Meteorological analyses of acidic precipitation in Ontario

Meteorological analyses of precipitation and air quality data for the period 1976 to 1983 have been undertaken to infer potential source regions of acidity in Ontario. Techniques such as air parcel trajectory modelling and synoptic weather classification have been utilized. A meteorological data acquisition system has been implemented to provide historical and real-time trajectory statistics. This paper provides an overview of these studies. For areas of South and Central Ontario, precipitation events most commonly occur with pre-warm front and cyclonic situations, and trajectories from the south and southwest octants. Furthermore, most of the reported wet deposition of S and N is associated with trajectories from these octants, the direction of the Ohio Valley industrial source region and industrialized SW Ontario. High air concentrations of S and N are also associated with trajectories from these octants.     

Interaction of nitrate and sulfate reduction in tobacco

A series of experiments was conducted to study the interrelationship of sulfate (SO₄) and nitrate (NO₃) reduction in ‘Ky14’ tobacco plants (Nicotiana tabacum L.) as influenced by nutrient solution availability of NO₃ and SO₄. The activities of ATP sulfurylase and NO₃ reductase, the first steps of SO₄ and NO₃ reduction, respectively, have been considered as indicators of the state of regulation of the assimilatory pathways of SO₄ and NO₃. Activity of ATP sulfurylase was derepressed when SO₄ was limited in the nutrient solution, provided that there was a net accumulation of reduced N in the tissue. The availability of SO₄ or the lack of N resulted in repressed activity of ATP sulfurylase. Nitrate reductase activity was induced when NO₃ was available in the nutrient solution, provided that there was a net accumulation of reduced S in the tissue. When NO₃ was limited in the nutrient solution or there was a lack of S, repression of NO₃ reductase activity resulted.     

A method for extracting sulfate from sphagnum peat

Abstract

The efficacy of five solutions for extracting sulfate from a peat‐based medium was investigated. Extracting solutions used were 10 mM LiCl, 10 mM KC1, 100 mg/L P, 500 mg/L P, 0.15% CaCl₂, or distilled water. Equilibration time affected the amount of sulfate extracted with the use of 100 mg/L P or distilled water extractants. Differences in the amount of sulfate extracted were observed at 0.5‐, 4‐, and 12‐hour equilibration times. Extraction effectiveness increased with the increase of equilibration time, up to a maximum of 4 hours. The concentration of sulfate extracted with all extractants levelled off at the 2‐hour equilibration time. CaCl₂ was the most effective solution for the extraction of water‐soluble sulfate. Water‐soluble sulfate plus absorbed sulfate was most efficiently extracted with 500 mg/L P. No relationship was observed between measured sulfate and the pH levels of the extracted solutions.     

Sensitivity of southern quebec lakes to acidic precipitation

Physico-chemical data from 258 Quebec lakes were collected during spring and summer 1980. These data are examined in order obtain a first general diagnosis of lake acidification in Quebec. The spatial variation of the mineralization of lakes is interpreted in relation to lithology and glacial deposits, allowing the identification of Shield areas particularly threatened by acid precipitation. A strong south-west to north-east gradient in sulphate concentration is observed and interpreted as a result of long range atmospheric transport of S and as an indication of increased sulphate levels in southern Quebec lakes. The frequency distribution of pH values and the relation between pH and sulphate are examined; the results obtained suggest that many Shield lakes are probably affected by acid precipitation. A comparison is made between spring and summer conditions; data obtained in spring show a substantial decrease in pH and alkalinity.     

The influence of storm characteristics on sulfate in precipitation

The effects of storm dynamics on precipitation chemistry were examined using an atmospheric budget for SO₄ ^? . One hundred storms occurring between 1975 and 1978 at Hubbard Brook Experimental Forest in New Hampshire were used as test data. Concentrations of major ions were usually greater in convective storms than in continuous or layer storms. For example the geometric mean concentrations of SO₄ ^? in convective and continuous storms were 4.1 and 1.1 mg L^?1, respectively. Higher SO₄ ^? concentrations also occurred when surface wind directions were south or southwest. The summer maximum in convective activity along with the seasonal dependence of surface wind directions and the seasonal atmospheric chemistry cycle can account for the summer maximum in SO₄ ^? concentrations observed in the northeastern United States.     

Effects of acidic precipitation and acidity on soil microbial processes

Effects of soil acidity on microbial decomposition of organic matter and transformation of N in an acid forest soil were investigated. In the oak-leaf-amended pH-adjusted acid soils, CO₂ production in 14-and 150-day preincubated samples decreased by about 6 and 37%, respectively. In the control (unamended) acidified soils, reductions in CO₂ production of 14% in 14-day preincubated samples and of 52% in 150-day samples were observed. Ammonia formation in the pH-adjusted acid soil was about 50% less than in the naturally acid soil. Increased rates of ammonification and nitrification were observed in the pH-adjusted neutral soil. Little autotrophic and heterotrophic nitrifying activity was detected in naturally acid and acidified forest soils. The rate of denitrification was rather slow in acid soils, and at greater acidities N₂O was the predominant end product. The abundance of N-fixing free-living bacteria was very low in acidic and acidified forest soils, and N gains by asymbiotic bacterial fixation in an acid forest ecosystem may be insignificant. These results suggest that further acidification of acid forest soils by addition of H₂SO₄ or by acid precipitation may lead to significant reductions in the leaf litter decomposition, ammonification, nitrification, and denitrification and thus reduce nutrient recycling in the forest ecosystem.     

Assessment of a selection pressure for improved nitrate and sulfate recovery by Maize

The increase in grain yield of current maize cultivars has been conditioned by the abundant supply of fertilizers, potentially involving energy waste and environment pollution. The shift from frugality to luxury consumption has been attributed to the scarce or zero selection pressure for improved nutrient recovery, due to the high fertility of soils usually adopted in breeding programs. Seven cycles of recurrent selection, starting from the same maize population and carried out on the same soil in conditions of either large (HF) or limited supply (LF) of macronutrients, have demonstrated the effectiveness of the selection pressure by reduced fertilizer application. Physiological parameters determined in seedlings growing in nutrient solution evidenced, in the LF population, a connection with both grain yield and efficiency of nitrate and sulfate recovery. Influx and efflux at steady supply or after deprivation, translocation to shoot, internal pool of both anions, and ATPase‐dependent H+ transport in plasmalemma vesicles were particularly significant.     

Spatial and temporal pattern of sulfate and nitrate wet deposition in Ontario

The spatial patterns of the precipitation-weighted mean concentration and total deposition of sulfate and nitrate in Ontario from 1981 to 1983 were determined using the Modified Simple Kriging method. The 3-yr averaged spatial patterns of sulfate and nitrate concentrations were similar to the sulfate and nitrate 3-yr averaged deposition patterns in Ontario. The overall spatial variability of nitrate was slightly higher than sulfate. The seasonal variation of nitrate concentrations and deposition were less regular than sulfate.     

Response of wheat,canola and alfalfa to simulated acidic precipitation

Wheat, canola and alfalfa were subjected to simulated acidic precipitation with pH ranging from 5.6 to 2.6 under controlled growth room conditions. The number of simulated precipitation events were 12, 10 and 21 for wheat, canola and alfalfa, respectively. In this short-term experiment, wheat, canola and alfalfa do not appear to be sensitive to the simulated acid rain treatments used. Wheat and canola showed no visible symptoms of injury with any of the treatments. The pH 2.6 resulted in whitish spots on alfalfa leaflets. The economic yield was not affected at any of the acidity levels used in this tudy. Dry weight of the aboveground vegetative parts of wheat and canola was stimulated by the most acidic treatment (pH 2.6), apparently as a result of the higher nutrient content of the simulated acidic rain. Although below ground biomass for any of the species tested was not affected by rain acidity, the shoot: root ratio was significantly higher at pH 2.6 than with the control. Chorophyll a concentration in alfalfa leaves was reduced at only the highest acidity treatment. Chlorophyll b was not affected. While K levels in alfalfa leaves were significantly reduced at pH 2.6, no change in the concentration of Ca, Mg and P was noted. Sulfur and N concentrations increased, mainly at pH 2.6, reflecting the composition of the simulated rain solution.     

A130 years deposition record of sulfate,nitrate and chloride from a high-alpine glacier

An ice core from a high-alpine glacier (Grenzgletscher, Colle Gnifetti, Monte Rosa massif, 4450 m a.s.l., Switzerland) was used to reconstruct the pollution history of Central-Europe. Concentrations of the most important acidifying species sulfate and nitrate as well as of chloride were measured in 1151 samples with 5 cm resolution from the top 60 m of a 109 m long firn/ice core. This corresponds to a mean time resolution of 8 (bottom) to 14 (top) data points per year. A ²¹⁰Pb nuclear dating showed that the ice core covers a time period between 1850–1981 and that the mean accumulation rate was 0.33 m water equivalent per year. Between the two time periods 1850 – 1880 and 1965 – 1981 the mean sulfate concentrations increased by a factor of 5.8±0.9 and for nitrate by a factor of 2.3±0.3. The mean concentrations at the beginning of the industrial time (period 1850 –1880) was 0.078±0.008 mg/l for sulfate and 0.067±0.005 mg/l for nitrate. The mean chloride concentration was 0.047±0.004 mg/l and did not show a trend in concentration over the time period investigated. A distribution analysis of the measured concentrations for the two time periods 1850 – 1865 and 1965 – 1981 was performed which showed that the data have a nearly log-normal distribution.     

Iron and sulfate reduction in the sediments of acidic mine lake 116 (Brandenburg,Germany): Rates and geochemical evaluation

A combination of rate measurements of iron(III)oxide and sulfate reduction, thermodynamic data, and pore-water and solid phase analyses was used to evaluate the relative significance of iron and sulfate reduction in the sediments of an acidic strip mining lake (Lake 116, Brandenburg, Germany). The rate of sulfate reduction was determined using a 35S-radiotracer method. Rates of iron turnover were quantified by mass balances based on pore-water concentration profiles. The differences in Gibbs free energy yield from reduction of iron and sulfate and from methanogenesis were calculated from individual redox couples and concentrations of reactants to account for the influence of high Fe2+ concentrations and differing mineral phases. Integrated (O-20 cm) mean rates of sulfate reduction were 1.2 (pelagial), respectively 5.2 (littoral) mmol (m2d)-1. Based on electron equivalents, the estimated iron reduction rates reached between about 50 % (pelagial) and 75 % (littoral) of the sulfate reduction rates. Compared to conditions usually assumed in the literature, in the sediments Gibbs free energy advantage of iron reduction over sulfate reduction was reduced frmm +11 KJeq-1 to a range of about +7 KJeq-1 (ferrihydrite, "reactive iron") to -6 KJeq-1 (goethite). This indicates that iron reduction was thermodynamically favored to sulfate reduction only if amorphous iron(III)oxides were available and is in accordance to the high competitiveness of sulfate reducers in the sediment. While total iron concentration in the sediments was high (up to 80% of the dryweight), reactive iron only accounted for 11-38% and was absolutely and relatively diminished in the zone of iron reduction. Pore-water concentration gradients and 137CS profiles indicated that little or no bioturbation occurred in the sediments, probably inhibiting the renewal of reactive iron. We further hypothesize that the reactivity of the iron oxide surfaces was reduced due to adsorption of DOM, suggested by IR spectra of the DOM and by a surface coverage estimate using literature data. Pelagial and littoral sediments displayed different dynamics. At the littoral relative iron reduction rate estimates were higher, iron sulfides were not accumulated and residence times of iron oxides were short compared to the pelagial. At the littoral site reoxidation of iron sulfides probably resulted in the renewal of reactive iron(III)oxides, possibly allowing for higher relative rates of iron reduction.     

Relationship between wet deposition of sulfate and nitrate and rainfall amount in Japan

A regression model of wet deposition on rainfall amount for non-seasalt sulfate (nss-SO₄ ^2?) and nitrate (NO₃ ^?) was applied to a data set obtained through a nationwide survey from April 1989 to March 1993. Wet-only samples on a biweekly basis were collected at 29 sites over Japan. Reparameterized bivariate lognormal distribution was employed to describe the joint distribution of concentration (C) and rainfall amount (R) for each site. Ranges of geometric mean (μ_D) of biweekly deposition (D = C. R) for each site were 0.54–2.90 meq m^?2 for nss-SU₄ ^2?, and 0.21–1.36 meq m^?22 for NO₃ ^?; that of biweekly rainfall amount (μ_R) was 24.1–78.0 mm. Urban or industrialized areas had high values of μ_D for these ions. Ranges of estimates of the slope of the regression equation of log(D/μ_D) on log(R/μ_R), were 0.45–0.99 for nss-SO₄ ^2?, and 0.35–0.86 for NO₃ ^?; thus estimates of the slope for nss-SO₄ ^2? tend to be larger than those for NO₃ ^?. The present analysis, consequently, statistically clarified some differences between the two ions in deposition processes which is understood in the light of current knowledge of atmospheric chemistry.     

A method for identification and mapping potentially acid sulfate soils in Jutland, Denmark

A method for mapping potentially acid sulfate soils in Jutland, Denmark is described. First the wetlands were outlined, using already existing topographic maps. Then 7900 profiles, evenly distributed over the wetland areas, were examined to point out areas with potentially acid sulfate soils. The method used to identify potentially acid sulfate material was, for carbonate-free samples, a pH-measuring at the sampling time and after the samples were inoculated with soil water extract from an acid sulfate soil and 2, 8 or 16 weeks of incubation. For carbonate-containing samples the pyrite content was compared to the acid-neutralizing capacity. A map was constructed showing the ratio of profiles containing potentially acid sulfate soil samples to total number of profiles examined within natural geographical wetland regions.The investigation showed that 35% of the wetlands in Jutland have a high frequency of potentially acid sulfate soils.     

A simple method for estimating nitrate removal from floodwaters in river marginal wetlands

Abstract. Soil cores from river marginal wetlands in the UK, France and Ireland, sampled and contained within PVC piping, were flooded with nitrate-N enriched water. Half of the cores were sterilized prior to flooding to destroy the denitrifying bacteria. The change in nitrate-N concentration in the floodwater was measured over time. It is argued that the observed nitrate depletion rates (from 0.4 to 2.3 kg/ha per day) may be identified With microbially-mediated denitrification. The results show the method to be a simple and direct procedure for the assessment of spatial variation in nitrate-sink capacity. The depth of the denitrifying layer at the soil-water interface was confirmed to be of the order of a few mm.     

Response of two western Canadian conifers to simulated acidic precipitation

Ready-to-plant nursery stock of jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) were subjected to simulated acid rains of pH 5.6 (control), 4.6, 3.6, and 2.6 under controlled growth room conditions to determine the threshold for damage. The two species exhibited contrasting response patterns to simulated acid rain treatments. Growth and chlorophyll content of jack pine were not adversely affected at any of the levels applied. Furthermore, no macroscopic foliar injury symptoms were evident and foliar nutrient levels remained unaffected. White spruce showed no statistically significant reduction in growth rate at any of the treatments. Needle chlorophyll a content of white spruce was not affected by any of the treatments, while chlorophyll b level was significantly reduced at pH 2.6. Symptoms of visible injury were observed to increase with rain acidity. No statistically significant change in the levels of foliar nutrients of white spruce were found, with the exception of the elevated S concentration at pH 2.6.     

Frequency distributions for durations and volumes of rainfalls in the Eastern United States in relation to acidic precipitation

A significant percentage (between 17 and 40%) of all showers recorded on Long Island, NY, Urbana, IL, Franklin, NC, and Seaside Park, NJ, had durations less than 20 min. Similarly, a large percentage had durations less than 40 min (50, 46, and 32% for 3 yr at Urbana, IL, 65% at Coral Gables, FL, 50% at Franklin, NC, and 54% at Seaside Park, NJ). When all data from the six growing seasons were pooled, over 88% of all rainfalls were less than 160 min. Similar results were observed when volume measurements were made. Between 38 and 57% of all recorded showers had less than 1 mm at all five stations in the eastern United States. When all data were pooled, over 65% of all rainfalls were less than 3 mm. These data demonstrate that plant foliage is wetted during the growing season by numerous showers which are of short duration and low volume.     

南宁市蔬菜的硝酸盐含量及评价

通过调查和采样分析结果表明,南宁市各类蔬菜硝酸盐平均含量依次为叶菜类(1932 1mg·kg-1)>根菜类(944 1mg·kg-1)>葱蒜类(488 6mg·kg-1)>瓜菜类(183 6mg·kg-1)>茄果类(157 6mg·kg-1)>豆菜类(147 0mg·kg-1)>水生菜类(62 0mg·kg-1)。部分蔬菜受不同程度硝酸盐污染,以叶菜类污染最重(除韭菜),其次是根菜类和葱蒜类,污染指数在1 04～6 60,多数在2 0以上,其它各类蔬菜的污染指数均<1,未受硝酸盐污染。     

Effect of sulfate on nitrate transport in volcanic ash soils sampled from the A and the B horizons

Intensive cultivation of crop fields using agricultural chemicals and fertilizers has led to changes in ecological systems, resulting in a high possibility of environmental pollution by contamination, or occasional reactions not only in the soil but also in the water and the atmosphere. Some substances are known to be very toxic to human beings at low concentrations. For example, nitrosamines are believed to be carcinogenic and mutagenic.