13 research outputs found
Seawater alkalinity determination by the pH method
The coefficient fH used in the seawater alkalinity method of Anderson and Robinson (1946), has been redetermined at 25°C. We have found that fH = 0.741 ±0,005 for salinities between 30‰ and 41‰…
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Pressure dependence of the apparent dissociation constants of carbonic and boric acids in seawater
A comparison of methods for the determination of dissolved oxygen in seawater
An intercalibration of dissolved oxygen methods was conducted at 2 stations
in the Sargasso Sea between April 28 and May 3, 1990. The experiment compared
three techniques using automated endpoint detection with the manual Winkler method using a starch endpoint. Institutions participating in the
intercomparison were the Bedford Institute of Oceanography (automated photometric
titration), the University of Delaware (automated amperometric titration), the
Scripps Institution of Oceanography (manual titration), and the Woods Hole
Oceanographic Institution (automated amperometric titration).
Differences in measured oxygen concentrations between institutions were
encouragingly small. However, small, systematic differences in dissolved oxygen
between institutions did exist. The range between the highest and lowest oxygen
values reported by the 4 institutions never exceeded 0.6% over the entire
concentration range studied (3.4 to 6.2 mlj1). The good agreement is probably
due to the use of the essentials of Carpenter's (1965) modification of the
Winkler method by all institutions.
The intercalibration revealed several aspects of dissolved oxygen
measurements that require further research: (1) the intercalibration should be
extended to very low oxygen concentrations; (2) procedures for measur ing and
applying corrections for the seawater blank need to be formalized; (3) a simple
procedure to measure the temperature of seawater at the time of sampling needs
to be developed; and (4) the solubility of atmospheric oxygen in the Winkler
reagents must be measured as a function of temperature.
The intercalibration also revealed that analytical techniques required for
precise and accurate volumetric measurements were often not applied, even by
experienced analysts. It was found that uncalibrated pipets were used to
dispense standards, that the volumes of oxygen flasks were not corrected for
buoyancy, and that corrections for the thermal expansion of aqueous solutions were often not applied.This research was supported by National Science Foundation Grants OCE 88-
22542 and OCE 88-21977 and OCE 89-07815. Preparation and distribution of this
report by the WHP Office, Woods Hole Oceanographic Institution, Woods Hole, MA.
02543 USA, was supported by NSF Grant OCE 89-07815
Foraminifera, paleoecology, and biostratigraphy of the Paleocene "Ostrea thirsae beds", Nanafalia Formation, West-Central Alabama
Eighty-four species of foraminifera are recognized in the "Ostrea thirsae Beds" at the type locality and in the type area of west-central Alabama. Benthonic species comprise 96 percent of the total foraminiferal fauna. Anomalinoides umboniferus (Schwager) is the dominant element, averaging 45 percent of the total population, but ranging from eight to a maximum of 81 percent of the population of any one sample. Important subordinate benthonic species include Lenticulina midwayensis (Plummer), Discorbis washburni Garrett, Eponides lotus (Schwager), Cibicides howelli Toulmin, Gyroidinoides octocameratus (Cushman and Hanna), and Pulsiphonina wilcoxensis (Cushman). Discorbis washburni Garrett and Gyroidinoides lottensis (Garrett) are persistent benthonic species restricted to the "Ostrea thirsae Beds". Paleoecologic interpretation of the "Ostrea thirsae Beds" indicates accumulation within the middle-neritic (depths of 50 to 300 feet) marine environment with open-marine circulation. Planktonic foraminifera are represented by seventeen species. Globorotalia pseudomenardii Bolli and Globorotalia pusilia laevigata Bolli establish the beds as middle Late Paleocene in age, equivalent to the upper part of the type Thanetian Stage in Europe. The range zone of Globorotalia pseudomenardii appears to have a worldwide geographic distribution, providing for biostratigraphic correlation of the "Ostrea thirsae Beds" with Europe, the Mediterranean, Southern India, the Soviet Union, and Australia, as well as North and South America.Earth and Atmospheric Sciences, Department o
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Processes affecting the oceanic distribution of carbon dioxide
The stoichiometric model of organic decomposition in seawater
(Redfield, Ketchum, and Richards, 1963) was used to describe the
oceanic distribution of total carbon dioxide. It was assumed that the
concentration of total carbon dioxide was the sum of three terms:
(1) the initial concentration of carbon dioxide, (2) the increase in
carbon dioxide due to the oxidation of organic matter, and (3) the
increase in carbon dioxide due to the solution of calcium carbonate.
The initial concentration of carbon dioxide was calculated by assuming
that surface seawater is in equilibrium with atmospheric carbon
dioxide. This assumption allowed the temperature dependence of the
initial concentration to be estimated. The vertical and horizontal
distribution of total carbon dioxide in the Pacific, Indian, and South
Atlantic Oceans was shown to conform to this model. In particular,
values of the oxidative ratio (ΔC/ΔO) calculated from field data agreed
with the theoretical value of Redfield et al. (1963).
The model for the distribution of total carbon dioxide was applied
to the vertical distribution of carbon-13 at the North Pacific (1969)
GEOSECS intercalibration station (Kroopnick, Deuser, and Craig,
1970). Values of δC¹³ calculated from the stoichiometric model
agreed to within ± 0.3‰ with the measured values at this station.
Near-bottom chemical measurements were made on three
cruises: YALOC-69 to the Eastern Tropical Pacific, Y6908F off the
Oregon Coast, and TT-46 to the Caribbean Sea and North Atlantic.
The emphasis during these cruises was on chemical gradients in
deep water, and 39 stations were occupied at depths greater than
2000 m. Salinity, oxygen, pH, alkalinity, silicate, phosphate,
nitrate, and nitrite were measured at heights from 0.5 to 300 m
above the bottom. No measurable salinity, oxygen, silicate, phosphate,
nitrate, or nitrite gradients were observed. A statistically
significant near-bottom increase in pH and alkalinity was found.
However, the increase was small and could have resulted from
undetected analytical and/or sampling errors
Land grant to M. J. Thurman of 160 acres, decreed by Governor Charles A. Culberson
Land grant to M. J. Thurman of 160 acres, decreed by Governor Charles A. Culberson
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Iodine chemistry in the water column of the Chesapeake Bay: Evidence for organic iodine forms
During the summer of 1987, we collected and analysed Chesapeake Bay water samples for the inorganic iodine species: iodide (by cathodic-stripping squarewave voltammetry) and iodate (by differential pulse polarography); and total iodine (by hypochlorite oxidation of the seawater sample to iodate). The difference between the sum of the inorganic iodine species and the total iodine was significant for about one-third of the samples collected from the Bay. Thus, in these samples, a third (or more) ‘new’ form(s) of iodine was present. These samples were primarily from oxygen-saturated surface waters of high biological activity (primary productivity and bacterial processes). This ‘new’ form can make up as much as 70% of the total iodine. Waters containing low oxygen concentrations showed less of this ‘new’ form of iodine whereas anoxic and sulphidic bottom waters contained only iodide. This ‘new’ form of iodine is organic in nature and probably non-volatile. It may reside in the peptide and humic fractions.
Only reduced iodine (iodide and organic iodine) was detected in waters from the northern section of the Bay, whereas only iodide and iodate were detected in the southern section of the Bay. In only two samples were iodide, iodate and the ‘new’ form of iodine found to coexist. Iodide and organic iodine are probably cycled in the surface waters of the northern section of the Bay via a combination of biogeochemical and photochemical processes which produce the reactive intermediates, molecular iodine and hypoiodous acid. These react quickly with reduced inorganic and organic compounds to maintain the reduced forms of iodine in the water column. Only total iodine is conservative throughout the estuary. The inorganic iodine forms can be used as geochemical tracers