Uranium sequestration in sediment at an iron-rich contaminated site at Oak Ridge, Tennessee via. bioreduction followed by reoxidation

This study evaluated uranium sequestration performance in iron-rich(30 g/kg) sediment via bioreduction followed by reoxidation. Field tests(1383 days) at Oak Ridge, Tennessee demonstrated that uranium contents in sediments increased after bioreduced sediments were re-exposed to nitrate and oxygen in contaminated groundwater. Bioreduction of contaminated sediments(1200 mg/kg U) with ethanol in microcosm reduced aqueous U from 0.37 to 0.023 mg/L. Aliquots of the bioreduced sediment were reoxidized with O_2, H_2O_2,and NaNO_3, respectively, over 285 days, resulting in aqueous U of 0.024, 1.58 and 14.4 mg/L at pH 6.30, 6.63 and 7.62, respectively. The source-and the three reoxidized sediments showed different desorption and adsorption behaviors of U, but all fit a Freundlich model.The adsorption capacities increased sharply at pH 4.5 to 5.5, plateaued at pH 5.5 to 7.0, then decreased sharply as pH increased from 7.0 to 8.0. The O_2-reoxidized sediment retained a lower desorption efficiency at pH over 6.0. The NO_3~--reoxidized sediment exhibited higher adsorption capacity at pH 5.5 to 6.0. The pH-dependent adsorption onto Fe(Ⅲ) oxides and formation of U coated particles and precipitates resulted in U sequestration, and bioreduction followed by reoxidation can enhance the U sequestration in sediment.     

2000年来中国生态状况时空变化格局

21世纪以来,我国在经济快速发展的同时高度重视生态环境保护,一系列生态修复工程和空间管控措施使生态状况发生了巨大变化;然而目前对于全国生态状况宏观格局的认识仍十分有限。借助 Google Earth Engine（GEE）遥感云计算平台,采用主成分分析方法和MODIS数据构建的绿度NDVI、热度LST、湿度WET和干度NDSI四个指标,生成长时间序列的遥感生态指数RSEI数据集,完整刻画了中国2000年来生态状况的时空连续变化格局。研究发现:在空间格局上,东南沿海地区生态状况优于西北地区;变化趋势上,全国生态状况除上海、西藏和澳门之外均显著改善,RSEI增长最多的三个省份为山西、陕西和河北。进一步采用遥感云计算定量评价了2000年来生态状况变化的宏观格局,以期为国土空间管控和生态保护提供科学支持。     

RTO热力平衡核算及天然气消耗量影响因素分析

以某船舶涂装车间运行数据为依据,建立了蓄热式高温氧化炉（Regenerative Thermal Oxidizer,RTO）的热力平衡关系式,核算了RTO空载和满载运行的数据,验证了炉温与挥发性有机化合物（Volatile Organic Compounds,VOCs）浓度的关系;讨论了排风量、沸石转轮浓缩倍率、换热器热利用率和VOCs浓度四个关键参数对天然气消耗量的影响.结果显示,入炉VOCs浓度每增加1000mg/Nm³,炉温上升约21℃,排风量越小,沸石转轮浓缩倍率、换热器热利用率和VOCs浓度越大,天然气消耗量越低.基于本研究建立的热平衡方程,结合RTO实际工程应用中的注意事项,结果表明,在烘干阶段按照工艺要求的3次/h确定车间最小排风量,将沸石转轮浓缩倍率设定为10~14倍,选用换热器热利用率在0.7以上的换热器能在保证RTO安全运行的前提下显著降低天然气消耗量.     

Magnetic polyamidoamine dendrimers for magnetic separation and sensitive determination of organochlorine pesticides from water samples by high-performance liquid chromatography

Organochlorine pesticides (OCPs) have received much attention due to their toxicity. Reliable methods to monitor their residues in the environment are needed. Here, magnetic polyamidoamine dendrimers were prepared by co-precipitation, Michael addition, and amidation. The magnetic polyamidoamine dendrimers demonstrated good adsorption ability for OCPs—this feature was utilized to construct a sensitive tool for monitoring OCPs in water samples. The proposed method provided remarkable linearity from 0.1 to 500 μg/L and satisfactory limits of detection from 0.012 to 0.029 μg/L. The spiked recoveries of the four target analytes were 91.8%?103.5% with relative standard deviations less than 4.5%. The magnetic materials had good reusability. The results indicated that the resulting method was an efficient, easy, rapid, economical, and eco-friendly tool for monitoring OCPs in aqueous samples.     

Nano-selenium controlled cadmium accumulation and improved photosynthesis in indica rice cultivated in lead and cadmium combined paddy soils

Selenium nanoparticles (Se NPs) are less toxic and more biocompatible than selenite or selenate. However, studies involving spraying with Se NPs for reducing accumulation of cadmium (Cd) and lead (Pb) in rice grains have been rarely reported as yet. Herein, indica rice seedlings cultivated in Cd+Pb-spiked paddy soils (denoted as positive control) were sprayed with Se NPs sols for four times from tillering to booting stage. Compared to positive control, 50–100 μmol/L Se NPs downregulated Cd transporters-related genes such as OsLCT1, OsHMA2 and OsCCX2 in leaves and OsLCT1, OsPCR1 and OsCCX2 genes in node I at filling stage. Meanwhile, Se-binding protein 1 was distinctly elevated, involving the repression of Cd and Pb transportation to rice grains. Se NPs also differentially improved RuBP carboxylase and chlorophylls especially some key genes and proteins involving photosynthetic system. Besides, 25–50 μmol/L Se NPs diminished reactive oxygen species overproduction from NADPH oxidases whereas boosted glutathione peroxidase, reducing protein carbonylation in rice seedlings. However, the antioxidant isozymes and oxidatively modified proteins were slightly rebounded at 100 μmol/L. Se contents were noticeably elevated and confirmed to exist as selenomethionine in the rice grains following all the treatments by Se NPs. Thus, the optimal dosage of Se NPs for foliar application is 50 μmol/L, which significantly decreased Cd accumulation, improved photosynthesis and Se enrichment whereas caused no distinct reduction of Pb in the grains. Thus, an appropriate dosage of Se NPs can be conducted to decrease Cd accumulation, improve photosynthesis, and organic Se contents in rice grains.     

Enhanced adsorption for Pb(II) and Cd(II) of magnetic rice husk biochar by KMnO4 modification

Environmental Science and Pollution Research - Novel KMnO4-treated magnetic biochar (FMBC) was successfully synthesized by addition of Fe(NO3)3 during carbonization and KMnO4 treatment following...     

The effectiveness of travel restriction measures in alleviating the COVID-19 epidemic: evidence from Shenzhen,China

Environmental Geochemistry and Health - With the expansion of the global novel coronavirus disease (COVID-19) pandemic, unprecedented interventions have been widely implemented in many countries,...     

Methyl siloxanes in road dust from a large silicone manufacturing site in China: implications of human exposure

Environmental Science and Pollution Research - Methyl siloxanes are becoming increasingly prevalent in the environment because of their extensive use in various consumer products. Little is known...     

有毒气体扩散预测法在大气环境应急监测布点中的应用

利用有毒气体扩散预测方法在大气环境应急监测布点中的应用进行探索性研究。研究认为:有毒气体扩散的大气环境风险预测可以为大气环境污染事故应急监测布点提供所需的重要信息,能够很好地解决应急监测只能参照现有的监测规范和个人工作经验进行布点的问题,避免了监测人员的主观性,从而确保了应急监测的科学性、规范性、准确性和可靠性。