Time filter

Source Type

Liu F.,Sun Yat Sen University | Niu L.,Sun Yat Sen University | Chen H.,Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering | Li P.,Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering | And 2 more authors.
Marine Pollution Bulletin | Year: 2017

The behaviours of PAHs (containing 2-6 aromatic rings) in the Pearl River estuary were examined each month in 2011. This study was designed to investigate the abundance of 16 priority PAHs and their response to the seasonal dynamics of anthropogenic activities and hydrological cycles. Monthly mean concentrations of ∑16PAHs in water and suspended particulate matter (SPM) were 88.31ng/L and 252.31ng/L respectively, with higher concentrations in the wet season (April to September). Heavy precipitation in the wet season resulted in relatively increased PAH input via riverine discharges and atmospheric deposition. Seasonal variations in suspended sediment concentration (SSC), temperature and salinity have considerably affected the PAH phase association. Higher SSC in the wet season contributed to higher concentration of the PAHs in SPM, and higher temperature and lower salinity facilitated desorption from SPM. The PAH sources were largely attributed to vehicular emissions, coal combustion and coke ovens. © 2017 Elsevier Ltd.

Gong W.,Sun Yat Sen University | Gong W.,Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering | Shen J.,Virginia Institute of Marine Science
Continental Shelf Research | Year: 2011

The increase of salt intrusion in recent years in the Modaomen Estuary, one of the estuaries of the Pearl River Delta in China, has threatened the freshwater supply in the surrounding regions, especially the cities of Zhongshan, Zhuhai in Guangdong Province and Macau. A numerical modeling system using nested grids was developed to investigate the salt transport mechanisms and the response of salt intrusion to changes in river discharge and tidal mixing. The steady shear transport induced by estuarine circulation reaches maximum and minimum, respectively, during neap and spring tides, while the tidal oscillatory transport shows an opposite pattern. The net transport is landward during neap tides and seaward during spring tides. The salt intrusion length responding to constant river discharges generally follows a power law of -0.49. The dependence of salt intrusion on tidal velocity is less than that predicted by theoretical models for exchange flow dominated estuaries. The response of salt intrusion to change in tidal velocity depends largely on river discharge. When river flow increases, the impact of tidal velocity increases and the phase lag of response time decreases. The asymmetries of salt intrusion responding to increasing and decreasing river discharge (tidal velocity) are observed in the estuary. © 2011 Elsevier Ltd.

Lu Y.,Sun Yat Sen University | Sun X.,Sun Yat Sen University | Sun X.,Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering | Lin Z.,Sun Yat Sen University | And 4 more authors.
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2015

Cold-seep carbonates are precipitated under high alkalinity conditions created by the anaerobic oxidation of methane in cold-seep sites. Multiple Ca-Mg-carbonate phases are identified, including aragonite, low-Mg calcite (LMC), high-Mg calcite (HMC), protodolomite, and dolomite. These phases result from different conditions that are related with cold-seep activities. Here, we report on the relationship between the Ca-Mg-carbonate phases and the cold-seep status. Authigenic carbonates were sampled from northern slope of South China Sea. Carbon isotopic compositions of samples from Shenhu area are lower than -40‰, indicating methane-derived carbon. The δ13C values of samples from Southwest (SW) Taiwan area range from ~-30‰ to ~-20‰, which is the result of the mixture of methane carbon and seawater carbon. Carbonate phases were identified according to the composition and structure results. Samples from Shenhu area are composed of protodolomite and HMC. Three zones were discovered from the center to the rim of the cross-section of the tube-like sample from SW Taiwan area. From the external to the internal zones, the carbonate phases are HMC; LMC and protodolomite; HMC, respectively. The intensity of superstructure reflections of the protodolomite from Shenhu area is stronger than that from SW Taiwan area, indicating higher MgCO3 content. Based on the formation conditions of Ca-Mg-carbonates from LMC to dolomite, those with higher MgCO3 content are formed in more active cold-seep environment. According to the distribution of carbonate phases in each sample, the cold seep flux was high in Shenhu area and was sustained for a long time. By contrast, the flux in SW Taiwan area was relatively low and not stable. It once became higher, but finally returned to low. © 2015 Elsevier Ltd.

Gong W.,Sun Yat Sen University | Gong W.,Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering | Wang Y.,Nanjing University | Jia J.,State Oceanic Administration
Journal of Asian Earth Sciences | Year: 2012

In recent years, the increased pressure of saltwater intrusion in the Modaomen Estuary, one of the outlets in the Pearl River Delta (PRD), China, has threatened the freshwater supply for the surrounding regions. The estuary has complex geometry and bathymetry and branches into three waterways, Madaomen Waterway, Hongwan Waterway, and Hezhou Waterway, entering into the coastal sea. In this study, a three-dimensional baroclinic model (EFDC) was used to investigate salt transport among these branches and saltwater intrusion in the mainstem of the estuary. The salt transport at selected cross sections was decomposed into three components: advection, steady shear, and tidal oscillatory, following the method of Lerczak et al. (Lerczak, J.A., Geyer, W.R., Chant, R.J., 2006. Mechanisms driving the time-dependent salt flux in a partially stratified estuary. Journal of Physical Oceanography 36, 2296-2311). Results from this study indicate that the Hongwan Waterway serves as a salt source for the mainstem of the estuary, especially during spring tides, while the Hezhou Waterway mainly acts as a salt sink for the mainstem. The down-estuary wind increases the steady shear transport in the Modaomen Waterway and the advection transport in the Hongwan Waterway, which alters the saltwater intrusion in the estuary. Closure of the Hongwan and the Hezhou Waterways could result in a 20% decrease of saltwater intrusion in the estuary. These results provide scientific basis for water resource management in the region. © 2011 Elsevier Ltd.

Cai H.,Sun Yat Sen University | Cai H.,State and Local Joint Engineering Laboratory of Estuarine Hydraulic Technology | Cai H.,Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering | Toffolon M.,University of Trento | Savenije H.H.G.,Technical University of Delft
Coastal Engineering Journal | Year: 2016

An analytical model is used to investigate the resonant behavior in a semi-closed channel. The main integral quantities of the tidal wave are obtained by means of a linearized one-dimensional model as a function of three dimensionless parameters, representing cross-section convergence, friction and distance to the closed boundary. Arbitrary along-channel variations of width and depth are accounted for by using a multi-reach approach, whereby the main tidal dynamics are reconstructed by solving a set of linear equations satisfying the continuity conditions of water level and discharge at the junctions of the sub-reaches. We highlight the importance of depth variation in the momentum equation, which is not considered in the classical tidal theory. The model allows for a direct characterization of the resonant response and for the understanding of the relative importance of the controlling parameters, highlighting the role of convergence and friction. Subsequently, the analytical model is applied to the Bristol Channel and the Guadalquivir estuary. The proposed analytical relations provide direct insights into the tidal resonance in terms of tidal forcing, geometry and friction, which will be useful for the study of semi-closed tidal channels that experience relatively large tidal ranges at the closed end. © 2016 © The Author(s)

Gong W.,Sun Yat Sen University | Gong W.,Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering | Jia L.,Sun Yat Sen University | Jia L.,Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering | And 2 more authors.
Continental Shelf Research | Year: 2014

Huangmaohai Estuary is a micro-tidal funnel-shaped estuary, located along the southwestern side of the Pearl River Delta complex. Variations of sediment transport patterns under different conditions of river discharge and tidal mixing are investigated by using field measurements and data analysis during both dry and wet seasons, respectively. The intratidal variation of sediment dynamics is largely controlled by the tidal asymmetry. The typical pattern of 25-hour mean sediment transport during the dry season is that the transport is landward in the channel and seaward on the shoals. A bifurcation pathway of sediment transport shows that sediments are imported from the East Opening and exported through the Middle Opening. However, this pattern can be altered by mixing processes and river discharge. Enhanced mixing or increased discharge can result in a predominantly seaward transport. Conversely, weak mixing can result in an emphatic landward transport. In general, the sediment transport is closely associated with the morphological evolution in the estuary. © 2014 Elsevier Ltd.

Xiaoming S.,Sun Yat Sen University | Xiaoming S.,Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering
Acta Geologica Sinica | Year: 2011

In the present study, the modified Sverjensky-Molling equation, derived from a linear-free energy relationship, is used to predict the Gibbs free energies of formation of crystalline phases of a-MOOH (with a goethite structure) and a-M2O3 (with a hematite structure) from the known thermodynamic properties of the corresponding aqueous trivalent cations (M3+). The modified equation is expressed as \G JM FX=≤MKAAG iji^+bMyX+PMyxyiu 3*, where the coefficients aMyX, bMyX, and fiMyX characterize a particular structural family of MVX (M is a trivalent cation [M3+] and X represents the remainder of the composition of solid); j^is the ionic radius of trivalent cations (M 3*); AG /,MVX^ the standard Cibbs free energy of formation of MVX; and AG ^M3* is the non-solvation energy of trivalent cations (M34). By fitting the equation to the known experimental thermodynamic data, the coefficients for the goethite family (a-MOOH) are C MFA=0.8838, AMFA=-424.4431 (kcal/mol), and pMyx=\\5 (kcal/ mol.A), while the coefficients for the hematite family (a-M2O 3) are aMvx=U468, bMyx=S14.9573 (kcal/ mol), and /?MFX=278 (kcal/mol.A). The constrained relationship can be used to predict the standard Gibbs free energies of formation of crystalline phases and fictive phases (i.e. phases that are thermodynamically unstable and do not occur at standard conditions) within the isostructural families of goethite (a-MOOH) and hematite (a-M2O3) if the standard Gibbs free energies of formation of the trivalent cations are known. Copyright © 1999-2011 John Wiley & Sons, Inc. All Rights Reserved.

Gong W.,Sun Yat Sen University | Gong W.,Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering | Schuttelaars H.,Technical University of Delft | Zhang H.,Sun Yat Sen University | Zhang H.,Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering
Ocean Dynamics | Year: 2016

Different types of tidal asymmetry (see review of de Swart and Zimmerman Annu Rev Fluid Mech 41: 203–229, 2009) are examined in this study. We distinguish three types of tidal asymmetry: duration and magnitude differences between flood and ebb tidal flow, duration difference between the rising and falling tides. For waterborne substance transport, the first two asymmetries are important while the last one is not. In this study, we take the Huangmaohai Estuary (HE), Pearl River Delta, China as an example to examine the spatio-temporal variations of the tidal asymmetry in a mixed semidiurnal tidal regime and to explain them by investigating the associated mechanisms. The methodology defining the tidal duration asymmetry and velocity skewness, proposed by Nidzieko (J Geophys Res 115: C08006. doi: 10.1029/2009JC005864, 2010) and synthesized by Song et al. (J Geophys Res 116: C12007. doi: 10.1029/2011JC007270, 2011), is utilized here and referred to as tidal duration asymmetry (TDA) and flow velocity asymmetry (FVA), respectively. The methodology is further used to quantify the flow duration asymmetry (FDA). A positive asymmetry means a shorter duration of low water slack for FDA, a shorter duration of the rising tide for TDA, and a flood dominance for FVA and vice versa. The Regional Ocean Modeling System (ROMS) model is used to provide relatively long-term water elevation and velocity data and to conduct diagnostic experiments. In the HE, the main tidal constituents are diurnal tides K1, O1 and semidiurnal tides M2 and S2. The interaction among the diurnal and semidiurnal tides generates a negative tidal asymmetry, while the interactions among semidiurnal tides and their overtides or compound tides result in a positive tidal asymmetry. The competition among the above interactions determines the FDA and TDA, whereas for the FVA, aside from the interaction among different tidal constituents, an extra component, the residual flow, plays an important role. The results show that the FDA exhibits a predominant tendency of shorter duration of low water slack, favoring the landward transport of fine sediment. The FVA demonstrates prevailing ebb dominance in the study period, favoring the seaward transport of coarse sediment. This ebb dominance is primarily induced by the interaction among the residual flow and the tidal constituents. The external TDA in the ocean experiences distinct cyclic variations with positive asymmetry when semidiurnal tides dominate and negative asymmetry during the periods when diurnal tides dominate. The funnel shape of the HE is advantageous for the development of positive tidal asymmetry as the semidiurnal tides are more amplified than the diurnal tides. The effect of river flow can enhance the ebb dominance, while the baroclinic effect is more complex. The existence of channel and shoals favors the development of residual pattern with seaward flow (ebb dominance) in the channel and landward flow (flood dominance) at the shoal when the tides are strong (semidiurnal tides dominate) and the residual pattern with landward flow (flood dominance) in the channel and seaward flow (ebb dominance) at the shoal when the baroclinic effect is dominant (diurnal tides dominate). © 2016 Springer-Verlag Berlin Heidelberg

Gong W.,Sun Yat Sen University | Gong W.,Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering | Shen J.,Virginia Institute of Marine Science | Jia L.,Sun Yat Sen University | Jia L.,Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering
Journal of Marine Systems | Year: 2013

The Huangmaohai Estuary is the most western estuary in the Pearl River Delta, China. The tide in the estuary is a mixed semi-diurnal tide. The water level fluctuation is dominated by periods of semi-diurnal tide and alternated by periods of diurnal tide. The tidal range is generally larger during diurnal tide than during semi-diurnal tide, thus the diurnal tide and the semi-diurnal tide are referred to as spring tide and neap tide, respectively, in a traditional sense. The estuary is classified as well-mixed to partially mixed in dry seasons. The salinity distribution is abnormal, since the estuary becomes more stratified during the diurnal tide and more mixed during the semi-diurnal tide. Correspondingly, salt intrusion is strong during the diurnal tide and weak during the semi-diurnal tide. Model diagnostic analyses indicate that the geometry of the estuary largely controls the variation of tidal current during the spring-neap tidal cycle, and the water exchange among the Pearl River Network plays an important role in modulating salt intrusion in the estuary. The change of the diurnal tide and the semi-diurnal tide during a spring-neap tidal cycle results in a strong tidal current during semi-diurnal tide and a weak current during the diurnal tide, which contributes to the change in mixing and salt flux in the estuary. The variation of freshwater discharged into the estuary over a spring-neap tidal cycle is controlled by the river flow distribution in the Pearl River Network and demonstrates a pattern with more freshwater inflow in the estuary during the semi-diurnal tide than that during the diurnal tide. This pattern coincides with the change in tidal mixing resulting in variations of stratification, estuarine circulation, and salt transport during the spring-neap tidal cycle. The combination of tidal action and buoyancy forcing determines the salt intrusion pattern. © 2012 Elsevier B.V.

Zhai W.,Sun Yat Sen University | Zhai W.,Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering | Sun X.,Sun Yat Sen University | Sun X.,Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering | And 6 more authors.
Ore Geology Reviews | Year: 2014

The southern Tibet AuSb metallogenic belt in the Himalayan orogen consists of more than 50 gold, gold-antimony and antimony lode deposits, and associated placer gold deposit. The deposits are hosted in a Mesozoic metamorphosed turbidite sequence of the Indian passive continental margin. The Zhemulang Au deposit, Mazhala AuSb deposit, and Shalagang Sb deposit are three typical examples of such epizonal orogenic deposits. At Zhemulang, gold-bearing quartz veins occur in the Upper Triassic Songre Formation, consisting of carbonaceous phyllite and slate. Ore minerals are native gold, pyrite, galena, chalcopyrite, and limonite. At Mazhala, the gold- and stibnite-bearing quartz vein orebodies are hosted in Lower to Middle Jurassic slate, interlayered with metastandstone, metasiltstone, and limestone of the Lure Formation. Ore minerals are native gold, stibnite, pyrite, arsenopyrite, and trace amount of cinnabar. At Shalagang, the host rocks are Lower Cretaceous sandstone, siltstone, muddy limestone, and chert of the Duojiu Formation. Orebodies consist mainly of stibnite-bearing quartz veins and locally altered fault breccia. Ore minerals are stibnite, cinnabar, valentinite [Sb2O3], limonite, and trace amount of pyrite, arsenopyrite, and realgar. For the three deposits, the wallrock alteration has produced the minerals silica, carbonates, white mica, sulfide and chlorite. The three deposits have a similar element associations, but with a few slight variations. The Zhemulang, Mazhala, and Shalagang deposits, in order of element enrichments relative to crustal abundance, are anomalous in Au, Sb, Te, Bi, As, Pb, Ag, and W; Sb, Au, Te, As, Pb, Bi, Ag and W, to Sb, Te, As, Au, Hg, W, Pb, and Ag, respectively, and all depleted in Cu, Zn, Sn, and Mo.Various aqueous, carbonic, and hydrocarbon fluid inclusions were recognized in quartz and/or stibnite at the three deposits. These include type 1a one-phase aqueous inclusions, type 1b two-phase aqueous inclusions, type 2a carbonic inclusions, type 2b aqueous-carbonic inclusion, and rare type 3 hydrocarbon inclusions that include two-phase hydrocarbon inclusions (type 3a) and dark one-phase hydrocarbon inclusions (type 3b). The three deposits have the similar low-salinity H2OCO2CH4N2 ore fluids with trace amounts of hydrocarbons. For the Zhemulang, Mazhala, and Shalagang deposits, the salinities of aqueous inclusion range mainly between 3.3 and 6.4wt.% NaCl equiv., 2.5 and 4.9wt.% NaCl equiv. and 4.1 and 6.4wt.% NaCl equiv., respectively. The ore-forming temperatures vary mainly from 180 to 320°C, 160 to 300°C and 140 to 240°C, respectively. The estimated mineralization depths are 4 to 6km, 3 to 5km, and 1 to 4km of the epizonal environment, respectively. The different mineralization temperatures and pressures led to the different element enrichments at the three deposits.For the Zhemulang, Mazhala and Shalagang deposits, ore fluid isotopic compositions are δDH2O -107.5 to -36.7‰ and δ18Ofluid 2.8 to 8.2‰, δDH2O -119.0 to -72.7‰ and δ18Ofluid 7.5 to 16.2‰, and δDH2O -173.4 to -139.2‰ and δ18Ofluid 7.5 to 12.3‰, respectively; δ13Cfluid values are -11.7 to -9.6‰, -3.5 to -2.5‰, and -6.5 to -5.1‰, respectively; and δ34S values are -4.0 to -1.1‰, -0.8 to 2.3‰, and -3.9 to 2.1‰, respectively. The ore-forming fluids were partly derived from metamorphic devolatilization of immediate or deeper level country rocks, with a deposit's corresponding metamorphic degree controlling the fluid PTX. The ore-forming fluid for Zhemulang, Mazhala, and Shalagang consisted of predominantly metamorphic water with minor involvement of meteoric water, a mixture of metamorphic fluid and meteoric water, and predominantly meteoric water, respectively. Ore metals were derived from country rocks, including synsedimentary Sedex-like sulfide layers in the Jurassic strata observed at the Mazhala AuSb deposit. Among three deposits, the variation of δ13Cfluid and δ34S reflects the fact that the Zhemulang Au deposit formed from a relatively high content of organic carbon and low f{hook}O2 fluid, the Mazhala AuSb deposit from a relatively low content of organic carbon and high f{hook}O2 fluid, and the Shalagang Sb deposit from an intermediate content of organic carbon and f{hook}O2 fluid. Fluid immiscibility was the main mechanism for ore metal precipitation at all three deposits. The vertical zonation of Au, AuSb, and Sb mineralization suggests that additional gold resources may exist below the antimony or gold-antimony orebodies. Stream sediment and soil geochemical surveys and the occurrence of placer gold prospects are effective for identifying areas of orogenic gold and antimony deposits in the Himalayan and other orogens. © 2013 Elsevier B.V.

Loading Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering collaborators
Loading Guangdong Provincial Key Laboratory of Marine Resources and Coastal Engineering collaborators