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1.
为探讨单一因素(如浓度、温度、酸碱度)对冰封期乌梁素海中营养盐和盐分(总氮、总磷、Na+和Cl-)迁移的影响,对不同条件下各物质水样进行室内单向结冰模拟,分析总结物质在冰层和冰下水层中的分布特征,并用分配系数(K)来表征.结果表明:冰体中物质浓度随水样初始浓度(C0)的增大而增大,随结冰温度的升高而减小;各物质在冰体中的浓度分布表现为顶层中层底层.总氮、总磷的分配系数K随C0的增大呈递减趋势,Na+和Cl-的K值随C0的增大呈递增趋势;对各条件下的K值进行假设检验,结果为:水样中物质初始浓度和结冰温度显著影响其在冰-水体系中的分布;同一温度下,C0较小时,酸碱度显著影响各物质在冰-水体系中的分布,C0较大时,酸碱度显著影响Na+和Cl-在冰-水体系中的分布,但对总氮、总磷浓度分布的影响不显著.可见,在不同环境因素下,各物质在冰-水体系中表现出不同的分布特征,对此进行模拟可为寒区湖泊污染物迁移和生物地球化学循环的研究提供一定的参考.  相似文献   

2.
Analyses (n = 525) of chloride (Cl−), bromide (Br−), nitrate as nitrogen (NO3-N), sodium (Na+), calcium (Ca2+) and potassium (K+) in stream water, tile-drain water and groundwater were conducted in an urban-agricultural watershed (10% urban/impervious, 87% agriculture) to explore potential differences in the signature of Cl− originating from an urban source as compared with an agricultural source. Only during winter recharge events did measured Cl− concentrations exceed the 230 mg/L chronic threshold. At base flow, nearly all surface water and tile water samples had Cl− concentrations above the calculated background threshold of 18 mg/L. Mann–Whitney U tests revealed ratios of Cl− to Br− (p = .045), to NO3-N (p < .0001), to Ca2+ (p < .0001), and to Na+ (p < .0001) to be significantly different between urban and agricultural waters. While Cl− ratios indicate that road salt was the dominant source of Cl− in the watershed, potassium chloride fertilizer contributed as an important secondary source. Deicing in watersheds where urban land use is minimal had a profound impact on Cl− dynamics; however, agricultural practices contributed Cl− year-round, elevating stream base flow Cl− concentrations above the background level.  相似文献   

3.
盐分是参与湖泊物质循环的重要成分之一，湖泊盐度增加对湖泊生态系统健康造成了严重的威胁.乌梁素海总溶解性固体（TDS）和盐度均处于较高的水平，为揭示盐分在冰-水-沉积物中的分布及迁移规律，冰封期在乌梁素海7个采样点采集冰、冰下水和不同深度沉积物样品，分析样品的TDS、Na+和Cl-浓度，得到各自在冰-水间浓度的比值，即分配系数K，并对水-沉积物界面Na+和Cl-的扩散通量进行估算.结果显示，TDS、Na+和Cl-在冰-水中分配系数K的均值分别为0.02、0.03和0.01，表明在湖水结冰形成冰盖的过程中，随着冰晶的析出，TDS、Na+和Cl-逐渐在水体中浓缩，水体中Na+和Cl-在浓度梯度驱动力作用下，向沉积物间隙水中扩散，估算其扩散通量均值分别为-229和-676 mg/（m2·d）.总之，湖水在冻结过程中，由于冰晶的析出，盐分向冰下水体中迁移，使得盐分浓度在冰下水体中浓缩增加，继而向沉积物中迁移，对湖泊水生态环境构成胁迫.  相似文献   

4.
Lithological and hydrological influence on fluvial physical and chemical erosion was studied in a glacierized sedimentary basin with high evaporite presence. Suspended particulate matter (SPM), total dissolved solids (TDS) and major ion concentrations were analysed for 2 years of different hydrologic condition: (i) 2009–2010, Q = 100% average; and (ii) 2010–2011, Q = 60% average. Annual hydrograph was simple regime‐type with one peak in summer related to snow melting. The intra‐annual SPM and TDS variations were directly and inversely associated to Q, respectively. Snow chemistry showed continental influence (Na+/Ca2+ = 0.17), and atmospheric input of TDS was <1% of the total exported flux. River water was highly concentrated in Ca2+ and SO42− (~4 mmol l−1) and in Na+ and Cl− (~3 mmol l−1). Ca2+/SO42− and Na+/Cl− molar ratios were ~1 and related to Q, directly and inversely, respectively. Major ion relationships suggest that river chemistry is controlled by evaporite (gypsum and halite) dissolution having a summer input from sulfide oxidation and carbonate dissolution, and a winter input from subsurface flow loaded with silicate weathering products. This variation pattern resulted in nearly chemostatic behaviour for Ca+, Mg2+ and SO42−, whereas Na+, Cl− and SiO2 concentrations showed to be controlled by dilution/concentration processes. During the 2009–2010 hydrological year, the fluxes of water, SPM and TDS registered in the snow melting–high Q season were, respectively, 71%, 92% and 67% of the annual total, whereas for equal period in 2010–2011, 56% of water, 86% of SPM and 54% of TDS annual fluxes were registered. The SPM fluxes for 2009–2010 and 2010–2011 were 1.19 × 106 and 0.79 × 106 t year−1, whereas TDS fluxes were 0.68 × 106 and 0.55 × 106 t year−1, respectively. Export rates for 2009–2010 were 484 t km2 year−1 for SPM and 275 t km2 year−1 for TDS. These rates are higher than those observed in glacierized granite basins and in non‐glacierized evaporite basins, suggesting a synergistic effect of lithology and glaciers on physical and chemical erosion. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

5.
Soil salinity and waterlogging are two major environmental problems in estuarine wetlands. The objective of this study was to investigate the effects of salt stress, water table, and their combination on growth, chlorophyll content, antioxidant system, and ion accumulation in Suaeda salsa plant, which is the pioneer plant in coastal wetland of the Yellow River Delta (YRD). The results showed that plant height, number of branches, and biomass were significantly affected by water table and salt stress. With enhanced salt stress, the ratio of leaf to total biomass increased and the ratio of root to total biomass decreased. The contents of Chl‐a, ‐b, Chl‐a + b, and carotenoids (Car) decreased significantly with increasing soil salinity and the water table level. Salt stress enhanced the activity of superoxide dismutase (SOD) and catalase (CAT), but reduced the content of protein. With the lowering water table level, the activity of CAT and protein content increased, and activity of SOD decreased. Na+ and Cl? content were up‐regulated with increasing salt stress (NaCl), whereas, the contents of other cations (K+, Ca2+, and Mg2+) and anions ( and ) were decreased. In summary, the results indicated that the S. salsa plants could adapt to the adverse soil environments through modifying their growth and physiology status at the highly saline and intertidal zone, such as the YRD estuarine wetlands, and also could be used as a bio‐reclamation plant to decline the high salt in saline soils.  相似文献   

6.
Chloride (Cl−) in urban waterways largely originates from runoff containing deicing salts. Cl− is retained in watersheds after deicing ends, resulting in deleterious effects on aquatic biota. Stormwater management ponds (SWMPs), designed to mitigate ‘flashy’ urban runoff response, are known to impact pollutant transport. However, there is little information on what role SWMPs play in the timing and magnitude of Cl− transport over different timescales. This study quantifies the mass of Cl− retained in two SWMPs over varying timescales. Both ponds are in an urbanizing watershed in south-central Ontario; one drains a commercial area, the other, a residential area. High frequency measurements of water level and specific conductivity, from which flow and Cl− concentration were derived, were taken with sensors at pond inlets and outlets. For one SWMP, data were also collected upstream and downstream of the confluence of the pond outflow and the receiving creek to quantify the in-stream response to Cl−-laden pond outflows. The findings suggest that SWMPs likely play a role in watershed-scale Cl− retention; one SWMP consistently retained Cl− while the other had variable retention and release of Cl−. In the receiving creek, Cl− concentrations downstream of the pond exceeded the acute toxicity threshold for aquatic organisms twice as often as concentrations upstream of the pond, and Cl− pulses corresponded to Cl− release events from the pond. The results of this study suggest that SWMPs concentrate spatially distributed salt inputs and modify the timing and magnitude of their release to receiving streams. Stream reaches that receive water inputs from SWMPs may be more vulnerable to Cl− toxicity than reaches that do not receive flow via SWMPs. The results of this study will help parameterize the role of SWMPs in watershed-scale Cl− transport models and geospatial models of salt vulnerable areas.  相似文献   

7.
Salinity and periodic inundation are both known to have a major role in shaping the ecohydrology of mangroves through their controls on water uptake, photosynthesis, stomatal conductance, gas exchanges, and nutrient availability. Salinity, in particular, can be considered one of the main abiotic regulating factors for halophytes and salt‐tolerant species, due to its influence on water use patterns and growth rate. Ecohydrological literature has rarely focused on the effects of salinity on plant transpiration, based on the fact that the terrestrial plants mostly thrive in low‐saline, unsaturated soils where the role of osmotic potential can be considered negligible. However, the effect of salinity cannot be neglected in the case of tidal species like mangroves, which have to cope with hyperosmotic conditions and waterlogging. We introduce here a first‐order ecohydrological model of the soil/plant‐atmosphere continuum of Avicennia marina—also known as gray mangrove—a highly salt‐tolerant pioneer species able to adapt to hyperarid intertidal zones and characterized by unique morphological and ecophysiological traits. The A. marina's soil‐plant‐atmosphere continuum takes explicitly into account the role of water head, osmotic water potential, and water salinity in governing plant water fluxes. A. marina's transpiration is thus modeled as a function of salinity based on a simple parameterization of salt exclusion mechanisms at the root level and a modified Jarvis' expression accounting for the effects of salinity on stomatal conductance. Consistently with previous studies investigating the physiology of mangroves in response to different environmental drivers, our results highlight the major influence of salinity on mangrove transpiration when contrasted with other potential stressors such as waterlogging and water stress.  相似文献   

8.
Thermal springs of the Boundary Creek hydrothermal system in the southwestern part of Yellowstone Park outside the caldera boundary vary in chemical and isotopic composition, and temperature. The diversity may be accounted for by a combination of processes including boiling of a deep thermal water, mixing of the deep thermal water with cool meteoric water and/or with condensed steam or steam-heated meteoric water, and chemical reactions with surrounding rocks. Dissolved-silica, Na+, K+ and Ca2+ contents of the thermal springs could result from a thermal fluid with a temperature of 200 ± 20°C. Chloride-enthalpy and silica-enthalpy mixing models suggest mixing of 230°C, 220 mg/l Cl− thermal water with cool, low-Cl− components. A 350 to 390°C component with Cl− ≥ 300 mg/l is possibly present in thermal springs inside the caldera but is not required to fit observed spring chemical and isotopic compositions. Irreversible mass transfer models in which a low-temperature water reacts with volcanic glass as it percolates downward and warms, can account for observed pH and dissolved-silica, K+, Na+, Ca2+ and Mg2+ concentrations, but produces insufficient Cl− or F− for measured concentrations in the warm springs. The ratio of aNa/aH, and Cl− are best accounted for in mixing models. The water-rock interaction model fits compositions of acid-sulfate waters observed at Summit Lake and of low-Cl− waters involved in mixing.The cold waters collected from southwestern Yellowstone Park have δD values ranging from −118 to −145 per mil and δ18O values of −15.9 to −19.4 per mil. Two samples from nearby Island Park have δD values of −112 and −114 per mil and δ18O values of −15.1 and −15.3 per mil. All samples of thermal water plot significantly to the right of the meteoric water line. The low Cl− and variable δD values of the thermal waters indicate isotopic compositions are derived by extensive dilution with cold meteoric water and by steam separation on ascent to the surface. Many of the hot springs with higher δD values may contain in addition a significant amount of high-D, low-Cl−, acid-sulfate or steam-heated meteoric water. Mixing models, Cl− content and isotopic compositions of thermal springs suggest that 30% or less of a deep thermal component is present. For example, the highest-temperature springs from Three Rivers, Silver Scarf and Upper Boundary Creek thermal areas contain up to 70% cool meteoric water and 30% hot water components, springs at Summit Lake and Middle Boundary Creek spring 57 are acid-sulfate or steam-heated meteoric water; springs 27 and 48 from Middle Boundary Creek and 49 from Mountain Ash contain in excess of 50% acid-sulfate water; and Three Rivers spring 46 and Phillips could result from mixing hot water with 55% cool meteoric water followed by mixing of acid-sulfate water. Extensive dilution by cool meteoric water increases the uncertainties in quantity and nature of the deep meteoric, thermal component.  相似文献   

9.
The relations between lake surface sediment diatoms and water environmental variables were revealed effectively by use of a new multivariate canonical correspondence analysis (CCA) based on 45 lakes in the Tibetan Plateau. Water depth, conductivity, Cl?, Mg2+, K+ and pH, identified from 12 contemporary water environmental variables, can significantly and independently explain the diatom distributions (p<0.05). The first two axes (λ1=0.34, λ2=0.27) capture 16.1% of the variance in the species data, and account for 57.4% of the variance in diatom-environment relationship. The deletion of redundant environmental variables and unusual samples do not influence the explanation to diatom data. The final CCA result indicates that the water depth and the salinity are the two important environmental gradients and influence the diatom distribution in the plateau lakes. The water depth correlates with axis 1, while conductivity, Cl?, Mg2+ and K+, indicating the direction of salinity changes, correlate with both of the first two axes. The definition of diatom-environment model may provide a basis for further quantitative inference on diatom-environment transfer function.  相似文献   

10.
Inorganic ions and nutrients were measured at different depths of the Xiangxi and Daninghe Rivers to explore the mixing processes of representative bays in the Three Gorges Reservoir (TGR). HCO3− and Ca2+ are the dominant ions. Carbonate weathering is the most important mechanism controlling the ion water chemistry; however, important differences exist between the main channel and its tributaries. Major ion levels in the TGR bays depend on hydrological mixing. Results show that the major ions of Ca2+, Mg2+, Na+, K+, Sr2+, SO42− and Cl− show chemically conservative behaviour during transit through the bays of the TGR. This means the ions can be used as tracers in the same way that salinity is used in estuaries to explore behaviour of other non‐conservative elements and to indicate specific source waters. In contrast, nutrients are not conserved in the mixing zone. The mixing of the main channel and tributaries and biological utilization in backwater reaches were the key factor controlling nutrient distributions in Xiangxi and Daninghe Bays. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

11.
土地利用结构与景观格局对鄱阳湖流域赣江水质的影响   总被引：4，自引：0，他引：4  
徐启渝  王鹏  王涛  舒旺  张华  齐述华 《湖泊科学》2020,32(4):1008-1019
于2015年1月和7月采集赣江干流及支流34个采样点水样,测定电导率、水化学离子、无机氮等水质指标.利用赣江流域2014年30 m分辨率的土地利用数据,以流域景观类型占比表征土地利用结构,景观指数表征景观格局;采用Pearson相关分析、Bioenv分析、Mantle检验与方差分解等方法分析流域土地利用结构与景观格局对赣江水质的影响.结果表明:上游Cl~-、Na~+浓度最高,中游电导率、Cl~-、Na~+、K~+、Ca~(2+)等水质指标最低,下游电导率、HCO_3~-、SO_4~(2-)、Mg~(2+)、Ca~(2+)、NO_3~--N等水质指标最高.居民建设用地是对水质影响最显著的单一土地利用类型.林地、水田与居民建设用地是对水质影响最显著的土地利用类型组合.平均最近邻体指数是对水质影响最显著的单一景观指数,斑块个数、斑块聚集度指数、平均最近邻体指数是对水质影响最显著的景观指数组合.枯水期土地利用结构和景观格局对水质的贡献率分别为41.1%和17.2%,景观格局对水质的贡献率(17.2%)均为和土地利用结构的交互作用,无独立贡献部分;丰水期二者对水质贡献率分别为51%、53%,交互作用部分为37%.以上结果表明,土地利用结构与景观格局都对赣江水质有较大影响,二者的交互作用在该影响中占有重要地位,且枯水期景观格局对水质的影响涵盖在与土地利用结构的交互作用中.  相似文献   

12.
The groundwater of the Korba plain represents major water resources in Tunisia. The Plio‐Quaternary unconfined aquifer of the Cap‐Bon (north‐east Tunisia) is subject to the intensive agricultural activities and high groundwater pumping rates due to the increasing of the groundwater extraction. The degradation of the groundwater quality is characterized by the salinization phenomena. Groundwater were sampled and analysed for physic‐chemical parameters: Ca2+, Mg2+, Na+, K+, Cl‐, SO42‐, HCO3‐, NO3‐, pH, electrical conductivity (EC), and the temperature (T°). The hydrochemical analysis is coupled with the calculation of the saturation indexes (SI gypsum, SI halite, SI calcite and SI dolomite), ionic derivation and with the ion correlations compared to chloride concentrations: Na+/ Cl‐, Ca2+/ Cl‐ and Mg2+/ Cl‐ ratios. Seawater fractions in the groundwater were calculated using the chloride concentration. Those processes can be used as indicators of seawater intrusion progression. EC methods were also conducted to obtain new informations on the spatial scales and dynamics of the fresh water–seawater interface of coastal groundwater exchange. The mixing zone between freshwater and saltwater was clearly observed from the EC profile in the investigated area where a strong increase in EC with depth was observed, corresponding to the freshwater and saltwater interface. Results of hydrochemical study revealed the presence of direct cation exchange linked to seawater intrusion and dissolution processes associated with cations exchange. These results, together with EC investigation, indicated that the groundwater is affected by seawater intrusion and is still major actor as a source of salinization of the groundwater in Korba coastal plain. Further isotopic and hydrological investigations will be necessary to identify and more understood the underlying mechanisms. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

13.
Concentrations of major ions in surface waters of the rivers of Khara-Murin and Snezhnaya are compared based on data of many-year observations carried out in the 1950s and 2000s. The concentrations of HCO 3 ? , Cl?, Ca2+, Mg2+, Na+ + K+ are shown to be stable. A considerable increase in SO 4 ?2 concentration was revealed.  相似文献   

14.
Chemical studies have been carried out on a number of water wells from the Dibdiba Formation northeast of Kuwait. Water salinity of this formation ranges between 3,300 mg/l to 7,000 mg/l, increasing with depth. The water entrapped in Dibdiba Formation is mainly sodium chloride type which can be differentiated into three different groups according to the ranges of concentration of the main cations and anions. These groups are: (3331113) sodium chloride water type in which Cl > Na, group (3333113) sodium chloride water type in which Na > Cl. In both groups the sequence of dominant cations is Na > Ca > Mg. Group (3333111) sodium chloride water type has Na > Cl and the sequence of dominant cations is Na > Mg > Ca. Chemical ratios of Ca/Mg, Na/Cl, and C1/HCO3 were worked out for Dibdiba ground water. The ratio of Ca/Mg Dibdiba Formation ranges from 0.4 to 8.58, the ratio of Na/Cl ranges between 0.98 to 1.33, and the ratio of C1/HCO3 is 232. A plot of chemical analysis on a trilinear diagram shows that Dibdiba Formation ground-water chemical properties are dominated by alkalies (Na > Ca) and strong acid (Cl > SO4). Water chemistry may reflect the history of the flow path, indicating regional flow as shown by increasing Na+, Cl-, SO–4 and where Ca+, Mg+ achieve equilibrium.  相似文献   

15.
Three techniques for obtaining soil water solutions (gravitational and matrical waters extracted using both in situ tension lysimeters and in vitro pressure chambers) and their later chemical analysis were performed in order to know the evolution of the soil‐solution composition when water moves down through the soil, from the Ah soil horizon to the BwC‐ or C‐horizons of forest soils located in western Spain. Additionally, ion concentrations and water volumes of input waters to soil (canopy washout) and exported waters (drainage solutions from C‐horizons) were determined to establish the net balance of solutes in order to determine the rates of leaching or retention of ions. A generalized process of sorption or retention of most components (even Cl?) was observed, from the soil surface to the C‐horizon, in both gravitational and matrical waters, with H4SiO4, Mn2+, Na+, and SO42? being the net exported components from the soil through the groundwater. These results enhance the role of the recycling effect in these forest soils. The net percentages of elements retained in these forest soils, considering the inputs and the outputs balance, were 68% K+, 85% Ca2+, 58% Mg2+, 7% Al3+, 5% Fe3+, 34% Zn2+, 57% Cl?, and 20% NO3?, and about 75% of dissolved organic carbon was mineralized. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

16.
To investigate the impacts of the invasion by bamboo on fluxes of nutrients and pollutants, the nutrient/pollutant fluxes and canopy interactions, including neutralization of acidity, leaching and uptake of nitrogen (N), were characterized in conjunction with rainfall partitioning in a Moso‐bamboo (Phyllostachys pubescens) forest. Measurements of precipitation volume, pH, major ions, and silicate (SiO2) in rainfall, throughfall and stemflow were collected weekly in a Moso‐bamboo forest located in Munakata City, Western Japan for 1 year. Results showed that rainfall partitioning into stemflow was larger than that for other types of forest, which may be due to the properties of Moso‐bamboo forest structure, such as a straight and smooth culm. Inorganic N (NO3− + NH4+) and S (SO42−) fluxes of throughfall and stemflow were approximately 1·6 and 1·3 times higher than that of rainfall, respectively. Contribution of stemflow flux to inorganic N and S fluxes to the forest floor was high. This could be due to lower uptake of inorganic N through culm and a higher rainfall partitioning into stemflow than that for other types of forest. The Moso‐bamboo canopy neutralized rainfall acidity, reducing the fluxes of potentially acidifying compounds via throughfall and stemflow. Canopy leaching of K+ was distinctly higher than that of Mg2+ and Ca2+ and could be related to the high mobility of K+ in plant tissues. Cl− and SiO2 were readily leached as for K+. The impact of the invasion by bamboo on nutrient cycling was discussed. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

17.
Xiaohu Wen  Meina Diao  De Wang  Meng Gao 《水文研究》2012,26(15):2322-2332
Groundwater salinization has become a crucial environmental problem worldwide and is considered the most widespread form of groundwater contamination in the coastal zone. In this study, a hydrochemical investigation was conducted in the eastern coastal shallow aquifer of Laizhou Bay to identify the hydrochemical characteristics and the salinity of groundwater using ionic ratios, deficit or excess of each ions, saturation indices and factor analysis. The results indicate that groundwater in the study area showed wide ranges and high standard deviations for most of hydrochemical parameters and can be classified into two hydrochemical facies, Ca2+‐Mg2+‐Cl‐ facies and Na+‐Cl‐ facies. The ionic ratio, deficit or excess of each ions and SI were applied to evaluate hydrochemical processes. The results obtained indicate that the salinization processes in the coastal zones were inverse cation exchange, dissolution of calcite and dolomite, and intensive agricultural practices. Factor analysis shows that three factors were determined (Factor 1: TDS, EC, Cl‐, Mg2+, Na+, K+, Ca2+ and SO42‐; Factor 2: HCO3‐ and pH; Factor 3: NO3‐ and pH), representing the signature of seawater intrusion in the coastal zone, weathering of water–soil/rock interaction, and nitrate contamination, respectively. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

18.
Dew samples were collected between October 2007 and February 2008 from a suburban site in Agra. pH, conductivity, major inorganic ions (F?, Cl?, NO 3 ? , SO 4 2? , Na+, K+, Ca2+, Mg2+, and NH 4 + ), and some trace metals (Cr, Sn, Zn, Pb, Cd, Ni, Mn, Fe, Si, Al, V, and Cu) were determined to study the chemistry of dew water. The mean pH was 7.3, and the samples exhibited high ionic concentrations. Dew chemistry suggested both natural and anthropogenic influences, with acidity being neutralized by atmospheric ammonia and soil constituents. Ion deposition flux varied from 0.25 to 3.0?neq?m?2?s?1, with maximum values for Ca2+ followed by NH 4 + , Mg2+, SO 4 2? , Cl?, NO 3 ? , Na+, K+, and F?. Concentrations of trace metals varied from 0.13 to 48?μg?l?1 with maximum concentrations of Si and minimum concentration of Cd. Correlation analysis suggested their contributions from both crustal and anthropogenic sources.  相似文献   

19.
The cherts formed from sodium silicate precursors in East African saline, alkaline lakes have δ18O values ranging from 31.1 to 44.1. The δ18O values correlate in general with lake salinities as inferred from geologic evidence, indicating that most chert was formed from its precursor in contact with lake water trapped at the time of deposition. A few of the analyzed cherts probably formed in contact with dilute meteoric water. From the widely varying δ18O values we conclude that precursors were transformed to chert in fluids of widely varying salinity and aNa+/aH+ ratio.  相似文献   

20.
An empirical model of Skeletonema costatum photosynthetic rate is developed and fit to measurements of photosynthesis selected from the literature. Because the model acknowledges existence of: 1) a light-temperature interaction (by allowing optimum irradiance to vary with temperature), 2) light inhibition, 3) temperature inhibition, and 4) a salinity effect, it accurately estimates photosynthetic rates measured over a wide range of temperature, light intensity, and salinity. Integration of predicted instantaneous rate of photosynthesis with time and depth yields daily net carbon assimilation (pg C cell?1 day?1) in a mixed layer of specified depth, when salinity, temperature, daily irradiance and extinction coefficient are known. The assumption of constant carbon quota (pg C cell?1) allows for prediction of mean specific growth rate (day?1), which can be used in numerical models of Skeletonema costatum population dynamics.Application of the model to northern San Francisco Bay clearly demonstrates the limitation of growth by low light availability, and suggests that large population densities of S. costatum observed during summer months are not the result of active growth in the central deep channels (where growth rates are consistently predicted to be negative). But predicted growth rates in the lateral shallows are positive during summer and fall, thus offering a testable hypothesis that shoals are the only sites of active population growth by S. costatum (and perhaps other neritic diatoms) in the northern reach of San Francisco Bay.  相似文献   

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