中晚全新世六盘山流域土壤侵蚀的湖泊沉积记录

流域土壤侵蚀是流域水文—气候—生态的集中表现之一,对生态、环境等有着重大影响,重建过去流域土壤侵蚀强度对理解区域人类活动具有重要意义.本文选取黄土高原西南部高山湖泊——六盘山天池沉积岩芯为研究对象,基于XRF岩芯元素数据分析,结合可靠的AMS 14C年代序列,重建了中晚全新世以来六盘山流域土壤侵蚀强度变化记录.结果显示:5570?—?1600 cal BP,流域土壤侵蚀整体较强,侵蚀强度逐渐减弱,其主要受控于降水变化,也受植被覆盖等因素的影响;随着晚全新世气候逐渐变干,1600 cal BP之后的侵蚀强度整体弱于前一时期,此时段由于人类活动的显著影响,加剧了流域的土壤侵蚀.太阳辐射可能是研究区土壤侵蚀强度变化的初始驱动力,ENSO通过驱动亚洲季风变化影响区域降水,进而直接影响流域土壤侵蚀的强度变化.     

保定市2013~2019年秋冬季污染物浓度变化特征

为深入了解保定市空气质量状况,揭示保定市空气污染变化趋势、多尺度变化特征和突变特性,综合利用Morlet小波分析和Mann-Kendall非参数检验方法,对保定市2013~2019年秋冬季PM₁₀、PM_2.5、SO₂、NO₂、CO和O₃-8h 6种常规大气污染物年均浓度和秋冬季污染特征逐日数据进行分析.结果表明：除O₃-8h外保定市其它各污染物年均浓度逐年下降,全年重度污染天数占全年天数的比例从31%下降到6.6%,整体呈好转趋势,但2013~2019年秋冬季重度污染天数占全年重度污染天数的81%~97%,秋冬季污染依然需要重视;小波分析结果显示,保定市秋冬季各污染物浓度存在显著的周期性变化,周期震荡主要在20d准双周、50~90d左右的季节内震荡和90~110d的季节震荡3个时间尺度范围,污染物浓度存在的低频震荡与大气中存在的低频震荡密切相关;历年各污染物污染最严重的月份多集中在12月、1月和2月,主要与污染源排放强度和相对静稳的大气条件有关;各污染物污染序列突变点多集中于10月和3月;2019~2020年秋冬季NO₂呈极显著的下降趋势,且突变点较往年提前1个月,这与疫情期间车辆排放大幅降低有直接关系;SO₂和CO在2013~2014年和2015~2016年秋冬季的突变点时间相近,这可能与冬季居民取暖散煤的不完全燃烧有关,2015年后保定实施了煤改气、煤改电,劣质散煤专项治理等措施后,2种污染物突变点时间存在差异,说明清洁取暖措施对降低SO₂浓度,改善空气质量的效果明显.     

碳中和愿景的实现路径与政策体系

习近平主席在第七十五届联合国大会上郑重承诺中国将努力争取2060年实现碳中和目标，为中国未来低碳转型促进经济高质量发展、生态文明建设指明了方向、明确了目标，也提振了全球应对气候变化的信心。作为排放量全球最大的发展中国家，在2030年前达峰后用三十年左右的时间很快地实现碳中和愿景，任务异常艰巨，但总体上排放路径必然呈现尽早达峰、稳中有降、快速降低、趋稳中和的过程。支撑碳中和的技术几乎涉及所有的产业和经济活动，从控制碳排放途径的角度可以分为高能效循环利用技术、零碳能源技术、负排放技术。政府、企业、个人在迈向碳中和愿景进程中具有至关重要而又各有侧重的作用，需要科学的政策体系以形成系统有效的激励机制，促进资本和人才朝着碳中和技术创新和市场化推广应用方向快速汇集。     

重污染天气应对“绩效分级、差异化管控”措施首次实践效果后评估

为提高重污染天气应对的科学性和精准度,2019年7月生态环境部制定重污染天气应对“绩效分级、差异化管控”措施.为应对9月底至10月初的重污染过程,京津冀及周边共68个城市启动重污染预警,该措施得以首次实践.通过时间序列断点回归方法对该措施效果进行评估发现,空气质量改善存在滞后的现象,SO₂、 NO₂和CO这3个气态污染物改善速度较快,对涉及二次生成的O₃和PM_2.5两个污染物见效速度相对较慢. 10月1日恰逢在北京举办庆祝中华人民共和国成立70周年阅兵式,对10月1日当天进行评估,发现与假如不采取措施的情形相比,重污染应急措施使北京市PM_2.5、 NO₂和CO日均浓度显著下降,下降幅度分别为54.1%、 62.4%和25.8%.如果不采取重污染应急措施,北京10月1日上午可能出现中重度污染,但实际上空气质量保持在良的水平.区域启动预警的68城市PM_2.5、 PM₁₀、 NO₂、 SO     

紫外光降解高浓度氯苯气体的研究

为评价紫外光降解作为高浓度挥发性有机物生物预处理的可行性,系统考察了其对高浓度氯苯气体的去除性能及其影响因素.所考察的影响因素包括紫外光波长、进口ρ(氯苯)、空塔停留时间和气体相对湿度等.结果表明:复合254和185 nm波长紫外光照射对氯苯的去除效果优于单一254 nm波长;紫外光降解反应器的进口ρ(氯苯)在2 300～2600 mg/m3,空塔停留时间为27 s时,对氯苯气体的去除率可达40%,继续延长空塔停留时间对氯苯去除率的提高作用有限;进口ρ(氯苯)在150～3 000 mg/m3时,氯苯去除速率随进口浓度单调增加,当高于3 000 mg/m3时,氯苯去除速率基本保持不变;增加气体相对湿度可以提高紫外光降解反应器对氯苯的去除效果.      

二叉树创建算法的研究

通过对二叉树四种遍历方法的分析,给出四种建立二叉树的通用算法,以及对这些算法效率的初步分析．解决了二叉树在实际应用中创建的问题,同时,给出的算法对一些高级树型数据结构的研究也具有一定参考价值．参4．     

Influence of environmental temperature and relative humidity on photocatalytic oxidation of toluene on activated carbon fibers coated TiO2

TiO₂ supported on active carbon fiber (TiO₂/ACF), an absorbable photocatalyst, is a new kind of material applied in air purification. In this paper, the influence of environmental temperature (T) and relative humidity (RH) on the gas-solid adsorption of toluene and the photocatalytic oxidation (PCO) efficiency of adsorbed toluene on TiO₂/ACF were studied, and then, the purification capability of TiO₂/ACF was estimated. PCO results showed that although the PCO efficiency increased under high RH and T levels, the amount of adsorption of toluene decreased. Moreover, quantitative analysis results of intermediates indicated that more environmental risk emerged when PCO of toluene was carried out at higher environmental T and RH levels because more toxic intermediates would be accumulated on the TiO₂/ACF. So, it is significant to control the environmental T and RH conditions in the application of the PCO technique. T = 25°C and RH530% is the optimal condition for purifying toluene in our experimental system.     

气候变化研究的中国知识贡献及其影响局限

气候变化知识的不断深化和积累是全球气候治理的基础。政府间气候变化专门委员会(IPCC)邀请全球有代表性的科学家,通过分析评估国际上正式发表的文献,提供关于全球气候变化科学进展的最新认识结论。本文基于文献计量学,通过统计中国在气候变化十大重要领域的科技成果产出量和影响力、中国政府和科学家对IPCC评估报告的参与以及中国大陆引文在IPCC第五次评估报告中的贡献,分析了中国对全球气候变化知识的贡献与局限。结果表明:近十年来,中国在气候变化大多数领域的科技成果产出量已居全球第二或第三位,但在海洋与气候变化、适应气候变化和全球气候治理领域的国际论文量明显落后;与美国和英国相比,中国气候变化科技成果的各类影响力指标明显偏低;中国对IPCC评估报告的参与度和影响力在不断提升,中国积极组织相关机构和专家参与IPCC评估工作,对全球气候治理起到了重要的科学支撑作用;但从IPCC第五次评估报告中国大陆引文的角度看,中国贡献仍整体偏弱,中国大陆引文的贡献呈领域分布不均衡,优势领域少,成果影响面窄的特点。与科学基础领域相比,中国在影响和适应、减缓和国际合作领域的科学贡献更弱,对全球视角关注不够,但中国大陆引文总体的国际科学合作活跃度较高。后巴黎时代,中国需要更加面向国家需求、气候公约和《巴黎协定》目标以及国际气候变化科技前沿,加强全球视野和原始创新,突出中国优势和特色,使气候变化的中国研究成果更多支撑全球气候治理进程的推进。     

Optimized determination of airborne tetracycline resistance genes in laboratory atmosphere

• Sampling parameters with high efficiency was determined. • Operational process to detect airborne ARGs was optimized. • Providing research basis to control airborne ARGs of a laboratory atmosphere Antibiotic resistance genes (ARGs) have been detected in various atmospheric environments. Airborne ARGs transmission presents the public health threat. However, it is very difficult to quantify airborne ARGs because of the limited availability of collectable airborne particulate matter and the low biological content of samples. In this study, an optimized protocol for collecting and detecting airborne ARGs was presented. Experimental results showed that recovery efficiency tended to increase initially and then declined over time, and a range of 550–780 copies/mm² of capture loading was recommended to ensure that the recovery efficiency is greater than 75%. As the cell walls were mechanically disrupted and nucleic acids were released, the buffer wash protects ARGs dissolution. Three ratios of buffer volume to membrane area in buffer wash were compared. The highest concentrations of airborne ARGs were detected with 1.4 µL/mm² buffer wash. Furthermore, the majority of the cells were disrupted by an ultrasonication pretreatment (5 min), allowing the efficiency ARGs detection of airborne samples. While, extending the ultrasonication can disrupt cell structures and gene sequence was broken down into fragments. Therefore, this study could provide a theoretical basis for the efficient filter collection of airborne ARGs in different environments. An optimized sampling method was proposed that the buffer wash was 1.4 µL/mm² and the ultrasonication duration was 5 min. The indoor airborne ARGs were examined in accordance with the improved protocol in two laboratories. The result demonstrated that airborne ARGs in an indoor laboratory atmosphere could pose the considerable health risk to inhabitants and we should pay attention to some complicated indoor air environment.     

Spatial and temporal variations of PAHs in surface sediments of estuarine and coast of CanGio wetland,Vietnam

Surface sediments from estuarine and coast of CanGio wetland (CGW) of Hochiminh City, Vietnam, were investigated to identify the spatial and temporal variations of polycyclic aromatic hydrocarbons (PAHs). The total PAHs showed wide variation but similar to patterns observed (F?=?0.901, p?=?0.46) in LongTau (31?±?77 ng/g dry weight, n?=?13), SoaiRap (53?±?81, n?=?4), ThiVai (60?±?62, n?=?10) estuaries, and coastal areas (112?±?211, n?=?9). A decreasing trend in the wet season (F?=?8.8, p?=?0.01) reflected that inland sources such as wastewater discharged and atmospherically transported contaminants contributed to PAHs in sediments. The risk posed by the PAHs in the coastal and estuarine areas of CGW is still negligible. The present study provides baseline data, which can be used for regular monitoring and future strategy of environmental protection for the study area.