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.     

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.     

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.     

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.

     

A microplate solid scintillation counter as a radioactivity detector for high performance liquid chromatography in drug metabolism: validation and applications

Sensitive radioactivity detection following high performance liquid chromatography (HPLC) separation remains a challenge in many drug metabolism studies with radiolabeled compounds. In this work, solid scintillation counting (SSC) after fraction collection into 96-well plates was evaluated as an off-line radioactivity detection method, in comparison with conventional liquid scintillation counting (LSC). The impact of counting time and biological matrix on the quantification of radiolabeled metabolites and parent drug in samples from animal and human absorption, distribution, metabolism and excretion (ADME) studies was investigated. Three different approaches were used to test whether reliable quantification by off-line SSC detection, which requires an approximately constant counting yield during the entire chromatographic run, can be realized: (i) the measurement of radioactivity-spiked biological blank samples without HPLC separation as an extreme case of biological background, (ii) the measurement of radioactivity-spiked HPLC fractions of biological blank samples and (iii) the comparison of radiochromatograms obtained by off-line SSC and LSC of real samples from ADME studies with radiolabeled compounds. Situations in which variations in SSC yield during an HPLC run are likely to lead to significant errors in quantitation were identified and are discussed. However, examples from a number of animal or human ADME studies showed that in the majority of cases off-line SSC provides very similar quantitative data, compared with the reference method of off-line LSC radioactivity detection. Approaches for validation of the off-line SSC approach in critical cases are discussed. The main advantages of off-line SSC, compared with off-line LSC, are lower detection limits and a substantially higher throughput. Several applications of off-line SSC detection in ADME studies are shown.     

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.     

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.     

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.     

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.     

Effects of temperature on the concentration of polycyclic aromatic hydrocarbons (PAHs) adsorbed onto airborne particulates

Summary Daily samples of airborne particulates (143) were collected along the year in La Spezia (Italy). Seasonal variations of atmospheric PAH concentrations, with highest winter values, have been observed. The concentration of PAHs was found to correlate negatively with the mean ambient temperature during the sampling period. Volatilization, photodegradation and seasonal modifications of emissions from urban traffic were found to be a possible explanation of this phenomenon.     

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.     

Significant downward trend of SO2 observed from 2005 to 2010 at a background station in the Yangtze Delta region,China

SO2 is an important gas in atmosphere with great environmental and climate implications.SO2 emission in China has been receiving great attention as the economy grows and the amount of coal consumption has increased in the past few decades.SO2 has been observed from July 2005 to June 2010 at Linan WMO GAW regional station(30.3 °N,119.73 °E,138 m a.s.l.) located in the Yangtze Delta region in eastern China.These observation data are analyzed to understand the trend of regional SO2 background concentration.Strict quality controls are conducted to ensure the temporal comparability of the data.Significant downward trend with ?2.4 ppb/yr(P < 0.0001) of surface SO2 is observed from 2005 to 2010,especially after 2008.The average concentration of SO2 from July 2005 to June 2008 is 14.2±3.1 ppb,which is slightly higher than the mean values of 13.5±5.1 ppb during 1999?2000 and is two folds of the average value(7.1±3.1 ppb) from July 2008 to June 2010.More than 50% of the SO2 has been cut down after 2008 in the Yangtze Delta region due to the implementation of stricter emission control measures.The peak SO2 concentration appears around 10 o’clock in the morning after 2009 while appears at night before 2009.These diurnal variations of SO2 might indicate that after 2009,more SO2 is from the vertical exchange process than from the local accumulation.     

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.     

Seasonal variation, chemical behavior and kinetics of uranium in an unconfined groundwater system

The seasonal changes in the concentration of uranium in an unconfined groundwater system in Cyprus have been investigated and compared to corresponding changes of boron and salinity, to better understand the chemical behavior of uranium in the respective system. Uranium concentration measurements were performed by alpha spectroscopy after selective pre-concentration, whereas boron concentration analysis and electrical conductivity measurements were carried out by photometry using azomethine-H and an electrical conductivity electrode, respectively. The experimental data show that seasonal variations are mainly related to rainwater infiltration and the specific chemical behavior of a species. Increased levels of uranium and boron in natural water systems are attributed to the increased stability of the uranium(VI)-carbonato complexes and the boric acid, which are in natural waters the predominant chemical species for uranium and boron, respectively. Dilution/dissolution processes govern the seasonal concentration changes of uranium and boron in a groundwater system, however redox-reactions resulting in the reduction of U(VI) to U(IV) affect significantly the concentration of uranium in the respective system, particularly under suboxic conditions.     

Characterization of River Natural Organic Matter by High-Performance Size Exclusion Chromatography

The molecular weight of natural organic matter from the Yeongsan and Seomjin Rivers and the discharge from the wastewater treatment plants were analyzed for seasonal characteristics by high-performance size exclusion chromatography. The distribution of molecular weights demonstrated relationships with microbial activity and seasonal variations with temperature. Dissolved organic carbon and total organic carbon for the Seomjin River were from 1.6 to 3.1 mg L^?1; for the Yeongsan River system, these parameters were between 2.0 and 8.0 mg L^?1. There were no significant differences between upstream and downstream organic matter. The biochemical oxygen demand (0.8–2.5 mg L^?1) for the Seomjin River was less than the chemical oxygen demand (2.9–5.0 mg L^?1). Similarly, the biochemical oxygen demand (0.9–4.6 mg L^?1) for the Yeongsan River was lower than the chemical oxygen demand (3.8–10.6 mg L^?1). The molecular weight of aromatic compounds increased as the water temperature decreased in October, whereas the molecular weights of proteins decreased as the water temperature increased. These results suggest that as microbial activity increased, natural organic matter with a smaller molecular weight may be employed as an energy source by microorganisms. As a result, seasonal variation of the water temperature may influence the distribution of organic matter in the rivers based on molecular weight and microbial activity such that the smaller natural organic matter was more readily degraded by microorganisms.