Reprint of “Seasonal and daily variation of mercury evasion at coastal and off shore sites from the Mediterranean Sea”     

Maria E. Andersson  Katarina Gårdfeldt  Ingvar Wängberg  Francesca Sprovieri  Nicola Pirrone  Oliver Lindqvist 《Marine Chemistry》2007

Dissolved gaseous mercury (DGM) was measured continuously using two newly developed techniques and a manual technique. The continuous techniques were based on the equilibrium between the aqueous and gaseous phase (DGM = Hg_extr / H', Hg_extr is the measured mercury concentration in the gas phase, H' is the Henry's Law coefficient at the desired temperature). In order to calculate the annual mercury evasion from the Mediterranean Sea, diurnal and seasonal measurements of DGM, total gaseous mercury in air (TGM), water temperature and wind speed were performed. During August 2003, March–April 2004 and October–November 2004 measurements of these parameters were conducted on board the RV Urania. The continuous measurements of DGM showed a diurnal variation in concentration, at both coastal and off shore sites, with higher concentrations during daytime than nighttime. The concentration difference could be as large as 130 fM between day and night. The degree of saturation was calculated directly from the measurements, S = Hg_extr / TGM and was found to vary between the different seasons. The highest average degree of saturation (850%) and the largest variation in saturation (600–1150%) was observed during the summer. The spring showed the lowest variation (260–360%) and the lowest average degree of saturation (320%). The autumn also showed a large variation in saturation (500–1070%) but a lower average (740%) compared to the summer cruise. This might be explained by the temperature difference between the different seasons, since that parameter varied the most. The flux from the sea surface was calculated using the gas exchange model developed by Nightingale et al. [Nightingale, P.D., Malin, G., Law, C.S., Watson, A.J., Liss, P.S., Liddicoat, M.I., Boutin, J., Upstill-Goddard, R. C., 2000. In situ evaluation of air–sea gas exchange parameterization using novel conservative and volatile tracers. Global Biogeochemical Cycles, 14(1):373–387]. The evasion varied between the different seasons with the highest evasion during the autumn, 24.6 pmol m^− 2 h^− 1. The summer value was estimated to 22.3 pmol m^− 2 h^− 1 and the spring to 7.6 pmol m^− 2 h^− 1. Using this data the yearly evasion from the Mediterranean Sea surface was estimated to 77 tons.  相似文献   

Effects of periodic saturation on K0 for a sandstone-mudstone particle mixture     

Zhenfeng Qiu  Junjie Wang  Yulong Chen  Yang Yang  Yongsuo Li 《Marine Georesources & Geotechnology》2020,38(7):867-875

Abstract

Sandstone-mudstone particle mixture (SMPM) is one of the main materials, which has been widely used for filling in and around reservoirs for water conservation projects. During the periodic rising and falling of the water level, the fill material for the embankments, dam, and other waterfront features will also undergo drainage-saturation cycles. The deformation and coefficient of lateral pressure at rest K₀ may be affected by periodic saturation. In this study, a device is modified for testing the K₀ for gravel-soil under periodic saturation. In order to investigate the effects of periodic saturation on K₀, a series of experiments were performed for SMPM under different vertical stress and saturation cycling. K₀^N values of SMPM containing 20% mudstone particles under periodic saturation were obtained. The results shows that the K₀^N initially increased, but eventually reached a stable value with the increasing number of periodic saturation cycles. The magnitude of the coefficient increment was also found to be related to the stress condition. K₀^N is a logarithmic function of the saturation cycling time. By calculating K₀^N with the proposed empirical formula, the deformation and stress distribution of the SMPM filler in waterfront engineering works can be calculated with greater precision.  相似文献   

天然含水量对海底沉积物贯入阻力的影响     

崔高嵩  刘雁春  裴文斌 《海洋测绘》2005,25(6):51-53

研究浅海表层底质沉积物的天然含水量变化规律及其对海底沉积物贯入阻力的影响.对某浅海海域的72份表层底质沉积物样品的天然含水量测试和贯入阻力测定值进行了分析对比.天然含水量是影响海底表层沉积物贯入阻力的重要因素,沉积物天然含水量与贯入阻力之间具有较强的负相关性,沉积物天然含水量越大,贯入阻力越小.  相似文献   

The Effects of Zn, Mn, and Co Accumulation on Growth and Chemical Composition of Fucus vesiculosus L under Different Temperature and Salinity Conditions     

IVKA M. MUNDA  V. HUDNIK 《Marine Ecology》1988,9(3):213-225

Abstract. Combined effects of temperature, salinity, and metal enrichment (Zn, Mn, Co) on the growth rate and chemical composition of Fucus vesiculosus L. were studied in culture. Factorial combinations of two temperatures and three salinities were used. The results indicated that the accumulation of Zn and Mn into algal tissue was enhanced by dilution of the media, whereas Co accumulation exhibited maxima at the medium salinity. Zn accumulation was enhanced by temperature, while the opposite was true for Mn and Co.
In the presence of metals the usual dilution-induced changes in growth activity and chemical composition of Fucus plants were altered, while responses to the temperature factor remained unchanged. In diluted media, growth activity and mannitol content decreased along with a simultaneous increase of protein content. In the presence of Zn and Mn the mannitol content exhibited peaks at the medium salinity; in the presence of Co the dilution-induced pattern remained unchanged. Salinity-induced changes in growth and protein content were altered in the presence of metals. Maxima in growth rates were found at the medium salinity. Growth was higher in extremely diluted media than in scawater, indicating an inversion of responses to the salinity factor. Both the growth rate and mannitol content were lowest under the influence of Zn.  相似文献   

Gravitational Sedimentation Behavior of Sensitive Marine Ariake Clays     

Zhenshun Hong  Takehito Negami  Hailun Guo 《Marine Georesources & Geotechnology》2004,22(1):49-63

It has been well documented that natural marine Ariake clays are sensitive clays. In this study, extensive data of marine Ariake clays are obtained to investigate the gravitational compression behavior for sensitive clays. Analysis results indicate that the compression behavior of remolded Ariake clays is not different from that of other remolded/reconstituted soils. But natural Ariake clays do not follow the gravitational compression pattern reported by Skempton (1970) for natural sedimentary soils. At a given value of effective overburden pressure, the void ratios of natural Ariake clays are almost independent of liquid limits. Most natural Ariake clays lie above the sedimentation compression line proposed by Burland (1990). When the liquid limit is larger than 90% and the ratio of natural water content over liquid limit ranges 0.8-1.1, the natural Ariake clays lie around the sedimentation compression line. In addition, the natural Ariake clay with higher value of the ratio of natural water content over liquid limit lies above the natural Ariake clay with lower value of the ratio of natural water content over liquid limit. Salt removal is the most probable cause for such a phenomenon.  相似文献   

黄河三角州沿岸及相邻渤海海域碳酸盐研究(英文)   总被引：2，自引：0，他引：2  

杨作升  王兆祥  瞿建忠  郑爱芬 《中国海洋大学学报(自然科学版)》1989,(3)

对黄河三角州陆地上河道,河口、潮间带及毗邻渤海海域沉积物中的碳酸盐含量作了分析,在此基础上划分出含量不同的沉积区和亚区。沉积区的划分和其物源有十分良好的对应关系,同一沉积区内的亚区则主要和粒度有关,从而间接反映了水动力环境与生物作用的控制性影响。黄河口沉积物中碳酸盐含量与粒度成反比,其他物源的沉积物则各不相同。黄河口及邻近渤海海域中粘土粒级和碳酸盐含量等值线反映出黄河细粒级沉积物扩散的方向、强度和范围。海洋生源沉积是影响渤海东部和中部沉积物中碳酸盐含量分布的主要因素。  相似文献   

台湾增生楔天然气水合物的地震特征   总被引：4，自引：1，他引：4  

丁巍伟  陈汉林  王渝民  杨树锋  吴能友 《海洋与湖沼》2006,37(1):90-96

通过对南海973航次在该区域的多道地震剖面的分析,结合该区域的地质背景,认为台湾增生楔具有天然气水合物存在和分布的地球物理特征,在地震剖面上出观海底反射层(BSR)、振幅空白(BZ)、极性反转等地震识别标志。BSR所在区域位于南海向菲律宾海板块俯冲的增生楔上,南海新生代沉积不仅提供了富含有机质的丰富物源,而且类似于活动大陆边缘的构造体系又为天然气水合物的形成提供了良好的条件。  相似文献   

Physical control of sediment carbon content in an estuarine tidal flat system (Nanakita River, Japan): A mechanistic case study     

Takashi Sakamaki  Osamu Nishimura 《Estuarine, Coastal and Shelf Science》2007,73(3-4):781-791

Temporal variations in sediment carbon content were tracked by sampling every 2 weeks for 6 to 33 months at 6 tidal flat stations with different carbon content levels (0.05–1.64%) in a single estuary. Three temporal series of current velocity at 5 cm above the sediment were also obtained. Non-cohesive and cohesive sediment stations differed in patterns of temporal variation in sediment carbon content, suggesting the difference in processes controlling sediment carbon content. In the stations of non-cohesive sandy sediment with relatively low carbon content (0.05–0.15%), sediment carbon content fluctuated within ranges specific to each station. In these stations, current velocity data suggested that frequency of sand resuspension washing out sediment carbon controls sediment carbon content level. In the stations of cohesive sediment with relatively high carbon content (0.77–1.64%), sediment carbon contents showed some unusual upward and downward peaks, recovered to usual levels specific to the stations, and was always kept higher than that in the non-cohesive sediment stations. We speculate that in the cohesive sediment stations, sand inputs may significantly control processes establishing the consolidated sediments with various carbon content levels. Spatial transitions from non-cohesive to cohesive sediments and from low to high sediment carbon contents likely occur as sand resuspension at spring tides become more irregular and less frequent. Based on these results, conceptual models describing physical processes controlling sediment carbon content at the studied stations were proposed.  相似文献   

Strength Sensitivity of Marine Ariake Clays     

Zhenshun Hong  Songyu Liu  Takehito Negami 《Marine Georesources & Geotechnology》2005,23(3):221-233

Natural Ariake clays are characterized by high sensitivity. In this study, the mechanism and the factors controlling undrained shear strengths of both undisturbed and remolded Ariake clays are discussed. A series of unconfined compressive tests were performed on undisturbed samples of natural Ariake clays. The remolded undrained shear strength is predicted using a quantitative expression derived from extensive data of remolded undrained shear strength for a number of soils compiled from resources in the literature. The sensitivity of natural Ariake clays derived from the ratio of half of unconfined compressive strength for undisturbed samples to remolded undrained shear strength is found to be affected by both natural water content and normalized water content that is defined as the ratio of natural water content to liquid limit. The smaller the natural water content, the higher the sensitivity is at the same normalized water content. At the same natural water content, the larger the normalized water content, the higher the sensitivity is.  相似文献   

海水及天然水中微量碘离子快速测定法的研究     

崔仙舟  王中柱 《海洋与湖沼》1995,26(6):673-677

研究用气相色谱测定海水及天然水中微量碘离子含量的快速分析方法，确定了最佳条件。水样经酸化后，用Ｋ２Ｃｒ２Ｏ７将碘离子氧化成碘，再与丁酮反应的１０ｍｉｎ，生成磺代丁酮，用环己烷萃取后，用气相色谱仪的电子捕获检测器测定其含量。于１９９１年６月，用此法测定青岛胶州湾沿岸海水及某些河口水样，证明该方法简便、快速。  相似文献