A STUDY ON EQUILIBRIUM COASTAL PROFILES OF THE CLOSE TIDAL FLAT—A Case Study of Fengxian Tidal Flat

The article analyses the temporal-spatial changes of profiles by EOF(Emipirical Orthogonal Function)analysis and DTM analysis of GIS.These profiles,which are not affected by engineering,are chosen from the coast with successive field monitoring data from 1990 to 1999.Temporal and spatial EOF indicates the obvious stability of coast profile paramclino with steep slopes flat.In spatial scale,high tidal flats and deep-water terraces are in a balance state while upper clino with steep slopes are sensitive and the stability is easy to be destroyes.In temporal scale,the erosion and deposition in this area are kepy in balance in a whole.There are almost no change below -8-9.5m.At the same time,it is the lower limit of tidal affection and the erosion and deposition process from it to high tidal flat keep in balance for many years.So the closre depth is appointed to from -8m to -9.5m(Wusong datum mark).     

Acid volatile sulfide and simultaneously extracted metals in tidal flat sediments of Jiaozhou Bay,China

It is well known that acid-volatile sulfide （AVS） plays an important role in influencing the toxicity of divalent cationic metals within anoxic sediments. In studying sediment core samples collected from tidal flats within the Jiaozhou Bay, China, we found that the AVS concentration gradually increases with depth and decreases from high tidal flat to low tidal flat areas. We evaluated the chemical activity and bioavailability of heavy metals in the tidal flat based on the molar ratio of simultaneously extracted metals （SEM） and AVS. The value of SEM/AVS is generally less than 1 in this area except for the surface layer, which suggests that the heavy metals only have chemical activity in the surface layer. SEM is most highly concentrated at the boundary of the redox layer SEM have similar depth distributions throughout the tidal flat. The aeration of low tidal flat sediment indicates that SEM gradually move to deeper sites via interstitial water.     

Impact of Human Activities on Depositional Process of Tidal Flat in Quanzhou Bay of China

As a very important component of a coastal system,tidal flats come to be a focus of the studies on land-ocean interaction in the coastal zone because those areas are subjected to intense human activities and are highly sensitive to the global change.The Quanzhou Bay,located along the middle part of Fujian coast of China,covers about 136.4km2,and the area of coastal wetland in the entire bay from intertidal to subtidal with 6m of water depth accounts for 96% of the total area.Seven short cores were collected and divided in situ with the interval of 5cm on the coastal wetlands of Quanzhou Bay on April 19,2006.The sediment samples were scattered and the grain sizes were measured by using Mastersizer 2000.Human beings' activities on tidal flat have disturbed the vertical distribution of sediments in stratigraphic sequence and accelerated the sedimentation rates.Grain size analysis results show that the grain size diameters increase and sediment becomes worse sorted towards the sea under the strong human disturbance;Spartina alterniflora can play a role of trapping the fine sediment;but near the bank,the sediment becomes coarse and there are two peak values on frequency curve influenced by the sandpile.The trough formed by human activities along the coastline changes the transport path of water and suspended sediment.The sediments are transported through the trough and deposit in it during the flood;the ebb flow is retarded by the flow output through the adjacent trough,and the deposited sediment can not be re-suspended;then,the sedimentation rate increases.In situ observation show that the sedimentation rate is about 8-10cm/yr.     

Standing crop and primary production of benthic microalgae on the tidal flats in Yueqing Bay

The standing stock and primary production of benthic microalgae on tidal flats were measured seasonally at 3 transects (Puqing, Dahengchuang and Puqi) in Yueqing Bay during 2002 2003. The results showed that the integral chlorophyll a (Chl a) concentration in tidal flat mud exhibited a seasonal variation with the order of magnitude: winter (14.0 4.2 mg m-2) > spring (13.0 6.3 mg m-2) > autumn (7.7 5.9 mg m-2) > summer (4.6 3.2 mg m-2). The primary production showed an order of magnitude: spring (270.5 224.9 mgC m-2 d-1)>winter (238.7 225.5 mgC m-2 d-1)>autumn (214.1 56.2 mgC m-2 d-1)>summer (71.6 44.6 mgC m-2 d-1). Both chlorophyll a and primary production showed maximum values in the surface layer of sediment, and decreased rapidly with increasing depth due to sun light limitation. The results of variance analysis indicated that seasonal variation and tidal flat condition affected Chl a greatly, but had no significant effect on primary production. The annual primary production of benthic microalgae on tidal flats in Yueqing Bay was estimated at 16143 tons carbon, which is sufficient to support 1.02×105 tons shellfish production. The environmental factors affecting chlorophyll and primary production on the tidal flats in Yueqing Bay were discussed. By comparing with other bays on China’s coast, it was observed that Yueqing Bay is a region with high benthic microalgae standing crop and primary production, which may be related to the type of its sediment.     

深圳湾潮流动力特征研究

应用短期资料的潮流准调和分析方法,对深圳湾4测站两周日海流观测获得的表、中、底层海流资料进行分析,计算了4测站O_1、K_1、M_2、S_2、M_4、MS_4 6个主要分潮的潮流调和常数,并给出各测站在各层的潮流椭圆要素。计算结果表明:深圳湾主要为不规则半日潮流海区,浅水分潮流在总海流中的影响较大;站位1、2和4主要分潮流的北分量大于东分量,而站位3主要分潮流的北分量小于东分量。观测期间余流的流向主要呈北和东北向;最小余流速度出现在站位3;余流流速表层最大,中层次之,底层最小。整个海区潮流的可能最大流速表层在76～102cm/s之间;中层在80～106cm/s之间;底层在56～88cm/s之间。整个海区潮流表现出往复流的性质。     

Factorial analysis of annual erosion-accretion cycles of tidal flats in the front area of the southern Changjiang river delta

Based on surveyed data from seven coastal sections and the collected data of wind, sea level, tide, nearshore suspended sediment concentration and river flux from adjacent stations, this paper deals with regressive correlation between monthly average flat elevation and monthly average figures of the influential factors. All sections except one which is located within the river mouth showed negative correlation between flat elevation and sea level and between flat elevation and tidal range, with correlation coefficients being −0.53 – −0.91 (−0.77 on the average) in the former condition and −0.56 – −0.97 (−0.80 on the average) under the latter. Each of the sections with available suspended sediment concentration (SSC) data shows a positive correlation between flat elevation and SSC, with correlative coefficients being 0.35 – 0.97 (0.66 on the average). Only two sections (one in the Changjiang River Estuary and the other in the Hangzhou Bay) which are similar to beaches in sediment grain-size and slope gradient showed a negative correlation between flat elevation and onshore wind frequency and between flat elevation and average wind velocity, with correlative coefficients being respectively −0.57 and −0.69 (−0.63 on the average) in the former situation and −0.61 and −0.75 (−0.68 on the average) in the latter. Other sections did not show uniform relationship between flat elevation and wind conditions. Due to local marine factors the nearshore SSC in the studied area is negatively correlated with the Changjiang River sediment flux (r=−0.78), which results in false negative correlation between flat elevation and river sediment flux. The paper also gives sediment dynamic and morphodynamic explanation for the above correlations. Sea level rise results in the spread of breaker zone from subtidal area to intertidal area and then increases the intertidal water energy. The larger the tidal range, the stronger the tide currents and the easier for the flat to be eroded. The higher the SSC of flood water, the easier for the sediment to deposit down. Because of correlations among the influential factors, it is difficult to give the prime one which dominates the erosion and accretion processes in tidal flats.     

Factorial analysis of annual erosion-accretion cycles of tidal flats in the front area of the southern Changjiang river delta

ＦＡＣＴＯＲＩＡＬＡＮＡＬＹＳＩＳＯＦＡＮＮＵＡＬＥＲＯＳＩＯＮＡＣＣＲＥＴＩＯＮＣＹＣＬＥＳＯＦＴＩＤＡＬＦＬＡＴＳＩＮＴＨＥＦＲＯＮＴＡＲＥＡＯＦＴＨＥＳＯＵＴＨＥＲＮＣＨＡＮＧＪＩＡＮＧＲＩＶＥＲＤＥＬＴＡＹａｎｇＳｈｉｌｕｎ（杨世伦）Ｃｈｅ...     

Distribution and source of main contaminants in surface sediments of tidal flats in the Northern Shandong Province

Twenty-nine samples of surface sediments from tidal flats in the Northern Shandong Province were collected for grain size, heavy metal(Hg, Cu, Pb, Zn, Cd, and Cr), and oil pollution analyses. The geoaccumulation index(Igeo) and factor analysis were introduced to evaluate sediment quality and source of contaminants. The mean concentrations of Hg, Cu, Pb, Zn, Cd, Cr, and oil in the surface sediments in the study area are 0.033, 17.756, 19.121, 55.700, 0.291, 59.563, and 14.213 μg g-1, respectively. The heavy metal contamination in the old delta lobe is slightly higher than that in the abandoned delta lobe; however, the opposite was observed for oil pollution. The Igeo results revealed that the overall quality of the surface sediments in the study area is in good condition. The heavy metal pollution levels show a descending order: Cd Hg Cr Cu Zn Pb, Cd being the main pollutant. The contamination level for in the study area is relatively lower than those for China's other tidal flats. Heavy metals are mainly derived from natural sources of rock weathering and erosion, partly influenced by industrial and agricultural discharge. However, oil pollution is mainly from runoff input, motorized fishing boat sewage, and oil exploitation.     

The distribution feature of size-fractionated chlorophyll a and primary productivity in Prydz Bay and its north sea area during the austral summer

The investigation of size-fractionated chlorophyll a and primary productivity were carried out in three longitudinal sections (63°-69°12'S, 70°30'E, 73°E and 75(30'E) at December 18-26, 1998 and January 12-18, 1999 in Prydz Bay and its north sea area, Antarctica. The results showed that surface chlorophyll a concentration were 0. 16 -3. 99 μg dm-3. The high values of chlorophyll a concentration (more than 3.5 μg dm -3) were in Prydz Bay and in the west Ladies Bank. The average chlorophyll a concentration at sub-surface layer was higher than that at surface layer; its concentration at the deeper layers of 50 m decreased with increasing depth and that at 200 m depth was only 0. 01 -0. 95μg dm -3. The results of size-fractionated chlorophyll a showed that the contribution of the netplanktion to total chlorophyll a was 56% , those of the nanoplankton and the picoplankton were 24% and 20% respectively in the surveyed area. The potential primary productivity at the euphotic zone in the surveyed area wa     

Seasonal variability of salinity budget and water exchange in the northern Indian Ocean from HYCOM assimilation

Based on HYbrid Coordinate Ocean Model (HYCOM) assimilation and observations, we analyzed seasonal variability of the salinity budget in the southeastern Arabian Sea (AS) and the southern part of the Bay of Bengal (BOB), as well as water exchange between the two basins. Results show that fresh water flux cannot explain salinity changes in salinity budget of both regions. Oceanic advection decreases salinity in the southeastern AS during the winter monsoon season and increases salinity in the southern BOB during the summer monsoon season. In winter, the Northeast Monsoon Current (NMC) carries fresher water from the BOB westward into the southern AS; this westward advection is confined to 4°-6°N and the upper 180 m south of the Indian peninsula. Part of the less saline water then turns northward, decreasing salinity in the southeastern AS. In summer, the Southwest Monsoon Current (SMC) advects high-salinity water from the AS eastward into the BOB, increasing salinity along its path. This eastward advection of high-salinity water south of the India Peninsula extends southward to 2°N, and the layer becomes shallower than in winter. In addition to the monsoon current, the salinity difference between the two basins is important for salinity advection.     

1987-2017年粤港澳大湾区城市群的不透水地表扩张与梯度演化

不透水地表是衡量城市化过程与空间扩张的重要特征.本文以我国最具经济活力的城市群-粤港澳大湾区城市(以下简称大湾区)为研究区,采用重心-标准差椭圆与梯度分析等方法,探讨其1987-2017年不透水地表的时空扩张分布特征与演化趋势.结果 表明:①30年来大湾区的不透水地表面积从1839.34km2持续增长至12 385.9...     

Spatial variability of chemical tracers in surface snow along the traverse route from the coast to 1000 km inland at east Dronning Maud Land, Antarctica

1　IntroductionAntarcticicesheetisaburialgroundforatmosphericdeposition .Sincethereiscon tinuousinteractionbetweentheicesheetandtheatmosphere,variousatmosphericsub stancesareinjectedtotheicesheetsequentiallyintimeandspace.Therefore,verticalanalysesoftheicesheetprovideuswithinformationaboutpastclimaticchange (Delmas1 992 ;LegrandandMayewski 1 997)andhorizontalanalysesoftheicesheetprovideuswithknowledgeregardinglong rangetransportofairbornematerials (Kamiyamaetal.1 989;KreutzandMayewski 1 999)…     

基于中国大气环境监测站点的2015—2019年大气质量状况时空变化分析

2013年以来几次严重的雾霾污染事件引起了公众的广泛关注,此后中国实施了一系列有关大气污染防治的政策、法规和措施来改善大气质量。为了分析近年来中国大气质量的时空变化特征,本文选取2015—2019年生态环境部国控站点监测的大气污染关键参数,对比分析了空气质量指数和6种大气污染物的季均、年均浓度变化结果,并利用组合指标分析法和相关分析法探讨了不同大气污染物之间的相关性。结果表明：① PM_2.5、PM₁₀、SO₂、CO和NO₂浓度和AQI均有明显下降,2019年均浓度较2015年均浓度分别下降4.5%、3.84%、7.86%、3.74%、0.95%,AQI下降了19.31%,同时,O₃浓度则上升了0.79%;② 从空间分布来看,中国北方地区PM₁₀、PM_2.5、O₃、NO₂、SO₂、CO年均质量浓度和AQI分别比南方地区高25.2%、18.73%、4.95%、17.6%,32.74%、16.17%、28.3%;③ 从季节性变化规律来看,除了O₃呈现出夏季浓度高,冬季浓度低外,其他5种污染物和AQI都呈现相反的季节变化规律;④ 总体而言,目前中国大气污染以PM_2.5和O₃为主,PM_2.5与NO₂、SO₂、CO之间有极显著的正相关关系（r>0.85,p<0.01）,而O₃与其前体物NO₂和CO之间存在显著的负相关关系（r>0.8,p<0.01）。