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The characterization of the concentration, chemical speciation and source of heavy metals in soils is an imperative for pollution monitoring and the potential risk assessment of the metals to animal and human health. A total of 154 surface horizons and 53 underlying horizons of grassland soil were collected from the Baicheng–Songyuan area in Jilin Province, Northeast China, in which the concentrations and chemical fractionations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn were investigated. The mean concentrations of heavy metals in grassland topsoil were 7.2, 0.072, 35, 16.7, 0.014, 15.2, 18.3 and 35 mg kg − 1 for As, Cd, Cr, Cu, Hg, Ni, Pb and Zn, respectively, and those averaged contents were lower than their China Environmental Quality Standard values for the Soils, implying that heavy metal concentrations in the studied soils were of the safety levels. The mobility sequence of the heavy metals based on the sum of the soluble, exchangeable, carbonate-bound and humic acid-bound fractions among the seven fractions decreased in the order of Cd 50.4%) > Hg (39.8%) > Cu (26.5%) > As (19.9%) > Zn (19.1%) > Ni (15.9%) > Pb (14.1%) > Cr (4.3%), suggesting Cd and Hg may pose more potential risk of soil contamination than other metals. Multivariate statistical analysis suggested that As, Cr, Cu, Ni, Pb, Zn, Cd and Hg had the similar lithogenic sources, however, Cd and Hg were more relevant to organic matter than other heavy metals, which was confirmed by the chemical speciation analysis of the metals. The study provides a base for local authority in the studied area to monitor the long term accession of heavy metals into grassland soil. [ABSTRACT FROM AUTHOR]

It is useful in the clarifications of pore spaces at different scales in reservoir evaluations, and also helpful to exploit shale oil resources. The analysis of pores and fractures can be used to evaluate the reconstruction effects of pyrolysis in reservoirs. The existing analysis methods mainly adopt single scale data to study pores of certain sizes, which does not fully reflect the pore structures of oil shale. In this study, experiments regarding gas adsorption, SEM, MICP, NMR, and CT were conducted for the purpose of evaluating the effects of pyrolysis on the oil shale from the Wangqing. It was proposed to divide the pore spaces (0.1–106 nm) into seven levels for comparison purposes according to the order of magnitude, and then to evaluate the applicability of each method. The pyrolysis was observed to have caused the porosity of oil shale to markedly increase, and the sizes of the pores were found to change from mainly nano to co-developed micro-nano pores. The results indicated that a single pore detection method has its limitations since it is difficult to obtain multi-scale pore information. In order to understand the pore structures of oil shale, it is necessary to integrate multiple methods. • The pore structure of multi-scale oil shale is analyzed comprehensively. • The influence of pyrolysis on the pore structure of oil shale was evaluated. • The application effect of different measurement methods to oil shale is compared. [ABSTRACT FROM AUTHOR]