Marginal bleaching of thalli of Rhizocarpon as evidence for acid rain in the Norra Storfjället, Sweden

Recent lichen surveys in the foreland of The Syterb?cken glacier reveal that the crustose lichens, principally species of Rhizocarpon section Rhizocarpon, exhibit marginal bleaching, readily distinguishable from normal pigmented forms. The largest elliptical thallus of Rhizocarpon measured 290 mm maximum diameter on a bedrock outcrop beyond the margin of Little Ice Age moraines in the upper Syterb?cken Valley. Many small and large thalli of Rhizocarpon suffered damage to the periphery of individual thalli. We examine here some of the possible hypotheses explaining these occurrences. Among others, these are bedrock lithology, ice crystal blasting, long-term snowbank cover, ultraviolet exposure and acid rain. While at this time none of the possibilities can be ruled out entirely, acid rain would appear to be at least one of the factors involved. Acid rain, which is known to produce a soil pH as low as 3.3 in the field area, appears to provide a high input of H(+) ions that the lichen algal component cannot withstand. However, the lack of similar effects on associated foliose or fruticose forms raises the possibility that perhaps two or more factors specific to the environment of Rhizocarpon are operating.     

The interactive effects of low pH, toxic metals, and DOC on a simulated temporary pond community

The effects of pH, potentially toxic metals, and dissolved organic carbon (DOC) on a freshwater, palustrine wetland assemblage (three amphibian species, one mosquito genus, and 18 genera of algae) were examined in 500 liter outdoor mesocosms. The design was fully factorial and exposure levels were set to represent concentrations that occur naturally in temporary ponds in central Pennsylvania, an acid-impacted region of the USA. Water chemistry was precisely regulated by use of an artificial pond water rather than using stream water or well water with partially unknown composition. Jefferson (Ambystoma jeffersonianum) and spotted salamanders (A. maculatum) were negatively impacted by low pH and high metal concentrations. Wood frogs (Rana sylvatica) were negatively impacted by high DOC and low pH. These negative effects included increased time to metamorphosis and decreased survival and wet body mass at metamorphosis. Mosquito emergence was unaffected by pH, metals, or DOC. All three abiotic factors (metals, pH, and DOC) interacted to determine algal taxonomic composition. Hence, abiotic conditions may determine amphibian reproductive success both directly and indirectly, via effects on algae, since a primary food source of salamanders, zooplankton, are affected by changes in algal composition. These complex interactions should be considered in evaluating the possible toxicity of pond waters to fauna and flora. Until now, pH alone has been considered the primary limiting factor for amphibians breeding in temporary ponds.     

A laboratory exposure procedure for screening pulp and paper mill effluents for the potential of causing increased mixed function oxidase activity in fish

To better understand the relationships between pulp manufacturing processes and mixed function oxidase (MFO) enzyme induction in fish, a practical and standardized exposure procedure is required. This study was undertaken to develop a laboratory-based exposure procedure to quantify the relative MFO induction potencies of different types of pulp and paper mill effluents. One major consideration in developing the procedure was to ensure that the protocol was practical so that tests could be performed in a short time, with small volumes of effluents and using simple experimental conditions. A series of concentration-response and time-course experiments were conducted to find the minimum time and effluent concentration which could distinguish the ability of different effluents to cause significant MFO induction in rainbow trout in the laboratory. Experiments were also conducted to determine the effects of biotic and abiotic factors such as loading density, fish size and feeding regime. This study showed that the exposure of rainbow trout in the laboratory to 10% concentration of secondary-treated effluent for 96 h caused significant increases in hepatic MFO activity. The magnitude of MFO induction was comparable to other field and laboratory observations. While fish size, loading density and feeding regime were found to affect the test results, consistent responses within a laboratory using this protocol are possible, provided that these factors are standardized. Therefore, the short-term exposure approach described in this paper could be a relevant tool for assessing the ability of different types of pulp and paper mill effluents to cause MFO induction in fish.     

Linear least squares method for time series analysis with an application to a methane time series

A simple method of time series analysis, based upon linear least squares curve fitting, is developed. The method's advantages and disadvantages are discussed, and an example is presented using the Vostok Core methane record.     

Management options to limit nitrate leaching from grassland

Nitrate leaching can be reduced by the adoption of less intensive grassland systems which, though requiring a greater land area to achieve the same agricultural output, result in less nitrate leaching per unit of production than do intensively managed grasslands. The economic penalties associated with reductions in output can be partly offset by greater reliance on symbiotic nitrogen fixation and the use of clover-based swards in place of synthetic N fertilisers. Alternatively, specific measures can be adopted to improve the efficiency of nitrogen use in intensively managed systems in order to maintain high outputs but with reduced losses. Controls should take account of other forms of loss and flows of nitrogen between grassland and other components of the whole-farm system and, in most instances, should result in an overall reduction in nitrogen inputs. Removing stock from the fields earlier in the grazing season will reduce the accumulation of high concentrations of potentially leachable nitrate in the soil of grazed pastures but will increase the quantity of manure produced by housed animals and the need to recycle this effectively. Supplementing grass diets with low-nitrogen forages such as maize silage will reduce the quantity of nitrogen excreted by livestock but may increase the potential for nitrate leaching elsewhere on the farm if changes to cropping patterns involve more frequent cultivation of grassland. Improved utilisation by the sward of nitrogen in animal excreta and manures and released by mineralisation of soil organic matter will permit equivalent reductions to be made in fertiliser inputs, provided that adequate information is available about the supply of nitrogen from these non-fertiliser sources.     

Pharmacokinetic model of dioxin and furan levels in adipose tissue from Sawmill work involving chlorophenate fungicides

Sawmill workers in British Columbia (B.C.), Canada, have been exposed to chlorophenate fungicides which are known to be contaminated with polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). Due to concern about the potential of these workers to have significant body burdens of PCDD/Fs, and the absence of measurements in these worker, a single-compartment pharmacokinetic model was developed to estimate the concentration of PCDD/Fs in the fat tissue of the sawmill workers. Data from a large cohort of B.C. sawmill workers and literature-based data on chlorophenate exposures and PCDD/F concentrations in chlorophenates were used in Monte Carlo simulations to predict a PCDD/F body burden distribution. The median concentrations of HxCDF and HpCDF predicted using the model for the B.C. sawmill worker population exceeded the range measured in unexposed populations. PeCDF and OCDF concentrations exceeded the range measured in unexposed populations at the 70th percentile of the model-predicted distribution, and PeCDD at the 90th percentile. The primary limitation of the model was the scarcity of input data about actual dermal and inhalation exposures to chlorophenates.     

Growth and nutrition of Quercus rubra L. seedlings and mature trees after three seasons of ozone exposure

Seedling growth and nutritional status have been shown to be sensitive to ozone, but the influence of multi-season ozone exposure on mature tree growth and nutrition has not been examined. To determine if seedlings and mature trees were similarly affected by ozone exposure, growth and nutrient concentrations in northern red oak (Quercus rubra L.) 4-year-old seedlings and 32-year-old mature trees were examined after treatment with subambient, ambient and twice ambient concentrations of ozone for three growing seasons. SUM00 values summed over the three growing seasons were 147, 255 and 507 ppm-h, respectively, for the subambient, ambient and twice ambient exposures. For mature trees, no influence of ozone treatment on lower stem diameter growth, stem growth within the mid-canopy and foliar biomass was observed. Seedling height was increased by ozone, but biomass and diameter were unaffected. A reduction in the specific leaf weight of leaves in response to ozone coincident with the loss of recurrent flushing was observed in seedlings. Ozone exposure reduced foliar nitrogen concentrations and increased woody tissue nutrient concentrations in seedlings and mature trees at the end of the third growing season. These results suggest an influence of ozone on retranslocation processes in seedlings and mature trees.     

Cationic surfactant as a sensitizer for the spectrophotometric determination of hydrogen sulphide in air and evaluation of a new absorbing medium containing triethanolamine-zinc acetate-sodium hydroxide

An extractive spectrophotometric method for the determination of trace amounts of hydrogen sulphide after fixing the gas in triethanolamine (TEA)-zinc acetate-sodium hydroxide solution is described. The method is based on the reaction of iodate with hydrogen sulphide in the presence of acid and excess chloride ion leading to the formation of ICl2- species which is used to iodinate 2',7'-dichlorofluorescein to form 2',7'-dichloro-4',5'-diiodofluorescein. The iodinated product formed is extracted into an organic solvent and sensitized by equilibrating with a cationic surfactant, cetrimide, in the presence of acetate buffer (pH 5.9 +/- 0.1). The colour system obeys Beer's law over the range 0-1 microg of hydrogen sulphide and the relative standard deviation is 2.4% for 10 determinations at 0.75 microg of hydrogen sulphide. The effect of interfering gases on the determination is discussed. The proposed absorbing solution has been evaluated using a hydrogen sulphide permeation device. This absorbing solution has an absorption efficiency of > 93% at a flow rate of 1.5 litre min(-1) for a sampling period of 2 h. The fixed H2S is stable for 40 days. The method has been applied to determine residual H2S levels in a laboratory fume hood and in the vicinity of sewage pumping station. The method can be used to determine as little as 0.05 microg of hydrogen sulphide.     

Biomonitoring of air pollutants from traffic and industries employing Ramalina ecklonii (Spreng.) Mey. and Flot. in Córdoba, Argentina

The lichen Ramalina ecklonii (Spreng.) Mey. and Flot. was transplanted to 29 biomonitoring sites in the southeastern area of Córdoba, Argentina and tested for chlorophyll a, phaeophytin a, conjugated dienes concentration, malondialdehyde, soluble protein content and sulfur accumulation. The biomonitoring sites were determined according to (i) vehicular traffic levels, and (ii) industrial density, i.e. number and type of industries (small and medium) close to each of the sites. Each of the two groups were then broken down into three categories which provided a basis for performance analysis and quantification of the chemical parameters in the biomonitor. A pollution index (P.I.) was calculated based on the ratio of phaeophytin a to chlorophyll a and ratio of sulfur, malonaldehyde and conjugated dienes in transplanted specimens to sulfur, malonaldehyde and conjugated dienes in the freshly picked specimens. Significant differences were observed in sulfur content and P.I. in lichen samples that had been transplanted to sites with different vehicular traffic levels. At the same time, significant differences in the phaeophytin a concentration, phaeophytin a/chlorophyll a ratio and P.I. were observed at sites characterized by different levels of industrial density (all with low-to-medium traffic).