For instance, based on the analysis of modes of trace-element (including yttrium and rare earth) and mineral occurrence, Dai et al. (2014a) revealed the dominant sediment-source regions for the late Permian coal-bearing strata of the Huayingshan coalfield, eastern Sichuan, southwestern China, are the Dabashan and Leshan-Longnvsi Uplifts and the Hannan Upland.
Patient referral is the mode of tracing contacts in the Netherlands, but anonymous, web-based, partner notification via the programme was also possible.
The modes of occurrence of trace elements present in these coals have been determined through statistical approach.
The modes of occurrence of trace elements were discussed by correlation analysis and the inferred concentrations of trace elements in organic matters and minerals were then calculated based on linear regression.
Yang determined abundances and modes of occurrence of trace elements in the Late Permian coals in the Puan Coalfield, Guizhou, China, and found that the silicate-associated fraction of Se was about 3.81% of the total[38].
The concentrations, distribution and modes of occurrence of trace elements in coal is mainly influenced by geological factors like depositional environment and other physical and biogeochemical factors during its formation (Hower et al. 2007; Li et al. 2016).
Yang studied the abundances and modes of occurrence of trace elements in the Late Permian coals in the Puan Coalfield, Guizhou, China, and found that the water-soluble Se fraction was about 0.03%[38].
However very few data on the modes of occurrence of trace elements are available in the West Bokaro coalfield, which is one of biggest Gondwana coalfields based on its areal extent, number and thickness of coal seams and reserves of coking coals (Pareek and Bardhan 1985).
Such traits include primary vascular system, type of secondary xylem, pit distribution on secondary xylem tracheid walls, and mode of leaf trace production.
