Composition of the organic matter of the water,suspended matter,and bottom sediments in Nha Trang Bay in Vietnam in the South China Sea

Research has been conducted in Nha Trang Bay (Southern Vietnam, the South China Sea) at the section from the estuary of the Cai River to the marine part of the bay, as well as in the area of coral reefs. The objects of the studies are the river and sea waters, the suspended matter, and the bottom sediments. Data on the dissolved organic carbon and the total nitrogen in the water are obtained. The organic carbon content is estimated in the suspended matter; the organic carbon and the molecular and group composition of the n-alkanes are determined in the bottom sediments. The molecular and group composition of the n-alkanes in the bottom sediments of the landfill have made it possible to identify three types of organic matter (OM): marine, mixed, and of mainly terrigenous origin. All the types of OM are closely related to the specificity of the sedimentation and the hydrodynamics of the waters in this water area.     

Features of the soft-bottom subtidal macrobenthos in Nha Trang Bay (Vietnam, South China Sea)

General characteristics of macrobenthos of the muddy sediments of the subtidal (19–24 m) zone in Nha Trang Bay (South Vietnam) were described based on the survey performed in April–May 2002. The mean abundance of organisms was 637 ind/m² and the mean biomass was 2.3 g/m². Sixty-seven macrobenthic species were found during the study. The main structural features of the macrobenthos were high species diversity, low species recurrence, and high eveness of the species structure with the absence of clearly manifested dominants. The number of species encountered regularly increased with the increase in the total area sampled from 210 to 5000 cm², though the relation did not reach saturation. The similarities and differences between the macrobenthos structures in Nha Trang Bay and those in some tropical and boreal soft-bottom communities are discussed.     

Influence of anthropogenic pressure and seasonal upwelling on coral reefs in Nha Trang Bay (Central Vietnam)

The growing coastal development, dredging and dumping activities, overfishing and expansion of marine cage culture in Nha Trang Bay (NTB) of Central Vietnam since the beginning of the 2000s have resulted in a dramatic decrease of live coral cover. Surveys conducted in April–May 2013 and the same period in 2014 revealed that with an increase in distance from the outer part of the bay towards the mainland, the rivers’ influxes and dredged areas, coral cover decreased from 75% to 0.6% and species richness from 63 to 5, while the abundance of macroalgae increased from 0% to 56%. These changes correlate with differences in the concentration of suspended sediments on the same gradient. The abundance of the crown‐of‐thorns starfish Acanthaster planci and of the echinoid Diadema setosum significantly increased between the first estimation in 1998 and the survey in 2014, from 0 to 1.7 individuals (ind.) per 100 m^?2 and from 50.8 to 94.5 ind. per 100 m^?2, respectively, contributing to coral loss and intensive bioerosion of the reef framework in the bay. The large sizes of adult colonies of tabulate Acropora on the remote stations with negligible sedimentation and eutrophication loads were inconsistent with the assumptions that temperature‐induced coral bleaching or cyclones could be the major impacts in Nha Trang Bay. Analysis of the 16‐year thermal history of the bay did not reveal any instances in which the coral thermal bleaching threshold had been exceeded up to the present study. Seasonal upwelling, which occurs annually in the vicinity of Central Vietnam, may contribute to mitigation of thermal anomalies within NTB and to the maintenance of healthy coral communities on the remote reefs with relatively low anthropogenic impact.     

Clay mineralogy of bottom sediment in the Jinhae Bay,Korea

The bottom sediments of Jinhae Bay area contain, on average, 45 % illite, 23 % kaolinite, 17 % intergrade clay, 10 % chlorite, and 5 % smectite. The geographical distribution of the clay minerals shows, in general, an it crease in illite, a decrease in kaolinite, and a slight decrease in chlorite seawards. The distributional trends of smectite and intergrade clay are irregular. The clay fractions of the sediments of Jinhae Bay are supplied from stream-borne sediments and are mixed with sediments transported landwards from the East China Sea. Local erosion and redeposition of the clay fractions of the bottom sediments is caused by rapid tidal currents.     

粤西海陵湾底质沉积特征与泥沙输运路径

在分析粤西海陵湾表层沉积物分布特征的基础上,应用泥沙搬运矢量模型计算了泥沙净输运趋势。结果表明,海区南北两端均存在着一个泥沙聚集区,北侧是径流与涨潮上潮流交绥的响应,南侧是波浪与落潮下泄流交绥的响应。分选性好的中部广大区域受单一动力作用,泥沙净输移方向由北指向南。     

大亚湾海域典型有机氯农药生物累积特征及变化因素研究

于2003年采集大亚湾海域28个鱼类等生物样品和14个表层沉积物样品,分析其中滴滴涕(DDTs)、六六六(HCHs)和氯丹(CHLs)各组分的含量以及脂含量和δ15N,δ13C同位素值,重点研究了大亚湾沉积物和生物体中有机氯农药(OCPs)的污染现状及其生物积累规律.大亚湾海域鱼类DDTs,HCHs和CHLs平均含量分别为57.1±52.9,0.30±0.18和0.87±0.35ng/g(湿重);与其他海区相比,该海域生物体中DDTs的含量相对较高,HCHs和CHLs较低;表层沉积物中高的p,p'-DDT含量及较低的(DDE+DDD)/DDT比值(平均为0.56,<1),均显示仍有新的DDTs源输入;OCPs在生物累积中表现出脂溶性的特征,生物体内脂含量越高,其OCPs含量也越高;δ15N,δ13C同位素的研究结果显示肉食性生物比植食性生物更易累积OCPs;大亚湾海域OCPs的生物-沉积物累积系数(BSAF)与有机物的亲脂性程度即辛醇-水比值(K_OW)存在显著的正相关.     

水动力对越南巴达棱湾表层沉积物和岸滩的影响

基于越南巴达棱湾2007年4月采集的42个表层沉积物样品及实测水文资料,分析越南巴达棱湾表层沉积物特征,并结合GSTA模型分析表层沉积物的运移趋势。结果表明:越南巴达棱湾表层沉积物以粗颗粒为主,在潮流和波浪的作用下呈中西部粗、东部细的分布特征;其西侧表层沉积物沿岸线自西南向湾内运移,中西近岸区沉积物垂直于岸线做离岸输移,在湾的东侧存在自东北向西南的运移趋势,并与从湾西运移过来的底沙相遇,形成运移辐聚区,并在余流的作用下,向西运移;"波浪掀沙,潮流输沙"是该地区表层沉积物输运的主要作用机制;在波浪的作用下,研究海域的海岸线处于侵蚀状态,有后退的趋势。     

Current status and historical trends of organochlorine pesticides in the ecosystem of Deep Bay, South China

To characterize the current status and historical trends in organochlorine pesticides (OCPs) contamination in Deep Bay, an important water body between Hong Kong and mainland China with a Ramsar mangrove wetland (Maipo), samples from seawater, suspended particulate matter (SPM), surface sediment, sediment core and fish were collected to determine the OCPs concentrations. Sediment core dating was accomplished using the ²¹⁰Pb method. The average concentrations of DDTs, HCHs and chlordanes in water were 1.96, 0.71, 0.81 ng l⁻¹, while in SPM were 36.5, 2.5, 35.7 ng g⁻¹ dry weight, in surface sediment were 20.2, 0.50, 2.4 ng g⁻¹ dry weight, and in fish were 125.4, 0.43, 13.1 ng g⁻¹ wet weight, respectively. DDTs concentrations in various matrices of Deep Bay were intermediate compared with those in other areas. Temporal trends of the targeted OCPs levels in sediment core generally increased from 1948 to 2004, with the highest levels in top or sub-surface sediment. Both DDT composition and historical trends indicated an ongoing fresh DDT input. A positive relationship between the bioconcentration factor (BCF) of target chemicals and the corresponding octanol–water partition coefficient (K_ow), and between the biota-sediment accumulation factors (BSAF) and the K_ow were observed in the Bay. The risk assessment indicated that there were potential ecological and human health risks for the target OCPs in Deep Bay.     

Modelling phytoplankton deposition to Chesapeake Bay sediments during winter–spring: interannual variability in relation to river flow

The often-rapid deposition of phytoplankton to sediments at the end of the spring phytoplankton bloom is an important component of benthic–pelagic coupling in temperate and high latitude estuaries and other aquatic systems. However, quantifying the flux is difficult, particularly in spatially heterogeneous environments. Surficial sediment chlorophyll-a, which can be measured quickly at many locations, has been used effectively by previous studies as an indicator of phytoplankton deposition to estuarine sediments. In this study, surficial sediment chlorophyll-a was quantified in late spring at 20–50 locations throughout Chesapeake Bay for 8 years (1993–2000). A model was developed to estimate chlorophyll-a deposition to sediments using these measurements, while accounting for chlorophyll-a degradation during the time between deposition and sampling. Carbon flux was derived from these estimates via C:chl-a = 75.Bay-wide, the accumulation of chlorophyll-a on sediments by late spring averaged 171 mg m⁻², from which the chlorophyll-a and carbon sinking fluxes, respectively, were estimated to be 353 mg m⁻² and 26.5 gC m⁻². These deposition estimates were ∼50% of estimates based on a sediment trap study in the mid-Bay. During 1993–2000, the highest average chlorophyll-a flux was in the mid-Bay (248 mg m⁻²), while the lowest was in the lower Bay (191 mg m⁻²). Winter–spring average river flow was positively correlated with phytoplankton biomass in the lower Bay water column, while phytoplankton biomass in that same region of the Bay was correlated with increased chlorophyll-a deposition to sediments. Responses in other regions of the Bay were less clear and suggested that the concept that nutrient enrichment in high flow years leads to greater phytoplankton deposition to sediments may be an oversimplification. A comparison of the carbon flux associated with the deposition of the spring bloom with annual benthic carbon budgets indicated that the spring bloom did not contribute a disproportionately large fraction of annual carbon inputs to Chesapeake Bay sediments. Regional patterns in chlorophyll-a deposition did not correspond with the strong regional patterns that have been found for plankton net community metabolism during spring.     

桑沟湾水体中有机氯农药和多氯联苯的浓度水平及分布特征

以气相色谱-电子捕获检测器(GC/ECD)分析并结合外标法,定量测定了桑沟湾海域水体中15种有机氯农药和多氯联苯类化合物的含量.结果表明:桑沟湾海域表层水体中有机氯农药浓度范围为20.34～52.86 ng/L,底层水中的浓度范围为31.7～58.68 ng/L.该海域水体中共检出有机氯农药6种,DDTs类化合物是水体...     

桑沟湾经济贝类有机氯农药和多氯联苯残留水平及分布特征

采用气相色谱法定量测定了桑沟湾海域2009年4月-2009年12月的经济贝类中有机氯农药和多氯联苯的残留量。结果显示：该海域贝类中 HCHs 为 N.D.~2.04×10-9,均值为0.30×10-9; DDTs 为(0.13~3.36)×10-9,均值为0.97×10-9;PCBs为(0.01~3.20)×10-9,均值为0.59×10-9,有机氯物质含量均低于相关国家标准值,符合食用安全要求。经济贝类中的有机氯农药的组分特征为HCHs中b-HCH占优势, DDTs中p, p′-DDT占相对优势; PCBs中多为5~7个氯原子。与北海等6个海域相比,桑沟湾海域经济贝类有机氯污染物中, HCHs、DDTs和PCBs的残留量都处于中等水平。     

大连湾和杭州湾表层沉积物中多氯联苯和有机氯农药及风险评价

对大连湾与杭州湾沉积物样品中多氯联苯(Polychlorinated Biphenyls,PCBs)和有机氯农药(Organochlorine Pesticides,OCPs)进行了分析测定。结果表明,大连湾和杭州湾沉积物中PCBs的含量为0.72~14.87 ng/g和0.76~3.86 ng/g,其中3、4、5氯联苯比例较高,其和超过总含量的70%;OCPs的含量为2.98~32.23 ng/g和1.61~4.71 ng/g,其中主要成分为六六六(Hexachlorocyclohexanes,HCHs)和滴滴涕(Dichlorodiphenyldichloroethylenes,DDTs)。大连湾和杭州湾表层沉积物中HCHs主要来自农业使用,而且大连湾有新的DDTs输入,杭州湾表层沉积物中的DDTs则主要来自历史残留。生态风险评价的结果表明,PCBs几乎不会对研究区域产生生态风险,OCPs对杭州湾也不会造成潜在的生态风险,但大连湾的OCPs处于中等风险水平,应当引起关注。     

桑沟湾水体及沉积物中有机磷农残时空分布特征

以气相色谱-质谱法(GC-MS)分析并结合外标法,定量测定了2009年4月—2010年2月6个航次桑沟湾海域水体和沉积物中常见的8种有机磷农药,探讨了该海域有机磷农药组成以及时空分布特征.结果表明:桑沟湾水体中共检出有机磷农药6种,其中甲基对硫磷、马拉硫磷和对硫磷等3种有机磷农药在各航次均有检出.沉积物中有机磷农药含量的水平分布呈现由湾口向湾内海域逐渐降低的趋势.该海域水体中有机磷农药含量呈现10月份较高,4月、6月和8月份次之,12月和 2月份最低的月份分布特征.与国内外类似水体相比,桑沟湾海域中总有机磷农药含量处于轻度污染水平,甲基对硫磷、马拉硫磷等单组分含量也处于较低水平.     

三沙湾夏季底边界层动力过程及悬沙输运特征

基于2018年8月福建三沙湾湾内外共两个定点站位的船基和座底三脚架观测数据,研究了三沙湾底边界动力过程及悬沙输运特征。结果表明,三沙湾湾内湾外两个站位均表现出涨落潮历时相近但涨落潮流速明显不对称的现象,即湾内涨潮流速大于落潮流速,湾外则相反。湾内水体受淡水输入影响较大,表现出落潮期间显著的温盐层化,而涨潮期间水体混合良好;湾外水体受淡水影响不明显,表现为水体温度主导的层化。通过对底边界层动力过程的分析表明,湾内(距底0.75m)、湾外(距底0.50m)站位底边界层的平均摩阻流速分别是0.016m/s、0.013m/s,且两个站位拖曳系数基本相等(2.03×10^–3),表明在相同流速下湾内站位的底部切应力更大,近底沉积物再悬浮和搬运相对湾外站位更为显著。因此观测期间悬沙浓度最大值出现在湾内站位,为109mg/L,且悬沙在垂向上的分布可达上层水体;湾外站位悬沙浓度更低,并且底部悬浮泥沙仅能影响至距底5m的水体。悬沙通量机制分解结果表明,三沙湾夏季的潮周期单宽悬沙从湾外向湾内方向净输运,湾内站位向湾内方向净输运74.88 g/(m·s),平流输沙占主导作用,贡献率41....     

The deposition of reef-derived sediment upon a bathyal slope: The deep off-reef environment,north of Discovery Bay,Jamaica

The steep submarine slope north of Jamaica was formed as a normal fault scarp during the early rifting of the Cayman Trough. It is overgrown at the top by flourishing reefs, and below these a series of irregular valleys have been cut into the rocks of the slope and run downslope to at least 2,500 m. Cores from these valleys contain thin layers of reef-derived sands interbedded with pelagic muds of Quaternary age. Cores from topographically high areas recovered only pelagic muds. It is shown that bottom currents and turbidity currents are both unlikely to have been the agencies responsible for the deposition of the reef-derived sands, but that they were probably emplaced by either free avalanching or by sand flow.     

基于遥感反演的莱州湾悬沙分布及其沉积动力分析

选用1986-2004年不同时期的LandsatTM/ETM+影像,利用2004年黄河口附近实测数据推导的表层悬浮泥沙浓度反演模型,结合水文气象资料、多年水深数据和极端天气数模结果,研究了莱州湾西南近岸海域表层悬浮泥沙分布特征,结果表明,受黄河丰枯水期的影响,莱州湾西南部海域悬浮泥沙高浓度区主要分布于黄河口附近海域和西南沿岸,其枯水期的覆盖范围一般大于丰水期的。受潮流高流速场控制,黄河口外悬沙浓度高值区与海底泥沙堆积区对应较好,泥沙主要来源于陆源输沙和泥沙再悬浮;在西南近岸浅海区悬沙浓度高值区主要形成于泥沙的再悬浮,在近岸出现轻微冲刷。风等其他海洋动力因素,一般情况下对悬浮泥沙扩散的程度和范围具有一定的影响作用,但悬沙受潮流场影响而形成的总体扩散趋势未发生改变;极端条件下,风暴潮流使莱州湾西南部近岸浅海区的悬浮泥沙浓度显著增加。     

Distribution and sources of organochlorine pesticides in water and sediments from Daliao River estuary of Liaodong Bay,Bohai Sea (China)

The levels of 19 kinds of organochlorine pesticides (OCPs) in the aqueous phase, suspended particulate matter (SPM), pore water and sediments from Daliao River estuary of Liaodong Bay (Bohai Sea) in northeast China were investigated to evaluate their potential pollution risks. The total OCPs concentrations in the aqueous phase, SPM, pore water and sediments were 3.7–30.1 ng l⁻¹, 4.6–52.6 ng l⁻¹, 157–830 ng l⁻¹ and 2.1–21.3 ng g⁻¹ dry weight, respectively. The concentrations of OCPs, in the Daliao River estuary, are in the mid-range, as compared to those reported in other estuaries worldwide. The distribution of HCHs and DDTs were different indicating different contamination sources. Lindane is the main type of HCH and continuing use in northeast China of ‘pure’ HCH (lindane) rather than technical HCH accounts for the source. The ratios of (DDE + DDD)/DDT in the samples indicate no recent inputs of these chemicals to the estuary.     

The organochlorine contamination history of the Mersey estuary, UK, revealed by analysis of sediment cores from salt marshes

Sediment profiles in the Banks, Ince and Widnes Warth salt marshes in Northwest England contain a mappable record of historic pollution. For persistent organochlorine compounds this stretches back over 90 years. The PCB and HCH profiles can be successfully rationalised by dating methods, and they can be related to the dates of initial production and subsequent withdrawal from use of these chemicals as a result of restrictive environmental legislation. HCB has a more complex pollution profile as it has been manufactured in Northwest England, both deliberately as a pesticide and accidentally as a by-product of several chlorination processes, dating back to the start of the 20th century. The concentrations of degradation products of DDT are relatively constant through the sediment profile and are dominated by op'- and pp'-DDD with only minor contributions from the most toxic species, pp'-DDT. The quantities of these compounds resident in the reservoir of pollutants under these marshes have been calculated, and have fallen progressively in the last 30-50 years.