The Experts below are selected from a list of 5721 Experts worldwide ranked by ideXlab platform
Peter G. Hartel - One of the best experts on this subject based on the ideXlab platform.
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exposing water samples to ultraviolet light improves fluorometry for detecting human fecal contamination
Water Research, 2007Co-Authors: Peter G. Hartel, Charles Hagedorn, Jennifer L. Mcdonald, Jared A. Fisher, Michael A. Saluta, Lisa C. Gentit, Steven L. Smith, Nehru S. Mantripragada, Jerold W. Dickerson, Kerry J. RitterAbstract:Abstract Fluorometry identifies human fecal contamination by detecting optical brighteners in environmental waters. Because optical brighteners are sensitive to sunlight, we determined if we could improve fluorometry by exposing water samples to ultraviolet (UV) light to differentiate between optical brighteners and other fluorescing organic compounds. Optical brighteners were likely present when the relative percentage difference in fluorometric value of the water before and after UV light exposure was > 30 % (glass cuvettes, 30 min exposure) or > 15 % (polymethacrylate cuvettes, 5 min exposure). In a blind study, we correctly identified the presence or absence of optical brighteners in 178 of 180 (99%) of the samples tested with a more expensive field Fluorometer and in 175 of 180 (97%) of the samples tested with a less expensive handheld Fluorometer. In the field, the method correctly identified two negative and three positive locations for human fecal contamination. When combined with counts of fecal bacteria, the new fluorometric method may be a simple, quick, and easy way to identify human fecal contamination in environmental waters.
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improving fluorometry as a source tracking method to detect human fecal contamination
Estuaries and Coasts, 2007Co-Authors: Peter G. Hartel, Jennifer L. Mcdonald, Lisa C. Gentit, Sarah N J Hemmings, Karen Rodgers, Katy A Smith, Yaritza Riveratorres, Richard L. Kuntz, Carolyn N. Belcher, Ernesto OteroAbstract:In a continuing effort to develop inexpensive source tracking methods to detect human fecal contamination in environmental waters, targeted sampling was combined with fluorometry. Targeted sampling works by identifying hot spots of fecal contamination through multiple samplings over ever-decreasing distances. Fluorometry identifies human fecal contamination by detecting optical brighteners, primarily from laundry detergents. Because organic matter fluoresces and interferes with fluorometry, two locations were chosen for sampling: waters relatively low in organic matter at Mayaguez Bay, Puerto Rico, and waters relatively high in organic matter at St. Simons Island, Georgia. In Puerto Rico, targeted sampling and fluorometry quickly and easily identified two hot spots of human fecal contamination in the Yaguez River, which flows through the city of Mayaguez. Another source tracking method, detection of theesp gene, confirmed their human origin. On St. Simous Island, targeted sampling and fiuorometry identified two hot spots of potential human fecal contamination. Detection of theesp gene confirmed the human origin of one site but not the other, most likely because background organic matter fluorescence interfered with fhiorometry. A separate experiment showed that adding a 436-um emission filter to the Fluorometer reduced this background fluorescence by > 50%. With the 436-nm Filter in place, another sampling was conducted on St. Simons Island, and the second hot spot was identified as fecal contamination from birds. As long as the Fluorometer was equipped with a 436-nm filter and organic matter concentrations were considered, targeted sampling combined with fluorometry was a relatively inexpensive method for identifying human fecal contamination in water.
Ernesto Otero - One of the best experts on this subject based on the ideXlab platform.
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improving fluorometry as a source tracking method to detect human fecal contamination
Estuaries and Coasts, 2007Co-Authors: Peter G. Hartel, Jennifer L. Mcdonald, Lisa C. Gentit, Sarah N J Hemmings, Karen Rodgers, Katy A Smith, Yaritza Riveratorres, Richard L. Kuntz, Carolyn N. Belcher, Ernesto OteroAbstract:In a continuing effort to develop inexpensive source tracking methods to detect human fecal contamination in environmental waters, targeted sampling was combined with fluorometry. Targeted sampling works by identifying hot spots of fecal contamination through multiple samplings over ever-decreasing distances. Fluorometry identifies human fecal contamination by detecting optical brighteners, primarily from laundry detergents. Because organic matter fluoresces and interferes with fluorometry, two locations were chosen for sampling: waters relatively low in organic matter at Mayaguez Bay, Puerto Rico, and waters relatively high in organic matter at St. Simons Island, Georgia. In Puerto Rico, targeted sampling and fluorometry quickly and easily identified two hot spots of human fecal contamination in the Yaguez River, which flows through the city of Mayaguez. Another source tracking method, detection of theesp gene, confirmed their human origin. On St. Simous Island, targeted sampling and fiuorometry identified two hot spots of potential human fecal contamination. Detection of theesp gene confirmed the human origin of one site but not the other, most likely because background organic matter fluorescence interfered with fhiorometry. A separate experiment showed that adding a 436-um emission filter to the Fluorometer reduced this background fluorescence by > 50%. With the 436-nm Filter in place, another sampling was conducted on St. Simons Island, and the second hot spot was identified as fecal contamination from birds. As long as the Fluorometer was equipped with a 436-nm filter and organic matter concentrations were considered, targeted sampling combined with fluorometry was a relatively inexpensive method for identifying human fecal contamination in water.
Ulrich Schreiber - One of the best experts on this subject based on the ideXlab platform.
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coral photobiology studied with a new imaging pulse amplitude modulated Fluorometer
Journal of Phycology, 2005Co-Authors: Peter J Ralph, Ulrich Schreiber, Rolf Gademann, Michael Kuhl, Anthony W D LarkumAbstract:A new high-resolution imaging Fluorometer (Imaging-PAM) was used to identify heterogeneity of photosynthetic activity across the surface of corals. Three species were examined: Acropora nobilis Dana (branching), Goniastrea australiensis Edwards & Haime (massive), and Pavona decussata Dana (plate). Images of fluorescence parameters (F, F m ', effective quantum yield, optimal quantum yield, electron transport rate, relative photosynthetic rate, and non-photochemical quenching) allowed heterogeneity to be detected in terms of position on colony and indicated that the photosynthetic activity of polyp and coenosarc tissues responded differently to changing light for all three species. The Imaging-PAM offers a special routine, with which images of PAR absorption (absorptivity) are obtained. In this way, for the first time it has become possible to derive images of the relative photosynthesis rate. Polyps had a lower PAR absorptivity than coenosarc tissue for A. nobilis and P. decussata, whereas G. australiensis showed the opposite pattern. Acropora nobilis showed heterogeneity along the longitudinal axis of the branch, which could be differentiated from the effect of variations in illumination across the rugose and curved surface. Diel changes were apparent and influenced the longitudinal heterogeneity along the A. nobilis branch. Images were also obtained showing the degree of photoinhibition caused by high-light stress across a coral surface at a hitherto unobtainable level of resolution.
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pam Fluorometer based on medium frequency pulsed xe flash measuring light a highly sensitive new tool in basic and applied photosynthesis research
Photosynthesis Research, 1993Co-Authors: Ulrich Schreiber, Christian Neubauer, Ulrich SchliwaAbstract:A newly developed modulation Fluorometer is described which employs repetitive 1 μs Xe-flashes for excitation light. Similar to the standard PAM Chlorophyll Fluorometer, which uses 1 μs LED pulses for measuring light, the integrated measuring light intensity is sufficiently low to monitor the dark-fluorescence level, Fo. The maximal fluorescence yield, Fm, can be determined with high selectivity upon application of a saturating light pulse. The Xe-PAM displays exceptionally high sensitivity, enabling quenching analysis at chlorophyll concentrations as low as 1 μg/l, thus allowing to assess photosynthesis of phytoplankton in natural waters like lakes, rivers and oceans. Due to high flexibility in the choice of excitation and emission wavelengths, this system also provides the experimental basis for a thorough study of fluorescence and photosynthesis properties of various algae classes with differing antenna organisation. By appropriate modifications, the instrument may as well be used to measure with great sensitivity and selectivity other types of fluorescence (e.g. NADPH-fluorescence), as well as light-scattering and absorbance changes.
Anthony W D Larkum - One of the best experts on this subject based on the ideXlab platform.
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coral photobiology studied with a new imaging pulse amplitude modulated Fluorometer
Journal of Phycology, 2005Co-Authors: Peter J Ralph, Ulrich Schreiber, Rolf Gademann, Michael Kuhl, Anthony W D LarkumAbstract:A new high-resolution imaging Fluorometer (Imaging-PAM) was used to identify heterogeneity of photosynthetic activity across the surface of corals. Three species were examined: Acropora nobilis Dana (branching), Goniastrea australiensis Edwards & Haime (massive), and Pavona decussata Dana (plate). Images of fluorescence parameters (F, F m ', effective quantum yield, optimal quantum yield, electron transport rate, relative photosynthetic rate, and non-photochemical quenching) allowed heterogeneity to be detected in terms of position on colony and indicated that the photosynthetic activity of polyp and coenosarc tissues responded differently to changing light for all three species. The Imaging-PAM offers a special routine, with which images of PAR absorption (absorptivity) are obtained. In this way, for the first time it has become possible to derive images of the relative photosynthesis rate. Polyps had a lower PAR absorptivity than coenosarc tissue for A. nobilis and P. decussata, whereas G. australiensis showed the opposite pattern. Acropora nobilis showed heterogeneity along the longitudinal axis of the branch, which could be differentiated from the effect of variations in illumination across the rugose and curved surface. Diel changes were apparent and influenced the longitudinal heterogeneity along the A. nobilis branch. Images were also obtained showing the degree of photoinhibition caused by high-light stress across a coral surface at a hitherto unobtainable level of resolution.
Jennifer L. Mcdonald - One of the best experts on this subject based on the ideXlab platform.
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exposing water samples to ultraviolet light improves fluorometry for detecting human fecal contamination
Water Research, 2007Co-Authors: Peter G. Hartel, Charles Hagedorn, Jennifer L. Mcdonald, Jared A. Fisher, Michael A. Saluta, Lisa C. Gentit, Steven L. Smith, Nehru S. Mantripragada, Jerold W. Dickerson, Kerry J. RitterAbstract:Abstract Fluorometry identifies human fecal contamination by detecting optical brighteners in environmental waters. Because optical brighteners are sensitive to sunlight, we determined if we could improve fluorometry by exposing water samples to ultraviolet (UV) light to differentiate between optical brighteners and other fluorescing organic compounds. Optical brighteners were likely present when the relative percentage difference in fluorometric value of the water before and after UV light exposure was > 30 % (glass cuvettes, 30 min exposure) or > 15 % (polymethacrylate cuvettes, 5 min exposure). In a blind study, we correctly identified the presence or absence of optical brighteners in 178 of 180 (99%) of the samples tested with a more expensive field Fluorometer and in 175 of 180 (97%) of the samples tested with a less expensive handheld Fluorometer. In the field, the method correctly identified two negative and three positive locations for human fecal contamination. When combined with counts of fecal bacteria, the new fluorometric method may be a simple, quick, and easy way to identify human fecal contamination in environmental waters.
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improving fluorometry as a source tracking method to detect human fecal contamination
Estuaries and Coasts, 2007Co-Authors: Peter G. Hartel, Jennifer L. Mcdonald, Lisa C. Gentit, Sarah N J Hemmings, Karen Rodgers, Katy A Smith, Yaritza Riveratorres, Richard L. Kuntz, Carolyn N. Belcher, Ernesto OteroAbstract:In a continuing effort to develop inexpensive source tracking methods to detect human fecal contamination in environmental waters, targeted sampling was combined with fluorometry. Targeted sampling works by identifying hot spots of fecal contamination through multiple samplings over ever-decreasing distances. Fluorometry identifies human fecal contamination by detecting optical brighteners, primarily from laundry detergents. Because organic matter fluoresces and interferes with fluorometry, two locations were chosen for sampling: waters relatively low in organic matter at Mayaguez Bay, Puerto Rico, and waters relatively high in organic matter at St. Simons Island, Georgia. In Puerto Rico, targeted sampling and fluorometry quickly and easily identified two hot spots of human fecal contamination in the Yaguez River, which flows through the city of Mayaguez. Another source tracking method, detection of theesp gene, confirmed their human origin. On St. Simous Island, targeted sampling and fiuorometry identified two hot spots of potential human fecal contamination. Detection of theesp gene confirmed the human origin of one site but not the other, most likely because background organic matter fluorescence interfered with fhiorometry. A separate experiment showed that adding a 436-um emission filter to the Fluorometer reduced this background fluorescence by > 50%. With the 436-nm Filter in place, another sampling was conducted on St. Simons Island, and the second hot spot was identified as fecal contamination from birds. As long as the Fluorometer was equipped with a 436-nm filter and organic matter concentrations were considered, targeted sampling combined with fluorometry was a relatively inexpensive method for identifying human fecal contamination in water.