Measurements of H202 in rainwater collected in Miami, Florida, and the Bahama Islands area indica... more Measurements of H202 in rainwater collected in Miami, Florida, and the Bahama Islands area indicate the presenc e of H202 concentration levels ranging from (1-7) x 10-5 M. No systematic trends in H202 concentration were observed during an individual storm, in marked contrast to the behavior of other anions (e.g., [NO3-], [SO4=], and [C1-]). The data suggest that a substantial fraction of the H202 found in precipitation is generated by aqueous-phase reactions within the cloudwater rather than via rainout and washout of gaseous H202.
Gas Phase and Particulate Phase Organic Compositions at the Sydney Site During the 2002 Bay Regional Atmospheric Chemistry Experiment (BRACE)
AGU Fall Meeting Abstracts, Dec 1, 2003
During the Bay Regional Atmospheric Chemistry Experiment (BRACE) in 2002, particle and gas phase ... more During the Bay Regional Atmospheric Chemistry Experiment (BRACE) in 2002, particle and gas phase organic compounds were routinely measured at the Sydney site east of Tampa. This was the most easterly (inland) site occupied during the study and could be characterized as a rural clean air site which provided the background site for the Tampa urban area. Aircraft measurements were also performed using canisters to follow the urban air plume. Because of the proximity of Tampa and the transport of the urban air mass eastward, periodic enrichment episodes where anticipated. Hourly measurements of C2-C12 NMHCs were performed using a system composed of a gas trap coupled with a GC/FID. Aerosol samples were also collected for organic speciation. PM2.5 and size-segregated samples were respectively collected with a high volume sampler and Micro Orifice Uniform Deposit Impactors (MOUDIs). All particulate matter (PM) samples were collected on a 24 hours schedule with the exception of a few days while shorter schedules were used for the PM2.5. Samples were extracted using a mixture of dichloromethane/acetone/hexane, concentrated down and analyzed using gas chromatography-mass spectrometry (GC/MS). Gas phase results showed that isoprene was consistently the most common NMHC present and constituted the bulk of the OH reactivity. The measurements will be put into the context of other continental background measurements. Linkages to organic aerosol formation will also be explored. Organic speciation of PM showed that the Sydney site was representative of a rural site for most of May 2002. Concentrations, especially for polycyclic aromatic hydrocarbons (PAH), compared well with PM2.5 data obtained from other rural sites within the Southeastern United States. Only a few days showed concentrations higher than typical rural sites but without reaching urban values.
Correlation of UV-vis absorption and solar irradiance with depth in seawater
Annual Meeting Optical Society of America, 1989
Photochemical and optical properties of seawater are controlled by the absorbance spectrum of the... more Photochemical and optical properties of seawater are controlled by the absorbance spectrum of the chromophores and by the light intensity and spectral distribution at depth. These parameters are not commonly measured together. Solar penetration has previously been estimated from short-and long-wavelength insulation formulas or has been modeled from multiple wavelength attenuation formulas. On two cruises in the Caribbean Sea in the spring and fall of 1988, irradiance data were collected at selected depths in the photic zone and concurrently at the surface, using LICOR spectroradiometers. Absorbance measurements by a spectrophotometer were made on water collected by CTD casts within a few hours of the light profiles. Particulate scattering was determined by absorption measurements on filtered (0.45-µm) and unfiltered water samples.
Publisher Summary This chapter defines some of the possible photochemical processes that may be a... more Publisher Summary This chapter defines some of the possible photochemical processes that may be affecting the nature of organic materials found in seawater, and reviews some evidence for the occurrence of these processes in the marine environment. The efficiency of any photophysical or photochemical process is a function of both the properties of the reaction environment and the character of the excited state species. The fundamental quantity which is used to describe the efficiency of any photoprocess is the quantum yield ( ϕ ); it is useful in both quantifying the process and in elucidating the reaction mechanism. Quantum yield has the general definition of the number of events occumng divided by the number of photons absorbed. The understanding of marine photochemical processes and their effects on the organic fraction is still only rudimentary. The slow development of this potentially important area of marine chemistry is probably the result of a combination of factors including misconceptions about energy requirements for photochemical reactions and the depth of penetration of actinic radiation into seawater. An examination of the light absorbers in seawater reveals that many potential reactions are possible in the marine environment, and initial investigations have demonstrated that significant reactions are occurring there.
Reaction products from the chlorination of seawater. Final report 15 Jul 75-14 Jul 80
Chemical treatment of natural waters, in particular the use of chlorine as a biocide, modifies th... more Chemical treatment of natural waters, in particular the use of chlorine as a biocide, modifies the chemistry of these waters in ways that are not fully understood. The research described in this report examined both inorganic and organic reaction products from the chlorination of seawater using a variety of analytical approaches. Some analytical methods in widespread current use underestimate the
Bromoform Formation in Ozonated Groundwater Containing Bromide and Humic Substances
Ozone: Science & Engineering, 1986
... William J. Cooper1, Gary L. Amy2, Cynthia A. Moore3, and Rod G. Zilca3 1 Drinking Water Resea... more ... William J. Cooper1, Gary L. Amy2, Cynthia A. Moore3, and Rod G. Zilca3 1 Drinking Water Research Center, Florida International University ... wells situated next to the Alexander Orr water treatment plant, the Hollywood water treatment plant, the John Preston water treatment ...
Total optical attenuation in seawater is defined by the following equation (Jerlov, 1968): C tot ... more Total optical attenuation in seawater is defined by the following equation (Jerlov, 1968): C tot = ap + aDOM + bp + cw where ap = absorption coefficient for particles, aDOM is the absorption coefficient for the dissolved organic matter, bp is the scattering by particles, and cw is the attenuation by water (through absorption, and elastic and inelastic scattering). For coastal waters it is the first three terms of this equation that are responsible for the large range in optical attenuation and variation in color that are often observed. Also, these terms are interactive through a variety of processes involving transformations between the biota, DOM, and particulates. The processes affecting these transformations in coastal environments can be complex and dynamic; they include, but are not limited to recycling, sediment resuspension, precipitation, photochemical alteration, tidal flow and other physical transport and mixing processes.
Report Group 3 – Photochemistry in the sea-surface microlayer
The Sea Surface and Global Change
... The primary reactions of these halogen species should be oxidation of organic substrates, but... more ... The primary reactions of these halogen species should be oxidation of organic substrates, but substitution reactions of aromatic and unsatu-rated ... In Active Oxygen in Chemistry, ed. CS Foote etal., pp. ... Surface microlayer phenolic enrichments indicate sea surface slicks. ...
The emphasis in our ONR funded research is placed on characterizing the factors affecting the opt... more The emphasis in our ONR funded research is placed on characterizing the factors affecting the optical properties (i.e. attenuation and fluorescence) of coastal seawater. Particular emphasis is being placed on developing a better understanding of the differences and similarities between colored dissolved organic matter CDOM of marine and terrestrial origin, and the impact these properties have on the chemical and optical characteristics of coastal environments where their effects are most pronounced. The equipment assembled under this grant is being used both in the laboratory and in shipboard experiments to provide detailed characterization of the optical properties of coastal seawater. Such information once acquired can be applied to remote sensing modeling applications and the design of optical sensing detectors for probing the ocean.
AbUnct-Emission rates of tbc bio@c sulpbur pwr hydrogen sulpbidc, dimetbyl sulpbide, carbon disul... more AbUnct-Emission rates of tbc bio@c sulpbur pwr hydrogen sulpbidc, dimetbyl sulpbide, carbon disulpbidc and dimetbyl dirulpbide lmvc bcco maaurui from the cxposui soils of five wetland planet communitks in Florida Dimctbyl &bide and hydrogen rulpbide ven tbc predominant specks emitted. All tbc studied ozosystana 8bored did variation in the cmisaion rata of the biogcnic sulpbur gases with tbe bigbat emissions rata nccu&g early-to mid-afternoon, and tbc lowest cmiasion rates occuning during the arly mornin& The rcl8tivc magnitude of anissions from the individual ccosystcmfi followed the trend DidchIt spicata > Aaknda gemhans > Bath maritima a JVKW romvianus a Clodium jfmuaicense. only the a&ion rates from the paty D. spic~ro site uc comparable in magnitude lo previous emission measuremart in wetl8nd ocorynan~ of Sparttna oltrmiporo and associated mud flats. Key word index: Riopnic sulpbur emissions, dimctbyl &bide, hydrogen sulpbide, carbon disulpbide, dimetbyl disulpbidc, wetland soils.
Fig 11: a) Sea surface height (SSH, cm), b) Sea surface temperature (SST, o C), c) Sea surface sa... more Fig 11: a) Sea surface height (SSH, cm), b) Sea surface temperature (SST, o C), c) Sea surface salinity (SSS, psu) which covers the sub-domain (15-20 o N, 60-70 o W) was obtained from the Experimental Real-Time Intra-Americas Sea Nowcast/Forecast System (IASNFS) from 1) February and 2) August 2005
Sunlight that arrives at the surface of the earth contains substantial amounts of energy. When su... more Sunlight that arrives at the surface of the earth contains substantial amounts of energy. When surface waters, which contain either natural or anthropogenic chromophores, are exposed to sunlight, light initiated chemical reactions often occur. Sunlight induced photochemical reactions in surface waters may broadly be defined as environmental aquatic photochemistry. Within aquatic photochemistry, it is possible to envision reactions involving either inorganic and/or organic molecules. These chemicals could be either natural or anthropogenic and may participate in either homogeneous or heterogeneous reactions. Very often in these environments, a complex array of primary and secondary photoprocesses are occurring simultaneously. Surface waters are diverse in nature. They might be near shore or inland wetland environments or mid-oceanic oligotrophic water. Until recently, sunlight induced photochemistry was not recognized as an important pathway for the transformation of natural and anthropogenic chemicals in surface waters. It is now well established that photochemically mediated processes are important in most, if not all, areas of aqueous phase environmental chemistry. Both direct, primary, and indirect photoprocesses have been documented in natural waters.
Measurements of H202 in rainwater collected in Miami, Florida, and the Bahama Islands area indica... more Measurements of H202 in rainwater collected in Miami, Florida, and the Bahama Islands area indicate the presenc e of H202 concentration levels ranging from (1-7) x 10-5 M. No systematic trends in H202 concentration were observed during an individual storm, in marked contrast to the behavior of other anions (e.g., [NO3-], [SO4=], and [C1-]). The data suggest that a substantial fraction of the H202 found in precipitation is generated by aqueous-phase reactions within the cloudwater rather than via rainout and washout of gaseous H202.
Gas Phase and Particulate Phase Organic Compositions at the Sydney Site During the 2002 Bay Regional Atmospheric Chemistry Experiment (BRACE)
AGU Fall Meeting Abstracts, Dec 1, 2003
During the Bay Regional Atmospheric Chemistry Experiment (BRACE) in 2002, particle and gas phase ... more During the Bay Regional Atmospheric Chemistry Experiment (BRACE) in 2002, particle and gas phase organic compounds were routinely measured at the Sydney site east of Tampa. This was the most easterly (inland) site occupied during the study and could be characterized as a rural clean air site which provided the background site for the Tampa urban area. Aircraft measurements were also performed using canisters to follow the urban air plume. Because of the proximity of Tampa and the transport of the urban air mass eastward, periodic enrichment episodes where anticipated. Hourly measurements of C2-C12 NMHCs were performed using a system composed of a gas trap coupled with a GC/FID. Aerosol samples were also collected for organic speciation. PM2.5 and size-segregated samples were respectively collected with a high volume sampler and Micro Orifice Uniform Deposit Impactors (MOUDIs). All particulate matter (PM) samples were collected on a 24 hours schedule with the exception of a few days while shorter schedules were used for the PM2.5. Samples were extracted using a mixture of dichloromethane/acetone/hexane, concentrated down and analyzed using gas chromatography-mass spectrometry (GC/MS). Gas phase results showed that isoprene was consistently the most common NMHC present and constituted the bulk of the OH reactivity. The measurements will be put into the context of other continental background measurements. Linkages to organic aerosol formation will also be explored. Organic speciation of PM showed that the Sydney site was representative of a rural site for most of May 2002. Concentrations, especially for polycyclic aromatic hydrocarbons (PAH), compared well with PM2.5 data obtained from other rural sites within the Southeastern United States. Only a few days showed concentrations higher than typical rural sites but without reaching urban values.
Correlation of UV-vis absorption and solar irradiance with depth in seawater
Annual Meeting Optical Society of America, 1989
Photochemical and optical properties of seawater are controlled by the absorbance spectrum of the... more Photochemical and optical properties of seawater are controlled by the absorbance spectrum of the chromophores and by the light intensity and spectral distribution at depth. These parameters are not commonly measured together. Solar penetration has previously been estimated from short-and long-wavelength insulation formulas or has been modeled from multiple wavelength attenuation formulas. On two cruises in the Caribbean Sea in the spring and fall of 1988, irradiance data were collected at selected depths in the photic zone and concurrently at the surface, using LICOR spectroradiometers. Absorbance measurements by a spectrophotometer were made on water collected by CTD casts within a few hours of the light profiles. Particulate scattering was determined by absorption measurements on filtered (0.45-µm) and unfiltered water samples.
Publisher Summary This chapter defines some of the possible photochemical processes that may be a... more Publisher Summary This chapter defines some of the possible photochemical processes that may be affecting the nature of organic materials found in seawater, and reviews some evidence for the occurrence of these processes in the marine environment. The efficiency of any photophysical or photochemical process is a function of both the properties of the reaction environment and the character of the excited state species. The fundamental quantity which is used to describe the efficiency of any photoprocess is the quantum yield ( ϕ ); it is useful in both quantifying the process and in elucidating the reaction mechanism. Quantum yield has the general definition of the number of events occumng divided by the number of photons absorbed. The understanding of marine photochemical processes and their effects on the organic fraction is still only rudimentary. The slow development of this potentially important area of marine chemistry is probably the result of a combination of factors including misconceptions about energy requirements for photochemical reactions and the depth of penetration of actinic radiation into seawater. An examination of the light absorbers in seawater reveals that many potential reactions are possible in the marine environment, and initial investigations have demonstrated that significant reactions are occurring there.
Reaction products from the chlorination of seawater. Final report 15 Jul 75-14 Jul 80
Chemical treatment of natural waters, in particular the use of chlorine as a biocide, modifies th... more Chemical treatment of natural waters, in particular the use of chlorine as a biocide, modifies the chemistry of these waters in ways that are not fully understood. The research described in this report examined both inorganic and organic reaction products from the chlorination of seawater using a variety of analytical approaches. Some analytical methods in widespread current use underestimate the
Bromoform Formation in Ozonated Groundwater Containing Bromide and Humic Substances
Ozone: Science & Engineering, 1986
... William J. Cooper1, Gary L. Amy2, Cynthia A. Moore3, and Rod G. Zilca3 1 Drinking Water Resea... more ... William J. Cooper1, Gary L. Amy2, Cynthia A. Moore3, and Rod G. Zilca3 1 Drinking Water Research Center, Florida International University ... wells situated next to the Alexander Orr water treatment plant, the Hollywood water treatment plant, the John Preston water treatment ...
Total optical attenuation in seawater is defined by the following equation (Jerlov, 1968): C tot ... more Total optical attenuation in seawater is defined by the following equation (Jerlov, 1968): C tot = ap + aDOM + bp + cw where ap = absorption coefficient for particles, aDOM is the absorption coefficient for the dissolved organic matter, bp is the scattering by particles, and cw is the attenuation by water (through absorption, and elastic and inelastic scattering). For coastal waters it is the first three terms of this equation that are responsible for the large range in optical attenuation and variation in color that are often observed. Also, these terms are interactive through a variety of processes involving transformations between the biota, DOM, and particulates. The processes affecting these transformations in coastal environments can be complex and dynamic; they include, but are not limited to recycling, sediment resuspension, precipitation, photochemical alteration, tidal flow and other physical transport and mixing processes.
Report Group 3 – Photochemistry in the sea-surface microlayer
The Sea Surface and Global Change
... The primary reactions of these halogen species should be oxidation of organic substrates, but... more ... The primary reactions of these halogen species should be oxidation of organic substrates, but substitution reactions of aromatic and unsatu-rated ... In Active Oxygen in Chemistry, ed. CS Foote etal., pp. ... Surface microlayer phenolic enrichments indicate sea surface slicks. ...
The emphasis in our ONR funded research is placed on characterizing the factors affecting the opt... more The emphasis in our ONR funded research is placed on characterizing the factors affecting the optical properties (i.e. attenuation and fluorescence) of coastal seawater. Particular emphasis is being placed on developing a better understanding of the differences and similarities between colored dissolved organic matter CDOM of marine and terrestrial origin, and the impact these properties have on the chemical and optical characteristics of coastal environments where their effects are most pronounced. The equipment assembled under this grant is being used both in the laboratory and in shipboard experiments to provide detailed characterization of the optical properties of coastal seawater. Such information once acquired can be applied to remote sensing modeling applications and the design of optical sensing detectors for probing the ocean.
AbUnct-Emission rates of tbc bio@c sulpbur pwr hydrogen sulpbidc, dimetbyl sulpbide, carbon disul... more AbUnct-Emission rates of tbc bio@c sulpbur pwr hydrogen sulpbidc, dimetbyl sulpbide, carbon disulpbidc and dimetbyl dirulpbide lmvc bcco maaurui from the cxposui soils of five wetland planet communitks in Florida Dimctbyl &bide and hydrogen rulpbide ven tbc predominant specks emitted. All tbc studied ozosystana 8bored did variation in the cmisaion rata of the biogcnic sulpbur gases with tbe bigbat emissions rata nccu&g early-to mid-afternoon, and tbc lowest cmiasion rates occuning during the arly mornin& The rcl8tivc magnitude of anissions from the individual ccosystcmfi followed the trend DidchIt spicata > Aaknda gemhans > Bath maritima a JVKW romvianus a Clodium jfmuaicense. only the a&ion rates from the paty D. spic~ro site uc comparable in magnitude lo previous emission measuremart in wetl8nd ocorynan~ of Sparttna oltrmiporo and associated mud flats. Key word index: Riopnic sulpbur emissions, dimctbyl &bide, hydrogen sulpbide, carbon disulpbide, dimetbyl disulpbidc, wetland soils.
Fig 11: a) Sea surface height (SSH, cm), b) Sea surface temperature (SST, o C), c) Sea surface sa... more Fig 11: a) Sea surface height (SSH, cm), b) Sea surface temperature (SST, o C), c) Sea surface salinity (SSS, psu) which covers the sub-domain (15-20 o N, 60-70 o W) was obtained from the Experimental Real-Time Intra-Americas Sea Nowcast/Forecast System (IASNFS) from 1) February and 2) August 2005
Sunlight that arrives at the surface of the earth contains substantial amounts of energy. When su... more Sunlight that arrives at the surface of the earth contains substantial amounts of energy. When surface waters, which contain either natural or anthropogenic chromophores, are exposed to sunlight, light initiated chemical reactions often occur. Sunlight induced photochemical reactions in surface waters may broadly be defined as environmental aquatic photochemistry. Within aquatic photochemistry, it is possible to envision reactions involving either inorganic and/or organic molecules. These chemicals could be either natural or anthropogenic and may participate in either homogeneous or heterogeneous reactions. Very often in these environments, a complex array of primary and secondary photoprocesses are occurring simultaneously. Surface waters are diverse in nature. They might be near shore or inland wetland environments or mid-oceanic oligotrophic water. Until recently, sunlight induced photochemistry was not recognized as an important pathway for the transformation of natural and anthropogenic chemicals in surface waters. It is now well established that photochemically mediated processes are important in most, if not all, areas of aqueous phase environmental chemistry. Both direct, primary, and indirect photoprocesses have been documented in natural waters.
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