A leaching experiment, where liquid manure spiked with Salmonella enterica serovar Typhimurium (T... more A leaching experiment, where liquid manure spiked with Salmonella enterica serovar Typhimurium (Tet + ) DSM554 was applied to soil surfaces, was conducted on intact soil monoliths (60 cm in diameter and 100 cm long). A total of 6.5 × 10 10 CFU was applied to each column. We found that Salmonella serovar Typhimurium could be transported to a 1-m depth in loamy soil at concentrations reaching 1.3 × 10 5 CFU/ml of leachate. The test strain was found in concentrations ranging from 300 to 1.3 5 cells/ml in loamy soil throughout the 27 days of the experiment, while concentrations below 20 cells/ml were sporadically detected in the leachates from sandy monoliths. Real-time PCR targeting invA DNA showed a clear correspondence between the total and culturable numbers of cells in the leachate, indicating that most cells leached were viable. On day 28, distribution of Salmonella serovar Typhimurium at five depths in the four monoliths was determined. The highest recovery rate, ranging from 1.5...
The aim of our study was to estimate emissions of natural chloroform from soil in arctic and suba... more The aim of our study was to estimate emissions of natural chloroform from soil in arctic and subarctic ecosystems. We therefore determined the seasonal and spatial variation in soil-to-air fluxes of chloroform at 11 sites representing typical vegetation types in Greenland (Narsarsuaq, Kangerlussuaq and Disko Island) and northern Scandinavia (Abisko). Fluxes of chloroform showed a large variation, ranging from 4 to 2850 ng m−2 h−1. The local variation within a 12-m transect at each site was frequently five to tenfold, which emphasizes the need for multiple measurements even within field plots that seem homogenous. At one site, the transect was extended to 58 m and 40 measurements and a large number of environmental parameters were recorded as well. In this transect, collars separated by 60 cm distances were in most cases similar but at 3 m distance variation was as big as between collars with greater separation. CO2 flux was the parameter that showed the most correlation to the chloroform flux in the extended transect. Chloroform fluxes also varied over the year, but this variation was smaller than the variation between the five collars of each site and much smaller than the variation between sites. All arctic sites except a non-tussock sedge wetland showed low fluxes. A subarctic pine forest had by far the highest fluxes. Subarctic and boreal coniferous forests generally seem to be important global sources of biogenic chloroform to the troposphere. The future spatial extent of coniferous forest in the subarctic to arctic region, in response to climate change, may be the key driver of future chloroform emissions from these areas.
Pollution with organochlorines has received major attention due to various environmental effects,... more Pollution with organochlorines has received major attention due to various environmental effects, but it is now increasingly recognized, that they also take part in biogeochemical cycles and that natural background concentrations exist for several chlorinated compounds. We here report the natural occurrence and cycling of organic compounds with a trichloromethyl moiety in common. The study areas are temperate coniferous forests. Trichloromethyl compounds can be found in all compartments of the forests (groundwater, soil, vegetation and throughfall), but not all compounds in all compartments. The atmospheric input of trichloromethyl compounds is found to be minor, with significant contributions for trichloroacetic acid (TCAA), only. In top soil, where the formation of the compounds is expected to occur, there is a clear positive relationship between chloroform and trichloroacetyl containing compounds. Other positive relations occur, which in combination with chlorination experiments performed in the laboratory, point to the fact that all the trichloromethyl compounds may be formed concurrently in the soil, and their subsequent fates then differ due to different physical, chemical and biological properties. TCAA cannot be detected in soil and groundwater, but sorption and mineralization experiments performed in the laboratory in combination with analyses of vegetation, show that TCAA is probably formed in the top soil and then partly taken up by the vegetation and partly mineralized in the soil. Based on this and previous studies, a conceptual model for the natural cycling of trichloromethyl compounds in forests is proposed.
Trichloroacetic acid (TCAA) is a pollutant with several sources and is also formed naturally in s... more Trichloroacetic acid (TCAA) is a pollutant with several sources and is also formed naturally in soil. We show that almost all investigated environmental compartments (soil, soil water, groundwater, spruce needles and throughfall, but not rain) contain compounds, which make false positives in the thermal decarboxylation method often used for determination of TCAA in environmental samples. The compounds are dominating quantitatively over TCAA in soil, soil water and groundwater, while TCAA is dominating in needle and throughfall samples. The compounds behave differently from TCAA with regard to the velocity and the pH-dependence of the chloroform release. We did not manage to reveal the whole chemical structure of the compounds, but a trichloroacetyl group seems to be the only plausible structure giving rise to CHCl(3) both upon heating and under alkaline conditions. Besides the trichloroacetyl group, the compounds did in general contain a carboxylic acid group, although in needle and throughfall samples, trichloroacetyl compounds with a neutral charge at pH 7.5 seemed to co-exist with the carboxylic acids. Trichloroacetyl groups in humic substances and possibly other macromolecular structures contribute to the major portion of the total trichloroacetyl-CHCl(3) in topsoil, but smaller molecules with less UV-VIS absorption seem to constitute the major part of trichloroacetyl-CHCl(3) in soil water and groundwater. The trichloroacetyl containing compounds are most likely naturally occurring compounds formed in the natural chlorination processes in soil, but additional studies are needed to substantiate this hypothesis.
A leaching experiment, where liquid manure spiked with Salmonella enterica serovar Typhimurium (T... more A leaching experiment, where liquid manure spiked with Salmonella enterica serovar Typhimurium (Tet + ) DSM554 was applied to soil surfaces, was conducted on intact soil monoliths (60 cm in diameter and 100 cm long). A total of 6.5 × 10 10 CFU was applied to each column. We found that Salmonella serovar Typhimurium could be transported to a 1-m depth in loamy soil at concentrations reaching 1.3 × 10 5 CFU/ml of leachate. The test strain was found in concentrations ranging from 300 to 1.3 5 cells/ml in loamy soil throughout the 27 days of the experiment, while concentrations below 20 cells/ml were sporadically detected in the leachates from sandy monoliths. Real-time PCR targeting invA DNA showed a clear correspondence between the total and culturable numbers of cells in the leachate, indicating that most cells leached were viable. On day 28, distribution of Salmonella serovar Typhimurium at five depths in the four monoliths was determined. The highest recovery rate, ranging from 1.5...
The aim of our study was to estimate emissions of natural chloroform from soil in arctic and suba... more The aim of our study was to estimate emissions of natural chloroform from soil in arctic and subarctic ecosystems. We therefore determined the seasonal and spatial variation in soil-to-air fluxes of chloroform at 11 sites representing typical vegetation types in Greenland (Narsarsuaq, Kangerlussuaq and Disko Island) and northern Scandinavia (Abisko). Fluxes of chloroform showed a large variation, ranging from 4 to 2850 ng m−2 h−1. The local variation within a 12-m transect at each site was frequently five to tenfold, which emphasizes the need for multiple measurements even within field plots that seem homogenous. At one site, the transect was extended to 58 m and 40 measurements and a large number of environmental parameters were recorded as well. In this transect, collars separated by 60 cm distances were in most cases similar but at 3 m distance variation was as big as between collars with greater separation. CO2 flux was the parameter that showed the most correlation to the chloroform flux in the extended transect. Chloroform fluxes also varied over the year, but this variation was smaller than the variation between the five collars of each site and much smaller than the variation between sites. All arctic sites except a non-tussock sedge wetland showed low fluxes. A subarctic pine forest had by far the highest fluxes. Subarctic and boreal coniferous forests generally seem to be important global sources of biogenic chloroform to the troposphere. The future spatial extent of coniferous forest in the subarctic to arctic region, in response to climate change, may be the key driver of future chloroform emissions from these areas.
Pollution with organochlorines has received major attention due to various environmental effects,... more Pollution with organochlorines has received major attention due to various environmental effects, but it is now increasingly recognized, that they also take part in biogeochemical cycles and that natural background concentrations exist for several chlorinated compounds. We here report the natural occurrence and cycling of organic compounds with a trichloromethyl moiety in common. The study areas are temperate coniferous forests. Trichloromethyl compounds can be found in all compartments of the forests (groundwater, soil, vegetation and throughfall), but not all compounds in all compartments. The atmospheric input of trichloromethyl compounds is found to be minor, with significant contributions for trichloroacetic acid (TCAA), only. In top soil, where the formation of the compounds is expected to occur, there is a clear positive relationship between chloroform and trichloroacetyl containing compounds. Other positive relations occur, which in combination with chlorination experiments performed in the laboratory, point to the fact that all the trichloromethyl compounds may be formed concurrently in the soil, and their subsequent fates then differ due to different physical, chemical and biological properties. TCAA cannot be detected in soil and groundwater, but sorption and mineralization experiments performed in the laboratory in combination with analyses of vegetation, show that TCAA is probably formed in the top soil and then partly taken up by the vegetation and partly mineralized in the soil. Based on this and previous studies, a conceptual model for the natural cycling of trichloromethyl compounds in forests is proposed.
Trichloroacetic acid (TCAA) is a pollutant with several sources and is also formed naturally in s... more Trichloroacetic acid (TCAA) is a pollutant with several sources and is also formed naturally in soil. We show that almost all investigated environmental compartments (soil, soil water, groundwater, spruce needles and throughfall, but not rain) contain compounds, which make false positives in the thermal decarboxylation method often used for determination of TCAA in environmental samples. The compounds are dominating quantitatively over TCAA in soil, soil water and groundwater, while TCAA is dominating in needle and throughfall samples. The compounds behave differently from TCAA with regard to the velocity and the pH-dependence of the chloroform release. We did not manage to reveal the whole chemical structure of the compounds, but a trichloroacetyl group seems to be the only plausible structure giving rise to CHCl(3) both upon heating and under alkaline conditions. Besides the trichloroacetyl group, the compounds did in general contain a carboxylic acid group, although in needle and throughfall samples, trichloroacetyl compounds with a neutral charge at pH 7.5 seemed to co-exist with the carboxylic acids. Trichloroacetyl groups in humic substances and possibly other macromolecular structures contribute to the major portion of the total trichloroacetyl-CHCl(3) in topsoil, but smaller molecules with less UV-VIS absorption seem to constitute the major part of trichloroacetyl-CHCl(3) in soil water and groundwater. The trichloroacetyl containing compounds are most likely naturally occurring compounds formed in the natural chlorination processes in soil, but additional studies are needed to substantiate this hypothesis.
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Papers by Ole Stig Jacobsen