Manganese flux from continental margin sediments in a transect through the oxygen minimum

The flux of manganese from continental margin sediments to the ocean was measured with a free-vehicle, benthic flux chamber in a transect across the continental shelf and upper slope of the California margin. The highest fluxes were observed on the shallow continental shelf. Manganese flux decreased linearly with bottom water oxygen concentration, and the lowest fluxes occurred in the oxygen minimum zone (at a depth of 600 to 1000 meters). Although the flux of manganese from continental shelf sediments can account for the elevated concentrations observed in shallow, coastal waters, the flux from sediments that intersect the oxygen minimum cannot produce the subsurface concentration maximum of dissolved manganese that is observed in the Pacific Ocean.     

Influences of dietary uptake and reactive sulfides on metal bioavailability from aquatic sediments

Understanding how animals are exposed to the large repository of metal pollutants in aquatic sediments is complicated and is important in regulatory decisions. Experiments with four types of invertebrates showed that feeding behavior and dietary uptake control bioaccumulation of cadmium, silver, nickel, and zinc. Metal concentrations in animal tissue correlated with metal concentrations extracted from sediments, but not with metal in porewater, across a range of reactive sulfide concentrations, from 0.5 to 30 micromoles per gram. These results contradict the notion that metal bioavailability in sediments is controlled by geochemical equilibration of metals between porewater and reactive sulfides, a proposed basis for regulatory criteria for metals.     

刚毛藻分解对荣成天鹅湖沉积物磷释放的影响

在荣成天鹅湖刚毛藻暴发和非暴发区域分别采集沉积物进行室内加藻模拟试验,定期监测上覆水的溶解氧(DO)、pH、化学需氧量(COD)和可溶性磷(SRP)等指标的变化,并分析了刚毛藻分解对沉积物磷释放的影响。结果表明,避光培养过程中,刚毛藻分解使上覆水体的DO含量大幅降低,形成厌氧环境(0~0.14 mg.L-1);COD含量则明显增加,各处理最大值变化在0.59~6.93 mg.L-1之间。刚毛藻分解可明显促进沉积物中磷的释放,培养期间上覆水SRP的含量大幅上升,变幅为0.01~1.51 mg.L-1;暴发区沉积物+10 g藻和沉积物+30 g藻处理的最大释磷量分别为沉积物处理的2.06倍和1.91倍。不同湖区沉积物磷的释放能力存在较大差异,暴发区沉积物的释磷量明显高于非暴发区,沉积物释放是前者上覆水磷含量增加的主要来源,而在非暴发区藻类分解释放的磷高于沉积物中释放的磷。     

速生杨木单板染色阻燃性能研究

为研究酸性染料和无机阻燃剂同步处理对杨木单板性能的影响,用酸性大红3R染料和BL-阻燃剂对杨木进行染色阻燃,采用单因素法,探讨染色阻燃工艺参数对单板上染率、色差、载药率和氧指数的影响。结果表明:随浸渍温度的升高,上染率和色差均呈先增大后减小趋势,载药率和氧指数增大;随浸渍时间的延长,上染率和色差呈增大趋势,载药率和氧指数先迅速后缓慢增加;随酸性大红3R浓度的增加,上染率和色差先增大后减小,载药率和氧指数呈先缓慢后迅速减小趋势;阻燃剂的添加促进了单板上染率,随阻燃剂浓度的增加上染率呈先增大后逐渐减小的趋势,色差逐渐增大,载药率和氧指数都增大。     

地表水体底泥中氮磷及重金属的释放规律研究

通过对地表水体底泥污染特性的分析,论明水体沉积物与水体之间具有复杂的迁移规律。分类介绍了影响水体底泥中氮磷及重金属释放的各种因素,主要分析了温度、pH值、溶解氧、沉积物形态、水体扰动的影响,认为影响释放的主导因素因地而异,指出开展污染底泥综合整治技术研究的重要性。     

Interstitial nitrate profiles and oxidation of sedimentary organic matter in the eastern equatorial atlantic

Pore-water nitrate concentrations in six pelagic eastern equatorial Atlantic cores increase from bottom water values (22 micromolar) to 40 micromolar at a depth of about 5 centimeters, then decrease to undetectable levels at depths as shallow as 40 centimeters. These nitrate concentrations and concentration gradients reflect zones of oxygen reduction, nitrate reduction, and sulfate reduction in the sediments. The estimated benthic flux of nitrate to the ocean from our data is much less than the total globalflux of nitrate to deep waters, even though these equatorial sediments underlie a productive upwelling zone. The estimated denitrification rate in our study area suggests that pelagic sediments may be important sites of marine denitrification.     

太湖沉积物耗氧速率空间异质性研究

沉积物耗氧速率(sediment oxygen demand,简称SOD)在综合评价水体水质和环境特征时是一个非常有用的参数,对分析水体氧收支平衡和评价水环境质量具有重要意义。采集了由太湖大浦沿岸到湖心及太湖南岸到湖心不同位点的太湖沉积物,采用微体积法研究了太湖沉积物SOD的空间异质性。结果表明:随着离湖岸距离的增加,沉积物SOD逐渐降低;沉积物SOD与沉积物粒度分布和间隙水APA呈极显著正相关(R2=0.867,P<0.01;R2=0.929,P<0.01),与沉积物APA呈负相关,但不显著(R2=-0.331,P>0.05),与有机物含量呈极显著负相关(R2=-0.794,P<0.01)。     

Hypoxia: effects on heart rate and respiration in the snapping turtle

In response to atmospheres containing decreasing amounts of oxygen, snapping turtles (Chelydra serpentina) maintained a fairly constant oxygen uptake. Their heart rate increased and the period of apnea between breathing cycles decreased. Small animals had a slightly greater mean uptake per gram than those five to ten times as large.     

Nonoxidative glucose consumption during focal physiologic neural activity

Brain glucose uptake, oxygen metabolism, and blood flow in humans were measured with positron emission tomography, and a resting-state molar ratio of oxygen to glucose consumption of 4.1:1 was obtained. Physiological neural activity, however, increased glucose uptake and blood flow much more (51 and 50 percent, respectively) than oxygen consumption (5 percent) and produced a molar ratio for the increases of 0.4:1. Transient increases in neural activity cause a tissue uptake of glucose in excess of that consumed by oxidative metabolism, acutely consume much less energy than previously believed, and regulate local blood flow for purposes other than oxidative metabolism.     

The Archean sulfur cycle and the early history of atmospheric oxygen

The isotope record of sedimentary sulfides can help resolve the history of oxygen accumulation into the atmosphere. We measured sulfur isotopic fractionation during microbial sulfate reduction up to 88 degrees C and show how sulfate reduction rate influences the preservation of biological fractionations in sediments. The sedimentary sulfur isotope record suggests low concentrations of seawater sulfate and atmospheric oxygen in the early Archean (3.4 to 2.8 billion years ago). The accumulation of oxygen and sulfate began later, in the early Proterozoic (2.5 to 0.54 billion years ago).     

微生物接种对生活垃圾堆肥生化特性的影响

以生活垃圾为原料,利用静态堆肥反应装置,在通风好氧条件下,研究了接种微生物堆肥过程中温度、耗氧速率、CO2释放率以及几种酶活性变化规律。结果表明,与普通堆肥法(CK)比较,接种微生物菌剂堆肥(CM),可明显加速堆肥升温过程,延长高温阶段(55℃以上)24 h;堆肥中前期CM处理耗氧速率及CO2释放率显著增大,其峰值分别是CK处理的1.25、1.24倍;与CK处理比较,CM处理堆肥过程中纤维素酶、蔗糖酶、多酚氧化酶活性峰值分别增加了8.77%、8.30%和22.36%。结果显示,接种微生物可以明显改善生活垃圾堆肥过程中的生化特性。     

Dechlorination of DDT by Aerobacter aerogenes

Dechlorination of DDT to DDD in higher animals requires the presence of molecular oxygen, but in microorganisms the presence of oxygen hinders dechlorination. In cell-free preparations of Aerobacter aerogenes, the use of selected metabolic inhibitors indicated that reduced Fe(II) cytochrome oxidase was responsible for DDT dechlorination. This finding may possibly explain. the persistence of DDT residues in soils and sediments.     

大型水生植物对太湖底泥磷释放的影响研究

通过对太湖流域常见3种水生植物(芦苇、苦草和茭白)根部底泥及无植物底泥进行磷释放特性模拟试验,讨论了pH值(分别为5、7、12)、温度(25℃、35℃)以及好氧(DO>8.0 mg.L-1)和厌氧(DO<1.0 mg.L-1)条件对磷释放强度的影响。结果表明,pH增大、温度升高、厌氧状态均可增加底泥磷释放,pH在弱酸至中性范围内底泥释磷量较小,酸性和碱性条件都有利于磷的释放,进一步分析了其中机理。从模拟试验结果来看,水生植物能在一定程度上降低湖泊底泥的总可溶性磷(TDP)含量,减少内源性磷释放,因而可供研究种植大型水生植物修复湖泊富营养化问题参考。     

Oxygen consumption in pelagic marine sediments

Measurements in the interstitial waters of pelagic red clay and carbonate ooze sediments in the central equatorial Pacific show that the dissolved oxygen content decreases with depth and levels off at nonzero values. The supply of reactive organic carbon introduced by bioturbation limits oxygen consumption at depth in the sediment. These gradients should produce diffusive fluxes across the sediment-water interface that average about 8.8 x 10(-14) mole per square centimeter per second or 0.08 milliliter per square meter per hour.     

Molecular fossil record of elevated methane levels in late Pleistocene coastal waters

Accumulating evidence suggests that methane has been released episodically from hydrates trapped in sea floor sediments during many intervals of rapid climate warming. Here we show that sediments from the Santa Barbara Basin deposited during warm intervals in the last glacial period contain molecular fossils that are diagnostic of aerobic and anaerobic methanotrophs. Sediment intervals with high abundances of these compounds indicate episodes of vigorous methanotrophic activity in methane-laden water masses. Signals for anaerobic methanotrophy in 44,100-year-old sediment are evidence for particularly intense methane emissions and suggest that the basin's methane cycle can profoundly affect oxygen budgets in the water column.     

Molybdenum isotope evidence for widespread anoxia in mid-Proterozoic oceans

How much dissolved oxygen was present in the mid-Proterozoic oceans between 1.8 and 1.0 billion years ago is debated vigorously. One model argues for oxygenation of the oceans soon after the initial rise of atmospheric oxygen approximately 2.3 billion years ago. Recent evidence for H(2)S in some mid-Proterozoic marine basins suggests, however, that the deep ocean remained anoxic until much later. New molybdenum isotope data from modern and ancient sediments indicate expanded anoxia during the mid-Proterozoic compared to the present-day ocean. Consequently, oxygenation of the deep oceans may have lagged that of the atmosphere by over a billion years.     

Late Precambrian oxygenation; inception of the clay mineral factory

An enigmatic stepwise increase in oxygen in the late Precambrian is widely considered a prerequisite for the expansion of animal life. Accumulation of oxygen requires organic matter burial in sediments, which is largely controlled by the sheltering or preservational effects of detrital clay minerals in modern marine continental margin depocenters. Here, we show mineralogical and geochemical evidence for an increase in clay mineral deposition in the Neoproterozoic that immediately predated the first metazoans. Today most clay minerals originate in biologically active soils, so initial expansion of a primitive land biota would greatly enhance production of pedogenic clay minerals (the "clay mineral factory"), leading to increased marine burial of organic carbon via mineral surface preservation.     

Late-Neoproterozoic deep-ocean oxygenation and the rise of animal life

Because animals require oxygen, an increase in late-Neoproterozoic oxygen concentrations has been suggested as a stimulus for their evolution. The iron content of deep-sea sediments shows that the deep ocean was anoxic and ferruginous before and during the Gaskiers glaciation 580 million years ago and that it became oxic afterward. The first known members of the Ediacara biota arose shortly after the Gaskiers glaciation, suggesting a causal link between their evolution and this oxygenation event. A prolonged stable oxic environment may have permitted the emergence of bilateral motile animals some 25 million years later.     

暗适应叶光诱导期间出现的光声瞬态研究初报

利用光声光谱技术可以精确研究暗适应叶在光诱导期间出现的放氧动态、光热动态、能量储存动态。用光声光谱技术测量了在非胁迫条件以及高CO2下暗适应叶在光诱导期间出现的光声动态,包括放氧动态,气体吸收动态,光热动态和能量储藏动态。研究发现放氧动态与叶绿素荧光曲线有一定关系。第一个放氧峰可能反映PSII的电子传递的瓶颈现象。一开始出现的能量储藏极小值可能反映了诱导期间PSI的环式电子传递或非线性电子传递。诱导期间高浓度CO2诱导产生巨大的气体吸收信号,可能各种类型的Mehler反应是其中的原因之一,另一个原因是CO2的迅速液化。     

凡纳滨对虾露天土池底泥硫化物含量及其与其他环境因子的关系

通过定期监测分析凡纳滨对虾露天养殖土池水化学指标和底泥硫化物(S~(2-))、单质硫(S~0)、总硫(TS)含量和动态变化特征,探讨其与溶解氧(DO)、p H、总磷(TP)、总氮(TN)和总有机碳(TOC)的相关性,为凡纳滨对虾的健康养殖和养殖塘底质的科学管理提供理论依据。结果如下:周边河道底泥中硫化物含量(18.13~232.56 mg/kg)和露天土池底泥中硫化物含量(0.31~5.86 mg/kg)都低于渔业沉积环境中硫化物的安全下限;养殖塘底泥S~0和TS含量分别是0.39~3.06 mg/kg和221~4421 mg/kg。S~(2-)和TS随养殖时间呈波浪式增加趋势,S~0含量箱型区间增减变化;土池底泥TS中0.12%~1.76%为S~(2-),0.12%~1.04%为单质硫;水源底泥TS中4.30%~17.85%为硫化物,0.09%~0.37%为单质硫;主要水化学指标符合凡纳滨对虾养殖需求,底泥中TOC与TN均随养殖时间波浪式累积,TP动态变化规律不明显;相关分析表明,底泥S~(2-)、TS与底泥中TOC、TN呈极显著正相关(P0.01),与DO、p H显著负相关。结果表明:残饵、代谢产物和生物尸体等虾塘有机质的累积,易造成大量氧气被消耗,从而导致低氧状态下底泥中硫化物含量增加。建议通过合理投饵、提高溶解氧含量、定时清淤等途径有效减少虾塘底质硫化物和有机质的含量。