Showing papers in "Water Air and Soil Pollution in 1989"

Effects of heavy metals in soil on microbial processes and populations (a review)

Abstract: The effects of Cd, Cu, Zn, and Pb on soil microorganisms and microbially mediated soil processes are reviewed. The emphasis is placed on temperate forest soils. The sensitivity of different measurements is discussed, and data compiled to compare relative toxicity of different metals. On the whole the relative toxicity of the metals (on a μg g−1 soil basis) decreased in the order Cd > Cu > Zn > Pb, but differences between different investigations were found. The influence of abiotic factors on metal toxicity is briefly discussed and especially examplified by different soil organic matter content. Evidence of tolerance and adaptation in the soil environment and the time scale involved in the evolution of a metal-tolerant microbial community after metal exposure are also considered.

Copper toxicity and chemistry in the environment: a review

Abstract: Copper compounds have been widely used in industrial processes and agriculture. As a result, elevated Cu concentrations can be found in certain areas of the biosphere. To better understand the toxicity of Cu to organisms it is necessary to understand the mechanism by which Cu influences biological and chemical processes in the environment. This review will examine Cu toxicity, microbial resistance mechanisms and factors influencing Cu speciation and toxicity in the environment

Toxicity of heavy metals (Zn, Cu, Cd, Pb) to vascular plants

Abstract: The literature on heavy metal toxicity to vascular plants is reviewed. Special attention is given to forest plant species, especially trees, and effects at low metal concentrations, including growth, physiological, biochemical and cytological responses. Interactions between the metals in toxicity are considered and the role of mycorrhizal infection as well. Of the metals reviewed, Zn is the least toxic. Generally plant growth is affected at 1000 μg Zn L−1 or more in a nutrient solution, though 100 to 200 µg L−1 may give cytological disorders. At concentrations of 100 to 200 μg L−1, Cu and Cd disturb metabolic processes and growth, whereas the phytotoxicity of Pb generally is lower. Although a great variation between plant species, critical leaf tissue concentrations affecting growth in most species being 200 to 300 μg Zn g−1 dry weight, 15 to 20 μg Cu g−1 and 8–12 μg Cd g−1. With our present knowledge it is difficult to propose a limit for toxic concentrations of Zn, Cu, Cd and Pb in soils. Besides time of exposure, the degree of toxicity is influenced by biological availability of the metals and interactions with other metals in the soil, nutritional status, age and mycorrhizal infection of the plant.

Heavy-metal ecology of terrestrial plants, microorganisms and invertebrates

Abstract: Ecological and physiological effects of heavy metals on terrestrial organisms are reviewed, considering evidence from both laboratory and field studies. Problems concerning how to define heavy-metal exposure and to assess the sensitivity of field biota to heavy metals are discussed. Mechanisms of heavy-metal tolerance are considered including avoidance, exclusion, immobilization and excretion, as well biochemical mechanisms including enzymatic change. The taxonomy of heavy-metal tolerance and problems concerning tolerance and ecological performance are discussed briefly. Efforts are made to compare the relative sensitivity of various groups, including bacteria, fungi, bryophytes, lichens, vascular plants and soil invertebrates. An emphasis is placed on organisms of temperate forest ecosystems, particularly coniferous forests.

Fluxes of Cu, Zn, Pb, Cd, Cr, and Ni in temperate forest ecosystems

Abstract: The literature on the fluxes of six heavy metals in temperate forest ecosystems is reviewed. Special attention is given to wet and dry deposition and internal flux, to metal budgets for ecosystems and soils, to concentrations in aqueous compartments of the ecosystem and to speciation in soil solutions. Metal fluxes are discussed in relation to pollution load, soil type, tree species and land use. The mobility of Cu and Pb is strongly dependent on the solubility of organic matter. These metals are commonly accumulated in forest soils. Zinc, Cd and Ni are greatly influenced by soil acidity and are often lost in considerable amounts from acidified soils. Chromium is often at balance in forest ecosystems. Implications for metal solubility and budgets in forest soils are discussed in connection with an increase in soil acidification.

Effects of acidification and liming on carbon and nitrogen mineralization and soil organisms in mor humus

Abstract: The aim was to determine if changes in C and N mineralization after acidification and liming could be explained by changes in the soil organism biomass. Intact soil cores from F/H layers in a Norway spruce (C:N=31) and a Scots pine (C:N=44) stand in central Sweden were treated in the laboratory for 55 days with deionized water (control), weak H2SO4 (successively applied as 72 mm of acid rain of pH 3.1), strong H2SO4 (applied as a single high dose of pH 1), and lime CaCO3. Strong acidification reduced C mineralization and increased net N mineralization in both soils. Weak acidification resulted in similar but less pronounced effects. Liming initially stimulated C mineralization rate, but the rates declined, indicating that an easily available C source was successively used up by the microorganisms. Liming also increased net N mineralization in the C:N=31 humus, but not significantly in the C:N--44 humus. Strong acidification generally affected the amounts of FDA-active fungal hyphae, nematodes and enchytraeids more than the other treatments did. The increases in net N mineralization after acidification and liming could only partly be explained by the decreases in biomass N in soil organisms. Mineralization of biomass N from killed soil organisms could at the most explain up to about 30% of the increase in net N mineralization after strong acidification. Most of the effects on N mineralization seemed to depend on the fact that acidification reduced and liming increased the availability of C and N to the microorganisms. Furthermore, acidification seemed to reduce the incorporation of N from dead organisms into the soil organic matter and, thereby, make the N compounds more readily available to microbial decomposition and mineralization.

Simulation of the long-term soil response to acid deposition in various buffer ranges

Abstract: A soil acidification model has been developed to estimate long-term chemical changes in soil and soil water in response to changes in atmospheric deposition. Its major outputs include base saturation, pH and the molar Al/BC ratio, where BC stands for divalent base cations. Apart from net uptake and net immobilization of N, the processes accounted for are restricted to geochemical interactions, including weathering of carbonates, silicates and Al oxides and hydroxides, cation exchange and CO2 equilibriums. First, the model's behavior in the different buffer ranges between pH 7 and pH 3 is evaluated by analyzing the response of an initially calcareous soil of 50 cm depth to a constant high acid load (5000 molc ha−1 yr−1) over a period of 500 yr. In calcareous soils weathering is fast and the pH remains high (near 7) until the carbonates are exhausted. Results indicate a time lag of about 100 yr for each percent CaCO3 before the pH starts to drop. In non-calcareous soils the response in the range between pH 7 and 4 mainly depends on the initial amount of exchangeable base cations. A decrease in base saturation by H/BC exchange and Al/BC exchange following dissolution of Al3+ leads to a strong increase in the Al/BC ratio near pH 4. A further decrease in pH to values near 3.0 does occur when the A1 oxides and/or hydroxides are exhausted. The analyses show that this could occur in acid soils within several decades. The buffer mechanisms in the various pH ranges are discussed in relation to Ulrich's concept of buffer ranges. Secondly, the impact of various deposition scenarios on non-calcareous soils is analyzed for a time period of 100 yr. The results indicate that the time lag between reductions in deposition and a decrease in the Al/BC ratio is short. However, substantial reductions up to a final deposition level of 1000 molc ha−1 yr−1 are needed to get Al/BC ratios below a critical value of 1.0.

Critical loads for nitrogen deposition on forest ecosystems

Abstract: Critical loads for N deposition are derived from an ecosystem's anion and cation balance assuming that the processes determining ecosystem stability are soil acidification and nitrate leaching. Depending on the deposition of S, the parent soil material, and the site quality critical N deposition rates will range between 20 to 200 mmol m−2 yr−1 (3 to 14 kg ha−1 yr−1) on silicate soils and reach 20 to 390 mmol m−2 yr−1 (3 to 48 kg ha−1) on calcareous soils.

Effect of pH on chemical forms and plant availability of cadmium, zinc, and lead in polluted soils

Abstract: The effect of pH on chemical forms and plant availability of heavy metals in three polluted soils was investigated. The soils were adjusted to pH values of 7.0, 6.0, and 4.5, then sequentially extracted so that Cd, Zn, and Pb could be partitioned into five operationally defined chemical fractions: exchangeable, carbonate, Fe-Mn oxide, organic, and residual. Kidney beans were grown in the soils to investigate plant availability of the metals in relation to changes of their levels in chemical forms resulting from alteration of soil pH. Alteration of pH resulted in changes of chemical forms of the metals in the soils, and at lower pH the changes were more significant. When soil pH values were decreased from 7.0 to 4.55, levels of Cd, Zn, and Pb in exchangeable form increased, decreased in carbonates and decreased slightly in Fe-Mn oxide forms. Their levels in organic and residual forms were unchanged. Although concentration of metals in plants increased with reduction in soil pH values, dry matter yields were also restricted, so that the amount of metal uptake were almost similar. The uptake rate of the metals in the exchangeable + carbonate forms was the same for the three elements in all the cases.

Comparative evaluation of NTA and EDTA for extractive decontamination of Pb-polluted soils

Abstract: Nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA) were compared for their ability to solubilize Pb from a highly-contaminated (PbT 21%) soil collected from a battery recycling facility. For chelant concentrations below 0.04 M (representing a 1:1 chelant-to-PbT molar ratio), EDTA released 10 to 30% more Pb than NTA. NTA-to-Pb T ratios greater than 1:1 reduced Pb recovery because of readsorption of Pb(NTA)24− onto positively-charged oxide soil components at pH < 8.5. For the EDTA system, however, complexation completely bound all coordination sites of Pb and EDTA, leaving no functional groups available for surface adsorption. Thus, Pb recovery progressively increased with higher EDTA concentrations, although the additional Pb release with each EDTA increment became smaller. For pH < 5 and EDTA/Pb of 2:1, Pb recovery exceeded 90%. The addition of 0.5 M NaC1O4 enhanced Pb recovery by EDTA for pH 5 to 12, but substantially suppressed recovery by NTA for pH < 11. Because Pb release by NTA was diminished by high ionic strength and chelant-to-metal ratios, NTA may be limited as a soil washing reagent. Stronger complexation and consistent Pb desorption behavior by EDTA favors its use.

Cycling of mercury between water, air, and soil compartments of the environment

Abstract: The propensity to resist chemical, photo-chemical or biological degradation processes, coupled with a high degree of mobility — due to favorable physical-chemical properties such as relatively high vapor pressure and low solubility in water - bestows upon some chemical substances the necessary pre-requisites for extensive cycling among environmental compartments. Certain inorganic and organometallic species of Hg exhibit the aforementioned characteristics. This paper presents field measurement data, collected in Canada and Sweden, that provide information concerning the direction and magnitude of the material fluxes associated with transfer processes of Hg in the natural environment. The results of the field measurements reported here point to the importance of the natural phenomena of emission or re-emission (i.e., volatilization processes) involving the release of volatile Hg species from lake and soil surfaces into the overlying air, at least under warm weather conditions. Consequently, volatilization fluxes of Hg from natural surfaces should be taken into account when constructing biogeochemical cycles for this element and when calculating mass balances or budgets for Hg on local, regional and global scales.

The influence of pH, soil type and time on adsorbtion and uptake by plants of Cd added to the soil

Abstract: Adsorption of Cd by two soils and its uptake by perennial ryegrass (Lolium perenne) and winter rape (Brassica napus) as a function of pH (pH 4 to 7) and the amount of Cd added to the soil (0 to 5 mg kg−1 soil) were studied in a 2-yr pot experiment. In the soils, the more soluble fractions of Cd increased as the pH was lowered. Increasing the pH from 5 to 7 by adding CaO invariably reduced the Cd-content of ryegrass plants, but this decrease was less consistent where the pH had only been increased to 6. In some cases, acidifying the soil with S to reach a pH of 4 also led to a decrease in plant Cd-content. The Cd-content of rapeseed plants was markedly higher at pH 4 than at pH 5. Plant damage at low pH was observed in this crop. Water-leachable and CaCl2-extractable soil Cd levels as well as plant uptake were higher in the sand soil than in the clay soil, whereas 1M NH4AcO (buffered at pH 4.8 and 7) extracted roughly equal amounts from both soils. Adding more Cd to the soil did not change the relation between Cd levels in soil and those in plants; instead the amounts of Cd in both increased in direct proportion to the amounts added. Fixation of added Cd apparently did not occur continuously at any pH or Cd-level during the 2-yr period, but seasonal variations in solubility and uptake were observed.

The role of organic acids in the acidification of surface waters in the Eastern U.S.

Abstract: There is considerable uncertainty concerning the role of naturally occurring organic solutes in the acidification of surface waters. To provide a preliminary assessment of this process, we evaluated water chemistry data obtained from the US EPA Eastern Lake Survey (ELS). A wide range of dissolved organic carbon (DOC) and organic anion concentrations were evident across acid-sensitive lake districts in the Eastern US. In particular, lakes in Maine, the Upper Midwest and Florida contained high concentrations (greater than 1000 gmol C · L−1) of DOC. High concentrations of organic anions, estimated by discrepancy in charge balance in several subregions, suggest that dissociation of naturally occurring organic acids could significantly reduce the ANC of dilute surface waters. Unfortunately, analysis of acidification by organic solutes is complicated by uncertainty in H+ dissociation characteristics. Input of organic acids with weakly acidic pK a values do not alter acid neutralizing capacity (ANC), while strongly acidic organic functional groups dissociate completely and decrease ANC. As a first step to assess the acid/base characteristics of naturally occurring organic solutes, we calibrated the Oliver et al. (1983) model, using a reduced version of the ELS data set. This model explained 94% of the observed variability in organic anion concentration in this data set. However, model parameters obtained from the ELS calibration were somewhat different than values provided by Oliver et al. (1983), based on potentiometric titrations of pre-concentrated organic acids. The discrepancy in model parameters has implications for estimating organic anion concentrations in water using the Oliver et al. (1983) model. Finally, data from the ELS indicates that across glaciated regions of the eastern US, concentrations of DOC and organic ions were negatively correlated with SO inf2− p4 . This trend would appear to be consistent with the hypothesis that inputs of strong acids immobilize organic acids, resulting in a shift of surface water acidification by organic acids to strong acids.

Cadmium soil sorption at low concentrations: VIII. correlation with soil parameters

Abstract: Cadmium distribution coefficients, K d were determined at low Cd concentrations (solute: 02 to 30 μg Cd dm−3, soil: 0044 to 11 mg Cd kg−1) for 63 Danish agricultural soils The K d values ranged from 15 to 2450 L kg−1 About 40% of the soils had K d values below 200 L kg−1 The observed K d values correlated very well with soil pH (r 2 = 072) Introducing soil organic matter content as a second parameter improved the correlation some (r 2 = 079) No further improvements were obtained by introducing traditional soil parameters as clay, silt, fine sand, coarse sand and CEC or ‘reactive’ parameters as oxyhydroxides of Mn, Fe and Al The identified regression equation for predicting K d values indicates that K d approximately doubles for each 05 unit increase in pH or 2% increase (weight basis) in organic matter content

Uptake, retention and toxicity of heavy metals in L ichens

Abstract: Literature on metals, particularly heavy metals, in lichens is reviewed including mechanisms of metal uptake, retention, toxicity and tolerance. Interspecies differences in sensitivity are discussed as well as the development and nature of extreme tolerance encountered in certain taxa.

Critical metal concentrations for forest soil invertebrates

Abstract: Based on a review of the literature on metal effects on forest soil invertebrates 100 to 200 mg Pb, < 100 mg Cu, < 500 mg Zn and 10 to 50 mg Cd kg−1 soil or litter are suggested as maximum allowable metal concentrations that will cause no adverse effects. These critical levels, emphasizing effects on abundance, diversity and life history parameters, are considered conservative and tentative, since few of the surveys they rely on were designed for critical level assessment; especially with respect to long-term consequences on decomposition and nutrient regeneration. The variation between animal species and individuals in susceptibility to metals due to differences in uptake, storage and tolerance are addressed.

Aluminum toxicity in forests exposed to acidic deposition: The ALBIOS results

Abstract: The ALBIOS project was conducted to examine the influence of acidic deposition on aluminum transport and toxicity in forested ecosystems of eastern North America and northern Europe. Patterns of aluminum chemistry were evaluated in 14 representative watersheds exposed to different levels of sulfur deposition. Controlled studies with solution and soil culture methods were used to test interspecific differences in aluminum sensitivity for one indicator species (honeylocust - Gleditsia triacanthos L. ) and six commercial tree species (red spruce - Picea rubens Sarg., red oak - Quercus rubra L., sugar maple - Acer saccharum Marsh., American beech - Fagus grandifolia Ehrh., European beech - Fagus sylvatica, and loblolly pine - Pinus Taeda L. ). Overall, red spruce was the tree species whose growth was most sensitive to soluble aluminum, with significant biomass reductions occurring at Al concentrations of approximately 200–250 umol/L. Analyses of soil solutions from the field sites indicated that the conditions for aluminum toxicity for some species exist at some of the study areas. At these watersheds, aluminum toxicity could act as a contributing stress factor affecting forest growth.

Heavy metal pollution by long range atmospheric transport in natural soils of Southern Norway

Abstract: Natural surface soils in Southern Norway are strongly contaminated by metals from atmospheric deposition. Except from local pollution with Cu, Ni and to a limited extent Pb around the town of Kristiansand, this large-scale contamination can be ascribed to long-range atmospheric transport from other parts of Europe. Zinc, As, Cu, and Pb are all found in excessive concentrations in the surface layer of natural soils throughout the region, and in particular within a zone of about 20 to 40 km from the coast. In this zone the elements appear at the following concentrations or higher in the A0 layer (typical levels in other parts of Norway little affected by air pollution in parantheses): Zn, 120(30) mg kg−1; As, 4(0.5) mg kg−1; Cd, 2(0.2) mg kg−1; Pb, 160(15) mg kg−1. Possible harmful effects to soil biological processes of this contamination cannot be excluded.

Zooplankton communities and acidification processes (a review)

Abstract: A review of the literature which deals the with zooplankton of acid-stressed ecosystems revealed several strong patterns, weaker patterns, areas of controversy or inconsistency, and poorly understood but potentially important factors. Those patterns which are strong, but not necessarily universal, include a general response to short term pH shocks suggesting that daphnids are least tolerant followed by other cladocerans, copepods, and chaoborids. In addition, the numbers of both crustacean and rotifer species are decreased, and the importance of daphnids is reduced in acidic lakes, while limnetic hemipterans are greatly increased in acidic fishless lakes. Weaker patterns include reduced zooplankton biomass, reduced importance of cyclopoids, and increased representation of generalist species in acidic lakes, and intraspecies differences in pH tolerance indicating that populations of acid-stressed ecosystems are more tolerant. But, zooplankton biomass is apparently a result of system productivity as opposed to pH per se. Inconsistencies within the literature exist as to whether chaoborids are more abundant in acidic fishless lakes, the influence of physiological stress contra predation in determining community structure, the immediate response of the zooplankton to lake neutralization, and the toxicity of Al. The importance of metals, humic substances, and the fauna in determining community dynamics is poorly understood. Although both phyto- and zooplankton communities can be severely simplified in acidic lakes, the influence of the phytoplankton on the zooplankton, beyond the relation edible biomass vs zooplankton standing stock, in these ecosystems is unclear. From the literature it is apparent that direct physiological influences of acid-stress are important, but that indirect (biotic) influences and variables which correlate with pH are often as important if not more so to the zooplankton.

Measurements of wet and dry deposition in a Northern Hardwood forest

Abstract: Inputs of wet and dry deposition were monitored at the Huntington Forest in the Adirondack Mountains of New York for two years in the open and beneath the canopy of a northern hardwood forest. In the open, ion flux estimates were similar using wet-only weekly (NADP protocol) and event collections, but bulk collections were higher for all ions except H+, which was much lower. These differences were due to the contribution of dry deposition and possible biotic alterations in bulk collectors. Dry deposition was estimated using air concentrations and ion-specific depositional velocities modeled with meteorological data, and contributed substantially to the input of all ions [H+ (45%), Na+ (24%), K+ (22%), NH4 + (12%), Ca2+ (58%), Mg2+(43%), NO3 − (55%), Cl− (27%) and SO4 −2 (26%)]. Dry input of base cations was dominated by coarse particles, whereas gaseous inputs were more important for S and NO3 −. Atmospheric concentrations of SO2 and inputs of SO4 2− and H+ were lower at this site than sites closer to point sources of S gas emission. The importance of estimating atmospheric inputs was examined using examples of elemental budgets. For example, different estimates of the contribution of dry deposition of SO4 2− (9–21 meq m−2 y−1) resulted in conclusions ranging from no net retention to a net loss of this element. Such differences have important implications in assessing the current and future role of atmospheric inputs in affecting elemental cycling.

Distribution of mercury species in soil from a mercury-contaminated site

Abstract: The distribution of mercury species was determined in soil from a site with Hg contamination. Mercury contamination was primarily confined to the top 40 cm of soil, and the concentration of total Hg ranged from 0.5 to 3000 µg Hg g−1. Of total Hg present, we determined that 91% was inorganic, 0.01% organic (as methyl Hg), and 6% elemental Hg. Furthermore, of total inorganic Hg present, 85% was in the insoluble mercuric sulfide form. Thus, of total Hg present in soil at this contaminated site, 91% was in the relatively insoluble HgS and Hg0 forms.

Liming and fertilization as mitigation tools in declining forest ecosystems

Abstract: In central Europe the ‘new type’ forest damages have been observed since the mid 1970's Various investigations indicate that the declines are frequently associated with nutritional disturbances Good correlations between the site specific substrate chemistry and the actual nutritional status of the trees/stands were found To explain the sudden and widespread appearance of the forest declines, adverse anthropogenic impacts mainly due to elevated emissions of air pollutants and their atmospheric derivatives are hypothesized in combination with natural stress factors Causal mechanisms include soil degradation due to accelerated soil acidification and increased nutrient leaching from the canopy of forest stands Fertilization and liming experiments have demonstrated that a fast and sustained revitalization and restabilization of declining forest ecosystems marked by nutritional disturbances can be achieved This is demonstrated by chemical and histological foliar analyses generally combined with a visible improvement of the phenotype Soil analyses reveal a considerable positive change of the chemical soil status due to the site and species specific application of appropriate amounts of fast soluble fertilizers and lime Considering these recent favorable findings, as well as based on observations from historic fertilization and liming trials nutrient supplementation and liming have become common tools to counteract the new type forest damages in West Germany

Climate change and forest decline: A review of the red spruce case

Abstract: Climate change as a contributor to the decline of red spruce is investigated. Previous climatic response model results are reviewed and more detailed time-dependent modeling of tree growth-climate interactions are performed using the Kalman filter. These new results show that there is a clear temporal and elevational dependence in the response of red spruce to climate. Influence of abnormally warm prior-August temperatures become increasingly time-dependent with decreasing elevation, which is contrary to the elevational gradient in the severity of decline. Thus, this variable, which had been implicated in red spruce declines from previous studies, is unlikely to be a primary cause of the current decline. However, it may be implicated in earlier declines at low elevations. Prior-December temperatures are influential at all elevations, but time-dependent only at the highest elevational zone. The emergence of a strongly time-dependent prior-November temperature response is clearly associated with a time-trend in the temperature record. Thus, it is likely that red spruce is responding, in a transient sense, to changing climate. An additional transient response to current-July temperatures is not associated with any unusual behavior in the data and is, as yet, unexplained. These results show that red spruce is not in equilibrium with its climatic environment, which may have made it more susceptible to damage caused by natural and anthropogenic factors.

Metal fluxes to Swedis forest lakes

Abstract: Data on atmospheric deposition, transport via run-off water and contents in soil were used to estimate the fluxes of Zn, Cd, Cu, Pb, and Hg to Swedish forest lakes. The calculations refer to a hypothetical lake with a surface area of about 9% of the total catchment area. There are clear differences in the pathways and transport mechanisms for the different elements. The dominating pathway for the input of Zn and Cd to lakes is via run-off from the drainage area. About 60 to 95% of the total load comes from run-off, highest in the acidified areas. The acidification status of the soil is by far the most important factor regulating the mobility of these elements. The amounts of Hg and Pb deposited on the drainage area are mainly accumulating in the surficial soil layers. The transport of these elements is primarily associated with humic substances. About 30 to 50% of the total load of Pb and 25 to 75% of the total load of Hg to lakes originates from run-off. The transport mechanisms for Cu are similar to those of Pb and Hg, but due to the lower anthropogenic airborne load, the direct deposition is of less importance.

Ion leaching from a sugar maple forest in response to acidic deposition and nitrification

Abstract: Year-to-year variation in acidic deposition within a mature sugar maple-dominated forest and in leaching of ions from the associated podzolic soil were examined at the Turkey Lakes Watershed between 1981 and 1986. Below-canopy inputs to the soil of SO42− and NO3− in throughfall averaged 640 and 295 eq. ha−1 yr−1; the corresponding ranges were 493–917 and 261–443 eq. ha−1 yr−1. The contribution of atmospheric deposition to SO42− NO3− and Ca2+ leaching decreased over the six years. During the study period, the mean annual volume-weighted NO3− concentration decreased in throughfall and forest-floor percolate and increased in the mineral-soil solution collected below the effective rooting zone. A substantial shift in the balance between SO42− and NO3−leaching from the mineral soil was observed; leaching of SO42−decreased and NO3− leaching increased with time. Leaching of Ca2+ and Mg2+ from the soil was increased as a result of excess NO3− production in the soil. The calculated output of NO3− from the soil, which averaged 1505 eq. ha−1 yr−1, considerably exceeded the atmospheric deposition of NO3−, whereas SO42− outputs were only moderately greater than inputs.

Natural stresses, nutrient imbalances and forest decline in southeastern Quebec

Abstract: Recent information is presented on biotic and abiotic stresses that have affected the deciduous forest in southeastern Quebec over the last 10 years as well as on the nature and the extent of nutrient imbalances observed over the last five years. A large part of the forest dieback is thought to have resulted from insect defoliation and adverse climatic conditions, particularly drought, which took place in the early 1980's. However these factors alone do not seem to account for all symptoms of the current forest decline. Repeated samplings and analyses of sugar maple (Acer saccharum Marsh.) foliage in the Quebec Appalachians since 1983 has revealed the occurrence of severe nutrient imbalances, particularly very low K and P concentrations on several sites. More recently, Mg deficiency was found to be associated with declining sugar maple stands in the Lower Laurentians. Appropriate fertilizer applications have restored adequate nutrition of sugar maple during the first three or four years of observation. Disturbed nutrition is discussed in the context of forest nutrient cycling.

Nutritional disturbances and histological changes in declining forests

Abstract: “New type” forest damages have been observed in West Germany since the mid-1970's and discussed in North America since the early 1980's. Various types of damage are associated with typical foliar discoloration symptoms related to site characteristic nutritional disturbances. The macronutrients are generally Mg, Ca, and K. Based on foliar and soil analysis results diagnostic fertilization trials were established at a wide variety of sites and stands in West Germany as well as in North America. The appropriate application of fast soluble fertilizers proved that damage symptoms associated with nutritional disturbances can frequently be mitigated within a relatively short period. The observed visual revitalization corresponds well with foliar analysis data obtained continuously for the last 5 yr. Soil analyses also reflect the improved nutrient supply. Investigations of older fertilizer trials indicated that stands fertilized before the appearance of “new type” damage symptoms are considerably more vital when compared to the untreated control plots. Remarkable results were derived from histological research. Microscopic analysis of needles proved the regeneration potential on a histological level for moderately yellowed needles after fertilization. Furthermore, needles of nutrient deficient trees reveal typical differences of tissue damages when compared to SO2 fumigated or O3 impacted needles. Thus, histological investigations can be used as a diagnostic tool to differentiate between direct and indirect forest damages.

Effects of acid, aluminium and lime additions on fish and invertebrates in a chronically acidic welsh stream

Abstract: A chronically acidic stream, mean pH 5.2, in upland mid-Wales was subjected to an induced episode of acidity, during which acid, Al and limestone were added at different points along the stream length. An upstream reference zone (A), an acid zone (B), an acid plus Al zone (C) and a downstream zone of Al at low pH with added limestone to increase pH (D) were created for a 24 hr period. Four species of fish and 10 species of invertebrates were exposed in each zone and response criteria measured included mortality, metal uptake, feeding and the ability of stressed animals to recover. Fish mortalities were greater in zones B and C than in zone A and were greatly reduced by the addition of lime in zone D. Overall mortality was low amongst the invertebrate species found in acid waters. Greatest mortalities were recorded for Gammarus pulex. G. pulex infected with the acanthocephalan parasite Pomphorhynchus laevis exhibited greater mortality than uninfected animals. The feeding rate of G. pulex was suppressed in all zones during the dosing period; uninfected G. pulex consumed more than infected animals, and the feeding rate of all gammarids increased post-dosing but not to the level of unexposed animals. Aluminium concentrations in fish gills increased with time. Invertebrate body burdens of Al were greatest in zone D, with significant increases over the dosing period for both G. pulex and Isoperla grammatica. No significant patterns were observed in the concentration of Ca, Na or K for either fish or invertebrates.

Analytical air pollution advection and diffusion models

Abstract: A review of non-Gaussian analytical solutions of the advection diffusion equation is presented. Their utilization to mathematical models of air pollution diffusion is discussed and the application of a particular solution is suggested. The suggested KAPPAG model uses the Demuth's (1978) solution and can incorporate smoothed observed vertical wind and diffusion coefficient profiles. It is shown that Demuth's solution can represent the realistic situations of the diminishing vertical exchange coefficient at the top of boundary layer.

Finnish lake survey: the role of organic and anthropogenic acidity

Abstract: A lake survey consisting of 987 randomly selected lakes was conducted in Finland in autumn 1987. The survey covered the whole country, and the water quality of the lakes can be considered as representative of the approximately 56 000 lakes larger than 0.01 km2 in Finland. The median TOC concentration is 12 mg L-1 and the median pH 6.3. The proportion of lakes with TOC concentrations > 5 mg L-1 in the whole country is 91 %. Organic anion is the main anion in the full data set (median 89 μeq L-1). The high organic matter concentrations in Finnish lakes are associated with catchment areas containing large proportions of peatlands and acid organic soils under coniferous forest. The survey demonstrated that organic matter strongly affects the acidity of lakes in Finland. The decreasing effect of organic matter on the pH values was demonstrated by both regression analysis and ion balances. At current deposition levels of *SO4 the pH of humic lakes in Finland is determined to a greater extent by high TOC concentrations than by *SO4 in most areas. In lakes with pH values lower than 5.5 the average organic anion contribution is 56 % and non-marine sulfate contribution 39 %. However, in the southern parts of the country, where the acidic deposition is highest, the minerogenic acidity commonly exceeds the catchment derived organic acidity.