Total Carbon Analysis Research Articles

Lake levels for the past 19,000 years from the TL05-4 cores, Tulare Lake, California, USA: Geophysical and geochemical proxies

Geochemical and geophysical proxy data from the TL05-4 lake-plain cores of Tulare Lake, California, are reported on here representing most of the past 19,000 years. The new record consists of carbon/nitrogen ratios, total organic carbon (TOC), nitrogen (N), total inorganic carbon (TIC), grain size, and magnetic susceptibility analyses from samples taken at 1-cm intervals (∼45 yr/sample). Age control is provided by 22 radiocarbon dates. The first part of the record (∼19.0–14.5 cal ka BP) consists of elevated sand and silt percentages and higher sedimentation rates interpreted as elevated runoff associated with melting of the Tioga-age Sierra Nevada ice cap. The TIC was undetectable and TOC and N were low suggesting low productivity in a relatively sterile, freshwater lake. From 14.5 to 10.3 cal ka BP, the deposits consisted of 50% clay and 50% silt with TIC and TOC extremely low, which is consistent with a stable, low productivity lake. From 10.3 to 7.5 cal ka BP, an initial pulse of fining upward sand gave way to increased clay deposition that suggests a lake transgression to a stable highstand, coeval with the deep water event found in previously published records of Tulare Lake and other lakes from central and southern California, including Owens Lake and Lake Elsinore. A few-hundred-year duration spikes in TIC centered at 8.0 cal ka BP is suggestive of evaporating lake conditions toward the end of this early Holocene highstand. Tulare Lake dropped quickly to a relative low at 7.5 cal ka BP, but then lake level increased steadily until 3.0 cal ka BP. High amplitude fluctuation in almost all proxies occurs from 2.5 to 1.8 cal ka BP at the end of the record, suggesting that this time interval was characterized by rapid fluctuations in lake level. Tulare Lake levels during the Holocene vary in conjunction with sea surface temperature (SST) records from the Ocean Drilling Program (ODP) Site 1017 located off the coast of central California, which suggests that variations in SSTs throughout the Holocene drove changes in precipitation in the Sierra Nevada and hence, Tulare Lake level. Since historic lake-level histories have been shown to be directly related to stream discharge from the Sierra Nevada, this observation will be integral in forecasting future decadal-scale changes in southern San Joaquin Valley water supply due to anticipated climate change.

Late Quaternary strata and carbon burial records in the Yellow River delta, China

Sediment carbon sequestration plays an essential role in mitigating atmospheric CO2 increases and the subsequently global greenhouse effect. To clarify the late Quaternary strata and carbon burial records in Yellow River delta (YRD), detailed analysis of benthic foraminifera, total carbon (TC), organic carbon (Corg), sedimentary characteristics and moisture contents of sediments, was performed on core ZK3, 30.3 m in length and obtained from YRD in 2007. Eight depositional units (designated U1-U8 in ascending order) were identified. A comprehensive analysis method of historical geography and sedimentary geology was used to determine the precise depositional ages of the modern Yellow River delta (MYRD), from which pre-MYRD ages were deduced. The results indicates that the maximum burial rates of TC, inorganic carbon (IC) and Corg occurred in the delta front (U5), and the minimum in the shallow sea (U3). Remarkable high sedimentation rates in the MYRD are responsible for burial efficiency of carbon, with an average rate of Corg burial reaching 2087±251 g (m2 yr)−1, and that of IC reaching 13741±808 g (m2 yr)−1, which are much higher than those of other regions with high contents of Corg. Therefore, YRD has a significant burial efficiency for carbon sequestration.

Synthesis of homogeneous sphere-like Bi2WO6nanostructure by silica protected calcination with high visible-light-driven photocatalytic activity under direct sunlight

The homogeneous sphere-like morphology of bismuth tungstate (Bi2WO6) was synthesized by silica protected calcination using a facile hydrothermal method followed by silica etching. The flower-like Bi2WO6 structure was synthesized without silica protection. SEM and TEM analysis of the samples at different hydrothermal reaction times reveals that the growth of in situ formed nanoplates was controlled by silica protection which leads to the formation of the sphere-like structures of Bi2WO6. The homogeneous sphere-like structure was retained up to 1 h of etching period with complete removal of the silica layer. Subsequently, both the flower and sphere-like Bi2WO6 were used as photocatalysts for the degradation of reactive black 5 (RB5) dye under direct sunlight irradiation. Sphere-like Bi2WO6 exhibited excellent visible-light-driven photocatalytic efficiencies by complete degradation of the RB5 dye within 3 h compared with the flower-like Bi2WO6 (45%, 3 h) structure. The enhancement in photocatalytic activity using homogeneous sphere-like Bi2WO6 was confirmed by kinetic studies, chemical oxygen demand, total organic carbon and total inorganic carbon analysis.

Photolysis of phenylalanine in the presence of oxidized carbon nanotubes.

Photolyses at 254 nm of phenylalanine (Phe) in aqueous solutions, were carried out in the presence of oxidized carbon nanotubes modified by the reaction with SO2 (mNTO). Kinetics of the photolyses were followed by UV spectrophotometry at 220 nm, and the products were characterized by HPLC, XPS, and (13)C-SSNMR. The ratio of the initial rates of photolysis in the presence and absence of mNTO, k*/ko*, showed a systematic decrease. The photolytic decay of Phe occurs with minor formation of tyrosine. The mass of nanotubes produced an exponential attenuation of the photolytic decomposition of Phe. Total carbon analyses (TCA) showed no inorganic carbon formation after the photolyses. The first-order rate constant of photofunctionalization of mNTO by the insertion of phenylalanine onto the nanotube matrix was calculated from TCA to be kin = 30.1 min(-1). Comparison of the XPS spectra of the mNTO before and after the photolysis, using the atom inventory technique, suggests the insertion of Phe along with the extrusion of a sulfide radical anion ((•)S(-)) which undergo subsequent oxidation to SO4(2-). The obtained results show the effects of mNTO on the photolysis of Phe and provide a new method of photofunctionalization of carbon materials, modified by the intermediates of the reduction of SO2, with an organic moiety.

Quantitative and qualitative study of density driven CO2 mass transfer in a vertical Hele-Shaw cell

The density driven convection phenomenon is expected to have a significant and positive role in CO2 geological storage capacity and safety. But predictions on reservoir time and space scales are difficult to validate because data are generally sparse and will only be useful for a small part of the relevant time period. Laboratory scale data are valuable to validate the numerical models. In this paper we focus on the comparison of experimental and numerical determination of CO2 mass transfer in a laboratory experiment. We developed an experimental protocol for the determination of density-driven mass transfer of CO2 in water-saturated Hele-Shaw cells with different apertures. We used a CCD camera to capture images of the initiation of density-driven convection caused by dissolution of CO2 in water and the subsequent development of convective fingers. The visualization of the phenomenon allowed consistently stopping the experiment when dissolved CO2 first reached the bottom of the cell. We determined the total mass of dissolved CO2 during the experiment using a catalytic combustion-based total carbon analyzer (TC-analyzer). This experimental procedure was repeated several times for uncertainty analysis. Thus a combination of quantitative and qualitative experimental results for the same Hele-Shaw cell configuration was obtained for validation of corresponding numerical simulation results. A numerical simulation of the phenomenon was carried out using the STOMP-WCS simulator. We found that in order to accurately simulate numerically the phenomenon occurring in the Hele-Shaw cell, existent variations in the cell apertures should be taken into account. Thus we observed a good agreement between the experimental and numerical results in terms of total dissolved CO2 mass, timescale of mass transport and morphology of the convection fingers. In addition correlations are obtained between total dissolved CO2 mass, arrival time of dissolved CO2 to bottom of the cell, and the Rayleigh number.

Photocatalytic degradation of a textile dye Reactive Red 31 using phyto-synthesized titanium nanoparticles under solar irradiation

In the present work, we have reported a sustainable and effective method for the degradation of a textile dye Reactive Red 31 (RR31) using synthesized titanium nanoparticles. Titanium dioxide nanoparticles were synthesized using a noxious weed, Parthenium hysterophorus, as reducing and capping agent for the first time. The synthesized nanoparticles were characterized and confirmed as TiO2 nanoparticles by using X-ray diffraction spectroscopy, Fourier transformation infrared spectroscopy, and scanning electron microscopy analysis. A glass reactor was designed and developed for the degradation of dye under solar radiations. Photocatalytic degradation of Reactive Red 31 was carried out at different concentrations using synthesized nanoparticles. UV–vis spectroscopy, total organic carbon, and total inorganic carbon analysis were carried out for the determination of dye degradation. The results reveal that biogenic TiO2 nanomaterial acts as a good photocatalyst for the degradation of textile dye Reactive Red 31.

A study on removal characteristics of o-, m-, and p-nitrophenol from aqueous solutions by organically modified diatomaceous earth

The natural diatomaceous earth (DAT) was modified with surfactant of hexadecyltrimethylammonium bromide (HDTMABr) to form organic-modified diatomaceous earth (DAT-HDTMABr). The DAT and DAT-HDTMABr were characterized by X-ray fluorescence, X-ray diffraction, FT-IR and DTA-TG. The surface area was determined using Brunauer, Emmett, and Teller adsorption method. Cation exchange capacity was estimated using an ethylenediamine complex of copper method, and the modifier loading was calculated from the total carbon analysis. The ability of raw and organomodified diatomaceous earth to remove o-nitrophenol (ONP), m-nitrophenol (MNP), and p-nitrophenol (PNP) from aqueous solutions has been carried out at predetermined equilibration time, adsorbent amount, pH, and temperatures using a batch technique. The removal of ONP, MNP, and PNP from aqueous solutions by modified clay seems to be more effective than unmodified sample. The experimental equilibrium adsorption data were analyzed by four widely used two parameters, Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich (D–R) isotherm equations. Kinetic studies showed that pseudo-second-order described the adsorption experimental data better than the pseudo-first-order kinetic model. Based on the calculated thermodynamic parameters, such as enthalpy (ΔH), entropy (ΔS), and Gibb’s free energy changes (ΔG), it is noticeable that the adsorption of ONP, MNP, and PNP by DAT and DAT-HDTMABr adsorbents was carried out spontaneously, and the process was exothermic in nature.

Forsterite Carbonation in Zones with Transport Limited by Diffusion

Fractures in rocks could provide substantial surface area for reactions that lead to carbonate mineral precipitation in geologic carbon sequestration. Diffusion-limited transport of solutes in such zones affects the spatial and temporal distribution of mineral dissolution rates and carbonation products, thus influencing the overall carbon sequestration process. A tube with a packed bed of forsterite and exposed at one end to a solution in equilibrium with 100 bar of CO2 at 100 °C was used to explore the timing and spatial localization of carbonate precipitation along a one-dimensional diffusion-limited zone. The identity and quantity of carbonate minerals as a function of depth were determined using Raman spectroscopy and total carbon analysis. Carbonate was observed within the packed bed as early as day 1. Hydromagnesite formed in the bed first and was replaced by magnesite within 5 days. Carbonate was spatially localized with the largest amount formed 0.5 cm into the packed bed. The overall carbonation ...

Improving the carbon balance of fermentations by total carbon analyses

Carbon balancing of microbial fermentations is a valuable tool for the evaluation of the process performance and to identify the presence of undesired by-products. In this study, we demonstrate the relevance of total carbon (TC) analysis for carbon balancing in fermentations with the wild-type of Corynebacterium glutamicum by (i) quantifying significant amounts of dissolved inorganic carbonic species (TIC) in the culture medium and (ii) determining the effective (mass) carbon content of the biomass fraction (MC,X). In principle, TC based carbon balancing yielded at fully matching carbon balances. Thus, the application of our TC approach for the accurate detection of TIC and MC,X increased the total carbon recovery in standard batch fermentations with C. glutamicum on glucose from about 76% to carbon closures of 94–100% in contrast to conventional approaches. Besides, the origin of the missing 6%-gap could be attributed to incomplete quantification of all carbon sources in the liquid phase. To conclude this study, the concept of TC-based balancing was transferred to an l-lysine production process, successfully quantifying relevant system carbon fractions, which resulted in matched carbon recoveries.

Chemistry and product quality of an NH3–CO2 forward osmosis desalination system

This study examined the chemistry of a forward osmosis (FO) desalination system, which employs ammonium bicarbonate as the draw solute. The Indophenol blue photometric technique and a total carbon analyzer were used to determine the ammonia concentration and carbonate species concentration, respectively. The equilibrium relationships of the concerned species in water were used to analyze the distribution of ionic and gaseous species present in the solution at different stages of the process. The results can be used to evaluate the economic and environmental feasibility of the FO desalination process for water supply.

Interaction of natural and thermally processed vermiculites with gaseous carbon dioxide during mechanical activation

The interaction of natural and thermally processed (exfoliated and heated) vermiculites with CO2 during mechanical activation in a planetary ball mill (in-situ) and in an autoclave after mechanical activation (ex-situ) was investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), surface area analyses and total carbon analyses. Mechanical activation under an air or a CO2 atmosphere, especially in wet mode, increased the surface area and pore volume of the studied vermiculites. Moreover, activation under a CO2 atmosphere resulted in a higher degree of amorphisation (comparing the basal reflections in the XRD patterns of the vermiculites milled under air or CO2), indicating that CO2 interacted with the sample during activation. From this type of interaction, a maximum CO2 content of 2.74% was determined for the heated vermiculite sample that was mechanically activated in dry mode under a CO2 atmosphere. If the interaction with CO2 was performed in an autoclave following mechanical activation, hydromagnesite crystallisation occurred, and a maximum CO2 content of 3.22% was found for the thermally exfoliated sample.In the FT-IR spectra, the observed bands attributed to carbonate in the range of 1430–1550cm−1 were singlets (for the natural and thermally exfoliated vermiculites) or split (for the heated vermiculite). This effect is likely due to structural breakdown and increased amorphisation created by heating and mechanical activation.

Organic matter characterization of sediments in two river beaches from northern Portugal for forensic application

In a forensic investigation, the analysis of earth materials such as sediments and soils have been used as evidence at a court of law, relying on the study of properties such as color, particle size distribution and mineral identification, among others. In addition, the analysis of the organic composition of sediments and soils is of particular value, since these can be used as complementary independent evidence to the inorganic component. To investigate the usefulness of organic indicators in sediment characterization and discrimination, seventy-seven samples were collected during a period of one year in two river beaches located at the southern bank of the Douro River estuary in the North of Portugal. Isotopes of total carbon, pollen and plant wax-marker analyses were performed. In both beaches, an increase of the organic matter concentrations was noticeable, moving landward, related with the higher cover of associated plant material. The results obtained showed that the combination of all the techniques adopted showed a clear discrimination between samples from the two beaches, and also showed a differentiation of samples in relation to distance from the river in both beaches. The results also show that seasonality in these beaches was not a determining factor for discrimination, at the times considered. In addition, the effects of time was not marked.

A highly reproducible solenoid micropump system for the analysis of total inorganic carbon and ammonium using gas-diffusion with conductimetric detection

In this work, a simple, economic, and miniaturized flow-based analyzer based on solenoid micropumps is presented. It was applied to determine two parameters of high environmental interest: ammonium and total inorganic carbon (TIC) in natural waters. The method is based on gas diffusion (GD) of CO₂ and NH3 through a hydrophobic gas permeable membrane from an acidic or alkaline donor stream, respectively. The analytes are trapped in an acceptor solution, being slightly alkaline for CO₂ and slightly acidic for NH₃. The analytes are quantified using a homemade stainless steel conductimetric cell. The proposed system required five solenoid micro-pumps, one for each reagent and sample. Two especially made air bubble traps were placed down-stream of the solendoid pumps, which provided the acceptor solutions, by this increasing the method's reproducibility. Values of RSD lower than 1% were obtained. Achieved limits of detection were 0.27 µmol L⁻¹ for NH₄⁺ and 50 µmol L⁻¹ for TIC. Add-recovery tests were used to prove the trueness of the method and recoveries of 99.5 ± 7.5% were obtained for both analytes. The proposed system proved to be adequate for monitoring purpose of TIC and NH₄⁺ due to its high sample throughput and repeatability.

IMPACTOS DA CONVERSÃO DE USO E MANEJO DO SOLO DO CERRADO UTILIZANDO DADOS DE CARBONO TOTAL E ISOTÓPICO

The middle region of Minas Gerais / High Paranaíba originally covered by Cerrado vegetation has been heavily deforested area for being a pioneer expansion of agribusiness. Among the various environmental changes related to deforestation include soil erosion and imbalances in stocks and the nature of carbon sources. Results of analysis of total carbon (Ctotal) and carbon isotope (δ 13C) of four categories of use - remnant of cerrado tree, rotation of soybeans and corn in no-tillage, pasture and degraded pasture managed - revealed that the conversion of use and management led to important changes in the nature and content of the soil carbon. The results presented can serve as important indicators of environmental impacts when natural ecosystems are converted into agricultural systems without the adoption of appropriate management.

Enhanced photocatalytic activity of bismuth-doped TiO2 nanotubes under direct sunlight irradiation for degradation of Rhodamine B dye

Bismuth-doped TiO2 nanotubes (Bi-TNT) were successfully synthesized by combination of sol–gel and hydrothermal methods. The synthesized photocatalyst was efficiently used for degradation of rhodamine B (RhB) dye under direct sunlight irradiation. Subsequent characterization of synthesized photocatalysts was carried out using PXRD, SEM, TEM, EDX, FT-IR, Raman, N2 adsorption, TPD-NH3, UV–Vis DRS, XRF and ICP techniques. The surface area of the TiO2 nanoparticles increased after tubular structure formation (TiO2 nanoparticles—114.21 m2/g, TiO2 nanotube—191.93 m2/g). The degradation studies revealed that initial rate of photocatalytic degradation of RhB dye using Bi-TNT was 5.56, 4.16, 1.30 and 2.38 times higher as compared to TNP, Bi-TNP, TNT and Degussa P-25 TiO2 (P-25), respectively, under direct sunlight irradiation. The enhanced photocatalytic activity of Bi-TNT may be due to the increase in the surface area and Bi doping, which leads to effective separation of photogenerated carriers. The degradation was confirmed by chemical oxygen demand, total organic carbon and total inorganic carbon analysis of the degraded dye solutions. The probable degradation mechanism of RhB dye has also been proposed using liquid chromatography-mass spectrometry analysis of degraded samples.

Effects of Timber Harvesting on Dissolved Oxygen in a Northern Louisiana Headwater Stream

Many headwaters in Louisiana have low concentrations of dissolved oxygen (DO) and there is a concern that timber harvesting can further decrease these concentrations. This study was conducted to examine the direct and long-term effect of timber harvest on DO in a low-gradient headwater stream in north-central Louisiana, USA. Water quality multisensor probes were deployed at two locations along a second-order stream, approximately 500 m apart. DO concentration and saturation were recorded at 15-minute intervals from 2006 to 2010. In addition, monthly site visits were conducted for streamflow measurement and water sample collection for biochemical oxygen demand (BOD) and total carbon (TC) analyses. In late summer 2007, a 45-ha loblolly pine stand between the two locations was clearcut, which allowed data analysis in a before-after and above- below control design. At the upstream site (control), concentrations of DO, BOD, and TC averaged 2.3, 1.3, and 26.5 mg L 1 , respectively. DO concentrations were mostly (83% of measurements) less than 1 mg L 1 during the summer and were frequently (33% of measurements) less than 2 mg L 1 during the winter. After the harvest, BOD and TC at the downstream site were significantly higher than those at the upstream site (paired t-tests; P 0.01; df 37 and 32, respectively), whereas water temperature at the downstream site increased only slightly (0.9° C). However, these changes did not lower DO under a range of flow conditions. After harvest, DO concentrations were significantly higher at the downstream site during both summer and winter (paired t-tests; P 0.001; df 126 and 313, respectively). The DO increase may have resulted from increased streamflow due to reduced evapotranspiration at the harvested site. Even with the harvest-induced DO increases, concentrations at both sites continued to fall below the Environmental Protection Agency-recommended 5-mg L 1 limit for greater than 70% of measurements, challenging the attainability of the current water quality standard. FOR .S CI. 59(2):127-138.

Soil total carbon analysis in Hawaiian soils with visible, near-infrared and mid-infrared diffuse reflectance spectroscopy

Accurate assessment of total carbon (Ct) content is important for fertility and nutrient management of soils, as well as for carbon sequestration studies. The non-destructive analysis of soils by diffuse reflectance spectroscopy (DRS) is a potential supplement or alternative to the traditional time-consuming and costly combustion method of Ct analysis, especially in spatial or temporal studies where sample numbers are large. This alternative technique has been utilized in several locations in the United States and elsewhere, but has not been tested on the unique and diverse tropical soils in Hawaii. This study investigated the feasibility of DRS for Ct prediction of Hawaiian agricultural soils by creating visible, near-infrared (VNIR) and mid-infrared (MIR) spectral libraries and developing chemometric models with partial least squares regression (PLSR) and random forests (RF) ensemble tree regression. The sample set contained 305 soils from across the five main Hawaiian Islands, representing 10 soil orders and over 100 soil series. The Ct of these samples measured by dry combustion ranged from <1% to 56%, greater than that of most previously published studies. The VNIR spectra of the soils commonly exhibited features associated with OH− and H2O, iron oxides, phyllosilicates, and organic molecules. The numerous features in the MIR spectra can be attributed to OH−, organic molecules, and a variety of silicate minerals, such as phyllosilicates and quartz. Excellent results were obtained from both PLSR models using VNIR and MIR spectra. The models had R2 values of 0.95/0.94 (VNIR/MIR), root mean squared error (RMSE) values of 2.80%/3.08%, residual prediction deviation (RPD) values of 4.25/3.91, and ratio of performance to inter-quartile distance (RPIQ) values of 3.66/3.38. The RF VNIR and MIR models were also of high quality, with R2=0.95/0.96 (VNIR/MIR), RMSE=2.82%/2.28%, RPD=4.27/5.28, and RPIQ=3.68/4.56. An evaluation of the different wavelength ranges and chemometric methods determined that for this sample set all were capable of robust predictions of Ct. These results indicate that DRS is an alternative technique for analysis of Ct in Hawaiian soils.

Degradation of azo dye with dirhodium(II) caprolactamate as heterogeneous catalyst

The kinetics of the oxidative degradation of an azo dye Metanil Yellow (MY) was investigated in aqueous solution using dirhodium(II) caprolactamate, Rh(2)(cap)(4), as a catalyst in the presence of H(2)O(2) as oxidizing agent. The reaction process was followed by UV/Vis spectrophotometer. The decolorization and degradation kinetics were investigated and both followed a pseudo-first-order kinetic with respect to the [MY]. The effects of various parameters such as H(2)O(2) and dye concentrations, the amount of catalyst and temperature have been studied. The studies show that Rh(2)(cap)(4) is a very effective catalyst for the formation of hydroxyl radicals HO(•) which oxidized and degraded about 92% of MY into CO(2) and H(2)O after 24 h as measured by total carbon analyzer.

Study on UV-LED/TiO 2 process for degradation of Rhodamine B dye

UV-light emitting diodes (UV-LEDs) was used for the photocatalytic degradation of Rhodamine B (RhB) dye to study the various parameters, effectiveness and feasibility for designing of photocatalytic reactor based on UV-LED irradiation in different conditions. The photocatalytic experiments were conducted using 5 UV-LED lights with same specification and Degussa P-25 TiO 2 as a photocatalyst. The effects of operational parameters such as catalysts loading, initial dye concentration, pH, addition of H 2O 2 and effect of metal ions (Zn 2+, Ag +, Fe 3+, Cu 2+ and Cd 2+) were studied for the photocatalytic degradation of RhB. A detailed degradation pathway has been suggested, which was based on the electrospray ionization mass spectrometry (ESI-MS) analysis. It was observed that the degradation of RhB occurred via N-de-ethylation process. N-de-ethylated product was further oxidized into acids and alcohols. The complete mineralization of RhB dye (2.08 × 10 −5 M) was confirmed by chemical oxygen demand (COD), total organic carbon (TOC), total inorganic carbon (TIC) and high pressure liquid chromatography (HPLC) analysis. The optimum conditions for higher percentage degradation of RhB dye obtained with amount of catalyst (1.6 g/L), dye concentration (6.26 × 10 −5 M) and pH = 3.05. Results demonstrated that the UV-LED/TiO 2 process can effectively degrade RhB dye with optimum conditions.

Paleoceanographic changes on the Farallon Escarpment off central California during the last 16,000 years

New benthic and planktic foraminiferal assemblage census data and Benthic Foraminiferal Oxygen Index (BFOI) values, previously published marine climate proxy data (stable isotopes and Ca/Cd), and unpublished results of total carbon, organic carbon, and calcium carbonate analyses of sediments recovered off central California on the Farallon Escarpment (1605 m water depth; 37°13.4′N, 123°14.6′W; core F-8-90-G21) document paleoceanographic changes during the latest Quaternary which reflect the intensity and source of North Pacific Intermediate Water (NPIW) and surface productivity. Accelerator mass spectrometry radiocarbon dates of both benthic and planktic species provide an excellent age-depth model for the last 16,000 years, covering the latest glacial, Bølling–Allerød, Younger Dryas, and early, middle, and late Holocene intervals. A Q-mode cluster analysis separated the benthic fauna into three clusters, one Pleistocene and two Holocene, whereas the planktic fauna was divided only into Pleistocene and Holocene clusters. Stable oxygen isotope values show an increase in water temperature of ∼1 °C from the late glacial to late Holocene and a change in faunal composition of the planktic assemblage implies surface waters warmed as well. A general trend of decreasing dissolved oxygen concentration from the Pleistocene (high oxic; 3.0–6.0+ ml/l O 2) to the Holocene (low oxic; 1.5–3.0 ml/l O 2) suggested by the BFOI and Cd/Ca data reflect decreased ventilation as the source of the NPIW shifted from the Sea of Okhotsk to the tropical east Pacific at ∼11,000 cal BP. The middle Holocene cooling reported in other central and northern California margin studies is not apparent in F-8-90-G21, which compares more favorably with studies from southern California and British Columbia. Total carbon and organic carbon values are highest in the Bølling–Allerød, early Holocene, and late Holocene. Similarly, calcium carbonate values are high in the Bølling–Allerød and peak in the early Holocene, but decrease significantly in the latest middle and late Holocene which coincides with a depauparate planktic foraminiferal fauna in the upper 60 cm (∼70000–0 cal BP) of the core and poor preservation of the benthic foraminiferal fauna at 40 cm (∼3000 cal BP). Decoupling is evident between the planktic and benthic faunal response to changing climatic conditions, with the surface-dwelling assemblage often leading the bottom-dwelling assemblage by several millennia.