新型生物反应墙原位修复石油烃污染地下水

以功能微生物、泥炭和粗砂为填充介质设计新型生物反应墙,研究了反应墙对地下水中石油烃污染物的修复效果与机理.结果表明:运行期内生物反应墙修复效果良好,苯系物、萘系物及菲去除率为83.6%～99.85%,其中71.23%～99.71%在墙体前半部分被去除.泥炭介质和功能微生物能够稳定发挥对污染物的吸附与降解功能,32.63%～77.98%的BTEX和97.14%～99.81%的目标PAHs被泥炭吸附去除;18.96%～50.98%的BTEX和已吸附于泥炭上的大部分石油烃污染物均显示被生物降解.微生物对污染物的降解可有效延长泥炭的吸附寿命,泥炭对功能微生物的营养供给可使反应墙内长期保持较高的功能微生物数量,每克干介质约含有3.46×106～6.16×109个.因此新型生物反应墙原位修复石油烃污染地下水是可行的.     

石油污染场地浅层地下水MNA原位修复潜能及微生物降解效益评估

监测式自然衰减(MNA)能够高效低耗地原位修复石油污染地下水的场地,微生物对污染物的降解对MNA过程起到了重要作用.在分析东北石油污染场地地下水中总石油烃(TPH)、电子受体的质量浓度分布和变化规律基础上,划分了微生物功能区.采用溶质通量计算法.对MNA原位修复的潜能及其微生物降解效果进行了评估.结果显示,场地微生物降解正在发生.利用的电子受体不同,划分为Mn、Fe和SO(2/4-)还原区.污染通量模型计算显示:上游地区微生物降解强度不断增强,下游地区微生物降解强度不断降低.监测期内石油烃总量降低了394 kg,微生物降解为自然衰减过程中的主要作用,其贡献率为64%～93%,每个通量断面内微生物降解率为0.18～0.73 kg/d.由此可以证明,MNA可以有效地修复地下水中的石油污染.     

湘西花垣渔塘铅锌矿床成矿物质来源的C、O、Pb、S同位素制约

渔塘铅锌矿床是花垣矿田中发现较早的超大型铅锌矿床之一,具有典型的“花垣式”铅锌矿床特征,本文通过对其C、O、S、Pb稳定同位素地球化学特征研究,探讨了其成矿物质来源。     

新疆卡拉麦里地区与韧-脆性剪切带有关的金矿床成因分析——来自流体包裹体、同位素的证据

东准噶尔卡拉麦里地区韧-脆性剪切带,形成于陆-陆碰撞体制,在330～265Ma期间,受挤压伸展体制转换影响,先后经历了韧、脆性构造变形。通过对与该韧-脆性剪切带有关的金矿床的流体包裹体、同位素组成研究表明：包裹体以气液相为主,均一温度集中在160～240℃,成矿流体盐度彬（NaCl）为3．55％～4．5％;成矿流体氢、氧同位素组成表明成矿流体的水为变质成因水;金属硫化物硫同位素扩S值为3．54‰～10．68‰,显然属于混染硫;黄铁矿包裹体氦氩同位素^3He／^4He值为0．18-2．18Ra,属幔壳混源。综合研究认为,金矿成矿在时间、空间上严格受韧-脆性剪切构造变形带控制。     

湖南通道地区金矿床成矿流体特征及成矿物质来源：来自流体包裹体、H-O-S同位素的证据

通道地区金矿床位于雪峰弧形金锑矿带西南段,主要包括茶溪、金坑和黄垢3个中小型金矿床,矿脉发育在前寒武系浅变质地层中,受断裂控制明显,矿石类型为石英脉型与蚀变岩型。通过野外地质调查、显微鉴定、流体包裹体测试及H、O、S同位素分析,对成矿流体特征与成矿物质来源进行约束。分析结果表明：成矿过程主要划分为2个阶段,一是石英+黄铁矿+毒砂+绢云母+金阶段;二是石英+绢云母+少量金阶段;其中茶溪矿区第一阶段石英包裹体均一温度为155~297 ℃,峰值为210~220 ℃,盐度［w（NaCl）］为4.9%~11.7%,第二阶段石英包裹体均一温度为135~233 ℃,峰值为160~170 ℃,盐度为3.3%~9.7%;金坑矿区第一阶段石英包裹体均一温度为202~261 ℃,峰值为210~220 ℃,盐度为5.6%~10.1%,第二阶段石英包裹体均一温度为134~203 ℃,峰值为150~160 ℃,盐度为3.8%~8.8%;黄垢矿区第一阶段石英包裹体均一温度为176~319 ℃,峰值为220~240 ℃,盐度为5.1%~11.7%;3个矿床中成矿流体的H-O同位素组成具有相似的变化趋势,第一阶段δ¹⁸O_fluid变化较小,分布在+4.95‰~+6.95‰之间,第二阶段δ¹⁸O_fluid分布在+1.08‰~ +1.38‰之间,而δD值变化较大,分布在-83‰~-33‰之间,因此第一阶段成矿流体为中温中低盐度的流体,来源以变质流体为主,可能有岩浆热液的叠加,第二阶段成矿流体为低温低盐度的流体,指示有大气水的混入。另外,黄垢矿区黄铁矿中的δ³⁴S值分布范围较广,为-15.79‰~+3.88‰;金坑矿区硫化物δ³⁴S值较为集中,为-5.02‰~+0.74‰。结合区域地层中S同位素组成与黄铁矿电子探针分析,认为载金硫化物硫源（δ³⁴S值接近零值）主要为深部岩浆,而不含金或含微量金的硫化物（δ³⁴S值为负值）来源于围岩地层。     

Solution for Flow Rates across the Wellbore in a Two-Zone Confined Aquifer

A closed-form solution for transient flow rates across the wellbore in a confined aquifer is derived from a two-zone radial ground-water flow equation subject to the boundary condition of keeping a constant head at the well radius. An aquifer may be considered as a two-zone system if the formation properties near the wellbore are significantly changed due to the well construction and/or well development. An efficient numerical approach is used to evaluate this newly derived solution. Values of the transient flow rate are provided in a tabular form and compared with those obtained by numerical inversion for the Laplace-domain solution. The results show that the two solutions are in good agreement. This newly derived solution can be used not only for predicting the transient flow rate across the wellbore but also for identifying the effects of a skin with a finite thickness on the estimation of transient flow rates in a ground-water system with two different formation properties.     

Evidence for a role of oxygen-derived free radicals and protein kinase C in nitrate tolerance

The anti-ischemic effects of organic nitrates are rapidly attenuated due to the development of nitrate tolerance. The mechanisms underlying this phenomenon likely involve several independent factors. As a vasodilator, nitroglycerin activates compensatory neurohumoral mechanisms such as the renin-angiotensin system and increases catecholamine and vasopressin levels, all of which may attenuate its vasodilator potency. Tolerance may be also due to the inability of the vessel to dilate after prolonged treatment with the nitrate. More recent experimental studies have challenged traditional tolerance concepts by demonstrating that tolerance is not associated with sulfhydryl group depletion, reduced nitroglycerin biotransformation, or desensitization of the target enzyme guanylyl-cyclase. Experimental and clinical observations suggest that tolerance may be the consequence of intrinsic abnormalities of the vasculature, including enhanced endothelial production of oxygen-derived free radicals secondary to an activation of NAD(P)H-dependent oxidases and an activation of PKC. Superoxide degrades nitric oxide derived from nitroglycerin (NTG) while C activation causes enhanced sensitivity of the vasculature to circulating neurohormones such as catecholamines, angiotensin II, and serotonin, all of which may compromise the vasodilator potency of NTG. Interestingly, these vascular consequences of in vivo NTG treatment such as superoxide production and PKC activation can be mimicked in vitro by incubating cultured endothelial and smooth muscle cells with angiotensin II. Furthermore, nitrate tolerance and rebound following sudden cessation of prolonged NTG therapy can be prevented by concomitant treatment with high-dose angiotensin-converting enzyme inhibition, angiotensin type 1 receptor blockade, or antioxidants such as hydralazine. Thus one can conclude that neurohumoral counterregulatory mechanisms such as increased circulating levels of angiotensin II may be at least in part responsible for tolerance mechanisms at the cellular level.     

Evidence for a recommended dietary allowance for vitamin C from pharmacokinetics: a comment and analysis

The current recommended dietary allowance (RDA) for vitamin C, as proposed by the Food and Nutrition Board/National Research Council in 1980 and reconfirmed in 1989, is 60 mg daily for nonsmoking adult males. Levine et al. [Levine, M., Conry-Cantilena, C., Wang, Y., Welch, R. W., Washko, P. W., et al. (1996) Proc. Natl. Acad. Sci. USA 93, 3704-3709], based on a study of vitamin C pharmacokinetics in seven healthy men, have now proposed that the RDA should be increased to 200 mg daily. I have examined, in brief, the experimental and conceptual bases for this new recommendation and its implications for public health and nutrition policy and programs. Using, for illustrative purposes only, data extracted from each of two recent dietary surveys of noninstitutionalized adult males living in households in the Netherlands and the United States, it is predicted that the prevalence of intakes inadequate to meet the individual's own requirement would be about 96% or 84%, respectively, if the criteria of adequacy used for derivation of the 200 mg RDA are accepted. Depending upon the particular average requirement value for ascorbic acid that might be derived from their data, the proposal by Levine et al. would mean a desirable increase in mean intakes in these two populations by as much about 2-to 3-fold. Hence, before an action of this kind is to be recommended, an answer must be sought to the question whether current experimental data including the criteria selected (saturation kinetics) are adequate to establish a new set of requirements for vitamin C, which then carry such profound policy implications. This will require critical assessment of all of the available evidence emerging from laboratory, clinical, and epidemiological studies to determine whether it provides a sufficient rationale for accepting criteria of vitamin C adequacy such as those proposed by Levine et al. and the requirement estimates so derived.