The ionization of acids in estuarine waters

The stoichiometric, $\text{K}{}_{\mathrm{HA}}{}^1$, and apparent, K'_HA, constants for the ionization of a number of weak acids (NH₄⁺, HSO₄^?, HF, H₂O, B(OH)₃, H₂CO₃, HCO₃^?, H₃PO₄, H₂PO₄^?, HPO₄², H₃AsO₄ H₂AsO₄^? and HAsO₄^2?) in seawater at 25°C diluted with water have been fitted to equations of the form (Millero, 1979). In $\text{K}{}_{\mathrm{HA}}{}^1\text{= In K}{}_{\mathrm{HA}}\text{+ AS}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{+ BS}$ where In K_HA is the thermodynamic constant in water, S is the salinity, A and B are adjustable parameters. The validity of this equation in estuarine waters has been examined by using an ion pairing model (Millero and Schreiber, 1981). The calculated values of $\text{K}{}_{\mathrm{HA}}{}^1$ and K'_HA at S = 35%. are in good agreement with the measured values for all the systems examined. The equation used to extrapolate the measured values to pure water K_HA predicted values that agreed with those determined by using the ion pairing model. The exception was the ionization of HPO₄^2? due to the strong interactions of Ca²⁺ and Mg²⁺ with PO₄^3?. The differences in the predicted values of $\text{K}{}_{\mathrm{HA}}{}^1$ in seawater diluted with pure water and average river water were very small for all the acids except HPO₄^2? (the maximum ΔpK = 0.96 in average river water). The larger difference in the $\text{K}{}_{\mathrm{HA}}{}^1$ for HPO₄^2? in river waters is due to the strong interactions of Ca²⁺ and PO₄^3?.     

Silver in San Francisco Bay estuarine waters

Spatial gradients of silver concentrations in the surface waters of San Francisco Bay reveal substantial anthropogenic perturbations of the biogeochemical cycle of the element throughout the estuarine system. The most pronounced perturbations are in the south bay, where dissolved (<0.45 μm) silver concentrations are as high as 250 pM. This is more than one order-of-magnitude above baseline concentrations in the northern reach of the estuary (6 pM) and approximately two orders-of-magnitude above natural concentrations in adjacent coastal waters (3 pM). The excess silver is primarily attributed to wastewater discharges of industrial silver to the estuary on the order of 20 kg d^?1. The contamination is most evident in the south bay, where wastewater discharges of silver are on the order of 10 kg d^?1 and natural freshwater discharges are relatively insignificant. The limited amount of freshwater flushing in the south bay was exacerbated by persistent drought conditions during the study period. This extended the hydraulic residence time in the south bay (≥160 d), and revealed the apparent seasonal benthic fluxes of silver from anthropogenically contaminated sediments. These were conservatively estimated to average ≈16 nmol m^?2 d^?1 in the south bay, which is sufficient to replace all of the dissolved silver in the south bay within 22 d. Benthic fluxes of silver throughout the estuary were estimated to average ≈11 nmol m^?2 d^?1, with an annual input of approximately 540 kg yr^?1 of silver to the system. This dwarfs the annual fluvial input of silver during the study period (12 kg yr^?1) and is equivalent to approximately 10% of the annual anthropogenic input of silver to the estuary (3,700–7,200 kg yr^?1). It is further speculated that benthic fluxes of silver may be greater than or equal to waste water fluxes of silver during periods of intense diagenic remobilization. However, all inputs of dissolved silver to the estuary are efficiently sorbed by suspended particulates, as evidenced by the relatively constant conditional distribution coefficient for silver throughout the estuary (K_d≈10⁵).     

Sulfate enrichments in estuarine waters of North Carolina

Sulfate concentrations in the mesohaline surface waters of the Pamlico and Neuse River estuaries were enriched, relative to the conservative seawater ratio with Cl^? (0.0517 (M)), by 5 to 43% between late winter and early summer. During this period, sulfate concentrations increased to a maximum excess of 3.5 mM in the bottom waters (0.5 m deep) through intermittent periods of both very low river flow and bottom water anoxia. The calculated net sulfate production rate for this period was 18 mmol per m² per d in the bottom waters. By late summer, the excess sulfate (an average of 12 mol per m²) had been removed from the water column, presumably due to SO₄ ^?2 reduction in anoxic bottom waters and sediments. Qualitative laboratory experiments with slurries of mud exposed to excess O₂ and treated with inhibitors of cytochrome oxidase showed that it was possible to produce the excess SO₄ ^?2 under these conditions via biochemical (not chemical) oxidation of pyride that occurs within the top 5 cm of mud (ca. 100 mmol pyrite-S per g dry mud). Whether the in situ substrate for SO₄ ^?2 production was pyrite, S⁰, or S⁺², is unknown, but the predominance of aqua regia extractable pyrite-Fe and the accumulation of excess SO₄ ^?2 in slurries with insufficient other sources of oxidizable S, indicates that it may be an important substrate for biochemical production of SO₄ ^?2.     

On the use of the nephelometer in estuarine waters

A study of the problems encountered in nephelometric determinations of suspended sediment loads in the Chesapeake Bay estuary has led to development of a technique which uses nephelometer readings as a guide for sampling at vertical profiles in an estuary. This permits optimum sampling for concentration profiles and allows one to use nephelometer/load ratios to characterize particles.     

Diel biogeochemical cycling in a hyperventilating shallow estuarine environment

A diel biogeochemical study was performed to assess the influence that periods of elevated biological activity have on the biogeochemical cycling of macronutrients and redox-sensitive elements in a natural estuarine environment. High-resolution data (15 min sampling) illustrates periodic extreme variations in dissolved oxygen (DO) in the shallow waters of Azevedo Pond, Elkhom Slough, California. During periods of low tidal flushing, DO values can range from highly oxic (>560 μM O₂: >250% saturation) during sunny days to suboxic conditions (<5 μM) at night. Nutrient cycling and redox-sensitive trace element biogeochemistry were evaluated in response to the extreme daily DO fluctuations. A diel sampling study was conducted over a 26-h period, where O₂ concentrations ranged from 346 μM to sustained non-detectable levels in the night hours. In concert with the DO fluctuations, diel phosphate cycling was on the order of 4 μM in response to tidal flushing events and biological assimilation and regeneration. The IO₃ ⁻/I⁻ redox couple quickly responded to suboxic conditions in the water column by a marked increase in I⁻ concentrations and corresponding depletion of IO₃ ⁻. The extreme fluctuations of the p∈ in the water column resulted in diel dissolved Mn²⁺ variations of nearly 5 μM, with observed dissolved Mn removal rates on the order of 1 μM h⁻¹. The elevated biogeochemical cycling of oxygen, nitrogen, phosphorus, iodine, manganese, and iron found in this shallow estuarine environment suggest that tidal restrictions and anthropogenic nutrient enrichments can amplify diel variations and potentially hinder the functional and ecological stability of these systems. These data suggest that accurate chemical monitoring of the health of an estuarine ecosystem must account for the diel variability inherent in these highly productive environments.     

Detoxification of chlorinated sewage effluent by dechlorination in estuarine waters

Secondary treated sewage was chlorinated to a residual level of 2–10 mg/l in a continuous flow system in the laboratory and diluted to various levels with estuarine water. A portion of the chlorinated sewage effluent was dechlorinated with sodium thiosulfate and the dechlorinated waste was diluted with estuarine water in the same proportions as the chlorinated waste.Menidia menidia, Palaemonetes pugio andCrassostrea virginica were exposed to chlorinated and dechlorinated treatments. High concentrations of chlorinated effluent caused mortalities inM. menidia andP. pugio, whereas similar concentrations of dechlorinated wastes did not cause mortalities. Mortalities in the chlorinated waste are correlated with chlorine residuals. Similarly, the chlorinated wastes depressed the shell deposition rate ofC. virginica below 50% of controls at all doses. Dechlorinated waste allowed shell deposition greater than 50% of controls. However, the occurrence of some growth inhibition inC. virginica exposed to dechlorinated waste suggests the presence of toxic material in the waste other than chlorine.     

海湾水库蓄水初期的单次往复密度流

为了探讨海湾水库蓄水初期单次往复水平密度流的产生与效应,进行砂质斜坡沉积物与水体之间盐分交换的水槽实验。通过沉积物孔隙水与其上覆水的多剖面电导率动态监测,分析盐分的时空分布特征,并计算深水区、浅水区和中心区的边界层单位面积含盐总量。实验结果显示,进水在浅水区沉积物表面产生明显的渗入-溢出现象,浅水区沉积物孔隙水盐分浓度显著低于中心区与深水区同一高度的盐分浓度,深水区初始底边界层含盐量与初始边界层下边界盐分浓度均为最高;这表明进水过程在倾斜沉积物表面产生了前进密度流,水流携带的盐分在坡底累积。水槽进满水后深水区边界层含盐总量与边界层下边界盐分浓度快速降低,并且浅水区表层沉积物孔隙水与深水区同一深度水体之间的盐分快速达到平衡;这表明蓄水初期在两者之间形成了返回密度流,从浅水区表层沉积物冲刷出的盐分在密度流作用下再次进入沉积物。为避免再次进入沉积物的盐分在后期继续影响水库泛咸,建议在蓄水结束后尽快实施坡底咸水排除方案。     

Wind-generated tool marks resembling trace fossils in a shallow estuarine environment

A suite of tool marks were observed in the seaward section of a small estuary on the south coast of New South Wales. The marks were formed through wind-generated waves dragging Eucalyptus leaves and Casuarina fronds over the backshore sands that separate the closed estuary from the sea. Some of the marks formed through the process of tilting, which has not previously been recognised in an Australian setting. A number of the more complex marks closely resemble trace fossils left by fish, and differentiation between the two in the sedimentary record could be difficult. If correctly identified as tool marks, then they could give a spurious estimate of palaeoflow direction, as they correspond to the orientation of the prevailing winds at the time of formation. This study highlights the need for judicious interpretation of ambiguous grooves in the sedimentary record.     

羌塘盆地浅层地震探测方法技术

西藏羌塘盆地地震地质条件复杂,要取得高质量的浅层地震勘探资料是非常困难的。文中结合多次在羌塘地区开展的浅层反射地震勘探方法技术试验,探讨了高原冻土层对地震资料的影响因素,地震数据采集采用了小道间距、多道数长排列的接收方式,同时提高覆盖次数,采用大吨位可控震源进行高频激发,获得了高质量的原始数据资料;在地震数据处理阶段,重点在叠前采取相应的去噪处理技术,能够有效地衰减震源干扰波、随机和相干噪声等干扰,获得信噪比较高的地震成像剖面。总结研究区浅层地震勘探的数据采集方法和资料处理解释技术,取得了较好的试验研究成果,对今后在高原冻土区开展浅层地震勘探方法技术的应用与研究有一定的借鉴作用。     

原位“Darcy实验”方法研究与实践

在室内Darcy实验原理和装置的基础上,设计了一套原位“Darcy实验”装置,原位试验条件满足Darcy定律的假定条件,能够应用Darcy定律确定包气带浅表层土的渗透系数.与室内“Darcy实验”相比,原位“Darcy实验”的测试结果更能准确地反映结构性土野外状态下的渗透性能.与其它原位试验相比,该方法在获取渗透系数方面具有试验装置简单、操作方便、观测数据直观的优点.应用该方法在中国西北部半干旱的黄土台塬开展了3组测试,成功地求取了区内包气带浅表层饱和黄土的垂向渗透系数,并将测试结果与双环试验、室内渗透试验、抽水试验及颗粒分析方法求得的渗透系数结果进行对比分析,发现应用原位“Darcy实验”求取的渗透系数更能准确地反映包气带浅表层土的渗透性能.同时,总结和探讨了一套原位“Darcy实验”的技术方法.     

Tidal straining,density currents,and stirring in the control of estuarine stratification

Buoyancy input as fresh water exerts a stratifying influence in estuaries and adjacent coastal waters. Predicting the development and breakdown of such stratification is an inherently more difficult problem than that involved in the analogous case of stratification induced by surface heating because the buoyancy input originates at the lateral boundaries. In the approach adopted here, we have adapted the energy considerations used in the surface heating problem to describe the competition between the stabilizing effect of fresh water and the vertical mixing brought about by tidal and wind stirring. Freshwater input induces horizontal gradients which drive the estuarine circulation in which lighter fluid at the surface is moved seaward over heavier fluid moving landward below. This contribution to stratification is expected to vary in time as the level of turbulence varies over the tidal cycle. The density gradient also interacts directly with the vertical shear in the tidal current to induce a periodic input to stratification which is positive on the ebb phase of the tide. Comparison of this input with the available stirring energy leads to a simple criterion for the existence of strain-induced stratification. Observations in a region of Liverpool Bay satisfying this criterion confirm the occurrence of a strong semidiurnal variation in stratification with complete vertical mixing apparent around high water except at neap tides when more permanent stratification may develop. A simulation of the monthly cycle based on a model including straining, stirring, and the estuarine circulation is in qualitative agreement with the main features of the observations.     

Removal of dissolved boron and silicon during estuarine mixing of sea and river waters

The behaviour of dissolved boron and silicon during mixing of sea and river waters has been studied in two surveys of the estuary of the River Alde in Suffolk, England. Removal of approximately 25–30 per cent was found for both elements. This appears to be the first report of estuarine removal of dissolved boron. The extent of removal of silicon in the Alde is somewhat higher than that found in other estuaries.     

Survival of F-RNA coliphages and three bacterial indicators during wastewater chlorination and transport in estuarine waters

Three bacterial water quality indicators,Clostridium perfringens, enterococci, and fecal coliforms, were compared to F-RNA coliphages for their survival during chlorination at several municipal wastewater treatment plants in Rhode Island and seasonally during transport in a section of the Narragansett Bay estuary. F-RNA coliphages were used as the best available indicator for the survival of Noroviruses (formerly Norwalk-like virus), the most frequently identified agent for the most prevalent waterborne disease (an acute but benign gastroenteritis), which has yet to be propagated in tissue culture and for which there is no lower animal model. Inactivation of the enterococci and fecal coliforms during wastewater chlorination was much greater than that of the F-RNA coliphages whose inactivation was essentially the same as that of C.perfringens. Survival of the F-RNA coliphages andC. perfringens during winter transport down Narragansett Bay were comparable to each other and greater than that for the enterococci or fecal coliforms. During the summer,C. perfringens survived longer than the other three indicators, possibly because the virus-like (F-RNA coliphages) and the two vegetative bacterial indicators were more susceptible than theC. perfringens spores to the lethal effects of sunlight and elevated water temperatures during the summer. Based on these findings, F-RNA coliphages seems to be a reliable indicator of viral contamination and die-off in estuarine waters.     

Hydrogeochemistry of karst underground waters at shallow depth in Guiyang City, Guizhou Province

The aim of this study is to shed light on the hydrogeochemical characteristics of karst underground waters at shallow depth in Guiyang City, Guizhou Province with an emphasis on the geochemistry of major elements. Guiyang City bears abundant underground waters and it is also an important representative of the karst areas throughout the world. Ca^2 and Mg^2 are the dominant cations, accounting for 81% -99.7% of the total, and HCO3^- and SO4^2- are the dominant anions. Weathering of limestones and dolostones is the most important factor controlling the hydrogeochemistry of underground waters, and weathering of sulfate and evaporite rocks is less important. Moreover, the precipitation and human activities also have a definite influence on the hydrogeoehemistry of underground waters in the region studied.     

Pliocene sedimentation in a shallow, cool-water, estuarine gulf, Murray Basin, South Australia

The Pliocene Norwest Bend Formation is a well‐preserved succession of terrestrial and shallow‐marine deposits in the Murray Basin, South Australia. Sediments in this unit consist of two discrete terrigenous clastic‐rich, decametre‐scale sequences, or informal members, which record episodes of marine incursion during the Early and Late Pliocene respectively. The base of each sequence is a transgressive lag and/or strandline deposit that is transitional upwards into a highstand, subtidal, terrigenous clastic and cool‐water carbonate sediment accumulation. The top of each sequence is incised by fluvial channels that are filled by river deposits which formed as relative sea‐level fell and terrestrial environments prograded basinward. Sedimentological data suggest that gross stratigraphic architecture was primarily determined by glacioeustasy. Differences in sedimentary style between these two sequences, however, reflect a major climatic change that took place in southern Australia during the mid‐Pliocene. The lower quartzose sand member is formed of siliciclastic sediment derived from prolonged, deep, subaerial weathering and contains a bivalve‐dominated, cool‐temperate, open‐marine mollusc assemblage. These sediments accumulated under an equitable, relatively warm, humid climate. The Murray Basin during this time, because of high fluvial discharge, was a salt‐wedge estuary with typical estuarine circulation. In contrast, the upper, oyster‐rich member is typified by large monospecific oyster buildups that grew in restricted coastal environments. Strandline deposits contain a warm‐temperate skeletal assemblage. Contemporaneous aeolian sediments accumulated under warm, semi‐arid climatic conditions. Well‐developed ferricrete, silcrete and calcrete horizons reflect cyclic conditions of rainwater infiltration and evaporation in the seasonally dry climate that typifies southern Australia today. Highly seasonal rainfall produced an estuary that fluctuated annually from being well to partially mixed. These Pliocene sediments support the notion that mollusc‐rich facies are the signature of cool‐water carbonate accumulations in inboard neritic environments. Unlike bryozoans that dominate the outer parts of Cenozoic cool‐water carbonate shelves, molluscs evolved to exploit an array of coastal ecosystems with wide salinity variations and variable sedimentation rates.