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Soil fertility diagnosis often omits subsoil measurements, impacting precision. Our objective was to compare the vertical distribution of nitrate and sulfate in agricultural Mollisols. Both anions were measured in 34 Mollisols of the Pampean region (Argentina) sampled to 160‐cm depth at 20 cm intervals. Nitrate exhibited a continuous downward trajectory, with maximum values at 0–20 cm (12.7 mg N kg−1) and minimum values at 140–160 cm (3.3 mg N kg−1). Sulfate displayed a sinuous pattern, with a minimum at 60–80 cm (3 mg S kg−1). The 60–160/0–160 cm concentration ratio was 42% for nitrate and 60% for sulfate, indicating greater topsoil stratification for nitrate. Predicting deep‐layer nitrate concentrations from topsoil data was more accurate than for sulfate. This poses a challenge for assessing soil S bioavailability, as subsoil sulfates go undetected in conventional sampling. Core Ideas: Nitrate content consistently decreased from the shallowest to the deepest soil layer.In contrast, sulfate exhibited a sinuous trajectory, with minimum values at 60–80 cm.Compared to sulfates, the stratification toward the topsoil was 35% higher for nitrates.Sulfates in the upper layers failed to predict sulfate concentrations in deep layers.Nitrate at 20–60 cm was an acceptable predictor of subsoil nitrate (60–160 cm). [ABSTRACT FROM AUTHOR]

The impacts of cloud mixing and uptake on wet scavenging are not adequately resolved in global models which can lead to an overestimation of the removal of water‐soluble gases and aerosols from the atmosphere. To address this issue, we develop and implement novel parameterizations to consider the impacts of these processes. Our analysis of vertical profiles of nitric acid, inorganic nitrate, ammonium, and sulfate concentrations during the Atmospheric Tomography Mission periods indicates that air refreshing limitation has a significant impact above 800 hPa, while cloud ice uptake limitation plays an important role above 500 hPa. Incorporating these two processes resulted in a reduction of wet depositions of these species across source regions and a slight increase in their downwind regions. Wet depositions of nitrate, ammonium, and sulfate were reduced in source regions by 22.7%, 8.4%, and 8.3%, respectively and increased in downwind regions by 10.1%, 7.0%, and 4.3%, respectively. Plain Language Summary: Atmospheric species in cloud‐free or rain‐free air need time to be transported and mixed with those in cloudy or rainy air before being influenced by wet scavenging. Additionally, the efficiency of rainout of water‐soluble aerosols for cold clouds is expected to be limited by cloud ice uptake. The removal of water‐soluble aerosols from cold clouds only occurs when they are taken up by ice crystals. However, current models do not adequately address these two processes. In this study, we derived new approaches that consider the effects of air refreshing and cloud ice uptake limitations on wet scavenging. We found that these new approaches have significant impacts on the vertical profiles and wet deposition fluxes of nitrate, ammonium, and sulfate. Key Points: Air refreshing and cloud ice uptake limitations are not well resolved in global modelsAir refreshing limitation impacts vertical concentration profiles <800 hPa, while cloud ice uptake limitation is important above 500 hPaIn combination, the two processes reduced wet depositions across source regions and slightly increased wet depositions in downwind regions [ABSTRACT FROM AUTHOR]

The electrocatalytic nitrogen oxidation reaction (NOR) to generate nitrate is gaining increasing attention as an alternative approach to the conventional industrial manufacture. But, current progress in NOR is limited by the difficulties in activation and conversion of the strong N≡N bond (941 kJ mol−1). Herein, we designed to utilize sulfate to enhance NOR performance over an Rh electrocatalyst. After the addition of sulfate, the inert Rh nanoparticles exhibited superior NOR performance with a nitrate yield of 168.0 μmol gcat−1 h−1. The 15N isotope‐labeling experiment confirmed the produced nitrate from nitrogen electrooxidation. A series of electrochemical in situ characterizations and theoretical calculation unveiled that sulfate promoted nitrogen adsorption and decreased the reaction energy barrier, and in situ formed sulfate radicals reduced the activation energy of the potential‐determining step, thus accelerating NOR. [ABSTRACT FROM AUTHOR]

Abstract: The anion transport properties of a series of previously reported tren‐based anionophores have been revisited using new assays designed to measure anion uniport. This study provides new insights into the transport mechanism and selectivity of this important class of transporters. Specifically, we report the chloride and nitrate transport selectivity of these systems and quantify sulfate transport to determine EC50 values for sulfate transport for the first time. Two new assays were developed to study bicarbonate transport allowing accurate quantification of chloride/bicarbonate exchange. [ABSTRACT FROM AUTHOR]

Abstract: The building designed by Sansovino in 1532 as the new Mint of Venice underwent a change in its intended use, becoming in 1900 the Biblioteca Nazionale Marciana. A spectroscopic study concerning the surface stone materials of the current reading room (previously a courtyard) was attempted since the transformation lead to heavy micro‐ and macroclimatic variations. Many alterations were observed, such as blackening, cracking, incrustations, and mortars powdering. The employed techniques, such as Raman and Fourier Transform InfraRed‐Attenuated Total Reflectance spectroscopy, allowed identifying the substrate main components and their alteration phases, mainly sulfates and nitrates. These data represent important information when approaching such a famous building because every further intervention must be based on accurate scientific results. [ABSTRACT FROM AUTHOR]

Materials based on the cationic copper(II) hexanuclear 18-membered metallacrown [18-MC [ABSTRACT FROM AUTHOR]

Freezing point depression (FDP) modeling was performed for selected aqueous nitrate and sulfate salt solutions to evaluate Pitzer ion interaction parameter values at 273.15 K. 1-1 and 1-2 electrolyte solutions of NaNO3, KNO3, NH4NO3, Na2SO4, K2SO4, and (NH4)2SO4 were studied. New Pitzer parameter values of β0, β1, and Cϕ were obtained for the studied electrolyte solutions. FDP modeling was also used to determine temperature derivatives of interaction parameters for the Pitzer model for selected salt solutions. Osmotic and activity coefficients using the new parameter values are also presented. [ABSTRACT FROM AUTHOR]

Waters containing ClO4- and dissolved NO3-, derived from detonated explosives and solid propellants, often also contain elevated concentrations of other dissolved constituents, including SO42-. Four column experiments, containing mixtures of silica sand, zero-valent Fe (ZVI) and organic C (OC) were conducted to evaluate the potential for simultaneous removal of NO3-, SO42- and ClO4-. Initially, the flow rate was maintained at 0.5 pore volumes (PV) d-1 and then decreased to 0.1 PV d-1 after 100 PV of flow. Nitrate concentrations decreased from 10.8 mg L-1 (NO3-N) to trace levels through NO3- reduction to NH4+ using ZVI alone and through denitrification using OC. Observations from the mixture of ZVI and OC suggest a combination of NO3- reduction and denitrification. Up to 71% of input SO42- (24.5 ± 3.5 mg L-1) was removed in the column containing OC, and >99.7% of the input ClO4- (857 ± 63 mg L-1) was removed by the OC- and (ZVI + OC)-containing columns as the flow rate was maintained at 0.1 PV d-1. Nitrate and ClO4- removal followed first-order and zero-order rates, respectively. Nitrate >2 mg L-1 (NO3-N) inhibited ClO4- removal in the OC-containing column but not in the (ZVI + OC)-containing column. Sulfate did not inhibit ClO4- degradation within any of the columns. [ABSTRACT FROM AUTHOR]

In this work, a multianalytical methodology based on a combination of spectroscopic techniques such as Raman spectroscopy and micro energy dispersive X-ray fluorescence spectroscopy, and soluble salt analysis by means of ion chromatography followed by a correlation analysis of these data was applied, in order to identify the nature of the deterioration compounds present in different building materials located on inner rooms from the ground floor of the Igueldo lighthouse (San Sebastian, Basque Country, North of Spain), and in order to prove if marine aerosol could contribute to cause deterioration processes in this kind of materials. The main deterioration compounds identified were sulfate and nitrate salts. Taking into consideration the positioning of some materials, a gypsum plaster covering them could be the sulfate source responsible of the crystallisation process of a wide variety of sulfate salts. Nevertheless, in some areas were no gypsum plaster remains are present, ammonium sulfate crystallisations were identified. The presence of this kind of sulfate could suggest a possible sulfate input coming from the migration of ammonium sulfate (among other sulfate salts) carried on marine aerosol, which can be deposited on the facade of the lighthouse and migrate to its inner areas. The possible source of nitrates that could cause the crystallisation of a wide variety of nitrate salts identified in this work could be the infiltration of ammonium nitrates coming from seagull droppings from outdoor to indoor areas. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The article presents a study to quantify the effects of bicarbonate and phosphate on the desorption of antimony Sb(V) from sediments which are contaminated. It examines the desorption of Sb(V)sediment samples by phosphate, carbonate, sulfate and nitrate. The study reveals that phosphate has a strong mobilizing ability when compared to weaker carbonate. The dependence of adsorption of Sb(V) to the potential of hydrogen in the absence and presence of carbonate has revealed that adsorption densities were higher suggesting a competition with carbonate.

This study investigated the effect of silicic acid to the adhesion of Bacillus subtilis to metal oxide-coated surfaces. The first sets of column experiments were conducted under various concentrations of silicic acid. The second and third experiments were performed under various concentrations of sulfate and nitrate to compare the results from silicic acid. Bacterial breakthrough curves were obtained by monitoring effluent, and mass recoveries were quantified from these curves. The results show that, at silicic acid concentrations between 0 and 0.2 mM, bacteria were negatively charged, while the charges of metal oxides were changed from positive to negative. Bacterial adhesion to metal oxide- coated surfaces decreased sharply with increasing silicic acid concentration (bacterial mass recovery increased from 11.5 to 82.2%), as a result of the hindrance effect of silicic acid adsorbed Onto metal oxide-coated surfaces. Between 0.2 and 10 mM, both bacteria and metal oxides were negatively charged. Bacterial adhesion remained constant (mass recovery were 80.5 to 82.2%), despite the increasing silicic acid concentration, possibly as a result of the hindrance effect of polymerized silicic acid. That is, the bacterial approach to the metal oxide-coated surfaces could be disturbed through steric hindrance of polymerized silicic acid, which compensates the potential enhancement effect from the electrical double layer compression. The results also illustrate that the effect of silicic acid on bacterial adhesion was greater than those of sulfate and nitrate. This study demonstrates that silicic acid can play a significant role in bacterial interaction with metal oxide-coated surfaces. Water Environ. [ABSTRACT FROM AUTHOR]

The eastern Mediterranean Sea (EMS) is a nutrient-poor ocean with unusually high nitrate-phosphate ratios (up to 28:1) and relatively depleted 15N/14N ratios (expressed as δ15N) in deepwater nitrate (δ15NO3- of 2.5‰) and sediments (<3.5‰) that have been attributed to extensive N2 fixation. To quantify the role of atmospheric NO3- deposition in the N cycle in the EMS, we analyzed NO3- and its δ15N in samples of dry and wet deposition on biweekly and per event basis from April 2006 to September 2007 on the island of Crete. Both dry and wet deposition samples have consistently negative δ15N compared to air N2, implying a strongly depleted atmospheric source calculated to be (weighted annual estimate) -3.1‰. The low δ15N of wet deposition is in agreement with data from other environments, but the consistently depleted nature of dry deposition is unusual and supports the view of an origin from association of atmospheric NO3- mainly with dust and sea salt. This situation is due to high levels of sulphate compared to ammonium, sea salt, and lithogenic material. Mass balance and isotope-mixing calculations show that the present-day inputs of nitrate from external sources into the surface water layer of the eastern Mediterranean Sea have a weighted mean δ15N-NO3- of 0.5‰ to 1.5‰ and that particle flux to and mineralization in the deepwater pool over the last 40-50 years can account for the unusually low δ15N ratios found in deepwater NO3- without the need of any significant N2 fixation. [ABSTRACT FROM AUTHOR]

Microbial fuel cells (MFCs) simultaneously provide waste treatment while capturing energy in the form of electricity. Although these devices are being used in engineered and natural environments where nitrate or sulfate may inhibit power production, the effects of these electron acceptors have not been fully explored. This research investigated the effect of nitrate and sulfate on MFC power production when these chemicals are present at the anode. Nitrate decreased the maximum current and power density by 15 and 17%, respectively, when present at 20 mg/L, and sulfate caused the maximum current and power density to decrease by 4 and 7%, respectively (also at 20 mg/L). Stronger inhibition was observed at higher nitrate and sulfate concentrations, but power production persisted. Coulombic efficiency decreased as nitrate and sulfate levels increased, although this was not primarily due to the biochemical reduction of nitrate or sulfate; rather, it was probably because of the inhibition of exoelectrogens. [ABSTRACT FROM AUTHOR]

The article presents a study on the groundwater geochemistry of the Chihuahua City region in the Rio Conchos Basin in northern Mexico, and its implications for water resources management. Results showed that the background groundwater chemistry upstream of Chihuahua City results from feldspar weathering but beyond Chihuahua City, the chemical conditions are strongly modified owing to the disposal of sewage from public and industrial water supplie into the Rio Chuviscar. As a consequence, anions like chloride and and sulphate are mainly linked to surface sources, while nitrate is controlled in part by sewage from public supply and industry and in part by agricultural practices.

In light of recent reductions in sulphur (S) and nitrogen (N) emissions mandated by Title IV of the Clean Air Act Amendments of 1990, temporal trends and trend coherence in precipitation (1984–2001 and 1992–2001) and surface water chemistry (1992–2001) were determined in two of the most acid-sensitive regions of North America, i.e. the Catskill and Adirondack Mountains of New York. Precipitation chemistry data from six sites located near these regions showed decreasing sulphate (SO4²-), nitrate (NO3-), and base cation (CB) concentrations and increasing pH during 1984–2001, but few significant trends during 1992–2001. Data from five Catskill streams and 12 Adirondack lakes showed decreasing trends in SO4²- concentrations at all sites, and decreasing trends in NO3-, CB, and H+ concentrations and increasing trends in dissolved organic carbon at most sites. In contrast, acid-neutralizing capacity (ANC) increased significantly at only about half the Adirondack lakes and in one of the Catskill streams. Flow correction prior to trend analysis did not change any trend directions and had little effect on SO4²- trends, but it caused several significant non-flow-corrected trends in NO3-- and ANC to become non-significant, suggesting that trend results for flow-sensitive constituents are affected by flow-related climate variation, SO4²- concentrations showed high temporal coherence in precipitation, surface waters, and in precipitation-surface water comparisons, reflecting a strong link between S emissions, precipitation SO4²- concentrations, and the processes that affect S cycling within these regions. NO3- and H+ concentrations and ANC generally showed weak coherence, especially in surface waters and in precipitation-surface water comparisons, indicating that variation in local-scale processes driven by factors such as climate are affecting trends in acid-base chemistry in these two regions. [ABSTRACT FROM AUTHOR]

This article focuses on a study conducted to examine rapid removal of nitrate and sulfate in freshwater wetland sediments. Wetlands are often situated at points of ground water recharge and discharge or along streams and rivers, and thus biogeochemical processes in wetlands can affect downstream water quality, as for example by removing nutrients. Nitrate removal by wetlands has received particular attention because of the escalating problem of nitrate contamination of drinking water supplies, and the growing recognition that nitrogen pollution of rivers causes eutrophication of marine coastal waters, leading to problems such as harmful algal blooms and oxygen depletion. The purpose of this study was to investigate rates of removal of nitrate and sulfate from small wetlands of variable hydrology in the glacial landscape of southwestern Michigan. Push-pull tracer experiments were employed to evaluate the removal of nitrate and sulfate from ground water as it comes into contact with reduced wetland sediment. This is a measurement of the potential reaction rates insofar as the ground water is relatively enriched in nitrate and to a lesser extent sulfate compared to the sediment porewaters.

We studied the interactions between nitrogen (N) inflow (uptake rate per unit root length) and root growth in the capture of nitrate by soil-grown wheat (Triticum aestivum L. cv. Wembley). [15N]-nitrate was applied locally to soil overlying seminal roots of 42-d-old plants that had previously received N fertilizer (N+) or not (N0). [34S]-sulphate was also applied to check the specificity of the plant's responses to nitrate. No plants had exhausted soil nitrate by day 42. Over the next 7 d, inflow was stimulated in soil to which [15N]-nitrate was supplied in the N0 plants. N0 plants increased their root length densities throughout the root system, not only around the point of [15N]-nitrate application. Root length density did not change in the N+ plants. N0 plants captured 73% of the [15N]-nitrate in d; N+ plants captured only 13%. There was no evidence that the plants' responses to the localized application of nitrate had an effect on the uptake of sulphate. The dominant influence on the capture of nitrate was inflow, rather than root growth. [ABSTRACT FROM AUTHOR]

Sulfate and nitrate uptake capacity, ATP sulfurylase (ATPS) and nitrate reductase (NR) activity were determined in a set of maize hybrids representative of selection cycles carried out during the period 1930 through 1975. All the above metabolic parameters together with the grain yield were improved by the selection. The annual rate of the improvement was higher (double) for sulfate uptake than for ATPS and similar for NR and nitrate uptake. Significant correlations were evidenced between the uptake efficiency of the roots and the enzyme activity in the leaves both for sulfate and nitrate pathways, and also between the uptake and enzyme steps of nitrate and those of sulfate. This offered good evidence of a coupled genetic regulation between nitrogen and sulfur metabolism in maize. [ABSTRACT FROM AUTHOR]

The effects of different levels of nitrate and sulphate in acidic precipitation on the growth of the lichens Cladina rangiferina ( L.) Wigg. and C. stellaris (Opiz.) Brodo were compared. Permanent field plots in a Canadian boreal forest ecosystem received two years of spraying with artificial rains of ph 4.2 (ambient), 3.5 or 2.8, each containing one of four molar ratios of sulphate to nitrate, i.e. sulphuric acid alone, nitric acid alone: 2: 1 or 1 :2. A substantial fertilization effect was observed when C. rangiferina was watered with rain of pH 2.8, derived from nitric acid alone. Compared with before-treatment values, gains in mean dry weight ( + 62%) and mean podetial height ( + l4%) were obtained for this species, in addition to elevated levels of N in air-dried tissues. Post-treatment values for the mean dry weight of C. rangiferina were significantly reduced for those podetia sprayed with rain of low pH, derived from sulphuric acid alone. Although podetia of C. stellaris were stimulated by rains of pH 4.2, based on a higher concentration of nitric acid, there was no N fertilization following the most acidic sprays. Data from this study support the view that the N content of acidic rain can cause a short-term growth stimulation for those species able to absorb nitrate from solution. However, beneficial effects on growth of prolonged fertilization via acid rain inputs are unlikely. [ABSTRACT FROM AUTHOR]

15N-Nitrate and 35S-sulphate labelling experiments were performed with spring wheat (Triticum aestivum L. cv. Timmo) 44, 64, 79, 95 and 115 days after sowing (growth stages arbitrarily denoted I to V). Label was fed to the plants via a fraction of the root system, termed “donor root”, whereas the rest of the root (“receiver root”) was fed non-labelled nutrient solution. Net uptake rates for both nitrate and sulphate per unit root weight changed little from growth stage I to IV, but were considerably lower at stage V. On a whole-plant weight basis, uptake declined from stage I to IV, because root contribution to total plant weight declined. Between 80 and 95% of absorbed label was translocated to the shoot at all growth stages. At stage V, up to 30% of absorbed label was recovered in the ears. Labelling of the receiver root indicated that, at all growth stages, 10 to 17% of N and 12 to 32% of S translocated to the shoot was retranslocated to the root. This corresponds to between 35 and 85% of the label actually recovered in the roots. Analysis of 15N-labelling of xylem sap collected from receiver roots at growth stages I to IV indicated that about half of the reduced N in the sap is derived from cycling through roots of recently assimilated N. Evidence of cycling was also obtained at stage V. Labelled sulphate was the only form of S cycled in the plant, but it accounted for only 1 to 7% of the sulphate in the xylem sap. [ABSTRACT FROM AUTHOR]

The uptake of K+ ion was studied in the roots of wheat (Triticum aestivum L. cv. GK Szeged) and cucumber (Cucumis sativus L. cv. Budai csemege) seedlings grown in nutrient solution under nitrogen and sulfate stress conditions. Seedlings pretreated with 1 or 10 mM NaNO3, absorbed more K+ than those treated with 0.1 mM NaNO3. However, the posteffect of NaNO3 was considerably influenced by the Na2SO4, treatment. The results suggest that, at least partly, a feed‐back regulation of K+ uptake may occur. However, due to the high Na+ contents of the roots, a Na+ effect in this process cannot be excluded. The growth and dry matter yields of the roots and shoots were strongly influenced by the SO2−/4 and NO−/3 supply of the plants. Appreciable differences were experienced between wheat and cucumber seedlings. The optimum SO2−/4 concentration of the growth solution for maximal growth varied considerably between the species, and was also different for the roots and the shoots in a given species. [ABSTRACT FROM AUTHOR]

(1) Multiple regression analysis was applied to single-event samples of throughfall beneath oak trees to separate the contributions of dry deposition and canopy exchange to the net deposition (throughfall minus precipitation). (2) Results for chestnut oak (Quercus prinus L.) in the growing season indicate that 62 and 42% of the net deposition of SO 2/4 and Ca2-, respectively, were supplied by canopy exchange, with the remainder being washed-off dry deposition. For white oak (Quercus alba L.), the corresponding values were 81 and 73%, (3) Dry deposition accounted for 30 and 71% of the total atmospheric input of SO 2/4 and Ca2-, respectively. (4) For nitrate, dry deposition was at least 30% of the total atmospheric input, but some uptake of both wet and dry deposition probably occurred in the canopy. (5) For potassium, much of the measured dry deposition appeared to be particulate material released and redeposited within the canopy. (6) Wet deposition dominated the throughfall flux of sulphate and nitrate, but dry deposition dominated that for Ca2- and canopy exchange dominated that for K-. [ABSTRACT FROM AUTHOR]

Vegetative compatibility among 15 strains of Pseudocercosporella herpotrichoides and a strain of P. aestiva was assessed, using a range of sulphate non-utilizing, nitrate non-utilizing auxotrophic and morphological mutants. Selection for resistance to selenate and chlorate provided a system (or the isolation of spontaneous sulphate and nitrate non-utilizing mutants with relative ease. Other auxotrophic and morphological mutants were obtained after UV-mutagenesis. Compatible interactions were identified by complementary growth at the inierface between pairs of mutants with dissimilar phenotypes. While most strain combinations proved incompatible, compatible interactions were found in P. herpotrichoides between two unrelated W-type strains and also between two unrelated R-type strains. No complementation was observed between W-type and R-type strains or between P. herpotrichoides and P. aestiva. [ABSTRACT FROM AUTHOR]

Anaerobic oxidation of methane (AOM) by sulfate has been recognized as a critical process to maintain this greenhouse gas stability by limiting methane flux to the atmosphere. We show geochemical evidence for AOM in deep lake sediments and demonstrate that AOM is likely driven by iron (Fe) reduction. Pore-water profiles from Lake Kinneret (Sea of Galilee, Israel) show that this sink for methane is located below the 20-cm depth in the sediment, which is well below the depths at which nitrate and sulfate are completely exhausted, as well as below the zone of methanogenesis. Iron-dependant AOM was verified by Fe(III)-amended mesocosm studies using intact sediment cores, and native iron oxides were detectable throughout the sediments. Because anaerobic Fe(III) respiration is thermodynamically more favorable than both sulfate-dependent methanotrophy and methanogenesis, its occurrence below the zone of methane production supports the idea that reduction of sedimentary iron oxides is kinetically or biologically limited. Similar conditions are likely to prevail in other incompletely pyritized aquatic sediments, indicating that AOM with Fe(III) is an important global sink for methane. [ABSTRACT FROM AUTHOR]

Unsaturated-zone sediments and the chemistry of shallow groundwater underlying a small (~8-km²) watershed were studied to identify the mechanisms responsible for anion storage within the Miocene Bridgeton Formation and weathered Coastal Plain deposits in southern New Jersey. Lower unsaturated-zone sediments and shallow groundwater samples were collected and concentrations of selected ions (including NO3- and SO42-) from 11 locations were determined. Grain size, sorting, and color of the lower unsaturated-zone sediments were determined and the mineralogy of these grains and the composition of coatings were analyzed by petrographic examination, scanning electron microscopy and energy dispersive analysis of x-rays, and quantitative whole-rock x-ray diffraction. The sediment grains, largely quartz and chert (80-94% w/w), are coated with a very fine-grained (<20 µm), complex mixture of kaolinite, halloysite, goethite, and possibly gibbsite and lepidocrocite. The mineral coatings are present as an open fabric, resulting in a large surface area in contact with pore water. Significant correlations between the amount of goethite in the grain coatings and the concentration of sediment-bound SO42- were observed, indicative of anion sorption. Other mineral-chemical relations indicate that negatively charged surfaces and competition with SO42- results in exclusion of NO3- from inner sphere exchange sites. The observed NO3- storage may be a result of matrix forces within the grain coatings and outer sphere complexation. The results of this study indicate that the mineralogy of grain coatings can have demonstrable effects on the storage of NO3- and SO42- in the unsaturated zone. [ABSTRACT FROM AUTHOR]

Particulate matters with aerodynamic diameter less than 10 µm (PM10) were collected with high-volume samplers for four periods of consecutive samplings. Each period included a high PM10 (defined as PM10 > or = 110 µg/m³) episode. The concentrations of all ionic species of high PM10 day (HPD) samples were higher than those of low PM10 (defined as PM10 < 110µg/m³) d (LPD) samples. Using the ionic concentrations of HPD samples at each station divided by those of LPD samples at respective stations, the results showed that NO3- increased most from LPD to HPD among the eight ionic species examined. A high mean value (3.15) of NO3-/elemental carbon (EC) ratio of HPD divided by that of LPD indicates that concentration variations due to chemical formation and nonchemical factors apparently were higher than those of the concentration variations due to nonchemical factors alone. The NO3-/SO42- ratio of HPD divided by that of LPD ranged from 1.62 to 3.92 for the four periods. The results indicate that more nitrate than sulfate had formed during high PM10 episodes. Multiple linear regression analysis showed that the percentage of NH4+ associated with nitrate and sulfate decreased and the percentage that could be explained by Ca2+ and Na+ increased on HPD. The reactions of HNO3 and H2SO4 with sea salt particles and with aqueous carbonates on soil particles during HPD were considered the main causes leading to these variations. [ABSTRACT FROM AUTHOR]

The Krusnehory (Erzgebirge or Ore Mountains) has been heavily affected by high atmospheric pollutant deposition caused by fossil fuel combustion in an adjacent Tertiary coal basin. Long-term routine sampling of bulk precipitation (1977-1996) and stream water (1977-1998) in aforested area on the south-eastern slope of the mountains were used to evaluate trends and patterns in solute concentration and flux withrespect to controlling processes. From 1977 to 1996, the annual volume-weighted Ca2+ and SO2-4concentrations decreased in bulk precipitation. However, after 1989, when a pronounced and continuous decrease occurred in coal production, annual volume-weighted concentrations decreased for most solutes, except H+. The concentration decreases were marked, with 1996 levels at or below 50% of those in 1989. The lack of a trend in H+ is attributed to similar decreases in both acid anions and neutralizing base cations. Stream water concentrations of most solutes, i.e. H+, Ca2+, Mg2+, SO2-4 NO2-4 were highest at the onset of sampling in 1977, decreased markedly from 1977 to 1983 and decreased moregradually from 1983 to 1998. The spruce forest die-back and removal reduced dry deposition of these solutes by reducing the filtering action, which was provided by the forest canopy. A notable decrease in stream water Ca2+ concentrations occurred after 1995 and may be due to the depletion of Ca2+, which was provided by catchment liming in 1986, 1988 and 1989. Solute flux trends in bulk atmospheric deposition and stream water generally were not significant and the lack of trend is attributed to the large interannual variability in precipitation quantity and runoff, respectively. All solutes except Na+ varied seasonally. The average seasonal concentrations varied between the solutes, but for most solutes were highest in [ABSTRACT FROM AUTHOR]

Weekly precipitation and stream water samples were collected from small watersheds in Denali National Park, Alaska, the Fraser Experimental Forest, Colorado, Isle Royale National Park, Michigan, and the Calumet watershed on the south shore of Lake Superior, Michigan. The objective was to determine if stream water chemistry at the mouth and upstream stations reflected precipitation chemistry across a range of atmospheric inputs of H +, NH 4 +, NO 3- , and SO 4 2-. Volume-weighted precipitation H +, NH 4 +, NO 3- , and SO 4 2- concentrations varied 4 to 8 fold with concentrations highest at Calumet and lowest in Denali. Stream water chemistry varied among sites, but did not reflect precipitation chemistry. The Denali watershed, Rock Creek, had the lowest precipitation NO 3- and SO 4 2- concentrations, but the highest stream water NO 3- and SO 4 2- concentrations. Among sites, the ratio of mean monthly upstream NO 3- concentration to precipitation NO 3- concentration declined (p < 0.001, R 2 = 0.47) as precipitation NO 3- concentrationincreased. The ratio of mean monthly upstream to precipitation SO 4 2- concentration showed no significant relationship to change in precipitation SO 4 2- concentration. Watersheds showed strong retention of inorganic N (> 90 percent inputs) across inputs ranging from 0.12 to > 6 kg N ha - 1 y -1. Factors possibly accounting for the weak or non-existent signal between stream water and precipitation ion concentrations include rapid modification of meltwater and precipitation chemistry by soil processes, and the presence of unfrozen soils which perm [ABSTRACT FROM AUTHOR]