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At least 415 records · Page 23Linked to original sources
USGS2000

Stable hydrogen and oxygen isotope ratios for selected sites of the National Oceanic and Atmospheric Administration's Atmospheric Integrated Research Monitoring Network (AIRMoN)

Increasingly, hydrologic studies require information on the isotopic composition of natural waters. This report presents stable hydrogen (δ 2 H) and oxygen isotope ratios (δ 18 0) of precipitation samples from seven selected sites of the National Oceanic and Atmospheric Administration's Atmospheric Integrated Research Monitoring Network (AIRMoN) collected during the years 1992-1994.

Delaware;Illinois;New York;Ohio;Pennsylvania;Tenne↗
USGS2014

Multi-elemental analysis of aqueous geological samples by inductively coupled plasma-optical emission spectrometry

Typically, 27 major, minor, and trace elements are determined in natural waters, acid mine drainage, extraction fluids, and leachates of geological and environmental samples by inductively coupled plasma-optical emission spectrometry (ICP-OES). At the discretion of the analyst, additional elements may be determined after suitable method modifications and performance data are established. Samples are preserved in 1–2 percent nitric acid (HNO3) at sample collection or as soon as possible after collection. The aqueous samples are aspirated into the ICP-OES discharge, where the elemental emission signals are measured simultaneously for 27 elements. Calibration is performed with a series of matrix-matched, multi-element solution standards.

Open-File Report↗
USGS2018

Laboratory evaluation of the Sea-Bird Scientific HydroCycle-PO4 phosphate sensor

Sea-Bird Scientific’s HydroCycle-PO 4 phosphate sensor is a single-analyte wet-chemistry sensor designed for in situ environmental monitoring. The unit was evaluated at the U.S. Geological Survey Hydrologic Instrumentation Facility to assess the accuracy of the sensor in solutions with known phosphorous concentration and to test the effects of chromophoric (colored) dissolved organic matter (CDOM) and natural water matrixes on sensor accuracy. Accuracy was tested with three standards: 0.110, 0.174, and 0.260 milligram per liter, as phosphorous (mg/L as P). The 0.110- and 0.260-mg/L standards were made from a dilution of a National Institute of Standards and Technology-traceable phosphate-phosphorous standard with Type I deionized water (DIW). Average measured phosphate concentrations of the tested standards (0.110, 0.174, and 0.260 mg/L as P) in DIW were 0.132, 0.181, and 0.310 mg/L as P, for differences of 20, 4, and 19 percent, respectively. Measured phosphate concentration of a tested standard was biased by the addition of tea water filtered through a 0.45-micrometer pore size filter (filtered tea water [FTW]) simulating the effect of CDOM. An aliquot of the filtered tea solution was sent to a certified environmental laboratory, which reported a less than reporting level (<0.004 mg/L as P) phosphate concentration. True color of the FTW was measured at 380 platinum-cobalt units by using Standard Methods 8025. For this FTW test, the measured phosphate concentration for the clear 0.260 mg/L as P standard averaged 0.366 mg/L as P. This concentration increased to an average of 0.653 mg/L as P with the addition of 10 percent FTW, and to an average of 0.859 mg/L as P with the addition of 20 percent FTW. These test results indicate a positive bias of up to 40 percent of the concentrations of the measured phosphate concentrations when CDOM is present and indicate a proportional increase in an apparent concentration of phosphorus instrument response as CDOM concentration increases.

Open-File Report↗
USGS1987

WATEQ4F - a personal computer Fortran translation of the geochemical model WATEQ2 with revised data base

A FORTRAN 77 version of the PL/1 computer program for the geochemical model WATEQ2, which computes major and trace element speciation and mineral saturation for natural waters has been developed. The code (WATEQ4F) has been adapted to execute on an IBM PC or compatible microcomputer. Two versions of the code are available, one operating with IBM Professional FORTRAN and an 8087 or 89287 numeric coprocessor, and one which operates without a numeric coprocessor using Microsoft FORTRAN 77. The calculation procedure is identical to WATEQ2, which has been installed on many mainframes and minicomputers. Limited data base revisions include the addition of the following ions: AlHS04(++), BaS04, CaHS04(++), FeHS04(++), NaF, SrC03, and SrHCO3(+). This report provides the reactions and references for the data base revisions, instructions for program operation, and an explanation of the input and output files. Attachments contain sample output from three water analyses used as test cases and the complete FORTRAN source listing. U.S. Geological Survey geochemical simulation program PHREEQE and mass balance program BALANCE also have been adapted to execute on an IBM PC or compatible microcomputer with a numeric coprocessor and the IBM Professional FORTRAN compiler.

Open-File Report↗
USGS1983

Historical surface deformation near Oildale, California

Historical surface deformation recognized in the southern San Joaquin Valley and adjacent Sierra Nevada foothills near Oildale, Calif., includes: normal and apparently aseismic dip slip along four faults; subsidence within or adjacent to the Kern Front, Poso Creek, Mount Poso, and Fruitvale oil fields; and uplift of much of the area within and north of the Kern River oil field. As much as 0.34 m of vertical separation has been observed along a 5.2-km segment of the Kern Front fault, the structural barrier separating the Kern Front oil field on the west from the Kern River field to the east. Similar separations of as much as 0.15 m and 0.32 m, respectively, have also been identified along the surface traces of two en echelon faults between the Premier and Enas areas of the Poso Creek oil field and the fault that defines the southeast flank of the Premier area. The measured height changes are based on both unadjusted observed elevations and minimally constrained adjusted elevations developed from repeated control levelings referred to a relatively stable local bench mark; measurement error in the reported vertical movements probably is less than 0.05 m. Differential subsidence of at least 0.31 m (1903-68) and 0.05 m (1926/27/30/31-59) has occurred within the Kern Front and Fruitvale oil fields, respectively; subsidence of as much as 0.33 m (1903-53) and 0.19 m (1931-63) has also been measured along the north edge of the Premier area of the Poso Creek oil field and the south edge of the Main area of the Mount Poso field, respectively. Differential uplift of as much as 0.11 m and 0.13 m occurred within and immediately north of the Kern River oil field between 1903 and 1968, and similar uplift of as much as 0.19 m was measured along the north edge of the Dominion area of the Mount Poso field between 1931 and 1963. Differential subsidence within the Kern Front and Fruitvale oil fields and along the edges of the Poso Creek and Mount Poso fields is attributable to subsurface compaction owing to fluid withdrawal; absence of subsidence within the much larger Kern River field probably is the result of either production from compaction-resistant materials or natural water flooding that has acted to preserve reservoir fluid pressures in the generally shallow producing beds. Contemporary displacements on the Kern Front fault and those along the faults within and adjacent to the Poso Creek oil field are attributable largely or entirely to changes in the subsurface stress regime associated with reservoir compaction; accumulated elastic strain of tectonic derivation conceivably contributed to the development of these displacements. The apparent uplift within and north of the Kern River oil field and along the north edge of the Mount Poso field probably is due in part to compaction of as much as 0.055 m beneath the reference bench mark; most of this apparent uplift, however, is interpreted as an effect of tectonic tilting.

California↗
USGS2022

Assessment of fecal contamination sources to Alley Creek, Queens County, New York, August 2020–June 2021

Alley Creek, a tributary to Little Neck Bay in Queens County, New York, has been designated by the New York State Department of Environmental Conservation as impaired (Class I) for fecal coliform because of pollution from combined sewer overflow, including stormwater runoff. The U.S. Geological Survey, in cooperation with the New York City Department of Environmental Protection, conducted a 1-year study from August 2020 to June 2021 using microbial source tracking (MST) methods to assess potential host sources of fecal contamination (for example, human, canine, and waterfowl) from the following: three outfall sites, TI–025, TI–008, and TI–024; an artesian well (Q277) adjacent to Alley Creek; and natural waters within the Alley Creek watershed and Little Neck Bay. In addition to analyzing for MST markers, field measurements such as water temperature and specific conductance, samples for total suspended solids, and fecal indicator bacteria (FIB; enterococci and fecal coliform) were collected. Pharmaceutical compounds were also collected for analysis, and the results of sampling were compared spatially and temporally to help support management decisions related to mitigation of fecal sources to Alley Creek. Factors that could affect concentrations, including tidal conditions, seasonality, and weather conditions, also were assessed. A sediment resuspension laboratory experiment was designed to replicate tidal activity in Alley Creek using sediment collected in the sewers and on the shoreline, as well as water collected from Oakland Lake. These sediment samples were assessed to understand the relation between sediment resuspension and FIB in the water column. The human MST markers used for this study, Bacteroides HF183/BacR287, and crAssphage CPQ_056 and CPQ_064, were detected in most samples (27 of 28) collected at the three outfall sites along Alley Creek, whereas the canine marker BacCan was less prevalent (20 of 28 samples) but exhibited a pattern of relative concentrations similar to the human markers. The waterfowl MST GFD marker was detected in 7 of 28 samples collected at the three outfall sites. Human MST markers were not detected at Oakland Lake (which drains through a combined sewer line to Alley Creek at TI–008), indicating minimal or nonexistent influence of sewage contamination in the lake. Groundwater samples collected from Q277 did not contain any MST markers, and concentrations of fecal coliform were less than 10 colony forming units per 100 milliliters. Although FIB did not correlate well with total suspended solids for individual sample sets, samples collected following precipitation and high-turbidity events were typically found to have higher concentrations of FIB than dry-weather samples. Results from the pharmaceutical compounds analysis provided additional evidence for determining known and suspected human sources when coupled with MST markers. Together, the MST, pharmaceutical, and FIB data generated by this study, along with supplementary data such as locations of point sources, locations of wildlife populations, and tidal exchange data, may provide reliable information on source identification and transport mechanisms of fecal contamination to Alley Creek.

New York↗
USGS2003

Biogeochemical processes that produce dissolved organic matter from wheat straw

The chemical reactions that lead to the formation of dissolved organic matter (DOM) in natural waters are poorly understood. Studies on the formation of DOM generally are complicated because almost all DOM isolates have been derived from mixtures of plant species composed of a wide variety of different types of precursor compounds for DOM formation. This report describes a study of DOM derived mainly from bales of wheat straw that had been left in a field for several years. During this period of time, black water from the decomposing wheat straw accumulated in pools in the field. The nuclear magnetic resonance and infrared spectra of the black water DOM indicate that it is composed almost entirely of lignin and carbohydrate polymeric units. Analysis by high-performance size-exclusion chromatography with multi-angle laser-light scattering detection indicates that the number average molecular weight of the DOM is 124,000 daltons. The results presented in this report indicate that the black water DOM is composed of hemicellulose chains cross-linked to lignin oligomers. These types of structures have been shown to exist in the hemicellulose matrix of plant cell walls. The cross-linked lignin-hemicellulose complexes apparently were released from partially degraded wheat-straw cell walls with little alteration. In solution in the black water, these lignin-hemicellulose polymers fold into compact globular particles in which the nonpolar parts of the polymer form the interiors of the particles and the polar groups are on the exterior surfaces of the particles. The tightly folded, compact conformation of these particles probably renders them relatively resistant to microbial degradation. This should be especially the case for the aromatic lignin structures that will be buried in the interiors of the particles.

Water-Resources Investigations Report↗
USGS1982

Methodologies for extraction of dissolved inorganic carbon for stable carbon isotope studies: Evaluation and alternatives

The gas evolution and the strontium carbonate precipitation techniques to extract dissolved inorganic carbon (DIC) for stable carbon isotope analysis were investigated. Theoretical considerations, involving thermodynamic calculations and computer simulation pointed out several possible sources of error in delta carbon-13 measurements of the DIC and demonstrated the need for experimental evaluation of the magnitude of the error. An alternative analytical technique, equilibration with out-gassed vapor phase, is proposed. The experimental studies revealed that delta carbon-13 of the DIC extracted from a 0.01 molar NaHC03 solution by both techniques agreed within 0.1 per mil with the delta carbon-13 of the DIC extracted by the precipitation technique, and an increase of only 0.27 per mil in that extracted by the gas evolution technique. The efficiency of extraction of DIC decreased with sulfate concentration in the precipitation technique but was independent of sulfate concentration in the gas evolution technique. Both the precipitation and gas evolution technique were found to be satisfactory for extraction of DIC from different kinds of natural water for stable carbon isotope analysis, provided appropriate precautions are observed in handling the samples. For example, it was found that diffusion of atmospheric carbon dioxide does alter the delta carbon-13 of the samples contained in polyethylene bottles; filtration and drying in the air change the delta carbon-13 of the samples contained in polyethylene bottles; filtration and drying in the air change the delta carbon-13 of the precipitation technique; hot manganese dioxide purification changes the delta carbon-13 of carbon dioxide. (USGS)

Water-Resources Investigations Report↗
USGS1986

Temporal changes in sulfate, chloride, and sodium concentrations in four eastern Pennsylvania streams

Trend analyses of 20 years or more of chemical quality and streamflow data for four streams in eastern Pennsylvania indicate that sulfate has decreased significantly in three of the four basins studied, while sodium and chloride have generally increased. The majority of chemical quality changes occurred in the late 1950 's and early 1960 's coincident with significant cultural changes. It is believed that these chemical quality changes are presently of little or no environmental consequence, as the concentrations are well within the range of those found in natural waters. Decreases in sulfate follow a regional trend concurrent with the conversion of home and industrial heating units from high to low sulfur coal, gas, and oil. The most significant decreases were observed in those basins severely affected by mine-drainage where pumpage has decreased significantly in the past 25 years, thereby further reducing the sulfur content of the streams. The observed increases in chloride and sodium are attributed to population increases and shifts from rural to suburban communities with concurrent increase in the percentage of the population using municipal waste treatment facilities and the increased use of salt on roadways. The concentrations of dissolved chloride, which are from two to three times higher in recent years, reach a peak in January, coincident with the application of salt to melt ice on the roadways. (USGS)

Water-Resources Investigations Report↗
USGS1960

Residue method for common minor elements

A spectrographic method is described for the quantitative analysis of many minor elements in natural water. The excitation of the water residue using a direct-current arc provides a method for the detection of elements present in very low concentrations. The concentration of the elements is determined in percent of the dry residue. The results are readily expressed in parts per million by multiplying the determined percent concentration of an element by the dissolved solids content of the water sample. The method is flexible and can be applied to the analysis of water of variable composition and dissolved-solids content.

Water Supply Paper↗
USGS1967

Form and stability of aluminum hydroxide complexes in dilute solution

Laboratory studies of solutions 4.53 x 10 -4 to 4.5 x 10 -5 molal (12.2-1.2 ppm) in aluminum, in 0.01 molal sodium perchlorate, were conducted to obtain information as to the probable behavior of aluminum in natural water. When the solutions were brought to pH 7.5-9.5 and allowed to stand for 24 hours, a precipitate was obtained which was virtually amorphous as shown by X-rays, and which had a solubility equivalent to that of boehmite. This precipitate had a hydrolysis constant (*Ks4) of 1.93 x 10 -13a. When solutions were allowed to stead at this pH range for 10 days, their precipitates gave the X-ray pattern of bayerite (*Ks4 = 1.11 > (10- 4). These hydrolysis constants were obtained at 25?C. and corrected to zero ionic strength and are in close agreement with other published values. The predominant dissolved form in this pH range is Al(OH) -4. Below neutral pH (7.0) the dissolved aluminum species consist of octahedral units in which each aluminum ion is surrounded by six water molecules or hydroxide ions. Single units such as Al(OH2)6 + 3 and AlOH(OH2)5+2 are most abundant below pH 5.0, and where the molar ratio (r) of combined hydroxide to total dissolved aluminum is low. When r is greater than 1.0, polymerization of the octahedral units occurs. When r is between 2.0 and 3.0, solutions aged for 10 days or more contained colloidal particles between 0.10 and 0.45 ? in diameter. Particles whose diameters were greater than 0.10 ? were identified by X-ray diffraction as gibbsite. Particles smaller than 0.10 ? were also present and were shown by means of the electron microscope to have a hexagonal crystal pattern. Structured material consisting of sheets of coalesced six-membered rings of aluminum ions held together by double OH bridges has a distinctive kinetic behavior. This property was used to determine amounts of polymerized material in solutions having r between 1.0 and 3.0 after aging times ranging from a few hours to more than 4 months. Aging increased the size and orderliness of the polymeric aggregates and was accompanied by a decrease in the pH of the solution. The kinetic experiments and stoichiometric data for solutions aged for long periods provided a means of determining activities of polymerized aluminum. From these values the solubility product for microcrystalline gibbsite was determined to be 2.24 x 10 -3, and its free energy of formation, -? 272.3 0.4 kcal per mole. Where polymerization was observed, the process did not stop with small polynuclear complexes containing a few aluminum ions, but proceeded with aging until macromolecules or colloidal-sized particles were formed.

Water Supply Paper↗
USGS1988

Specific conductance; theoretical considerations and application to analytical quality control

This report considers several theoretical aspects and practical applications of specific conductance to the study of natural waters. A review of accepted measurements of conductivity of secondary standard 0.01 N KCl solution suggests that a widely used algorithm for predicting the temperature variation in conductivity is in error. A new algorithm is derived and compared with accepted measurements. Instrumental temperature compensation circuits based on 0.01 N KCl or NaCl are likely to give erroneous results in unusual or special waters, such as seawater, acid mine waters, and acid rain. An approach for predicting the specific conductance of a water sample from the analytically determined major ion composition is described and critically evaluated. The model predicts the specific conductance to within ?8 percent (one standard deviation) in waters with specific conductances of 0 to 600 microS/cm. Application of this approach to analytical quality control is discussed.

Water Supply Paper↗
USGS2003

Temperature correction in conductivity measurements

Electrical conductivity has been widely used in freshwater research but usual methods employed by limnologists for converting measurements to conductance at a given temperature have not given uniformly accurate results. The temperature coefficient used to adjust conductivity of natural waters to a given temperature varies depending on the kinds and concentrations of electrolytes, the temperature at the time of measurement, and the temperature to which measurements are being adjusted. The temperature coefficient was found to differ for various lake and stream waters, and showed seasonal changes. High precision can be obtained only by determining temperature coefficients for each water studied. Mean temperature coefficients are given for various temperature ranges that may be used where less precision is required.

Limnology and Oceanography↗
USGS1965

Detection and measurement of organic lampricide residues

The selective lampricide, 3-trifluoromethyl-4-nitrophenol (TFM), and its synergist, 5,2'-dichloro-4'-nitrosalicylanilide (DCN), are separable from natural waters by anion exchange. The adsorbed compounds can then be recovered from the resin as concentrates by elution with selective solvent mixtures. Measurements of the amounts of lampricides in the final concentrates can be made colorimetrically at 395 mI? for TFM and at 530 mI? for the safranin complex of DCN. TFM has also been separated for quantitative determination from homogenates of whole fish. The fish is first macerated in a blender and then hydrolyzed in hot, 3 N hydrochloric acid. The amount of background color, due to certain components of the fish in the hydrolysate, is reduced by one or a combination of three methods: (1) a series of three extractions with ether, methylene chloride, and benzene; (2) cation exchange followed by methylene chloride extraction; or (3) ether extraction followed by anion exchange and subsequent desorption with amyl acetate-acetic acid.

Technical Report↗
USGS2006

Herpetofaunal diversity of Alligator River National Wildlife Refuge, North Carolina

In the past century, habitat alteration and fragmentation have increased dramatically, which increases the need for improving our understanding of how species and biological communities react to these modifications. A national strategy on biological diversity has focused attention on how these habitat modifications affect species, especially herpetofauna (i.e., changes in species richness, community evenness and similarity, and dominant/rare species). As part of this strategy, we surveyed Alligator River National Wildlife Refuge, a coastal, mixed second-growth forested swamp (MFS) and pocosin wetland (PW), in North Carolina for amphibians and reptiles from September 2000 to August 2001. We randomly selected three sites (3 x 3 km) in two major habitat types (MFS, PW) and completed random surveys and trapping using transects, quadrats, nighttime aural road surveys, drift fences, canal transects, coverboards, incidental captures, and evening road surveys. We also collected herpetofauna opportunistically throughout the refuge to establish an updated species list. For analysis, we used Shannon-Weiner species diversity (H'), evenness (1'), species richness and species detectability (COMDYN4), and community percent similarity index to determine herpetofaunal community differences. We estimated 39 species in MFS and 32 species in PW (P < 0.10). Species detectability was similar between habitats (0.84 to 0.86). More reptilian species (+ 31 %) inhabited MFS than PW, but estimated amphibian species richness was identical (17 spp.). H' was higher (P < 0.000 I) for PW (2.6680) than for MFS (2.1535) because of lower J' in the latter (0.6214 vs. 0.8010). Dominance of three Rana species caused lower J' and H' in MFS. Similarity between the communities was 56.6%; we estimated 22-24 species in common for each habitat (95% CI = 18 to 31 spp.). We verified 49 of the 52 herpetofaunal species on the refuge that were known to exist in the area. Restoration of natural water flows may affect herpetofaunal diversity, which may be monitored during a restoration project. Currently, the refuge retains historical levels of herpetofaunal diversity for the region.

Southeastern Naturalist↗
USGS1999

Natural attenuation of chloroacetinilide herbicides in aquatic systems

Chloroacetanilide herbicides (e.g. alachlor and metolachlor) and their breakdown products are frequently found in agriculturally impacted and other natural waters. Although these compounds are usually present at low concentrations in aquatic systems, defining their fate and attenuation rate is important because they can be toxic at comparatively low exposure levels. This paper summarizes results from a four-year research program assessing factors that affect herbicide attenuation rates and breakdown product formation patterns in aquatic systems. Over 70 different field microcosms (11.3 m 3 cylindrical fiberglass tanks) were selectively manipulated (in replicate) to create nine unique aquatic ecosystems for this study. Alachlor and/or metolachlor were added to these units and transformations were observed over time. Alachlor half-lives ranged from 6.0 days to more than 100 days depending upon the temperature, oxygen conditions, and the nutrient conditions in the microcosm waters. The highest rates of alachlor decay were observed in warm, nutrient-rich, anaerobic water columns, whereas the lowest alachlor decay rates were observed under cooler, aerobic, oligotrophic water conditions. Similar relationships were observed for metolachlor, although metolachlor decay rates were about 40% slower. Our data suggest that herbicides will decay rapidly in waters that are high in nutrients possibly resulting from human activities. Alternately, low nutrient or pristine waters will have the lowest rates of herbicide decay. On a policy level, all efforts should be made to prevent exposure of comparatively pristine waters to herbicide inputs.

Conference Paper↗
USGS2011

Pathogens and diseases of freshwater mussels in the United States: Studies on bacterial transmission and depuration

Unionid mussels are recognized as important contributors to healthy aquatic ecosystems, as well as bioindicators of environmental perturbations. Because they are sedentary, filter feeding animals and require hosts (i.e., fishes) to transform embryonic glochidia, mussels are susceptible to direct adverse environmental parameters, and indirect parameters that restrict the timely presence of the host(s). Their numbers have declined in recent decades to a point that this fauna is regarded as one of the most imperiled in North America. The most significant threat to populations of native unionids in recent years has been the introduction and spread of zebra mussels Dreissena polymorpha. Many federal and state agencies, and private interests are now engaged in mussel conservation efforts, including collecting selected imperiled species from impacted rivers and lakes and propagating them at refuges for future population augmentations. One essential consideration with mussel propagation and their intensive culture at refugia is the prevention of pathogen introductions and control of diseases. Currently, there are few reports of etiological agents causing diseases among freshwater mussels; however, because of increased observations of mussel die-offs in conjunction with transfers of live animals between natural waters and refugia, disease problems can be anticipated to emerge. This review summarizes research to develop bacterial isolation techniques, study pathogen transmission between fish and mussels, identify causes of seasonal mussel die-offs, and develop non-destructive methods for pathogen detection. These efforts were done to develop disease preventative techniques for use by resource managers to avoid potential large-scale disease problems in restoration and population augmentation efforts among imperiled populations.

Conference Paper↗
USGS2014

Experimental design and quality assurance: in situ fluorescence instrumentation

Both instrument design and capabilities of fluorescence spectroscopy have greatly advanced over the last several decades. Advancements include solid-state excitation sources, integration of fiber optic technology, highly sensitive multichannel detectors, rapid-scan monochromators, sensitive spectral correction techniques, and improve data manipulation software (Christian et al., 1981, Lochmuller and Saavedra, 1986; Cabniss and Shuman, 1987; Lakowicz, 2006; Hudson et al., 2007). The cumulative effect of these improvements have pushed the limits and expanded the application of fluorescence techniques to numerous scientific research fields. One of the more powerful advancements is the ability to obtain in situ fluorescence measurements of natural waters (Moore, 1994). The development of submersible fluorescence instruments has been made possible by component miniaturization and power reduction including advances in light sources technologies (light-emitting diodes, xenon lamps, ultraviolet [UV] lasers) and the compatible integration of new optical instruments with various sampling platforms (Twardowski et at., 2005 and references therein). The development of robust field sensors skirt the need for cumbersome and or time-consuming filtration techniques, the potential artifacts associated with sample storage, and coarse sampling designs by increasing spatiotemporal resolution (Chen, 1999; Robinson and Glenn, 1999). The ability to obtain rapid, high-quality, highly sensitive measurements over steep gradients has revolutionized investigations of dissolved organic matter (DOM) optical properties, thereby enabling researchers to address novel biogeochemical questions regarding colored or chromophoric DOM (CDOM). This chapter is dedicated to the origin, design, calibration, and use of in situ field fluorometers. It will serve as a review of considerations to be accounted for during the operation of fluorescence field sensors and call attention to areas of concern when making this type of measurement. Attention is also given to ways in which in-water fluorescence measurements have revolutionized biogeochemical studies of CDOM and how those measurements can be used in conjunction with remotely sense satellite data to understand better the biogeochemistry of DOM in aquatic environments.

Book chapter↗