Heavy mineral stratigraphy of the Unayzah Formation and Basal Khuff Clastics (Carboniferous to Permian) of Central Saudi Arabia

A study of heavy mineral assemblages in the Unayzah Reservoir sandstones of central Saudi Arabia has identified successive changes in provenance signature. These define four heavy mineral units that are of regional extent and largely coincident with the four main depositional units defined by previous authors: Unayzah C, Unayzah B, Unayzah A and the Basal Khuff Clastics. Sandstone bodies with anomalous mineral signatures also occur, however, especially within the Unayzah B Member. These are attributed to local supply of sand from pre-Unayzah Paleozoic sandstones exposed on the Central Arabian Arch and on intrabasinal highs. The stratigraphic changes in mineralogy reflect successive developments in the geography and climate of the region and in the pattern of sand sourcing and transport. The Unayzah C sands and the majority of Unayzah B sands were derived from the south but whereas the southerly derived Unayzah C sands appear to have been derived from pre-existing mature sandstones, those of Unayzah B were sourced from a wider range of rock types including crystalline basement. This contrast is interpreted as indicating that a significant hiatus may separate the two units. The Unayzah B sands are also characterised by the common presence of apatite, indicating that the source rocks were relatively unweathered. This observation is compatible with the glacial origin attributed to many of the Unayzah B sediments. A further change in provenance signature takes place at the base the newly recognised ‘un-named middle Unayzah member’, equivalent to the base of Unayzah A of previous authors. This is associated with the onset of red-bed sedimentation throughout the area. Unayzah A sedimentation was terminated by a fall in sea level that led to the formation of a widespread unconformity and to the development of deeply incised valleys along the western basin margin. In most of the study area this unconformity corresponds to the base of the Khuff Formation, but in the east of the area, where the succession is more complete, it is believed to occur within the Unayzah Formation, at a level equivalent to the base of the Upper Gharif Member of Oman. By identifying lateral and vertical changes in sand provenance, heavy mineral analysis provides an important additional tool in the stratigraphic analysis of the Permian sandstone succession of Saudi Arabia, both at the regional scale and wand at the scale of individual reservoir sandstone successions

Development of a biomarker for penconazole: a human oral dosing study and a survey of UK residents’ exposure

Penconazole is a widely used fungicide in the UK; however, to date, there have been no peer-reviewed publications reporting human metabolism, excretion or biological monitoring data. The objectives of this study were to i) develop a robust analytical method, ii) determine biomarker levels in volunteers exposed to penconazole, and, finally, to iii) measure the metabolites in samples collected as part of a large investigation of rural residents’ exposure. An LC-MS/MS method was developed for penconazole and two oxidative metabolites. Three volunteers received a single oral dose of 0.03 mg/kg body weight and timed urine samples were collected and analysed. The volunteer study demonstrated that both penconazole-OH and penconazole-COOH are excreted in humans following an oral dose and are viable biomarkers. Excretion is rapid with a half-life of less than four hours. Mean recovery of the administered dose was 47% (range 33%–54%) in urine treated with glucuronidase to hydrolyse any conjugates. The results from the residents’ study showed that levels of penconazole-COOH in this population were low with >80% below the limit of detection. Future sampling strategies that include both end of exposure and next day urine samples, as well as contextual data about the route and time of exposure, are recommended

Estimate of global atmospheric organic aerosol from oxidation of biogenic hydrocarbons

The results from a series of outdoor chamber experiments establishing the atmospheric aerosol-forming potential of fourteen terpenoid hydrocarbons have been used to estimate the annual amount of secondary organic aerosol formed globally from compounds emitted by vegetation. Hydroxyl radical, ozone, and nitrate radical oxidation each contribute to aerosol formation in full-photooxidation experiments; because oxidation by nitrate radical under ambient, remote conditions is likely to be negligible, parameters describing aerosol formation from hydroxyl radical and ozone reaction only are developed. Chamber results, temporally and spatially resolved, compound-specific estimates of biogenic hydrocarbon emissions, and hydroxyl radical and ozone fields are combined to lead to an estimate for atmospheric secondary organic aerosol formed annually from biogenic precursors of 18.5 Tg, a number smaller than the previously published estimate of 30–270 Tg [Andreae and Crutzen, 1997]

Organic aerosol formation from the oxidation of biogenic hydrocarbons

A series of outdoor chamber experiments has been used to establish and characterize the significant atmospheric aerosol-forming potentials of the most prevalent biogenic hydrocarbons emitted by vegetation. These compounds were also studied to elucidate the effect of structure on aerosol yield for these types of compounds. Because oxidation products partition between the gas and aerosol phases, the aerosol yields of the parent biogenic hydrocarbons depend on the concentration of organic aerosol into which these products can be absorbed. For organic mass concentrations between 5 and 40 µg m^(-3), mass-based yields in photooxidation experiments range from 17 to 67% for sesquiterpenes, from 2 to 23% for cyclic diolefins, from 2 to 15% for bicyclic olefins, and from 2 to 6% for the acyclic triolefin ocimene. In these photooxidation experiments, hydroxyl and nitrate radicals and ozone can contribute to consumption of the parent hydrocarbon. For bicyclic olefins (α-pinene, β-pinene, Δ^3-carene, and sabinene), experiments were also carried out at daytime temperatures in a dark system in the presence of ozone or nitrate radicals alone. For ozonolysis experiments, resulting aerosol yields are less dependent on organic mass concentration, when compared to full, sunlight-driven photooxidation. Nitrate radical experiments exhibit extremely high conversion to aerosol for β-pinene, sabinene, and Δ^3-carene. The relative importance of aerosol formation from each type of reaction for bicyclic olefin photooxidation is elucidated

Comparison of residents' pesticide exposure with predictions obtained using the UK regulatory exposure assessment approach.

AbstractThe UK regulatory methods currently used for estimating residents' potential pesticide exposure were assessed to determine whether they provide sufficiently conservative estimates. A non-random sample of 149 residents living within 100 m of fields where pesticides were sprayed provided first morning void urine samples one and/or two days after spraying. Using farmers’ spray information, regulatory exposure assessment (REA) models were applied to estimate potential pesticide intake among residents, with a toxicokinetic (TK) model used to estimate urinary biomarker concentrations in the mornings of the two days following the spray. These were compared with actual measured urinary biomarker concentrations obtained following the spray applications. The study focused on five pesticides (cypermethrin, penconazole, captan, chlorpyrifos and chlormequat). All measured cypermethrin urinary biomarker levels were lower than the REA-predicted concentrations. Over 98% and 97% of the measured urinary biomarker concentrations for penconazole and captan respectively were lower than the REA-predicted exposures. Although a number of the chlorpyrifos and chlormequat spray-related urinary biomarker concentrations were greater than the predictions, investigation of the background urinary biomarker concentrations suggests these were not significantly different from the levels expected had no pesticide spraying occurred. The majority of measured concentrations being well below the REA-predicted concentrations indicate that, in these cases, the REA is sufficiently conservative

Impaired decision making following escalation of cocaine self-administration predicts vulnerability to relapse in rats.

Impairments in cost-benefit decision making represent a cardinal feature of drug addiction. However, whether these alterations predate drug exposure, thereby contributing to facilitating loss of control over drug intake, or alternatively arise as a result of drug use and subsequently confer vulnerability to relapse has yet to be determined. Male Sprague-Dawley rats were trained to self-administer (SA) cocaine during 19 daily long-access (12-h) sessions; conditions reliably shown to promote escalation. One week after cocaine SA, rats underwent an extinction/relapse test immediately followed by conditioned stimuli-, stress-, and drug-primed reinstatement challenges. The influence of escalated cocaine intake on decision making was measured over time by four test sessions of a rodent analogue of the Iowa Gambling Task (rGT), once prior to cocaine exposure and then 1 day, 1 week, and 1 month after the last SA session. Substantial individual variability was observed in the influence of escalated cocaine SA on decision-making performance. A subset of rats displayed pronounced deficits, while others showed unaffected or even improved performance on the rat Gambling Task (rGT) 24 hours after the last SA session. When challenged with a relapse test after 1 week of forced abstinence, animals that showed impaired decision making following SA displayed an increased propensity to respond for cocaine under extinction. These data suggest that decision-making deficits in individuals with drug addiction are not antecedent to-but arise as a consequence of-drug exposure. Moreover, these data indicate that susceptibility to the deleterious effects of drugs on decision making confers vulnerability toward relapse.Medical Research Council Leverhulme Trus

Validation of trichloroacetic acid exposure via drinking water during pregnancy using a urinary TCAA biomarker

Disinfection by-product (DBP) exposure during pregnancy may be related to reduced fetal growth, but the evidence is inconclusive and improved DBP exposure assessment is required. The authors conducted a nested exposure study on a subset (n=39) of pregnant women in the Born in Bradford cohort to assess validity of TCAA exposure assessment based on tap water sampling and self-reported water-use; water-use questionnaire validity; and use of a one-time urinary TCAA biomarker. TCAA levels in urine and home tap water supply were quantified, and water use was measured via a questionnaire and 7-day diary, at 28 weeks gestation. Diary and urine measures were repeated later in pregnancy (n=14). TCAA level in home tap water supply was not correlated with urinary TCAA (0.18, P=0.29). Cold unfiltered tap water intake at home measured by questionnaire was correlated with urinary TCAA (0.44, P=0.007), but correlation was stronger still for cold unfiltered tap water intake reported over the 3 days prior to urine sampling (0.60, P<0.001). For unemployed women TCAA ingestion at home, derived from tap water sampling and self-reported water-use, correlated strongly with urinary TCAA (0.78, P<0.001), but for employed women the correlation was weak (0.31, P=0.20). Results suggest individual tap water intake is most influential in determining TCAA exposure variability in this cohort, and that TCAA ingestion at home is a valid proxy for TCAA exposure for unemployed women but less satisfactory for employed women

Reconstruction of Exposure to m-Xylene from Human Biomonitoring Data Using PBPK Modelling, Bayesian Inference, and Markov Chain Monte Carlo Simulation

There are numerous biomonitoring programs, both recent and ongoing, to evaluate environmental exposure of humans to chemicals. Due to the lack of exposure and kinetic data, the correlation of biomarker levels with exposure concentrations leads to difficulty in utilizing biomonitoring data for biological guidance values. Exposure reconstruction or reverse dosimetry is the retrospective interpretation of external exposure consistent with biomonitoring data. We investigated the integration of physiologically based pharmacokinetic modelling, global sensitivity analysis, Bayesian inference, and Markov chain Monte Carlo simulation to obtain a population estimate of inhalation exposure to m-xylene. We used exhaled breath and venous blood m-xylene and urinary 3-methylhippuric acid measurements from a controlled human volunteer study in order to evaluate the ability of our computational framework to predict known inhalation exposures. We also investigated the importance of model structure and dimensionality with respect to its ability to reconstruct exposure

Observation of gaseous and particulate products of monoterpene oxidation in forest atmospheres

Atmospheric oxidation of biogenic hydrocarbons, such as monoterpenes, is estimated to be a significant source of global aerosol. Whereas laboratory studies have established that photochemical oxidation of monoterpenes leads to aerosol formation, there are limited field studies detecting such oxidation products in ambient aerosols. Drawing on prior results of monoterpene product analysis under controlled smog chamber conditions, we have identified organic aerosol components attributable to monoterpene oxidation in two forest atmospheres, Kejimkujik National Park, Nova Scotia, Canada, and Big Bear, San Bernardino National Forest, California, U.S.A. The major identified aerosol products derived from α-pinene and β-pinene oxidation include pinic acid, pinonic acid, norpinonic acid and its isomers, hydroxy pinonaldehydes, and pinonaldehyde, concentrations of which in the aerosol phase are in the sub ng m^(−3) range. Identification of oxidation products in atmospheric aerosol samples serves as direct evidence for aerosol formation from monoterpenes under ambient conditions

Urinary biomarker concentrations of captan, chlormequat, chlorpyrifos and cypermethrin in UK adults and children living near agricultural land

There is limited information on the exposure to pesticides experienced by UK residents living near agricultural land. This study aimed to investigate their pesticide exposure in relation to spray events. Farmers treating crops with captan, chlormequat, chlorpyrifos or cypermethrin provided spray event information. Adults and children residing ≤100 m from sprayed fields provided first-morning void urine samples during and outwith the spray season. Selected samples (1–2 days after a spray event and at other times (background samples)) were analysed and creatinine adjusted. Generalised Linear Mixed Models were used to investigate if urinary biomarkers of these pesticides were elevated after spray events. The final data set for statistical analysis contained 1518 urine samples from 140 participants, consisting of 523 spray event and 995 background samples which were analysed for pesticide urinary biomarkers. For captan and cypermethrin, the proportion of values below the limit of detection was greater than 80%, with no difference between spray event and background samples. For chlormequat and chlorpyrifos, the geometric mean urinary biomarker concentrations following spray events were 15.4 μg/g creatinine and 2.5 μg/g creatinine, respectively, compared with 16.5 μg/g creatinine and 3.0 μg/g creatinine for background samples within the spraying season. Outwith the spraying season, concentrations for chlorpyrifos were the same as those within spraying season backgrounds, but for chlormequat, lower concentrations were observed outwith the spraying season (12.3 μg/g creatinine). Overall, we observed no evidence indicative of additional urinary pesticide biomarker excretion as a result of spray events, suggesting that sources other than local spraying are responsible for the relatively low urinary pesticide biomarkers detected in the study population