The Experts below are selected from a list of 174 Experts worldwide ranked by ideXlab platform
Des Connell - One of the best experts on this subject based on the ideXlab platform.
-
Chlorohydrocarbon pesticides in the australian marine environment after banning in the period from the 1970s to 1980s
Marine Pollution Bulletin, 2002Co-Authors: Des Connell, Greg Miller, Shelly M AndersonAbstract:The Chlorohydrocarbon pesticides (CHPs) (principally DDT, dieldrin, hexachlorocyclohexane (HCH) including lindane, chlordane, heptachlor and heptachlorepoxide, aldrin and hexachlorobenzene (HCB)) were used extensively in Australia during the 1960s and 1970s. These were progressively banned from the 1970s with DDT being totally banned in 1987. The levels in marine waters are believed to have progressively declined as indicated by water in the Brisbane River, which consistently fell from maximum concentrations of about 1.7 microg/l in 1972-1973 to not detectable in 1986-1987. In some urban areas sediment concentrations, up to 1700 microg/kg dry weight, were recorded in the early 1990s which may reflect the reworking and exposure of older more contaminated material. Fish exhibited consistent occurrence of DDT, HCH, dieldrin and HCB through the 1970s to the 1990s. Maximum concentrations of DDT and dieldrin occurred generally in the 1970s at 40.3 and 8.8 microg/g wet weight, and minimums in the 1990s at 2.4 and 0.041 micro/g wet weight respectively. Inputs of dialdrin from sewage and DDT from the broad environment, reflected by the calculated daily human uptake in the diet, were shown to decline with half-lives of 1.1-1.5 and about 3 years respectively. This evidence suggests that banning of the CHPs has greatly reduced the inputs into the marine environment with consequent reductions in concentrations in biota but there is the occasional occurrence of relatively high concentrations.
-
environmental distribution of Chlorohydrocarbon contaminants associated with sydney sewage discharges
Marine Pollution Bulletin, 1996Co-Authors: Munro R Mortimer, Des ConnellAbstract:Abstract A steady-state nonequilibrium fugacity model incorporating the oceanographic dimensions of the environment receiving a sewage discharge from Sydney, Australia was used to predict the environmental fate of a range of Chlorohydrocarbon contaminants. The model showed advection in water to be the dominant removal process, accounting for all except 1–2% of the contaminants discharged. With the exception of the more water soluble dieldrin, the major portion of contaminant present in the area was held in the sediments. Bioconcentration and sediment sorption models were used with levels detected in the biota and sediments to calculate the ambient water concentrations of the Chlorohydrocarbon contaminants. The ambient water concentrations calculated using these models were in general agreement within a factor of about 2 in all but one case, and that was in agreement within an order of magnitude. The fugacity model was also used to estimate the rates of discharge of each of the contaminants. These were chlordane 83–640, DDT 150, dieldrin 1400–1500, hexachlorobenzene 360–400 and PCBs 55–96 g day −1 . Comparisons of the calculated ambient concentrations of each compound in the water and in fish in waters adjacent to the discharge point before and after its relocation from a cliff-face to a deepwater site indicated that relocation should result in an order of magnitude reduction.
-
a model of the environmental fate of Chlorohydrocarbon contaminants associated with sydney sewage discharges
Chemosphere, 1995Co-Authors: Munro R Mortimer, Des ConnellAbstract:Bioconcentration and sediment sorption models were used with levels detected in the biota and sediments to calculate the ambient water concentrations of Chlorohydrocarbon contaminants from a major outfall discharging sewage to the ocean near Malabar, in Sydney, Australia. The ambient water concentrations calculated using these models were in general agreement within a factor of about 2 in all but one case, and that was in agreement within an order of magnitude. A steady-state nonequilibrium fugacity model incorporating the oceanographic dimensions of the environment receiving the discharges was used to predict the environmental fate of a range of the Chlorohydrocarbon contaminants. The model showed advection in water to be the dominant removal process, accounting for all except 1-2% of the contaminants discharged. With the exception of the more water soluble dieldrin, the major portion of contaminant present in the area was held in the sediments. The model was also used to estimate the rates of discharge of each of the contaminants. These were chlordane 83-640, DDT 150, dieldrin 1400-1500, hexachlorobenzene 360-400 and PCBs 55-96 g per day. Comparisons of the calculated ambient concentrations of each compound in the water and in fish in waters adjacent to the cliff-face outfall before and after its relocation to a deepwater outfall site indicated that relocation resulted in a reduction to about 2% of the previous levels.
-
bioaccumulation of Chlorohydrocarbon pesticides by fish in the natural environment
Chemosphere, 1992Co-Authors: Murray C Cullen, Des ConnellAbstract:Abstract Examination of Chlorohydrocarbon pesticide data in fish from rivers on the North Coast of New South Wales, Australia suggests that exposure to upstream waters contaminated with dieldrin and DDT and metabolites leads to increasing residues of these substances with age. However, movement to clean oceanic and estuarine waters during the spawning migration downstream by adults results in depuration and lowering of the pesticide residues. This finding was supported by continuing increased residue levels in non-migrating fish throughout their life cycle. The Chlorohydrocarbon concentration in the fish was also used to estimate overall pesticide concentrations in the water of the rivers using the bioconcentration factor for fish calculated from the octanol/water partition coefficient. Analysis of the data suggests variations in residue levels observed with different geography and species were due principally to variations in the fat content and different exposure histories of the fish.
Roger E Summons - One of the best experts on this subject based on the ideXlab platform.
-
first detections of dichlorobenzene isomers and trichloromethylpropane from organic matter indigenous to mars mudstone in gale crater mars results from the sample analysis at mars instrument onboard the curiosity rover
Astrobiology, 2020Co-Authors: Daniel P. Glavin, Caroline Freissinet, Cyril Szopa, Maeva Millan, A Buch, H B Franz, Roger E SummonsAbstract:Chromatographic analysis of the Cumberland mudstone in Gale crater by the Sample Analysis at Mars (SAM) instrument revealed the detection of two to three isomers of dichlorobenzene. Their individual concentrations were estimated to be in the 0.5-17 ppbw range relative to the sample mass. We also report the first detection of trichloromethylpropane and the confirmation of the detection of chlorobenzene previously reported. Supporting laboratory experiments excluded the SAM internal background as the source of those compounds, thus confirming the organic carbon and chlorine of the newly detected Chlorohydrocarbons are indigenous to the mudstone sample. Laboratory experiments also demonstrated that the Chlorohydrocarbons were mainly produced from chemical reactions occurring in the SAM ovens between organic molecules and oxychlorines contained in the sample. The results we obtained show that meteoritic organics and tested chemical species (a polycyclic aromatic hydrocarbon, an amino acid, and a carboxylic acid) were plausible organic precursors of the chlorinated aromatic molecules detected with SAM, thus suggesting that they could be among the organic molecules present in the mudstone. Results from this study coupled with previously reported detections of chlorinated aromatics (<300 ppbw) indigenous to the same mudstone highlight that organics can be preserved from the harsh surface conditions even at shallow depth. The detection of new Chlorohydrocarbons with SAM confirms that organic molecules should have been available in an environment favorable to life forms, strengthening the habitability aspect of Gale crater.
-
Effect of the presence of chlorates and perchlorates on the pyrolysis of organic compounds: implications for measurements done with the SAM experiment onboard the Curiosity rover
2016Co-Authors: Maeva Millan, Daniel P. Glavin, Caroline Freissinet, Brad Sutter, Cyril Szopa, Arnaud Buch, Patrice Coll, P. Douglas Archer, Imène Belmahdi, Roger E SummonsAbstract:The Sample Analysis at Mars (SAM) experiment onboard the Curiosity rover of the Mars Science Laboratory mission is partly devoted to the in situ molecular analysis of gases evolving from solid samples collected on Mars surface/sub-surface. SAM has a gas-chromatograph coupled to a quadrupole mass spectrometer (GC-QMS) devoted to the separation and identification of organic and inorganic material [1]. Before proceeding to the GC-QMS analysis, the solid sample collected by Curiosity is subjected to a thermal treatment thanks to the pyrolysis oven to release the volatiles into the gas processing system. As the Viking landers in 1976 [2], SAM detected Chlorohydrocarbons with the pyrolysis GC-QMS experiment [3,4]. The detection of perchlorates salts in soil at the Phoenix Landing site [6] suggests that these chloro- hydrocarbons could come from the reaction of organics with oxychlorines. Oxychlorines indeed decomposed into molecular oxygen and volatile chlorine when heated and react with the organic matter in the samples by oxidation and/or chlorination processes. [3,5,7,8]. During SAM pyrolysis, samples are heated to 850◦C. SAM detected C1 to C3 chloroalkanes, entirely attributed to reaction products occurring during the pyrolysis experiment between oxychlorines and organic carbon from instrument background [3] and chlorobenzene and C2 to C4 dichloroalkanes produced by reaction between Mars endogenous organics with oxychlorines [4]. To help understanding the influence of perchlorate and chlorate salts on organic matter during SAM pyrolysis, we systemically study the reaction products formed during pyrolysis of various organic compounds mixed with various perchlorates and chlorates. We selected organics from simple molecule forms as for instance PAHs and amino acids to complex material (>30 carbon atoms) such as kerogen. The perchlorate and chlorate salts are prepared at 1 wt % concentration in silica and mixed with the organics to study the potential qualitative and/or quantitative effects. The experiments are performed on a laboratory GC-QMS with a Restek Rxi-5 column (30m x 0.25mm x 0.25μm) and an Intersciences pyrolyser. The mixture is pyrolyzed at different temperatures up to 900◦C to cover the SAM temperature range. Different experiments are done to discriminate the pyrolysis products directly coming from the organics, and those produced from the reaction with oxychlorine. These experiments are under progress and should bring key information on the potential to identify Martian organics when pyrolyzing solid samples. Depending on the organic families studied, we may find recurring molecules, which are potentially present in Mars’ surface samples. This work could thus highlight some organic precursors of the chlorinated compounds found on Mars, and support the interpretation of SAM measurements.
-
potential precursor compounds for Chlorohydrocarbons detected in gale crater mars by the sam instrument suite on the curiosity rover
Journal of Geophysical Research, 2016Co-Authors: Kristen E Miller, Benjamin Kotrc, Pascaline Francois, Daniel P. Glavin, Jennifer L. Eigenbrode, Caroline Freissinet, Roger E SummonsAbstract:The detection of chlorinated organic compounds in near-surface sedimentary rocks by the Sample Analysis at Mars (SAM) instrument suite aboard the Mars Science Laboratory Curiosity rover represents an important step toward characterizing habitable environments on Mars. However, this discovery also raises questions about the identity and source of their precursor compounds and the processes by which they become chlorinated. Here we present the results of analog experiments, conducted under conditions similar to SAM gas chromatography-mass spectrometry analyses, in which we pyrolyzed potential precursor compounds in the presence of various Cl salts and Fe oxides that have been identified in Martian sediments. While chloromethanes could not be unambiguously identified, 1,2-dichloropropane (1,2-DCP), which is one of the chlorinated compounds identified in SAM data, is formed from the chlorination of aliphatic precursors. Additionally, propanol produced more 1,2-DCP than nonfunctionalized aliphatics such as propane or hexanes. Chlorinated benzenes ranging from chlorobenzene to hexachlorobenzene were identified in experiments with benzene carboxylic acids but not with benzene or toluene. Lastly, the distribution of chlorinated benzenes depended on both the substrate species and the nature and concentration of the Cl salt. Ca and Mg perchlorate, both of which release O2 in addition to Cl2 and HCl upon pyrolysis, formed less chlorobenzene relative to the sum of all chlorinated benzenes than in experiments with ferric chloride. FeCl3, a Lewis acid, catalyzes chlorination but does not aid combustion. Accordingly, both the precursor chemistry and sample mineralogy exert important controls on the distribution of chlorinated organics.
Munro R Mortimer - One of the best experts on this subject based on the ideXlab platform.
-
environmental distribution of Chlorohydrocarbon contaminants associated with sydney sewage discharges
Marine Pollution Bulletin, 1996Co-Authors: Munro R Mortimer, Des ConnellAbstract:Abstract A steady-state nonequilibrium fugacity model incorporating the oceanographic dimensions of the environment receiving a sewage discharge from Sydney, Australia was used to predict the environmental fate of a range of Chlorohydrocarbon contaminants. The model showed advection in water to be the dominant removal process, accounting for all except 1–2% of the contaminants discharged. With the exception of the more water soluble dieldrin, the major portion of contaminant present in the area was held in the sediments. Bioconcentration and sediment sorption models were used with levels detected in the biota and sediments to calculate the ambient water concentrations of the Chlorohydrocarbon contaminants. The ambient water concentrations calculated using these models were in general agreement within a factor of about 2 in all but one case, and that was in agreement within an order of magnitude. The fugacity model was also used to estimate the rates of discharge of each of the contaminants. These were chlordane 83–640, DDT 150, dieldrin 1400–1500, hexachlorobenzene 360–400 and PCBs 55–96 g day −1 . Comparisons of the calculated ambient concentrations of each compound in the water and in fish in waters adjacent to the discharge point before and after its relocation from a cliff-face to a deepwater site indicated that relocation should result in an order of magnitude reduction.
-
a model of the environmental fate of Chlorohydrocarbon contaminants associated with sydney sewage discharges
Chemosphere, 1995Co-Authors: Munro R Mortimer, Des ConnellAbstract:Bioconcentration and sediment sorption models were used with levels detected in the biota and sediments to calculate the ambient water concentrations of Chlorohydrocarbon contaminants from a major outfall discharging sewage to the ocean near Malabar, in Sydney, Australia. The ambient water concentrations calculated using these models were in general agreement within a factor of about 2 in all but one case, and that was in agreement within an order of magnitude. A steady-state nonequilibrium fugacity model incorporating the oceanographic dimensions of the environment receiving the discharges was used to predict the environmental fate of a range of the Chlorohydrocarbon contaminants. The model showed advection in water to be the dominant removal process, accounting for all except 1-2% of the contaminants discharged. With the exception of the more water soluble dieldrin, the major portion of contaminant present in the area was held in the sediments. The model was also used to estimate the rates of discharge of each of the contaminants. These were chlordane 83-640, DDT 150, dieldrin 1400-1500, hexachlorobenzene 360-400 and PCBs 55-96 g per day. Comparisons of the calculated ambient concentrations of each compound in the water and in fish in waters adjacent to the cliff-face outfall before and after its relocation to a deepwater outfall site indicated that relocation resulted in a reduction to about 2% of the previous levels.
Peilin Zhang - One of the best experts on this subject based on the ideXlab platform.
-
energy dependent normal and unusually large inverse chlorine kinetic isotope effects of simple Chlorohydrocarbons in collision induced dissociation by gas chromatography electron ionization tandem mass spectrometry
Journal of Mass Spectrometry, 2020Co-Authors: Peilin ZhangAbstract:Kinetic isotope effects (KIEs) occurring in mass spectrometry (MS) can provide in-depth insights into the fragmentation behaviors of compounds of interest in MS. Yet, the fundamentals of KIEs in collision-induced dissociation (CID) in tandem mass spectrometry (MS/MS) are unclear, and information about chlorine KIEs (Cl-KIEs) of organochlorines in MS is particularly scarce. This study investigated the Cl-KIEs of dichloromethane, trichloroethylene, and tetrachloroethylene during CID using gas chromatography-electron ionization triple-quadrupole MS/MS. Cl-KIEs were evaluated with MS signal intensities. All the organochlorines presented large inverse Cl-KIEs (<1, the departures of Cl-KIEs from 1 denote the magnitudes of Cl-KIEs), showing the largest magnitudes of 0.797, 0.910, and 0.892 at the highest collision energy (60 eV) for dichloromethane, trichloroethylene, and tetrachloroethylene, respectively. For dichloromethane, both intra-ion and inter-ion Cl-KIEs were studied, within the ranges of 0.820-1.020 and 0.797-1.016, respectively, showing both normal and inverse Cl-KIEs depending on collision energies. The observed Cl-KIEs generally declined from large normal to extremely large inverse values with increasing collision energies from 0 to 60 eV but were inferred to be independent of MS signal intensities. The Cl-KIEs are dominated by critical energies at low internal energies of precursor ions, resulting in normal Cl-KIEs; while at high internal energies, the Cl-KIEs are controlled by rotational barriers (or looseness/tightness of transition states), which lead to isotope-competitive reactions in dechlorination and thereby inverse Cl-KIEs. It is concluded that the Cl-KIEs may depend on critical energies, bond strengths, available internal energies, and transition state looseness/tightness. The findings of this study yield new insights into the fundamentals of Cl-KIEs of organochlorines during CID and may be conducive to elucidating the underlying mechanisms of KIEs in collision-induced and photo-induced reactions in the actual world.
Maeva Millan - One of the best experts on this subject based on the ideXlab platform.
-
first detections of dichlorobenzene isomers and trichloromethylpropane from organic matter indigenous to mars mudstone in gale crater mars results from the sample analysis at mars instrument onboard the curiosity rover
Astrobiology, 2020Co-Authors: Daniel P. Glavin, Caroline Freissinet, Cyril Szopa, Maeva Millan, A Buch, H B Franz, Roger E SummonsAbstract:Chromatographic analysis of the Cumberland mudstone in Gale crater by the Sample Analysis at Mars (SAM) instrument revealed the detection of two to three isomers of dichlorobenzene. Their individual concentrations were estimated to be in the 0.5-17 ppbw range relative to the sample mass. We also report the first detection of trichloromethylpropane and the confirmation of the detection of chlorobenzene previously reported. Supporting laboratory experiments excluded the SAM internal background as the source of those compounds, thus confirming the organic carbon and chlorine of the newly detected Chlorohydrocarbons are indigenous to the mudstone sample. Laboratory experiments also demonstrated that the Chlorohydrocarbons were mainly produced from chemical reactions occurring in the SAM ovens between organic molecules and oxychlorines contained in the sample. The results we obtained show that meteoritic organics and tested chemical species (a polycyclic aromatic hydrocarbon, an amino acid, and a carboxylic acid) were plausible organic precursors of the chlorinated aromatic molecules detected with SAM, thus suggesting that they could be among the organic molecules present in the mudstone. Results from this study coupled with previously reported detections of chlorinated aromatics (<300 ppbw) indigenous to the same mudstone highlight that organics can be preserved from the harsh surface conditions even at shallow depth. The detection of new Chlorohydrocarbons with SAM confirms that organic molecules should have been available in an environment favorable to life forms, strengthening the habitability aspect of Gale crater.
-
Effect of the presence of chlorates and perchlorates on the pyrolysis of organic compounds: implications for measurements done with the SAM experiment onboard the Curiosity rover
2016Co-Authors: Maeva Millan, Daniel P. Glavin, Caroline Freissinet, Brad Sutter, Cyril Szopa, Arnaud Buch, Patrice Coll, P. Douglas Archer, Imène Belmahdi, Roger E SummonsAbstract:The Sample Analysis at Mars (SAM) experiment onboard the Curiosity rover of the Mars Science Laboratory mission is partly devoted to the in situ molecular analysis of gases evolving from solid samples collected on Mars surface/sub-surface. SAM has a gas-chromatograph coupled to a quadrupole mass spectrometer (GC-QMS) devoted to the separation and identification of organic and inorganic material [1]. Before proceeding to the GC-QMS analysis, the solid sample collected by Curiosity is subjected to a thermal treatment thanks to the pyrolysis oven to release the volatiles into the gas processing system. As the Viking landers in 1976 [2], SAM detected Chlorohydrocarbons with the pyrolysis GC-QMS experiment [3,4]. The detection of perchlorates salts in soil at the Phoenix Landing site [6] suggests that these chloro- hydrocarbons could come from the reaction of organics with oxychlorines. Oxychlorines indeed decomposed into molecular oxygen and volatile chlorine when heated and react with the organic matter in the samples by oxidation and/or chlorination processes. [3,5,7,8]. During SAM pyrolysis, samples are heated to 850◦C. SAM detected C1 to C3 chloroalkanes, entirely attributed to reaction products occurring during the pyrolysis experiment between oxychlorines and organic carbon from instrument background [3] and chlorobenzene and C2 to C4 dichloroalkanes produced by reaction between Mars endogenous organics with oxychlorines [4]. To help understanding the influence of perchlorate and chlorate salts on organic matter during SAM pyrolysis, we systemically study the reaction products formed during pyrolysis of various organic compounds mixed with various perchlorates and chlorates. We selected organics from simple molecule forms as for instance PAHs and amino acids to complex material (>30 carbon atoms) such as kerogen. The perchlorate and chlorate salts are prepared at 1 wt % concentration in silica and mixed with the organics to study the potential qualitative and/or quantitative effects. The experiments are performed on a laboratory GC-QMS with a Restek Rxi-5 column (30m x 0.25mm x 0.25μm) and an Intersciences pyrolyser. The mixture is pyrolyzed at different temperatures up to 900◦C to cover the SAM temperature range. Different experiments are done to discriminate the pyrolysis products directly coming from the organics, and those produced from the reaction with oxychlorine. These experiments are under progress and should bring key information on the potential to identify Martian organics when pyrolyzing solid samples. Depending on the organic families studied, we may find recurring molecules, which are potentially present in Mars’ surface samples. This work could thus highlight some organic precursors of the chlorinated compounds found on Mars, and support the interpretation of SAM measurements.
-
potential sources of artifacts and backgrounds generated by the sample preparation of sam
47th LPSC Lunar and Planetary Science Conference, 2016Co-Authors: A Buch, Daniel P. Glavin, Jennifer L. Eigenbrode, Caroline Freissinet, Cyril Szopa, Maeva Millan, Imène Belmahdi, P Coll, Michel Cabane, Rafael NavarrogonzalezAbstract:Sample Analysis at Mars (SAM) is one of the instruments of the MSL mission. Three analytical devices are onboard SAM: the Tunable Laser Spectrometer (TLS), the Gas Chromatography (GC) and the Mass Spectrometer (MS). To adapt the nature of a sample to the analytical devices used, a sample preparation and gas processing system implemented with (a) a pyrolysis system, (b) wet chemistry: MTBSTFA and TMAH (c) the hydrocarbon trap (silica beads, Tenax® TA and Carbosieve G) and the injection trap (Tenax® GR composed of Tenax® TA and 30% of graphite) are employed to concentrate vol-atiles released from the sample prior to GC-MS analysis [1]. This study investigates several propositions for chlo-rinated hydrocarbon formation detected in the SAM background by looking for: (a) all products coming from the interaction of Tenax® and perchlorates, (b) also between some soil sample and perchlorates and (c) sources of chlorinated hydrocarbon precursors. Here we report on the detection of Chlorohydrocarbon compounds and their potential origin.