Monitoring of chlorine in the forest ecosystem – its cycling and effects

The aim of the project is to gain data for the elucidation of processes taking place during the decay of organic matter in forest ecosystems (microbially as well as abiotically) with the participation of chlorine. To attain this, we will monitor chlorine in forest ecosystems and will conduct laboratory experiments providing data required and indicated in part in the literature (Asplund et al. 1989, 1993a, b, 1994, Asplund 1995, Öberg 1998, 2002, 2003, Öberg et al. 1997, 1998, Öberg and Groen 1998, Hoekstra et al. 1999a,b, Fahimi et al. 2003, Laturnus et al. 2005). These breakdown processes were ascribed in particular to the degradation capabilities of microorganisms, fungi and their extracellular enzymes such as cellulases and peroxidases (Eriksson et al. 1986 a 1990, de Jong and Field 1997, Baldrián 2004, Daniel et al. 1994, Vyas et al. 1994). During these hitherto little explored processes not only is CO₂ emitted into the atmosphere, thus contributing to climate change (Adams and Piovesan 2005), but volatile chlorinated hydrocarbons (VOCl) are also released. Methyl chloride and chloroform belong to the key VOCl compounds damaging the stratospheric ozone layer or contaminating water sources and thus affecting human health.
The above mentioned references and also our recent results (Forczek et al. 2001, Matucha et al. 2003a,b, 2004, 2006, 2007a,b) show that the formation and microbial degradation of AOX, including CAA, proceeds in forest soils, where the presence of chloroperoxidases (CPO) was indicated. Chloride and CPO participate in the chlorination of litter, wood residues, lignin and humic substances in the soil. Until now, studies of chlorinated soil organic matter have focused on the changes in the total amount of bound chlorine (TOX and AOX). To the formation of particular chlorinated organic compounds corresponding attention has not yet been paid, e.g. chloroform and CAA have hitherto been determined together and more or less only qualitatively. The research has also focused mainly on coastal countries such as Sweden, Denmark, the Netherlands and Germany, where a relatively high chloride input in sea salt results in considerable quantities of these compounds in forest ecosystems. Because a net of intensively monitored forest plots in the Czech Republic already exists – in the frame of the international cooperative program “ICP Forests” for assessment of the influence of air pollution on forests – we propose to utilize this net also for assessment of chloride and chlorinated compounds in the forest ecosystem, including in water (precipitation, soil, ground, drainage, and run-off water).
Little attention has been paid to the microbiological aspects of breakdown processes of soil organic matter (Gryndler et al. 2008). The published data (including our recent findings) show that the function of chlorine in decomposition processes is more significant than previously assumed. The geographic situation of the Czech Republic implies that the concentration of chlorine and corresponding rate of chlorination in forest soil are lower than in coastal countries such as Norway, where sea salt inputs are ecologically important (Aamlid and Horntvedt 2002, Lange et al. 2006); however some preliminary results of pilot studies give evidence of a relatively high content of chloride (over 50 mg/kg dw) and AOX (over 200 mg/kg dw) in soil as well. Low chloride content (less than 10 mg/kg) can be a consequence of intensive natural leaching of chlorine from soil (Uhlířová and Šebková 2001 and further unpublished results), while plots influenced by winter road salting have many times higher concentration (hundreds of mg/kg Cl).
The project should answer the following questions:

a. what levels of chloride and AOX are present in the forest ecosystems in the Czech Republic (compared to Norway)?
b. does chlorine contribute to the SOM degradation?
c. does chloride influence microbial activity in the forest soil?
d. do AOX from forest ecosystems contribute in considerable degree to AOX levels in surface waters (in comparison with industrial and communal waste waters)?