Secondary air pollutants

The study has been performed in a supposedly clean-air region of a Northern Finnish forest with a homogeneous stand of Scots pine. Stomatal epicuticular wax layer erosion is described using a classification system of five erosion stages. The percentage of stomatal wax within each erosion stage is calculated and the results are treated statistically, which makes the morphological study of the needle surface semi-quantitative. Severe wax degradation has already been found in the current year, increasing with the age of the needles. In this area, the wax layer erosion is correlated with secondary air pollutants, as analyses have shown high trichloroacetate (TCA) levels in needles from the same trees. The wax layer analyses are in accordance with earlier findings which have demonstrated differences in tolerance to TCA.     

Means to improve the effect of in situ bioremediation of contaminated soil: an overview of novel approaches

Different aspects of bacterial degradation of organic contaminants in soil, and how to improve the efficiency and reproducibility is discussed in this review. Although bioremediation in principle includes the use of any type of organism in improving the condition of a contaminated site, most commonly bacteria are the degraders and other organisms, such as soil animals or plant roots, play a role in dissemination of bacteria and, indirectly, plasmids between bacteria, and in providing nutrients and co-substrates for the bacteria active in the degradation process. There are a number of different procedures that have been tested more-or-less successfully in attempts to improve reliability, cost efficiency and speed of bioremediation. The methods range from minimal intervention, such as mere monitoring of intrinsic bioremediation, through in situ introduction of nutrients and/or bacterial inocula or improvement of physico-chemical conditions, all the way to excavation followed by on site or ex situ composting in its different varieties. In the past the rule has been that more intervention (leading to higher costs) has been more reliable, but novel ideas are continuously tried out, both as a means to come up with new truly functional applications and also as a line of studies in basic soil microbial ecology. Both approaches generate valuable information needed when predicting outcome of remediation activities, evaluating environmental risks, deciding on cleaning-up approaches, etc. The emphasis of this review is to discuss some of the novel methods for which the value has not been clearly shown, but that in our view merit continued studies and efforts to make them work, separately or in combination.     

Exposure of garbage truck drivers and maintenance personnel at a waste handling centre to polycyclic aromatic hydrocarbons derived from diesel exhaust

Exposure to diesel exhaust was evaluated in summer and winter by measuring vapour and particle phase polycyclic aromatic hydrocarbons (PAHs). Fifteen PAHs were simultaneously determined from the air samples obtained from truck drivers collecting household waste and maintenance personnel at a waste handling centre. The major compounds analysed from the personal air samples of exposed workers were naphthalene, phenanthrene and fluorene. The total PAH exposure (sum of 15 PAHs) of garbage truck drivers ranged from 71 to 2,660 ng m(-3) and from 68 to 900 ng m-3 in the maintenance work. The exposure of garbage truck drivers to benzo[a]pyrene (B[a]P) ranged from the mean of 0.03 to 0.3 ng m(-3) whereas no B[a]P in control samples or in those collected from maintenance workers was detected. A statistically significant difference in diesel-derived PAH exposure between the garbage truck drivers and the control group in both seasons (in summer p = 0.0022, degrees of freedom (df) 70.5; and in winter p < 0.0001, df = 80.4) was observed. Also, a significant difference in PAH exposure between the garbage truck drivers and the maintenance workers (in summer p < 0.0001, df = 50.1; and in winter p < 0.0001, df = 44.2) was obtained.     

Effect of birch (Betula spp.) and associated rhizoidal bacteria on the degradation of soil polyaromatic hydrocarbons, PAH-induced changes in birch proteome and bacterial community

Two birch clones originating from metal-contaminated sites were exposed for 3 months to soils (sand-peat ratio 1:1 or 4:1) spiked with a mixture of polyaromatic hydrocarbons (PAHs; anthracene, fluoranthene, phenanthrene, pyrene). PAH degradation differed between the two birch clones and also by the soil type. The statistically most significant elimination (p ≤ 0.01), i.e. 88% of total PAHs, was observed in the more sandy soil planted with birch, the clearest positive effect being found with Betula pubescens clone on phenanthrene. PAHs and soil composition had rather small effects on birch protein complement. Three proteins with clonal differences were identified: ferritin-like protein, auxin-induced protein and peroxidase. Differences in planted and non-planted soils were detected in bacterial communities by 16S rRNA T-RFLP, and the overall bacterial community structures were diverse. Even though both represent complex systems, trees and rhizoidal microbes in combination can provide interesting possibilities for bioremediation of PAH-polluted soils.     

Haloacetic acids,phytotoxic secondary air pollutants

Haloacetic acids are atmospheric oxidation products of airborne C₂-halocarbons which are important solvents and propellants. Levels of trichloroacetate (TCA) in conifer needles from mountain ranges in Germany (Black Forest, Erzgebirge) and from two sites in Finland are compared; TCA is present in conifer needles at concentrations up to 0.7 μmol/kg, MCA up to 0.2 μmol/kg. At the Finnish sites, TCA-concentrations and branch degeneration symptoms of Scots pine are correlated. Monochloroacetate (MCA) has been determined in needle samples from Southern Germany in concentrations exceeding its phytotoxicity threshold towards photoautotrophic organisms. Data on atmospheric chloroacetate levels in Germany are also given; ambient air levels of chloroacetic acids range from about 2 pmol/m³ (TCA) to 390 pmol/m³ (MCA). TCA and dichloroacetic acid (DCA) arise from atmospheric oxidation of airborne C₂-chlorocarbons, while the source of MCA is not yet known; several tentative pathways are suggested.