On the Water-Soluble Organic Matter in Inhalable Air Particles: Why Should Outdoor Experience Motivate Indoor Studies?

The current understanding of water-soluble organic aerosol (OA) composition, sources, transformations, and effects is still limited to outdoor scenarios. However, the OA is also an important component of particulate matter indoors, whose complexity impairs a full structural and molecular identification. The current limited knowledge on indoor OA, and particularly on its water-soluble organic matter (WSOM) fraction is the basis of this feature paper. Inspired by studies on outdoor OA, this paper discusses and prioritizes issues related to indoor water-soluble OA and their effects on human health, providing a basis for future research in the field. The following three main topics are addressed: (1) what is known about the origin, mass contribution, and health effects of WSOM in outdoor air particles; (2) the current state-of-the-art on the WSOM in indoor air particles, the main challenges and opportunities for its chemical characterization and cytotoxicity evaluation; and (3) why the aerosol WSOM should be considered in future indoor air quality studies. While challenging, studies on the WSOM fraction in air particles are highly necessary to fully understand its origin, fate, toxicity, and long-term risks indoors.

The Role of Soluble Organic Matter in Shale Oil “Sweet Spots” Prediction: An Investigation of Shale With Different Lithofacies in the Dongying Sag

Lithofacies are the fundamental geological units for shale oil and gas exploration and development, and soluble organic matter (SOM) is most similar to crude oil in composition. Both aspects attract our attention in the interpretation of SOM in different lithofacies, which can provide direct evidence to predict shale oil “sweet spots”. Here, twenty-five shale samples were collected from the Eocene Shahejie Formation in the Dongying Sag and were subjected to X-ray diffraction, Rock-Eval pyrolysis, and SOM characterization. Comparison of the SOM contents in shales with different lithofacies revealed remarkable differences: 1) The contents of SOM, saturates and total hydrocarbons (THC) showed the order of detrital massive mudstone < homogenous massive mudstone < wide laminated shale < discontinuous laminated shale < fine laminated shale < gypsum-bearing mudstone, and the SOM content was controlled by lithofacies through differences in both OM and minerals. 2) The SOM in detrital and homogenous massive mudstones was mainly composed of saturates and resins. Saturates were the main component in wide and fine laminated shales. The SOM in discontinuous laminated shale was mainly composed of saturates and aromatics. The SOM in gypsum-bearing mudstone was mainly composed of saturates, and the percentage of asphaltenes was quite high. Based on the evaluation parameters of high-quality lithofacies in terms of abundance (i.e., SOM, THC or saturate contents) and quality (i.e., quality index and asphaltene percentage), the fine, wide and discontinuous laminated shales were regarded as relatively favorable lithofacies. Based on the lithofacies combination, the fine, wide and discontinuous laminated shales in Es3x and Es4ss (upper section of Es4s) in the Dongying Sag were interpreted as “sweet spots” for shale oil exploration and development. Thus, it is of great significance to study the characteristics of SOM in shale with different lithofacies for shale oil exploration and development.

Characteristics and Geological Significance of the Hydrocarbon Source Rocks of the Qum Formation in Outcrop of the Northern Garmsar Area, Iran

The carbonate rocks were collected from the Qum Formation in outcrop of the northern Garmsar Area, Iran. In order to evaluating the hydrocarbon generation prospects of these source rocks, we analyzed their geochemical characteristics, including the abundance, type, and maturity of organic matter, and investigated their formation conditions by analyzing the characteristics of soluble organic matter and sedimentary environment. The results show that the organic matter abundance of the source rocks in the Qum Formation in the Garmsar Area is low in the north and west. The organic matter type is mainly II1-II2, locally showing type I and III, and in general, it is conducive to hydrocarbon generation. The maturity of organic matter is low, showing the Tmax between 416°C and 439°C, vitrinite reflectance (Ro) from 0.49% to 0.83%, which indicate it is at the stage of low to moderate maturity. The soluble organic matter characteristics indicated that the organic matter evolution of the source rocks in the Qum Formation is low. Through comparison between the study area and other areas, and different places within the working area, the abundance, type, and maturity of organic matter of the source rocks in the Qum Formation are different, caused by the basin facie zones, sedimentary environment, and history of sedimentation of the source rocks. Overall, the source rock in the Qum Formation in Garmsar Area has good prospects of hydrocarbon generation. This study has important significance for further exploration in the Garmsar Area.