Rates of methane emission from intact cores were measured during anoxic dark and oxic light and d... more Rates of methane emission from intact cores were measured during anoxic dark and oxic light and dark incubations. Rates of methane oxidation were calculated on the basis of oxic incubations by using the anoxic emissions as an estimate of the maximum potential flux. This technique indicated that methane oxidation consumed up to 91% of the maximum potential flux in peat sediments but that oxidation was negligible in marl sediments. Oxygen microprofiles determined for intact cores were comparable to profiles measured in situ. Thus, the laboratory incubations appeared to provide a reasonable approximation of in situ activities. This was further supported by the agreement between measured methane fluxes and fluxes predicted on the basis of methane profiles determined by in situ sampling of pore water. Methane emissions from peat sediments, oxygen concentrations and penetration depths, and methane concentration profiles were all sensitive to light-dark shifts as determined by a combinatio...
Strong inhibitory effects of the anionic surfactant linear alkylbenzene sulfonate (LAS) on four s... more Strong inhibitory effects of the anionic surfactant linear alkylbenzene sulfonate (LAS) on four strains of autotrophic ammonia-oxidizing bacteria (AOB) are reported. Two Nitrosospira strains were considerably more sensitive to LAS than two Nitrosomonas strains were. Interestingly, the two Nitrosospira strains showed a weak capacity to remove LAS from the medium. This could not be attributed to adsorption or any other known physical or chemical process, suggesting that biodegradation of LAS took place. In each strain, the metabolic activity (50% effective concentration [EC 50 ], 6 to 38 mg liter −1 ) was affected much less by LAS than the growth rate and viability (EC 50 , 3 to 14 mg liter −1 ) were. However, at LAS levels that inhibited growth, metabolic activity took place only for 1 to 5 days, after which metabolic activity also ceased. The potential for adaptation to LAS exposure was investigated with Nitrosomonas europaea grown at a sublethal LAS level (10 mg liter −1 ); compare...
A new microarray method, the isotope array approach, for identifying microorganisms which consume... more A new microarray method, the isotope array approach, for identifying microorganisms which consume a 14 C-labeled substrate within complex microbial communities was developed. Experiments were performed with a small microarray consisting of oligonucleotide probes targeting the 16S rRNA of ammonia-oxidizing bacteria (AOB). Total RNA was extracted from a pure culture of Nitrosomonas eutropha grown in the presence of [ 14 C]bicarbonate. After fluorescence labeling of the RNA and microarray hybridization, scanning of all probe spots for fluorescence and radioactivity revealed that specific signals were obtained and that the incorporation of 14 C into rRNA could be detected unambiguously. Subsequently, we were able to demonstrate the suitability of the isotope array approach for monitoring community composition and CO 2 fixation activity of AOB in two nitrifying activated-sludge samples which were incubated with [ 14 C]bicarbonate for up to 26 h. AOB community structure in the activated-s...
The active herbicide ingredient glyphosate [N-(phosphonomethyl)glycine] is frequently detected as... more The active herbicide ingredient glyphosate [N-(phosphonomethyl)glycine] is frequently detected as a contaminant in groundwater and surface waters. This study investigated effects of UV-A (365 nm), UV-B (302 nm) and UV-C (254 nm) irradiation of glyphosate in water on photolysis and toxicity to aquatic organisms from different trophic levels. A test battery with bacteria (Bacillus subtilis, Aliivibrio fischeri), a green microalga (Raphidocelis subcapitata), and a crustacean (Daphnia magna) was used to assess biological effect of glyphosate and bioactive transformation products before and after UV irradiation (4.7–70 J/cm2). UV-C irradiation at 20 J/cm2 resulted in a 2–23-fold decrease in toxicity of glyphosate to aquatic test organisms. UV-B irradiation at 70 J/cm2 caused a twofold decrease whereas UV-A did not affect glyphosate toxicity at doses ≤ 70 J/cm2. UV-C irradiation of glyphosate in drinking water and groundwater with naturally occurring organic and inorganic constituents sho...
Manganese removal in drinking water biofilters is facilitated by biological and physico-chemical ... more Manganese removal in drinking water biofilters is facilitated by biological and physico-chemical processes, but knowledge regarding the relative role of these mechanisms during start-up is very limited. The aim of this study was to identify the dominant process for manganese removal occurring during the start-up period of sand filters with and without inoculation by addition of matured sand collected from an operating groundwater-based waterworks. Inoculation with matured filter sand is frequently used to accelerate the start-up in virgin biofilters and to rapidly obtain compliant water quality. The non-inoculated filter took 41 days to comply with manganese quality criteria, whereas the inoculated filter with 20% matured sand showed removal from Day 1 and compliance from Day 25. By Day 48, the inoculated filter showed two times higher manganese removal rates and manganese oxides deposits. Using sodium azide as an inhibitor of microbial activity, it was found that manganese removal ...
Rates of methane emission from intact cores were measured during anoxic dark and oxic light and d... more Rates of methane emission from intact cores were measured during anoxic dark and oxic light and dark incubations. Rates of methane oxidation were calculated on the basis of oxic incubations by using the anoxic emissions as an estimate of the maximum potential flux. This technique indicated that methane oxidation consumed up to 91% of the maximum potential flux in peat sediments but that oxidation was negligible in marl sediments. Oxygen microprofiles determined for intact cores were comparable to profiles measured in situ. Thus, the laboratory incubations appeared to provide a reasonable approximation of in situ activities. This was further supported by the agreement between measured methane fluxes and fluxes predicted on the basis of methane profiles determined by in situ sampling of pore water. Methane emissions from peat sediments, oxygen concentrations and penetration depths, and methane concentration profiles were all sensitive to light-dark shifts as determined by a combinatio...
Strong inhibitory effects of the anionic surfactant linear alkylbenzene sulfonate (LAS) on four s... more Strong inhibitory effects of the anionic surfactant linear alkylbenzene sulfonate (LAS) on four strains of autotrophic ammonia-oxidizing bacteria (AOB) are reported. Two Nitrosospira strains were considerably more sensitive to LAS than two Nitrosomonas strains were. Interestingly, the two Nitrosospira strains showed a weak capacity to remove LAS from the medium. This could not be attributed to adsorption or any other known physical or chemical process, suggesting that biodegradation of LAS took place. In each strain, the metabolic activity (50% effective concentration [EC 50 ], 6 to 38 mg liter −1 ) was affected much less by LAS than the growth rate and viability (EC 50 , 3 to 14 mg liter −1 ) were. However, at LAS levels that inhibited growth, metabolic activity took place only for 1 to 5 days, after which metabolic activity also ceased. The potential for adaptation to LAS exposure was investigated with Nitrosomonas europaea grown at a sublethal LAS level (10 mg liter −1 ); compare...
A new microarray method, the isotope array approach, for identifying microorganisms which consume... more A new microarray method, the isotope array approach, for identifying microorganisms which consume a 14 C-labeled substrate within complex microbial communities was developed. Experiments were performed with a small microarray consisting of oligonucleotide probes targeting the 16S rRNA of ammonia-oxidizing bacteria (AOB). Total RNA was extracted from a pure culture of Nitrosomonas eutropha grown in the presence of [ 14 C]bicarbonate. After fluorescence labeling of the RNA and microarray hybridization, scanning of all probe spots for fluorescence and radioactivity revealed that specific signals were obtained and that the incorporation of 14 C into rRNA could be detected unambiguously. Subsequently, we were able to demonstrate the suitability of the isotope array approach for monitoring community composition and CO 2 fixation activity of AOB in two nitrifying activated-sludge samples which were incubated with [ 14 C]bicarbonate for up to 26 h. AOB community structure in the activated-s...
The active herbicide ingredient glyphosate [N-(phosphonomethyl)glycine] is frequently detected as... more The active herbicide ingredient glyphosate [N-(phosphonomethyl)glycine] is frequently detected as a contaminant in groundwater and surface waters. This study investigated effects of UV-A (365 nm), UV-B (302 nm) and UV-C (254 nm) irradiation of glyphosate in water on photolysis and toxicity to aquatic organisms from different trophic levels. A test battery with bacteria (Bacillus subtilis, Aliivibrio fischeri), a green microalga (Raphidocelis subcapitata), and a crustacean (Daphnia magna) was used to assess biological effect of glyphosate and bioactive transformation products before and after UV irradiation (4.7–70 J/cm2). UV-C irradiation at 20 J/cm2 resulted in a 2–23-fold decrease in toxicity of glyphosate to aquatic test organisms. UV-B irradiation at 70 J/cm2 caused a twofold decrease whereas UV-A did not affect glyphosate toxicity at doses ≤ 70 J/cm2. UV-C irradiation of glyphosate in drinking water and groundwater with naturally occurring organic and inorganic constituents sho...
Manganese removal in drinking water biofilters is facilitated by biological and physico-chemical ... more Manganese removal in drinking water biofilters is facilitated by biological and physico-chemical processes, but knowledge regarding the relative role of these mechanisms during start-up is very limited. The aim of this study was to identify the dominant process for manganese removal occurring during the start-up period of sand filters with and without inoculation by addition of matured sand collected from an operating groundwater-based waterworks. Inoculation with matured filter sand is frequently used to accelerate the start-up in virgin biofilters and to rapidly obtain compliant water quality. The non-inoculated filter took 41 days to comply with manganese quality criteria, whereas the inoculated filter with 20% matured sand showed removal from Day 1 and compliance from Day 25. By Day 48, the inoculated filter showed two times higher manganese removal rates and manganese oxides deposits. Using sodium azide as an inhibitor of microbial activity, it was found that manganese removal ...
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