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Agricultural nonpoint-source pollution (ANPSP) is a key cause of global environmental problems. However, the estimation of ANPSP, based on agricultural land use type, crop management, and attenuation of pollutants with distance, is lacking. Using the Mun River Basin as an example, this study established quantitative response relationships between subbasin flows and hydrological and water quality parameters. A good matching of the monitored sections and the control area based on flow relationships was achieved. By determining flow paths and flow distances, the overland and in-river transport attenuations of ANPSP were clarified. The overland and in-river transport and attenuation parameters were also quantified. The land use distribution and structure were further refined through crop management, which included crop types and crop rotation (monocropping or double cropping). Based on the above procedures, quantitative relationships among land use pattern, crop management, attenuation of pollutants with distance, and river water quality were established and used to construct six kinds of regression models. Among these models, the best modeling results were obtained when the parameters of water quality, land use structure, crop management, and soil nutrient attenuation were included. The modeling accuracy in the dry season increased from 0.398 to 0.881 when information about attenuation with distance and crop management was included. Similarly, the modeling accuracy in the wet season increased from 0.365 to 0.727. This study's findings indicate that the constructed water quality model is effective and has significance for the quantitative determination of ANPSP. [ABSTRACT FROM AUTHOR]

Coal samples analyzed from Junggar Basin are characterized by high Total Organic Carbon (TOC) contents (63.7-82.2%) in all samples, except the highly over-mature samples Ha-01 and Ha-02, and high S2 (60.5-83.0 mg HC/g rock) and Hydrogen Index (HI) values (77-118 mg HC/g TOC), indicating the coal rocks have excellent source rock potential. The Tmax values (418-531°C), C29 sterane 20S/(20S+20R) ratios (0.20-0.54) and C31 homohopane 22S/(22S+22R) ratios (0.26-0.61) indicate an immature to highly over-mature stage of organic matter, which is supported by the organic geochemical maturation parameters. In addition, n-alkane carbon numbers range from C11 to C33 with maxima at n-C19 or n-C23, exhibiting unimodal distribution patterns except Ai-13 and Ha-01, and low Pr/Ph ratios (0.29-0.80) in Ai-01, Ai-13, Ha-01 and Ha-02, indicating a suboxic reductive environment. In Wu-8, Wei-09 and Shinan-20, the Pr/Ph ratios are clearly greater than 1.0 (2.43-3.23), indicating oxic depositional conditions. Furthermore, pristane isomers were identified in extracts from these coal samples. Using coals of different maturity, which correspond to vitrinite reflectances (%Ro) of 0.36-2.99%, the Pristane Isomerization Ratio (PIR) (PIR = [6(R)10(R)+6(S)10(S)]/6(R)10(S)) ranges from 0.42 to 0.97 for the coal extracts. The value of the PIR, which is a molecular maturity parameter, is evaluated by analyzing a series of samples using known values of the molecular maturity parameter based on the sterane and hopane isomerization indices, and the Methyl Phenanthrene Index (MPI). Changes to the PIR in highly mature Ai-13 (Ro > 1.5%) and over-mature Ha-01 and Ha-02 (Ro > 2.0%) are clear; thus, a linear correlation is evident between the PIR and Ro. The results suggest that the PIR is an appropriate indicator of maturity for the highly mature and over-mature coal samples in the Junggar Basin.

The abundant acyclic isoprene alkanes, including norpristane (2, 6, 10-tetramethyltetradecane), pristane (2, 6, 10, 14-tetramethylpentadecane), phytane (2, 6, 10, 14-tetramethylhexadecane) and their diastereomers, were detected and separated by GC-MS/MS in the coal sample of the Junggar Basin. Furthermore, the optimized condition of separation were discussed in terms of column type, length, and column temperature program. The results showed that the separation degree (R) of their diastereomers (i.e., 6(R)10(S)), 6(S)10(S) + 6(R)10(R)) of norpristane, pristane and phytane reached 0.6, 0.8 and 0.9, respectively. It indicated that the method was versatile, simple, rapid and efficient to separate the diastereomers of acyclic isoprene alkanes. [ABSTRACT FROM AUTHOR]