三峡水库消落区土壤、植物汞释放及其在斑马鱼体的富集特征

利用室内模拟试验,探讨了三峡水库消落区淹没后土壤、植物汞释放特征及其在斑马鱼体的富集水平.结果表明,随淹水时间的延长,淹没土壤中总汞(THg)含量下降;水体THg浓度总体明显升高.淹没土壤及水体中甲基汞(MMHg)含量总体明显上升,其中稗草+土壤处理水体中增加尤为明显,淹水21 d后,其浓度是土壤处理的2.52倍.表明消落区土壤、植物是水库水体汞的一个重要来源.供试稗草淹水分解造成水体pH及溶解氧(DO)含量下降、溶解性有机碳(DOC)含量上升,对土壤MMHg含量无明显影响,对水体MMHg影响较大.供试斑马鱼头部、内脏及肌肉中THg含量总体明显上升,与水体中THg浓度具有显著相关性(P<0.01).鱼体头部、内脏及肌肉中均出现不同程度的MMHg富集现象,以头部与肌肉最为明显.淹水21 d后,添加土壤处理的鱼体头部、内脏及肌肉MMHg增加的含量分别是对照的1.75~6.25、3.53~8.38、2.22~3.36倍;稗草+土壤处理的分别是土壤处理的3.57、2.37、1.52倍.可见,淹没土壤是鱼体MMHg增加的重要来源,淹没植物改变原水环境条件影响其向水体释汞过程能提高鱼体中MMHg含量.     

CdSe/ZnS量子点对稀有鮈鲫胚胎发育的影响及其氧化应激作用

本研究以稀有鮈鲫(Gobiocypris rarus)为对象,研究了不同浓度CdSe/ZnS量子点(QDs)暴露下,稀有鮈鲫胚胎发育过程中自主运动频率、内心率和体长的变化,以及利用体内超氧化物歧化酶(SOD)和丙二醛(MDA)作为毒性指标,反映CdSe/ZnS QDs暴露对稀有鮈鲫胚胎发育的氧化应激作用.结果显示:CdSe/ZnS QDs对稀有鮈鲫胚胎72 hpf(hours post fertilization)的半致死浓度(LC50)为319.629 nmol·L-1,96 hpf的半致畸浓度(EC50)为203.312 nmol·L-1.CdSe/ZnS QDs暴露不仅影响稀有鮈鲫胚胎死亡率、畸形率、自主运动频率、孵化时间和孵化率,而且使其内心率减缓、体长缩短,导致胚胎卵凝结,心包囊肿,出现脊椎弯曲等多种毒性现象.同时发现,CdSe/ZnS QDs暴露导致稀有鮈鲫体内MDA含量增加以及SOD活力的降低.这表明CdSe/ZnS QDs对稀有鮈鲫胚胎发育具有致畸、致死作用,而氧化应激可能是引起其胚胎致畸、致死的重要机制之一.     

DOC/CCRT老化对柴油公交车气态物排放特性的影响

基于重型底盘测功机,研究新鲜及老化氧化型催化器(DOC)、氧化型催化器耦合催化型颗粒捕集器(DOC+CDPF,CCRT)对在用国Ⅲ柴油公交车进行中国典型城市公交车循环CCBC时一氧化碳(CO)、总碳氢化合物(THC)、一氧化氮(NO)、二氧化氮(NO_2)和氮氧化物(NO_x)、二氧化碳(CO_2)等气态物排放特性的影响.结果表明:采用新鲜及老化DOC/CCRT,均可以降低CO、THC、NO排放,增加NO_2排放,NO_x及CO_2排放基本不变;在怠速、加速、减速及匀速这4种工况下,新鲜DOC比老化DOC对CO、THC氧化效率好,新鲜CCRT比老化CCRT对THC氧化效率好,但老化CCRT对CO氧化效率更好,新鲜DOC/CCRT比老化DOC/CCRT对NO减少幅度高,对NO_2增加幅度高,但对NO_x排放总量基本无影响.     

小型露天采石场爆破作业安全评价方法的探讨

应用安全检查表、事故树、作业条件危险性分析等方法对露天小型采石场爆破作业进行了分析评价,找出了导致爆破作业事故发生的可能因素及可采用的预防途径,为小型露天爆破作业事故的预防提供有益参考.     

Effects of cerium on growth and physiological mechanism in plants under enhanced ultraviolet-B radiation

Effect of cerium （Ce^3＋） on the growth, photosynthesis and antioxidant enzyme system in rape seedlings （Brassica juncea L.） exposed to two levels of UV-B radiation （T1： 0.15 W/m^2 and T2：0.35 W/m^2） was studied by hydroponics under laboratory conditions. After 5 d of UV-B treatment, the aboveground growth indices were obviously decreased by 13.2%-44. 1%（T1） and 21.4%-49.3% （T2）, compared to CK, and except active absorption area of roots, the belowground indices by 14.1%-35.6%（T1） and 20.3%-42.6% （T2）. For Ce＋UV-B treatments, the aboveground and belowground growth indices were decreased respectively by 4.1%-23.6%, 5.2% -23.3%（Ce＋T1） and 10.8%-28.4%, 7.0%-27.8%（Ce＋T2）, lower than those of UV-B treatments. The decrease of growth indices appeared to be the result of changes of physiological processes. Two levels of UV-B radiation induced the decrease in chlorophyll content, net photosynthesis rate, transpiration rate, stomatal conductance and water use efficiency by 11.2%-25.9%（T1） and 20.9%- 56.9%（T2）, whereas increase in membrane permeability and activities of antioxidant enzymes including superoxide dismutase（SOD）, catalase （CAT） and peroxidase （POD） by 6.9%, 22.8%, 21.5%, 9.5%（T1） and 36.6%, 122.3%, 103.5%, 208.9%（T2）, respectively. The reduction of the photosynthetic parameters in Ce＋UV-B treatments was lessened to 3.2%-13.8%（Ce＋T1） and 4.9%-27.6%（Ce＋T2）, and the increase of membrane permeability and activities of antioxidant enzymes except POD in the same treatments were lessened to 2.4%, 8.4%, 6.6%（Ce＋T1） and 30.1%, 116.7%, 75.4%（Ce＋T2）. These results indicate that the regulative effect of Ce on photosynthesis and antioxidant enzymatic function is the ecophysiological basis of alleviating the suppression of UV-B radiation on growth of seedlings. Furthermore, the protective effect of Ce on seedlings exposed to TI level of UV-B radiation is superior to T2 level.     

不同喷雾方式下低阻文丘里振弦栅除尘配置优化实验研究

为了对比径向外喷和轴向喷雾下的低阻文丘里振弦栅耦合除尘效果,以除尘效率和系统阻力为参照,选定喉管气速、振弦栅数、纤维丝间隙和喉管液气比进行单因素实验。结果表明2种喷雾方式的除尘效率和系统阻力的变化趋势相同。利用SPSS软件进行4因素3水平正交实验设计,在特定参数条件下,2种喷雾方式的因素影响排序相同,除尘效率为纤维栅数＞纤维丝间隙＞喉管气速＞喷雾量;系统阻力为喉管气速＞纤维栅数＞纤维丝间隙＞喷雾量;径向外喷最佳配置为喉管气速24 m/s、喷雾量2.3 L/min、2块间隙为0.8 mm纤维栅板;轴向喷雾为喉管气速28 m/s、喷雾量2.4 L/min、2块间隙为0.8 mm纤维栅板;在最优配置下的除尘性能为径向外喷＞轴向喷雾。     

Characteristics that make trophy hunting of giant pandas inconceivable

In November 1928, Theodore Jr. and Kermit Roosevelt led an expedition to China with the expressed purpose of being the first Westerners to kill the giant panda (Ailuropoda melanoleuca). The expedition lasted 8 months and resulted in the brothers shooting a giant panda in the mountains of Sichuan Province. Given the concurrent attention in the popular press describing this celebrated expedition, the giant panda was poised to be trophy hunted much like other large mammals around the world. Today, however, the killing of giant pandas, even for the generation of conservation revenue, is unthinkable for reasons related to the species itself and the context, in time and space, in which the species was popularized in the West. We found that the giant panda's status as a conservation symbol, exceptional charisma and gentle disposition, rarity, value as a nonconsumptive ecotourism attraction, and endemism are integral to the explanation of why the species is not trophy hunted. We compared these intrinsic and extrinsic characteristics with 20 of the most common trophy-hunted mammals to determine whether the principles applying to giant pandas are generalizable to other species. Although certain characteristics of the 20 trophy-hunted mammals aligned with the giant panda, many did not. Charisma, economic value, and endemism, in particular, were comparatively unique to the giant panda. Our analysis suggests that, at present, exceptional characteristics may be necessary for certain mammals to be excepted from trophy hunting. However, because discourse relating to the role of trophy hunting in supporting conservation outcomes is dynamic in both science and society, we suspect these valuations will also change in future.     

Biofiltration and disinfection codetermine the bacterial antibiotic resistome in drinking water: A review and meta-analysis

• Published data was used to analyze the fate of ARGs in water treatment. • Biomass removal leads to the reduction in absolute abundance of ARGs. • Mechanism that filter biofilm maintain ARB/ARGs was summarized. • Potential BAR risks caused by biofiltration and chlorination were proposed. The bacterial antibiotic resistome (BAR) is one of the most serious contemporary medical challenges. The BAR problem in drinking water is receiving growing attention. In this study, we focused on the distribution, changes, and health risks of the BAR throughout the drinking water treatment system. We extracted the antibiotic resistance gene (ARG) data from recent publications and analyzed ARG profiles based on diversity, absolute abundance, and relative abundance. The absolute abundance of ARG was found to decrease with water treatment processes and was positively correlated with the abundance of 16S rRNA (r² = 0.963, p<0.001), indicating that the reduction of ARG concentration was accompanied by decreasing biomass. Among treatment processes, biofiltration and chlorination were discovered to play important roles in shaping the bacterial antibiotic resistome. Chlorination exhibited positive effects in controlling the diversity of ARG, while biofiltration, especially granular activated carbon filtration, increased the diversity of ARG. Both biofiltration and chlorination altered the structure of the resistome by affecting relative ARG abundance. In addition, we analyzed the mechanism behind the impact of biofiltration and chlorination on the bacterial antibiotic resistome. By intercepting influent ARG-carrying bacteria, biofilters can enrich various ARGs and maintain ARGs in biofilm. Chlorination further selects bacteria co-resistant to chlorine and antibiotics. Finally, we proposed the BAR health risks caused by biofiltration and chlorination in water treatment. To reduce potential BAR risk in drinking water, membrane filtration technology and water boiling are recommended at the point of use.     

Biological conversion pathways of sulfate reduction ammonium oxidation in anammox consortia

• The SRAO phenomena tended to occur only under certain conditions. • High amount of biomass and non-anaerobic condition is requirement for SRAO. • Anammox bacteria cannot oxidize ammonium with sulfate as electron acceptor. • AOB and AnAOB are mainly responsible for ammonium conversion. • Heterotrophic sulfate reduction mainly contributed to sulfate conversion. For over two decades, sulfate reduction with ammonium oxidation (SRAO) had been reported from laboratory experiments. SRAO was considered an autotrophic process mediated by anammox bacteria, in which ammonium as electron donor was oxidized by the electron acceptor sulfate. This process had been attributed to observed transformations of nitrogenous and sulfurous compounds in natural environments. Results obtained differed largely for the conversion mole ratios (ammonium/sulfate), and even the intermediate and final products of sulfate reduction. Thus, the hypothesis of biological conversion pathways of ammonium and sulfate in anammox consortia is implausible. In this study, continuous reactor experiments (with working volume of 3.8L) and batch tests were conducted under normal anaerobic (0.2≤DO<0.5 mg/L) / strict anaerobic (DO<0.2 mg/L) conditions with different biomass proportions to verify the SRAO phenomena and identify possible pathways behind substrate conversion. Key findings were that SRAO occurred only in cases of high amounts of inoculant biomass under normal anaerobic condition, while absent under strict anaerobic conditions for same anammox consortia. Mass balance and stoichiometry were checked based on experimental results and the thermodynamics proposed by previous studies were critically discussed. Thus anammox bacteria do not possess the ability to oxidize ammonium with sulfate as electron acceptor and the assumed SRAO could, in fact, be a combination of aerobic ammonium oxidation, anammox and heterotrophic sulfate reduction processes.     

Enhanced debromination of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) by zero-valent zinc with ascorbic acid

• Highly efficient debromination of BDE-47 was achieved in the ZVZ/AA system. • BDE-47 debromination by the ZVZ/AA can be applied to a wide range of pH. • AA inhibits the formation of (hydr)oxide and accelerates the corrosion of ZVZ. • Reduction mechanism of BDE-47 debromination by the ZVZ/AA system was proposed. A new technique of zero-valent zinc coupled with ascorbic acid (ZVZ/AA) was developed and applied to debrominate the 2,2′,4,4′-Tetrabromodiphenyl ether (BDE-47), which achieved high conversion and rapid debromination of BDE-47 to less- or non-toxic forms. The reaction conditions were optimized by the addition of 100 mg/L ZVZ particles and 3 mmol/L AA at original solution pH= 4.00 using the solvent of methanol/H₂O (v:v= 4:6), which could convert approximately 94% of 5 mg/L BDE-47 into lower-brominated diphenyl ethers within a 90 min at the ZVZ/AA system. The high debromination of BDE-47 was mainly attributed to the effect of AA that inhibits the formation of Zn(II)(hydr)oxide passivation layers and promotes the corrosion of ZVZ, which leads to increase the reactivity of ZVZ. Additionally, ion chromatography and gas chromatography mass spectrometry analyses revealed that bromine ion and lower-debromination diphenyl ethers formed during the reduction of BDE-47. Furthermore, based on the generation of the intermediates products, and its concentration changes over time, it was proposed that the dominant pathway for conversion of BDE-47 was sequential debromination and the final products were diphenyl ethers. These results suggested that the ZVZ/AA system has the potential for highly efficient debromination of BDE-47 from wastewater.