Ce-promoted Mn/ZSM-5 catalysts for highly efficient decomposition of ozone

Manganese oxides supported by ZSM-5 zeolite (Mn/ZSM-5) as well as their further modified by Ce promoter were achieved by simple impregnation method for ozone catalytic decomposition. The yCe20Mn/ZSM-5–81 catalyst with 8% Ce loading showed the highest catalytic activity at relative humidity of 50% and a space velocity of 360 L/(g × hr), giving 93% conversion of 600 ppm O₃ after 5 hr. Moreover, this sample still maintained highly activity and stability in humid air with 50%–70% relative humidity. Series of physicochemical characterization including X-ray diffraction, temperature-programmed technology (NH₃-TPD and H₂-TPR), X-ray photoelectron spectroscopy and oxygen isotopic exchange were introduced to disclose the structure-performance relationship. The results indicated that moderate Si/Al ratio (81) of zeolite support was beneficial for ozone decomposition owing to the synergies of acidity and hydrophobicity. Furthermore, compared with 20Mn/ZSM-5-81, Ce doping could enhance the amount of low valance manganese (such as Mn²⁺ and Mn³⁺). Besides, the Ce³⁺/Ce⁴⁺ ratio of 8Ce20Mn/ZSM-5-81 sample was higher than that of 4Ce20Mn/ZSM-5-81. Additionally, the synergy between the MnO_x and CeO₂ could easily transfer electron via the redox cycle, thus resulting in an increased reducibility at low temperatures and high concentration of surface oxygen. This study provides important insights to the utilization of porous zeolite with high surface area to disperse active component of manganese for ozone decomposition.     

Functional traits of poplar leaves and fine roots responses to ozone pollution under soil nitrogen addition

Concurrent ground-level ozone（O₃） pollution and anthropogenic nitrogen（N） deposition can markedly influence dynamics and productivity in forests.Most studies evaluating the functional traits responses of rapid-turnover organs to O₃ have specifically examined leaves,despite fine roots are another major source of soil carbon and nutrient input in forest ecosystems.How elevated O₃ levels impact fine root biomass and biochemistry remains to be resolved.This study was...     

伯克氏菌对水稻种子萌发及初生幼苗耐镉性的影响

在无菌条件下研究了伯克氏菌对镉胁迫下水稻种子萌发及初生幼苗耐镉性的影响。结果表明：伯克氏菌D54能在含500mg·L^-1Cd的培养基中正常生长,显示出极强的耐镉能力。在50 mg·L^-1的镉胁迫下,接种伯克氏菌能显著提高水稻种子的萌发率,但在其他镉处理下,接种伯克氏菌对种子萌发无显著影响。接种伯克氏菌对水稻种子的发芽指数没有影响,但在10 mg·L^-1Cd处理下,接种伯克氏菌能显著提高水稻种子的活力指数和初生幼苗的根长、根表面积、根尖总数和耐性系数。接种伯克氏菌对初生幼苗的芽鲜重无影响,但能显著提高根鲜重。在50 mg·L^-1和100 mg·L^-1的高浓度镉处理下,接种伯克氏菌对根系生长没有影响。     

Awareness of zero tolerance laws in three states

PROBLEM: A prior study indicated that zero tolerance laws differ in their enforceability and likelihood of enforcement, with California's law being easier to enforce than New York's, and New Mexico's being the hardest of all. The question is, do these differences in enforcement affect teenagers' knowledge and perception of these laws? METHOD: A telephone survey was conducted to investigate awareness of the laws among 17-20 year olds in these three states and perceptions of enforcement. RESULTS: Estimated percentages of teenagers who knew of the laws were much higher in New York and California (71% and 65%, respectively) than in New Mexico (34%). Perceptions that police were enforcing the law, that licenses could be suspended, and that penalties were often applied were also lowest in New Mexico. IMPACT ON INDUSTRY: The potential of zero tolerance laws will not be realized without better awareness among young people. Full enforcement of the laws accompanied by publicity about the enforcement is recommended. Changes to the laws and their application may encourage enforcement efforts.     

德国的臭氧监控及其对成都市的借鉴

环境空气中臭氧含量问题越来越多为人们所重视,本文拟就臭氧的形成与危害,臭氧监测在德国的开展情况作一介绍,并对其在成都市的借签应用提出建议措施。     

无菌水葫芦的降酚和耐酚性能的研究

干重为0.2～0.3g的无菌水葫芦在各种酚浓度中(10、100、150、200、360、800μg/ml)的5日降解率可达20％～40％,即使在高浓度中植株很快死亡,但仍有降解能力;一定时间内的吸酚量随初始浓度不同而不同,有一定正相关;干重为0.2～0.3g的无菌水葫芦耐酚阈值为100～150μg/ml,高出此浓度植株很快死亡。     

Accumulation of Hg(II) by microbial biofilms on suspended particulate matter

Accumulation of Hg(II) by microbial biofilms on suspended particulate matter     

Impacts of meteorology and precursor emission change on O3 variation in Tianjin, China from 2015 to 2021

Deterioration of surface ozone (O₃) pollution in Northern China over the past few years received much attention. For many cities, it is still under debate whether the trend of surface O₃ variation is driven by meteorology or the change in precursors emissions. In this work, a time series decomposition method (Seasonal-Trend decomposition procedure based on Loess (STL)) and random forest (RF) algorithm were utilized to quantify the meteorological impacts on the recorded O₃ trend and identify the key meteorological factors affecting O₃ pollution in Tianjin, the biggest coastal port city in Northern China. After “removing” the meteorological fluctuations from the observed O₃ time series, we found that variation of O₃ in Tianjin was largely driven by the changes in precursors emissions. The meteorology was unfavorable for O₃ pollution in period of 2015-2016, and turned out to be favorable during 2017-2021. Specifically, meteorology contributed 9.3 µg/m³ O₃ (13%) in 2019, together with the increase in precursors emissions, making 2019 to be the worst year of O₃ pollution since 2015. Since then, the favorable effects of meteorology on O₃ pollution tended to be weaker. Temperature was the most important factor affecting O₃ level, followed by air humidity in O₃ pollution season. In the midday of summer days, O₃ pollution frequently exceeded the standard level (>160 µg/m³) at a combined condition with relative humidity in 40%-50% and temperature > 31°C. Both the temperature and the dryness of the atmosphere need to be subtly considered for summer O₃ forecasting.     

外秦淮河生态护坡挺水植物适应性试验研究

针对外秦淮河的污染状况,采用挺水植物菖蒲和狭叶香蒲进行试验,对外秦淮河的污染水质进行净化;同时进行两种挺水植物在外秦淮河当前水质下的耐淹没性试验.通过试验研究得出,在深秋季节,虽然菖蒲和狭叶香蒲两种植物已经处于生长周期的最后阶段,但是对外秦淮河污染水质仍然有较好的净化效果,对TP、TN、氨氮等的去除率能达到80%以上,对CODMn的去除率偏低.而且通过净化和耐淹试验中两种植物的对比,菖蒲比狭叶香蒲更能适应外秦淮河的水质状况.     

UV-US-O3联用处理高浓度有机废水的研究

本研究利用UV-US-O3联用处理废水.结果表明,UV-US-O3联用的处理效果大大高于单一紫外、单一臭氧及单一超声波处理的去除效率之和,UV-US-O3联用具有极好的协同效应.另外,本研究还考察了pH值、臭氧流量、超声波声能密度、处理时间的变化对处理效果的影响.