Atmospheric deposition and ionic interactions within a beech canopy in the Karkonosze Mountains

A method, of artificial foliage placed above rain collectors, which enables to estimate total atmospheric inputs of elements, was employed to study processes related to ionic flow through a tree canopy. The investigations were conducted within a beech forest in the Karkonosze Mountains, in 1996-1997. An analysis of net canopy exchange (throughfall flux-atmospheric input) revealed that NH4+, NO3-, H+ had been retained in the canopy, Ca2+, Na+, Cl-, SO(2-)4, PO(3-)4 flowed passively, whereas K+ and Mg2- had been removed from the tree foliage. Ammonium absorption was more efficient than that of NO3- ions, because NH4+ was taken up from rain-waters and aerosol-gaseous fraction of the atmospheric input, whereas NO3- ions were captured primarily from the latter source. Retention of H+ was also related exclusively to the aerosol-gaseous input. Leaching losses of K+ and Mg2+ did not result from exchange reactions of these ions with retained H+, but from ionic exchange between NH4+ and K+ + Mg2+. At the same time, neutralisation of H+ in the canopy has been attributed to NO3- absorption, resulting most likely from HNO3 vapour penetration into the plants.     

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.     

Sulphur dioxide adsorption in Scots pine canopies exposed to high ammonia emissions near a Cu-Ni smelter in SW Finland

Since 1994 the nickel-processing plant at the Cu-Ni smelter at Harjavalta, south-west Finland, has emitted considerable amounts of NH(3) into the atmosphere. The effects of NH(3) emissions on nitrogen and sulphur deposition in throughfall and the foliar nutrient status were investigated in a Scots pine stand at 0.5 km distance. Bulk deposition, stand throughfall and percolation water (20 cm depth) samples were collected at 4-week intervals during 1992-1998. pH and the Ca, Mg, K, NH(4) and SO(4) concentrations were determined on the samples. NH(3) emissions have strongly increased the scavenging of SO(2) from the air in the pine stand, and the increased levels of N and S deposition were clearly evident as increased foliar N and S concentrations and larger needle size. The increased input of SO(4) into the forest floor was not associated with an increase in the leaching of Ca and Mg from the surface soil layers.     

Contribution of canopy leaching to sulphate deposition in a Scots pine forest

Radioactive sulphate (35SO4) was applied to the soil below a Scots pine forest on 23 June 1989, and its movement into the canopy and into throughfall and stemflow was measured over 4 months. The specific activity, Bq (mg S)(-1), of the canopy increased monotonically; uptake by current-year (1989) expanding needles was initially twice as fast as by older needles or live twigs. By 10 October the canopy average specific activity was 62 Bq (mg S)(-1). The specific activity of net throughfall (throughfall + stemflow - rain), deduced from measurements from six throughfall collectors, six stemflow collectors and two rain collectors, fell rapidly from 12.6 Bq (mg S)(-1) in late July to <1 Bq (mg S)(-1) in mid-August. The results suggest (assuming rapid equilibration of 35S with sulphate in soil) that root-derived sulphate contributed c. 3% of sulphate in net throughfall and that dry deposition of SO2 and sulphate particles contributed c. 97% of the 0.56 g S m(-2) measured in net throughfall over the period. Simultaneous measurements of SO2 at canopy height and of NH3 above and within the canopy gave mean concentrations of 5.9 and 0.86 microg m(-3), respectively, sufficient to account for the sulphate measured in net throughfall only if codeposition of NH3 and SO2 occurred to canopy surfaces. The large values of specific activity observed in July, however, indicate that throughfall composition may be closely related to recent soil input of sulphate, and that equilibrium cannot be safely assumed. The possibility of a significant contribution of soil-derived sulphate to sulphate deposition in net throughfall cannot be ruled out on the basis of this experiment.     

Atmospheric input of elements to forest ecosystems: a method of estimation using artificial foliage placed above rain collectors

Usefulness of a method of artificial foliage was tested for estimation of total ionic inputs from the atmosphere to forest ecosystems, as well as of processes relevant to ionic fluxes through tree canopies: uptake, leaching, passive flow. The studies were performed in Norway spruce and European beech stands in Karkonosze Mountains (Poland), in 1995-97. Artificial leaves of increasing leaf area index: 0, 2, 6 and 12 m(2) m(-2 )were placed above standard rain collectors. It has been found that total atmospheric fluxes of H(+), NH(4)(+), Ca(2+), Mg(2+), Pb(2+), NO(3)(-) and SO(4)(2-) rose as surface area of the foliage increased. This was especially true for nitrate, sulphate and ammonium. No such relationship was found for K(+), Na(+), Zn(2+), Cd(2+), Cu(2+) and PO(4)(3-). The increase in anion fluxes exceeded that in neutralising cations (NH(4)(+), Na(+), K(+), Mg(2+), Ca(2+)) and led to progressive rainwater acidification with the increase in the foliage area. An analysis of net canopy exchange (atmospheric input-throughfall flux) has shown that SO(4)(2-), PO(4)(3-), Na(+), Ca(2+) and Cu(2+) flowed passively through the tree crowns; NH(4)(+), NO(3)(-), Zn(2+), Cd(2+) and occasionally Pb(2+) were efficiently absorbed, whereas K(+) was leached from the canopies. Beech was more effective in modifying ionic pool from the atmosphere than spruce. This related to H(+) (greater absorption) and Mg(2+) (greater leaching). It has been demonstrated that the results concerning trends in net canopy exchange and produced by the simple method of artificial foliage are comparable to more sophisticated techniques of the measurements. This proves the method to be useful.     

Effect of simulated acid rain on quantity of epiphytic microfungi on Scots pine (Pinus sylvestris L.) needles

The effects of simulated acid rain on the phyllosphere microflora of pine (Pinus sylvestris L.) were studied experimentally in northern Finland during the summer of 1988. Trees were irrigated with artificial acid rain of pH4 and pH3 (H(2)SO(4) and HNO(3), weight ratio of S:N=2.86:1). Untreated trees and trees irrigated with spring water (pH6) were used as controls. Two sampling heights (0.5m and 2m) were used. The needles were colonized exclusively by epiphytic fungi, mainly Aureobasidium pullulans (de Bary) Arnaud. The lower branches had significantly more epiphytic fungi than the upper branches. Compared to the control trees, the numbers of epiphytic fungi were significantly decreased on the needles of trees irrigated with acid rain. Acid rain affected the number of epiphytic fungi equally at both sampling heights. The species composition of the epiphytic fungi was not affected by the acid treatments.     

Limited compensation of ozone stress by potassium in Norway spruce

The effects of potassium fertilization and ozone stress were investigated in a clone of Picea abies (L.) Karst, by studies of the uptake of CO(2) by the crowns, the element content, on leaching of the youngest needles, and the longevity of the needles. All plants were exposed to 0.075 microl litre(-1) SO(2) from January to April 1986. The average ozone concentrations applied during the subsequent growing season (May-December) were 0, 0.027, 0.050 and 0.100 microl litre(-1). Half of the trees received liquid fertilizer applications from April to July 1986. CO(2) uptake by the crowns was significantly reduced in non-fertilized plants at ozone doses of 100-200 microl litre(-1) h, whereas similar reductions were recorded in fertilized plants only above an ozone dose of 300 microl litre(-1) h. Independent of the fertilization, however, the concentrations of calcium, magnesium and nitrogen in the needles increased in parallel with the ozone dose, whilst potassium, phosphorus and sulphur showed little response to ozone. In both nutrient regimes, the diffusive loss of elements from chloroform-washed needles was similar and tended to be reduced at the highest ozone concentration, when relating the leachate to the corresponding element content in the needles. Needles formed in the highest ozone treatment were significantly shed during the succeeding year, regardless of the nutrient supply. It appears that increased potassium supply has little compensating effect on ozone stress in spruce.     

Acidification of a Solonetzic soil by nitrogenous fertilizers

Annual applications of (NH4)2SO4, NH4NO3 and urea on a Solonetzic soil at 112 kg N/ha for 10 consecutive years reduced pH levels from 5.6 for the check to 4.4, 4.9 and 5.3, respectively for (NH4)2SO4, NH4NO3 and urea. (NH4)2SO4 generated twice as much exchange acidity as NH4NO3 and four times as much as urea. Net extractable cations leached from the Ap horizon closely approximated the amount of exchange acidity generated by (NH4)2SO4 and NH4NO3 fertilizers. The levels of soil extractable Al and Mn were greatly enhanced by (NH4)2SO4 as were plant contents. Similar acidifying effects to that produced by the (NH4)2SO4 occurred when NH4NO3 was applied at 300 kg N/ha annually for 12 consecutive years in another field experiment on the same soil. Liming samples of the field (NH4)2SO4 acidified soils in the greenhouse, significantly increased yields and lowered the Al and Mn contents of the plants to normal levels.     

Seasonal variation in the atmospheric deposition of inorganic constituents and canopy interactions in a Japanese cedar forest

The seasonal changes in throughfall (TF) and stemflow (SF) chemistry and the canopy interactions of K+ and N compounds were studied in a Japanese cedar forest near the Sea of Japan. The fluxes of most ions, including non-sea-salt SO4(2-), from TF, SF, and rainfall showed distinct seasonal trends, increasing from autumn to winter, owing to the seasonal west wind, while the fluxes of NH4+ and K+ ions from TF+SF might have a large effect of canopy interactions. The contact angle (CA) of water droplets on leaves decreased with leaf aging, suggesting that surface wettability increases with leaf age. The K+ concentration in TF was negatively correlated with the CA of 1-year-old leaves, while the NH4+ concentration was positively correlated with the CA. The net fluxes of NH4+ and NO3(-) from TF were positively correlated with the CA. The increase in wettability may accelerate leaching of K+ or uptake of NH4+.     

Combined use of open-air and indoor fumigation systems to study effects of SO2 on leaching processes in Scots pine litter

Both an open-air fumigation system and a laboratory-based system were used to expose decomposing Scots pine (Pinus sylvestris L.) needles to controlled concentrations of SO(2) (arithmetic mean 相似文献   

Mineral content in the soil and tree foliage

Seedlings of fir (Abies alba Mill.) and spruce (Picea abies L. Karst.) were fumigated with SO(2), O(3) and SO(2) + O(3) in open-top chambers (OTCs) for almost 5 vegetation periods. As background stress, simulated rain of pH 4.0 was applied. Nutrient content of soil, soil solutions, and trees was investigated and balanced. In the upper partition of the soil high concentrations of exchangeable Ca(2+) were found in all chambers. The SO(2) and SO(2) + O(3) treatments led to increased Ca(2+), Mg(2+) and Mn(2+) concentrations in soil solution and the pool of exchangeable protons increased. This response was most evident in the SO(2) and SO(2) + O(3) chambers and less clear in the filtered pH 5.0 control chamber. In the SO(2) treatment increased Mn and S levels were found in the needles. Ca content in the needles showed a decreasing trend. O(3) alone had no consistent effect on needle nutrient content.     

Chlorophyll, carotenoids and the activity of the xanthophyll cycle

Clone spruce trees (Picea abies L. Karst.) were exposed in the Hohenheim open-top chambers to low levels of O(3) and SO(2), singly and in combination, and to simulated precipitation of two pH treatments (Seufert et al., this volume). At the end of five years of continuous exposure, needles from the 13-year-old trees were sampled and analysed for pigments content by means of HPLC (high pressure liquid chromatography). The pigment content was determined for three needle age classes. Chlorophyll a content, measured on a dry weight basis, was similar for all needle age classes in the control chambers receiving only the simulated rain treatments at pH 5.0 or 4.0, and the chamber receiving O(3) and the rain treatment at pH 4.0. Also, no differences were noted in one-year-old needles in the chambers with SO(2) and simulated precipitation at pH 4.0 and SO(2) + O(3) and simulated precipitation at pH 4.0. Reductions of approximately 10 and 35% were measured in two-year-old needles from the chambers with SO(2) and precipitation at pH 4.0, and SO(2) + O(3) and precipitation at pH 4.0. The three-year-old needles from these chambers had 40% lower chlorophyll a content compared to the control chambers. No treatment effects were seen on the molar ratios of chlorophyll b, the carotenes, lutein, neoxanthin, and the sum of carotenoids involved in the xanthophyll cycle, violaxanthin + antheraxanthin + zeaxanthin, to chlorophyll [Formula: see text]. The xanthophyll cycle, assayed in one-year-old needles under defined light conditions (520 microE m(-2) s(-1), while light) was active in all samples. Needles from the control chambers and the chambers with SO(2) and with O(3) behaved similarly and differed from the SO(2) + O(3) treated needles by a 50% higher zeaxanthin content reached under light.     

Caesium selectivity and fixation by vermiculite in the presence of various competing cations

Caesium selectivity coefficients (k(G)) that were determined with respect to Na-, Mg-, Ca-, Sr- and Ba-ions, for Kent and Libby vermiculites,ranged from 4.8 to 11 (litres/mol) [Formula: see text], much higher than those with respect to K- and NH(4)-ions (0.01 to 0.06), indicating the high affinity of vermiculite for the weakly hydrated cations. Higher K(G) values were also found for low and extremely low Cs concentrations. Vermiculite samples were very effective in removing (137)Cs from solutions containing traces of (137)Cs (4 ng litre(-1)) and extremely higher quantities of K-, NH(4)-, Na-, Mg- and Ca-ions (500 mg litre(-1)). 0.5N chloride solutions of H, NH(4), K, Na, Mg and Ca were unable to remove Cs from Cs-saturated v vermiculite samples which had undergone heating at 110 degrees C. Significant quantities (50-65%) of fixed Cs were removed from these samples only after treatment with strong acids. The high preference and fixing ability of vermiculite for Cs suggests the use of this mineral as a radioactive Cs decontaminating agent.     

Effects of ozone on foliar leaching in Norway spruce (Picea abies L. Karst): confounding factors due to NOx production during ozone generation

Previous experiments with conifers fumigated with O(3), produced by air-operated electric discharge ozonators, have provided evidence that O(3) increases the leaching of NO(3)(-), NH(4)(+), K(+), Ca(2+), Mg(2+) and some other cations from needles, when the trees are treated with acid mist. This evidence has provided the foundation of the ozone-acid mist hypothesis of spruce decline. We report experiments with Norway spruce saplings fumigated with purified and unpurified O(3). The results show that the accumulation of NO(3)(-) in the needles arises from the rapid deposition of N(2)O(5) and HNO(3) formed from N(2) in the ozonator. An increase in removal of NH(4)(+), Na(+), Ca(2+), Mg(2+), Zn(2+) and Mn(2+) from the needles during soaking in H(2)SO(4), pH3, was also observed, which was related to the increase in NO(3)(-) but was independent of O(3) concentration. It is concluded that results of previous experiments cited in support of the ozone-acid mist hypothesis arose from effects which were at least partly caused by N(2)O(5) produced as a contaminant, and were incorrectly attributed to ozone. Other effects, such as growth stimulations, visible symptons, enhanced frost sensitivity, and infestation by pests or pathogens, which have been attributed to O(3) generated by electric discharge in air, should be interpreted with caution. Future experiments with ozone must eliminate this problem by either using O(2)-driven ozonators, or by purifying the output from air-driven ozonators using cold and/or water traps.     

Effects of rhizobium, arbuscular mycorrhizal fungi and anion content of simulated rain on subterranean clover

An experiment was conducted to determine the extent to which rhizobia, mycorrhizal fungi, and anions in simulated rain affect plant growth response to acid deposition. Germinating subterranean clover seeds were planted in steam-pasteurized soil in pots and inoculated with Rhizobium leguminosarum, Glomus intraradices, Glomus etunicatum, R. leguminosarum + G. intraradices, R. leguminosarum + G. etunicatum, or no microbial symbionts. Beginning 3 weeks later, plants and the soil surface were exposed to simulated rain in a greenhouse on 3 days week(-1) for 12 weeks. Rain solutions were deionized water amended with background ions only (pH 5.0) or also adjusted to pH 3.0 with HNO3 only, H2SO4 only, or a 50/50 mixture of the two acids. Glomus intraradices colonized plant roots poorly, and G. intraradices-inoculated plants responded like nonmycorrhizal plants to rhizobia and rain treatments. Variation in plant biomass attributable to different rain formulations was strongest for G. etunicatum-inoculated plants, and the effect of rain formulation differed with respect to nodulation by rhizobia. The smallest plants at the end of the experiment were noninoculated plants exposed to rains (0.38 g mean dry weight total for 3 plants pot(-1)). Among nonnodulated plants infected by G. etunicatum, those exposed to HNO3 rain were largest, followed by plants exposed to HNO3 + H2SO4, pH 5.0, and H2SO4 rain, in that order. Among plants inoculated with both R. leguminosarum + G. etunicatum, however, the greatest biomass occurred with pH 5.0 rains, resulting in the largest plants in the study (1.00 g/3 plants). Treatment-related variation among root and shoot biomass data reflected those for whole-plant biomass. Based on quantification of biomass and N concentrations in shoot and root tissues, total N content of plants inoculated with G. etunicatum alone and exposed to the HNO3 + H2SO4 rains was approximately the same as plants inoculated with R. leguminosarum + G. entunicatum and exposed to pH 5 rains. Thus, the acid-mixture rains and rhizobia under no acid deposition provided approximately equal amounts of N in biomass. The significant interactions among rain formulation and the symbiotic status of the plants suggest that conclusions concerning the impact of acid deposition on plants in the environment cannot be considered reliable because most experiments on which such assessments are based have not tested confounding influences of microorganisms and precipitation characteristics.     

Organism-induced accumulation of iron, zinc and arsenic in wetland soils

Four year old spruce (Picea abies (L.) Karst.) seedlings were planted in sand pots and supplied with nutrient solution. Three groups were formed, differing only in manganese nutrition (0.5 ppm, 2.5 ppm, 12.5 ppm, respectively). After three months, five individuals of each group were transferred to a dew chamber. For the next seven weeks the trees were sprayed in the evenings, the relative humidity overnight was kept high and the droplets were collected directly from the needles in the mornings. The trees were sprayed with HNO3 (pH 3.4) during the first three weeks to reduce the natural buffering capacity of the needles. After this time, the trees were sprayed with KCl (1 mM) solution, and NaHSO3 was added to the chamber resulting in SO2 concentrations usually between 50 and 150 microg m(-3). Needles and water samples were analysed. Foliar Ca seemed to be only a short-time buffer even under optimal Ca supply. A highly significant influence of managanese supply on manganese in needles and droplets was observed, as well as on sulphate, H+ and calcium concentrations in the droplets. The SO2 flux to trees treated with 12.5 ppm Mn was about twice as high as to trees treated with 0.5 ppm Mn. The conclusion is that this is due to a synergism between manganese leaching and catalysis of the SO2 oxidation by the leached Mn2+ ions. The results suggest a positive feedback between (moderate) acidification of soils and SO2 and NH3 inputs to terrestrial ecosystems.     

Inorganic PM2.5 at a U.S. agricultural site

In this study, we present approximately two years (January 1999-December 2000) of atmospheric NH3, NH4+, HCl, Cl-, HNO3, NO3-, SO2, and SO4= concentrations measured by the annular denuder/filter pack method at an agricultural site in eastern North Carolina. This site is influenced by high NH3 emissions from animal production and fertilizer use in the surrounding area and neighboring counties. The two-year mean NH3 concentration is 5.6 (+/-5.13) microg m(-3). The mean concentration of total inorganic PM2.5, which includes SO4=, NO3-, NH4+, and Cl-, is 8.0 (+/-5.84) microg m(-3). SO4=, NO3-, NH4+, and Cl- represent, respectively, 53, 24, 22, and 1% of measured inorganic PM2.5. NH3 contributes 72% of total NH3 + NH4+, on an average. Equilibrium modeling of the gas+aerosol NH3/H2SO4/HNO3 system shows that inorganic PM2.5 is more sensitive to reductions in gas + aerosol concentrations of sulfate and nitrate relative to NH3.     

The effects of excess nitrogen deposition on young Norway spruce trees. Part II the vegetation

The effects of wet-deposited nitrogen on soil acidification and the health of Norway spruce were investigated in a pot experiment using an open-air spray/drip system. Nitrogen was applied as ammonium ((NH(4))(2)SO(4)) or nitrate (HNO(3)/NaNO(3)) in simulated rain to either the soil or the foliage. Symptoms of forest decline as observed in the field were not reproduced, and there was no evidence of direct toxicity. Treatments did, however, have significant effects on tree nutrition. Both NH(+)(4) and NO(-)(3) treatment applied to the foliage lowered foliar K concentrations. NH(+)(4) to a greater extent. Soil-applied NH(+)(4) reduced foliar Mg concentrations and increased foliar Al and Fe. Soil-applied NO(-)(3) significantly reduced foliar P concentrations, and at high doses prevented the alleviation of P deficiency by fertiliser. These effects could be important in some field situations. Ammonium deposition is predicted to be more damaging than nitrate deposition, although the latter may be critical for forests where P status is marginal, such as in parts of the British uplands.     

Artificial acidification of a non-acidic and an acidic headwater stream in Maine, USA

Two headwater streams with low DOC and different pHs (4.5-4.8 and 5-6.5) were acidified with H2SO4 to pH 4.1 and 4.5, respectively, for 24-h periods. Neutralization of the added acid occurred by protonation of ANC (HCO3-dominated in the higher pH stream), desorption of Ca (< 15 microeq litre(-1)) and Mg (<6 microeq litre(-1)), and desorption and dissolution of AL (<250 microg litre(-1)) from the stream bed. The concentrations of dissolved organic carbon (DOC) remained constant within the experimental reaches. The concentrations of Na, K an H4SiO4 also remained constant, indicating no detectable increase in the rate of chemical weathering in the stream bed. After acid addition was stopped, concentrations of Ca, Mg and Al decreased to below background, indicating reversible ion exchange as the principal mechanism for the mobility of Ca and Mg and to a lesser extent for Al. Repeated acidifications indicated that significant regeneration of cations on the exchange surfaces of the stream substrate occurs rapidly.     

Atmospheric deposition to the edge of a spruce forest in Denmark

Atmospheric deposition was measured during 1 year at the forest edge of a Norway spruce stand in Denmark. Inside the forest the deposition of H(+), Ca(2+), Mg(2+), Na(+), K(+), Cl(-), NO(3)(-), NH(4)(2) and SO(4)(2-) with canopy throughfall varies with the distance from the forest edge. The deposition at the edge is found to be 10-20 times as high as deposition to an open field and 2-8 times as high as deposition inside the stand. An exponential decrease in deposition as a function of the distance from the forest edge is found. Increased deposition of K(+) and non-sea salt Mg(2+), which mainly originates as a result of leaching from the needles may be explained by a larger leaf area index (LAI) at the forest edge. Deposition of particulate substances, especially Na(+), Cl(-), Mg(2+) and to some extent SO(4)(2-), NH(4)(+) and NO(3)(-) is increased much more than the LAI, which we believe to be caused by changes in wind movements at the forest edge.