不同构型富氮生物炭对Pb (II)和Cr (VI)的作用机制

为了明确不同构型富氮生物炭对重金属的作用机理,本研究以玉米秸秆为生物质,通过尿素改性结合高温热解制备了3种不同氮构型的富氮生物炭（以吡咯氮为主的Pr-NBC、吡啶氮为主的Pd-NBC和石墨氮为主的Gp-NBC）,考察其对典型重金属的作用行为.吸附动力学和吸附等温线等实验结果显示：富氮生物炭对Pb （II）和Cr （VI）的吸附均以化学吸附为主,且存在明显的差异;对Pb （II）的吸附容量与溶液离子强度成正比,吸附可能以形成内层络合物为主,对Cr （VI）的作用则包含吸附和还原两个过程;对两种重金属的吸附容量受pH影响较大,静电吸引作用可能是主要驱动力.吸附前后的材料表征显示：富氮生物炭主要通过静电吸引作用、阳离子交换、沉淀作用和阳离子-π键作用吸附Pb （II）,通过静电吸引作用吸附Cr （VI）,同时能将Cr （VI）还原为Cr （III）.不同构型氮与重金属作用机理存在差异,其中,石墨氮主要通过与Pb （II）形成阳离子-π键作用促进吸附,吡咯氮和吡啶氮具有还原性,可将Cr （VI）转化为Cr （III）,实现减毒.因此,在考察自然环境中富氮生物炭对重金属的作用机制时,应当充分考虑氮构型的影响.     

中国粮食主产区耕地撂荒程度及其对粮食产量的影响

耕地撂荒严重地影响着我国的粮食安全。以我国粮食主产区为研究区域,在识别撂荒地分布的基础上,测度了撂荒地空间分布格局,并建立耕地撂荒中介效应模型,探究了耕地撂荒对区域粮食产量的影响机制。结果表明：（1）中国粮食主产区耕地撂荒规模为405.53万hm²,撂荒率约为5.85%;空间上撂荒地规模分布呈“T”字形空间格局,黑龙江东北部、吉林西北部以及内蒙古南部地区为撂荒地主要集聚区。（2）耕地撂荒对于粮食主产区粮食产量具有显著负向影响,2017年我国粮食主产区因耕地撂荒损失的农田生产潜力达到1339.15万t,损失的粮食产量高达2265.6万t,损失比例达4.69%;内蒙古自治区成为粮食产出损失量和损失比例最大的地区。（3）粮食播种面积、农田生产潜力和农业技术投入均发挥了部分中介作用,系数分别为-0.194、-0.025和0.006。（4）应遵从城乡融合以及农业农村发展态势,强化粮食主产区农业生产现代要素投入与政策扶植,构建粮食生产—耕地休耕空间转换弹性机制,保障我国粮食安全。     

全球跨境水资源合作时空演变及生成机制

跨境水资源合作对人类社会的可持续发展和国家水权益保障意义重大。以166个国家为研究样本,选择1948—2008年全球跨境水资源合作事件为基础数据,提取合作关系并构建全球跨境水资源合作网络。基于社会网络分析、层次分析等方法,探讨了跨境水合作事件及其网络的时空复杂性,阐述了跨境水合作生成机制与合作类型。研究发现：水合作事件数量与频次呈波动增长,阶段特征显著;水合作网络结构的去中心化、多极化和区域化趋势明显,东西方阵营在冷战时代主导了全球水合作,后冷战时代的热点合作广泛产生在非洲、东欧地区和亚洲水塔周边地区;水合作对地理距离表现为高敏感性,同一流域内国家互动频繁,域外大国在不同时期介入热点流域水合作事务;国家行为体、区域合作关系和国际合作体系三个层次综合影响水合作关系的生成,各层次内部有着复杂的多因素互动,强制型、功利型、规范型和意识形态型水合作是四种主要跨境水合作类型。     

木耳菌糠生物炭对阳离子染料的吸附性能研究

为了有效处理印染废水,以废弃木耳菌糠（AG）为原料,采用限氧热解法在350、550、750℃的温度下制备木耳菌糠生物炭（AGBC）,处理含有孔雀石绿（MG）、番红花红T （ST）的有色废水.考察了不同初始pH值、吸附时间、初始浓度对AGBC吸附MG、ST的影响,讨论了吸附动力学及等温吸附特性.并利用傅里叶变换红外光谱（FTIR）、X射线衍射仪（XRD）、扫描电子显微镜（SEM）等技术对吸附前后的菌糠生物炭进行表征,探究吸附机理.结果表明：随着热解温度的升高,吸附剂表面的含氧官能团数量逐渐减少,而比表面积和芳香化程度逐渐增加.MG的平衡吸附量随溶液pH值的升高而增大,而ST的平衡吸附量呈现相反趋势.AGBC对MG、ST的吸附分别在8h和4h基本达到平衡.AGBC对MG的吸附过程符合准一级动力学模型与Freundlich模型,说明吸附过程以物理吸附为主;对ST的吸附过程符合准二级动力学模型与Freundlich模型,说明吸附过程以化学吸附为主.与AG350和AG550相比,AG750对MG和ST的吸附量更高,经Langmuir模型拟合,其对MG和ST的最大吸附量分别为10249.79mg/g、3353.49mg/g.吸附机理表明,AGBC对MG的吸附主要为静电引力和π-π共轭作用,对ST的吸附主要为氢键作用、π-π共轭作用以及静电引力.说明AGBC对阳离子染料具有一定的吸附潜力,是一种经济高效的吸附材料.     

生态系统服务约束关系界定及影响机制分析

以长江经济带为研究对象,选择InVEST模型对长江经济带代表性的5种生态系统服务进行评估,根据两两配对关系原理进行约束线提取,并构建生态系统服务约束关系与影响因素相互作用模型,对其作用机制进行探究.结果表明,2000~2015年长江经济带5种生态系统服务两两间共表现出矩形型,对数型,抛物线型和驼峰型4种约束类型;7种影响因素与配对的10对约束关系间均呈弱相关性;影响因子与约束关系作用关系曲线的空间变化呈现较大差异,总体为上下波动的趋势;影响因子对约束关系的贡献程度情况各异.辐射对约束关系的平均贡献率最高,达21.43%,其中对粮食供给-生境质量的贡献率最高,为33.10%;NDVI的平均贡献率最低,为7.55%,其中对粮食供给-生境质量的贡献率最低,为5.70%;各因素间相互作用、彼此制约的关系是生态系统服务约束关系变化的内在机制.     

双酚AF诱导乳腺癌细胞增殖的分子机制

从细胞水平上研究不同浓度双酚AF （BPAF）对MCF-7人乳腺癌细胞系的细胞增殖能力、细胞凋亡、细胞周期等终点的影响;以新型雌激素膜受体GPER1介导的PI3K/Akt和ERK1/2信号通路为靶点,研究低浓度BPAF对该信号通路相关基因表达的影响,以及其在诱导乳腺癌细胞增殖中的作用,评估其增殖效应机制.结果表明,低浓度BPAF （0.001~1μmol/L）能够诱导MCF-7细胞的增殖,使S期细胞比例升高,并且激活雌激素信号通路相关基因mRNA的表达;在较高浓度时（>10μmol/L）能抑制细胞活力,诱导细胞凋亡.通过特异性靶点抑制剂发现GPER1在mRNA层面上激活了PI3K/Akt和ERK1/2信号通路,并且该信号通路的激活可能是BPAF引起MCF-7细胞增殖的关键机制,并且ERα也在其中起到了重要的作用.     

原位形成生物铁锰氧化物对砷(Ⅲ/V)的去除效果与机制

通过改变砷的初始浓度、砷价态、细菌接种比、铁锰浓度等因素来研究不同条件下Pseudomonas putida strain MnB1原位诱导形成生物铁锰氧化物（Biogenic Fe-Mn oxides,BFMO）对As（Ⅲ）和As（V）的去除效果与机制.结果表明：①当As（Ⅲ）和As（V）初始浓度为0.5~5 mg·L^-1时,原位形成的BFMO对As（Ⅲ）和As（V）有良好的去除效率,均在62%以上;②当细菌接种比为0.1%~0.5%时,As（Ⅲ）和As（V）的去除效率与细菌接种比成正比,当细菌接种比大于0.5%时,As（Ⅲ）和As（V）的去除效率基本维持在85%以上,未发生明显变化;③当MnCO₃浓度为0.2~0.8 g·L^-1或Fe（Ⅱ）浓度为2.5~25 mg·L^-1时,原位诱导产生的BFMO对As（Ⅲ）和As（V）的去除率随MnCO₃浓度或Fe（Ⅱ）浓度的增加而增大;当MnCO₃或Fe（Ⅱ）浓度再升高时,As（Ⅲ）和As（V）的去除效率基本保持不变.微观特征分析结果表明,原位形成的BFMO与As（Ⅲ）和As（V）反应后主要产物为As（V）,其去除主要以吸附为主,还存在共沉淀作用.总体而言,原位形成的BFMO适用于砷污染水环境的修复.     

An unusual high ozone event over the North and Northeast China during the record-breaking summer in 2018

Under the background of global warming, the summer temperature of the North and Northeast China (NNEC) has significantly increased since 2017, which was accompanied by the aggravated ozone (O₃) pollution. In 2018, the NNEC experienced a record-breaking summer of the past 40 years. Influenced by the abnormal high temperatures, a regional ozone event occurred on 2-3 August, over 63% of 79 selected cities in the NNEC were exposed to O₃ pollution, and the maximum value of MDA8 O₃ reached 268 μg/m³. Observations indicated that ozone concentrations agree well with the maximum temperature at 2 meters (MT2M) over NNEC with a correlation coefficient of 0.69. During the pollution episode, strong downdraft in the local high (35°N-42.5°N, 112.5°E-132.5°E; LH) over the NNEC created the favourable meteorological conditions for O₃ formation. By analyzing the horizontal wind and wave activity fluxes (WAFs) at 200 hPa, we found that the LH formation was resulted from the Rossby wave propagation from upstream along the mid-latitude Asian jet. The split polar vortex intrusion further strengthened the amplitude of the Rossby wave and reinforced the LH. Moreover, a secondary circulation between Typhoon Jongdari and the LH contributed to the enhanced LH with strong subsidence. On the other hand, the stratospheric intrusions under the deep subsidence also contributed to the enhanced surface O₃. In this study, the deep-seated meteorological dynamical mechanisms contributing to the abnormal high temperatures were investigated, which can lead to a better understanding of the regional O₃ pollution over NNEC under the global-warming background.     

Removal of antibiotic-resistant genes during drinking water treatment: A review

Once contaminate the drinking water source, antibiotic resistance genes (ARGs) will propagate in drinking water systems and pose a serious risk to human health. Therefore, the drinking water treatment processes (DWTPs) are critical to manage the risks posed by ARGs. This study summarizes the prevalence of ARGs in raw water sources and treated drinking water worldwide. In addition, the removal efficiency of ARGs and related mechanisms by different DWTPs are reviewed. Abiotic and biotic factors that affect ARGs elimination are also discussed. The data on presence of ARGs in drinking water help come to the conclusion that ARGs pollution is prevalent and deserves a high priority. Generally, DWTPs indeed achieve ARGs removal, but some biological treatment processes such as biological activated carbon filtration may promote antibiotic resistance due to the enrichment of ARGs in the biofilm. The finding that disinfection and membrane filtration are superior to other DWTPs adds weight to the advice that DWTPs should adopt multiple disinfection barriers, as well as keep sufficient chlorine residuals to inhibit re-growth of ARGs during subsequent distribution. Mechanistically, DWTPs obtain direct and inderect ARGs reduction through DNA damage and interception of host bacterias of ARGs. Thus, escaping of intracellular ARGs to extracellular environment, induced by DWTPs, should be advoided. This review provides the theoretical support for developping efficient reduction technologies of ARGs. Future study should focus on ARGs controlling in terms of transmissibility or persistence through DWTPs due to their biological related nature and ubiquitous presence of biofilm in the treatment unit.     

Degradation of poly(butylene adipate-co-terephthalate) by Stenotrophomonas sp. YCJ1 isolated from farmland soil

In recent years, poly (butylene adipate-co-terephthalate) (PBAT) has been widely used. However, PBAT-degrading bacteria have rarely been reported. PBAT-degrading bacteria were isolated from farmland soil and identified. The effects of growth factors on the degradation of PBAT and the lipase activity of PBAT-degrading bacteria were assessed. The degradation mechanism was analyzed using scanning electron microscopy, attenuated total reflection Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, X-ray diffraction, and liquid chromatography-mass spectrometry. The results showed that Stenotrophomonas sp. YCJ1 had a significant degrading effect on PBAT. Under certain conditions, the strain could secrete 10.53 U/mL of lipase activity and degrade 10.14 wt.% of PBAT films. The strain secreted lipase to catalyze the degradation of the ester bonds in PBAT, resulting in the production of degradation products such as terephthalic acid, 1,4-butanediol, and adipic acid. Furthermore, the degradation products could participate in the metabolism of YCJ1 as carbon sources to facilitate complete degradation of PBAT, indicating that the strain has potential value for the bioremediation of PBAT in the environment.