Seasonal,neap-spring variation of sediment concentration in the joint area between Yangtze Estuary and Hangzhou Bay

An analysis of variations in suspended sediment concentration (SSC) over one year is presented for the joint area between the Yangtze Estuary and the Hangzhou Bay. Results suggest that daily SSC presents periodic variations, which correspond with seasonal and neap-spring tidal cycle. SSCs are higher during the winter season and during spring tides when compared with summer and neap-tide conditions. Furthermore, data indicate that wave and tidal currents are the two dominant factors affecting SSC. Although the Yangtze River discharges abundant sediments to the study area, it does not directly affect concentration variations. But the changing path of the Yangtze River plume plays a certain role in the seasonal variations of SSC. Finally, the calculation of bottom stresses suggests that SSC is a function of both wave and tide-induced resuspension.     

Seasonal, neap-spring variation of sediment concentration in the joint area between Yangtze Estuary and Hangzhou Bay

An analysis of variations in suspended sediment concentration (SSC) over one year is presented for the joint area between the Yangtze Estuary and the Hangzhou Bay. Results suggest that daily SSC presents periodic variations, which correspond with seasonal and neap-spring tidal cycle. SSCs are higher during the winter season and during spring tides when compared with summer and neap-tide conditions. Furthermore, data indicate that wave and tidal currents are the two dominant factors affecting SSC. Although the Yangtze River discharges abundant sediments to the study area, it does not directly affect concentration variations. But the changing path of the Yangtze River plume plays a certain role in the seasonal variations of SSC. Finally, the calculation of bottom stresses suggests that SSC is a function of both wave and tide-induced resuspension.     

The change of characteristics of tidal wave in the Changjiang River mouth area since the post-glacial transgression maximum

During the period of the post-glacial transgression maximum (PGTM), there was a huge trumpet estuary in the modern Changjiang River Delta area. The location and the shape of the Paleo-Changjiang River Estuary (PCRE) were much different from those of the present Chang-Jiang River Estuary. The study on the change of characteristics of tidal wave in the Changjiang River mouth area since the PGTM can help to understand better the dynamic development of the Changjiang River Delta. The course curves of tidal level and tidal current velocity during a single tidal cycle for 35 points are calculated, and characteristics of tidal waves in the PCRE and its adjacent area are compared with those of tidal waves in the modern Changjiang River mouth area. The results show that the tidal waves within the PCRE and in its adjacent area during the period of the PGTM belonged to standing wave or a mixture of standing wave and progressive wave. Since then, the tidal wave in the Changjiang River mouth become gradually to be pr     

The change of characteristics of tidal wave in the Changjiang River mouth area since the post-glacial transgression maximum

During the period of the post-glacial transgression maximum (PGTM), there was a huge trumpet estuary in the modern Changjiang River Delta area. The location and the shape of the Paleo-Changjiang River Estuary (PCRE) were much different from those of the present Changjiang River Estuary. The study on the change of characteristics of tidal wave in the Changjiang River mouth area since the PGTM can help to understand better the dynamic development of the Changjiang River Delta. The course curves of tidal level and tidal current velocity during a single tidal cycle for 35 points are calculated, and characteristics of tidal waves in the PCRE and its adjacent area are compared with those of tidal waves in the modern Changjiang River mouth area. The results show that the tidal waves within the PCRE and in its adjacent area during the period of the PGTM belonged to standing wave or a mixture of standing wave and progressive wave. Since then, the tidal wave in the Changjiang River mouth become gradually to be progressive wave with the PCRE being filled and the Changjiang River mouth shifting southeastwards.     

Distribution and forms of phosphorus in tidal flat sediments of the Yangtze Estuary and coast

The distribution and forms of phosphorus (P) were investigated in the tidal flat sediments of the Yangtze Estuary and coast. The total P contents in surface sediments range from 18.0 to 31.4 μmol·g^-1 along the southern coast. The spatial and temporal distribution of P in tidal flats is closely related to the location and pollution resources, especially in association with the variation of hydrodynamic conditions. Significant variations in the forms of P in different sites were observed. P bonded with Ca(Ca-P) is the dominant mineral form in all surface sediments, organic P(Org-P) is lower. Most P is of unstable form, suggesting that P has larger potential activity. P accumulation is the main behavior process between water and sediment in the coastal environment of the Yangtze Estuary.

     

Seasonal changes in coastal dynamics and morphological behavior of the central and southern Changjiang River delta

Seasonal changes in sea level, tidal range, wind, riverine discharges, nearshore SSC (suspended sediment concentration) and bed-level of intertidal flat at 4 different sites were shown. In addition, the statistical relationships between the dynamics and the behavior of the sediment surface were examined. The average intertidal elevation seems negatively correlated to sea level while positively correlated to nearshore SSC. The effect of wind on seasonal cycle of average intertidal elevation is not evident although wind is an important factor governing short-term erosion/accretion events. The influence of riverine discharges on seasonal cycle of deltaic intertidal flats is masked by other factors. It is concluded that seasonality on mudflats is more complicated than on beaches.     

Seasonal changes in coastal dynamics and morphological behavior of the central and southern Changjiang River delta

Seasonal changes in sea level, tidal range, wind, riverine discharges, nearshore SSC (suspended sediment concentration) and bed-level of intertidal flat at 4 different sites were shown. In addition, the statistical relationships between the dynamics and the behavior of the sediment surface were examined. The average intertidal elevation seems negatively correlated to sea level while positively correlated to nearshore SSC. The effect of wind on seasonal cycle of average intertidal elevation is not evident although wind is an important factor governing short-term erosion/accretion events. The influence of riverine discharges on seasonal cycle of deltaic intertidal flats is masked by other factors. It is concluded that seasonality on mudflats is more complicated than on beaches.     

Application of Non-Destructive X-Ray Fluorescence Spectrometry to the Analysis of Suspended Matter in Sea Water

Abstract

In the framework of remote sensing studies concerning coastal transport of pollution in the Northern Adriatic Sea, a method has been developed for the quantitative determination of sulphur, iron, titanium, calcium, phosphorus, silicon, aluminium, magnesium in suspended matter of sea water.

The suspended material was collected by filtering on millipore membrane filters with pore width of 0.45 μ and directly analysed by X-ray spectroscopy. For calibration dried solution and particulate standard samples were used. Limits of sensitivity and precision of the method are reported.

Correlations between the concentration of these elements and the total suspended matter/chlorophyll are discussed.

The aim is to study the geochemical composition of particulate matter and its variations within the geographical site of the sea basin and the seasonal conditions. The approach is to consider aluminium and the other elements normalized on Al. On the basis of a matrix correlation analyses of some sets of data chosen in the restricted area for investigation, some hypothesis on superficial distribution of clay, carbonate, iron hydrous oxides and other mineral detrites, are taken into account. The results confirm the complex situation existing in the offshore area of the Venice lagoon from a geochemical point of view.

The suspended matter seem to be argillaceous in the Southern part of the investigated area and semi-argillaceous with hydrous oxides and carbonates in the Northern part which is influenced by the Piave river.     

Variations of mercury distribution in the water column during the course of a tidal cycle in the Yangtze Estuarine intertidal zone, China

Tidally induced resuspension processes play an important role in the release of mercury (Hg) into the water column, which increases the risk of Hg exposure to estuarine eco-systems. In order to further understand the geochemical activities of Hg in the intertidal area, the temporal variations of dissolved Hg (Hg D ) and particulate Hg (Hg P ) in the water column during the course of a tidal cycle and its geochemical processes were studied in the southern intertidal zone of the Yangtze Estuary, China. The concentrations of Hg D and Hg P varied between 37-612 ng/L and 51-638 ng/L respectively during the tidal cycle. The increase of Hg D was distinguished at the early flood tide and late ebb tide when the water flow rates were higher. The Hg D concentrations were negatively correlated with Hg P (r = 0.523, p < 0.05) and positively correlated with dissolved organic carbon (DOC) (r = 0.605, p < 0.05) in the bottom water, indicating that the Hg D released from the sediments into the overlying water was associated with the simultaneously released colloidal material in the bottom water. The main pathways for the translocation of Hg from the sediments to the overlying water include the processes of desorption from resuspended particles, advection or diffusion from sediments, and the oxidation of resuspended sulfide. The results of principal components analysis (PCA) and Pearson correlation analysis showed that the combined effects of the total suspended substrate (TSS), DOC, pH and dissolved oxygen (DO) influenced the geochemical activities of Hg in the water column during the course of a tidal cycle.     

Mössbauer study of iron-containing atmospheric aerosols

The Mössbauer technique was applied to study the seasonal variations of iron concentration in atmospheric air. The concentration of iron in air was calculated by the area method from the experimental spectra obtained. From the shapes of the Mössbauer spectra it was concluded that iron appears as Fe₂O₃ in the form of ultrafine particles in the superparamagnetic state. The measurements as a function of temperature [from 300 to 75 K) made it possible to estimate the size of iron-containing aerosol particles. Correlation of the seasonal variations of iron concentration with meteorite activity was discussed. This method was applied also in investigations of iron concentration variations with air radioactivity due to nuclear explosions performed in the atmosphere. Attempts were made to find a relation between air pollution and the concentration of iron in the air.     

Polarographic Behaviour of Trazodone

Abstract

Trazodone, which cannot be electrochemically reduced at the dropping mercury electrode, exhibits catalytic proton reduction waves as shown by the strong modifications occuring with variations of pH, concentration, nature of the buffer, ionic strength and presence of organic solvent. The catalytic process is developing three successive waves with rising pH or concentration, depending on the protonation rate or the adsorbed state. The influence of sodium ions indicates a decrease of sorbtivity with the proton concentration. The strong surface character of the wave observed in very acidic media decreases gradually on behalf of a more pronounced bulk character with increasing pH. The wave recorded in neutral media is of analytical interest, a linear calibration curve being plotted in the 2.10^?6 M to 1.10^?3 M concentration range.     

Fluoride accumulation in barnacles and mussels in the lagoon of Venice.

As some industries are likely to discharge fluoride into the Lagoon of Venice, especially in the area of Portomarghera, a survey was undertaken of the environmental levels of this element. Fluoride concentrations in the waters surrounding the industrial area ranged from 1.53 mg 1^?1 (chlorinity: 16.6‰) to 3.14 mg 1^?1 (15.1‰) and all values exceeded the levels considered normal for seawater having the same chlorinity.However determination of the fluoride content of water alone tells little about the entrance of this element into food chains. It therefore seemed appropriate to monitor the environment by examining organisms for their ability to accumulate fluoride in tissues. The organisms chosen for this purpose were the crustacean $\text{Balanus}$$\text{amphitrite}$ (barnacles) and the mollusk $\text{Mytilus galloprovincialis}$ (mussels). Both species were found to accumulate fluoride in their soft tissues to above-ambient levels. Maximum fluoride concentrations found for barnacles and mussels were 81 ± 6 μg g^?1 and 85 ± 20 μg g^?1 (dry weight) respectively; the concentration factor, calculated as the ratio of mean concentration of fluoride in dry soft tissue of the animal to mean concentration in water, was of the order of 10² for both species. Moreover seasonal variations in soft tissue fluoride concentrations were recorded. These seasonal variations are probably related to the reproductive cycle; in both species the highest fluoride levels were found during the spawning periods, that is in summer in the case of the barnacle and in winter and spring in the case of the mussel.These species, especially during their spawning periods, are indirectly or directly included in the human diet. Since fluoride can be toxic, more attention should be paid to levels in environments, like the Lagoon of Venice, in the vicinity of highly industrialized comunities in which a large amount of local seafood is included in the diet.     

Determination of Lead,Cadmium and Mercury in Surface Marine Sediments and Mussels

Abstract

Lead, cadmium and mercury were determined in sediments and mussels, and the ability of these indicators to record metal variations in coastal marine environment is described in this work. The results of an extended investigation of the status of three gulfs at Northern Greece are given, regarding the content of these metals in surface sediments and Mytilus galloprovincialis. The samples were collected during a four-year period. The total concentration of the above heavy metals was determined after digestion of the samples by suitable mixtures of acids, including nitric, perchloric and hydrofluoric acid. The digestion was carried out in a steel pressurised bomb with closed teflon vessels. Lead and cadmium were determined by means of electrothermal atomic absorption spectrometry (ETAAS), and mercury by cold vapour atomic absorption spectrometry (CVAAS). The results were statistically evaluated by analysis of variance, and emphasis was given to annual, seasonal and spatial sources of variation. The annual changes during the last four years and the spatial distribution of heavy metals load is also discussed.     

Denitrification in tidal flat sediment, Yangtze estuary

Sediment denitrification rates at six Yangtze River estuary tidal flat locations (mudflats and salt marshes) were measured from July 2003 to October 2004. In winter and summer, spatial distribution of denitrification rates was not great in the Yangtze estuary, while in spring and autumn, denitrification rates had a great spatial distribution because of the human activity effect. The temporal change of denitrification rates was greater. They ranged from 0.2 to 36.4 μmolN·m⁻²·h⁻¹, and were higher in the summertime. The annual average of sediment denitrification rate was 18.2±12.3 μmolN·m⁻²·h⁻¹ in the middle tidal flat and 15.1±9.45 μmolN·m⁻²·h⁻¹ in the low tidal flat in the Yangtze estuary. Data analysis indicated that the temperature was the primary factor controlling the process of denitrification (significant positive correlation, P<0.01); at the same time, the content of sediment total nitrogen (TN) and the molar ratio of sediment carbon and nitrogen (C/N) had significant positive correlation (P<0.05) and negative correlation (P<0.05) with denitrification rates, respectively. In the Yangtze estuary, increasing of water salinity had no significant inhibition of denitrification because of the wide change range of water salinity. Supported by the National Natural Science Foundation of China (Grant Nos. 40173030, 40571006 and 40131020), the Science & Technology Department of Shanghai (Grant Nos. 05DZ120007 and 05JC14059) and China Postdoctoral Science Foundation.     

华中地区偏远站点金沙站气态污染物的变化特征

对于2006年6月到2007年7月在华中地区的金沙区域大气本底站站址科学论证实验期间获得的近地面O₃、SO₂、NO_x和CO等观测资料进行分析, 讨论其浓度水平、变化特征和影响因素. 结果表明, 观测期间O₃、SO₂、NO_x和CO的平均浓度分别为24.6±17.0 ppb、2.8±5.5 ppb、5.6±5.5 ppb和502±222 ppb, 低于同纬度位于长三角地区的临安大气本底站的同期观测水平. 金沙站局地O₃光化学生成不显著, 一次污染物的平均日变化比较平稳, 有别于临安和位于华北地区的上甸子大气本底站的变化特征. 由于观测点相对孤立且海拔相对较高, 可受到自由大气的影响, 使O₃浓度持续多日保持较高水平, 而一次污染物浓度很低, 相对湿度显著降低且与O₃浓度变化明显反相关. 因此, 该站数据可以在更大的尺度上反映出区域本底信号的变化情况.     

Spatial and temporal distribution of environmental markers from Coastal to Plateau areas in Antarctica by firn core chemical analysis

The chemical analysis of shallow firn cores sampled in coastal and plateau areas in Northern Victoria Land and along a transect from Talos Dome to Dome C (East Antarctica, Pacific Ocean sector) allowed a global view of spatial and temporal changes in chemical composition of snow depositions over the last 100 years. Variations in concentration of primary (sea spray) and secondary (biogenic emission, atmospheric inputs) source markers were observed and discussed as a function of distance from the sea and altitude.

In the stations characterized by relatively high snow accumulation rates, the sub-sampling resolution was sufficient to obtain a stratigraphic dating by using the periodical variations of seasonal markers. In these stations, a subdivision in “summer” and “winter” samples was carried out in order to study the seasonal changes of the contributions of the measured compounds to the snow composition as elevation and distance from the sea increase.

Some evidence of post-depositional effects which are able to change the original deposition of chloride and nitrate, was observed at stations with low accumulation rates. The reliability of the depth/concentration profile of these substances for reconstructing past deposition was also discussed.     

Understanding Variations in Pollution Levels of Marine Biota: The Particle Concentration Effect

Abstract

Important seasonal variations in contamination levels of marine biota by lipophile organic compounds are noted when overviewing pollution data, even when data are normalized on lipid content. We therefore tried to understand part of the observed variations in contamination levels between watermasses (different geographic areas or seasons) by studying lipophile pollutant bioconcentration at the origin of the food chain.

The uptake kinetics and bioconcentration of ¹⁴C-DDT, by five species of marine phytoplankton were investigated in laboratory experiments. An inverse relationship, representative for all species studied, was noted between the phytoplankton bioconcentration factor and the phytoplankton biomass (both normalized on organic carbon). No differences in bioconcentration factors among different phytoplankton species, with different cell sizes and biochemical characteristics, were noted, when data were standardized on organic carbon content. The importance of the Particle Concentration Effect (PCE) on the bioconcentration factor of micro-organic pollutants is, in this study, further illustrated with data on pollution of North Sea field samples. It is shown that within a specific range of organic matter, normalization of pollution data on particulate or phytoplankton biomass will account for part of the geographic and seasonal differences in organochlorine contamination levels noted for marine watermasses.     

Ra-isotopes around a phosphate fertilizer complex in an estuarine system at the Southwest of Spain

The presence of²²⁴Ra and²²⁶Ra in waters from an estuarine system which surrounds a phosphate fertilizer complex (southwest Spain) has been studied. The high activities obtained confirm that an important radiological impact from such industrial complex on its close environment is being produced. The influence of tidal oscillations and seasonal conditions on activity concentration has also been investigated.     

Modeling of <Superscript>226</Superscript>Ra behavior in a Spanish estuary affected by the phosphate industry

The Odiel and Tinto rivers, southwest Spain, form a fully mixed estuary. An industrial area that includes a complex dedicated to the production of phosphate fertilizers is located by the Odiel River. This complex released phosphogypsum wastes directly to the Odiel River and also disposed them on open air piles located by the Tinto River. Due to new EU regulations, wastes are not directly released to the Odiel from 1998 on, although they are still disposed on the open air piles. The behavior of ²²⁶Ra in a system like this estuary is complex, since radionuclides are affected by tidal actions and interactions with sediments through adsorption/desorption reactions and erosion/deposition processes. A numerical 2D depth-averaged model of the estuary has been developed, including processes mentioned above. It has been applied to reproduce experimental data measured after a release from the industrial complex in the Odiel River and after an accidental release in the Tinto River from the gypsum piles. The model has also been applied to simulate the self-cleaning process observed in the estuary after the direct releases from the fertilizer complex were stopped.     

Average daily and annual courses of222Rn concentration in some natural medium

Simultaneous measurements of the²²²Rn concentration in the outdoor atmosphere of Bratislava and in the soil air over one year period have been made. Daily and seasonal variations of the²²²Rn concentration in both media were found. Some attributes of these variations as well as methods of measurements are presented in this work.