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.     

Assessment of environmental impact zones in the Kola Peninsula forest ecosystems

This paper describes the condition of forest ecosystems subjected to smelter pollution in the Kola peninsula. This assessment is based on the parameters of the biogeochemical cycle. The defoliation index was used to delimit three basic forest states: background, defoliating, sparse. Close to the smelter, due to expansion of the area not covered by vegetation, a fourth type of state, so-called "industrial deserts", has been observed. The concentrations of sulphur, copper and nickel in the precipitation in the forests generally declined with distance from the smelter. The defoliating forests are noted for the highest Ca, Mg, K concentrations in the summer precipitation. In sparse forests and industrial deserts a decrease in the Ca, Mg, K concentrations in the summer precipitation in comparison with the defoliating forests, despite the particle emissions, could be attributed to the reduction in forest biomass. The higher levels of soil and soil leachate carbon and acidity in the defoliating forests was due to higher litterfall and to the higher dissolution of fulvic acids by the acidic precipitation. This increase in organic matter levels affects soil cation exchange capacity and cation saturation. The pine trees demonstrated significant changes in the uptake of elements in all types of forests under pollution. Elevated levels of S, Ni, Cu and K and reduced levels of Mg, Mn and Zn were found in the needles of different age classes.     

Influence of soil substrate and ozone plus acid mist on the frost resistance of young Norway spruce

The needles of clonal Norway spruce grown in environmental chambers on two different soils (an acidic soil 1 and a calcareous soil 2) and exposed to two levels of ozone fumigation (a low level combined with neutral mist = control, and an elevated one combined with acid mist = treatment) were analyzed for their frost hardiness. No effect of ozone was observed on either the development of frost resistance during the hardening phase or on the decrease in frost resistance during the dehardening phase. The preliminary results of Brown et al. (1987) and Barnes and Davidson (1988), which indicated that ozone treatment predisposes plants to winter injury, could thus not be confirmed. Frost resistance was, however, distinctly influenced by the content of the mineral nutrients of the soils. The pronounced K(+) deficiency of the needles of the trees growing on the neutral soil (Alps) had less effect on the development of frost resistance than did the Ca(++) and Mg(++) deficiency of the needles of the trees grown on the acidic soil 1 (Bavarian Forest). The variability of frost resistance between the different clones on soil 1 was partly attributed to fluctuations in the mineral nutrient content of the needles, rather than to a genetic predisposition.     

Heavy metal pollution and forest health in the Ukrainian Carpathians

The Ukrainian Carpathians are characterized by high air pollution caused by emissions from numerous industries. We have been monitoring the state of forests in this region since 1989. The highest levels of tree defoliation (>30%) are found close to industrial emission sources and in the upper mountain forests of the Ivano-Frankivsk and Chernivtsi regions. This is caused by a combination of strong anthropogenic influences (pollution, illegal uses, recreation) as well as poor site and climatic conditions. In the Ivano-Frankivsk region, Cd and Mo accumulate in forest soils; Cr, Mo and Zn soil concentrations are higher than their limit levels; and Pb concentrations exceed toxic levels close to industrial areas (10% of the region territory). Local background levels of heavy metals are greatly exceeded in snow close to industrial regions. Analysis of correlation matrices shows that the chemical elements Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, V and Zn occur at pollution levels in natural ecosystems in the Ukrainian Carpathians. Maximum concentrations of toxic elements occur in the oak forest zone; the most industrially developed area of the region. Toxic heavy metals in the Ukrainian Carpathians forests enter with precipitation and dustfall, then become fixed in soil and accumulate in leaves, needles of vascular plants and mosses. Concentrations of these metals decrease with altitude: highest in the oak forests, less in beech, and lowest in the spruce forest zones. However, some chemical elements have the highest concentrations in spruce forests; V in needles, As in snow, and Ba and Al in soils.     

Total vs. internal element concentrations in Scots pine needles along a sulphur and metal pollution gradient

Analysis of foliar elements is a commonly used method for studying tree nutrition and for monitoring the impacts of air pollutants on forest ecosystems. Interpretations based on the results of foliar element analysis may, however, be different in nutrition vs. monitoring studies. We studied the impacts of severe sulphur and metal (mainly Cu and Ni) pollution on the element concentrations (Al, Ca, Cu, Fe, K, Mg, Mn, Ni, P, Pb, S and Zn) in Scots pine (Pinus sylvestris L.) foliage along an airborne sulphur and metal pollution gradient. Emphasis was put on determining the contribution of air-borne particles that have accumulated on needle surfaces to the total foliage concentrations. A comparison of two soil extraction methods was carried out in order to obtain a reliable estimate of plant-available element concentrations in the soil. Element concentrations in the soil showed only a weak relationship with internal foliar concentrations. There were no clear differences between the total and internal needle S concentrations along the gradient, whereas at the plot closest to the metal smelter complex the total Cu concentrations in the youngest needles were 1.3-fold and Ni concentrations over 1.6-fold higher than the internal needle concentrations. Chloroform-extracted surface wax was found to have Ni and Cu concentrations of as high as 3000 and 600 microg/g of wax, respectively. Our results suggest that bioindicator studies (e.g. monitoring studies) may require different foliar analysis techniques from those used in studies on the nutritional status of trees.     

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.     

Air pollution, precipitation chemistry and forest health in the Retezat Mountains, Southern Carpathians, Romania

In the Retezat Mountains concentrations of O3, NO2 and SO2 in summer season 2000-2002 were low and below toxicity levels for forest trees. While NH3 concentrations were low in 2000, the 2001 and 2002 concentrations were elevated indicating possibility for increased N deposition to forest stands. More than 90% of the rain events were acidic with pH values <5.5, contributing to increased acidity of soils. Crown condition of Norway spruce (Picea abies) and European beech (Fagus sylvatica) was good, however, defoliation described as >25% of foliage injured increased from 9.1% in 2000 to 16.1% in 2002. Drought that occurred in the southern Carpathians between fall 2000 and summer 2002 and frequent acidic rainfalls could cause the observed decline of forest condition. Both Norway spruce and European beech with higher defoliation had lower annual radial increments compared to the trees with low defoliation. Ambient O3 levels found in the Retezat did not affect crown condition of Norway spruce or European beech.     

Fine roots in stands of Fagus sylvatica and Picea abies along a gradient of soil acidification

Root length of naturally grown young beech trees (Fagus sylvatica L.) was investigated in 26 forest plots of differing base saturation and nitrogen deposition. The relative length of finest roots (<0.25 mm) was found to decrease in soils with low base saturation. A similar reduction of finest roots in plots with high nitrogen deposition was masked by the effect of base saturation. The formation of adventitious roots was enhanced in acidic soils. The analysis of 128 soil profiles for fine roots of all species present in stands of either Fagus sylvatica L., Picea abies [Karst.] L. or both showed a decreased rooting depth in soils with < or =20% base saturation and in hydromorphic soils. For base rich, well drained soils an average rooting depth of 108 cm was found. This decreased by 28 cm on acidic, well drained soils. The results suggest an effect of the current soil acidification in Switzerland and possibly also of nitrogen deposition on the fine root systems of forest trees.     

Nitrate reductase activity of needles of Norway spruce fumigated with different mixtures of ozone, sulfur dioxide, and nitrogen dioxide

Four-year-old spruce clones (Picea abies (L.) Karst.) cultivated in sand and provided with a complete nutrient solution, or a solution deficient in magnesium and calcium, were exposed to the pollutant mixtures SO(2)/NO(2), O(3)/NO(2), and O(3)/SO(2)/NO(2), at realistic concentrations for 32 weeks. Fumigation caused a slight increase of total N contents in current year needles, whereas in one-year-old needles N concentrations did not change. The response of nitrate reductase activity to pollutant stress depended on needle age and nutrient supply, respectively. In one-year-old needles fumigation resulted in a significant inhibition of enzyme activity, particularly in Mg and Ca deficient trees. The combination of all three components proved to be most effective in causing a decrease by 60% compared to the control. In contrast, nitrate reductase activity was stimulated in current year needles, especially by O(3)/NO(2) and O(3)/SO(2)/NO(2). Changes in the activity of nitrate and nitrite reductases are considered as a factor contributing to the high phytotoxic potential of pollutant combinations with NO(2).     

Persistence and fate of polychlorinated biphenyls (PCBs) in sewage sludge-amended agricultural soils

Four metal enriched sewage sludges containing different concentrations of polychlorinated biphenyls (PCBs) were applied to two field soils in the UK in 1968. Samples of the sludges, sludge-amended soils and soils from untreated control plots were stored and analysed retrospectively. Sludge concentrations ranged from 1 to 7 mg SigmaPCB kg(-1). The pattern of PCBs was similar in three of the four sludges, with congeners 14, 18, 28 and 52 present at the highest concentrations. The fourth sludge contained higher amounts of congeners 149, 153, 138 and 180. SigmaPCB concentrations in control plot soil have declined over the last 20 years, indicating a reduction in atmospheric deposition inputs of PCBs to the soil. SigmaPCB concentrations also declined on the sludge-amended plots, reaching control plot concentrations (30-60 microg SigmaPCB kg(-1)) in the late-1980s. Half-lives ranged from < 1 to 8.5 years for congeners 18, 28 and SigmaPCB. Biodegradation and/or the formation of reversibly sorbed soil PCB residues could not account for the losses observed. Volatilisation is implicated as the most important loss process on both the control and sludge-amended plots. Using the fugacity approach, congener concentrations in soils at Luddington were predicted still to have not reached equilibrium with the air. Further losses to the atmosphere are likely.     

Crown condition of Norway spruce in relation to sulphur and nitrogen deposition and soil properties in southeast Norway

Atmospheric deposition of sulphur and nitrogen compounds may lead to enhanced leaching of base cations, accumulation of nitrogen in organic matter, lowered pH and increased concentration of toxic aluminium in soil, which in turn may affect the vitality of forest trees. A general monitoring of forest condition has been initiated in many European countries, partly in order to reveal stresses caused by acidification. However, forest condition is also affected by many other factors. This paper examines a seven-year series of crown-condition data from Local County Monitoring Plots in Norway spruce stands in Norway. Average, time trend and lability variables were calculated for crown density and crown colour for each plot. Wet deposition of sulphate, ammonium and nitrate for each plot were estimated using data from the national air and precipitation monitoring programmes. Soil data are based on soil sampling within the plots. The analysis gave no evident support for the hypothesized negative effect on crown condition from sulphur and nitrogen deposition and related alterations in soil.     

Trichloroacetic acid in the environment

Suppositions that the trichloroacetic acid (TCA, CCl3C(O)OH) found in nature was a consequence solely of the use of chlorinated hydrocarbon solvents prompted this critical review of the literature on its environmental fluxes and occurrences. TCA is widely distributed in forest soils (where it was rarely used as an herbicide) and measurements suggest a soil flux of 160 000 tonnes yr(-1) in European forests alone. TCA is also produced during oxidative water treatment and the global flux could amount to 55 000 tonnes yr(-1) (from pulp and paper manufacture, potable water and cooling water treatments). By contrast, the yields of TCA from chlorinated hydrocarbon solvents are small: from tetrachloroethene 13 600 tonnes yr(-1) and from 1,1,1-trichloroethane 4300 tonnes yr(-1) on a global basis, at the atmospheric burdens and removal rates typical of the late 1990s. TCA is ubiquitous in rainwater and snow. Its concentrations are highly variable and the variations cannot be connected with location or date. However, there is no significant difference between the concentrations found in Chile and in eastern Canada (by the same analysts), or between Malawi and western Canada, or between Antarctica and Switzerland, nor any significant difference globally between the concentrations in cloud, rain and snow (although local enhancement in fog water has been shown). TCA is present in old ice and firn. At the deepest levels, the firn was deposited early in the 19th century, well before the possibility of contamination by industrial production of reactive chlorine, implying a non-industrial background. This proposition is supported by plume measurements from pulp mills in Finland. TCA is ubiquitous in soils; concentrations are very variable but there are some indications that soils under coniferous trees contain higher amounts. The concentrations of TCA found in plant tissue are region-specific and may also be plant-specific, to the extent that conifers seem to contain more than other species. TCA is removed from the environment naturally. There is abundant evidence that soil microorganisms dehalogenate TCA and it is lost from within spruce needles with a half-life of 10 days. There is also recent evidence of an abiotic aqueous decarboxylation mechanism with a half-life of 22 days. The supposedly widespread effects of TCA in conifer needles are not shown in controlled experiments. At concentrations in the needles of Scots pine similar to those observed in needles in forest trees, changes consequent on TCA treatment of field laboratory specimens were almost all insignificant.     

Relations between crown condition and ozone and its dependence on environmental factors

It is now widely accepted that stomatal ozone uptake provides a more reliable indicator for the assessment of risk of ozone damage to forest trees than ozone exposure. Thus, environmental factors influencing stomatal opening strongly affect the sensitivity of forest trees towards high ozone concentrations. In this study the hydrological model WAWAHAMO is used to simulate stomatal opening dependent on air temperature, solar radiation, vapor pressure deficit and soil water potential. Then, a statistical analysis was carried out to investigate relations between crown defoliation and ozone concentrations dependent on stomatal opening. The results support the hypothesis that tropospheric ozone contributes to the observed crown defoliation. However, environmental factors strongly affect tree response to high ozone concentrations.     

Fine root studies in situ and in the laboratory

The fine roots and myocorrhizae of beech, spruce and fir trees exposed to ozone, sulphur dioxide and simulated acid precipitation in open-top chambers (OTC) were examined both in situ by rhizoscopy and in the laboratory using root samples from soil cores. Prior to measurements the trees were treated for about one year. During the second year of treatment the fine root production of all three tree species was determined rhizoscopically. The OTC experiments were concluded after an additional three years at which time fine root and small root dry matter as well as the absolute and relative frequencies of mycorrhizae of spruce and fir were determined from soil cores. The vitality of spruce mycorrhizae was examined by fluorescein diacetate staining. In addition total contents of essential cations of spruce mycorrhizae were measured. Long-term exposure to SO(2), SO(2) + O(3), and simulated acid precipitation led to an increased mycorrhizal production by fir. On spruce, a decreased number of mycorrhizae was found in the chambers polluted with SO(2), but a high proportion of dead fine roots indicated an increased root production with an intensified turnover or a delayed decomposition of spruce mycorrhizae. The cation analyses showed an accumulation of Ca(2+) and Zn(2+) in the mycorrhizae of spruce exposed to ozone.     

Mercury loss from soils following conversion from forest to pasture in Rondônia, Western Amazon, Brazil

This work reports on the effect of land use change on Hg distribution in Amazon soils. It provides a comparison among Hg concentrations and distribution along soil profiles under different land use categories; primary tropical forest, slashed forest prior to burning, a 1-year silviculture plot planted after 4 years of forest removal and a 5-year-old pasture plot. Mercury concentrations were highest in deeper (60-80 cm) layers in all four plots. Forest soils showed the highest Hg concentrations, ranging from 128 ngg(-1) at the soil surface to 150 ngg(-1) at 60-80 cm of depth. Lower concentrations were found in pasture soils, ranging from 69 ngg(-1) at the topsoil to 135 ngg(-1) at 60-80 cm of depth. Slashed and silviculture soils showed intermediate concentrations. Differences among plots of different soil-use categories decreased with soil depth, being non-significant below 60 cm of depth. Mercury burdens were only statistically significantly different between pasture and forest soils at the topsoil, due to the large variability of concentrations. Consequently, estimated Hg losses were only significant between these two land use categories, and only for the surface layers. Estimated Hg loss due to forest conversion to pasture ranged from 8.5 mgm(-2) to 18.5 mgm(-2), for the first 20 cm of the soil profile. Mercury loss was comparable to loss rates estimated for other Amazon sites and seems to be directly related to Hg concentrations present in soils.     

Effects of photochemical smog and mineral nutrition on ponderosa pine seedlings

Two-year-old seedlings of ponderosa pine (Pinus ponderosa Dougl. ex Laws) were exposed to ambient concentrations of photochemical smog (AA) and clean air (CA) during a single field season at Tanbark Flat of the San Gabriel Mountains in the Los Angeles Basin. The seedlings were grown in a perlite-vermiculite medium with full supply of nutrients (based on modified Hoagland solution); reduced to 50% supply of N; reduced to 50% supply of Mg; and reduced to 50% supply of N+Mg. No significant effects of air pollution exposures on injury development, stem growth and concentrations of plant pigments were determined. The seedlings in the AA treatment had decreased N concentration in current year needles compared with CA seedlings; however, the needle concentrations of other elements did not change. Reduction of N supply in the growing medium caused decreased N, P, Ca, K and chlorophyll a concentrations in needles. Stem growth of the seedlings with reduced N supply was significantly decreased as well. No changes in stem growth or chemical composition of plants with reduced Mg supply were noted. Reduction of supply of nutrients did not change responses of trees to the air pollution exposures.     

Accumulating pollutants in conifer needles on an Atlantic island - a case study with Pinus canariensis on Tenerife, Canary Islands

Concentrations of potential pollutant elements Na, Cl, and S were investigated in needles of Pinus canariensis grown at 55 field plots in Tenerife. Microelement concentrations (including heavy metals) were measured at a subset of 18 plots. Na and Cl concentrations were high at low elevations (up to 8 mg g(-1) Cl and 5.5 mg g(-1) Na). Na/Cl ratio close to standard seawater indicated sea spray influence up to 1200 m a.s.l. Only at few plots, sulphur concentrations indicated possible pollutant impact. Cluster and correlation analyses identified a related group of V, As, Cr, Fe, Mo, Ni, Cu, Pb, and Al, possibly related to traffic exhaust aggregated with soil particles. Mainly north-eastern, lower elevated plots were exposed to those immissions, but metal concentrations were generally low compared to data from other studies. In conclusion, seawater and soil particles explained most of the element distribution pattern in pine needles in Tenerife, but strong indications for some effect of local sources of air pollutants were detected.     

Are N and S deposition altering the mineral composition of Norway spruce and Scots pine needles in Finland?

Data from a large-scale foliar survey were used to calculate the extent to which N and S deposition determined the mineral composition of Scots pine and Norway spruce needles in Finland. Foliar data were available from 367 needle samples collected on 36 plots sampled almost annually between 1987 and 2000. A literature study of controlled experiments revealed that acidifying deposition mediates increasing N and S concentrations, and decreasing Mg:N and Ca:Al ratios in the needles. When this fingerprint for N and S elevated deposition on tree foliage was observed simultaneously with increased N and S inputs, it was considered sufficient evidence for assuming that acidifying deposition had altered the mineral composition of tree needles on that plot in the given year. Evidence for deposition-induced changes in the mineral composition of tree foliage was calculated on the basis of a simple frequency model. In the late eighties the evidence was found on 43% of the Norway spruce and 27% of Scots pine plots. The proportion of changed needle mineral composition decreased to below 8% for both species in the late nineties.     

Trends in needle and soil chemistry of Norway spruce and Scots pine stands in South Sweden 1985-1994

The nutrient status of the trees and soil in 42 stands of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) in Scania, South Sweden was followed from 1985 to 1994. Samples from needles taken in winter 1985, 1987, 1990, and 1994, and soils in 1988 and 1993 were analyzed. Concentrations, as well as ratios to N, of K and Cu in needles of both species decreased by approximately 40% from 1985 to 1994. Soil analyses indicate ongoing soil acidification and leaching of mineral nutrients from the soil profile. Together with deposition data and corroboration from modeled scenarios, these data support the recent contention that one consequence of enhanced deposition of N and S will be the development of nutrient imbalances in trees growing in southern Sweden.     

Base cation depletion, eutrophication and acidification of species-rich grasslands in response to long-term simulated nitrogen deposition

Pollutant nitrogen deposition effects on soil and foliar element concentrations were investigated in acidic and limestone grasslands, located in one of the most nitrogen and acid rain polluted regions of the UK, using plots treated for 8-10years with 35-140kg Nha(-2)y(-1) as NH(4)NO(3). Historic data suggests both grasslands have acidified over the past 50years. Nitrogen deposition treatments caused the grassland soils to lose 23-35% of their total available bases (Ca, Mg, K, and Na) and they became acidified by 0.2-0.4 pH units. Aluminium, iron and manganese were mobilised and taken up by limestone grassland forbs and were translocated down the acid grassland soil. Mineral nitrogen availability increased in both grasslands and many species showed foliar N enrichment. This study provides the first definitive evidence that nitrogen deposition depletes base cations from grassland soils. The resulting acidification, metal mobilisation and eutrophication are implicated in driving floristic changes.