Organic geochemical (TOC, pyrolysis, biomarker) and petrographic (maceral analysis) investigations together with organic carbon isotope studies were carried out to characterize in detail the depositional environment, determine the organic matter type, and assess the hydrocarbon production potential of three coal seams (KP1-upper, KM3-middle, and KM2-lower) in the Soma (Manisa, Western Anatolia) coal field in Turkey. The total organic carbon value of the upper coal seam ranged between 11.7 and 55.75%, the middle coal seam between 20.12 and 62.86%, and the lower coal seam between 50.03 and 65.71%. Coals in all three seams are characterized by low hydrogen index (HI) values (<151 mg HC/g TOC), low bitumen index (BI) (<19 g HC/g TOC), and quality index (QI) between 23 and 156 mg HC/g TOC. According to Rock-Eval pyrolysis data, the organic matter type of the coals is type III kerogen. Huminite reflectance, Tmax, and biomarker data (22S/22S+22R (C₃₂) sterane, ββ/(αα + ββ) (C₂₉) sterane, and MPI-1) indicate that the organic matter is not thermally mature and that the Soma-Manisa coal has reached the sub-bituminous rank. Rock-Eval data shows that coal is gas-prone and has not reached the maturity threshold required for initial gas production. The dominant maceral group is huminite while liptinite and inertinite macerals have been found in minor amounts. Groundwater index (GWI), vegetation index (VI), tissue preservation index (TPI), and gelification index (GI) parameters indicate a transition from limnic-limno-telmatic to limno-telmatic-telmatic environment from the upper seam to the lower seam. N-Alkane distributions show that paleoclimatic conditions have changed from KP1 to KM2. The higher abundance of pristane compared to phytane and low C₃₅/C₃₁-C₃₅ homohopane index values demonstrate that the coals were deposited in a suboxic-oxic environment. The predominance of n-alkanes with generally high carbon number, relative variable abundances of C₂₇-C₂₈-C₂₉ steranes, δ¹³C values, C/N ratios, and very low gammacerane index indicate a terrestrial ecosystem with nonmarine influence, although algae and microorganisms also contributed to the biomass.

As industrial activities continue to expand, there is a growing demand for Rare Earth Elements (REEs). However, REE resources are rapidly depleting, leading to a search for alternative sources. Notably, REEs are found in significant quantities in coal, a fossil fuel with substantial global reserves and active extraction operations. Some countries, particularly China, extract REEs from coal, indicating its potential as an alternative REE source soon. The increasing number of academic research studies on this topic further underscores its importance. This study aims to analyze global academic research on REEs in coal and coal ash from 1973 to 2023 using bibliometric analysis to identify future trends. Data from the WoS database was utilized to ensure objective and comprehensive results. The research encompassed various aspects such as document type, country of origin, co-authors, institutions, citations, keywords, journals, and WoS categories. The findings suggest that coal could emerge as a significant REE source with sustainable and environmentally conscious practices, potentially forming a widespread business network.

In this study, geochemical behavior of elements is investigated in 25 coal samples collected at 10 locations of Şahinli coaliferous units at southeast of Aydın, Turkey. In all the samples, X-ray powder diffraction and inductively coupled plasma mass spectrometry analyses were performed and element and mineral compositions were determined. Total organic carbon (TOC) values of coals are between 14.6 and 37.7 wt% with average of 28.5 wt%. Samples are composed of quartz, calcite, feldspar, dolomite, mica, gypsum, and salt minerals which are accompanied by illite-, kaolinite-, and smectite-type clay minerals. Comparison of average element contents of world coals and studied samples yields that K > Fe > As > U > Cs > Y > Er > Al > Th > Rb > Yb > W > Tb > Dy > Lu > Ce > Sm > La > Ho > Si > Nd > Gd > Tm > Eu > Nb > Pr > Pb > Sn > Ni > Cu > Ga > Ta > Sb > Zr > Cd > V > Zn > Co > Mo > P > Hf > Ba are found to be enriched, while Mn > Be > Ca > Sr > Bi > Mg are found to be depleted. Statistically elements are correlated with TOC.

In this study, the radioactivity contents of Carboniferous Zonguldak-Kozlu hard coals, Carboniferous Antalya-Pamucakyayla hard coals and Pliocene Konya-Karapınar lignites were determined, then compared with the limit values determined by the authorized institutions and their hazard indexes were determined. The range of measured activity concentrations was from 16.2 Bq·kg ⁻¹ to 227.6 Bq·kg ⁻¹ for ²³⁸ U, 20.6 Bq·kg ⁻¹ to 67.5 Bq·kg ⁻¹ for ²³² Th and 211.9 Bq·kg ⁻¹ to 515.5 Bq·kg ⁻¹ for ⁴⁰ K. The calculated mean absorbed gamma dose rate ( D ), radium equivalent activity (Ra _eq ) and annual equivalent dose (AED) were 105.7 nGy·h ⁻¹ , 227.9 Bq·kg ⁻¹ and 129.6 μSv·h ⁻¹ , respectively. Although ²³⁸ U and ²³² Th radionuclide activity concentrations are comparable to literature values, ⁴⁰ K activity concentrations were around three or four times higher than in UNSCEAR (2000) reports. As it poses a radiological risk, it is necessary to take the necessary precautions to reduce the negative effects on the environment and human health due to use of coals from Konya-Karapınar, Antalya-Pamucakyayla basins and to burn in a controlled manner.