Jerry A. Leenheer

Bio: Jerry A. Leenheer is an academic researcher from United States Geological Survey. The author has contributed to research in topics: Dissolved organic carbon & Organic matter. The author has an hindex of 26, co-authored 52 publications receiving 7838 citations.

Fluorescence excitation-emission matrix regional integration to quantify spectra for dissolved organic matter.

Abstract: Excitation−emission matrix (EEM) fluorescence spectroscopy has been widely used to characterize dissolved organic matter (DOM) in water and soil. However, interpreting the >10,000 wavelength-dependent fluorescence intensity data points represented in EEMs has posed a significant challenge. Fluorescence regional integration, a quantitative technique that integrates the volume beneath an EEM, was developed to analyze EEMs. EEMs were delineated into five excitation−emission regions based on fluorescence of model compounds, DOM fractions, and marine waters or freshwaters. Volumetric integration under the EEM within each region, normalized to the projected excitation−emission area within that region and dissolved organic carbon concentration, resulted in a normalized region-specific EEM volume (Φi,n). Solid-state carbon nuclear magnetic resonance (13C NMR), Fourier transform infrared (FTIR) analysis, ultraviolet−visible absorption spectra, and EEMs were obtained for standard Suwannee River fulvic acid and 15 h...

Comprehensive approach to preparative isolation and fractionation of dissolved organic carbon from natural waters and wastewaters.

Abstract: Ward and DeGraeve (6) have shown that SO2 was an effective way to eliminate the residual toxicity of chlorinated effluent. These investigators concluded that 17 freshwater fish and one macroinvertebrate were not affected after Sop dechlorination. Similar results have also been reported by other authors using various dechlorinating agents (29-32). Chlorine will likely continue to be used for biofouling control and disinfecting purposes by power plants and sewage treatment plants, respectively. Therefore, all feasible means to reduce the toxicity of this biocide should be thoroughly investigated in order to minimize effects on aquatic organisms. In this preliminary study we have demonstrated that dechlorination with sulfur dioxide is an effective means to reduce the toxicity of chlorine to striped bass eggs and larvae in an estuarine system. Striped bass ichthyoplankton exposed to dechlorination for exposure periods of 4 h or less experienced minimal mortality. In contrast, concentrations of TRC greater than 0.13 mg/L were found to cause high mortality to larvae after 4 h of exposure; therefore, SO2 dechlorination a t exposure periods of 4 h or less could completely eliminate mortality. We recommend future investigations on other estuarine organisms that may be subjected to SO2 dechlorination associated with industrial effluent. Future studies should be conducted to evaluate the effects of short exposures of ‘I’RC-SO2 followed by observation periods of several days in control conditions. This type of study would provide data on possible sublethal effects. The effects of interacting AT and dechlorination conditions should be evaluated in order to determine responses of aquatic organisms subjected to power-plant discharge conditions. Evaluation of possible acute and sublethal effects of halogenated organics resulting from dechlorination should also be evaluated.

A comparison of water solubility enhancements of organic solutes by aquatic humic materials and commercial humic acids

Abstract: Water solubility enhancements of 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (p,p'-DDT), 2,4,5,2',5'-pentachlorobiphenyl (2,4,5,2',5'-PCB), and 2,4,4'-trichlorobiphenyl (2,4,4'-PCB) by dissolved organic matter have been studied with the following samples: (1) acidic water samples from the Suwannee River, Georgia, and the Sopchoppy River, Florida; (2) a humic extract of a nearly neutral pH water from the Calcasieu River, Louisiana; (3) commercial humic acids from the Aldrich Chemical Co and Fluka-Tridom Chemical Corp The calculated partition coefficients on a dissolved organic carbon basis (K/sub doc/) for organic solutes with water samples and aquatic humic extracts from this and earlier studies indicate that the enhancement effect varies with the molecular composition of the aquatic humic materials, The K/sub doc/ values with water and aquatic humic samples are, however, far less than the observed K/sub doc/ values obtained with the two commercial samples, by factors of about 4-20 In view of this finding, one should be cautious in interpreting the effects of the dissolved organic matter on solubility enhancement of organic solutes on the basis of the use of commercial humic acids 14 references, 3 figures, 2 tables

Photoproduction of hydrated electrons from natural organic solutes in aquatic environments.

Abstract: Etude de l'effet d'une photolyse UV eclair laser sur des composes organiques dissous dans l'eau ou contenus dans le sol. Les resultats de cette etude montre que l'electron hydrate joue un role important dans la persistance de polluants electronegatifs mais n'a pas d'effet notable sur la production de peroxyde d'hydrogene

Fluorescence excitation-emission matrix regional integration to quantify spectra for dissolved organic matter.

Abstract: Excitation−emission matrix (EEM) fluorescence spectroscopy has been widely used to characterize dissolved organic matter (DOM) in water and soil. However, interpreting the >10,000 wavelength-dependent fluorescence intensity data points represented in EEMs has posed a significant challenge. Fluorescence regional integration, a quantitative technique that integrates the volume beneath an EEM, was developed to analyze EEMs. EEMs were delineated into five excitation−emission regions based on fluorescence of model compounds, DOM fractions, and marine waters or freshwaters. Volumetric integration under the EEM within each region, normalized to the projected excitation−emission area within that region and dissolved organic carbon concentration, resulted in a normalized region-specific EEM volume (Φi,n). Solid-state carbon nuclear magnetic resonance (13C NMR), Fourier transform infrared (FTIR) analysis, ultraviolet−visible absorption spectra, and EEMs were obtained for standard Suwannee River fulvic acid and 15 h...

Organic geochemistry of natural waters

Abstract: This book is written as a reference on organic substances in natural waters and as a supplementary text for graduate students in water chemistry. The chapters address five topics: amount, origin, nature, geochemistry, and characterization of organic carbon. Of these topics, the main themes are the amount and nature of dissolved organic carbon in natural waters (mainly fresh water, although seawater is briefly discussed). It is hoped that the reader is familiar with organic chemistry, but it is not necessary. The first part of the book is a general overview of the amount and general nature of dissolved organic carbon. Over the past 10 years there has been an exponential increase in knowledge on organic substances in water, which is the result of money directed toward the research of organic compounds, of new methods of analysis (such as gas chromatography and mass spectrometry), and most importantly, the result of more people working in this field. Because of this exponential increase in knowledge, there is a need to pull together and summarize the data that has accumulated from many disciplines over the last decade.

Spectrofluorometric characterization of dissolved organic matter for indication of precursor organic material and aromaticity

Abstract: We studied the fluorescence properties of fulvic acids isolated from streams and rivers receiving predominantly terrestrial sources of organic material and from lakes with microbial sources of organic material. Microbially derived fulvic acids have fluorophores with a more sharply defined emission peak occurring at lower wavelengths than fluorophores in terrestrially derived fulvic acids. We show that the ratio of the emission intensity at a wavelength of 450 nm to that at 500 nm, obtained with an excitation of 370 nm, can serve as a simple index to distinguish sources of isolated aquatic fulvic acids. In our study, this index has a value of ;1.9 for microbially derived fulvic acids and a value of ;1.4 for terrestrially derived fulvic acids. Fulvic acids isolated from four large rivers in the United States have fluorescence index values of 1.4‐1.5, consistent with predominantly terrestrial sources. For fulvic acid samples isolated from a river, lakes, and groundwaters in a forested watershed, the fluorescence index varied in a manner suggesting different sources for the seepage and streamfed lakes. Furthermore, we identified these distinctive fluorophores in filtered whole water samples from lakes in a desert oasis in Antarctica and in filtered whole water samples collected during snowmelt from a Rocky Mountain stream. The fluorescence index measurement in filtered whole water samples in field studies may augment the interpretation of dissolved organic carbon sources for understanding carbon cycling in aquatic ecosystems.

PCR inhibitors - occurrence, properties and removal.

Abstract: The polymerase chain reaction (PCR) is increasingly used as the standard method for detection and characterization of microorganisms and genetic markers in a variety of sample types. However, the method is prone to inhibiting substances, which may be present in the analysed sample and which may affect the sensitivity of the assay or even lead to false-negative results. The PCR inhibitors represent a diverse group of substances with different properties and mechanisms of action. Some of them are predominantly found in specific types of samples thus necessitating matrix-specific protocols for preparation of nucleic acids before PCR. A variety of protocols have been developed to remove the PCR inhibitors. This review focuses on the general properties of PCR inhibitors and their occurrence in specific matrices. Strategies for their removal from the sample and for quality control by assessing their influence on the individual PCR test are presented and discussed.