Effects of artificial acidification and liming on the activity of digestive enzymes in Cognettia sphagnetorum (Vejdovsky´, 1878) (Annelida, Enchytraeidae)

The effects of simulated acid rain and acidification, combined with liming, on amylolytic, laminarinolytic and xylanolytic activity in whole body homogenates of enchytraeids Cognettia sphagnetorum were studied under field conditions. Simulated acid rain (pH 2.5) and simulated acid rain with subsequent liming (CaCO₃) were applied to experimental plots in a mixed forest soil. The pH of the soil was lowered by acid treatment (4.3), while the pH increased after liming (6.3) in comparison with the control (4.5). Acidification of soil caused a decrease in enchytraeid body mass and amylolytic activity. In acidified plots after liming, amylolytic activity and laminarinolytic activity increased, while live body mass decreased. The enzymatic activity of enchytraeids depended on season and also indirectly on individual mean mass. Received: 12 February 1996     

Physiological responses of soybean (Glycine max L. Merr) to simulated acid rain and ambient ozone in the field

Physiological processes in field-grown soybean (Glycine max L. Merr. 'Davis’) to determine if plant responses were altered by simulated acid rain and if the responses to acid rain were modified by the presence of gaseous pollutants. Applications of simulated acid rain (pH 3.2, 4.2, and 5.2), alone or in combination with gaseous pollutants, did not significantly affect photosynthesis, transpiration, stomatal conductance of water vapor, or chlorophyll content at periodic intervals during the 1984 season. Furthermore, in leaf samples collected during pod fill, the concentrations of 11 elements were not significantly affected by simulated acid rain, alone or in combination with gaseous pollutants. These data are evidence that combinations of ambient rain and gaseous pollutants at similar levels may not cause significant physiological disruption in field-grown Davis soybean, and provide mechanistic support for studies where no significant effects on yield were reported.     

Effects of ambient gaseous pollutants on photosynthesis,growth, yield and grain quality of selected crops grown at different sites varying in pollution levels

In recent decades, ambient gaseous pollution has increased due to anthropogenic activities worldwide. The studies to evaluate the adverse effects of ambient pollutants on commonly grown food crops are still limited, especially in Asian countries like Pakistan. The present study was conducted to measure the ambient pollutants in different sites of Faisalabad and their impact on growth and yield of wheat, mung bean and peas. Plants were grown in pots and placed at three sites named as control (Wire house of Government College University, Faisalabad), low pollution (LP) (Farm Area of Ayub Agricultural Research Institute) and high pollution (HP) (GT Chowk, Faisalabad) sites. Results showed that ambient ozone (O₃) concentration was highest at HP site followed by LP site and was below AOT40 in control site. Ambient pollutants caused foliar injury in crops and decreased plant height, leaf area, biomass and grain yield. Pollutants caused a reduction in photosynthetic pigments, stomatal conductance and net photosynthetic rate and grain protein contents in all three crops. In conclusion, the ambient O₃ level was highest at HP site, this current O₃ level and other pollutants decreased the growth and yield of important food crops.     

The effect of simulated acid rain on feather mosses and lichens of the boreal forest

Permanent field plots containing a dominant ground cover of feather moss (Pleurozium schreberi) and the forage lichen, (Cladina), were established in mature, boreal forest jack pine stands to monitor the effects of simulated acid precipitation. For a five-year period commencing in 1981, bimonthly sprays (pH range 2.5 to 5.6) were given throughout the growing season. The feather moss wefts were extremely sensitive to simulated rains of pH 2.5 and 3.0; but loss of cover and frond blackening were also observed at pH 3.5. The pH 2.5 treatment killed almost all of thePleurozium, while the cover remaining in the pH 3.0 treatment after 5 years was reduced by 44%. In laboratory studies designed to compare the effects of H₂S0₄, HN03 and a 2:1 mixture of both, microcosms sprayed with H₂S0₄ alone (pH 3.0) were more significantly affected than fronds treated with HN0₃ alone or pH 5.6 sprays of any ratio. Although less sensitive thanPleurozium, field-sprayed lichens were also visibly damaged. At pHs less than 3.5,C. stellaris andC. rangiferina had reduced podetial height and dry weight; whileC. mitis was affected by a combination of the acid rain treatment and other associated factors. While ambient rains of pH 4.2 may not in themselves be harmful to the boreal ground flora, it is apparent that the feather mosses and lichens, lacking a cuticle and true roots, are very sensitive to occasional, extremely acidic rain events.     

Chemical response of soil leachate to alternative approaches to experimental acidification

Abstract

One approach to evaluating computer models which predict terrestrial‐aquatic ecosystem response to acid deposition is the experimental acidification of soils with subsequent comparisons among predicted and measured soil solution response. Using a soil microcosm experimental approach, comparisions between simulated acid rain (i.e. dilute H₂SO₄), dry NH₄NO₃, and prilled reduced S were made for suitability for large‐scale field experiments. Soil microcosms consisting of reconstructed soil profiles received a background simulated throughfall dosing over the six month treatment period. Results indicated that simulated throughfall, applied at twice the ambient rate, acidified soil leachates approximately 0.5 pH units over the treatment period. Along with the decline in leachate pH was an apparent release of base cations as well as Fe and Al. Over the length of the treatment period, very little of the prilled S dissolved and the simulated acid rain treatment did not have significant effects on leachate chemistry.     

Chemical Composition of Precipitation, Throughfall and Soil Solutions at Two Forested Sites in Guangzhou, South China

Rain water at two forested sites in Guangzhou (south China) show high concentrations of SO₄ ^2?, NO₃ ^? and Ca²⁺ and display a remarkable seasonal variation, with acid rain being more important during the spring and summer than during the autumn and winter. The amount of acid rain represents about 95% of total precipitation. The sources of pollutants from which acid rain developed includes both locally derived and long-middle distance transferred atmosphere pollutants. The seasonal variation in precipitation chemistry was largely related to the increasing neutralizing capacity of base cations in rainwater in winter. Soil acidification is highlighted by high H⁺ and Al³⁺ concentrations in soil solutions. The variation in elemental concentration in soil solution was related to nitrification (H⁺, NH₄ ⁺ and NO₃ ^?) and cation exchange reaction (H⁺, Al³⁺) in soil. The negative effect of soil acidification is partly dampened by substantial deposition of base cations (Ca²⁺, Mg²⁺ and K⁺) in this area.     

Project rain: Changing acid deposition to whole catchments. The first year of treatment

Project Rain (Reversing Acidification In Norway) is a 5-yr international research project aimed at investigating the effect on water and soil chemistry of changing acid deposition to whole catchments. The project comprises 2 parallel large-scale experimental manipulations -- artificial acidification at Sogndal and exclusion of acid rain at Risdalsheia. Treatment at Sogndal commenced April 1984 with the acidification of the snowpack by addition of H₂SO₄ (SOG2) and a 1:1 mixture of H₂SO₄ and HNO₃ (SOG4). Preliminary results indicate rapid and significant response in runoff chemistry to the acid treatment; pH decreased (to as low as 4.1 during snowmelt in 1984); SO₄, NO₃, and labile Al increased. Response during snowmelt 1985 was modest relative to 1984. At Risdalsheia treatment began in June 1984 with the mounting of the transparent panels on the roofs at KIM catchment (treatment by deacidified rain) and EGIL catchment (control with ambient acid rain). Preliminary data for the first year indicate that most runoff samples from KIM contain much lower NO₃ concentrations, about 20 to 30% lower SO₄ levels and pH 0.1 to 0.3 units higher than runoff from EGIL catchment. The treatments continue in 1985–87. Project RAIN provides experimental evidence bearing on target loading, reversibility of acidification, and the processes linking acid deposition, soil acidification and freshwater acidification.     

Estimating heterotrophic and autotrophic soil respiration using small-area trenched plot technique: Theory and practice

The trenching method of root exclusion is generally used to estimate heterotrophic (microbial decomposition) (F_h) and autotrophic (root and associated rhizosphere respiration) (F_a) components of soil respiration (F₀), particularly in forest ecosystems. However, some uncertainties exist on the accuracy and interpretation of the results from such experiments using small-area root exclusion plots. Using field and laboratory measurements as well as simulations using a process-based model of CO₂ production and transport in soil, we show that: (a) CO₂ concentrations at or immediately below the depth of root exclusion in small-area root exclusion plots are similar to those at the same depth in nearby undisturbed soil and (b) the contribution of soil CO₂ flux from below the root exclusion depth to the measured efflux at the surface of a root exclusion plot (F_0re) is increased because of the higher concentration gradient at the bottom of the root exclusion layer due to the decreased rate of CO₂ production above this depth. Consequently, F_a, calculated as F_0c measured in control (non-disturbed) plots minus F_0re measured in root exclusion plots, is underestimated. We describe an analytical model, derived from the soil CO₂ production and diffusion equation, to obtain correct estimates of F_a measured using small-area root exclusion plots. The analytical model requires knowledge of depth distribution of soil CO₂ diffusivity and source strength as inputs.     

Prolonged simulated acid rain treatment in the subarctic: Effect on the soil respiration rate and microbial biomass

Humus chemistry and respiration rate, ATP, ergosterol, and muramic acid concentration as measures of chemical properties, microbial activity, biomass, and indicators of fungal and bacterial biomass were studied in a long-term acid rain experiment in the far north of Finnish Lapland. The treatments used in this study were dry control, irrigated control (spring water, pH 6), and two levels of simulated acid rain (pH 4 and pH 3). Originally (1985–1988), simulated acid rain was prepared by adding both H₂SO₄ and HNO₃ (1.9:1 by weight). In 1989 the treatments were modified as follows. In subarea 1 the treatments continued unchanged (H₂SO₄+HNO₃ in rain to pH 4 and pH 3), but in subarea 2 only H₂SO₄ was applied. The plots were sampled in 1992. The acid application affected humus chemistry by lowering the pH, cation exchange capacity, and base saturation (due to a decrease in Ca and Mg) in the treatment with H₂SO₄+HNO₃ to pH 4 (total proton load over 8 years 2.92 kmol ha^-1), whereas the microbial variables were not affected at this proton load, and only the respiration rate decreased by 20% in the strongest simulated acid rain treatment (total proton load 14.9 kmol ha^-1). The different ratios of H₂SO₄+HNO₃ in subareas 1 and 2 did not affect the results.     

The Effect of Air Pollution on Yield and Quality of Mung Bean Grown in Peri-Urban Areas of Varanasi

There is growing concern that air pollution may have adverse impacts on crops in developing countries, yet this has been little studied. This paper addresses this issue, for a major leguminous crop of the Indian sub continent, examining the effect of air pollution in and around an Indian city. A field study was conducted using a gradient approach to elucidate the impact of air pollutants on selected production characteristics of Vigna radiata L. cv. Malviya Jyoti (mung bean) plants grown from germination to maturity at locations with differing concentrations of air pollutants around peri-urban and rural areas of Varanasi. The 6 -h daily mean SO₂, NO₂ and O₃ concentrations varied from 8.05 to 32.2 ppb, 11.7 to 80.1 ppb and 9.7 to 58.5 ppb, respectively, between the sites. Microclimatic conditions did not vary significantly between the sites. Changes in plant performance at different sites were evaluated with reference to ambient air quality status. Reductions in biomass accumulation and seed yields were highest at the site experiencing highest concentrations of all three gaseous pollutants. The magnitude of response indicated that at peri-urban sites SO₂, NO₂ and O₃ were all contributing to these effects, whereas at rural sites NO₂ and O₃ combinations appeared to have more influence. The quality of seed was also found to be negatively influenced by the ambient levels of pollutants. It is concluded that the air pollution regime of Varanasi City causes a major threat to mung bean plants, both in terms of yield and crop quality, with serious implications for the nutrition of the urban poor.     

Studies on Atmospheric Pollution,Acid Rain and Emission Control for their Precursors in Chongqing,China

Chongqing City in China has suffered from serious air pollution and acid rain caused by low graded raw coal (sulfur=ca. 3≈5%, ash=ca. 30%) combustion. In this paper, the situation of atmospheric pollution and acid rain in Chongqing are discussed, the reduction efficiency for sulfur dioxide (SO₂) with the bio-briquetting of the raw coal that is one of countermeasures for emission control of air pollutants due to domestic consumes was determined. The research indicated that the frequency of acid rain was high, more than 50% at urban area, and its pH was low, about 4.5. Under our experimental conditions, the reducing efficiency of sulfur SO₂ emission from high sulfur coal-biomass briquette amounted to 87%. The field investigation indicated that SO₂ indoor concentrations in case of using bio-briquette dropped to 1/2≈1/3 of the raw coal.     

Growth and gas exchange of loblolly pine seedlings as influenced by drought and air pollutants

One-year-old loblolly pine seedlings were exposed to 0₃(≤0.025 or 0.10 μ L L^?1, 4 hr d^?1, 3 d wk^?1) in combination with simulated rain (pH 5.6 or 3.0, 1 hr d^?1, 2 d wk^?1, 0.75 cm hr^?1) for 10 wk. After the 10-wk treatment, the seedlings were submitted to two drought cycles, and water potential, net photosynthesis (Pn), and transpiration (Tr) were measured. Whole-plant fresh weight increment and relative growth rate were significantly increased in seedlings exposed to simulated rain at pH 3.0 compared to pH 5.6. An interaction between 0₃ and simulated rain occurred in height growth. Shoot height elongation was significantly less in seedlings exposed to 0.10 μL L^?1 0₃ + pH 5.6 than in any other pollutant combination after the 10-wk treatment period. There were no significant effects of 0₃ on Pn and Tr prior to the drought cycles; however, after the first drought cycle, Pn was significantly higher in seedlings pre-exposed to 0.10 μL L^?1 0₃ compared to the low 0₃ concentration. The 10-wk treatment with simulated rain at pH 3.0 significantly increased Pn and Tr. The relationship between gas exchange rates and needle water potential during the moisture stress period was affected by preexposure to pollutants. In general, Pn and Tr were more sensitive to decreasing needle water potential in seedlings exposed to pH 3.0 during the first drought cycle and to 0.10 μL L^?1 0₃ during second drought cycle.     

Effect of simulated acid rain on mycorrhizal infection of Pinus strobus L.

Mycorrhizal infection but not growth of white pine seedlings was reduced by application of simulated rain at pH 3.5 at 3 times ambient rates to plants grown in steamed Mardin soil inoculated with Pisolithus tinctorius. In unsteamed Mardin soil, the simulated acid rain at 3 times ambient rates had no effect on mycorrhizal infection or growth of pine seedlings if the rain was applied to the plants and soil or to only the soil before planting, except that nitrate-containing acid rain increased growth, infection and N content. In limed Mardin soil, the simulated acid rain reduced mycorrhizal infection if applied to the plants and soil as the seedlings were growing but not if applied to the soil before planting. Application of pH 3.5 rain at ambient rates had no detectable influence on mycorrhizal infection in 6 of 9 soils tested, but it stimulated infestion in 3 soils if the simulated rain contained only sulfate and in 1 soil if it had both sulfate and nitrate.     

Effects of simulated acid rain on the growth,nutrition, foliar pigments and photosynthetic rates of sugar maple and white spruce seedlings

Sugar maple (Acer saccharum Marsh.) and white spruce (Picea glauca (Moench) Voss) seedlings were exposed to simulated acid rain (SAR) of pH 3.2, 4.3 and 5.6 for two and one-half growing seasons. Ambient rain was excluded from the treatment plots by mobile rain exclusion canopies. Sugar maple seedlings treated with pH 3.2 SAR had significantly higher foliar concentrations of nitrogen, sulphur and manganese, compared to either the pH 4.3 or 5.6 treated seedlings. The pH 3.2 treated seedlings also tended to have greater growth and photosynthetic rates compared to the pH 4.3 and 5.6 treated seedlings. In contrast, the pH 3.2 treated white spruce seedlings tended to have decreased growth and lower foliar potassium concentrations relative to the pH 4.3 and 5.6 treated seedlings. Statistically there were no significant treatment differences in seedling height, seedling diameter, foliar pigments, or photosynthetic rates in either the sugar maple or white spruce seedlings.     

Simultaneous inhibition of CH4 efflux and stimulation of sulphate reduction in peat subject to simulated acid rain

Acid rain sulphate (SO₄²⁻) deposition is a known suppressant of methane (CH₄) emission from wetlands. However, the hypothesised mechanism responsible for this important biogeochemical interaction, competitive exclusion of methanogens by dissimilatory SO₄²⁻ reducing bacteria (SRB), lacks supporting evidence. Here, we present data from an acid rain simulation experiment in the Moidach More peat bog of NE Scotland that strengthens this hypothesis. We report a tenfold increase in estimated SO₄²⁻ reduction during periods when measured CH₄ emission rates were suppressed relative to controls receiving only one-tenth the SO₄²⁻ of treated plots, but no treatment effect on potential methane oxidation. This tenfold increase in estimated SO₄²⁻ reduction indicates the presence of a more active population of SRB in plots where CH₄ emissions were reduced by over 30%.     

Reduction in soybean yield after exposure to ozone and sulfur dioxide using a linear gradient exposure technique

A linear gradient field exposure system was modified from one originally described by Shinn et al. (1977) and used to expose field grown soybeans (Glycine max cv Hark) to a concentration gradient of a mixture of two gaseous pollutants: SO₂ and 0₃. Since this technique does not use enclosures, study plants experienced near ambient fluctuations in environmental conditions, including wind, and hence were exposed to widely fluctuating pollutant concentrations. Plants in the gradient system were exposed to both pollutants for 57 h on 12 days during the pod-filling period (31 August–17 September). Mean concentrations during the 57 h of exposure at the ‘high’ end of the gradient were 0.16 and 0.06 µl l^?1 (PPM) SO₂ and O₃, respectively, with 10 h at greater than 0.25 and 0.10 µl^?1 SO₂ and O₃, respectively. Total doses for these plants were estimated to be 9.0 and 3.5 µl^?1 · h SO₂ and O₃, respectively. Comparison with plants exposed to ambient air indicated that exposure to SO₂ and O₃ reduced total yield per plant and dry mass per bean by as much as 36 and 15 %, respectively. Since concurrent exposure to a much higher dosage of SO₂ alone (20.2 µl l^?1 · h) was observed in a separate experiment to have no significant effect on yield, 03, although present at moderately low levels, was probably responsible (alone or synergistically with SO₂) for the greatest reduction in seed size and yield.     

Impacts of acid precipitation on coniferous forest ecosystems

This paper summarizes the results from current studies in Norway. One main approach is the application of artificial acid ‘rain’ and of lime to field plots and lysimeters. Application during two growth seasons of 50 mm mo^?1 of ‘rain water’ of pH 3 to a podzol soil increased the acidity of the humus and decreased the base saturation. The reduction in base saturation was mainly due to leaching of Ca and Mg. Laboratory experiments revealed that decomposition of pine needles was not affected by any acid ‘rain’ treatment of the field plots. Liming slightly retarded the decomposition. No nitrification occurred in unlimed soils (pH 4.4-4.1). Liming increased nitrification. The soil enchytraeid (Ohgochaeta) fauna was not much affected by the acidification. Germination of spruce seeds in acidified mineral soil was negatively affected when soil pH was 4.0 or lower. Seedling establishment was even more sensitive to increasing soil acidity. Analysis of throughfall and stemflow water in southernmost Norway reveals that the total deposition of H₂SO₄ beneath spruce and pine is approximately two times the deposition in open terrain. A large part of this increase is probably due to dry deposition. Increased acidity of the rain seems to increase the leaching of cations from the tree crowns. Tree-ring analysis of spruce (Picea abies (L.) Karst.) and pine (Pinus sylvestris L.) has been based on comparisons between regions differently stressed by acid precipitation and also between sites presumed to differ in sensitivity to acidification. No effect that can be related to acid precipitation has yet been detected on diameter growth.     

Atmospheric Concentrations of Sulfur Dioxide and Nitrogen Dioxide in China and Korea Measured by Using the Improved Passive Sampling Method

The results of ambient sulfur dioxide (SO₂) and nitrogen dioxide (NO₂) concentrations measured in ten cities of China and Korea by the improved passive samplers are reported. The property of this sampler is the utilization for the long-term exposure to the high level of SO₂ and NO₂. In this method, the conversion coefficients from the analytical data to the ambient concentrations were obtained from the comparison with the direct concentrations through the automatic analyzers for SO₂ and for NO₂, respectively. The interesting monthly variations were observed in the ambient SO₂ and NO₂ concentrations measured by this passive sampler method, which seems to give important information to the formation of acid rain in these countries.     

Simulated Acid Rain Leaching Characteristics of Acid Soil Amended with Bio-Briquette Combustion Ash

In Chongqing City, the rapid growth of the economy has accompanied an increase of sulfur dioxide emissions from coal combustion, bringing about an expansion of acid rain affected areas and acidification of soil. Recently, we reported that coal-biomass briquettes so-called bio-briquettes (BB), which are produced from pulverized raw coal, biomass, and a sulfur fixation agent (Ca (OH)₂) under 3 to 5 tons cm^?2 pressure, have high sulfur-fixation efficiency. The BB ash contains nutritive substances such as Ca and Mg, and has a large acid-neutralizing capacity. Thus, in order to improve the acid soil in the Chongqing area, we analyzed the chemical composition of the original acid soil and the ash-amended soil, and investigated their leaching characteristics under simulated acid rain (SAR). It was found that plants and crops in Chongqing area would be injured if the present acid rain continues. We carried out a SAR leaching experiment and studeid the potential toxic effects of leachate from soil containing added ash. The results indicated that the contents of most toxic elements, with the sole exception of chromium, were below the environment standard for irrigation water. Because the BB ash was highly alkaline, the leaching aluminum (Al) species would be hydroxide rather than free Al³⁺ ion.     

A study to determine effects of simulated acidic rain on yield of field-grown soybeans (Glycine max. cv. Hodgson)

A field study was conducted in 1985 and 1986, using a fully automated rain exclusion canopy system, to investigate the impact of simulated acidic rain (SAR) on yield of soybean (Glycine max cv. Hodgson). Treatment effects were determined for various yield components: seed yield (kg ha^?1), pod number per plant, seed number per pod, seed weight (g 100 seeds^?1). Plant height (cm) was also measured. Results of the 1985 fields study showed that increased acid content of SAR had a slight stimulatory effect on soybean seed yield. However, the 1986 study results did not show significant treatment effects on seed yield (kg ha^?1) or other components of yield. For each of five SAR treatments, soybean yield (kg ha^?1) obtained in 1985 was significantly greater than the 1986 yield. The yield results can be attributed to differences in seed weight caused by environmental conditions specific to the two growing seasons.