Study on comprehensive evaluation of environmental pollution treatment effect in coal mine subsidence area: taking Xinglongzhuang mining area of Yanzhou energy as an example.

In order to explore the effective evaluation method of environmental pollution treatment effect in China's coal mine subsidence areas, based on the literature review and analysis of current situation, combined with the reality of environmental pollution treatment (EPT) in China's coal mine subsidence areas, this paper selected four categories, including a total of 21 evaluation indicators, and drew lessons from the latest research results in relevant fields to construct the spatial niche suitability model of comprehensive evaluation of environmental pollution treatment effect in coal mine subsidence area. Taking the collapse area of Xinglongzhuang coal mine of Yanzhou energy as an example, the comprehensive evaluation and application of environmental pollution treatment effect in coal mine subsidence area were studied. It is found that the environmental pollution treatment effect of the mining area has increased from moderate pollution (level III) in 2012 to mild pollution (level I) in 2020 within 9 years. The environmental pollution treatment effect has a rapid improvement relatively, but its growth rate has decreased year by year since 2016, and the environmental pollution indicator is still at a high level. Therefore, environmental pollution treatment in the subsidence area is still a long-term task of Dongtan coal mine. The research results of this paper provide an effective quantitative analysis method for the evaluation of environmental pollution treatment effect in coal mine subsidence area, which is conducive to the continuous improvement of environmental pollution treatment effect in mining area.

Simple and cost-effective methods for precise analysis of trace element abundances in geological materials with ICP-MS.

Inductively coupled plasma mass spectrometry (ICP-MS) is the most commonly used technique to determine the abundances of trace elements in a wide range of geological materials. However, incomplete sample digestion, isobaric interferences and instrumental drift remain obvious problems that must be overcome in order to obtain precise and accurate results. For this reason, we have done many experiments and developed a set of simple, cost-effective and practical methods widely applicable for precise and rapid determination of trace element abundances in geological materials using ICP-MS. Commonly used high-pressure digestion technique is indeed effective in decomposing refractory phases, but this inevitably produces fluoride complexes that create new problems. We demonstrate that the fluoride complexes formed during high-pressure digestion can be readily re-dissolved using high-pressure vessel at 190°C for only 2h for 50mg sample. In the case of isobaric interferences, although oxide (e.g., MO+/M+) and hydroxide (e.g., MOH+/M+) productivity is variable between runs, the (MO+/M+)/(CeO+/Ce+) and (MOH+/M+)/(CeO+/Ce+) ratios remain constant, making isobaric interference correction for all other elements of interest straightforward, for which we provide an easy-to-use off-line procedure. We also show that mass-time-intensity drift curve is smooth as recognized previously, for which the correction can be readily done by analyzing a quality-control (QC) solution and using off-line Excel VBA procedure without internal standards. With these methods, we can produce data in reasonable agreement with recommended values of international rock reference standards with a relative error of <8% and precision generally better than 5%. Importantly, compared to the widely used analytical practice, we can effectively save >60% of time (e.g., <24h vs. >60h).

Efficient hydrolysis of corncob residue through cellulolytic enzymes from Trichoderma strain G26 and L-lactic acid preparation with the hydrolysate.

To prepare fermentable hydrolysate from corncob residue (CCR), Trichoderma strain G26 was cultured on medium containing CCR for production of cellulolytic enzymes through solid-state fermentation (SSF), resulting in 71.3 IU/g (FPA), 136.2 IU/g (CMCase), 85.1 IU/g (ß-glucosidase) and 11,344 IU/g (xylanase), respectively. Through a three-stage saccharification strategy, CCR was hydrolyzed by the enzymatic solution (6.5 FPU/ml) into fermentable hydrolysate containing 60.1g/l glucose (81.2% cellulose was converted at solid loading of 12.5%), 21.4% higher than that by the one-stage method. And then the hydrolysate was used to produce L-lactic acid by a previous screened strain Bacillus coagulans ZX25 in the submerged fermentation. 52.0 g/l L-lactic acid was obtained after fermentation for 44 h, with 86.5% glucose being converted to L-lactic acid. The results indicate that the strains and the hydrolysis strategy are promising for commercial production of L-lactic acid from CCR and other biomass.