渭河流域关中段地下水硝态氮来源解析

为定性及定量识别地下水中氮的污染来源及迁移转化特征,本文在水化学分析的基础上结合氮氧稳定同位素技术及SIAR模型对渭河流域关中段地下水补给来源、地下水中氮污染特征进行了判断.结果表明,渭河流域关中段地下水的主要水化学类型为HCO₃-Ca+Mg型,地下水由降水快速入渗补给和地表水入渗补给.地下水氮污染以硝态氮形式为主,在所采集的34个地下水水样中,硝态氮含量的变化范围为0.154~36.717mg/L,平均含量为6.17mg/L,其中硝态氮含量超过Ⅲ类地下水标准的采样点共有2个,超标率为5.9%.氮循环的主导作用为硝化作用.地下水δ¹⁵N-NO₃^-含量的变化范围为+6.08‰~+16.42‰,δ¹⁵O-NO₃^-含量的变化范围为+9.38‰~+12.514‰,硝态氮污染主要受到人类活动的影响,土壤有机氮、粪便及污废水和大气沉降是地下水硝态氮的主要贡献者,平均贡献率分别为44.65%、40.03%和15.32%.     

Novel electrochemical half-cell design and fabrication for performance analysis of metal-air battery air-cathodes

Metal-air batteries (MABs) are considered promising candidates for sustainable energy storage & conversion applications. Air-cathodes have been identified to be the major challenge towards the commercialization of MAB technology. In development of air-cathodes effectively, a method, or a device is desired for cathode evaluation at operating conditions that are as close as possible to that of an actual battery. In this paper, for diagnosing, evaluating and analyzing the electrochemical performance of MAB air-cathodes, a novel electrochemical half-cell has been designed and fabricated. This half-cell is a three-electrode system, in which the air-cathode is used as the working electrode, a platinum wire with large area as the counter electrode and a saturated calomel electrode (SCE) as the reference electrode. The working electrode is designed to allow the surface of gas diffusion layer to be exposed to the air and the catalyst layer to be exposed to the electrolyte. This half-cell is validated by commercially available and in-house made air cathodes using electrochemical linear scan voltammetry (LSV) method in both neutral and alkaline solutions at various temperatures, enabling the in-situ performance evaluation and analysis of air-cathodes in an environment much closer to that of a primary aqueous metal-air battery while offering a more controlled laboratory environment and economic way for down-selecting and optimizing the air-cathodes.     

The use of waste basic oxygen furnace slag and hydrogen peroxide to degrade 4-chlorophenol

A new treatment method is developed to degrade 4-chlorophenol (4-cp) and its oxidation intermediates. The experimental results of this research demonstrate that 4-cp and its oxidation intermediates can be decomposed completely by basic oxygen furnace slag (BOF slag) with hydrogen peroxide (H₂O₂) in an acid solution. The factors that effect the treatment efficiency were studied including initial concentration of 4-cp, pH of the solution, concentration of H₂O₂ and amount of BOF slag. The BOF slags are final waste materials in the steel making process. The major components of BOF slag are CaO, SiO₂, Fe₂O₃, FeO, MgO and MnO. As the BOF slag in an acid solution, FeO and Fe₂O₃ can be dissociated to produce ferrous ion and ferric ion. Ferrous ion reacts with hydrogen peroxide to form “Fenton's reagent” which can produce hydroxyl radicals (OH^.). Hydroxyl radical possession of high oxidation ability can oxidize organic chemicals effectively. Results show that 100 mg/l of 4-cp is decomposed completely within 30 min by 438.7 g/l BOF slag with 8.2 mM hydrogen peroxide in pH=2.8±0.2 solution. The COD value of the solution is reduced from 290 to 90 mg/l. The factors studied which affect the 4-cp decomposition efficiency were the hydrogen peroxide concentration, BOF slag concentration, pH of the solution and initial concentration of 4-cp. Because large amounts of Fe₂O₃ and FeO are present in the BOF slag, the BOF slag not only has a high treatment efficiency, but also can be used repeatedly.     

铝胁迫下不同耐铝小麦品种活性氧代谢差异及与小麦耐铝性的关系

逆境条件下植物体内产生并累积活性氧从而破坏植物组织结构与功能,同时植物也可以通过改变活性氧代谢相关酶活性清除活性氧而减轻活性氧伤害以适应环境胁迫。为研究铝胁迫下不同耐铝小麦品种（TriticumaestivumL．）在活性氧代谢上的差异及与小麦耐铝性的关系,本试验选用小麦品种ET8（耐铝型）、ES8（铝敏感型）为试验材料研究了不同耐铝小麦品种活性氧代谢变化上的差异。结果表明,50μmol·L-1铝处理24h,ET8和ES8活性氧含量显著升高,O2产生速率增幅分别为10．5％和20．4％,H202含量增幅分别为3．3％和7．6％。ET8和ES8超氧化物歧化酶（SOD）活性增幅分别为11．9％和41．6％,过氧化物酶（POD）活性增幅为51．8％和77．8％,抗坏血酸过氧化物酶（APX）活性增幅为54．4％和29．1％,过氧化氢酶（CAT）活性增幅为32．9％和38．4％,谷胱甘肽还原酶（GR）活性增幅为83．1％和85．5％。虽然抗氧化酶活性增加后会清除一部分活性氧,但活性氧的累积仍然造成了膜脂的过氧化,ET8和ES8丙二醛（MDA）含量分别增加18．2％和50．0％,质膜透性也随着MDA含量的升高而增加,增幅分别为1．25倍和1．36倍。综上所述,不同耐铝品种间活性氧代谢的差异是小麦品种耐铝性差异显著的原因之一。     

微囊藻毒素-LR对罗非鱼鳃组织活性氧自由基含量及相关抗氧化酶活性的影响

应用腹腔注射的方式,研究了微囊藻毒素MC-LR对罗非鱼（Oreochromis niloticus）鳃组织活性氧自由基含量（ROS）及过氧化氢酶（CAT）、超氧化物歧化酶（SOD）活性的影响。结果表明：在MC-LR的胁迫下,罗非鱼鳃组织产生了大量的ROS,并引起了SOD和CAT 2种抗氧化酶活性的变化。SOD和CAT在清除过量的ROS时表现出的动态变化过程不同,SOD的变化曲线是多阶段的,而CAT则表现为先诱导后恢复的趋势。SOD和CAT在变化趋势上有所不同,但均表现为明显的时间与效应的正相关关系和剂量与效应的正相关关系。这也为将鳃组织中SOD和CAT作为抗氧化生物标志物来监测微囊藻毒素对罗非鱼胁迫作用提供了一定的参考。试验为研究微囊藻毒素对罗非鱼的生态毒理学作用提供相应的资料,并为罗非鱼质量安全问题的研究打下一定的基础。     

叔丁醇燃爆危险性研究

为预防叔丁醇氧化制甲基丙烯酸甲酯工艺过程中燃爆危险的发生,利用11L爆轰管测定不同工况温度、压力条件下,叔丁醇在不同氧含量的氧氮混合气中的爆炸极限,得到不同工况条〖JP2〗件下“叔丁醇-氧气-氮气”混合体系的燃爆区域;针对工艺过程中存在水蒸汽的条件,研究了水蒸汽含量对叔丁醇燃爆的影响。结果表明:叔丁醇在80℃、015MPa,170℃、015MPa,280℃、01MPa条件下的极限氧含量分别为159%、153%和135%;随着水蒸汽含量的升高,叔丁醇爆炸极限范围变小,在80℃、015MPa,170℃、015MPa条件下当水蒸汽含量增加到27%和34%时无燃爆现象发生。     

Spatial and seasonal variability of dissolved oxygen and nutrients in the Southern Adriatic coastal waters

The main objective of this paper is to present vertical and horizontal patterns of dissolved oxygen and nutrients found during four seasonal surveys (March, June, September and December 2000) in the Southern Adriatic Sea coastal waters. The multivariate technique Principal Component Analysis has been applied to our dataset considering the following parameters: seawater temperature, salinity, dissolved oxygen and nutrients (nitrate, nitrite, phosphate, silicate). The resulting plot shows in a self-explanatory way that a seasonal trend was not observable in the investigated period and that no significant differences occur between the stations sampled in the Taranto Gulf and those along the Adriatic coast. Water column stratification persists in all seasons, except in spring, in the shallowest stations. The surface layer is characterized by a low nutrient content. The influence of the Northern Adriatic Surface Water in the Southern Adriatic sub-basin seems to be very low and can be traced by nitrate and silicate only in spring and winter. Regarding deep waters, nitrate distribution shows an increasing gradient moving from the coast to the open sea, having the lowest concentration in the shelf area and the highest in the most offshore stations of the Otranto Strait. In the Otranto Strait area the vertical distributions of physical and chemical parameters show, at middle depths, the inflow of Levantine Intermediate Water, traced by both the maximum of salinity, nitrate and phosphate and the minimum of oxygen. The LIW signal is lost moving northward. The outflow of Adriatic Dense Water is less evident, being traced only in spring by an oxygen increase at the bottom layer in the shelf area. The N:P ratio is highly variable but in the range already observed in the Southern Adriatic, suggesting a P-limitation, which can both contribute to the low primary productivity of the area and support the N:P ratio anomaly of the Eastern Mediterranean.     

Mass spectral studies of 6‐n‐propyl‐2‐thiouracil,its oxygen,selenium and fluorinated congeners∗

The electron ionization mass spectra of the clinically used antithyroid agent 6‐n‐propyl‐2‐thiouracil (la), its minor metabolite, 6‐n‐propyluracil (lb) and their synthetic selenium and fluorinated analogs (1c and d) have been examined. The fragmentation pattern of these thiouracil and selenouracil studied bear strong similarities with those previously derived from a study of uracil analogs. Thus, the first step in the fragmentation is a retro Diel‐Alder decomposition with the loss of HCNX (X=O, S or Se) and the production of an ion radical which undergoes further fragmentation pathways which are discussed. 6‐n‐Propyl‐2‐selenouracil (1c) did show more complicated spectra due to the six natural isotopic abundance exhibited by the selenium atom. While the fluorinated analogs (1d) did substantiate the fact that the fragmentation pattern of these derivatives proceed through fragmentation between C₂ and N₃ bond since this produces the more resonance stabilized ion.     

Oxidative stress-mediated cardiac mast cell degranulation

Pulmonary mast cell degranulation is a well-characterized response to diesel exhaust exposure. A primary constituent of fossil fuel combustion is sulfur dioxide (SO₂). SO₂ was shown to induce mast cell degranulation in an immortalized cell line secondary to induction of intracellular oxidative stress; however, it is not known whether SO₂-induced oxidative stress directly triggers the activation of cardiac mast cells. Accordingly, this study sought to determine whether Na₂SO₃ induces degranulation of cardiac mast cells, and furthermore whether cardiac mast cell activation may be prevented by inhibition of oxidative stress. To this end, cardiac mast cells were isolated from epicardial surface of the heart and incubated with increasing concentrations of Na₂SO₃ (0, 0.5, or 5 mM). Antioxidant compounds targeting different mechanisms of free radical generation, including ebselen, diphenyleneiodonium (DPI), or α-tocopherol, were incubated with 5 mM of Na₂SO₃ in order to determine their efficacy in preventing mast cell degranulation. Na₂SO₃ induced a significant concentration-dependent histamine release from cardiac mast cells ranging from 8.87% to 18.86%, which was prevented by ebselen. No effect was observed with DPI and α-tocopherol under these conditions. In conclusion, these findings indicate that SO₂ is capable of producing cardiac mast cell degranulation in vitro; however, the variable effectiveness of the three antioxidants evaluated is indicative of a multifactorial mechanism mediating SO₂-induced cardiac mast cell degranulation. The particular effectiveness of ebselen in preventing mast cell degranulation may be related to its multiple mechanisms of preventing oxidative stress.     

淡水水体中氮污染源的识别——利用硝酸根中氮和氧同位素组成

氮营养盐污染在全球很多区域都是一个备受关注的环境问题,尤其是以农业为主的区域和人口密集的区域,因此,关于水体中氮污染源识别技术尤为重要.硝酸根离子中的氮、氧同位素组成在过去的十几年中频繁地应用于识别淡水水体中氮污染源的研究中.本文总结了已知氮污染源中氮、氧同位素组成的特征变化区间,阐述了影响氮、氧同位素组成的主要因素,描述了3种氮、氧同位素组成主流的测试方法,展望了未来定量测算各种氮污染源贡献比例的前景.在实际研究中,还将氮、氧同位素组成和水体化学特征结合,则可以有效地识别淡水水体的氮污染源.随着检测精度的不断提高,各种代表性端元污染物同位素值经验区间也变得更加准确.