Applied Geochemistry (v.22, #6)
Selected Papers from the 7th International Conference on Acid Deposition, Prague, Czech Republic, 12–17 June, 2005 by Martin Novák; Peter Brimblecombe; Daniel Houle; Alain Veron (1093-1094).
Sulphur behaviour in forest soils near the largest SO2 emitter in northern Europe by Galina Koptsik; Christine Alewell (1095-1104).
The impact of 60 a of SO2 emissions from a Ni–Cu plant in the Kola Peninsula (Russia) on soil S contents was assessed in podzols under pine forests. Sulphate desorption and the possible delay of acidification reversal was investigated, because the plant will be reconstructed in 2006 with an expected emission reduction of 90%. Sites were sampled along a pollution gradient in the prevailing wind direction from 1 to 66 km. The investigated podzols stored S mostly in the organic form. The concentrations of total and organic S in soil organic horizons tended to be higher near the smelter but were only weakly correlated with S deposition. No relationship between distance to smelter and S contents was found for the mineral horizons. Sulphate content and desorption behavior were highly variable due to natural variations of texture and extractable Al and Fe contents of the soils. The lack of a clear strong trend with distance from the smelter except in the organic layer indicated that long range transport and diffuse input of SO4 played a major role rather than point source impact. It was concluded that biological turnover is most likely the regulating process in these soils and thus low to medium release of SO4 is expected under decreasing deposition scenarios because organic S was the dominant fraction of total S in all soils.
The contribution of rain-on-snow events to annual NO3-N export from a forested catchment in south-central Ontario, Canada by M. Catherine Eimers; James M. Buttle; Shaun A. Watmough (1105-1110).
The contribution of rain-on-snow (ROS) events to NO3-N levels in stream water has received relatively little research attention. However, individual ROS events during January and February contributed up to 40% of annual NO3-N export from a forested catchment in south-central Ontario between 1980 and 2000, but comprised less than 10% of annual precipitation. Nitrate-N concentrations in stream water increased rapidly following ROS events, and were similar to the concentrations in incident rainfall and the accumulated snow pack, likely due to limited contact of runoff with mineral soil under snow cover and low winter biological activity. Increased NO3-N associated with ROS events resulted in substantial depressions in stream pH and alkalinity, which may delay the biological recovery from acidification. The contribution of ROS events to annual or winter NO3-N export has been generally greater in recent years, although there is a considerable year-to-year variation. As a result, ROS events contribute to inter-annual variability in stream NO3-N concentrations and will have a strong effect on apparent temporal trends. The contribution of ROS events to annual NO3-N export should be considered when assessing surface water recovery from acidification and the N-status of forests, particularly if climate change projections for winter warming result in a greater proportion of winter precipitation occurring as rain.
Potassium and phosphorus additions modify the response of Sphagnum capillifolium growing on a Scottish ombrotrophic bog to enhanced nitrogen deposition by J.A. Carfrae; L.J. Sheppard; J.A. Raven; I.D. Leith; A. Crossley (1111-1121).
This study reports the impacts of wet reduced versus oxidised N on in situ responses of Sphagnum capillifolium: architecture, chemistry and F v/F m. Nitrogen inputs were enhanced under realistic treatment scenarios in a unique experiment on an ombrotrophic bog ecosystem in the Scottish Borders, UK, receiving, historically and currently, low pollutant deposition. Ammonium (NH4Cl) and nitrate (NaNO3) treatments were applied from 2002 (June) at 16 kg and 64 kg N ha−1 a−1 with or without K and P (K2HPO4), provided in a 1:14 ratio of P:N. These wet treatments were applied to three replicates in precipitation collected at the site, as ‘real time’ applications to large, 13 m2 plots. A high application frequency >100 events was achieved and the maximum spray concentration was 4 mM. Over the study period June 2003–May 2004 rainfall was low over several months enabling the effects of water stress to be looked at. Branching and the length of photosynthetically active material were reduced by the high N input and the effect was more pronounced when the water-table was low, but the form of N was not important. Where the N form was important the effects of oxidised N were less favourable than those of reduced N. The findings are discussed in relation to current knowledge along with implications for critical N loads and management options for bogs to counteract the detrimental impact of elevated N deposition. These results provide further evidence that additions of K and P to N-polluted bogs can ameliorate the direct, negative impacts of N deposition on Sphagnum at least in the short-term.
Climate as a confounding factor in the response of surface water to nitrogen deposition in an area south of the Alps by Michela Rogora; Rosario Mosello (1122-1128).
Climate effects on NO3 concentrations have been investigated for two small rivers south of the Alps draining forested catchments. The Pellino and Cannobino rivers are representative of different stages of N saturation determined by high deposition of inorganic N (2.0–2.5 g N m−2 a−1). Long-term records of air temperature, precipitation, N deposition and stream NO3 concentration were used to assess the relative effect of N deposition and climate on NO3 export from the catchments. The climate signal was more evident in the river with the lower NO3 concentration. Prolonged dry and warm periods were the precondition for the occurrence of the highest peaks of NO3 concentration.
Monitoring of atmospheric deposition in European forests and an overview on its implication on forest condition by Richard Fischer; Volker Mues; Erwin Ulrich; Georg Becher; Martin Lorenz (1129-1139).
Forest conditions in Europe have been monitored over 20 years jointly by the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) and the European Union (EU). Maps for mean bulk SO4, NO3 and NH4 deposition at around 400 intensive monitoring plots in the years 1999–2001, as well as time trends for the period 1996–2001, are presented. Mean bulk SO4 deposition at 169 plots mostly located in central Europe decreased from 7.4 to 5.8 kgS ha−1 a−1. Mean NH4 bulk deposition decreased from 6.2 to 5.3 kgN ha−1 a−1. Nitrate bulk deposition fluctuated around 5 kgN ha−1 a−1. On average, throughfall deposition was considerably higher than bulk deposition. Time trends for mean tree crown defoliation as an overall indicator for forest condition show a peak in the mid 1990s for most of the monitored main tree species and a recent increase for the years 2003 and 2004. Multivariate linear regression analyses show some significant relations between deposition and defoliation. These relations depend on the tree species and site characteristics. Effects of deposition are moderated by the influence of biotic stress factors such as insects and fungi and by abiotic stress factors, such as weather.
Water chemistry in forested acid sensitive sites in sub-tropical Asia receiving acid rain and alkaline dust by Rolf D. Vogt; Jingheng Guo; Jiahai Luo; Xiaoyu Peng; Renjun Xiang; Jinsong Xiao; Xiaoshan Zhang; Dawei Zhao; Yu Zhao (1140-1148).
Acid rain, due to wet and dry deposition of S and N compounds, is an increasing environmental problem in China. A considerable deposition of alkaline dust serves to mitigate the acidifying effect to varying extent. Data from 3 years, a monitoring of water chemistry in 10 water compartments (i.e., two qualities of deposition, two types of throughfall, solution in five genetic soil horizons, and runoff) at five well documented sub-tropical forested catchments, have been interpreted in order to identify key processes governing the water chemistry in catchments suffering acid rain. This study of water chemistry in regions with sub-tropical climate supplements similar monitoring studies conducted in temperate regions with different types of soils and compositions of deposition. Natural organic acids as well as nutrient cycling of K+ have strong influence on the water chemistry in throughfall and upper soil horizons at the relatively pristine sites. At sites receiving elevated S and N deposition an accelerated cycling of K+ removes much of the mineral acidity in throughfall. The soil uptake of this K+ results in release of H+. Nitrification and/or assimilation of a substantial deposition of reduced N contributes at some sites also significantly to the acidity in the soils. During the study period, Ca2+ in solution was exchanged for Al3+ in the soils with an effective base saturation less than 20%. In deeper soil horizons most of this mobilized Al is re-adsorbed along with SO 4 2 - .
Fluxes of solute in two catchments with contrasting deposition loads in Atlantic Forest (Serra do Mar/SP-Brazil) by M. Cristina Forti; Christine Bourotte; Valdir de Cicco; Francisco C.S. Arcova; Maurício Ranzini (1149-1156).
Fluxes of solutes for two small catchments with contrasting deposition loads (polluted and natural) in the Atlantic Forest (Serra do Mar/SP-Brazil) were computed for rainfall, throughfall, soil water and stream flow (December 1999 until May 2002). One catchment (URBAN) is inside the largest metropolis of South America (São Paulo city) and the other (REFERENCE) is located inside the Serra do Mar State Park. The determined species in solution were: Na+, K+, Mg2+, Ca2+, NH 4 + , Cl−, NO 3 - and SO 4 2 - . The rainfall fluxes indicate that in the URBAN catchment NO 3 - deposition is mainly responsible for the rainfall acidity while in the REFERENCE there is no sign of acidic deposition. The net fluxes in throughfall are derived from dry deposition and rainwater interaction with the canopy and indicate a significant difference in the nutritional status of the vegetation. In the REFERENCE catchment the natural cycles are in equilibrium. This is indicated by the Cl− input–output relationship and, therefore, this area can actually be used as a reference for small catchment comparative studies. The exports of base cations from the URBAN catchment are high mainly due to the presence of high amounts of strong acid anions in the input. The nutrient input–output relationship for the URBAN forest presents a strong indication that atmospheric pollution is acidifying the drainage waters and damaging the vegetation. This acidification will lead to vegetation decline that, after a certain time, will make the forest susceptible to illnesses, droughts and insect attacks.
Effects of groundwater extraction from crystalline hard rock on water chemistry in an acid forested catchment at Gårdsjön, Sweden by Fredrik Mossmark; Hans Hultberg; Lars O. Ericsson (1157-1166).
Atmospheric deposition of S in Sweden has decreased by some 80% over the last 15 a, resulting in a general reduction of SO4 concentrations in ground and surface water. This project, however, shows that artificial hydrological alteration in an acid wetland can reverse this trend and increase acidity and SO4 concentrations. The experiment involved the monitoring of two catchments in relatively virgin conditions. In one of the catchments, an experiment with intensive groundwater extraction from the bedrock was carried out. During the experiment, the runoff from the catchment decreased by 50%. Furthermore, the extraction of groundwater resulted in increased seasonal aeration of the centrally located wetland, leading to oxidation of reduced S bound to the soil layers of the wetland. The S changed to solute SO4, with a subsequent SO4 surge. Thus, the experiment resulted in an induced acidification of the wetland and runoff waters. The extraction of groundwater significantly increased the recharge of water from the overburden, glacial till and organic soils to groundwater in the bedrock, which in turn reduced the retention time in the bedrock aquifer. These changes resulted in the chemical signature of the groundwater in the bedrock becoming similar to those of the wetland. The findings revealed deterioration in the water quality in the bedrock due to increased concentrations of dissolved organic C and SO4, as well as a decrease in pH.
Simulation of soil and surface water acidification: Divergence between one-box and two-box models? by J. Aherne; R.C. Helliwell; A. Lilly; R.C. Ferrier; A. Jenkins (1167-1173).
One soil-layer and two soil-layer model structures within the model of acidification of groundwater in catchments (MAGIC) were calibrated to 3 sites from the United Kingdom (UK) Acid Waters Monitoring Network. Catchment soil properties were segregated into two layers based on their hydrologic characteristics as defined by the hydrology of soil types (HOST) classification. Both model structures produced similar results for surface waters and soils. In general, simulated historic pH and acid neutralising capacity were slightly lower for the two-box structure. Similarly, weighted base saturation for both structures were comparable. Although both structures are highly consistent, the two-box simulations reflect the vertical differentiation in acid sensitivity, with the upper layers showing greater response to changes in acid deposition. The HOST classification appears to be a robust methodology to segregate soils and estimate flow-routing, providing a consistent methodology for application of the two-box protocol across the UK. The approach provides improved resolution for soils by representing their natural horizonation (acid-sensitive upper layers and higher-weathering lower layers), and a more appropriate tool for the integrated assessment of land use and climate impacts on catchments.
Large scale patterns of chemical recovery in lakes in Norway and Sweden: Importance of seasalt episodes and changes in dissolved organic carbon by Brit Lisa Skjelkvåle; Hans Borg; Atle Hindar; Anders Wilander (1174-1180).
Trends from 160 lakes in Norway and Sweden for the period 1990–2004 reveal that Scandinavian lakes show clear signs of recovery from acidification. Sulphate has decreased and ANC, alkalinity and pH have increased. During the last 5 a, the decline in SO 4 - has ceased, whereas ANC continues to increase. The results also show decreasing trends for Cl, while Na shows no or very small trends. The increase in the Na/Cl-ratio explains part of the increase in ANC. On average for the period 1990–2004 the decrease in Cl contributes 20–50% of the increase in ANC. The main cause of the trends in Cl in southern Sweden and Norway are probably due to declining seasalt inputs due to a higher frequency of heavy storms in the late 1980s and early 1990s. TOC exhibits increasing trends in regions with median TOC concentrations > 3 mg C/L, however, this does not contribute significantly to the observed increase in ANC.
Changes in the chemistry of lakes in the Adirondack region of New York following declines in acidic deposition by Charles T. Driscoll; Kimberley M. Driscoll; Karen M. Roy; James Dukett (1181-1188).
Long-term changes in the chemistry of wet deposition and lake water were investigated in the Adirondack region of New York. Marked decreases in concentrations of SO 4 2 - and H+ have occurred in wet deposition since the late 1970s. These decreases are consistent with long-term declines in emissions of SO2 in the eastern US. Changes in wet NO 3 - deposition and NO x emissions have been minor over the same interval. Virtually all Adirondack lakes have exhibited large decreases in concentrations of SO 4 2 - , which coincide with decreases in atmospheric S deposition. Since 1992, concentrations of NO 3 - have also decreased in many (27 of 48) Adirondack lakes. As atmospheric N deposition has not changed appreciably over this period (1992–2004), the mechanism contributing to this apparent increase in lake/watershed N retention is not evident. Decreases in concentrations of SO 4 2 - + NO 3 - have resulted in increases in acid neutralizing capacity (ANC; 37 of 48 lakes) and pH (31 of 48 lakes), and decreases in concentrations of inorganic monomeric Al, particularly in acid-sensitive lakes. Concentrations of dissolved organic C (DOC) have also increased in some (15 of 48) lakes coinciding with decreases in acidic deposition. Examination of changes in lake chemistry by hydrologic classes showed that drainage lakes in watersheds with thin deposits of glacial till and mounded seepage lakes have generally been the most responsive to decreases in acidic deposition.
Past and future changes to acidified eastern Canadian lakes: A geochemical modeling approach by T.A. Clair; J. Aherne; I.F. Dennis; M. Gilliss; S. Couture; D. McNicol; R. Weeber; P.J. Dillon; W. Keller; D.S. Jeffries; S. Page; K. Timoffee; B.J. Cosby (1189-1195).
As SO2 emissions are being reduced in North America, it has become important to know how rapidly the surface water chemistry of aquatic systems will recover. The authors applied the model of acidification of groundwater in catchments (MAGIC) to 410 acid-sensitive lakes located in a 3000 km east–west gradient in eastern Canada. The goal was to estimate the water chemistry from pre-acidification times, under worst case conditions (mid 1970s) and what it should be in the year 2030 after proposed acid emission reduction levels agreed-to or planned by Canada and the United States are in place. In eastern Canada, large decreases in pH and ANC are shown between pre-acidification and 1975, the year of greatest historical deposition. Current-day conditions are much improved from 1975. Under the most likely future acid deposition reduction scenarios, an improvement of pH and ANC is shown in all the regions from current-day levels, but not to pre-acidification levels. Dissolved Ca levels were considerably higher at the height of acidification than under pristine conditions, but will return to pre-acidification levels at most of the sites by the year 2030. The results also show that under proposed control programs, a large number of sites in eastern Canada will not return to ANC values >40 μeq L−1, thought to be suitable for healthy aquatic communities.
Modelling inorganic aluminium with WHAM in environmental monitoring by Neil Cory; Cecilia M. Andrén; Kevin Bishop (1196-1201).
Due to the varying toxicity of different Al species, information about Al concentration and speciation is important when assessing water quality. Modelling Al speciation can support operational monitoring programmes where Al speciation is not measured directly. Modelling also makes it possible to retroactively speciate older samples where laboratory fractionation was not undertaken. Organic-rich waters are a particular challenge for both laboratory analysis and models. This paper presents the modelling of Al speciation in Swedish surface waters using the Windermere Humic Acid Model (WHAM). The model was calibrated with data from operational monitoring, the Swedish national survey of lakes and rivers, and covers a broad spectrum of physical and chemical conditions. Calibration was undertaken by varying the amount of DOC active in binding Al. A sensitivity analysis identified the minimum parameters required as model input variables primarily to be total Al, organic C, pH, F−, and secondly Fe, Ca and Mg. The observed and modelled Ali had no significant differences (Spearman rank, p < 0.01), however, lake samples modelled better than rivers. Samples were placed in the correct toxicological category in 89–95% of the cases. The importance of the size of the calibration data set was assessed, and reducing the calibration data set resulted in poorer correlations, but had little impact on the toxicological placement. Overall, the modelling gave satisfactory results from samples covering a broad spectrum of physical and chemical conditions. This indicates the potential value of WHAM as a tool in operational monitoring of surface waters.
The influence of colloidal material on aluminium speciation and estimated acid neutralising capacity (ANC) by Hans-Christian Teien; Brit Salbu; Frode Kroglund; Lene Sørlie Heier; Bjørn Olav Rosseland (1202-1208).
Cationic Al species (Ali) cause toxic effects towards fish in acidified water. As several factors can influence the Ali-speciation, acid neutralising capacity (ANC) has been applied as an alternative indicator for acidification and effects towards fish. However, the critical range of ANC for biological stress has been shown to be dependent upon the concentration of organic material (DOC). Using in situ size fractionation techniques the influence of particulate and colloidal DOC (0–400 μM) on Ali-speciation and ANC-values was investigated in Norwegian streams. During high flow events with high river transport of DOC the Ali concentration increased by a factor of 2 due to retention of colloidal Al species (>10 kDa), probably organic, in the chromatography column. Ultrafiltration (⩽10 kDa) of water prior to chromatography reduced the influence of non-toxic organic Al-species, on Ali-speciation. The charge balanced ANC-values (ANCcb) were also significantly lower (on average 34 μeq L−1) in ultrafiltered water compared to unfiltered water samples, as base cations were associated with colloidal DOC (>10 kDa to 0.45 μm) and organic acids were not incorporated in the ANCcb estimate. Thus, ANCcb will underestimate the acidification effects towards fish in organic waters increasing with concentration of colloidal DOC present. Alkalinity based ANC-values (ANCalk), which include a fraction of organic acids, were similar in unfiltered and ultrafiltered waters, but higher than ANCcb-values of ultrafiltered samples. Thus, ANCalk-values also underestimate the acidification effects on fish in organic waters. Based on ultrafiltered samples, however, ANCcb-values was negatively correlated with Ali independent of the DOC present and thus a more correct indicator for toxic Al-species.
Speciation of aluminum in circumneutral Japanese stream waters by Masami Kanao Koshikawa; Takejiro Takamatsu; Seiichi Nohara; Hideaki Shibata; Xiaoniu Xu; Muneoki Yoh; Mirai Watanabe; Kenichi Satake (1209-1216).
Speciation of Al, including inorganic monomeric Al (Ali, the sum of aquo, hydroxy and inorganically complexed forms), organic monomeric Al (Alo, the organically complexed form), and colloidal mineral Al (Alc, the fine particulate form that passes through a 0.4-μm pore size membrane filter), was investigated in stream waters (pH 6–8) of 4 watersheds in Japan. Total dissolved Al (Alt, the sum of Alc, Ali and Alo) ranged from 0.03 to 3.31 μM, and Alc was a minor component (<22% of Alt) in most of the streams. Ali was dominant (71% of Alt) in stream waters with low concentrations of Alt (<0.25 μM), while the Alo fraction (37%) was almost as large as the Ali fraction (39%) in the highest class (Alt > 1 μM). In spite of the variation in the range of reactive Al (Alr, the sum of Ali and Alo) in the 4 watersheds (Miomote, 0.03–3.27 μM; Tsukuba, 0.06–0.71 μM; Dorokawa, 0.05–0.71 μM; Tama, 0.03–0.38 μM), the entire data set for Alr could be expressed as a function of the ratio of dissolved organic C (DOC) and Ca: [Al r (μM)] = 0.13 [DOC/Ca (mol/mol)] + 0.11 (r = 0.86, P < 0.001). Alr increased in proportion to the DOC/Ca ratio in Japanese stream waters. Although acidic deposition in Japan has already resulted in elevated concentrations of NO 3 - + SO 4 2 - in stream waters, a high level of Ca (instead of Al) is serving as a major counterion for NO 3 - + SO 4 2 - . However, an additional loading of acidic deposition may result in shortage of Ca and mobilization of Al as a counterion for NO 3 - + SO 4 2 - , and continuous observation of the speciation of Al in Japanese stream waters may reveal future change in the conditions for mobilization of Al from “low Ca and high DOC” to “low Ca and high NO 3 - + SO 4 2 - ”.
Atmospheric deposition of cadmium in the northeastern USA by Stephen A. Norton; Tiffany Wilson; Michael Handley; Erich C. Osterberg (1217-1222).
Lake sediment cores, dated by 210Pb, were collected from Spectacle Pond (SP), Massachusetts, and Side Pistol Lake (SPL) and Sargent Mountain Pond (SMP), Maine, USA. SP is a kettle seepage lake in granitic sand and gravel. SMP is a drainage pond on granite with little soil in the small watershed. SPL is a drainage lake in granitic till. The three cores were analyzed for total Cd. For SP and SMP, maximum concentrations of 1.7 and 3.9 mg/kg, four and eight times background concentrations, respectively, occur in the late 1960s. Accumulation rates reach maximum values concurrently with concentration and are 0.054 and 0.016 μg/cm2/a, more than 10 times background. Concentration and accumulation rate age relationships in SMP and SP are similar for background values, timing and magnitude of increase to peak values, and the decrease nearly to background values since about 1975. The chemical response to decreased atmospheric deposition lags in SPL sediment. Kettle-like lakes more clearly indicate changes in atmospheric deposition than drainage lakes.
Estimation of lead sources in a Japanese cedar ecosystem using stable isotope analysis by Yuko Itoh; Kyotaro Noguchi; Masamichi Takahashi; Toru Okamoto; Shuichiro Yoshinaga (1223-1228).
Anthropogenic Pb affects the environment worldwide. To understand its effect on forest ecosystem, Pb isotope ratios were determined in precipitation, various components of vegetation, the forest floor, soil and parent material in a Japanese cedar (Cryptomeria japonica D. Don) forest stand. The average 206Pb/207Pb ratio in bulk precipitation was 1.14 ± 0.01 (mean ± SD), whereas that in the subsoil (20–130 cm) was 1.18 ± 0.01. Intermediate ratios ranging from 1.15 to 1.16 were observed in the vegetation, the forest floor, and the surface soil (0–10 cm). Using the 206Pb/207Pb ratios, the contribution of anthropogenic sources to Pb accumulated in the forest were estimated by the simple binary mixing model. Sixty-two percent of the Pb in the forest floor, 71% in the vegetation, and 55% in the surface soil (0–10 cm) originated from anthropogenic sources, but only 16% in the sub-surface soil (10–20 cm) was anthropogenic. These results suggest that internal Pb cycling occurs mainly between surface soil and vegetation in a Japanese cedar ecosystem, and that anthropogenic Pb strongly influences Pb cycling. Although the Japanese cedar ecosystem has a shallow forest floor, very little atmospherically derived Pb migrated downward over 10 cm in depth.
Changes in fish mercury concentrations over 20 years in an acidified lake subject to experimental liming by Martti Rask; Roger I. Jones; Marko Järvinen; Anna Paloheimo; Maiju Salonen; Jari Syväranta; Matti Verta (1229-1240).
Lake Iso Valkjärvi (southern Finland, Europe) was divided in two with a plastic curtain in 1991. One half was neutralized with CaCO3, and the other acted as a control. Mercury concentrations of perch (Perca fluviatilis) and northern pike (Esox lucius) in the limed and control side of the lake were studied both before and after the treatment. Average Hg concentrations of perch and pike were 0.40 and 1.2 μg g−1 (ww) in the early 1980s and 0.25 and 0.72 μg g−1 (ww) a decade later at the time of liming. Ten years after the liming the Hg concentrations of perch in the limed and control sides of the lake were 0.21 and 0.28 μg g−1 (ww) and those of pike were 0.69 and 0.43 μg g−1 (ww), respectively. Nitrogen isotope ratios (δ 15N) for perch in the sampling period 2002–2004 showed wide variation suggesting variable trophic positions for individual fish. Pike formed two groups according to their δ 15N-values, suggesting that zoobenthos dominated the diet of pike around 20 cm in length and fish that of the larger pikes. Because the δ 15N-values of fish were at similar levels in the limed and control sides of L. Iso Valkjärvi, differences in food web structure cannot account for the different fish Hg concentrations. A more likely explanation is water quality induced differences in the dynamics and bioavailability of Hg, leading to decreased formation of methyl Hg.
Manganese cycling in central Ontario forests: Response to soil acidification by Shaun A. Watmough; M. Catherine Eimers; Peter J. Dillon (1241-1247).
Soil acidification results in enhanced mobilization of many potentially phytotoxic metals, including Mn. In Canada, there is also concern that emissions of Mn from the gasoline additive methylcyclopentadienyl manganese tricarbonyl (MMT) may contribute to the environmental risk posed by Mn. As a first step toward understanding the risk posed by Mn in acidifying forest systems in Ontario, the authors sampled foliage and soil from 46 forest plots in central Ontario that encompassed a soil pH range of 3.9–8.1. Increased availability of Mn at lower soil pH was clearly demonstrated, as water-extractable Mn increased and molar ratios of Ca:Mn in foliage decreased at sites with lower soil pH, although Mn availability appears to be determined by both soil pH and Mn content in soil. The cycling of Mn was studied in detail at a representative acidified coniferous forest catchment (Plastic Lake) in central Ontario. Between 1980 and 2002, Mn bulk deposition at PC ranged from 3 to 7 mg m−2 a−1 and there was no evidence that Mn deposition increased over this time period despite increased usage of MMT. Temporal patterns of Mn concentrations in stream water draining the Plastic Lake catchment were highly correlated to SO 4 2 - levels in stream water (r 2 = 0.90), indicating that acid leaching is currently driving Mn losses. Furthermore, Mn outputs in stream water draining the terrestrial catchment exceeded bulk deposition inputs, whereas the lake was a net sink for Mn, due to retention in lake sediment. Because Mn availability is determined by soil pH and the Mn content in soil, net losses of Mn from the terrestrial catchment indicate that Mn levels in soil and stream water will ultimately decline over the long-term, and therefore Mn is unlikely to have a negative impact on forests in this region.
Effects of atmospheric NO x on biocalcarenite coated with different conservation products by Mara Camaiti; Simone Bugani; Elena Bernardi; Luciano Morselli; Mauro Matteini (1248-1254).
One of the most important factors of calcareous stone decay is the chemical attack caused by atmospheric pollutants dissolved in water, in particular acidic gases such as SO x , NO x and CO2. The treatment of stone artefacts with hydrophobic products reduces the water uptake of the rock and is, therefore, considered a “protective treatment”. The aims of the present study were the observation of the effects of NO x on a biocalcarenite (Lecce stone) and the evaluation of the performance of protective products (Paraloid B72 and a fluoroelastomer) normally used in stone conservation. A system for the simulation of accelerated ageing has been assembled and the Lecce stone samples, treated with polymeric products, have been exposed to NO2 (nearly 1 ppm) during thermo hygrometric cycles. The nitrite and nitrate salts formed on the specimens have been determined by ion chromatography. Both the polymeric products tested have given high hydrophobic properties to the stone, even if they do not assure satisfactory protection toward NO2 exposure. Actually, their protective efficacy, or ability to reduce the acidic attack of NO2, quickly decreases when the ageing period increases. Paraloid B72 seems more effective than fluoroelastomer because, on the samples treated with the latter, higher amounts of nitrites and nitrates have always been detected. In contrast, non-treated samples – used as reference – have shown a constant increase in the amount of nitrates and nitrites during ageing. However, the surface analyses of the stone samples, by environmental SEM and μ-laser profilometry, did not show any change in superficial morphology after the ageing, suggesting that NO2 acts inside the pores.
Particulate air pollution in a small settlement: The effect of local heating by Martin Braniš; Markéta Domasová; Pavla Řezáčová (1255-1264).
Mass concentrations of PM10, PM2.5, and black smoke (BS) were measured in April 2003 during a 3-week campaign in a small village and at a nearby background location in the central part of the Czech Republic. In a pilot analysis, concentrations of selected trace elements (Al, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Sr, Cd, Sb, Cs, Pb) in the collected aerosol were determined by means of ICP-MS. Average concentrations of both PM fractions and BS were higher in the village (37, 26 and 26 μg m−3) than at the background location (26, 19 and 11 μg m−3) for PM10, PM2.5 and BS, respectively. Both PM10 and PM2.5 were reasonably correlated in the village (r = 0.80) and also at the background location (r = 0.79). Correlation between same fractions from the village and from the background site were even higher (r = 0.97 and r = 0.95 for the PM10 and PM2.5, respectively) suggesting that most of the aerosol in both locations may be influenced by similar sources. The ratio between PM10 and PM2.5 showed that sources in the village contributed about 33% and 35% to local aerosol concentration for PM10 and PM2.5, respectively. When the data from the two rural locations were compared with corresponding 24-h averages of PM10 concentrations obtained for the period of the campaign from fixed site monitors situated near larger towns, the highest concentration was found in Prague the Czech capital (49 μg m−3) followed by a district town Beroun (41 μg m−3) and the village (37 μg m−3). The lowest PM10 concentration was found in the village background (26 μg m−3). Elemental analysis revealed higher concentrations for most of the elements characteristic of combustion aerosol (namely Zn, Pb, As, Mn and Ti) in the PM collected in the village. The results support the idea that traditional heating in villages may contribute a great extent to local air pollution and may represent an important problem.
Ecological impacts of air pollution from road transport on local vegetation by Keeley L. Bignal; Mike R. Ashmore; Alistair D. Headley; Kirstin Stewart; Katherina Weigert (1265-1271).
Motor vehicles emit a cocktail of pollutants and are a major contributor to ground-level air pollution, but little is known regarding the ecological impacts of air pollution from roads on the surrounding vegetation. Data are presented on vegetation at three sites adjacent to two major motorways in the UK, comprising two woodland sites and one blanket bog site. Surveys of oak and beech tree health (at the woodland sites) and species composition (at the blanket bog site) were undertaken along transects away from the motorway.The oak tree health survey found increased defoliation and insect damage near to the motorway, and the beech tree health survey also found poorer crown condition close to the motorway. Vascular species composition showed a trend towards species adapted to higher N availability close to the motorway, while the moss Polytrichum commune showed a significant decline in frequency with distance from the motorway. The effect of the road was estimated to extend to approximately 100 m at these three sites; this distance was consistent with the measured profile of NO2, which declined to background levels at about 100 m. The results suggest that emissions of air pollutants can have significant ecological impacts on sensitive sites within 100 m of major roads.