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观测红树林潮滩在波浪和潮流作用下的近底层垂向剖面悬沙浓度变化过程, 对理解海岸带植被的消能促淤机制和滨海湿地生态修复工程有着重要作用。本文以北部湾七星岛岛尾桐花树红树林潮滩为例, 基于剖面流速仪HR、声学多普勒单点流速仪ADV、浪潮仪T-wave及剖面浊度仪ASM, 获取了研究区域2019年夏季大潮连续3天的水文数据, 同时结合桐花树典型植株实测参数, 分析了潮周期内红树林潮滩近底层垂向剖面悬沙响应波浪、潮流作用及桐花树空间结构的运动过程。结果表明: 1) 桐花树潮滩近底层悬沙浓度和悬沙通量具有涨潮明显大于落潮的潮汐不对称现象, 剖面垂向高悬沙浓度区域在涨潮初期—涨急由距底部0.1~0.37m转变为距底部0.5~0.67m, 落急—落潮末期则由上部转变为下部; 2) 潮周期内悬沙起动和再悬浮阶段发生在以波浪作用主导的涨潮初期和落潮末期, 平流和沉降发生在以潮流作用为主的涨急至落急整个阶段; 3) 涨潮阶段桐花树冠层的茂密枝叶通过减缓流速拦截多于冠层上部40%以上的悬沙, 落潮水体则挟沙自陆向海经过桐花树群落, 使得悬沙浓度下降超过71%。该不对称涨、落潮动力沉积机制有利于悬沙向岸输运, 促进潮滩扩张过程。 相似文献
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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0.75 m）、湾外（距底0.50 m）站位底边界层的平均摩阻流速分别是0.016 m/s、0.013 m/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109 mg/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5 m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41.7%;湾外站位向湾内方向净输运10.57 g/(m·s),主要受平流输沙和垂向净环流的控制,贡献率94.9% 相似文献
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本文基于4次洪枯季同步水文观测资料,着重分析了长江口北支悬沙浓度的潮周期变化、垂向分布、纵向分布和悬沙输移及其时空差异。研究结果显示,悬沙浓度的潮周期变化过程在大中潮期以M型(双峰型)为主,下段主槽内在大潮期多出现V型,上段在枯季可出现涨潮单峰型;小潮期可出现无峰、单峰或双峰型。涨、落潮悬沙浓度峰值及均值,在枯季多涨潮大于落潮,洪季中小潮特别是小潮期易出现落潮大于涨潮;下段主槽内在大潮期易出现落潮大于涨潮。悬沙浓度的垂向分布及其变化特点,在大中潮期与悬沙的潮周期变化型式有关,其中M型存在显著的洪枯季差异。纵向上,最高悬沙浓度在枯季出现于中段灵甸港至三和港之间及附近河段,洪季则在下段三条港附近。潮周期悬沙净输移,枯季大多向陆特别是大中潮期,洪季中上段大多向海,下段大潮期多向陆、中小潮易出现向海;下段主槽内在大潮期易出现向海。 相似文献
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长江口北港口门海域悬沙输运机制分析 总被引：1，自引：0，他引：1
根据2012年10月24日至11月1日在长江口北港口门海域获取的沉积动力学数据,采用输运通量分解方法分析水沙输运机制。结果表明,长江口北港口门附近海域涨、落潮期间底部悬沙浓度与近底部流速呈显著线性相关,存在显著的再悬浮作用;潮周期内的悬沙输运具不对称特征,涨潮悬沙浓度大于落潮悬沙浓度,悬浮泥沙有向陆输运的趋势。拉格朗日平流输运是影响悬沙输运的主要贡献项;潮泵效应(尤其是潮汐捕捉效应)以及河口垂向环流作用是两个次要影响因素,在影响程度上前者比后者略大。观测发现,长江口北港口门海域潮流除了具有涨落潮流速、历时等不对称现象外,还具有流速结构不对称的特征,进而导致涨、落潮底部湍流混合程度不对称与输沙不对称,这可能是造成悬沙向河口内输运形成最大浑浊带的重要因素。 相似文献
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于2005年5月大潮期间在杭州湾北部潮流深槽区的4个站位进行潮周期观测,获得了流速、悬沙等数据,并对其进行了分析,计算了水沙通量和再悬浮通量。分析结果表明,该深槽区涨潮流速大于落潮流速,涨潮历时小于落潮历时,潮差自湾口向湾内方向增大;悬沙的组分以粉砂为主,分选较差,偏态以负偏为主,这些特征与底质一致;深槽中部和东部的悬沙沿岸线向湾内方向输运;深槽西部和东部外侧的悬沙输运方向与余流方向一致,分别向湾内和南部输运;除转流和流速加速初期外,垂线流速分布符合Kûrmûn-Prandtl模型,摩阻流速与垂线平均流速变化趋势一致。计算得到的表观粗糙长度在涨落潮时段的水流加速或减速阶段都呈增大趋势,且数值较大,这难以把它简单地归结为床面形态的作用,表观粗糙长度的变化趋势可能是高悬沙浓度和浓度成层性共同作用的结果,但对这一假说的验证还有待于进一步的现场观测和机制分析。计算所得的再悬浮发生的周期性与实测悬沙浓度的周期性相符,而且最大悬沙浓度的出现滞后于最大再悬浮通量,说明再悬浮作用对水层中悬沙浓度的变化具有重要影响。 相似文献
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江苏大丰潮间带粉砂滩的潮流边界层特征 总被引：4，自引：0，他引：4
对江苏大丰潮间带粉砂滩的潮流观测数据，运用Karman-parndtl模型分析了流速对数剖面的出现频率和边界层参数（摩阻流速与粗糙长度）。结果表明，不同时间尺度（10^1-10^3s）的平均流速对计算u-lnz线性关系出现频率的影响不大，而不同层位组合的影响较为显著，影响流速对数剖面分布的自然因素为波浪、风、潮流旋转、表底层流向差异、滩面坡度和水流加减速等。相邻层位的流速在时间序列上存在很高的线性关系，回归直线的斜率与水层距底床的高度、粗糙长度和摩阻流速有关。涨潮阶段床面粗糙长度大于落潮阶段，涨潮阶段摩阻流速小于落潮阶段。 相似文献
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根据浙江舟山野鸭山至螺头山岸段海域4个测点的海流观测和含沙量调查(其中1个测点)资料,含沙量用1/10000感量的电光分析天平称量测定,悬沙粒度用AT 型库尔特计数器测定,底质表层泥样用激光粒度仪测定,使用DS3水准仪(其精度标准为四等)测量岸段潮滩高程,对该岸段所在海域的泥沙与潮流特征进行了对比分析并讨论了岸滩的冲淤变化。结果表明,该海域悬沙浓度由表层往底层逐渐增高,且与流速有一定的线性关系;中潮悬沙浓度低于大潮,冬季悬沙浓度高于春、夏季;大、中潮的落潮输沙量大于涨潮,大潮涨、落潮的输沙量大于中潮涨、落潮,大潮全潮单宽净输沙量大于中潮;冬季平均悬沙粒径比夏季大,春季适中;春、夏、冬季悬沙的分选系数属分选极好;悬沙的运移路径以落潮流流向为净输沙的方向;该海域的潮流为往复流,涨潮流历时短于落潮流历时,春、夏、冬季平均落潮流速大于平均涨潮流速,最大流速为1.82m/s(夏季),平均流速为0.70m/s;历史上野鸭山至螺头山的古海湾一直缓慢淤涨,1987年以来,潮滩仍缓慢淤涨,中潮滩平均淤高值约为3cm/a,岸滩平均淤进速度约为0.38m/a。 相似文献
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基于椒江河口大、小潮期间水位、流速、盐度和悬沙浓度观测数据,研究了椒江河口主潮汐通道的水动力、盐度和悬沙浓度的时空变化特征,解释了高浊度强潮作用下的层化物理机制。椒江河口大潮期悬沙浓度和盐度均大于小潮期,主潮汐通道区域落潮期悬沙浓度大于涨潮期;盐度随潮变化,盐水锋面出现在S2测站,锋面附近出现最大浑浊带;自陆向海,悬沙浓度递减,盐度递增;随水深增加,悬沙浓度与盐度递增。Richardson数与混合参数显示,盐度和悬沙引起的层化现象,是随着潮汐的变化而变化,涨潮时的层化均强于落潮,小潮时的层化持续时间最长,区域更广。混合参数随潮周期变化,大潮期高于临界值1.0,小潮期低于临界值1.0。小潮期水体层化强于大潮期;潮汐应变项是影响势能差异变化率的重要因素;落潮期间层化向混合状态转化,涨潮相反。 相似文献
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Soil-sized particulates have been collected on board ship by a mesh technique from the lower troposphere of the North, Equatorial and South Atlantic Ocean, northern and southern Indian Ocean, South and East China Sea and various coastal localities.Spectrographic analysis reveals that, on average, the particulates have concentrations of Mn, Ni, Co, Ga, Cr, V, Ba, and Sr which are of the same order of magnitude as those in average crustal material. In contrast, the average concentrations of Pb, Sn, and Zn are one order of magnitude higher than those in average crustal material.Within this “world-wide” average there are significant geographical variations in the distributions of Pb, Sn, and Zn which may be related to anthropogenic sources.On the basis of trace-element distributions lower tropospheric soil-sized marine particulates have been divided into four genetic components; local, zonal, inter-zonal, and global. The proportions of these components vary geographically, and each component may have both a natural and an anthropogenic fraction. 相似文献
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Tautog, Tautoga onitis, is an abundant species of fish in estuaries of the northeastern United States. Planktonic tautog larvae are abundant in summer in these estuaries, but there is little information on rates of growth of tautog larvae feeding on natural assemblages of food in the plankton. We examined abundance and growth of larval tautog and environmental factors during weekly sampling at three sites along a nearshore‐to‐offshore transect in Buzzards Bay, Massachusetts, USA during summer 1994. This is the first study of a robust sample size (336 larvae) to estimate growth rates of field‐caught planktonic tautog larvae feeding on natural diets, using the otolith daily‐growth‐increment method. The study was over the entire summer period when tautog larvae were in the plankton. The sampling sites contrasted in several environmental variables including temperature, dissolved oxygen (DO), and chlorophyll a concentration. There was a temporal progression in the abundance of tautog larvae over the summer, in relation to location and temperature. Tautog larvae were first present nearshore, with a pronounced peak in abundance occurring at the nearshore sites during the last 2 weeks in June. Larvae were absent at this time further offshore. From late June through August, larval abundance progressively decreased nearshore, but increased offshore although never approaching the abundance levels observed at the nearshore sites. The distribution and abundance of tautog larvae appeared to be related to a nearshore‐to‐offshore seasonal warming trend and a nearshore decrease in DO. Otoliths from 336 larvae ranging from 2.3 to 7.7 mm standard length had otolith increment counts ranging from 0 to 19 increments. Growth of larval tautog was estimated at 0.23 mm·day?1, and length of larvae prior to first increment formation was estimated at 2.8 mm indicating that first increment formation occurs 3–4 days after hatching at 2.2 mm. Despite spatial and temporal differences in environmental factors, there were no significant differences in growth rates at any of three given sites over time, or between sites. Because larval presence only occurred at a narrow range of temperature (17–23.5 °C) and DO (6.5–9.3 mg·l?1), in situ differences in growth did not appear to be because of differences in larval distribution and abundance patterns relative to these parameters. 相似文献
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P.N. Froelich L.W. Kaul J.T. Byrd M.O. Andreae K.K. Roe 《Estuarine, Coastal and Shelf Science》1985,20(3):239-264
Concentrations of dissolved nutrients (NO3, PO4, Si), germanium species, arsenic species, tin, barium, dimethylsulfide and related parameters were measured along the salinity gradient in Charlotte Harbor. Phosphate enrichment from the phosphate industry on the Peace River promotes a productive diatom bloom near the river mouth where NO3 and Si are completely consumed. Inorganic germanium is completely depleted in this bloom by uptake into biogenic opal. The ratio taken up by diatoms is about 0·7 × 10?6, the same as that provided by the river flux, confirming that siliceous organisms incorporate germanium as an accidental trace replacement for silica. Monomethylgermanium and dimethylgermanium concentrations are undetectable in the Peace River, and increase linearly with increasing salinity to the seawater end of the bay, suggesting that these organogermanium species behave conservatively in estuaries, and are neither produced nor consumed during estuarine biogenic opal formation or dissolution. Inorganic arsenic displays slight removal in the bloom. Monomethylarsenic is produced both in the bloom and in mid-estuary, while dimethylarsenic is conservative in the bloom but produced in mid-estuary. The total production of methylarsenicals within the bay approximately balances the removal of inorganic arsenic, suggesting that most biological arsenic uptake in the estuary is biomethylated and released to the water column. Dimethylsulfide increases with increasing salinity in the estuary and shows evidence of removal, probably both by degassing and by microbial consumption. An input of DMS is observed in the central estuary. The behavior of total dissolvable tin shows no biological activity in the bloom or in mid-estuary, but does display a low-salinity input signal that parallels dissolved organic material, perhaps suggesting an association between tin and DOM. Barium displays dramatic input behavior at mid-salinities, probably due to slow release from clays deposited in the harbor after catastrophic phosphate slime spills into the Peace River. 相似文献
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E. Wolanski P. Colin J. Naithani E. Deleersnijder Y. Golbuu 《Estuarine, Coastal and Shelf Science》2004,60(4):705-716
Three years of temperature data along two transects extending to 90 m depth, at Palau, Micronesia, show twice-a-day thermocline vertical displacements of commonly 50–100 m, and on one occasion 270 m. The internal wave occurred at a number of frequencies. There were a number of spectral peaks at diurnal and semi-diurnal frequencies, as well as intermediate and sub-inertial frequencies, less so at the inertial frequency. At Palau the waves generally did not travel around the island because there was no coherence between internal waves on either side of the island. The internal waves at a site 30 km offshore were out-of-phase with those on the island slopes, suggesting that the waves were generated on the island slope and then radiated away. Palau Island was thus a source of internal wave energy for the surrounding ocean. A numerical model suggests that the tidal and low-frequency currents flowing around the island form internal waves with maximum wave amplitude on the island slope and that these waves radiate away from the island. The model also suggests that the headland at the southern tip of Palau prevents the internal waves to rotate around the island. The large temperature fluctuations (commonly daily fluctuations ≈10 °C, peaking at 20 °C) appear responsible for generating a thermal stress responsible for a biologically depauperate biological community on the island slopes at depths between 60 and 120 m depth. 相似文献
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Klaus Kremling 《Marine Chemistry》1983,13(2):87-108
In June 1981, dissolved Zn, Cd, Cu, Ni, Co, Fe, and Mn were determined from two detailed profiles in anoxic Baltic waters (with extra data for Fe and Mn from August 1979). Dramatic changes across the O2H2S interface occur in the abundances of Cu, Co, Fe, and Mn (by factors of ?100). The concentrations of Zn, Cd, and Ni at the redox front decrease by factors between 3 to 5.Equilibrium calculations are presented for varying concentrations of hydrogen sulfide and compared with the field data. The study strongly supports the assumption that the solubility of Zn, Cd, Cu, and Ni is greatly enhanced and controlled by the formation of bisulfide and(or) polysulfide complexes. Differences between predicted and measured concentrations of these elements are mainly evident at lower ΣH2S concentrations.Cobalt proved to be very mobile in anoxic regions, and the results indicate that the concentrations are limited by CoS precipitation. The iron (Fe2+) and manganese (Mn2+) distribution in sulfide-containing waters is controlled by total flux from sediment-water interfaces rather than by equilibrium concentrations of their solid phases (FeS and MnCO3). The concentrations of these metals are therefore expected to increase with prolonged stagnation periods in the basin. 相似文献