Ruth Blake - Academia.edu (original) (raw)

Papers by Ruth Blake

Interest in the interactions between microorganisms and mineral surfaces has greatly intensified ... more Interest in the interactions between microorganisms and mineral surfaces has greatly intensified in recent years. Although many studies have appeared showing highresolution images of bacteria and other microorganisms in association with mineral surfaces using optical, electron, confocal, atomic force and other microscopic techniques, few

Fifty-seven interstitial water samples from six sites (Ocean Drilling Program Sites 1225-1229 and... more Fifty-seven interstitial water samples from six sites (Ocean Drilling Program Sites 1225-1229 and 1231) in the eastern equatorial Pacific Ocean and the Peru margin were analyzed for the stable sulfur isotopic composition (34S/32S) of dissolved sulfate along with major and minor ions. With the exception of Site 1231, sulfate from the interstitial fluids (d34S values as much as 89 per mil vs. the SF6-based Vienna-Canyon Diablo troilite standard) is found at depth to be enriched in 34S with respect to modern seawater sulfate (d34S = ~21 per mil), indicating that microbial sulfate reduction (MSR) took place to different extents at all investigated sites. Deeper sediments at Sites 1228 and 1229 are additionally influenced by diffusion of a sulfate-rich brine that has already undergone sulfate reduction. The intensity of MSR depends on the availability of substrate (organic matter), sedimentation conditions, and the active bacterial community structure. Formation of isotopically heavy diagenetic barite at the sulfate-methane transition zone is expected at Sites 1227 (one front), 1229 (two fronts), and probably Site 1228. At Site 1231, the constant sulfur isotopic composition of sulfate and concentrations of minor pore water ions indicate that suboxic (essentially iron and manganese oxide based) diagenesis dominates and no net MSR occurs.

Chemical Geology, Sep 1, 2010

We present oxygen isotope, micro-textural, and molecular evidence of microbial activity in the fo... more We present oxygen isotope, micro-textural, and molecular evidence of microbial activity in the formation of hydroxylapatite (HAP) in three limestone caves (Gosu, Sungryu, and Ssang caves) in South Korea. HAP typically forms as crusts (0.1 to 0.5 mm thick) coating carbonates of speleothems and host rock surfaces, on and near bat habitats. Micro-textures within HAP crusts indicate that a metastable apatite precursor (AP) is initially precipitated on and near the surfaces of sulfur-bearing microbial filaments and then transforms to HAP. Analysis of DNA extracted from the HAP crusts confirms that sulfur-oxidizing bacteria are present in some of the HAP samples. The δ 18 O values of phosphate (δ 18 O P) in HAP precipitated in the caves range from 14.6 to 15.6‰ and are close to isotopic equilibrium with the weighted mean annual δ 18 O value of rain water (= cave water) at the mean annual air temperature (= measured cave temperature). The difference in oxygen isotopic composition between speleothem carbonate (δ 18 O C) and phosphate (δ 18 O P) in adjacent apatitic crusts is similar to that of co-existing carbonate and phosphate in modern biogenic apatite. These results suggest that phosphate, likely derived from bat excretions, was metabolized by microorganisms and has undergone extensive oxygen isotope exchange with cave drip water by intense biological turnover of phosphate, and then precipitated as HAP in near-equilibrium with water and carbonate in the cave ecosystem. Results from these studies of δ 18 O P values of HAP crusts in limestone caves demonstrate the utility of δ 18 O P as an environmental temperature proxy and signature of microbiological processes.

Oxygen (O) isotope ratios of biogenic apatites have been widely used as paleotemperature and envi... more Oxygen (O) isotope ratios of biogenic apatites have been widely used as paleotemperature and environmental geochemical proxies. With improved knowledge of the phosphate O isotope effects of different P cycling pathways, the delta18O value of inorganic phosphate (delta18OP) has been proposed as a useful proxy and tracer of biological reactions and P cycling in natural environments[1,2,3,4]. Being the only way

RSC Advances, 2019

Methylphosphonic acid (MPn) is an intermediate in the synthesis of the phosphorus-containing nerv... more Methylphosphonic acid (MPn) is an intermediate in the synthesis of the phosphorus-containing nerve agents, such as sarin and VX, and a biosynthesis product of marine microbes with ramifications to global climate change and eutrophication.

Sulfur Biogeochemistry - Past and Present, 2004

Page 171. Geological Society of America Special Paper 379 2004 Sites of anomalous organic reminer... more Page 171. Geological Society of America Special Paper 379 2004 Sites of anomalous organic remineralization in the carbonate sediments of South Florida, USA: The sulfur cycle and carbonate-associated sulfate Timothy W ...

Rapid Communications in Mass Spectrometry, 2012

Past stable isotopic studies of selenium and arsenic oxyanions within a biogeochemistry context h... more Past stable isotopic studies of selenium and arsenic oxyanions within a biogeochemistry context have focused solely on selenium isotopes due to monoisotopic nature of arsenic and lack of attention to oxygen. A modern quantification method of d 18 O values in selenate, selenite, arsenate, and arsenite is presented here, similar to methods for other inorganic oxyanions such as phosphate. METHODS: Dissolved oxyanions were recovered after precipitation with silver or barium cations within controlled pH ranges and purified by drying and roasting under vacuum. Oxygen isotope ratio measurements were performed on 250-450 micrograms of solids using continuous flow high-temperature conversion elemental analyzer/isotope ratio mass spectrometry (CF-TCEA/IRMS). Each Se and As solid was evaluated for reproducibility and stability of d 18 O values and the usefulness of this method for evaluating aqueous phase Se and As oxyanion reactions was addressed. RESULTS: Only silver arsenate and barium selenate were shown to have stable, reproducible d 18 O values over 5 months and were calibrated to the VSMOW scale. The method was applied to confirm complete exchange of oxygen isotopes between arsenate and solvent water at pH 7 which produced an O-isotope fractionation between arsenate and water of 6.0%. Furthermore, the method revealed the ability of oxygen in selenate to kinetically fractionate during reduction to elemental selenium by a green rust compound which produced a fractionation (20.9%) larger than reported d 80/76 Se values for similar reactions. CONCLUSIONS: The experimental and analytical conditions for d 18 O analysis of Se and As oxyanions were detailed. d 18 O analyses of As and Se oxyanions may be useful in biogeochemical studies for tracing chemical reaction pathways, determining environmental sources of Se, or diagnosing specific reaction mechanisms for As and Se oxyanions.

AGU Spring Meeting …, 2006

On earth, phosphate has a strong biological oxygen isotope signature due to its concentration and... more On earth, phosphate has a strong biological oxygen isotope signature due to its concentration and intense cycling by living organisms as an essential nutrient. Phosphate does not undergo oxygen isotope exchange with water at low temperature without ...

The Terrestrial Fractionation Line (TFL) for oxygen isotopes is defined by 17O/16O and 18O/16O an... more The Terrestrial Fractionation Line (TFL) for oxygen isotopes is defined by 17O/16O and 18O/16O analyses of meteoric waters, seawater, sedimentary, metamorphic, and igneous rocks and constituent minerals. Interlaboratory measurements of the slope of the TFL on a plot of d18O vs. d17O revealed eclogitic garnets with a slope of 0.526 and hydrothermal quartz of 0.524 from rocks younger than 0.8

ABSTRACT Increased production and use of carbon nanotubes (CNTs) may result in the introduction o... more ABSTRACT Increased production and use of carbon nanotubes (CNTs) may result in the introduction of CNTs to soils and ultimately into groundwater systems. Deposition of CNTs onto surfaces is key to their fate, bioavailability, and reactivity in aquatic systems. This study evaluates the transport and deposition behavior of functionalized single-walled carbon nanotubes (SWNTs) in a well-defined porous media comprising quartz sand. Our results show that increasing solution ionic strength results in increased SWNT deposition (filtration). This observation is consistent with conventional colloidal stability theories, thereby suggesting that physicochemical filtration plays an important role in SWNT transport. However, the relatively insignificant change of SWNT filtration at low ionic strengths (≤3.0 mM KCl) and the incomplete breakthrough of SWNTs in deionized water indicate that physical straining also plays an important role in the capture of SWNTs within the packed sand bed. It is proposed that SWNT shape and structure, particularly the very large aspect ratio and highly bundled (aggregated) state in aqueous solutions, contribute considerably to straining in flow through porous media. We conclude that both physicochemical filtration and straining play a role at low ionic strength (<3.0 mM), while physicochemical filtration is the dominant mechanism of SWNT filtration at higher ionic strengths.

Geochimica et Cosmochimica Acta, 2015

The stable oxygen isotope composition of orthophosphate (d 18 O PO4) is a widely used (paleo)temp... more The stable oxygen isotope composition of orthophosphate (d 18 O PO4) is a widely used (paleo)temperature indicator and more recently, a useful tracer of phosphorus-cycling. In natural aqueous systems (e.g., oceans, rivers, soil/ground water) the largest reactive phosphorus pool is dissolved inorganic phosphate. Here, we present a new experimentally-determined equation for thermodynamic equilibrium O-isotope fractionations between dissolved phosphate and water, catalyzed by the enzyme inorganic pyrophosphatase (PPase) between 3 and 37°C; 1000 ln a ðPO 4 ÀH 2 OÞ ¼ 14:43 ðAE0:39Þ 1000=T ðKÞ À 26:54 ðAE1:33Þ r 2 ¼ 0:99 The new equation is slightly offset by +0.5 to +0.7& from recent empirically-determined fractionations based on biogenic apatite, with both based on modern cf-irms TC/EA analysis of Ag 3 PO 4. Dissolved phosphate-water fractionations are offset by +0.9 to +2.3& from the earlier empirical relation for biogenic phosphate-water fractionation determined using fluorination of BiPO 4. The equation presented here is thus, specific to equilibrium fractions between dissolved phosphate and water and appropriate for use in recent/future oxygen isotope studies of dissolved phosphate using similar cf-irms TC/EA analytical methods.

Interest in the interactions between microorganisms and mineral surfaces has greatly intensified ... more Interest in the interactions between microorganisms and mineral surfaces has greatly intensified in recent years. Although many studies have appeared showing highresolution images of bacteria and other microorganisms in association with mineral surfaces using optical, electron, confocal, atomic force and other microscopic techniques, few

Fifty-seven interstitial water samples from six sites (Ocean Drilling Program Sites 1225-1229 and... more Fifty-seven interstitial water samples from six sites (Ocean Drilling Program Sites 1225-1229 and 1231) in the eastern equatorial Pacific Ocean and the Peru margin were analyzed for the stable sulfur isotopic composition (34S/32S) of dissolved sulfate along with major and minor ions. With the exception of Site 1231, sulfate from the interstitial fluids (d34S values as much as 89 per mil vs. the SF6-based Vienna-Canyon Diablo troilite standard) is found at depth to be enriched in 34S with respect to modern seawater sulfate (d34S = ~21 per mil), indicating that microbial sulfate reduction (MSR) took place to different extents at all investigated sites. Deeper sediments at Sites 1228 and 1229 are additionally influenced by diffusion of a sulfate-rich brine that has already undergone sulfate reduction. The intensity of MSR depends on the availability of substrate (organic matter), sedimentation conditions, and the active bacterial community structure. Formation of isotopically heavy diagenetic barite at the sulfate-methane transition zone is expected at Sites 1227 (one front), 1229 (two fronts), and probably Site 1228. At Site 1231, the constant sulfur isotopic composition of sulfate and concentrations of minor pore water ions indicate that suboxic (essentially iron and manganese oxide based) diagenesis dominates and no net MSR occurs.

Chemical Geology, Sep 1, 2010

We present oxygen isotope, micro-textural, and molecular evidence of microbial activity in the fo... more We present oxygen isotope, micro-textural, and molecular evidence of microbial activity in the formation of hydroxylapatite (HAP) in three limestone caves (Gosu, Sungryu, and Ssang caves) in South Korea. HAP typically forms as crusts (0.1 to 0.5 mm thick) coating carbonates of speleothems and host rock surfaces, on and near bat habitats. Micro-textures within HAP crusts indicate that a metastable apatite precursor (AP) is initially precipitated on and near the surfaces of sulfur-bearing microbial filaments and then transforms to HAP. Analysis of DNA extracted from the HAP crusts confirms that sulfur-oxidizing bacteria are present in some of the HAP samples. The δ 18 O values of phosphate (δ 18 O P) in HAP precipitated in the caves range from 14.6 to 15.6‰ and are close to isotopic equilibrium with the weighted mean annual δ 18 O value of rain water (= cave water) at the mean annual air temperature (= measured cave temperature). The difference in oxygen isotopic composition between speleothem carbonate (δ 18 O C) and phosphate (δ 18 O P) in adjacent apatitic crusts is similar to that of co-existing carbonate and phosphate in modern biogenic apatite. These results suggest that phosphate, likely derived from bat excretions, was metabolized by microorganisms and has undergone extensive oxygen isotope exchange with cave drip water by intense biological turnover of phosphate, and then precipitated as HAP in near-equilibrium with water and carbonate in the cave ecosystem. Results from these studies of δ 18 O P values of HAP crusts in limestone caves demonstrate the utility of δ 18 O P as an environmental temperature proxy and signature of microbiological processes.

Oxygen (O) isotope ratios of biogenic apatites have been widely used as paleotemperature and envi... more Oxygen (O) isotope ratios of biogenic apatites have been widely used as paleotemperature and environmental geochemical proxies. With improved knowledge of the phosphate O isotope effects of different P cycling pathways, the delta18O value of inorganic phosphate (delta18OP) has been proposed as a useful proxy and tracer of biological reactions and P cycling in natural environments[1,2,3,4]. Being the only way

RSC Advances, 2019

Methylphosphonic acid (MPn) is an intermediate in the synthesis of the phosphorus-containing nerv... more Methylphosphonic acid (MPn) is an intermediate in the synthesis of the phosphorus-containing nerve agents, such as sarin and VX, and a biosynthesis product of marine microbes with ramifications to global climate change and eutrophication.

Sulfur Biogeochemistry - Past and Present, 2004

Page 171. Geological Society of America Special Paper 379 2004 Sites of anomalous organic reminer... more Page 171. Geological Society of America Special Paper 379 2004 Sites of anomalous organic remineralization in the carbonate sediments of South Florida, USA: The sulfur cycle and carbonate-associated sulfate Timothy W ...

Rapid Communications in Mass Spectrometry, 2012

Past stable isotopic studies of selenium and arsenic oxyanions within a biogeochemistry context h... more Past stable isotopic studies of selenium and arsenic oxyanions within a biogeochemistry context have focused solely on selenium isotopes due to monoisotopic nature of arsenic and lack of attention to oxygen. A modern quantification method of d 18 O values in selenate, selenite, arsenate, and arsenite is presented here, similar to methods for other inorganic oxyanions such as phosphate. METHODS: Dissolved oxyanions were recovered after precipitation with silver or barium cations within controlled pH ranges and purified by drying and roasting under vacuum. Oxygen isotope ratio measurements were performed on 250-450 micrograms of solids using continuous flow high-temperature conversion elemental analyzer/isotope ratio mass spectrometry (CF-TCEA/IRMS). Each Se and As solid was evaluated for reproducibility and stability of d 18 O values and the usefulness of this method for evaluating aqueous phase Se and As oxyanion reactions was addressed. RESULTS: Only silver arsenate and barium selenate were shown to have stable, reproducible d 18 O values over 5 months and were calibrated to the VSMOW scale. The method was applied to confirm complete exchange of oxygen isotopes between arsenate and solvent water at pH 7 which produced an O-isotope fractionation between arsenate and water of 6.0%. Furthermore, the method revealed the ability of oxygen in selenate to kinetically fractionate during reduction to elemental selenium by a green rust compound which produced a fractionation (20.9%) larger than reported d 80/76 Se values for similar reactions. CONCLUSIONS: The experimental and analytical conditions for d 18 O analysis of Se and As oxyanions were detailed. d 18 O analyses of As and Se oxyanions may be useful in biogeochemical studies for tracing chemical reaction pathways, determining environmental sources of Se, or diagnosing specific reaction mechanisms for As and Se oxyanions.

AGU Spring Meeting …, 2006

On earth, phosphate has a strong biological oxygen isotope signature due to its concentration and... more On earth, phosphate has a strong biological oxygen isotope signature due to its concentration and intense cycling by living organisms as an essential nutrient. Phosphate does not undergo oxygen isotope exchange with water at low temperature without ...

The Terrestrial Fractionation Line (TFL) for oxygen isotopes is defined by 17O/16O and 18O/16O an... more The Terrestrial Fractionation Line (TFL) for oxygen isotopes is defined by 17O/16O and 18O/16O analyses of meteoric waters, seawater, sedimentary, metamorphic, and igneous rocks and constituent minerals. Interlaboratory measurements of the slope of the TFL on a plot of d18O vs. d17O revealed eclogitic garnets with a slope of 0.526 and hydrothermal quartz of 0.524 from rocks younger than 0.8

ABSTRACT Increased production and use of carbon nanotubes (CNTs) may result in the introduction o... more ABSTRACT Increased production and use of carbon nanotubes (CNTs) may result in the introduction of CNTs to soils and ultimately into groundwater systems. Deposition of CNTs onto surfaces is key to their fate, bioavailability, and reactivity in aquatic systems. This study evaluates the transport and deposition behavior of functionalized single-walled carbon nanotubes (SWNTs) in a well-defined porous media comprising quartz sand. Our results show that increasing solution ionic strength results in increased SWNT deposition (filtration). This observation is consistent with conventional colloidal stability theories, thereby suggesting that physicochemical filtration plays an important role in SWNT transport. However, the relatively insignificant change of SWNT filtration at low ionic strengths (≤3.0 mM KCl) and the incomplete breakthrough of SWNTs in deionized water indicate that physical straining also plays an important role in the capture of SWNTs within the packed sand bed. It is proposed that SWNT shape and structure, particularly the very large aspect ratio and highly bundled (aggregated) state in aqueous solutions, contribute considerably to straining in flow through porous media. We conclude that both physicochemical filtration and straining play a role at low ionic strength (<3.0 mM), while physicochemical filtration is the dominant mechanism of SWNT filtration at higher ionic strengths.

Geochimica et Cosmochimica Acta, 2015

The stable oxygen isotope composition of orthophosphate (d 18 O PO4) is a widely used (paleo)temp... more The stable oxygen isotope composition of orthophosphate (d 18 O PO4) is a widely used (paleo)temperature indicator and more recently, a useful tracer of phosphorus-cycling. In natural aqueous systems (e.g., oceans, rivers, soil/ground water) the largest reactive phosphorus pool is dissolved inorganic phosphate. Here, we present a new experimentally-determined equation for thermodynamic equilibrium O-isotope fractionations between dissolved phosphate and water, catalyzed by the enzyme inorganic pyrophosphatase (PPase) between 3 and 37°C; 1000 ln a ðPO 4 ÀH 2 OÞ ¼ 14:43 ðAE0:39Þ 1000=T ðKÞ À 26:54 ðAE1:33Þ r 2 ¼ 0:99 The new equation is slightly offset by +0.5 to +0.7& from recent empirically-determined fractionations based on biogenic apatite, with both based on modern cf-irms TC/EA analysis of Ag 3 PO 4. Dissolved phosphate-water fractionations are offset by +0.9 to +2.3& from the earlier empirical relation for biogenic phosphate-water fractionation determined using fluorination of BiPO 4. The equation presented here is thus, specific to equilibrium fractions between dissolved phosphate and water and appropriate for use in recent/future oxygen isotope studies of dissolved phosphate using similar cf-irms TC/EA analytical methods.