Occurrence,fate, and transport of potentially toxic metals (PTMs) in an alkaline rhizosphere soil-plant (Maize,Zea mays L.) system: the role of Bacillus subtilis

Environmental Science and Pollution Research - Utilization of microbes is one of the most promising methods to remediate potentially toxic metals (PTMs) from soil. In this study, a systematic...     

基于STIRPAT模型的黑龙江省碳排放影响因素研究

2005年以来,黑龙江省社会经济持续稳步发展,截至2017年,全省GDP达到15903亿元,增长近3倍,人均GDP增长2.89倍,城镇化率达到60%,第三产业占全省生产总值比重达到55.82%。与此同时,全省碳排放量从19095万吨增加到27251万吨,增长1.43倍。通过对黑龙江省13年间社会经济数据的系统分析研判,人均GDP、城镇化率、碳排放强度等因素对全省碳排放量影响显著。     

对于土地使用权升值问题的探讨

基于经济和社会等方面的原因,土地所有权的价格一般会不断上涨,固定年期土地使用权价格也会随之上升。但受让土地使用权价格存在类似折旧的现象。投资人能否从地价普遍上涨中获得增值收益,取决于土地所有权增值比率、土地还原利率、剩余使用年期等多种因素。     

A DFT study on the carbamates formation through the absorption of CO2 by AMP

DFT calculations in gas and aqueous solution phases have been performed to study the mechanism of carbamate formation by the absorption of CO₂ in 2-amino-2-methyl-1-propanol (AMP). The results reveal the importance of considering the effect of water as solvent for the reaction to proceed. Furthermore water molecules play an important role as a basic reactant leading to stable intermediates formation. These results point at a single-step, third order reaction as the most probable mechanism for the formation of carbamate by the absorption process.     

An evaluation of improvements in the air quality of Beijing arising from the use of new vehicle emission standards

An innovative approach of mean emission by vehicle type was used in this paper to assess the impact of new vehicle emission standards in Beijing, China during the period of 2000–2005. It was found that CO and NO_x emissions decreased by 48% and 23%, respectively, from Type O (before 2000) to Type I (year 2000) vehicles. The reductions from Type O to Type II (year 2002) vehicles were 85% and 73% for CO and NO_x, respectively. When all three types of vehicles (Types O, I and II) are combined, the annual per vehicle CO emissions decreased from 586 kg per vehicle per year in 2000 to 324 kg per vehicle per year in 2005, while that of NO_x decreased from 66.9 to 43.4 kg per vehicle per year, which was mainly resulted from the impact of stringent new vehicle emission standards implemented in years 2000 and 2002. However, the vehicle population increased by 70% during the same time period, which offset the impact of cleaner vehicles. Thus, the total vehicle emission decreased little for CO (885,000 tons in 2000, 837,000 tons in 2005) and even increased slightly for NO_x (101,000 and 112,000 tons in 2000 and 2005, respectively). The ambient concentrations of CO decreased significantly throughout 2000–2005, the same trend was not observed for NO₂. Correlation analysis (grey correlation and Pearson correlation) between the annual vehicle emissions and annual concentrations of CO, the annual NO_x emission and annual NO₂ concentration indicated that the implementation of new vehicle emission standards was associated with the abatement of ambient CO and NO₂ concentrations in Beijing.     

气相色谱法测定环境空气中氯化苄和甲苯

用串联的乙醇吸收管收集环境空气中的氯化苄和甲苯,以毛细管柱分离,氢火焰检测器测定,保留时间定性,峰高定量。氯化苄平均浓度在４．２９ｍｇ／Ｌ～２１．４ｍｇ／Ｌ时,相对标准偏差在３．３％～４．６％之间;甲苯平均浓度为４．１８ｍｇ／Ｌ～２０．６ｍｇ／Ｌ时,相对标准差在４．４％～７．８％范围内。方法快速、灵敏度高,有较好的精密度与准确度。     

南通平原河网地区典型农田系统地下水硝态氮污染调查

针对平原河网地区典型农田系统灌溉施肥带来的地下水环境污染问题,采集南通地区蔬菜地、水稻-小麦轮作地、水稻-油菜轮作地和桑地地下水样品,分析了不同农田种植体系下的地下水污染程度。结果表明,蔬菜、桑地、水稻-油菜轮作、水稻-小麦轮作地地下水的硝态氮(N)平均值分别为12.2,9.53,7.95和6.12 mg/L,与氮肥用量呈显著的正相关关系;研究区域地下水硝态氮超Ⅲ类标准率(20 mg/L)的为4.8%,表明地下水已部分受到硝态氮污染。     

Simultaneous determination of organophosphorus and organonitrogen pesticides residues in Angelica sinensis

Gas chromatography with nitrogen phosphorus detector (GC-NPD) was applied to the simultaneous determination of 15 organophosphorus and 6 organonitrogen pesticides residues in Angelica sinensis. The pesticides were extracted by microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) techniques, respectively. The experimental variables were optimized through orthogonal array experimental design. Cleanup of extracts was performed with column chromatography using florisil and neutral aluminum as the sorbents. The determination of pesticides in the final extracts was carried out by GC-NPD. Under optimized conditions, the average recoveries obtained from MAE and UAE are in the range of 75.1–129% and 70.6–129%, respectively, and the relative standard deviations of MAE and UAE were 3.1–10.6% and 1.0–17.8%, respectively.     

Geofractionation of heavy metals and application of indices for pollution prediction in paddy field soil of Tumpat, Malaysia

The present study investigates the concentration of Pb, Cd, Ni, Zn, and Cu in the paddy field soils collected from Tumpat, Kelantan. Soil samples were treated with sequential extraction to distinguish the anthropogenic and lithogenic origin of Pb, Cd, Ni, Zn, and Cu. ELFE and oxidizable-organic fractions were detected as the lowest accumulation of Pb, Cd, Ni, Zn, and Cu. Therefore, all the heavy metals examined were concentrated, particularly in resistant fraction, indicating that those heavy metals occurred and accumulated in an unavailable form. The utilization of agrochemical fertilizers and pesticides might not elevate the levels of heavy metals in the paddy field soils. In comparison, the enrichment factor and geoaccumulation index for Pb, Cd, Ni, Zn, and Cu suggest that these heavy metals have the potential to cause environmental risk, although they present abundance in resistant fraction. Therefore, a complete study should be conducted based on the paddy cycle, which in turn could provide a clear picture of heavy metals distribution in the paddy field soils.     

Synthesis of α-Fe2O3 nanofibers for applications in removal and recovery of Cr(VI) from wastewater

Purpose

Nanomaterials such as iron oxides and ferrites have been intensively investigated for water treatment and environmental remediation applications. The purpose of this work is to synthesize α-Fe₂O₃ nanofibers for potential applications in removal and recovery of noxious Cr(VI) from wastewater.

Methods

α-Fe₂O₃ nanofibers were synthesized via a simple hydrothermal route followed by calcination. The crystallographic structure and the morphology of the as-prepared α-Fe₂O₃ nanofibers were characterized by X-ray diffraction, scanning electron microscope, and transmission electron microscope. Batch adsorption experiments were conducted, and Fourier transform infrared spectra were recorded before and after adsorption to investigate the Cr(VI) removal performance and adsorption mechanism. Langmuir and Freundlich modes were employed to analyze the adsorption behavior of Cr(VI) on the α-Fe₂O₃ nanofibers.

Results

Very thin and porous α-Fe₂O₃ nanofibers have been successfully synthesized for investigation of Cr(VI) removal capability from synthetic wastewater. Batch experiments revealed that the as-prepared α-Fe₂O₃ nanofibers exhibited excellent Cr(VI) removal performance with a maximum adsorption capacity of 16.17 mg g^?1. Furthermore, the adsorption capacity almost kept unchanged after recycling and reusing. The Cr(VI) adsorption process was found to follow the pseudo-second-order kinetics model, and the corresponding thermodynamic parameters ΔG°, ΔH°, and ΔS° at 298 K were calculated to be ?26.60 kJ?mol^?1, ?3.32 kJ?mol^?1, and 78.12 J?mol^?1 K^?1, respectively.

Conclusions

The as-prepared α-Fe₂O₃ nanofibers can be utilized as efficient low-cost nano-absorbents for removal and recovery of Cr(VI) from wastewater.