Distribution and sources of organic carbon, nitrogen and their isotopes in sediments of the subtropical Pearl River estuary and adjacent shelf, Southern China

The isotopic composition (δ¹³C and δ¹⁵N) and organic carbon (OC) and total nitrogen (TN, organic plus inorganic) content of 37 carbonate-free surficial sediments of the subtropical Pearl River estuary and the adjacent shelf of South China Sea (SCS) was determined. The δ¹³C values indicate that the sediment organic material is a mixture from two sources, terrestrial and marine. Several of the sediments have extremely low (< 4) OC / TN ratios, which could be due to low OC contents and/or to a significant fraction of the TN present as inorganic nitrogen adsorbed on clays. In general, the spatial patterns of OC, TN, δ¹³C and δ¹⁵N are similar. Values are low at the river mouth and on the western coast, suggesting proportionally greater accumulation of terrestrial particulate organic matter relative to marine phytodetritus, which is limited by low productivity in the turbid plume of the Pearl River. Algal-derived organic carbon (al-OC) content is estimated to be low (≤ 0.06%) at the river mouth and higher (up to 0.57%) on the adjacent inner shelf based on a mixing model of end members.     

Incorporation of aged dissolved organic carbon (DOC) by oceanic particulate organic carbon (POC): An experimental approach using natural carbon isotopes

Incorporation of ¹⁴C-depleted (old) dissolved organic carbon (DOC) on/into particulate organic carbon (POC) has been suggested as a possible mechanism to explain the low Δ¹⁴C-POC values observed in the deep ocean [Druffel, E.R.M., Williams, P.M., 1990. Identification of a deep marine source of particulate organic carbon using bomb ¹⁴C. Nature, 347, 172–174.]. A shipboard incubation experiment was performed in the Sargasso Sea to test this hypothesis. Finely ground dried plankton was incubated in seawater samples from the deep Sargasso Sea, both with and without a biological poison (HgCl₂). Changes in parameters such as biochemical composition and carbon isotopic signatures of bulk POC and its organic compound classes were examined to study the roles of sorptive processes and biotic activity on POC character. Following a 13-day incubation, the relative abundance of the acid-insoluble organic fraction increased. Abundances of extractable lipids and total hydrolyzable amino acids decreased for both treatments, but by a greater extent in the non-poisoned treatment. The Δ¹⁴C values of POC recovered from the non-poisoned treatment were significantly lower than the value of the unaltered plankton material used for the incubation, indicating incorporation of ¹⁴C-depleted carbon, most likely DOC. The old carbon was present only in the lipid and acid-insoluble fractions. These results are consistent with previous findings of old carbon dominating the same organic fractions of sinking POC from the deep Northeast Pacific [Hwang, J., Druffel, E.R.M., 2003. Lipid-like material as the source of the uncharacterized organic carbon in the ocean? Science, 299, 881–884.]. However, the Δ¹⁴C values of POC recovered from the poisoned treatment did not change as much as those from the non-poisoned treatment suggesting that biological processes were involved in the incorporation of DOC on/into POC.     

长牡蛎死因初探

本文对广西北海市海涂养殖的长牡蛎大量死亡的原因作了研究。电镜检测结果表明，在其外套膜、肝脏和中肠组织已吸入与积累了大量的直径为０．１～１．１０μｍ的球状有机化合物，未见微生物病原体感染，故该市海涂长牡蛎大量死亡的原因是其体内积累了大量的球状有机污染物而严重中毒引起的。     

波浪作用下近岸区污染物输移扩散的数学模型及其实验验证

在近岸缓坡浅水海岸,波浪破碎产生沿岸流是近岸海域流场的重要组成部分,它对污染物输移扩散规律的影响重大,在高阶近似抛物化缓坡方程求解大面积波浪场基础上,建立了波浪作用下污染物输移扩散数学模型.计算结果与不同坡度均匀斜坡地形上具有不同波高、周期的规则波及不规则波浪作用下污染物输移扩散实验结果进行了比较,分析了各种因素对波浪作用下沿岸流分布规律影响,所得结论认为地形坡度及入射波高对污染物输移扩散的影响较大,波浪作用将使缓坡海滩上污染物的输移扩散平行岸线方向.     

Depositional and palaeoenvironmental variation of lower Turonian nearshore facies in the Bohemian Cretaceous Basin,Czech Republic

Dark grey strata belonging to the basal horizons of the Bílá Hora Formation (lower Turonian) were exposed during quarrying at the locality of Plaňany (Bohemian Cretaceous Basin). Based mainly on quarry maps, the early Turonian rocky bottom was reconstructed in the area of about 14,800 m². Two sedimentologic and palaeoecological settings were recognized in the area. Dark grey deposits form part of the first setting, representing a fill of large and deep depressions on the northern foot of the Plaňany elevation. The second setting with a phosphatic lag is located on the elevated part of the area. Dark grey sedimentation belongs to the UC6a and particularly to the UC6b nannoplankton zones. During the latter zone the dark sedimentation passed upwards into light siltstones. The enrichment of C_org and S, clay minerals with an important kaolinite peak, formation of framboidal pyrite and the enrichment of macrofauna and phosphatic particles are characteristic of the basal portions of the dark deposits. The sulphate reduction zone is suggested for this sedimentary environment. In the associations of phosphatic particles, shark coprolites, faecal pellets and sponge fragments prevail. No phosphatic lag is developed. On the other hand, the phosphatic lag directly overlying the Cenomanian relics is most characteristic of the second setting. This lag is a product of sedimentary condensation, characterized by a long-lasting concentration of phosphatic particles and phosphogenesis, accompanied by encrustation of closely adjacent free rock surfaces by a faunal community with Terebella. Additional biostratigraphic data presently contributed to a proposed correlation of both settings. Micropalaeontological data (foraminifera, palynomorphs, nannoplankton) indicate that the phosphatic lag and basal dark grey deposits may be approximately coeval. The stagnant depositional conditions with only very slow sea-level rise are thought to have lasted for a relatively long period that includes a significant part of the Whiteinella archaeocretacea Zone (lowermost Turonian). In elevated parts, condensation could proceed under conditions of prevailingly weak currents and strong oxidation of organic matter, while decomposition of organic matter was probably very slow and incomplete in depressions below the elevation. The sedimentary condensation in both settings is highlighted by the remarkable formation of abundant glauconite in local deposits.     

Numerical characterization of dispersion coefficients by meshless‐based inverse analysis

This study presents the preliminary development of a meshless‐based indirect inverse analysis. Two goals are desired to be attained: (a) identifying fewer quantities in an indirect inverse analysis and (b) getting the interpolation results of spatial variation of a quantity insensitive to the replacement of one or few interpolation points with other points. This idea is illustrated by modifying a meshless local Petrov‐Galerkin (MLPG) formulation of a two‐dimensional (2D) contaminant transport problem under the concept of boundary control. Thus, dispersion coefficients to be identified are solved from measured or prescribed pollutant concentrations. A field problem is introduced to test the performance of resulting meshless‐based indirect inverse analysis procedure. This test finds a major motive and a minor one for performing a meshless‐based indirect inverse analysis. The major motive is attaining the aforementioned Goal (b), while the above‐mentioned Goal (a) is the minor motive. In conclusion, the development of a meshless‐based indirect inverse analysis procedure can be a valuable application of the MLPG method. Copyright © 2010 John Wiley & Sons, Ltd.     

2D-Cell Experiment on Methyl Tert-Butyl Ether Transport in Saturated Zone of Groundwater

As an additive of gasoline,methyl tert-butyl ether(MTBE)has a higher solubility in water,which is about 20 times as high as that of benzene.This characteristic results in MTBE dissolving out of the gasoline into the soil and groundwater.Due to relative unique physicochemical behavior of MTBE it would be an ideal candidate for use in environmental forensic investigations.In order to study the transport and distribution of MTBE in saturated zone of ground water,a two-dimensional experimental cell was setup to simulate the real environment of the groundwater flow.The effects of soil and groundwater flow velocity on the MTBE transport were investigated.The results show that the mobile distance of MTBE in vertical direction was smaller than that in horizontal direction paralleling with the groundwater flow.Because the main dynamics of groundwater flow direction was convection and dispersion,the movement of MTBE is also diffusion in the vertical direction.In addition,the transport of MTBE was more quick in high permeability porous media,and the increase of groundwater flow velocity can accelerate the MTBE plume de-velopment,but the irregularity and randomness of the plume are enhanced synchronously.These research results can give some helps for the investigation of MTBE movement in the groundwater,also can make some references for other petroleum contamination behavior.     

有机污染物在含土工膜复合隔离墙和含水层系统的运移半解析模型

为评估土工膜与土-膨润土组成的复合隔离墙对有机污染物的防污性能,建立了污染物在源区域发生降解扩散时透过复合隔离墙的一维瞬态扩散模型。通过拉普拉斯变换和Talbot数值反演获得了模型解。第3类入流边界条件下,考虑源区的扩散和降解时,第1类隔离墙(土工膜/土-膨润土)和第2类隔离墙(土-膨润土/土工膜/土-膨润土)100 a的击穿浓度分别较源浓度恒定时减少了59%和53%。由于假设土工膜渗透系数高于10^–12 m/s,污染物在复合隔离墙中的对流作用不能忽略,因此,采用第2类复合隔离墙使土-膨润土能更好地发挥主导隔离作用。将土工膜的渗透系数从10^–10 m/s减少到10^–16 m/s,第1类复合隔离墙的击穿时间从26 a增加到188 a,第2类复合隔离墙的击穿时间从32 a增加到81 a。利用抽水井调整墙体内外为负水头差及提高源区的污染物降解能力,可使隔离墙的防污性能得到较大提升。     

Organic matter accumulation of Late Ordovician sediments in North Guizhou Province,China: Sulfur isotope and trace element evidences

The organic-rich Upper Ordovician sediments (Wufeng and Guanyinqiao Formations) on the Yangtze platform are considered to be one of the main source rocks. Here we present geochemical proxies, including redox indicator (S/C ratios and sulfur isotopes) and productivity indices (TOC, Mo and Ba contents), from Nanbazi section in North Guizhou province, South China, in order to investigate the mechanism of organic matter accumulation. The geochemical data suggest a stagnant and anoxic environment predominated the Yangtze Sea during the Wufeng period, whereas ventilated and oxygenated marine conditions pervaded the Yangtze Sea during the Guanyinqiao period. Variations in the concentration of TOC, Mo and Ba indicate that higher organic carbon export in the Wufeng intervals than those in the Guanyinqiao intervals. These variations in redox and productivity during the late Ordovician were associated with different mechanisms and forcing processes. The abrupt change from anoxic to oxygenated condition at the beginning of the Guanyinqiao was concomitant with the global glacial period, likely resulted from the glacio-eustatic sea-level fall and subsequent circulation of cold, dense oxygenated waters upon the shelf seabed. The productivity variations were related to the change of nutrient supply, which is consistent with volcanic activities and runoff to the Yangtze Sea. Redox changes, together with primary productivity fluctuations could have played a significant role on the variation of organic matter accumulation during the late Ordovician in South China.     

Bioaccumulation and enantiomeric profiling of organochlorine pesticides and persistent organic pollutants in the killer whale (Orcinus orca) from British and Irish waters

Concentrations and enantiomeric profiles for a range of organochlorine compounds are reported in blubber samples from a number of individual killer whales (Orcinus orca) from British and Irish waters. Elevated contaminant levels and enriched isotopic ratios were determined in one individual whale sampled in the Scottish Western Isles compared to the others suggesting marine mammal based dietary influences. The potential application of isotopic ratios to model contaminant uptake, enantioselective enrichment and accumulation is demonstrated. Data are presented which provide information on enantioselective enrichment factors (EFs) for o,p'-DDT, alpha-HCH and toxaphene congeners CHB26 and CHB 50. This dataset further improves the current database on reported levels of a number of contaminants and provides additional background information on potential metabolic processes in killer whales from British and Irish waters.