黄土的形成与气候旋回划分

根据黄土土壤特征的研究和黄土地层古土壤的识别和划分,结合磁化率测定,研究了黄土剖面冷干与温湿条件下发育的古土壤的分层和代表的气候旋回变化。资料表明,黄土具有土壤的结构和淀积成分,它是在相对冷干气候条件下发育的成熟的灰黄色古土壤,能够可靠地作为冷干气候的指示;250万年来的黄土地层至少可分为51层灰黄色古土壤与50层红褐色古土壤,代表了51个生物、气候、土壤旋回和亚旋回的变化。在50万年来的温湿气候阶段中,气候波动更频繁。     

西安南郊和陕北长武土壤CO2 释放量研究

本文根据NaOH溶液吸收CO2的方法,对西安南郊和陕北长武地区土壤CO2释放量进行了昼夜观测。观测结果表明,不同地区土壤CO2释放量存在差异,气候偏冷偏干地区土壤CO2 释放量较小,气候偏热偏湿地区土壤CO2释放量较大。陕北长武土壤CO2释放量变化再次证明,从当日早晨至次日早晨, CO2释放量具有由低变高再变低的规律; CO2释放量相对于大气温度的日变化具有滞后性,滞后时间为4～6小时;土壤CO2释放量白天较少,夜间较多; CO2释放量变化显示,在土层深厚的地区,土壤微生物夜间活动强度总体应比白天大。      

富县地区末次间冰期以来古气候环境的演变

研究剖面位于洛川源北部的富县县城东郊。剖面由第一层古土壤(S_1)、马兰黄土(L_1)和全新世古土壤(S_0)组成。孢粉分析结果表明,黄土地层中孢粉非常丰富,为恢复古植被与古气候提供了可靠依据。S_1的植被是以榛、菊、蒿为主的疏林草原,有亚热带树种出现,反映了末次冰期的温湿气候。L_1时主要为菊、蒿干草原,气候冷干,其间有四次乔木增多期,反映了末次间冰期中有四次间冰阶的相对温湿气候波动。近代耕土中为以松、藜、中华卷柏为主的森林草原,反映了全新世某个时期比较温凉干旱的气候。     

冰缘植被与第四纪冰川的探讨

关于我国第四纪冰川问题特别是华北地区的冰川问题,至今仍存在着激烈的争论。有的认为华北地区平原及山麓地带有冰川出现,有的认为仅在一定高度的山地有冰川出现,还有的认为山地也无冰川出现。其所以认识难以统一,与以往确定冰川的依据多限于沉积物和地貌有关。     

中国黄土环境研究的新进展

本文概述了中国黄土气候旋回划分，气候变化周期，黄土地层气候划分与深海沉积氧同位素曲线的对比，传统第四纪冰期划分与黄土地层气候旋回差异的原因，介绍了红褐色古土壤淀积层和古土壤类型研究的新成果，黄土形成与演变的新模型，评述了黄土石植被研究的新进展和今后黄土环境研究的趋势。     

黄土高原的演变

根据黄土高原古地理演变，黄土地层年代学和侵蚀期与堆积期的资料分析，我们得出黄土高原出现之前为红土高原，２５０万来的黄土高原可分三个阶段，第一阶段出现在２５０～１４０万年之间，为高原物质内部侵蚀循环期，第二阶段出现在１４０～０．０４万年之间，为高原物质侵蚀外流期，第三阶段出现在４千年以来，为高原植物加速侵蚀外流期，此外，本文还讨论了黄土高原未来发展趋势。     

The emergence of life from iron monosulphide bubbles at a submarine hydrothermal redox and pH front

Here we argue that life emerged on Earth from a redox and pH front at c. 4.2 Ga. This front occurred where hot (c. 150 degrees C), extremely reduced, alkaline, bisulphide-bearing, submarine seepage waters interfaced with the acid, warm (c. 90 degrees C), iron-hearing Hadean ocean. The low pH of the ocean was imparted by the ten bars of CO2 considered to dominate the Hadean atmosphere/hydrosphere. Disequilibrium between the two solutions was maintained by the spontaneous precipitation of a colloidal FeS membrane. Iron monosulphide bubbles comprising this membrane were inflated by the hydrothermal solution upon sulphide mounds at the seepage sites. Our hypothesis is that the FeS membrane, laced with nickel, acted as a semipermeable catalytic boundary between the two fluids, encouraging synthesis of organic anions by hydrogenation and carboxylation of hydrothermal organic primers. The ocean provided carbonate, phosphate, iron, nickel and protons; the hydrothermal solution was the source of ammonia, acetate, HS-, H2 and tungsten, as well as minor concentrations of organic sulphides and perhaps cyanide and acetaldehyde. The mean redox potential (delta Eh) across the membrane, with the energy to drive synthesis, would have approximated to 300 millivolts. The generation of organic anions would have led to an increase in osmotic pressure within the FeS bubbles. Thus osmotic pressure could take over from hydraulic pressure as the driving force for distension, budding and reproduction of the bubbles. Condensation of the organic molecules to polymers, particularly organic sulphides, was driven by pyrophosphate hydrolysis. Regeneration of pyrophosphate from the monophosphate in the membrane was facilitated by protons contributed from the Hadean ocean. This was the first use by a metabolizing system of protonmotive force (driven by natural delta pH) which also would have amounted to c. 300 millivolts. Protonmotive force is the universal energy transduction mechanism of life. Taken together with the redox potential across the membrane, the total electrochemical and chemical energy available for protometabolism amounted to a continuous supply at more than half a volt. The role of the iron sulphide membrane in keeping the two solutions separated was appropriated by the newly synthesized organic sulphide polymers. This organic take-over of the membrane material led to the miniaturization of the metabolizing system. Information systems to govern replication could have developed penecontemporaneously in this same milieu. But iron, sulphur and phosphate, inorganic components of earliest life, continued to be involved in metabolism.     

Evaluation of non-specific immune functions in dab,Limanda limanda L., following short-term exposure to sediments contaminated with polyaromatic hydrocarbons and/or polychlorinated biphenyls

Experimental exposure tanks were set up containing 'clean' marine sediment spiked with set doses of polyaromatic hydrocarbons (PAH), or polychlorinated biphenyls (PCB), or both. Reference tanks contained only 'clean' sediment. Female dab Limanda limanda L., exposed to these sediments for 7 days showed no differences in serum total protein concentration, serum lysozyme activity or body growth. Their kidney leucocytes were assayed for extracellular production of reactive oxygen species of the phagocytic respiratory burst. No significant differences in superoxide anion (O2-) production were found between fish exposed to the 'spiked' sediments and those on the 'clean' reference sediment. The production of hydrogen peroxide (H2O2) was, however, reduced in the fish held on the PAH and PAH/PCB spiked sediments. H2O2 levels for fish exposed to PCBs alone, did not differ significantly from those of control fish. Our results suggest that the decrease in H2O2 production was due to exposure to PAHs, rather than to PCBs.     

Effect of cadmium, copper and mercury on antioxidant enzyme activities and lipid peroxidation in the gills of the hydrothermal vent mussel Bathymodiolus azoricus

Metals are known to influence lipid peroxidation and oxidative status of marine organisms. Hydrothermal vent mussels Bathymodiolus azoricus live in deep-sea environments with anomalous conditions, including high metal concentrations. Although B. azoricus are aerobic organisms they possess abundant methano and thioautotrophic symbiotic bacteria in the gills. The enzymatic defences (superoxide dismutase (SOD), catalase (CAT), total glutathione peroxidase (Total GPx) and selenium-dependent glutathione peroxidase (Se-GPx)) and lipid peroxidation were determined in the gills of B. azoricus exposed to Cd (0.9 microM), Cu (0.4 microM) and Hg (0.1 microM) with different times of exposure. The experiments were performed in pressurized containers at 9+/-1 degrees C and 85 bars. Results show that vent mussels possess antioxidant enzymatic protection in the gills. Cd and Cu had an inhibitory effect in the enzymatic defence system, contrarily to Hg. These enzymatic systems are not completely understood in the B. azoricus, since reactive oxygen species might be produced through other processes than natural redox cycling, due to hydrogen sulphide and oxygen content present. Also the symbiotic bacteria may play an important contribution in the antioxidant protection of the gills.