbon is effective for the removal of toxic pollutants from water.

Abstract  As evidenced by the recent report of the Commission of the European Communities (CEEC) project (Detection of Aneugenic Chemicals-CEEC project, 1993), there currently is a great deal of effort towards developing and validating assays to detect aneuploidy-inducing chemicals. In this report, we describe the utility of the Syrian hamster embryo (SHE) cell transformation assay for detecting carcinogens with known or suspected aneuploidy-inducing activity. The following carcinogens were tested: asbestos, benomyl, cadmium chloride, chloral hydrate, diethylstilbestrol dipropionate, and griseofulvin. Thiabendazole, a noncarcinogen, was also tested. Chemicals of unknown or inconclusive carcinogenicity data, colcemid, diazepam, econazole nitrate, and pyrimethamine were also evaluated. All of the above chemicals except thiabendazole induced a significant increase in morphological transformation (MT) in SHE cells. Based on these results as well as those published in the literature previously, the SHE cell transformation assay appears to have utility for detecting carcinogens with known or suspected aneuploidy-inducing ability.

Abstract  [ 1] We have constructed a pulsed cavity ring-down spectrometer ( CARDS) for simultaneous measurements of nitrogen dioxide (NO2), the nitrate radical (NO3), and dinitrogen pentoxide (N2O5) in the atmosphere. In this paper, we describe the development of the instrument to measure NO2 via its absorption at 532 nm. The NO2 detection channel was calibrated against a NIST traceable calibration standard as well as a photolysis-chemiluminescence (P-CL) NO2 detector. The absorption cross section of NO2 at 532 nm was determined to be (1.45 +/- 0.06) x 10(-19) cm(2). The NO2 detection limit (1 sigma) for 1 s data is 40 pptv, and the instrument response is accurate within +/- 4% (1 sigma) under laboratory conditions. The linear dynamic range of the instrument has been verified from the detection limit to above 200 ppbv (r(2) > 99.99%). For field measurements it is necessary to correct the CARDS NO2 signal for absorption by ozone. Under ambient conditions we report 1 s NO2 CARDS data with total uncertainty +/-(4%, 60 pptv + 0.4 x (pptv/ppbv) x O-3) (1 sigma). The instrument was deployed in the field during the New England Air Quality Study - International Transport and Chemical Transformation on board the NOAA research vessel Ronald H. Brown in the summer of 2004 and in Boulder, Colorado, in the winter of 2005. In both campaigns, CARDS and P-CL NO2 measurements were highly correlated (r(2) > 98%), indicating the absence of interfering gas phase absorbers at 532 nm other than ozone and the suitability of CARDS to measure NO2 in the troposphere.

Abstract  In Arabidopsis thaliana, a family of six genes encodes acyl-CoA-binding proteins (ACBPs) that show conservation at the acyl-CoA-binding domain. They are the membrane-associated ACBP1 and ACBP2, extracellularly targeted ACBP3, kelch-motif-containing ACBP4 and ACBP5, and 10-kDa ACBP6. The acyl-CoA domain in each of ACBP1 to ACBP6 binds long-chain acyl-CoA esters in vitro, suggestive of possible roles in plant lipid metabolism. We addressed here the use of Arabidopsis ACBPs in conferring lead [Pb(II)] tolerance in transgenic plants because the 10-kDa human ACBP has been identified as a molecular target for Pb(II) in vivo. We investigated the effect of Pb(II) stress on the expression of genes encoding Arabidopsis ACBP1, ACBP2 and ACBP6. We showed that the expression of ACBP1 and ACBP2, but not ACBP6, in root is induced by Pb(II) nitrate treatment. In vitro Pb(II)-binding assays indicated that ACBP1 binds Pb(II) comparatively better, and ACBP1 was therefore selected for further investigations. When grown on Pb(II)-containing medium, transgenic Arabidopsis lines overexpressing ACBP1 were more tolerant to Pb(II)-induced stress than the wild type. Accumulation of Pb(II) in shoots of the ACBP1-overepxressing plants was significantly higher than wild type. The acbp1 mutant showed enhanced sensitivity to Pb(II) when germinated and grown in the presence of Pb(II) nitrate and tolerance was restored upon complementation using an ACBP1 cDNA. Our results suggest that ACBP1 is involved in mediating Pb(II) tolerance in Arabidopsis with accumulation of Pb(II) in shoots. Such observations of Pb(II) accumulation, rather than Pb(II) extrusion, in the ACBP1-overexpressing plants implicate possible use of ACBP1 in Pb(II) phytoremediation.

Abstract  Abstract: The Barton reaction (nitrite photolysis) of a steroidal substrate 1, to give 2, a key intermediate for the synthesis of myriceric acid A, an endothelin receptor antagonist, was successfully carried out in a continuous microflow system using a Pyrex glass-covered stainless-steel microreactor having a one lane microchannel (Type A: 1000μm width, 107μm depth, 2.2m length). We found that using a low-power black light (peak wavelength: 352nm) and UV-LED light (peak wavelength: 365nm) as the light source will suffice for the Barton reaction, creating a compact energy-saving photo-microreaction system. A multi-gram-scale production was attained using a multi-lane microreactor (Type B: 1000μm width, 500μm depth, 0.5m length, 16 lanes) in conjunction with a black light. [Copyright 2009 Elsevier] Copyright of Tetrahedron is the property of Pergamon Press - An Imprint of Elsevier Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts)

Abstract  Third-phase formation in the extraction of Th(IV) by trialkyl phosphates (TalP) such as tri-n-butyl phosphate (TBP), tri-iso-butyl phosphate (TiBP), tri-sec-butyl phosphate (TsBP), tri-n-amyl phosphate (TAP), tri-2-methylbutyl phosphate (T2MBP), tri-iso-amyl phosphate (TiAP), tri-sec-amyl phosphate (TsAP), and tri-cyclo-amyl phosphate (TcyAP) has been investigated under various conditions. Formation of a third phase in the extraction of Th(IV) by TBP/n-dodecane as a function of TBP concentration at 303K was studied. Measurements were also carried out on the extraction of Th(IV) from its solution with near-zero free acidity by various phosphate/diluent binary solutions (1.1M) as a function of temperature. Third-phase formation in the extraction of Th(IV) by 1.1M TalP in various diluents from nitric acid media has also been studied as a function of equilibrium aqueous-phase acidity at 303K. Empirical equations to predict limiting organic concentration with respect to various parameters for third-phase formation in the extraction of Th(IV) by TBP and TAP from nitric acid media have been derived. Some of the above phosphates have been investigated for the distribution of Th (NO3)4 between the diluent-rich phase (DP) and third-phase (TP) in the extraction of Th(IV) by 1.1M TalP in various diluents from its saturated solution with near-zero free acidity at 303K. Results of the above studies are presented in this paper. Based on these studies, the effects of extractant concentration, the temperature, the nature of the diluent, the equilibrium aqueous- phase acidity, and the structure of the extractant on third-phase formation behavior of trialkyl phosphates are described in this paper.

Abstract  The Kety-Schmidt method is the reference method for measuring global cerebral blood flow (CBF), cerebral metabolic rates (CMR) and flux, especially where scanners are unavailable or impractical. Our primary objective was to assess the repeatability of the Kety-Schmidt method in a variety of different approaches using inhaled nitrous oxide (N2O) as the tracer, combined with photoacoustic spectrometry. A secondary objective was to assess the impact of this tracer on the systemic vascular concentration of nitrite (NO2-). Twenty-nine healthy male volunteers underwent 61 CBF measurements by breathing a normoxic gas mixture containing 5% N2O until tension equilibrium. Paired blood samples were collected from an arterial and a jugular bulb catheter in the saturation or desaturation phase, by continuous or the discontinuous sampling. N2O concentration was measured with photoacoustic spectrometry after equilibration of blood samples with air. CBF was calculated by the Kety-Schmidt equation. CMR of oxygen (CMRO2) was determined by the Fick principle. NO2- in plasma and red blood cells (RBC) was measured by ozone-based chemiluminescence. The most robust approach for CBF measurement was achieved by discontinuous sampling in the desaturation phase [CBF, 64 (95% confidence interval, 59-71 ml)] 100 g/min; CMRO2 1.8 (1.7-2.0) mu mol/g/min). The tracer did not influence plasma or RBC NO2- (P > 0.05 vs. baseline). These findings confirm the reliability and robustness of the Kety-Schmidt method using inhaled N2O for the measurement of global CBF and CMR. At the low tracer concentration used, altered NO metabolism is unlikely to have affected cerebral haemodynamic function.

Abstract  Various astrophysical events have been suggested as sources of ionizing radiation that, by way of destruction of the ozone layer and the subsequent increase in UVB and deposition of nitrate, could pose a threat to life on Earth. We have investigated whether the nitrate deposition that follows an ionizing event is sufficient to cause an additional stress beyond that of the heightened UVB previously considered. Our results show that, subsequent to the most intense ionization event likely to have occurred in the last billion years, the increase in nitrate concentration in bodies of water would not be sufficient to cause serious additional stress on amphibian populations and may actually provide some benefit by acting as fertilizer.

Abstract  Objectives. To measure eye blink frequency as a measure of trigeminal stimulation of the eye. Human subjects were exposed to oxidation mixtures representative of reactive indoor pollutants and clean air, from which relative changes in blink frequencies were measured. Method. Male subjects (n=8) were exposed for 20 min to limonene oxidation products (LOPs), isoprene oxidation products (IOPs), nitrate radicals (NO3), their residual reactants, and clean air at 20% relative humidity. A baseline blink frequency was measured prior to and following each exposure (2x8 min). The subjects were exposed locally in the non-dominant eye and single blind in random order. Blinking was video-recorded and evaluated for full sessions of 36 min while the subjects viewed an educational film. The initial terpene concentrations were one to two orders of magnitude higher than mean indoor concentrations. Results. The mean blink frequency increased significantly during subjects' exposure to gas-phase oxidation products at lower part-per-billion (ppb) levels of LOPs, 42% (P<0.0001) and NO3, 21% (P<0.022), compared with that at baseline. Neither the residual reactants nor clean air changed the blink frequency significantly. The findings coincided with qualitative reporting of weak eye irritation symptoms. Conclusions. Changes in blink frequency appear to be a promising measure of trigeminal stimulation from exposure to eye irritants in ppb levels. Gaseous products of limonene and ozone, and reactive radicals may cause eye irritation indoors.

Abstract  An analysis of clinical manifestations and emergency treatment of 144 cases of acute acrylonitrile (ACN) poisoning is reported in this article. It is suggested that the acute poisoning induced by inhalation of ACN at high concentrations for a short duration primarily impairs the central nervous system (CNS), and inhalation of ACN at medium concentrations but for a longer period leads to damage to the liver tissues besides the CNS. In severely poisoned victims, the cardiac muscles may be damaged and in the blood levels glutathione (GSH) is decreased. The rational administration of antidotes including the methemoglobin-producing agent (MHbPA), and the sulfur-providing agent (SPA) is the key to the success of emergency treatment and thus the early recovery of the victims.

Abstract  We present the Chemistry of Atmosphere-Forest Exchange (CAFE) model, a vertically-resolved 1-D chemical transport model designed to probe the details of near-surface reactive gas exchange. CAFE integrates all key processes, including turbulent diffusion, emission, deposition and chemistry, throughout the forest canopy and mixed layer. CAFE utilizes the Master Chemical Mechanism (MCM) and is the first model of its kind to incorporate a suite of reactions for the oxidation of monoterpenes and sesquiterpenes, providing a more comprehensive description of the oxidative chemistry occurring within and above the forest. We use CAFE to simulate a young Ponderosa pine forest in the Sierra Nevada, CA. Utilizing meteorological constraints from the BEARPEX-2007 field campaign, we assess the sensitivity of modeled fluxes to parameterizations of diffusion, laminar sublayer resistance and radiation extinction. To characterize the general chemical environment of this forest, we also present modeled mixing ratio profiles of biogenic hydrocarbons, hydrogen oxides and reactive nitrogen. The vertical profiles of these species demonstrate a range of structures and gradients that reflect the interplay of physical and chemical processes within the forest canopy, which can influence net exchange.

Abstract  Background: A growing body of research suggests that prenatal exposure to air pollution may be harmful to fetal development. We assessed the association between exposure to air pollution during pregnancy and anthropometric measures at birth in four areas within the Spanish Children's Health and Environment (INMA) mother and child cohort study. Methods: Exposure to ambient nitrogen dioxide (NO2) and benzene was estimated for the residence of each woman (n = 2,337) for each trimester and for the entire pregnancy. Outcomes included birth weight, length, and head circumference. The association between residential outdoor air pollution exposure and birth outcomes was assessed with linear regression models controlled for potential confounders. We also performed sensitivity analyses for the subset of women who spent more time at home during pregnancy. Finally, we performed a combined analysis with meta-analysis techniques. Results: In the combined analysis, an increase of 10 µg/m3 in NO2 exposure during pregnancy was associated with a decrease in birth length of -0.9 mm [95% confidence interval (CI), -1.8 to -0.1 mm]. For the subset of women who spent ≥ 15 hr/day at home, the association was stronger (-0.16 mm; 95% CI, -0.27 to -0.04). For this same subset of women, a reduction of 22 g in birth weight was associated with each 10-µg/m3 increase in NO2 exposure in the second trimester (95% CI, -45.3 to 1.9). We observed no significant relationship between benzene levels and birth outcomes. Conclusions: NO2 exposure was associated with reductions in both length and weight at birth. This association was clearer for the subset of women who spent more time at home.

Abstract  Two novel facultatively anaerobic bacterial strains, BL-34(T) and BL-35, isolated from groundwater contaminated by a mixture of chlorosolvents were characterized using a polyphasic approach. The two strains exhibited essentially identical taxonomic features except for a vitamin B(12) requirement by strain BL-35 for optimal growth. Phylogenetically, the isolates were affiliated with members of the family Propionibacteriaceae and were placed in a phylogenetic branch adjacent to, but distinct from, those of the genera Propionimicrobium, Propionibacterium, Luteococcus, Propioniferax and Tessaracoccus. The cells of the novel strains were Gram-positive, non-motile, non-spore-forming pleomorphic rods. They produced catalase but not oxidase, and nitrate reduction did not occur in peptone/yeast extract/glucose medium. Propionate and acetate were the predominant products of glucose fermentation. Fermentation occurred in the presence of 1,2-dichloroethane and 1,1,2-trichloroethane at concentrations up to at least 9.8 mM. The genomic DNA G+C content was 67.5-67.9 mol%. Menaquinone MK-9(H(4)) was the predominant respiratory quinone and meso-diaminopimelic acid was present in the cell-wall peptidoglycan layer. The major cellular fatty acids were C(15 : 0) and anteiso-C(15 : 0). On the basis of the results obtained in this study, strains BL-34(T) and BL-35 should be classified within a novel taxon, for which the name Brooklawnia cerclae gen. nov., sp. nov. is proposed. The type strain of Brooklawnia cerclae is BL-34(T) (=LMG 23248(T)=NRRL B-41418(T)). An additional strain, BL-35 (=LMG 23249=NRRL B-41419), was also characterized.

Abstract  A small monomictic, volcanic lake, Lago di Vico in Central Italy, was studied intensively for one calendar year 1992–1993 for its water quality and phytoplankton. The results were compared with those obtained 20 years before. A significant increase in nutrients such as orthophosphates and nitrates was found to have taken place during 1971–1991. Also, eutrification can be seen by the appearance of several algal species characterizing the present mesotrophic stage of the lake, while in 1971 it was classified as an oligotrophic lake.

Abstract  Biotreatment experiments with solutions of autoxidized phenolic compounds as well as coal-conversion wastewater stored for 30 years and rich in humic matter were performed under nitrate-reducing, sulphate-reducing and methanogenic conditions. The removal of total organic carbon in fractions of different molecular mass and of monomeric phenolic compounds in the wastewater was determined. A comparison of biotransformation potentials and rates indicated a relationship between these aspects and the availability of electron acceptors in the system. The capacities of the microbial consortia increased significantly with the energy microorganisms could gain from their respective respiration process and can be expressed by the order: aerobic process - nitrate reduction - sulphate reduction - methanogenesis.

Abstract  This study was conducted to assess availability, phytotoxicity and bioaccumulation of lead (Pb) to ryegrass (Lolium perenne L.) and millet (Echinochloa crusgalli) based on the 0.1 mol/L Ca(NO3), extraction. Effect of soil properties on availability, phytotoxicity and bioaccumulation of Pb to the two plants was also evaluated. Five soils with pH values varying from 3.8 to 7.3, organic carbon (OC) contents from 0.7% to 2.4%, and clay contents from 11.6% to 35.6% were selected. Soils were spiked with Pb to achieve a range of concentrations: 250, 500, 1000, 3000 and 5000 mg/kg. Pb availability in the spiked soils was estimated by extracting soil with 0.1 mol/L Ca(NO3)2. The results indicate that plants yield decreased with decreasing soil pH and increased with increasing soil clay and OC content. Negative relationship between available Pb and the relative dry matter growth (RDMG) of the two plants were significantly related. Available Pb used to assess EC20 (20% effective concentration) and EC50 (50% effective concentration) of millet was 119 and 300 mg/kg, respectively. Available Pb used to assess EC20 and ECs, of ryegrass was 63 and 157 mg/kg, respectively. Bioaccumulation, expressed as bioconcentration factors of Pb, was inversely related to soil pH, soil OC and clay content. Strong relationships were found between available lead and uptake by the two plants (i was 0.92 and 0.95 respectively). In general, 0.1 mol/L Ca(NO3)2 available Pb may be used to assess the availability, phytotoxicity and bioaccumulation of lead to the two plants tested.

Abstract  A novel family of electrochemical anion sensors operating in aqueous media, based on the heterometallic Au(I)-Cu(I) [{Au(3)Cu(2)(C(2)R)(6)}Au(3)(PPh(2)C(6)H(4)PPh(2))(3)](PF(6))(2) (L1, R = Fc; L2, R = C(6)H(4)Fc) alkynyl cluster complexes, is presented. Upon attachment to graphite and gold electrodes, these compounds exhibit a well-defined, essentially reversible, solid-state electrochemistry in contact with aqueous media, based on ferrocenyl-centered oxidation processes involving anion insertion, leading to distinctive pH-independent electrochemical responses for fluoride, chloride, bromide, perchlorate, bicarbonate, carbonate, phosphate, hydrogen phosphate, dihydrogen phosphate, and nitrate anions. Cluster-modified electrodes can be used as potentiometric sensors as a result of the reversible, diffusion-controlled electrochemistry obtained for the anion-assisted electrochemical oxidation of L1 and L2.

Abstract  Fifteen milk processing plants in the Upper Midwest of the United States participated in a study to obtain information on general process operation, waste generation and treatment practices, chemical usage, and wastewater characteristics. Long term data on wastewater characteristics were obtained for 8 of the 15 dairy plants, and a 24-h composite wastewater sample was characterized in detail for each plant. Wastewater flow rates and characteristics varied greatly among and within plants and were not easily predictable even when detailed information on processing operations was available. In addition, the contribution of milk and milk products to the waste streams was underestimated by plant operators. The use of caustic soda, phosphoric acid, and nitric acid for cleaning had a significant impact on wastewater characteristics, despite the implementation of changes in chemical usage practices during recent years. In particular, the use of phosphoric acid based cleaning pr

Abstract  BIOSIS COPYRIGHT: BIOL ABS. The transformability of trihalomethanes, carbon tetrachloride, 1,1,1-trichloroethane, 1,2-dibromomethane, tetrachloroethylene, dibromochloropropane, and chlorinated benzenes was evaluated by a biofilm utilizing a mixture of primary electron acceptors (oxygen, nitrate, and sulfate). These compounds at concentrations commonly found in groundwater were continuously administered for 4 years to a biofilm column reactor that resembled polluted groundwater environments. Acetate was the primary substrate to support microbial growth. Sequential biofilm zones of aerobic respiration, denitrification, and sulfate reduction developed within the column. Transformation of the halogenated aliphatic compounds coincided with the onset of sulfate reduction in the column. The temporary absence of nitrate and sulfate in the column feed decreased the steady-state removals for several of the halogenated aliphatic compounds. These results suggest that sulfate was an important primary electron

Abstract  DEREK is a knowledge-based expert system for the qualitative prediction of toxicity. The DEREK system has been used to predict the carcinogenicity in rodents of the 30 chemicals in the second National Toxicology Program (NTP) carcinogenicity prediction exercise. Seven of the chemicals were predicted to be carcinogens. For 23 chemicals, there was no evidence in the DEREK knowledge base to suggest carcinogenic activity. Supplementary data from a variety of sources have been evaluated by human experts to assess confidence in each DEREK prediction. These sources included standard toxicology reference texts, genotoxicity and subchronic toxicity assay results for each chemical, as well as Salmonella mutagenicity and carcinogenicity data for close structural analogues. This process has led to the proposal of a number of improvements to the DEREK carcinogenicity knowledge base.

Abstract  Using a flow tube reactor coupled to a chemical ionization mass spectrometer, the Cl-initiated oxidation of solid and supercooled liquid brassidic acid (BA, trans-13-docosenoic acid) particles was investigated in the presence of NO and NO2. For the first time, organic nitrate formation from the heterogeneous oxidation of model organic aerosols in the presence of NO was observed, but none was formed by the addition of up to 600 ppb of NO2. Also, no nitrate formation was observed in liquid particles, but the nitrate yields in the solid particles were measured to be as large as 6% with a negative temperature dependence over the range 259-293 K. The corresponding effective activation energy of -7.5 (+/-4.4) kJ mol(-1) suggests that the mechanism of particulate organic nitrate formation is analogous to the termolecular gas-phase reaction of . The yields are smaller than those from analogous gas-phase reactions, but this may result from photodissociation of the nitrate by the UV (355 nm) laser for which there is indirect evidence. Additionally, enhanced rates of the RO2+RO2 reactions in the condensed phase could lead to smaller nitrate yields. The results suggest that slower diffusion of the RO2 radicals in the solid particles compared to the liquid particles makes the RO2+NO reaction competitive with the RO2+RO2 reactions and results in nitrate formation near the surface of the particle. The organic nitrates formed in these experiments are observed intact after the reacted particles have been vaporized at temperatures up to 380 degrees C suggesting that they are thermally stable in the troposphere and may enable long-range transport of NOx if they photodissociate on the timescale of days. The findings from these experiments are not specific to unsaturated carboxylic acids but should apply to nearly all particulate hydrocarbons, and they indicate that the particle phase could be important in determining how organic aerosols evolve chemically through radical-initiated oxidation in polluted atmospheres.

Abstract  Ion concentrations of NO3- and SO42- in individual rains were observed at Nagagute in the suburbs of Nagoya, Japan, from July 1, 1991 to June 30, 1992. Decreasing concentrations of NO3- and SO42- in rainwater collected during precipitation were frequently observed and this decreasing pattern is expressed by exponential functions. The ion concentration decrease is more influenced by the ion scavenging loss in the precipitation area than the ion supply due to transportation and oxidation processes. Under calm atmospheric conditions, the empirical ion scavenging coefficients were derived from changes in ion concentration in a drizzling rain with a rain intensity of below 15 mm h(-1). These coefficients were linearly proportional to the rain intensity. The average empirical scavenging coefficients of NO3- and SO42- were 5.2 X 10(-4) and 2.2 x 10(-4) s(-1) respectively. The coefficient of NO3- is 2.5 times more sensitive to the rain intensity than that of SO42-. The NO3- and SO42- concentrations and pH were well simulated in a numerical model containing the obtained empirical scavenging coefficients. (C) 1997 EIsevier Science B.V.

Abstract  Tropical weather events can contribute large wet depositional fluxes of biogeochemically important rainwater constituents over relatively short time periods. One composite sample during these events does not capture the dynamic nature of rainwater composition and can lead to misinterpretation of the impact of tropical events on local aquatic systems. Eight sequential samples were collected at 2–3 h intervals in Wilmington, NC during the duration of tropical storm Ernesto to examine a suite of rainwater constituents influenced by gas phase, aerosol, or mixed sources in the atmosphere. Real time wind speed and air mass back trajectories were used to examine the progression of the storm. Hydrogen peroxide and nitrate displayed washout trends during the storm. Dissolved organic carbon (DOC), hydrogen ion (H+), and total mercury (HgT) displayed washout at the beginning of the storm but toward the end of the storm concentrations increased, which corresponded to a shift in air masses from marine to terrestrial, increased ground air mass influence, and increased wind speeds. Integrated fluorescence, a measure of the chromophoric properties of the DOC, was highest at the beginning of the storm and than decreased but unlike DOC, the fluorescence did not increase at the end of the storm, indicating a change in the DOC source and composition during the storm. Chloride and sulfate, which are strongly influenced by seasalt aerosols, increased with increasing wind speeds. Factors such as wind speed, storm trajectory, and rainwater volume influenced rainwater constituent concentrations; the relative importance of these factors was a function of the sources of these rainwater constituents in rainwater.

Abstract  A spruce-fir forest in central-Maine, USA, has been the site of dry and wet atmospheric deposition measurements since 1988. Precipitation flux of hydrogen ions (H+) and sulfate (SO42-) decreased by 24 and 42%, respectively, during the study period, but no temporal trends occurred for precipitation H+ or SO(4)2- concentrations. Decreased precipitation fluxes were likely due to a 33% decrease in precipitation amounts during the latter years of the study. Both H+ and SO42- concentrations and fluxes in throughfall decreased, corresponding to decreases in dry deposition of those constituents. No nitrate (NO3-) concentration or flux trends occurred in precipitation, throughfall, or dry deposition. Hydrogen, NO3-, and NH4+ had a negative net canopy exchange (NCE) attributable to N deficiency at this site and acid neutralization in the canopy. Sulfate and magnesium (Mg2+) were conservative and had no NCE. Calcium (Ca2+) and potassium (K+) had a positive NCE due to canopy leaching. A comparison of bulk and wet-only precipitation collectors showed that SO42-, Ca2+, and K+ concentrations were greater in solutions from a bulk collector compared with a wet-only collector. The differences were partially attributable to dry deposition. Throughfall H+, Ca2+, and dissolved organic carbon (DOC) concentrations were higher in weekly wet-only collections composited monthly, compared with weekly bulk collections composited either weekly or monthly. Nitrate concentration, however, was lowest in the wet-only thronghfall collections. Differences likely resulted from spatial variability. Ongoing research is attempting to further define trends apparent to date, and to determine the mechanisms controlling these characteristics.