Geochemistry and hydrocarbon source rock potential of shales from the Palaeo-Mesoproterozoic Vindhyan Supergroup, central India

With increase in shale gas exploration, inorganic and organic geochemical investigations of shale have become extremely important. Here, we explore the six argillaceous (shale) intervals (Arangi, Koldaha, Rampur, Bijaygarh, Rewa and Sirbu shale) from Son valley sector, Vindhyan Basin with an aim to understand provenance conditions, palaeoclimate, tectonic setting and hydrocarbon generation potential. Whole rock geochemistry indicates Vindhyan sediments derived from felsic source(s) except for Sirbu shale that indicates additional influx of mafic rocks with differentiated felsic source. A comparative study of Vindhyan shale rare earth elements (REEs) points to Mahakoshals and Chhotanagpur gneissic complex (CGC) as probable sediment provenance for Vindhyan sediments. CIA analysis, after necessary corrections for K-metasomatism, suggests evolution in weathering and palaeoclimate indicating a transformation from moderate weathering conditions with warm and humid climate during lower Vindhyan deposition to intense weathering conditions with hot and humid climate during upper Vindhyan deposition. Trace (La/Y vs. Sc/Cr) and REE analysis indicates passive margin setting for Vindhyan sediments whereas a wide range spanning passive to active continental margin setting is also inferred using (Th-Sc-Zr/10) and (Th–La-Sc) ternary diagrams. However, these tectonic discriminant diagrams lack in explaining rift- or sag-related origin of any intracratonic basin such as the Vindhyan Basin. The total organic carbon (TOC) content in Vindhyan shales ranges from 0.29% to 8.44%. The thermally liberated hydrocarbon (S1) values range from 0.01 to 0.18 mg HC/g rock (milligram hydrocarbon per gram of rock sample), whereas hydrocarbon from cracking of the kerogen (S2) shows values ranging from 0.04 to 0.47 mg HC/g rock. Based on modified Van Krevelen correlation (HI vs. Tmax) diagram, organic matter from Arangi and Bijaygarh shales is characterized as thermally mature, Type III kerogen of gas prone character indicating good to very good gas generation potential.

Historical record of effects of human activities on absolute and relative concentrations of Polycyclic aromatic hydrocarbons(PAHs) in Lake Chao,China

Polycyclic aromatic hydrocarbons（PAHs）are attracting concern because of their potential toxicity,posing serious threats to health of humans and ecosystems（Kim et al.,2013;Zhao et al.,2016）.Generally,similar to other contaminants＇behaviors（Wu et al.,2001;Zhang et al.,2007,2008;Lu et al.,2009）,PAHs result from natural organic matter and activities of humans,the latter＇s contribution usually outweighing the inputs from other sources（Fernández et al.,2000;Srogi,2007）.

Characterizations of organic compounds in diesel exhaust particulates

To characterize how the speed and load of a medium-duty diesel engine affected the organic compounds in diesel particle matter（PM） below 1 μm, four driving conditions were examined. At all four driving conditions, concentration of identifiable organic compounds in PM ultrafine（34–94 nm） and accumulation（94–1000 nm） modes ranged from 2.9 to 5.7 μg/m3 and 9.5 to 16.4 μg/m3, respectively. As a function of driving conditions, the non-oxygencontaining organics exhibited a reversed concentration trend to the oxygen-containing organics. The identified organic compounds were classified into eleven classes： alkanes,alkenes, alkynes, aromatic hydrocarbons, carboxylic acids, esters, ketones, alcohols, ethers,nitrogen-containing compounds, and sulfur-containing compounds. At all driving conditions,alkane class consistently showed the highest concentration（8.3 to 18.0 μg/m3） followed by carboxylic acid, esters, ketones and alcohols. Twelve polycyclic aromatic hydrocarbons（PAHs）were identified with a total concentration ranging from 37.9 to 174.8 ng/m3. In addition, nine nitrogen-containing polycyclic aromatic compounds（NPACs） were identified with a total concentration ranging from 7.0 to 10.3 ng/m3. The most abundant PAH（phenanthrene）and NPACs（7,8-benzoquinoline and 3-nitrophenanthrene） comprise a similar molecular（3 aromatic-ring） structure under the highest engine speed and engine load.

Chemical characteristics of PM_(2.5) during haze episodes in the urban of Fuzhou,China

Atmospheric fine particles （PM2.5） were collected in this study with middle volume samplers in Fuzhou, China, during both normal days and haze days in summer （September 2007） and winter （january 2008）. The concentrations, distributions, and sources of polycyclic aromatic hydrocarbons （PAHs）, organic carbon （OC）, elemental carbon （EC）, and water soluble inorganic ions （WSIls） were determinated. The results showed that the concentrations of PM2.s, PAHs, OC, EC, and WSIIs were in the orders of haze 〉 normal and winter〉 summer. The dominant PAHs of PM2.s in Fuzhou were Fluo, Pyr, Chr, BbF, BkF, BaP, BghiP, and IcdP, which represented about 80.0% of the total PAHs during different sampling periods. The BaPeq concentrations of ^-~PAHs were 0.78, 0.99, 1.22, and 2.43 ng/m3 in summer normal, summer haze, winter normal, and winter haze, respectively. Secondary pollutants （SO42 , NO3 , NH4＊, and OC） were the major chemical compositions of PM2.5, accounting for 69.0%, 55.1%, 63.4%, and 64.9% of PM2.s mass in summer normal, summer haze, winter normal, and winter haze, respectively. Correspondingly, secondary organic carbon （SOC） in Fuzhou accounted for 20.1%, 48.6%, 24.5%, and 50.5% of OC. The average values of nitrogen oxidation ratio （NOR） and sulfur oxidation ratio （SOR） were higher in haze days （0.08 and 0.27） than in normal days （0.05 and 0.22）. Higher OC/EC ratios were also found in haze days （5.0） than in normal days （3.3）. Correlation analysis demonstrated that visibility had positive correlations with wind speed, and neg- ative correlations with relative humidity and major air pollutants. Overall, the enrichments of PM2.5, OC, EC, SO42 ,andNO3 promoted haze formation. Furthermore, the diagnostic ratios of IcdP/（IcdP ＋ BghiP）, lcdP/BghiP, OC/EC, and NO3 /SO42 indicated that vehicle exhaust and coal consumption were the main sources of pollutants in Fuzhou.

On-board measurements of gaseous pollutant emission characteristics under real driving conditions from light-duty diesel vehicles in Chinese cities

A total of 15 light-duty diesel vehicles（LDDVs） were tested with the goal of understanding the emission factors of real-world vehicles by conducting on-board emission measurements. The emission characteristics of hydrocarbons（HC） and nitrogen oxides（NOx） at different speeds, chemical species profiles and ozone formation potential（OFP） of volatile organic compounds（VOCs） emitted from diesel vehicles with different emission standards were analyzed. The results demonstrated that emission reductions of HC and NOxhad been achieved as the control technology became more rigorous from Stage I to Stage IV. It was also found that the HC and NOxemissions and percentage of O2 dropped with the increase of speed, while the percentage of CO2 increased. The abundance of alkanes was significantly higher in diesel vehicle emissions, approximately accounting for 41.1%–45.2%, followed by aromatics and alkenes. The most abundant species were propene,ethane, n-decane, n-undecane, and n-dodecane. The maximum incremental reactivity（MIR）method was adopted to evaluate the contributions of individual VOCs to OFP. The results indicated that the largest contributors to O3 production were alkenes and aromatics, which accounted for 87.7%–91.5%. Propene, ethene, 1,2,4-trimethylbenzene, 1-butene, and1,2,3-trimethylbenzene were the top five VOC species based on their OFP, and accounted for 54.0%-64.8% of the total OFP. The threshold dilution factor was applied to analyze the possibility of VOC stench pollution. The majority of stench components emitted from vehicle exhaust were aromatics, especially p-diethylbenzene, propylbenzene, m-ethyltoluene, and p-ethyltoluene.