The production and degradation of trichloroacetic acid in soil: results from in situ soil column experiments

Previous work has indicated that the soil is important to understanding biogeochemical fluxes of trichloroacetic acid (TCA) in the rural environment, in forests in particular. Here, the hydrological and TCA fluxes through 22 in situ soil columns in a forest and moorland-covered catchment and an agricultural grassland field in Scotland were monitored every two weeks for several months either as controls or in TCA manipulation (artificial dosing) experiments. This was supplemented by laboratory experiments with radioactively-labelled TCA and with irradiated (sterilised) soil columns. Control in situ forest soil columns showed evidence of net export (i.e. in situ production) of TCA, consistent with a net soil TCA production inferred from forest-scale mass balance estimations. At the same time, there was also clear evidence of substantial in situ degradation within the soil (~70% on average) of applied TCA. The laboratory experiments showed that both the formation and degradation processes operate on time scales of up to a few days and appeared related more with biological rather than abiotic processes. Soil TCA activity was greater in more organic-rich soils, particularly within forests, and there was strong correlation between TCA and soil biomass carbon content. Overall it appears that TCA soil processes exemplify the substantial natural biogeochemical cycling of chlorine within soils, independent of any anthropogenic chlorine flux

Natural formation and degradation of chloroacetic acids and volatile organochlorines in forest soil: challenges to understanding

Goal, Scope and Background. 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. Main Features. 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. Results and Discussion. 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. Conclusion. 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. Recommendation and Perspective. 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

Analýza represivního zabezpečení PO zámku v Klášterci nad Ohří - muzeum porcelánu

Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta hornicko-geologická. Institut bezpečnostního inženýrství (547