title: Natural formation and degradation of chloroacetic acids and volatile organochlorines in forest soil--challenges to understanding.
abstract: OBJECTIVE
  The anthropogenic environmental emissions of chloroacetic acids and volatile organochlorines have been under scrutiny in recent years because the two compound groups are suspected to contribute to forest dieback and stratospheric ozone destruction, respectively. The two organochlorine groups are linked because the atmospheric photochemical oxidation of some volatile organochlorine compounds is one source of phytotoxic chloroacetic acids in the environment. Moreover, both groups are produced in higher amounts by natural chlorination of organic matter, e.g. by soil microorganisms, marine macroalgae and salt lake bacteria, and show similar metabolism pathways. Elucidating the origin and fate of these organohalogens is necessary to implement actions to counteract environmental problems caused by these compounds.
  
  
  METHODS
  While the anthropogenic sources of chloroacetic acids and volatile organochlorines are relatively well-known and within human control, knowledge of relevant natural processes is scarce and fragmented. This article reviews current knowledge on natural formation and degradation processes of chloroacetic acids and volatile organochlorines in forest soils, with particular emphasis on processes in the rhizosphere, and discusses future studies necessary to understand the role of forest soils in the formation and degradation of these compounds.
  
  
  CONCLUSIONS
  Reviewing the present knowledge of the natural formation and degradation processes of chloroacetic acids and volatile organochlorines in forest soil has revealed gaps in knowledge regarding the actual mechanisms behind these processes. In particular, there remains insufficient quantification of reliable budgets and rates of formation and degradation of chloroacetic acids and volatile organochlorines in forest soil (both biotic and abiotic processes) to evaluate the strength of forest ecosystems regarding the emission and uptake of chloroacetic acids and volatile organochlorines, both on a regional scale and on a global scale.
  
  
  CONCLUSIONS
  It is concluded that the overall role of forest soil as a source and/or sink for chloroacetic acids and volatile organochlorines is still unclear; the available laboratory and field data reveal only bits of the puzzle. Detailed knowledge of the natural degradation and formation processes in forest soil is important to evaluate the strength of forest ecosystems for the emission and uptake of chloroacetic acids and volatile organochlorines, both on a regional scale and on a global scale.
  
  
  CONCLUSIONS
  As the natural formation and degradation processes of chloroacetic acids and volatile organochlorines in forest soil can be influenced by human activities, evaluation of the extent of this influence will help to identify what future actions are needed to reduce human influences and thus prevent further damage to the environment and to human health caused by these compounds.
authors.affiliation: The Swedish Institute for Climate Science and Policy Research, ITUF, Linköpings universitet, 601 74 Norrköping, Sweden. frank.laturnus@ituf.liu.se
authors.forename: Frank
authors.initials: F
authors.lastname: Laturnus
authors.forename: Isabelle
authors.initials: I
authors.lastname: Fahimi
authors.forename: Milan
authors.initials: M
authors.lastname: Gryndler
authors.forename: Anton
authors.initials: A
authors.lastname: Hartmann
authors.forename: Mathew R
authors.initials: MR
authors.lastname: Heal
authors.forename: Miroslav
authors.initials: M
authors.lastname: Matucha
authors.forename: Heinz Friedrich
authors.initials: HF
authors.lastname: Schöler
authors.forename: Reiner
authors.initials: R
authors.lastname: Schroll
authors.forename: Teresia
authors.initials: T
authors.lastname: Svensson
mesh_terms: D000085:Acetates / Q000737:chemistry*; D001673:Biodegradation, Environmental; D006801:Humans; D006843:Hydrocarbons, Chlorinated / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis*; D014197:Trees; D014835:Volatilization
chemical_list: D000085:Acetates; D006843:Hydrocarbons, Chlorinated; D012989:Soil Pollutants; C006972:chloroacetic acid