大河影响下的边缘海沉积有机碳输运与埋藏及再矿化研究进展

大河影响下的边缘海是陆源输入物质的主要储库,也是有机碳埋藏和再矿化的主要场所,在全球碳的生物地球化学循环中有着重要作用。从有机碳的输运、埋藏和再矿化等方面综述了大河影响下的边缘海沉积有机碳生物地球化学研究的最新进展。研究表明,有机碳的来源、组成、粒径和密度分布等显著影响着有机碳的分布特征和归宿,大河影响下的边缘海中移动泥等特殊沉积环境在有机碳的输运、埋藏和再矿化分解等方面发挥了独特的作用;微生物分解作用则是边缘海沉积有机碳,特别是难降解陆源有机碳发生分解的重要因素。综合运用分子生物学、有机地球化学、生物地球化学等多学科研究手段,深入研究特定微生物、浮游生物功能类群等在大河影响下的边缘海沉积有机碳生物地球化学过程中的作用,将极大地丰富对河口和陆架边缘海生源要素生物地球化学循环的认识。     

九龙江口水体中1995年有机物的转移

1995年3个航次调查研究结果表明,九龙江口水体总有机物的含量受悬浮物含量控制。在S＜5的低盐度区,悬浮泥沙和有机物产生明显的絮凝沉降;在S＞5的广阔海域,它们的迁移接近于理想混合。估算得出九龙江河流的入海通量约：悬浮泥沙为9．8×105t／a;总COD为3．2×104t／a,其中溶解态COD为2.1×104t／a,约占2／3,为水体有机物的主要形态,如换算为溶解有机碳,则DOC的平均通量为3．2×104t／a。     

Methylmercury production in sediments of Chesapeake Bay and the mid-Atlantic continental margin

Methylmercury (MeHg) concentration and production rates were studied in bottom sediments along the mainstem of Chesapeake Bay and on the adjoining continental shelf and slope. Our objectives were to 1) observe spatial and temporal changes in total mercury (HgT) and MeHg concentrations in the mid-Atlantic coastal region, 2) investigate biogeochemical factors that affect MeHg production, and 3) examine the potential of these sediments as sources of MeHg to coastal and open waters. Estuarine, shelf and slope sediments contained on average 0.5 to 1.5% Hg as MeHg (% MeHg), which increased significantly with salinity across our study site, with weak seasonal trends. Methylation rate constants (k_meth), estimated using enriched stable mercury isotope spikes to intact cores, showed a similar, but weaker, salinity trend, but strong seasonality, and was highly correlated with % MeHg. Together, these patterns suggest that some fraction of MeHg is preserved thru seasons, as found by others [Orihel, D.M., Paterson, M.J., Blanchfield, P.J., Bodaly, R.A., Gilmour, C.C., Hintelmann, H., 2008. Temporal changes in the distribution, methylation, and bioaccumulation of newly deposited mercury in an aquatic ecosystem. Environmental Pollution 154, 77] Similar to other ecosystems, methylation was most favored in sediment depth horizons where sulfate was available, but sulfide concentrations were low (between 0.1 and 10 μM). MeHg production was maximal at the sediment surface in the organic sediments of the upper and mid Bay where oxygen penetration was small, but was found at increasingly deeper depths, and across a wider vertical range, as salinity increased, where oxygen penetration was deeper. Vertical trends in MeHg production mirrored the deeper, vertically expanded redox boundary layers in these offshore sediments. The organic content of the sediments had a strong impact on the sediment:water partitioning of Hg, and therefore, on methylation rates. However, the HgT distribution coefficient (K_D) normalized to organic matter varied by more than an order of magnitude across the study area, suggesting an important role of organic matter quality in Hg sequestration. We hypothesize that the lower sulfur content organic matter of shelf and slope sediments has a lower binding capacity for Hg resulting in higher MeHg production, relative to sediments in the estuary. Substantially higher MeHg concentrations in pore water relative to the water column indicate all sites are sources of MeHg to the water column throughout the seasons studied. Calculated diffusional fluxes for MeHg averaged  1 pmol m^− 2 day^− 1. It is likely that the total MeHg flux in sediments of the lower Bay and continental margin are significantly higher than their estimated diffusive fluxes due to enhanced MeHg mobilization by biological and/or physical processes. Our flux estimates across the full salinity gradient of Chesapeake Bay and its adjacent slope and shelf strongly suggest that the flux from coastal sediments is of the same order as other sources and contributes substantially to the coastal MeHg budget.     

Skeletal linear extension rates of the foliose scleractinian coral Merulina ampliata (Ellis & Solander, 1786) in a turbid environment

Skeletal linear extension rates of a foliaceous, IndoPacific, skiophilous, heterotrophic, scleractinian Merulina ampliata (Ellis & Solander 1786) were obtained along a sediment/nutrient load gradient at the southern islands of Singapore. Measurements were made during November 1999– November 2000 using the alizarin red‐S staining technique. Suspended particulate matter concentration (r²_adj = 0.76), turbidity (r²_adj = 0.59), the organic content of suspended sediments (r² = 0.50), and nitrite‐nitrate concentration (r²_adj = 0.50) were significant predictors of the skeletal linear extension rate of M. ampliata. Maximum linear extension growth rates of M. ampliata (mean ± SD: 1.43 ± 0.67–3.26 ± 0.59 cm·year^?1) were comparable to 15‐year‐old accounts at the same research sites, indicating adaptation to low‐light, high‐sediment waters.     

Photochemical production of molecular hydrogen in lake water and coastal seawater

Samples of lake water and coastal seawater from Nova Scotia, Canada, were irradiated with natural or artificial sunlight to investigate the potential for photochemical hydrogen production. Hydrogen photo-production was observed in all natural water samples. Rates of hydrogen formation were highest in coloured lake water (range: 98–163 pmol L^− 1h^− 1) and lower in seawater (range: 19–45 pmol L^− 1 h ^− 1). Dilutions of the most highly coloured lake sample (Kejimkujik Lake) showed a positive linear relationship between H₂ production rates and CDOM concentration. Photo-production rates normalised to UV absorption coefficients at 350 nm indicated that the photochemical efficiency of hydrogen formation varied between samples, perhaps due to differences in the CDOM composition. Photochemical hydrogen formation was also seen in solutions of syringic acid and acetaldehyde: two low-molecular-weight carbonyl compounds found in natural waters. Photochemistry may therefore offer least a partial explanation for the persistently high levels of hydrogen observed in the low-latitude surface ocean.     

威海市褚岛北部海域CDOM和COD分布特征遥感分析

根据2017年7月和9月在山东威海褚岛北部海域现场测量的COD_(Mn)(Chemical oxygen demand)值和水体表观光学量,结合COMS(Communication,OceanMeteorological Satellite)上搭载的传感器GOCI(Geostationary Ocean Color Imager)所提供的有色可溶性有机物(Chromophoric dissolved organic matter,CDOM)产品,利用星地同步观测数据对现有的基于遥感反射比反演CDOM的模式进行验证,确定适合该海域的CDOM浓度遥感反演模式;通过对测试海域化学需氧量与遥感反演的水体CDOM浓度相关性分析,建立利用CDOM反演COD_(Mn)的遥感模式,并将该模式应用于测试海域LANDSAT 8/OLI(Operational Land Imager)遥感图像上,获取该海域COD_(Mn)浓度专题图,基于这些专题图分析了测试海域COD_(Mn)时空分布特征。结果表明:(1)基于GOCI产品的CDOM浓度值随时间和站点动态变化大,离岸越近数值越高,同一地点水体前后相差近1 h的数值变化也较大;(2)基于LANDSAT 8/OLI遥感数据反演的COD_(Mn)浓度时间动态变化大,总体来看褚岛附近水体的COD_(Mn)含量相对较低,褚岛以北海域水体COD_(Mn)含量有所增加,褚岛西侧水体的COD_(Mn)含量较东侧水体COD_(Mn)含量来说整体偏高。     

Longitudinal and depth variation of bacterioplankton productivity and related factors in a temperate estuary

Bacterioplankton productivity (BP) spatial variation was investigated in relation to potential resources, including primary productivity and dissolved organic matter, in the micro-tidal Neuse River–Pamlico Sound estuarine system, North Carolina, USA. Estuarine BP was predicted to correlate with the trophic gradient, decreasing along the salinity gradient in parallel with the decrease in organic matter and primary productivity. This prediction was tested over four years at spatial scales ranging from kilometers to meters along the riverine axis and with depth. The general pattern of BP across the salinity gradient was unimodal and matched the phytoplankton patterns in peak location and variability. Peak locations varied with discharge, especially in 2003 when above average discharge moved peaks downstream. Spatial coherence of BP with other variables was much less at short time scales. The effect of temperature, nutrients, and phytoplankton on BP varied by location, especially fresh versus brackish stations, although only temperature explained more than 20% of the BP variation. Depth variation of BP was as great as longitudinal variation and bottom samples were often higher than surface. BP was strongly correlated with particulate organic carbon at the pycnocline and bottom, highlighting the importance of particulate matter as a resource. Station-averaged BP and phytoplankton data corresponded well with two published meta-analyses, although the offset of the freshwater station suggested longitudinal differences in community composition or resource availability.     

赤道东北太平洋沉积物中生物钡的分布特征

分析了赤道东北太平洋海域沉积物中Ba、Ti、Al和有机碳(Corg)的含量。研究表明,研究区沉积物中钡为0.198%~0.792%;采用标准陆源物质扣除法获得的生物钡(Babio)的含量为0.162%~0.764%,占沉积物中总钡含量的81.6%~96.5%,平均为88.7%,其在沉积物中的分布表现为上部一致,下部变化较大;有机碳(Corg)的含量为0.18%~0.58%,并表现为随沉积物深度的增加而降低。沉积物中Babio/Ti的比值表现为东区高于西区,且向高纬度降低的特点,而沉积物中Corg/Ti和Babio/Ti则表现为负相关关系,表明研究区沉积物中钡可能和上层海洋生产力的相关性不明显。     

柴达木盆地第三系咸水湖相生油岩古沉积环境地球化学特征

在系统分析柴达木盆地西部第三系咸水湖相生油岩样品的微量元素、有机物、粘土矿物组成的基础上,揭示了研究区生油岩的无机元素和有机质组成特征;并结合沉积环境的无机与有机地球化学指标,重建了生油岩沉积时的古沉积环境。生油岩的B、Cl-及伽玛蜡烷含量表明,沉积时的水介质条件是半咸水—咸水环境,并伴随湖盆沉积中心北迁过程各层位地层的盐度发生规律性时空]化;生油岩的Fe2 /Fe3 、S2-、Pr/Ph比值、藿烷碳数分布模式及黄铁矿含量反映其沉积时的沉积环境为强还原性;粘土矿物组合特征及含量揭示这些生油岩的沉积相带介于中心咸湖相和边缘咸湖相之间。