Effects of heavy-metal and sulphur deposition on the chemical properties of forest soil in the vicinity of a Cu-Ni smelter, and means of reducing the detrimental effects of heavy metals.

Dissertation + appendices

Validation of chemical analyses of atmospheric deposition on forested sites in Europe: 2. DOC concentration as an estimator of the organic ion charge

A Working Group on Quality Assurance/Quality Control of analyses in laboratories active in the chemical analysis of atmospheric deposition and soil water has been created within the framework of the Integrated Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (UN-ECE/ICP Forests) and the EU/Forest Focus Programme (Regulation 2152/2003). This paper is a follow up to an earlier paper dealing with the validation of chemical analyses, in which validation techniques (ion balance, comparison between measured and calculated conductivity, Na/Cl ratio and relationship between different forms of N) were tested on a set of real analysis data obtained from different laboratories. This paper focuses on the validation of chemical analysis of samples containing high dissolved organic carbon (DOC) concentrations (> 5 mg C L-1), where the ion balance criterion fails because of the presence of weak organic acids. About 6000 chemical analyses of bulk open field, throughfall and stemflow samples, which contained complete sets of all ion concentrations, conductivity and DOC, produced in 8 different laboratories, were used to calculate empirical relationships between DOC and the difference between the sum of cations and the sum of anions, with the aim to evaluate a formal charge per mg of organic C. Regression coefficients were obtained for data from each laboratory, as well as for all the data combined. The coefficients were further tested using an independent set of data from each country. The differences between the individual laboratory and the overall regression coefficients are discussed. The results are also considered in the light of formal charge values for DOC/TOC obtained in studies on freshwater. The formal DOC charge proved to be useful for estimating the contribution of organic acids in the ion balance test, thus considerably improving the applicability of the ion balance as a validation criterion for samples with high DOC values

In Situ Bioremediation through Mulching of Soil Polluted by a Copper–Nickel Smelter

Received for publication September 8, 2000. Bioremediation of a heavy metal–polluted soil was investigated in a 3-yr field experiment by adding mulch to a polluted forest floor. The mulch consisted of a mixture of compost and woodchips. The remediation treatment decreased the toxicity of the soil solution to bacteria as determined by the [3H]-thymidine incorporation technique, that is, by measuring the growth rate of soil bacteria extracted from unpolluted humus after exposing them to soil solution containing heavy metals from the experimental plots. Canonical correlation analysis was performed in order to identify the chemical and microbiological changes in the soil. The pH of the mulched organic layer increased by one unit. The concentration of complexed Cu increased and that of free Cu2+ decreased in the soil solution from the mulch treatment. According to basal respiration and litter decomposition, microbial activity increased during the 3 yr following the remediation treatment. The [3H]-thymidine incorporation technique was also used to study the growth rate and tolerance of bacteria to Cu. The bacterial growth rate increased and the Cu tolerance decreased on the treated plots. The structure of the microbial community, as determined by phospholipid fatty acid (PLFA) analysis, remained unchanged. The results indicate that remediation of the polluted soil had occurred, and that adding a mulch to the forest floor is a suitable method for remediating heavy metal–polluted soil