The effects of sulphur dioxide on the parasitism of the rust fungus Uromyces viciae-fabae on Vicia faba

Vicia faba cv. Aguadulce was grown in fumigation chambers ventilated with filtered air or air containing sulphur dioxide (SO(2)) at controlled concentrations, and inoculated with the rust fungus Uromyces viciae-fabae. The influence of the pollutant was rated in terms of production of uredia and dehiscent urediospores. Exposures to SO(2) levels around 70-90 nl litre(-1) enhanced uredia density. Pre-inoculation fumigations at 70-86 nl litre(-1) increased uredia density, whilst post-inoculation fumigations stimulated urediospore production. Lower concentrations increased diffusion resistance of the host plant and slightly increased uredia density. Concentrations between 100 and 130 nl litre(-1) were somewhat inhibitory for the parasite, even in the absence of any visible damage symptoms on the host. Total sulphur accumulation in leaf tissue was reduced by the presence of the fungal infection. Growing under SO(2) pollution neither decreased germination ability nor modified morphological parameters of the urediospores. However, elongation of the germination tube of spores coming from filtered air was adversely affected by the pollutant.     

Growth responses of three legume species exposed to simulated acid rain

Seedlings of Vicia faba L., Phaseolus multiflorus L. and Pisum sativum L. were raised during exposure to simulated acid rainfall treatments of pHs 5.6, 4.5, 3.5 and 2.5 at a rate of 30 mm per week. All three species were found to be adversely affected by the more acid pH 3.5 and pH 2.5 treatments after 7-8 weeks of exposure. There were total plant dry weight reductions of 40% for V. faba, 31% for P. sativum and 28% for P. multiflorus exposed to the pH 2.5 treatment, as compared to those grown in the control (pH 5.6 treatment). In addition, V. faba was found to be sensitive to the pH 4.5 treatment with an 18% reduction in total plant weights (compared to plants grown in the pH 5.6 treatment). In P. multiflorus, reduction in the dry weights of shoots in response to increasing acidity of rain was not accompanied by reduction in root weights, indicating an interference in the partitioning of assimilates. It is concluded that these three species, and V. faba in particular, may be growing below their potential in much of the UK.     

The MAGIC simulation of surface water acidification at, and first year results from, the Bear Brook Watershed Manipulation, Maine, USA

The catchments of East and West Bear Brooks, Maine, USA, have been hydrologically and chemically monitored for 3.5 years. Stream chemistries and hydrographs are similar. These clear water streams are low in ANC (0-70 microeq litre(-1)), with variations caused by changing concentrations of base cations, SO4, NO3 and Cl. The latter range between 90-120, 0-40 and 65-75 microeq litre(-1), respectively. The West Bear catchment is being treated with six applications per year of dry (NH4)2SO4 at 1800 eq ha(-1) year(-1). After one year of treatment, the response of the stream chemistry and the response modelled by MAGIC are similar. Retentions of NH4 and SO4 are nearly 100% and greater than 80%, respectively. The additional flux of SO4 is compensated principally by an increased Ca concentration. Episodes of high discharge in the treated catchment are now characterized by lower ANC and pH, and higher Al than prior to the manipulation. Concentrations of NO3 have increased about 10 microeq litre(-1) during the dormant season, presumably due to additional nitrification of N from NH4. Discharge-chemistry relationships indicate that changes in stream chemistry, except for NO3, are dominated by ion exchange reactions in the upper part of the soil profile.     

The impact of constituent ions of acid mist on assimilation and stomatal conductance of Norway spruce prior and post mid-winter freezing

Norway spruce seedlings were sprayed twice weekly with one of a range of artificial mists at either pH 2.5, 3.0 or 5.6, for three months. The mists consisted of either (NH4)2SO4 (pH 5.6), NH4NO3 (pH 5.6), water (pH 5.6), HNO3 (pH 2.5), H2SO4 (pH 2.5). In late December 1988 and early January 1989 the light response of assimilation and stomatal conductance were assessed in the laboratory following a 4-day equilibration period at 12 degrees C. The intact trees were then subjected to a mild (-10 degrees C), brief (3 h) frost in the dark and the recovery of light saturated assimilation (Amax) was followed during the subsequent light period. The same trees were then subjected to a second 3 h (-18 degrees C) frost. The recovery of Amax during the next day was followed. All ion-containing mists stimulated Amax and apparent quantum yield relative to control trees, irrespective of pH. The mists containing SO4 made stomatal conductance unresponsive to light flux density and caused the stomata to lock open. Frosts of -10 degrees C and -18 degrees C did not inhibit the Amax of control trees for longer than 200 min into the light period. In contrast, the ion-containing mists exerted a significant inhibitory effect upon the recovery of Amax. Nitric acid inhibited Amax to 35% of the pre-frost value, whilst the remaining treatments inhibited Amax between 15% and 40% of the pre-frost value. It is concluded that SO4 causes increased mid-winter frost sensitivity and NO3 ameliortes this effect. The results are discussed in relation to forest decline.     

Relationship between SO2 dose and growth of the pea aphid, Acyrthosiphon pisum, on peas

A series of experiments was carried out in controlled environment cabinets to investigate the effects of SO(2) dose on the mean relative growth rate (MRGR) of pea aphids, Acyrthosiphon pisum, feeding on the pea plant, Pisum sativum. There was a significant linear increase in the MRGR of aphids feeding on SO(2)-fumigated plants, relative to control aphids feeding on plants in charcoal-filtered air. The increase in MRGR reached a maximum of 11% at SO(2) concentrations between 90 and 110 nl litre(-1). MRGR declined at higher SO(2) concentrations until above 220 nl litre(-1) it was below that of the controls. The dose-response curve is discussed in relation to reported changes in the nitrogen metabolism of plants subject to air pollution, the response of aphids to host plant nitrogen and possible toxic effects of high concentrations of SO(2) on the aphid.     

Foliar injury in young Betula pendula roth., Salix purpurea L. and Ilex aquifolium L. trees and in propagated Taxus baccata L. shoots exposed to intermittent fog at a range of acidities

The occurrence of various visible symptoms of foliar injury was assessed on a 5-point scale for each of the species. There was a distinct increase in the incidence of most types of injury in plant material which has been exposed to pH 2.5 acid fog. No clear pH-related trend in foliar injury occurred in plants exposed to acid fog at pH 3.5, pH 4.5 and pH 5.6, indicating that a threshold for a range of different types of visible injury may exist between pH 2.5 and pH 3.5 for all four species.     

The in-vitro response of pollen germination and tube length to different types of acidity

Pollen germination and tube growth are among the most sensitive responses to atmospheric pollution. Both these are inhibited by the acidity of the growth medium. Pollen grains from two species (Pinus cembra L. and Sambucus nigra L.) were germinated in media over a range of pHs (5.0, 4.5, 4.0, 3.5, 3.0 and 2.5) and six types of acidity (H(2)SO(4), HNO(3), H(2)SO(4): HNO(3) in 1:1, 2:1, 3:1 and 5:1 ratio). Pollen of the Gymnosperm is shown to be more resistant to acidity in the medium. Sulphuric acid alone and the ratio 2:1 with nitric acid are demonstrated to be the more harmful for P. cembra and S. nigra, respectively. The latter species was sensitive to all mixtures, particularly in respect to germination percentage.     

Effect of SO2 on the reproduction of pea aphids, Acyrthosiphon pisum, and the impact of SO2 and aphids on the growth and yield of peas

Pea aphids feeding from birth to maturity on pea plants (Pisum sativum) exposed to SO(2) concentrations of 50 nl litre(-1) or 80 nl litre(-1) showed a significant 19% increase in the rate of nymph production during the reproductive period, compared to control aphids feeding on plants in charcoal-filtered air. The higher nymph production resulted in a mean 4.6% increase in the intrinsic rate of population increase (rm). In longer term glasshouse fumigation experiments pea aphid populations were, on average, 1.8 times greater on pea plants in ambient air plus 45 nl litre(-1) SO(2) than in ambient air alone. Aphid infestation in ambient air caused a 42% reduction in pea yield and affected most plant parameters adversely. Ambient air plus SO(2) had no direct effect on yield, but, in combination with aphid infestation, a further 10% reduction in yield was recorded.     

Chemical climatology of high elevation spruce-fir forests in the southern Appalachian mountains

The physical and chemical climatology of high elevation (> 1500 m) spruce-fir forests in the southern Appalachian mountains was studied by establishing a weather and atmospheric chemical observatory at Mt Mitchell State Park in North Carolina (35 degrees 44' 05" N, 82 degrees 17' 15"W). Data collected during the summer and autumn (May-October) of 1986, 1987, and 1988 are reported. All measurements were made on or near a 16.5 m walk-up tower extending 10 m above the forest canopy on Mt Gibbes (2006 m msl), which is located approximately 2 km SW of Mt Mitchell. The tower was equipped with standard meteorological instrumentation, a passive cloud water collector, and gas pollutant sensors for O3, SO2, NOx. The tower and nearby forest canopy were immersed in clouds 25 to 40% of the time. Non-precipitating clouds were very acidic (pH 2.5-4.5). Precipitating clouds were less acidic (pH 3.5-5.5). The dominant wind directions were WNW and ESE. Clouds from the most common wind direction (WNW) were more acidic (mean pH 3.5) than those from the next most common wind direction (ESE, mean pH 5.5). Cloud water acidity was related to the concentration of SO4(2-), and NO3- ions. Mean concentration of H+, NH4+, SO4(2-), and NO3- ions in the cloud water varied from 330-340, 150-200, 190-200 and 120-140 micromol litre(-1) respectively. The average and range of O3 were 50 (25-100) ppbv (109) in 1986, 51 (26-102) ppbv in 1987, and 66 (30-140) during the 1988 field seasons, respectively. The daily maximum, 1-h average, and 24-h average concentrations were all greatest during June through mid-August, suggesting a correlation with the seasonal temperature and solar intensity. Throughfall collectors near the tower were used to obtain a useful estimate of deposition to the forest canopy. Between 50-60% of the total deposition of SO4(2-) was due to cloud impact.     

The effects of simulated acid rain on the growth of three herbaceous species grown on a range of British soils

Seedlings of winter barley, perennial ryegrass and white clover were grown on a range of British soils for 21-24 weeks and exposed to simulated acid rainfall treatments of pHs 5.6, 4.5, 3.5 and 2.5. Whilst leaves of white clover developed leaf lesions after 18 weeks of exposure to the pH 2.5 treatments, there were no signs of visible injury to the other two species. At harvest, it was noted, for all species, that there was a large amount of variation in the sizes of individual plants and this made it difficult to detect differences between the treatments for plants on an individual soil. However, in combined analyses for all soils, it was found that the treatments had substantial effects on the yields of plants. The yields of both winter barley and clover were highly correlated with rainfall pH, showing substantial reductions in the more acid rains as compared to the pH 5.6 (control) treatment. In contrast, plants of perennial ryegrass produced higher yields of shoots at the most acid (pH 2.5) as compared to the other treatments. It was noted that the pH 2.5 treatment resulted in a generally lower soil pH at the termination of the experiment.     

Growth responses of birch and Sitka spruce exposed to acidified rain

Seedlings of birch and Sitka spruce were grown on a range of British soils for 2 years and exposed to simulated acid rainfall treatments of pHs 5.6, 4.5, 3.5 and 2.5. Both species developed visible leaf injury patterns when exposed to the pH 2.5 treatment. In Sitka spruce this leaf injury was followed by high needle loss during the first winter and greater mortality. Generally, height growth of Sitka spruce was unaffected by treatments, but acid rainfall at pH 2.5 increased the height of birch. Mean height of both species was strongly affected by soil type. Significant soils x treatment effects on the heights of both species indicated that on some soils plant growth responses to the treatments did not fit the general pattern. Hence, while the results indicate that generally ambient acidities of rainfall in the UK are unlikely to adversely affect the growth of birch or Sitka spruce, plants growing on some soils may be susceptible to injury.     

Peroxidative processes induced in bean leaves by fumigation with sulphur dioxide

Bean plants have been fumigated for 1 h with 300 or 1000 nl litre(-1) SO(2). Dependent on the SO(2) concentration, we observed an evolution of ethane the leaves. Even with 1000 nl litre(-1) SO(2) the evolution lasted for only 4 h. Pretreatment of single leaves with the radical scavenger ethoxyquin prevented this SO(2)-induced ethane formation. Another indication for the initiation of radicalic peroxidative processes by SO(2) was obtained by the manipulation of the endogenous antioxidants vitamin C and glutathione. An increase of both compounds by application of precursors of both biosynthetic pathways could completely suppress peroxidative ethane evolution. We also found a very good quantitative correlation between endogenous glutathione and ethane formation after SO(2) treatment. During these peroxidative processes, several cell components like fatty acids, chlorophylls, carotenoids and vitamin C were decreased. Based on our results, a mechanism for SO(2) induction of radical reactions leading to peroxidation and the role of endogenous antioxidants are discussed.     

Effects of sulphur dioxide and nitrogen dioxide, singly and in mixture, on the macroscopic growth of three birch clones

An investigation of some aspects of the effects of low concentrations of the gases, sulphur dioxide and nitrogen dioxide, singly and in mixture, was made on the growth of three birch clones, two of Betula pendula Roth. (silver birch) and one of Betula pubescens Ehr. (downy birch). Comparative measurements of the growth form and dry mass increment were made over one year in glasshouses supplied with charcoal-filtered ambient air, and SO(2) and NO(2), singly or in mixture, at mean concentrations of 62 ppb (nl litre (-1)) of one or both gases. The main effects were found in those plants that were fumigated with SO(2) singly, and SO(2) and NO(2) together. Both treatments induced premature leaf loss and reduction in mass, especially of roots, the effects increasing over time. The heights and initial leaf areas were maintained, apparently at the expense of other parameters. NO(2), if present singly, had little or no effect, but it tended to enhance the damaging effect of SO(2) when the two were applied together. The different clones showed different degrees of response to the pollutants, but these differences became less marked during the second season of fumigation. The effects found are discussed in relation to the annual growth of trees, particularly birch.     

Interactions between Sitka spruce, the green spruce aphid, sulphur dioxide pollution and drought

Sitka spruce trees, with and without the aphid Elatobium abietinum and/or drought treatment, were subjected to 25 nl litre(-1) of sulphur dioxide over a 2-month period. Aphids became three times as abundant on the fumigated trees if they were well watered and twice as abundant on trees from which water was withheld, compared with unfumigated controls. Growth parameters of the trees were little affected by pollution alone, but were substantially reduced by either aphids or drought. There was a significant interaction between SO(2) and aphids in a further reduction of both leader extension and root weight. Root weight was also reduced by 24% more than expected from the additive effects of the combined SO(2) and drought treatment.     

Effects of air filtration at small SO2 and NO2 concentrations on the yield of barley

Two cultivars of Igri and Gerbel winter barley Horteum vulgare L. were grown in open-top chambers in filtered and unfiltered air at a site with approximately 10 nl litre(-1) SO2 and 12 nl litre(-1) NO2 (seasonal mean). The experiment ran for three consecutive seasons 1982-1983, 1983-1984, 1984-1985, and significant effects of filtration were observed for each crop. In years 1982-1983 and 1984-1985, the crops in unfiltered air yielded larger grain dry matter, 9% in 1982-1983, and 8% in 1984-1985. For both crops, the differences were statistically significant at the 5% level. Differences were also observed for the remaining above-ground dry matter, and these were consistent in direction in each year but statistically significant only in 1984-1985. In both growing seasons (1982-1983 and 1984-1985), there were no major pest infestations and no long-term water stress or photochemical ozone episodes. In the remaining experiment (1983-1984) similar air concentrations of SO2 and NO2 produced effects of the opposite sign to those observed in 1982-1983 and 1984-1985. Significant reductions in grain yield (13%) were obtained in unfiltered air. The only major environmental difference for the 1983-1984 crop was a notable dry period in May and June 1984 with marked water stress in the crop, requiring irrigation. These results suggest that the relationship between yield and pollutant concentration may be confounded by additional stresses, many of which are a common component of the growing season for major crops.     

Effects of nitrogen dioxide pollution on the growth of three fern species

The effects of exposing plants of Dryopteris filix-mas (L.) Schott, Phyllitis scolopendrium (L.) Newman and Polypodium vulgare L. to 60 nl litre(-1) (122 microg m(-3)) NO(2) for 37 weeks were investigated in a closed chamber fumigation system. There was no effect of NO(2) on the numbers of fronds produced for any species at any time during the exposure period. However, at the end of the study, there was a lower dry weight yield of green shoots of D. filix-mas and P. scolopendrium and a higher yield of green shoots of P. vulgare for plants in the NO(2) treatment as compared to control plants. These differences in shoot dry weights were not accompanied by an effect of NO(2) exposure on total plant dry weights.     

采用杂多酸化合物溶液同时脱硫脱氮的实验研究

本文对液相催化氧化脱硫脱氮的新方法进行了研究 ,在鼓泡反应发生器内进行了液相催化氧化脱硫脱氮的实验。采用钼硅酸溶液及其还原产物脱除烟气中的SO2 和NOX,分别就吸收液的浓度、pH值、温度、停留时间等因素对SO2 和NOX 去除效率的影响及其变化规律进行了研究。实验结果表明 ,钼硅酸能十分有效地吸收SO2 ,将SO2 氧化成H2 SO4,并使杂多酸还原为杂多蓝。随后又被用于去除NOX,把NOX 还原成N2 ,蓝色溶液再次被氧化成为黄色溶液     

Acid neutralization of precipitation in Northern China

There is an increasing concern over the impact of human-related emissions on the acid precipitation in China. However, few measurements have been conducted so far to clarify the acid-neutralization of precipitation on a regional scale. Under a network of 10 sites across Northern China operated during a 3-year period from December 2007 to November 2010, a total of 1118 rain and snow samples were collected. Of this total, 28% was acid precipitation with pH < 5.6. Out of these acid samples, 53% were found heavily acidic with pH value below 5.0, indicating significantly high levels of acidification of precipitation. Most of the acidity of precipitation was caused by H2SO4 and HNO3, their relative contribution being 72% and 28%, respectively. However; the contribution of HNO3 to precipitation acidity will be enhanced due to the increasing NO(x) and stable SO2 emissions in future. Neutralization factors for K+, NH4+, Ca2+, Na+, and Mg2+ were estimated as 0.06, 0.71, 0.72, 0.15, and 0.13, respectively. The application of multiple regression analysis further quantified higher NH4+ and Ca2+ contribution to the neutralization process, but the dominant neutralizing agent varied from site to site. The neutralization was less pronounced in the rural than urban areas, probably due to different levels of alkaline species, which strongly buffered the acidity. Presence of high concentrations of basic ions was mainly responsible for high pH of precipitation with annual volume-weighted mean (VWM) values larger than 5.6 at several sites. It was estimated that in the absence of buffering ions, for the given concentration of SO4(2-) and NO3-, the annual VWM pH of precipitation would have been recorded around 3.5 across Northern China. This feature suggested that emissions of particles and gaseous NH3 played very important role in controlling the spatial variations of pH of precipitation in the target areas.     

Exposure of two upland plant species to acidic fogs

A system is described for exposing large numbers of plants to acidic fogs. The system allows low volumes of treatment solutions to be provided at particle sizes chiefly in the 5-30 microm range (equivalent to fog/cloud droplets). Plants of Poa alpina L. and Epilobium brunnescens were propagated from material collected in Snowdonia, North Wales and exposed to fog treatments at pH values of 2.5, 3.5, 4.5 and 5.6. There were 3 x 4 h exposures per week which provided a total of 6 mm deposition. Supplementary watering was with pH 4.5 simulated acid rain (24 mm per week). After 21 weeks, there was increased lowering and a greater dry weight for plants of E. brunnescens exposed to the pH 2.5 fog in comparison with other treatments. Also, the plants used assimilated material to form shoots rather than roots. A similar increase in dry weight accumulation in the pH 2.5 treatment was found in P. alpina after 63 weeks but this was not associated with changes in assimilate partitioning.     

Effects of rural roadside levels of nitrogen dioxide on Polytrichum formosum Hedw

Polytrichum formosum Hedw. was exposed to 60 nl litre(-1) (122.4 microm(-3)) NO2 for 37 weeks in a closed chamber fumigation system. This concentration was chosen to simulate roadside levels in rural areas. Over an initial winter period (October-January) growth of existing shoots was stimulated by NO2. When new growth was recorded in April and May, NO2 pollution over winter and spring had resulted in a 36% reduction in new (< 1 cm) shoot production, and a 46% reduction in old shoots showing new growth. It is concluded that plants of Polytrichum formosum Hedw. growing near to roads may be adversely affected by NO2 pollution. Adverse effects of NO2 on plants and possible synergistic effects with other pollutants could cause growth reductions in sensitive species, thus affecting species composition of roadside vegetation.