Investigation of the lateral spread of erbium ions implanted in silicon crystal

The erbium ions at energy of 400 keV and dose of 5×10¹⁵ ions/cm² were implanted into silicon single crystals at room temperature at the angles of 0°, 45°and 60°. The lateral spread of 400 keV erbium ions implanted in silicon sample was measured by the Rutherford backscattering technique. The results show that the measured values were in good agreement with those obtained from the prediction of TRIM'98 (Transport of Ions in Matter) and SRIM2006 (Stopping and Range of Ions in Matter) codes.     

Adsorption of lead and cadmium ions on calcite in the Krka estuary

The adsorption of Pb²⁺ and of Cd²⁺ ions from calcareous Krka river water of various salinities (3, 14, 20 and 38 psu) on calcite (CaCO₃, Merck p.a.) was investigated. Simultaneous adsorption of Pb²⁺ and Cd²⁺ ions was studied as well. The results suggest that the two ions are adsorbed at different calcite surface sites; Pb²⁺ remained firmly bound to calcite at all salinities, whereas Cd²⁺ was firmly bound at low salinities and released at high salinities. Dissolved natural organic ligands at the freshwater-seawater interface (FSI; at 14 psu) promoted and below the FSI (at 20 psu) decreased the adsorption of Cd²⁺. The experiments were performed at metal concentrations of 8 × 10⁻⁸ mol l⁻¹ and at natural pH values around pH 8. Adsorbed amounts of trace metal ions were determined in filtered samples by differential pulse anodic stripping voltammetry (DPASV) with a three-electrode system, after 24 h of equilibration with calcite. Several adsorption models were tested, such as Freundlich's, Langmuir's and Schindler-Stumm's surface coordination model. Adsorption isotherms belong to S-1 class of empirical adsorption isotherms. None gave reasonable values of adsorption constants. The fractional partitioning of adsorbent to the solid phase when normalized to the quantity of adsorbent present (K_d) declined as solid concentration increased. It was found that the surface charge is not responsible for the observed effect. Instead, aggregate size increased, which effected a loss in surface area. This is a reasonable explanation for the observed S-shaped adsorption isotherms curves.     

Thermal annealing induced photocarrier radiometry enhancement for ion implanted silicon wafers

An experimental study on the photocarrier radiometry signals of As⁺ ion implanted silicon wafers before and after rapid thermal annealing is performed. The dependences of photocarrier radiometry amplitude on ion implantation dose (1×10¹¹--1×10¹⁶/cm²), implantation energy (20--140 keV) and subsequent isochronical annealing temperature (500--1100 du are investigated. The results show that photocarrier radiometry signals are greatly enhanced for implanted samples annealed at high temperature, especially for those with a high implantation dose. The reduced surface recombination rate resulting from a high built-in electric field generated by annealing-activated impurities in the pn junction is believed to be responsible for the photocarrier radiometry signal enhancement. Photocarrier radiometry is contactless and can therefore be used as an effective in-line tool for the thermal annealing process monitoring of the ion-implanted wafers in semiconductor industries.     

样品温度对CF+3 与Si表面相互作用影响的分子动力学模拟

利用分子动力学模拟方法研究了不同温度下CF_x层对CF⁺₃刻蚀Si表面过程的影响.由模拟数据可知,温度对C和F的沉积有显著的影响;通过提高样品的温度,物理刻蚀得到了加强,而化学刻蚀被减弱.同时,随着温度的升高,Si的刻蚀率相应增加.刻蚀产物中的SiF,SiF₂的量随温度的增加而增加,SiF₃的量与基体温度没有直接的关系.Si刻蚀率的增加主要是通过提高SiF,SiF_{2相似文献}   

铜离子对海参精氨酸激酶活力与结构的影响

精氨酸激酶(Arginine kinase,EC2.7.3.3)是无脊椎动物能量代谢所必需的重要的酶.海参精氨酸激酶是一种特殊的双亚基精氨酸激酶.本文研究了在二价铜离子作用下,海参精氨酸激酶催化活性与结构的变化.结果表明,一定浓度的铜离子,可以抑制精氨酸激酶的活力,并引起酶二级结构与三级结构的变化,引起疏水面暴露,并导...     

Selective depressions of surface silicic acid within cyclonic mesoscale eddies in the oligotrophic western North Pacific

To reveal spatial dynamics of silicic acid [Si(OH)₄] in the poorly sampled oligotrophic western North Pacific, we investigated the surface distribution of Si(OH)₄ and associated biogeochemical parameters by using an underway survey system with a highly sensitive nutrient analyzer along the 138°E transect (between 30 and 34°N) and the 155°E transect (between 10 and 35°N) during the summers of 2007 and 2008. Surface Si(OH)₄ concentrations ranged from the detection limit (11 nmol L⁻¹) to 2462 nmol L⁻¹. High Si(OH)₄ concentrations (>1000 nmol L⁻¹) and dynamic fluctuations were generally observed north of 23°N, while consistently stable low concentrations of 415–751 nmol L⁻¹ were observed south of 23°N. Surface nitrate+nitrite (N+N) and phosphate (PO₄³⁻) were typically depleted to <20 nmol L⁻¹, except for PO₄³⁻ in the area south of 16°N. The majority of the study area was characterized by high-Si(OH)₄ and low-N+N and PO₄³⁻. However, submesoscale/mesoscale depressions of Si(OH)₄ were locally observed in the cyclonic eddy fields north of 23°N. Among a total of six Si(OH)₄ depressions within the eddies, a complete Si(OH)₄ depletion (<11 nmol L⁻¹) was observed on the cyclonic side near the Kuroshio axis (33.1°N, 138°E). This depletion was closely coupled with a diatom bloom, suggesting that Si(OH)₄ was exhausted by diatoms. All of the Si(OH)₄ depressions were selective and not accompanied by local depressions of N+N and PO₄³⁻. This unique phenomenon might be driven by biogeochemical processes such as selective Si export (Si pump), anomalous Si uptake associated with diatom physiology, and/or Si uptake supported by N₂ fixation.     

Isotopic constraints on the Si-biogeochemical cycle of the Antarctic Zone in the Kerguelen area (KEOPS)

Estimation of the silicon (Si) mass balance in the ocean from direct measurements (Si uptake-dissolution rates …) is plagued by the strong temporal and spatial variability of the surface ocean as well as methodological artifacts. Tracers with different sensitivities toward physical and biological processes would be of great complementary use. Silicon isotopic composition is a promising proxy to improve constraints on the Si-biogeochemical cycle, since it integrates over longer timescales in comparison with direct measurements and since the isotopic balance allows to resolve the processes involved, i.e. uptake, dissolution, mixing. Si-isotopic signatures of seawater Si(OH)₄ and biogenic silica (bSiO₂) were investigated in late summer 2005 during the KEOPS experiment, focusing on two contrasting biogeochemical areas in the Antarctic Zone: a natural iron-fertilized area above the Kerguelen Plateau (< 500 m water depth) and the High Nutrient Low Chlorophyll area (HNLC) east of the plateau (> 1000 m water depth). For the HNLC area the Si-isotopic constraint identified Upper Circumpolar Deep Water as being the ultimate Si-source. The latter supplies summer mixed layer with 4.0 ± 0.7 mol Si m^? 2 yr^? 1. This supply must be equivalent to the net annual bSiO₂ production and exceeds the seasonal depletion as estimated from a simple mixed layer mass balance (2.5 ± 0.2 mol Si m^? 2 yr^? 1). This discrepancy reveals that some 1.5 ± 0.7 mol Si m^? 2 yr^? 1 must be supplied to the mixed layer during the stratification period. For the fertilized plateau bloom area, a low apparent mixed layer isotopic fractionation value (?³⁰Si) probably reflects (1) a significant impact of bSiO₂ dissolution, enriching the bSiO₂ pool in heavy isotope; and/or (2) a high Si uptake over supply ratio in mixed layer at the beginning of the bloom, following an initial closed system operating mode, which, however, becomes supplied toward the end of the bloom (low Si uptake over supply ratio) with isotopically light Si(OH)₄ from below when the surface Si(OH)₄ pool is significantly depleted. We estimated a net integrated bSiO₂ production of 10.5 ± 1.4 mol Si m^? 2 yr^? 1 in the AASW above the plateau, which includes a significant contribution of bSiO₂ production below the euphotic layer. However, advection which could be significant for this area has not been taken into account in the latter estimation based on a 1D approach of the plateau system. Finally, combining the KEOPS Si-isotopic data with those from previous studies, we refined the average Si-isotopic fractionation factor to ? 1.2 ± 0.2‰ for the Antarctic Circumpolar Current.     

The effect of a tidal cycle on the dynamics of nutrients in a tidal estuary in the Seto Inland Sea, Japan

A 24 hour time series survey was carried out during a spring tide (tidal range ca.2 m) of May 1995 on a tidal estuary in the Seto Inland Sea, Japan, in the context of an integrated program planned to quantify the dynamics of biophilic elements (carbon, nitrogen and phosphorus) and the roles played by the macrobenthos on the processes. Three stations were set along a transect line of about 1.4 km, which linked the river to the rear to the innermost part of the subtidal zone. Every hour, at each station, measurements were made of surface water temperature, salinity and dissolved oxygen concentration, and surface water was collected for the determination of nutrients [NH₄ ⁺−N, (NO₃ ⁻+NO₂ ⁻)−N, PO₄ ³⁻−P and Si (OH)₄−Si]. During the ebb flow, riverine input of silicate and nitrate+nitrite significantly increased the concentrations of both the intertidal and the subtidal stations. Conversely, during the high tide, river nutrient concentrations were lowered by the mixing of fresh water with sea water. As a result, best (inverse) correlations were found at the river station for salinity against silicate (y=-2.9 Sal.+110.7,r ²=0.879) and nitrate+nitrite (y=-1.3 Sal.+48.4,r ²=0.796). In contrast, ammonium nitrogen concentrations were higher at intermediate salinities. Indeed, no significant correlation was found between salinity and ammonium. The effect of the macrobenthos, which is abundant on the intertidal flat, is discussed as a biological component that influences the processes of nutrient regeneration within the estuary. The effect of the tidal amplitude is an important one in determining the extent of the variations in nutrient concentrations at all three stations, which were stronger between the lower low tide and the higher high tide.     

Equilibrium and structural studies of silicon(IV) and aluminium(III) in aqueous solution. II. Formation constants for the monosilicate ions SiO(OH)3 and SiO2(OH)2. A precision study at 25°C in a simplified seawater medium

The hydrolysis of silicic acid, Si(OH)₄, was studied in a simplified seawater medium (0.6 M Na(Cl)) at 25°C. The measurements were performed as potentiometric titrations (hydrogen electrode) in which OH⁻ was generated coulometrically. The total concentration of Si(OH)₄, B, and log[H⁺] were varied within the limits 0.00075 B 0.008 M and 2.5 -log[H⁺] 11.7, respectively. Within these ranges the formation of SiO(OH)₃⁻ and SiO₂(OH)₂²⁻ with formation constants log β₋₁₁(Si(OH)₄ SiO(OH)₃⁻ + H⁺) = −9.472 ±0.002 and log β₋₂₁(Si(OH)₄ SiO₂(OH)₂²⁻ + 2H⁺) = −22.07 ± 0.01 was established. With B > 0.003 M polysilicate complexes are formed, however, with -log[H⁺] 10.7 their formation does not significantly affect the evaluated formation constants. Data were analyzed with the least squares computer program LETAGROPVRID.     

Equilibrium and structural studies of silicon(IV) and aluminium(III) in aqueous solution. II. Formation constants for the monosilicate ions SiO(OH)3− and SiO2(OH)22−. A precision study at 25°C in a simplified seawater medium

The hydrolysis of silicic acid, Si(OH)₄, was studied in a simplified seawater medium (0.6 M Na(Cl)) at 25°C. The measurements were performed as potentiometric titrations (hydrogen electrode) in which OH^? was generated coulometrically. The total concentration of Si(OH)₄, B, and log[H⁺] were varied within the limits 0.00075 ? B ? 0.008 M and 2.5 ? -log[H⁺] ? 11.7, respectively. Within these ranges the formation of SiO(OH)₃^? and SiO₂(OH)₂^2? with formation constants log β_?11(Si(OH)₄ ? SiO(OH)₃^? + H⁺) = ?9.472 ±0.002 and log β_?21(Si(OH)₄ ? SiO₂(OH)₂^2? + 2H⁺) = ?22.07 ± 0.01 was established. With B > 0.003 M polysilicate complexes are formed, however, with $\text{-}\text{log[H}{}^{\mathrm{+}}\text{] ? 10.7}$ their formation does not significantly affect the evaluated formation constants. Data were analyzed with the least squares computer program LETAGROPVRID.     

The adsorption and interaction of long-chain fatty acids and heavy metals at the mercury electrode/sodium chloride solution interface

The reduction of heavy metals (cadmium, lead and zinc) in the presence of long-chain fatty acids (lauric, oleic and linoleic) in 0.55 mol dm^?3 NaCl and 0.03 mol dm^?3 NaHCO₃ at pH 8.7 has been studied by differential pulse polarography. The increase of the peak height of investigated metals by up to tenfold the value obtained in electrolyte without fatty acid is due to adsorption of metal ions at the electrode surface. The accumulation of metal increases with the increase of adsorption time (at potentials more positive than the reduction potential of the particular metal) and with increase of salinity. The heavy-metal adsorption depends on the concentrations of both metal ions and fatty acids. The interaction of heavy metals with the unsaturated fatty acids in the bulk and/or in the adsorbed layer at different natural interfaces could be of considerable importance in an understanding of the fate and distribution of heavy metals in the natural aquatic environment.     

Distribution of some ions and minor gaseous components by concentrations in the atmospheric surface layer of some regions in Eastern Siberia and the Far East

We consider the resemblance between the ion composition of the fraction of soluble aerosols and gaseous admixtures in the atmospheric surface layer at the high-level Mondy station (East Sayan), those in the Listvyanka settlement south of Lake Baikal, in the city of Irkutsk, and at the Primorskaya station near the city of Ussuriysk (Primorskii krai). We use measurement data on the concentrations of the following ions: HCO ₃ ^? , SO ₄ ^2? , NO ₃ ^? , Cl^?, H⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺ in the soluble fraction of aerosols and gases HNO₃, HCl, NH₃, and SO₂ in air samples over a 10-year period conducted in the mode of online monitoring. We found the lognormal form of distributions of concentrations of each of the abovementioned components according to the number of samples. A versatile scheme of the distribution of mean geometric concentrations of atmospheric components was proposed for all four groups.     

Effect of solid to solution ratio on biogenic silica determination in coastal sediments

The method of DeMaster (1981) for measuring biogenic silica (BSi) in marine sediments was modified. We found a considerable effect of the solid to solution (S/S) ratio on BSi determination in coastal sediments. The BSi contents determined by DeMaster’s method were overestimated due to the contribution of clay mineral-derived extractable Si at a low S/S ratio (<1 g l⁻¹), and incomplete recovery of BSi was observed due to incomplete extraction when using a high S/S ratio (>2 g l⁻¹). For BSi analysis of coastal sediment samples, the BSi content of representative samples must be measured using various S/S ratios to determine the appropriate S/S ratio in order to minimize the contribution of extractable Si derived from clay minerals and to obtain sufficiently efficient extraction with 1% Na₂CO₃ before actual sample measurement. One way to determine the appropriate S/S ratio is to use artificial sediment which has a theoretical Si and clay mineral content similar to the sediment sample composition. Using artificial sediment, the S/S ratio of 2 g l⁻¹ seems appropriate for measuring the BSi content of the coastal sediments investigated in this study, because 99.6% recovery can be achieved.     

Dissolved nutrient fluxes from the nearshore sediments of Bowling Green Bay,central Great Barrier Reef Lagoon (Australia)

The fluxes of dissolved inorganic N, P, and Si from the nearshore sediments of the Great Barrier Reef Lagoon are significantly lower than those reported from sediments in temperate regions at similar temperatures. The directly measured fluxes range from −23 to +28, −154 to +890, and −990 to +1750 μmol m⁻² day⁻¹ for PO₄³⁻, ΣN(=NH₄⁺ + NO₂⁻ + NO₃⁻) and Si, respectively. Estimates suggest that sediments are the major source of dissolved N to near-shore waters of the Lagoon greatly exceeding the dissolved flux from rivers. Resuspension of up to 1 cm of sediment during storms would have a very small effect on the PO₄³⁻ or Si(OH)₄ concentration of the overlying water, but would significantly raise the ΣN concentration. The productivity of these waters may be controlled at various times by the balance between the steady-state sedimentary flux of nutrients, the fluvial input, and storm resuspension.     

长江口及邻近海区营养盐结构与限制

通过研究长江口及邻近海域溶解无机氮(DIN=NO₃-+NO₂-+NH₄+)、磷酸盐(PO₄3-)、硅酸盐(SiO₃2-)所表征的营养盐区域结构特征及影响因素,在分析营养盐绝对限制情况的基础上,划分了潜在相对营养限制区域。结果表明,123°E以西近岸表层区域DIN/P比值全年均高于16,而Si/DIN除秋季外基本小于1,显示出长江冲淡水影响下"过量氮"的特征。春夏季河口锋面区(31°~32.5°N,122.5°~124°E)硅藻的大量生长可使DIN/P异常升高和Si/DIN异常降低。秋季研究区域北部DIN/P西低东高且Si/DIN西高东低是由于在高DIN、低PO₄3-的长江冲淡水影响下,近岸受相对低DIN、高SiO₃2-的苏北沿岸流南下入侵影响而被分割而成。冬季长江口门东北部存在的高DIN/P和低Si/DIN区则主要由于寡营养盐的黑潮水深入陆架,向东北输送的部分长江冲淡水和增强的苏北沿岸流共同作用造成DIN升高所致。利用Redfield比值进行了不同站位表层潜在相对营养限制情况的区分。近岸123°E以西受高DIN、SiO₃2-长江冲淡水影响,四季多呈现PO₄3-潜在相对限制,而在春夏季由于浮游植物的大量吸收PO₄3-,造成局部PO₄3-绝对限制及潜在相对限制。春夏季氮限(DIN潜在相对限制)一般发生在外海部分站位,但较为零散。秋季除了东南外海大部分站位外,受苏北沿岸流影响在长江口北部近岸也存在氮限。随着低DIN/P的黑潮表层水(KSW)的入侵加强,冬季外海氮限站位增多。硅限(SiO₃2-潜在相对限制)在夏季发生在赤潮高发区,而冬季南部存在较多硅限站位表明KSW中SiO₃2-相对较为缺乏。     

Annual Variation of Benthic Nutrient Fluxes in Shallow Coastal Waters (Gulf of Trieste, Northern Adriatic Sea)

Abstract. Benthic fluxes of dissolved N. Si and P nutrients, alkalinity, dissolved inorganic C (DIC), and O₂ from sediments in the Gulf of Trieste (northern Adriatic, Italy) were measured monthly for 16 months, using laboratory incubated flux chambers at in siru temperatures in the dark. The annual average fluxes were: 02 = -19.3 ± 8.2, DIC = 13.7 ± 9.6, NO3 = -0.04 ± 0.16, NH4 = 0.3 ± 0.4. PO₄= 4.001 ± 0.01, Si = 0.9 ± 0.1 mmol m-² d^-1, with strong temporal fluctuations. The highest effluxes of all nutrients and DIC were observed in the summer. Small effluxes of DIC and NH4 and influxes of Si and PO4 were observed in late winter. Only NH₄ (ca. 50%) and Si (ca. 70%) fluxes were significantly correlated with temperature. This correlation suggests that the rate of downward input and the quality of sedimented organic matter (autochthonous and allochthonous) were superimposed on the temperature fluctuations. High DIC, NH₄ and Si effluxes observed in May 1993 during low temperature were due to the degradation of sedimentary organic matter produced by an early spring bloom of benthic microalgae which occurred about 6 weeks earlies while the autumn phytoplankton bloom was simultaneously reflected in enhanced benthic fluxes due to higher temperature. The role of benthic biological advection in this transport across the sediment-water interface, evaluated by comparison between measured benthic and calculated diffusive fluxes from nutrient pore water concentrations, was of minor importance. This is probably due to low infaunal activity throughout the year it was localized mostly in the narrow surficial layer. The annual average diffusive fluxes of NH4 and PO4 were higher than those measured, probably due to the presence of nitrificationdenitrifi-cation processes and redox-dependent chemical reactions at the oxic sediment-water interface, respectively. Only during bottom-water hypoxia in September 1993 did strong PO₄ effluxes prevail. Calculations based on the Redfield stoichiometry of oxic decomposition of organic N to NH4 and NO3, and differences between diffusive and measured NH₄ fluxes showed that denitrifkation averaged 0.8 mmol m^-2 d^-1. Significant correlations between NH₄ and PO₄ DIC and Si, and NH4 and Si fluxes suggested their parallel regeneration and utilization at the sediment-water interface. The nutrient fluxes observed were not significantly linked to O₂ consumption, suggesting also that anaerobic oxidation processes were important at the sediment-water interface in the gulf. The N, P and Si nutriqnts released from sediment pore waters are probably utilized in benthic microalgal and bottorn-hater primary production. This indicates that pelagic and benthic communities in the central part of the Gulf of Trieste function relatively independently of each other.     

纳米TiO2 对海洋生源要素含量及威氏海链藻生长的影响

探讨不同质量浓度纳米TiO2(0,4,8,12,16,20 mg/L)对海洋生源要素(N,P,Si,Fe)含量及威氏海链藻(Thalassiosira weissflogii)生长的影响。实验结果表明:随纳米二氧化钛浓度增大,对海洋生源要素的吸附率有不同程度的提高,海洋生源要素含量下降,对磷和铁的影响最为明显;纳米二氧化钛吸附对氮磷比和硅磷比影响很大,氮磷比为68~126,硅磷比为74~135,而对硅氮比影响很小基本维持在1。纳米二氧化钛对威氏海链藻生长有明显抑制,并存在剂量—效应关系,与海洋生源要素含量影响存在相关性。     

A nitrate and silicate budget in the equatorial Pacific Ocean: a coupled physical–biological model study

A coupled physical–biological model was developed to simulate the low-silicate, high-nitrate, and low-chlorophyll (LSHNLC) conditions in the equatorial Pacific Ocean and used to compute a detailed budget in the Wyrtki box (5°N–5°S, 180–90°W) for the major sources and cycling of nitrogen and silicon in the equatorial Pacific. With the incorporation of biogenic silicon dissolution, NH₄ regeneration from organic nitrogen and nitrification of ammonia in the model, we show that silicon recycling in the upper ocean is less efficient than nitrogen. As the major source of nutrients to the equatorial Pacific, the Equatorial Undercurrent provides slightly less Si(OH)₄ than NO₃ to the upwelling zone, which is defined as 2.5°N–2.5°S. As a result, the equatorial upwelling supplies less Si(OH)₄ than NO₃ into the euphotic zone in the Wyrtki box, having a Si/N supply ratio of about 0.85 (2.5 vs. 2.96 mmolm⁻² day⁻¹). More Si(OH)₄ than NO₃ is taken up with a Si/N ratio of 1.17 (2.72 vs. 2.33 mmolm⁻² day⁻¹) within the euphotic zone. The difference between upwelling supply and biological uptake is balanced by nutrient regeneration and horizontal advection. Excluding regeneration, the net silicate and nitrate uptakes are nearly equal (1.76 vs. 1.84 mmolm⁻² day⁻¹). However, biogenic silica export production is slightly higher than organic nitrogen (1.74 vs. 1.59 mmolm⁻² day⁻¹) following a 1.1 Si/N ratio. In the central equatorial Pacific, low silicate concentrations limit diatom growth; therefore non-diatom new production accounts for most of the new production. Higher silicate supply in the east maintains elevated diatom growth rates and new production associated with diatoms dominate upwelling zone. In contrast, the new production associated with small phytoplankton is nearly constant or decreases eastward along the equator. The total new production has a higher rate in the east than in the west, following the pattern of surface silicate. This suggests that silicate regulates the diatom production, total new production, and thereby carbon cycle in this area. The modeled mean primary production is 48.4 mmolCm⁻² day⁻¹, representing the lower end of direct field measurements, while new production is 15.0 mmolCm⁻² day⁻¹, which compares well with previous estimates.     

基于河口潮间带底栖微藻群落水平的环境质量状态评价

The feasibility of community-based bioassessment of environmental quality status was studied using microphytobenthos(MPB) in estuarine intertidal ecosystems.The sediment samples of MPB were collected monthly during a 1-year cycle(September 2006–August 2007) at four sampling stations in the Nakdong River Estuary,Korea.Environmental variables,such as salinity,radiation,grain size of sediment,Si(OH)_4(Si),nitrate(NO_3~–),nitrite(NO_2~–),ammonium(NH_4~+) and phosphates(PO_4~(3–)),were measured synchronously for comparison with biotic parameters.The statistical analyses were carried out for assessment the relationship between biotic and environmental parameters.The results showed that:(1) the MPB community structures were significant differences among four sampling stations;(2) spatial variation in the MPB communities were significantly correlated with environmental variables,especially the nutrient NH_4+ in combination with salinity and grain size;(3) three species(Navicula lacustris,Pleurosigma anglulatum and Fragilaria sp.1) were significantly correlated with nutrients and/or Si;and(4) the species richness and diversity were significantly correlated with the grain size.It is suggested that MPB communities may be used as a potentially robust bioindicator for assessing environmental quality status in estuarine intertidal ecosystems.     

Organic and inorganic speciation of copper in the Irish Sea

The metal complexing ability of surface water of the Irish Sea has been measured by the MnO₂ adsorption method. In all samples strong copper-chelating compounds are present at concentrations of 60–150 nM, with conditional stability constants (log values) of 10.0–10.4. The concentrations of Cu, Pb and Cd in the samples are 16–39 nM, 1–7 nM and 0.1–2 nM, respectively; much less than the ligand concentrations. The organic compounds form complexes with 94–98% of dissolved copper, and therefore constitute the major form of copper in surface water of the Irish Sea. Recalculation of speciation of the inorganic fraction of copper in seawater reveals that the major complex ion is that of CuCO₃⁰ (60%), followed by CuOH⁺ (16%) and Cu(OH)₂⁰ (16%). Complexes with borate ions form a small and rather insignificant fraction of 1%.