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1.
Dissolved and particulate trace metals (Cu, Cd, Pb, Zn, Ni, Fe and Mn) measured at six stations along the Scheldt estuary in October/November 1978 are compared with more recent data. Based on Ca content in the suspended matter, three distinct geochemical regions could be distinguished: the upper estuary (salinity 1–7) dominated by fluvial mud, mid-estuary (salinity 7–17) where the composition of the suspended matter remained relatively constant, and the lower estuary where marine mud prevailed. Re-suspension of sediments is the major factor controlling the composition of the particles in the upstream region. Anoxic conditions prevailed in the upper part of the estuary extending to a salinity of 15 in 1978, while at present the seaward boundary of the anoxic water body is located at less saline waters. Furthermore, the present-day metal load is much lower than in 1978. As a consequence of the changed situation, maxima in dissolved concentrations of redox-sensitive metals in the mid/lower estuary have moved as well, which affects the trace metal re-distribution pattern. In the anoxic zone, exchange processes between dissolved and particulate metal fractions were strongly redox regulated, with Fe and Mn as excellent examples. Iron was removed from the dissolved phase in the early stages of mixing resulting in an increase in the suspended particulate matter of the leachable ‘non-residual' Fe fraction from 2 to 3.5%. Due to its slower kinetics, removal of Mn from solution occurred in mid-estuary where oxygen concentrations increased. Cu, Cd and Zn on the contrary were mobilised from the suspended particles during estuarine mixing. External inputs of Pb, and to a lesser extent of Cu, in the lower estuary resulted in the increase of their particulate and the dissolved concentrations. Calculated Kd (distribution coefficient) values were used to assess the redistribution between the dissolved and particulate phase of the investigated metals. Due to the existence of the anoxic water body in the upper estuary, the importance of redox processes in determining the Kd values could be demonstrated. The sequence of Kd values in the upper estuary (Fe, Cd, Zn, Pb > Cu > Ni, Mn) is significantly different from that in the lower estuary (Fe > Mn > Pb, Ni, Zn, Cu, Cd). Thus, in such a dynamic estuary single metal-specific Kd values cannot be used to describe redistribution processes.  相似文献   

2.
Anoxic sulfidic waters provide important media for studying the effect of reducing conditions on the cycling of trace metals. In 1987–1988, dissolved and particulate trace metal (Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb) concentrations were determined in the water column of the anoxic Drammensfjord basins, southeastern Norway. The iminodiacetic acid type chelating resin (Chelex 100) was used for the preconcentration of trace metals. The trace metal concentrations were determined using atomic absorption spectrophotometry (AAS), differential pulse polarography (DPP), and differential pulse-anodic stripping voltammetry (DP-ASV).It was observed that the trace metals Mn and Fe were actively involved in the processes of redox cycling (oxidationreduction and precipitation-dissolution) at the O2/H2S interface. The dissolved concentrations of Mn, Fe and Co showed maxima just below the O2/H2S interface. The seasonal enhancement in the maxima of both dissolved and particulate Mn and Fe at the redox cline is mainly governed by the downward movement of water which carries oxygen. An association of Co with the Mn cycle was observed, while the total dissolved Ni was decreased by only 10–35% in the anoxic waters. The dissolved concentrations of Cu, Zn, Pb and, to a lesser extent, Cd decreased in the anoxic zone.  相似文献   

3.
The ratio of marine to fluvial suspended matter in the Scheldt Estuary was calculated by applying factor analysis to a data set of elemental concentrations. The data set consisted of 98 samples collected under various river discharge conditions. Each sample was analysed for the concentration of Cr, Pb, Fe, Mn, Ni, Co, Ba, Zn, Cu, Cd, S, Ca, Sr, Ag, Sn and Na. Five linearly independent processes were found to describe the variability of the elemental concentrations: (1) the supply of fluvial material to the mixing zone; (2) manganese oxidation in the transition area between the anoxic upper estuary and the oxic lower estuary; (3) the supply of marine material to the mixing zone; (4) a phytoplankton bloom in the lower estuary; and (5) the formation of insoluble metal sulphides in the anoxic high-turbidity zone. Scores of the first and third factor were used to calculate the ratio of marine to fluvial suspended matter in the mixing zone. Information on the origin of both the inorganic and organic fraction of suspended matter was obtained in this way.  相似文献   

4.
《Marine Chemistry》2001,75(3):229-248
Dissolved and particulate mercury and methylmercury concentrations were determined in the Southern Bight of the North Sea and the Scheldt estuary in the period 1991–1999. Mercury and methylmercury concentrations are higher before 1995 than after 1995, especially in the fluvial part.The North Sea: In the offshore stations, dissolved Hg concentrations are generally higher in winter than in summer while the reverse is true for particulate Hg KD values (KD=the concentration of particulate Hg (HgP in pmol kg−1) divided by the concentration of dissolved Hg (HgD in pmol l−1)) range from 100,000 to 1000,000 l kg−1. Dissolved methylmercury concentrations vary from 0.05 to 0.25 pmol l−1 in summer and from d.l. to 0.23 pmol l−1 in winter and particulate methylmercury concentrations from 1.8 to 36 pmol g−1 in summer and from 0.9 to 21 pmol g−1 in winter. The KD ranges from 9,000 to 219,000 l kg−1.The Scheldt estuary: In winter, dissolved Hg concentrations are elevated in the upper estuary, decrease exponentially in the low salinity range followed by a very slow decrease towards the mouth. In summer, they are low in the fluvial part, increase in the low salinity range or in the mid-estuary and sometimes show an increase in the lower estuary. Particulate Hg concentrations do not show any seasonal trend.Dissolved MMHg concentrations are much lower in winter, when maximum concentrations are found in the upper estuary, than in summer. In summer, the MMHg concentrations are low at low salinity, they show a first increase in the salinity range from 3 to 12, a decrease in the mid-estuary and a second increase in the lower estuary.The highest particulate MMHg concentrations are found in the upper estuary, while in the lower estuary generally lower and more constant values are observed. The ratio of dissolved MMHg to dissolved Hg (cruise averages between 1.3% and 20%), is higher than the ratio of particulate MMHg to particulate Hg (cruise averages of 0.27–0.90%). The KD values for MMHg are lower in the summer (30,000–65,000) than in autumn and winter (77,000–114,000).The Scheldt river: In the fluvial part of the Scheldt, dissolved increases in the most upstream stations, while particulate Hg shows no particular pattern. Dissolved MMHg ranges from 0.1 to 0.39 pmol l−1 and particulate MMHg from 3.1 to 43.5 pmol g−1. The MMHg concentrations are comparable to those found in the estuary and no seasonal variations could be observed.  相似文献   

5.
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 O2H2S 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   

6.
Dissolved concentrations of Cu, Pb, Zn, and Cd were measured in the Changjiang estuary and its adjacent waters. The results indicate that the ranges of dissolved heavy metals in the studied waters are as follows: Cu = 1.0−6.9 μg/L, Pb = 0.10−0.39 μg/L, Zn = 3.2−9.1 μg/L, and Cd = 0.011−0.049 μg/L. The behavior of the dissolved Cu was essentially conservative, but a high scatter was observed for the high salinity samples, and it is the same with Zn and Pb. The overall concentrations of dissolved Cd increase with the salinity. There were no differences between the surface, middle, and bottom layer for Cu, Pb, Zn, and Cd. Seasonal changes of their averages were not obvious on the whole. River discharges, sedimentary dynamics, and biological processes might determine the profiles of heavy metals. The text was submitted by the authors in English.  相似文献   

7.
The effect of the flood water salinity on the mobility of heavy metals was studied for intertidal sediments of the Scheldt estuary (Belgium). Soils and sediments of 4 sampling sites were flooded with water of different salinities (0.5, 2.5, and 5 g NaCl L−1). Metal concentrations were monitored in pore water and surface water. To study the potential effects of flood water salinity on metal bioavailability, duckweed (Lemna minor) was grown in the surface water. The salinity was found to primarily enhance the mobility of Cd and its uptake by duckweed. Cadmium concentrations in pore water of soils and sediments and surrounding surface waters significantly exceeded sanitation thresholds and quality standards during flooding of initially oxidized sediments. Moreover, the effect was observed already at lower salinities of 0.5 g NaCl L−1. This implies that risks related to Cd uptake by organisms and Cd leaching to ground water are relevant when constructing flooding areas in the brackish zones of estuaries. These risks can be reduced by inducing sulphide precipitation because Cd is then immobilised as sulphide and its mobility becomes independent of flood water salinity. This could be achieved by permanently flooding the polluted sediments, because sulphates are sufficiently available in the river water of the brackish part of the estuary.  相似文献   

8.
The environmental behavior of nonylphenol ethoxylates (A9PEO) in the Rhine and Scheldt estuaries (The Netherlands) was investigated using a hydrodynamic advection-dispersion fate model (ECoS 3). The model was validated with the results of field studies, in which A9PEO as well as the metabolites nonylphenoxy ethoxy acetic acids (A9PEC) and nonylphenol (NP) were analyzed in sediment, water and suspended particulate material (SPM) samples using LC–MS methods. Maximum actual concentrations observed in surface sediments were 620, 560 and 1100 ng g−1 d.w. for A9PEO, A9PEC and NP, respectively. In the dissolved phase, maximum observed concentrations amounted to 1100 ng L−1 (A9PEO), 6500 ng L−1 (A9PEC) and 960 ng L−1 (NP). Clear spatial trends were observed for dissolved A9PEO and metabolites in the Scheldt estuary, with decreasing concentrations going downstream. This concentration decrease was steeper than for conservatively behaving compounds. This trend was not visible in the Rhine estuary. The fate model was applied to A9PEO and metabolites in both estuaries. Transport of chemicals in the water column was considered as a longitudinal one-dimensional process through a number of estuary segments. For the Rhine estuary, to cope with the stratification observed, a model structure was chosen consisting of two water layers above each other, between which exchange was possible. Sedimentation/erosion processes were included in the model. A biodegradation scheme was incorporated, and rates were adjusted to fit the calculated concentration profiles with the actual profiles of both A9PEO and its metabolites. In this way, field biodegradation rates for A9PEO, A9PEC and NP could be derived, which were in agreement with values from literature. The measured dissolved concentration profiles as well as salinity and concentrations of SPM could be described successfully by the model. The concentrations calculated in SPM and sediment were of the same order of magnitude as the actual concentrations. In the Rhine estuary, additional sources of A9PEO had to be included to account for the relatively high concentrations in the middle of the estuary. The fate model for the Scheldt estuary could be slightly improved by using salinity-dependent biodegradation rates. A sensitivity analysis of the model showed that in the Scheldt estuary, the environmental process with the strongest influence on the dissolved concentration profiles of A9PEO and metabolites is biodegradation. In the Rhine estuary, the water residence time is too short for significant biodegradation to occur, and in this estuary the dissolved concentration profiles were mainly influenced by the additional A9PEO sources.  相似文献   

9.
The concentrations of the trace metals Cd, Cu, Fe, Ni, Pb and Zn in the Göta River estuary have been investigated. The following metal fractions have been determined: acid-leachable, dissolved, labile and particulate.The estuary represents a salt wedge type estuary and is situated in a densely populated region of Sweden. The metal concentrations found for the dissolved fraction is in the range of what can be considered as background levels for freshwater. It is difficult to evaluate any estuarine processes other than conservative mixing for Cd, Cu, Ni and Zn. The dissolved levels in the freshwater end member are Cd, 9–25 ngl?1; Cu, 1·1–1·4 μgl?1; Fe, 20–75 μg l?1: Ni, 0·7–0·9 μg l?1: Pb 0·09–0·2 μg l?1; and Zn, 6–7 μg l?1:The results from the acid-leachable fraction show that at high suspended load the particles sediment in the river mouth. The trace metal levels in this fraction are subject to large variations.  相似文献   

10.
We describe the effect of heavy metals Zn, Cd, Pb and Cu on the induction of methallothioneins on the clam Scrobicularia plana along a salinity gradient simulated under laboratory conditions. The clams were exposed to constant heavy metal concentrations in a dynamic estuary simulator during a 15-day assay to investigate possible induction of metal-binding proteins in them. The concentration of heavy metals in water was analysed. Clams were analysed for methallothionein concentrations. The speciation of Zn, Cd, Pb and Cu along the salinity gradient was modelled. Zn showed the highest concentrations and its prevalent species was the free ion. Intersite differences have been observed in methallothionein concentration and related to the salinity gradient. It seems that synthesis of methallothioneins is the result of physiological forces acting in concert with the changes in the chemical speciation of metals, owing to the trace metals uptake is controlled by means of an interaction of physiology and physicochemistry.  相似文献   

11.
A combination of CTD casts, discrete bottle sampling and in situ voltammetric microelectrode profiling was used to examine changing redox conditions in the water column at a single station south of the Bay Bridge in the upper Chesapeake Bay in late July/early August, 2002–2005. Short-term (2–4 h) fluctuations in the oxic/suboxic/anoxic interface were documented using in situ voltammetric solid-state electrodes. Profiles of dissolved oxygen and sulfide revealed tidally-driven vertical fluctuations of several meters in the depth and thickness of the suboxic zone. Bottom water concentrations of sulfide, Mn2+ and Fe2+ also varied over the tidal cycle by approximately an order of magnitude. These data indicate that redox species concentrations at this site varied more due to physical processes than biogeochemical processes. Based on analysis of ADCP data, tidal currents at this station were strongly polarized, with the principal axis of tidal currents aligned with the mainstem channel. Together with the chemical data, the ADCP analysis suggests tidal flushing of anoxic bottom waters with suboxic water from north of the site. The present study is thus unique because while most previous studies have focused on processes across relatively stable redox interfaces, our data clearly demonstrate the influence of rapidly changing physical mixing processes on water column redox chemistry.Also noted during the study were interannual differences in maximum bottom water concentrations of sulfide, Mn2+ and Fe2+. In 2003, for example, heavy spring rains resulted in severe hypoxia/anoxia in June and early July. While reported storm-induced mixing in late July/early August 2003 partially alleviated the low-oxygen conditions, bottom water concentrations of sulfide, Mn2+ and Fe2+ were still much higher than in the previous year. The latter implies that the response time of the microbial community inhabiting the suboxic/anoxic bottom waters to changing redox conditions is slow compared to the time scale of episodic mixing events. Bottom water concentrations of the redox-sensitive chemical species should thus be useful as a tracer to infer prior hypoxic/anoxic conditions not apparent from ambient oxygen levels at the time of sampling.  相似文献   

12.
The distribution of toxic cyanobacterium Microcystis cf. aeruginosa in the severely polluted Golden Horn Estuary was studied from 1998 to 2000. Microcystis persisted at the upper estuary where the water circulation was poor and values ranged between 2.9 × 104 and 2.7 × 106 cells ml−1 throughout the study. Simultaneously measured physical (salinity, temperature, rainfall and secchi disc) and chemical parameters (nutrients and dissolved oxygen) were evaluated together with Microcystis data. Although the Microcystis blooms generally occur in summer due to the increase in temperature, the blooms were recorded in winter in the present study. The abundance of Microcystis depended on the variations in salinity and both blooms were recorded below S = 2. A moderate partial correlation between Microcystis abundance and salinity was detected in the presence of temperature, dissolved oxygen and precipitation data (r = −0.561, p = 0.002). The M. cf. aeruginosa abundance was low in the summer when the salinity was higher than winter. A remarkable increase in the eukaryotic phytoplankton abundance following the improvements in the water quality of the estuary occurred, whilst the Microcystis abundance remained below bloom level.  相似文献   

13.
The adsorption of trace metals (Pb, Zn, Cu, Cd and Hg) on calcite, kaolinite and bentonite has been studied in Krka river water of various salinities (S = 3, 20 and 38‰).Model experiments were performed at pH 8 in natural water and in UV-irradiated water samples to determine the importance of natural soluble organic matter. Cold vapour atomic absorption spectrometry was used for the Hg determination, and a differential pulse anodic stripping voltammetry (DPASV) method for determination of other trace metals, using either a hanging mercury drop electrode or a mercury-coated glassy carbon working electrode. The following results have been obtained on calcite:
1. (1) a powerful absorption of Pb and Zn was observed for both natural and UV-irradiated waters at S=20‰;
2. (2) a strong adsorption of Hg was observed in natural water, and significantly lower adsorption in UV-irradiated water at all three salinities, particularly at low salinity;
3. (3) Cd adsorption was of medium intensity in both waters at S=20‰;
4. (4) Cu was practically not adsorbable in both waters at S=20‰ if the total Cu ion concentration was lower than the copper complexing capacity value;
5. (5) Cu adsorption was of a medium intensity at S=38‰. It has not influenced by the EDTA model ligand.
Trace metals Pb, Zn and Cu are adsorbable on kaolinite and bentonite at S=38‰, whereas Cd is practically not adsorbed. The Krka River is a calcareous river, which supplies the sea with calcite and aluminosilicates. In the light of our model experiments, we suggest that the self-purification of the Krka River is remarkable in respect to Pb, Zn and Hg; this occurs to a lesser extent for Cu, and is negligible in the case of Cd.  相似文献   

14.
大辽河口溶解态重金属的变化特征及影响因素研究   总被引：4，自引：0，他引：4  
分别于2009年7月和2010年4月在大辽河口采集表层水样,测定了水体中溶解态Cu、Pb、Zn、Cd和Cr的含量,并对其分布特征及影响因素进行探讨。结果表明:除2010年4月Cu,及个别站位Pb、Zn含量较高外,表层水重金属含量均达到国家一类海水水质标准。2010年4月表层水中Cu、Pb、Zn、Cr的浓度大于2009年7月,2航次Cu、Cd、Cr的含量由河向海呈逐渐上升趋势,2010年4月Pb、Zn的含量表现为河口段高于口外海滨。重金属的含量和分布主要受径流量、潮汐作用以及风浪扰动的影响。  相似文献   

15.
The early diagenesis of trace elements (V, Cr, Co, Cu, Zn, As, Cd, Ba, U) in anoxic sediments of the Achterwasser, a shallow lagoon in the non-tidal Oder estuary in the Baltic Sea, was investigated in the context of pyrite formation. The dissolved major redox parameters show a two-tier distribution with transient signals in the occasionally re-suspended fluid mud layer (FM) and a permanently established diagenetic sequence in the sediment below. Intense microbial respiration leads to rapid depletion of O2 within the uppermost mm of the FM. The reduction zones of Mn, Fe and sulfate overlap in the FM and in the permanently anoxic sediment section which appears to be a typical feature of estuarine sediments, under low-sulfate conditions. Degrees of pyritization (DOP) range from 50% in the FM to remarkably high values > 90% at 50 cm depth. Pyrite formation at the sediment surface is attributed to the reaction of Fe-monosulfides with intermediate sulfur species via the polysulfide pathway. By contrast, intense pyritization in the permanently anoxic sediment below is attributed to mineral growth via adsorption of aqueous Fe-sulfide complexes onto pyrite crystals which had originally formed in the surface layer.The studied trace elements show differential behavior patterns which are closely coupled to the diagenetic processes described above: (i) Zn, Cu and Cd are liberated from organic matter in the thin oxic layer of the sediment and diffuse both upwards across the sediment/water boundary and downwards to be trapped as monosulfides, (ii) V, Cr, Co and As are released during reductive dissolution of Mn- and Fe-oxyhydroxides, (iii) U removal from pore water occurs concomitantly to Fe reduction in the FM and is attributed to reduction of U(VI) to U(IV), (iv) the Ba distribution is controlled by reductive dissolution of authigenic barite in the sulfate reduction zone coupled with upward diffusion and re-precipitation. The incorporation of trace elements into pyrite is most intense for Co, Mn and As, intermediate for Cu and Cr and little to negligible for U, Zn, Cd, V and Ba. The observed trend is largely in agreement with previous studies and may be explained with differing rates for ligand exchange. Slow and fast ligand exchange and thus precipitation kinetics are also displayed by downcore increasing (Mn, Cr, Co and As) or constantly low (Zn, Cu, Cd) pore water concentrations. The downward increasing degrees of trace metal pyritization (DTMP) for Co, Cu, Zn and As are, in analogy to pyrite growth, assigned to adsorption of sulfide complexes or As oxyanions onto preexisting pyrite minerals.  相似文献   

16.
Between 1980 and 1984 extensive studies were carried out in the Baltic Sea on trace metals (Cd, Co, Cu, Fe, Hg, Mn, Ni, Pb and Zn) in water, suspended matter and sediments. The results enabled the influence of different factors on metal distribution patterns to be considered. The vertical profiles of dissolved and particulate metals in waters of the central deep basins reflect influences caused by oxygen deficiency and anoxic conditions in near-bottom water layers. Peculiarities at Station BY15 in the Gotland Deep included high dissolved Fe, Mn and Co concentrations and remarkable enrichment of Zn (0.64%), Cd (51 μg g−1) and Cu (0.15%) in particulate matter from the anoxic zone. Manganese-rich particles were accumulated above this layer.In fine-grained soft sediments below anoxic deep waters, maximum contents of Cd, Cu and Zn were observed, relative to other coring sites, between Bothnian Bay and Lübeck Bight. The Hg content in sediments probably reflects the joint flocculation with organic matter. Land-based sources seem to play the leading part for maximum lead contents.  相似文献   

17.
Oxy-anionic species of V, As, Se, Mo, Sb, Te and W were measured in solution and suspension in samples obtained during several cruises in the Dutch Wadden Sea, the offshore region of the Southern Bight (North Sea) and in the estuaries of the Rhine and Scheldt. Dissolved concentrations at salinities above 34·5 × 10?3 ( = 34·5%. S) agreed generally well with published open ocean values. It is suggested that Se speciation differs from the open ocean.In the Wadden Sea, concentrations of V, Se, Mo and Sb were linearly related to salinity (10–35 × 10?3). The good agreement between measured and extrapolated values at a salinity of 0·5 × 10?3 suggests conservative behaviour in the Rhine estuary (with residence time of freshwater in the order of a few days).Dissolved concentration vs. salinity plots in the Scheldt estuary (residence time 2–3 months) showed pronounced minima and maxima. These occurred in the low or medium salinity range for V, As and Sb. Linear behaviour was observed for Se and Mo (in some cases, relatively large differences between cruises were detected). Deviations from linearity in the plots are interpreted in terms of thermodynamic equilibrium conditions involving species with different solubilities (V), local input from land (As, Se, Sb, Te) and removal from solution (As), probably through coprecipitation with Fe(OH)3.In the offshore samples, the contributions of particulate forms to the total element concentrations were small (<15%). At higher SPM concentrations (about 30 mg dm?3), this percentage remained small for Se, Mo and Sb (<15%); it was substantial for V and As (25–50%).  相似文献   

18.
In the anoxic hypersaline Tyro and Bannock Basins of the eastern Mediterranean, extremely high concentrations of Co (0.015%), Cu (1.35%) and Zn (0.28%) were found in suspended matter collected at the sharp interface between seawater and the anoxic brine. The high particulate Co, Cu and Zn concentrations can be explained by the sharp increase in dissolved sulphide at these interfaces, and the resultant precipitation of metal sulphides. The particulate As, Sb and Mo concentrations also showed a sharp maximum at or close to the interface. However, the contributions of As, Sb and Mo contents in suspended matter to the total concentrations in the water column are small. Scanning electron microscopy-energy-dispersive X-ray analysis (SEM-EDAX) of suspended particulate matter from the Tyro Basin revealed spherical particles strongly enriched in Fe, Cu and Zn at the seawater-brine interface.  相似文献   

19.
Concentrations of P and of heavy metals (Zn, Cd, Pb, Cu) were determined in sediment cores from the Peel-Harvey Estuary in Western Australia. Two cores were extracted, each representing one of the two basins of the estuary. Sediments were dated by surplus210Pb, by137Cs and by changes in the Fe/S ratio. Increasing exports of P from the mainly agricultural catchments have resulted in more than a doubling of both total P and acid extractable inorganic P in sediments of the estuary. Accumulation of P in the estuary is less than expected for complete retention of inputs of P from the major tributaries. Historical data show that since 1950 average concentrations of dissolved inorganic P have approximately doubled in the Peel Inlet and increased by times seven in the Harvey Estuary. Increases in concentrations in surface sediments of acid extractable Zn, Cd, Pb and Cu are noticeable in the Peel Inlet, and of Zn and Cd in the Harvey Estuary. The greatest increase, relative to background, is shown by Zn. Concentrations of extractable Zn and Cd in surface sediments are similar to those estimated from average concentrations in the water column for equilibrium adsorption to organic matter in sediments. Extractable Pb is greater than estimated for equilibrium adsorption to sediments. Extractable Cu is of the order of what can be expected for equilibrium adsorption to sediments in the Peel Inlet, but is less than expected in the Harvey Estuary.  相似文献   

20.
The ratio of dissolved cadmium (Cd) to phosphate (PO4) in the subtropical coastal area of Ishigaki Island, Okinawa, Japan, was investigated. Twenty vertical seawater samplings were carried out once a month from May 2008 to January 2010. In order to examine how the Cd/PO4 ratio in seawater varies with the oceanographic conditions (i.e., the water temperature–salinity characteristics), the water masses at the study sites were classified into two types: group 1 with a water temperature of >25°C and a salinity range of 34.0–34.4, and group 2 with a water temperature of <25°C and a salinity of >34.4. A different phytoplankton assemblage was observed in each water mass defined. Different Cd/PO4 ratios were obtained for the two water mass types, due to the differences between the types in terms of the environmental conditions such as the water temperature–salinity (T–S) characteristics and phytoplankton assemblages, as well as possible variations in the concentrations of dissolved iron, zinc, manganese, and CO2 in seawater in each water mass.  相似文献   

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