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We estimate anthropogenic carbon (Canth) accumulation rates in the Pacific Ocean between 1991 and 2017 from 14 hydrographic sections that have been occupied two to four times over the past few decades, with most sections having been recently measured as part of the Global Ocean Ship‐based Hydrographic Investigations Program. The rate of change of Canth is estimated using a new method that combines the extended multiple linear regression method with improvements to address the challenges of analyzing multiple occupations of sections spaced irregularly in time. The Canth accumulation rate over the top 1,500 m of the Pacific increased from 8.8 (±1.1, 1σ) Pg of carbon per decade between 1995 and 2005 to 11.7 (±1.1) PgC per decade between 2005 and 2015. For the entire Pacific, about half of this decadal increase in the accumulation rate is attributable to the increase in atmospheric CO2, while in the South Pacific subtropical gyre this fraction is closer to one fifth. This suggests a substantial enhancement of the accumulation of Canth in the South Pacific by circulation variability and implies that a meaningful portion of the reinvigoration of the global CO2 sink that occurred between ~2000 and ~2010 could be driven by enhanced ocean Canth uptake and advection into this gyre. Our assessment suggests that the accuracy of Canth accumulation rate reconstructions along survey lines is limited by the accuracy of the full suite of hydrographic data and that a continuation of repeated surveys is a critical component of future carbon cycle monitoring.

Bolbometopon muricatum are ecologically unique mega-consumers in coral reef ecosystems. They primarily divide their dietary intake between living scleractinian corals and coral rock, a substrate richly colonized by non-coral biota. Here we examine how the chemical, structural, and energetic content of these two main classes of forage material may influence B. muricatum feeding behavior and selectivity. We then also examine nutrient content, pH, and alkalinity of the carbonate-rich feces of B. muricatum as a step toward understanding how B. muricatum defecation could affect reef nutrient dynamics and localized seawater chemistry. Our results suggest that by most measures, coral rock constitutes a richer food source than living corals, exhibiting higher levels of eight biologically relevant elements, and containing approximately three times greater caloric value than living corals. Additionally, the two forage types also presented distinct mineralogy, with the coral rock resembling a Mg-enriched carbonate phase in contrast to the primarily aragonitic live corals. Despite the fact that individual B. muricatum excrete tons of macerated coral annually, the low measured concentrations of N and P in feces suggest that this excretion may have relatively minor effects of reef macronutrient budgets. We also observed negligible local-scale impacts of B. muricatum feces on seawater pH and alkalinity. The approaches applied here integrate perspectives from marine biogeochemistry, materials science, and ecology. Collectively, these results provide preliminary insight into how reef chemistry could shape foraging of this dominant and vulnerable coral reef consumer and how it, in turn, might affect the chemistry of these reefs.

Data from GEOTRACES cruises GN01 (HLY1502) and GN04 (PS94) have been archived at the Biological & Chemical Oceanography Data Management Office (BCO-DMO; https://www.bco-dmo.org/deployment/638807) and PANGAEA (https://www.pangaea.de/?q=PS94&f.campaign%5B%5D=PS94) websites, respectively. The inorganic carbon data are available at the NOAA Ocean Carbon Data System (OCADS ; doi :10.3334/CDIAC/OTG.CLIVAR_ARC01_33HQ20150809). In addition to these national data archives, the data used in this paper is available as a supplementary downloadable excel file; International audience; A major surface circulation feature of the Arctic Ocean is the Transpolar Drift (TPD), a current that transports river‐influenced shelf water from the Laptev and East Siberian Seas toward the center of the basin and Fram Strait. In 2015, the international GEOTRACES program included a high‐resolution pan‐Arctic survey of carbon, nutrients, and a suite of trace elements and isotopes (TEIs). The cruises bisected the TPD at two locations in the central basin, which were defined by maxima in meteoric water and dissolved organic carbon concentrations that spanned 600 km horizontally and ~25‐50 m vertically. Dissolved TEIs such as Fe, Co, Ni, Cu, Hg, Nd, and Th, which are generally particle‐reactive but can be complexed by organic matter, were observed at concentrations much higher than expected for the open ocean setting. Other trace element concentrations such as Al, V, Ga, and Pb were lower than expected due to scavenging over the productive East Siberian and Laptev shelf seas. Using a combination of radionuclide tracers and ice drift modeling, the transport rate for the core of the TPD was estimated at 0.9 ± 0.4 Sv (106 m3 s‐1). This rate was used to derive the mass flux for TEIs that were enriched in the TPD, revealing the importance of lateral transport in supplying materials beneath the ice to the central Arctic Ocean and potentially to the North Atlantic Ocean via Fram Strait. Continued intensification of the Arctic hydrologic cycle and permafrost degradation will likely lead to an increase in the flux of TEIs into the Arctic Ocean.

Highly accurate and precise measurements of the inorganic carbon system are crucial for monitoring and assessing the uptake of anthropogenic CO2 by the ocean. The Arctic Ocean is an area of particular interest due to Arctic amplification of climate change. Internally consistent constants are essential for making high quality CO2 system measurements and for calculating the full suite of carbon parameters. Temperatures and salinities in the Arctic are near or below the valid ranges of most carbon system constants, but the applicability has never been fully assessed in the Arctic. Using measurements of all four carbon parameters (total alkalinity, total CO2, pH, and pCO2) made on the Arctic GEOTRACES/GO-SHIP cruise in summer 2015, we evaluate the internal consistency of six different sets of constants for surface waters at in situ temperature. Five of the six sets of constants are generally internally consistent, but each is statistically significantly different from each other. Although differences among constants are generally within the uncertainty of the calculations, these results indicate caution should be used when comparing data using different constants as biases may result from the choice of constants. We also find significant uncertainty in converting measured pH to pH at in situ temperature. The uncertainty in the pH temperature conversion limits our ability to determine the accuracy of pH measurements, particularly in polar regions. Measurements in marginal ice zones indicate that dissolution of semi-stable ikaite (CaCO3) may bias total alkalinity measurements, and should therefore be analyzed immediately upon collection or filtered before storage.

This work demonstrates how large-scale Aquarius satellite salinity data have provided an unprecedented opportunity when combined with total alkalinity (TA) equations as a function of salinity and temperature to examine global changes in the CO2 system. Alkalinity is a gauge on the ability of seawater to neutralize acids. TA correlates strongly with salinity. Spatial variability in alkalinity and salinity exceed temporal variability. Northern Hemisphere has more spatial variability in TA and salinity, while less variability in Southern Ocean TA is due to less salinity variability and upwelling of waters enriched in alkalinity. For the first time it is shown that TA in subtropical regions has increased as compared with climatological data; this is reflective of large-scale changes in the global water cycle. Thus, as temperature and salinity increase in subtropical regions, the resultant increase in TA and ocean acidification is reinforcing that from oceanic uptake of atmospheric CO2.

The Surface Ocean CO2 Atlas (SOCAT) is a synthesis of quality-controlled fCO2 (fugacity of carbon dioxide) values for the global surface oceans and coastal seas with regular updates. Version 3 of SOCAT has 14.7 million fCO2 values from 3646 data sets covering the years 1957 to 2014. This latest version has an additional 4.6 million fCO2 values relative to version 2 and extends the record from 2011 to 2014. Version 3 also significantly increases the data availability for 2005 to 2013. SOCAT has an average of approximately 1.2 million surface water fCO2 values per year for the years 2006 to 2012. Quality and documentation of the data has improved. A new feature is the data set quality control (QC) flag of E for data from alternative sensors and platforms. The accuracy of surface water fCO2 has been defined for all data set QC flags. Automated range checking has been carried out for all data sets during their upload into SOCAT. The upgrade of the interactive Data Set Viewer (previously known as the Cruise Data Viewer) allows better interrogation of the SOCAT data collection and rapid creation of high-quality figures for scientific presentations. Automated data upload has been launched for version 4 and will enable more frequent SOCAT releases in the future. High-profile scientific applications of SOCAT include quantification of the ocean sink for atmospheric carbon dioxide and its long-term variation, detection of ocean acidification, as well as evaluation of coupled-climate and ocean-only biogeochemical models. Users of SOCAT data products are urged to acknowledge the contribution of data providers, as stated in the SOCAT Fair Data Use Statement. This ESSD (Earth System Science Data) "living data" publication documents the methods and data sets used for the assembly of this new version of the SOCAT data collection and compares these with those used for earlier versions of the data collection (Pfeil et al., 2013; Sabine et al., 2013; Bakker et al., 2014). Individual data set files, included in the synthesis product, can be downloaded here: doi:10.1594/PANGAEA.849770. The gridded products are available here: doi:10.3334/CDIAC/OTG.SOCAT_V3_GRID.

The interaction between the redox chemistry of Fe and Cu at nanomolar has been studied in UV-treated seawater. The oxidation of Fe(II) was studied as a function of concentrations of Cu(II) and Cu(I) from 0 to 200 nM. The effect of added H 2 O 2 (0–500 nM), pH (6.0–8.5) and NaHCO 3 (2–9 mM) on the Fe(II) rate constants was studied at Cu(II) levels (0–200 nM). To understand the competition between Fe and Cu, the reduction of Cu(II) to Cu(I) was also studied as a function of oxygen (air-saturated and anoxic seawater), Fe(II) (0–200 nM) and H 2 O 2 (0–300 nM). The Fe(II) oxidation was accelerated by the presence of Cu(II) and Cu(I). This acceleration has been explained by the redox coupling between Fe and Cu, competition for different inorganic species (hydroxyl and carbonate groups studied independently) and by the formation of Fe–Cu particles (cupric or cuprous ferrite). Superoxide played a key role in the oxidation rate of Fe(II) in the presence of Cu(II). The presence of Fe(II) caused a greater reduction of Cu(II) to Cu(I). This is directly related to the levels of oxygen, Fe(II) and H 2 O 2 concentrations. The presence of Fe(II) produced a rapid formation of Cu(I) in the first 2–3 min of reaction. The Cu(I) is oxidized reaching a steady-state around 20 nM levels of Cu(I). These experimental results demonstrated that the presence of Fe and Cu strongly affected the inorganic redox chemistry of both metals in UV-treated seawater.

The extended multilinear regression method is used to determine the uptake and storage of anthropogenic carbon in the Atlantic Ocean based on repeat occupations of four cruises from 1989 to 2014 (A16, A20, A22, and A10), with an emphasis on the 2003–2014 period. The results show a significant increase in basin-wide anthropogenic carbon storage in the North Atlantic, which absorbed 4.4 ± 0.9 Pg C decade−1 from 2003 to 2014 compared to 1.9 ± 0.4 Pg C decade−1 for the 1989–2003 period. This decadal variability is attributed to changing ventilation patterns associated with the North Atlantic Oscillation and increasing release of anthropogenic carbon into the atmosphere. There are small changes in the uptake rate of CO2 in the South Atlantic for these time periods (3.7 ± 0.8 Pg C decade−1 versus 3.2 ± 0.7 Pg C decade−1). Several eddies are identified containing ~20% more anthropogenic carbon than the surrounding waters in the South Atlantic demonstrating the importance of eddies in transporting anthropogenic carbon. The uptake of carbon results in a decrease in pH of ~0.0021 ± 0.0007 year−1 for surface waters during the last 10 years, in line with the atmospheric increase in CO2.

The International Thermodynamic Equation of Seawater – 2010 has defined the thermodynamic properties of seawater in terms of a new salinity variable, Absolute Salinity, which takes into account the spatial variation of the composition of seawater. Absolute Salinity more accurately reflects the effects of the dissolved material in seawater on the thermodynamic properties (particularly density) than does Practical Salinity. When a seawater sample has standard composition (i.e. the ratios of the constituents of sea salt are the same as those of surface water of the North Atlantic), Practical Salinity can be used to accurately evaluate the thermodynamic properties of seawater. When seawater is not of standard composition, Practical Salinity alone is not sufficient and the Absolute Salinity Anomaly needs to be estimated; this anomaly is as large as 0.025 g kg−1 in the northernmost North Pacific. Here we provide an algorithm for estimating Absolute Salinity Anomaly for any location (x, y, p) in the world ocean. To develop this algorithm, we used the Absolute Salinity Anomaly that is found by comparing the density calculated from Practical Salinity to the density measured in the laboratory. These estimates of Absolute Salinity Anomaly however are limited to the number of available observations (namely 811). In order to provide a practical method that can be used at any location in the world ocean, we take advantage of approximate relationships between Absolute Salinity Anomaly and silicate concentrations (which are available globally).

The apparent molal volumes and compressibilities of Tris and Tris–HCl have been determined in water (5–45 °C) and 0.725 m NaCl (5–25 °C). The changes in the volume (Δ V ) and compressibility (Δ κ ) for the dissociation of Tris–H + Tris - H + = Tris + H + as functions of temperature in water and 0.725 m NaCl have been determined from these measurements. The values of Δ V and Δ κ have been used to determine the effect of pressure on the dissociation constant for Tris–H + ( K P / K 0 ). ln ( K P / K 0 ) = - ∆ V / ( R T ) P + 0 .5∆ k / ( R T ) P 2 These results will be useful in the calibration of pH systems making in-situ measurements at high pressure in seawater. In 0.725 m NaCl at 5 °C and a pressure of 2000 bar, the dissociation constant is reduced by 29%.

The partial molal volumes and compressibilities of a number of nonelectrolytes and amino acids in 0.725 m NaCl have been determined from density and compressibility measurements. The results have been used to examine the behavior of these compounds in ocean waters. The partial molal volumes of the solutes in 0.725 m NaCl were a linear function of the values in water. The partial molal compressibilities of urea, sugars and amino acids were all negative due to the hydration of water molecules. The values of partial molal compressibilities in 0.725 m NaCl were not as negative due to the decrease in the hydration in the salt solution. A simple hydration model is used to estimate the number of water molecules hydrated to the solutes in 0.725 m NaCl. The partial molal volumes and compressibilities for the nonelectrolytes determined in this study should be useful in estimating the effect of pressure on equilibrium reactions of these compounds in seawater.

Seasonal variability of the aragonite saturation state (ΩAR) in the upper (50 m and 100 m depths) North Pacific Ocean (NPO) was investigated using multiple linear regression (MLR). The MLR algorithm derived from a high-quality carbon data set accurately predicted the ΩAR of evaluation data sets (three time series stations and P02 section) with acceptable uncertainty (

A modified version of the extended multiple linear regression (eMLR) method is used to estimate anthropogenic carbon concentration (Canth) changes along the Pacific P02 and P16 hydrographic sections over the past two decades. P02 is a zonal section crossing the North Pacific at 30°N, and P16 is a meridional section crossing the North and South Pacific at ~150°W. The eMLR modifications allow the uncertainties associated with choices of regression parameters to be both resolved and reduced. Canth is found to have increased throughout the water column from the surface to ~1000 m depth along both lines in both decades. Mean column Canth inventory increased consistently during the earlier (1990s–2000s) and recent (2000s–2010s) decades along P02, at rates of 0.53 ± 0.11 and 0.46 ± 0.11 mol C m−2 a−1, respectively. By contrast, Canth storage accelerated from 0.29 ± 0.10 to 0.45 ± 0.11 mol C m−2 a−1 along P16. Shifts in water mass distributions are ruled out as a potential cause of this increase, which is instead attributed to recent increases in the ventilation of the South Pacific Subtropical Cell. Decadal changes along P16 are extrapolated across the gyre to estimate a Pacific Basin average storage between 60°S and 60°N of 6.1 ± 1.5 PgC decade−1 in the earlier decade and 8.8 ± 2.2 PgC decade−1 in the recent decade. This storage estimate is large despite the shallow Pacific Canth penetration due to the large volume of the Pacific Ocean. By 2014, Canth storage had changed Pacific surface seawater pH by −0.08 to −0.14 and aragonite saturation state by −0.57 to −0.82.

The practical ( S p ) and reference ( S R ) salinities do not account for variations in physical properties such as density and enthalpy. Trace and minor components of seawater, such as nutrients or inorganic carbon affect these properties. This limitation has been recognized and several studies have been made to estimate the effect of these compositional changes on the conductivity–density relationship. These studies have been limited in number and geographic scope. Here, we combine the measurements of previous studies with new measurements for a total of 2857 conductivity–density measurements, covering all of the world׳s major oceans, to derive empirical equations for the effect of silica and total alkalinity on the density and absolute salinity of the global oceans and to recommend an equation applicable to most of the world׳s oceans. The potential impact on salinity as a result of uptake of anthropogenic CO 2 is also discussed.

The Pitzer equations have been shown to be very useful in estimating the physical chemical properties of mixed electrolyte solutions like seawater. The equations account for all the ionic interactions occurring in a mixed electrolyte solution. In this paper, the Pitzer equations have been used to estimate the partial molar volumes of ions in 0.725 mol·kg−1 NaCl, which is a near equivalent for average seawater of absolute salinity S A = 35.165 g·kg−1. The calculated results at 25 °C for a number of cations and anions are in good agreement with the measured values in 0.725 mol·kg−1 NaCl. The estimates in seawater are limited, due to the scarcity of volume data for metal sulfate and bicarbonate salts. The model can now be used to make reasonable estimates of the effect of pressure on equilibria in the oceans and other mixed electrolyte solutions over a wide range of composition, at 25 °C, and for some of the major sea salts and the rare earth cations from 0 to 100 °C.

The Pitzer equations have been used to fit the apparent molal adiabatic compressibility of electrolytes in water as a function of temperature. The equations have been used to estimate the partial molal compressibility for a number of cations and anions in 0.725 m NaCl and average seawater (S = 35 g kg–1). The calculated results for electrolytes are in good agreement with direct measurements in 0.725 m NaCl and seawater. The partial molal compressibilities estimated from the model can be used to make more reliable estimates of the effect of pressure on activity coefficients and ionic equilibria in seawater and other mixed electrolyte solutions at high pressures.

The apparent molal volumes (Vϕ) of the trivalent rare earth (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) chlorides, nitrates and perchlorates have been calculated from the density measurements at 25 °C and (5 to 80) °C and 0.02 – 4 m. The values of Vϕ have been fitted to the Pitzer equations, Vϕ = V0 + (AvI/(1.2m) ln(1 + 1.2I0.5) + 2RTm(βV(0) + βV(1) g(y) + mCV), where V0 is the infinite dilution partial molal volume, Av is the Debye- Huckel slope, I is the ionic strength, and g(y) = (2/y2)·[1 – (1 + y) exp(−y)] where y = 2(I0.5). The Pitzer volume parameters βV(0), βV(1) and CV are functions of temperature. The values of V0, βV(0), βV(1), and CV for most of the rare earth chlorides are similar orders of magnitude. These results should be useful in estimating the effect of pressure on the equilibria of rare earths in natural waters over a wide range of temperature.

The speciation of lead in the environment is extremely important in determining its behavior and fate in natural waters. Speciation calculations rely on accurate formation constants, which are often scarce. The constants for Lead Chloride complexes are fairly well known in a wide variety of media, but lead carbonate values are rare and somewhat uncertain. We determined the stoichiometric formation constant (β PbCO3 ) of lead carbonate in NaCl solutions from 0.05 to 3.0 m at 25 °C. The thermodynamic formation constant (K PbCO3 ) was obtained using a Pitzer model (logK PbCO3 = 6.87 ± 0.09). The known thermodynamic and stoichiometric formation constants of PbCl n 2-n in HCl, NaCl, NaClO 4 , MgCl 2 and CaCl 2 , published PbCO 3 values in NaClO 4 , and our new PbCO 3 values in NaCl are fit to a Pitzer model to determine the Pitzer coefficients for PbCl + , PbCl 2 , PbCl 3 - , and PbCO 3 . Using this model the speciation of lead can be determined in a wide variety of media relevant to natural waters, including brines and seawater. Calculations of seawater speciation show general agreement with previously published estimates.

Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics, and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates and consistency within and among components, alongside methodology and data limitations. CO2 emissions from fossil fuels and industry (EFF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (ELUC), mainly deforestation, are based on combined evidence from land-cover change data, fire activity associated with deforestation, and models. The global atmospheric CO2 concentration is measured directly and its rate of growth (GATM) is computed from the annual changes in concentration. The mean ocean CO2 sink (SOCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The variability in SOCEAN is evaluated with data products based on surveys of ocean CO2 measurements. The global residual terrestrial CO2 sink (SLAND) is estimated by the difference of the other terms of the global carbon budget and compared to results of independent dynamic global vegetation models. We compare the mean land and ocean fluxes and their variability to estimates from three atmospheric inverse methods for three broad latitude bands. All uncertainties are reported as ±1σ, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (2006–2015), EFF was 9.3 ± 0.5 GtC yr−1, ELUC 1.0 ± 0.5 GtC yr−1, GATM 4.5 ± 0.1 GtC yr−1, SOCEAN 2.6 ± 0.5 GtC yr−1, and SLAND 3.1 ± 0.9 GtC yr−1. For year 2015 alone, the growth in EFF was approximately zero and emissions remained at 9.9 ± 0.5 GtC yr−1, showing a slowdown in growth of these emissions compared to the average growth of 1.8 % yr−1 that took place during 2006–2015. Also, for 2015, ELUC was 1.3 ± 0.5 GtC yr−1, GATM was 6.3 ± 0.2 GtC yr−1, SOCEAN was 3.0 ± 0.5 GtC yr−1, and SLAND was 1.9 ± 0.9 GtC yr−1. GATM was higher in 2015 compared to the past decade (2006–2015), reflecting a smaller SLAND for that year. The global atmospheric CO2 concentration reached 399.4 ± 0.1 ppm averaged over 2015. For 2016, preliminary data indicate the continuation of low growth in EFF with +0.2 % (range of −1.0 to +1.8 %) based on national emissions projections for China and USA, and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. In spite of the low growth of EFF in 2016, the growth rate in atmospheric CO2 concentration is expected to be relatively high because of the persistence of the smaller residual terrestrial sink (SLAND) in response to El Niño conditions of 2015–2016. From this projection of EFF and assumed constant ELUC for 2016, cumulative emissions of CO2 will reach 565 ± 55 GtC (2075 ± 205 GtCO2) for 1870–2016, about 75 % from EFF and 25 % from ELUC. This living data update documents changes in the methods and data sets used in this new carbon budget compared with previous publications of this data set (Le Quéré et al., 2015b, a, 2014, 2013). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi:10.3334/CDIAC/GCP_2016).

The Surface Ocean CO2 Atlas (SOCAT) is a synthesis of quality-controlled fCO2 (fugacity of carbon dioxide) values for the global surface oceans and coastal seas with regular updates. Version 3 of SOCAT has 14.5 million fCO2 values from 3646 data sets covering the years 1957 to 2014. This latest version has an additional 4.4 million fCO2 values relative to version 2 and extends the record from 2011 to 2014. Version 3 also significantly increases the data availability for 2005 to 2013. SOCAT has an average of approximately 1.2 million surface water fCO2 values per year for the years 2006 to 2012. Quality and documentation of the data has improved. A new feature is the data set quality control (QC) flag of E for data from alternative sensors and platforms. The accuracy of surface water fCO2 has been defined for all data set QC flags. Automated range checking has been carried out for all data sets during their upload into SOCAT. The upgrade of the interactive Data Set Viewer (previously known as the Cruise Data Viewer) allows better interrogation of the SOCAT data collection and rapid creation of high-quality figures for scientific presentations. Automated data upload has been launched for version 4 and will enable more frequent SOCAT releases in the future. High-profile scientific applications of SOCAT include quantification of the ocean sink for atmospheric carbon dioxide and its long-term variation, detection of ocean acidification, as well as evaluation of coupled-climate and ocean-only biogeochemical models. Users of SOCAT data products are urged to acknowledge the contribution of data providers, as stated in the SOCAT Fair Data Use Statement. This ESSD (Earth System Science Data) "Living Data" publication documents the methods and data sets used for the assembly of this new version of the SOCAT data collection and compares these with those used for earlier versions of the data collection (Pfeil et al., 2013; Sabine et al., 2013; Bakker et al., 2014).

The density and compressibility of seawater solutions from 0 to 95 °C have been examined using the Pitzer equations. The apparent molal volumes (X = V) and compressibilities (X = κ) are in the form $$ X_{\phi } = \bar{X}^{0} + A_{X} I/(1.2 \, m)\ln (1 + 1.2 \, I^{0.5} ) + \, 2{\text{RT }}m \, (\beta^{(0)X} + \beta^{(1)X} g(y) + C^{X} m) $$ where $$ \bar{X}^{0} $$ is the partial molal volume or compressibility, I is the ionic strength, m is the molality of sea salt, AX is the Debye–Huckel slope for volume (X = V) or adiabatic compressibility (X = κ s), and g(y) = (2/y 2)[1 − (1 + y) exp(−y)] where y = 2I 0.5. The values of the partial molal volume and compressibility ( $$ \bar{X}^{0} $$ ) and Pitzer parameters (β (0)X , β (1)X and C X ) are functions of temperature in the form $$ Y^{X} = \sum_{i} a_{i} (T-T_{\text{R}} )^{i} $$ where a i are adjustable parameters, T is the absolute temperature in Kelvin, and T R = 298.15 K is the reference temperature. The standard errors of the seawater fits for the specific volumes and adiabatic compressibilities are 5.35E−06 cm3 g−1 and 1.0E−09 bar−1, respectively. These equations can be combined with similar equations for the osmotic coefficient, enthalpy and heat capacity to define the thermodynamic properties of sea salt to high temperatures at one atm. The Pitzer equations for the major components of seawater have been used to estimate the density and compressibility of seawater to 95 °C. The results are in reasonable agreement with the measured values (0.010E−03 g cm−3 for density and 0.050E−06 bar−1 for compressibility) from 0 to 80 °C and salinities from 0 to 45 g kg−1. The results make it possible to estimate the density and compressibility of all natural waters of known composition over a wide range of temperature and salinity.

The sound speeds of boric acid and sodium borate in water and 0.725 m NaCl have been measured from 0 to 50 °C and to near 1 molal. These results have been used to determine the partial molal adiabatic compressibilities of B(OH)3 and NaB(OH)4. The partial molal volumes, v ¯ ( i ) , and compressibilities, κ ¯ ( i ) , have been used to estimate the changes in the volume (ΔV) and compressibility (Δκ) for the dissociation of boric acid in water and average seawater (0.725 m NaCl, SA ∼ 35 g/kg) B ( OH ) 3 + H 2 O = H + + B ( OH ) 4 - where Δ V = v ¯ ( H + ) + v ¯ ( B ( OH ) 4 - ) - v ¯ ( H 2 O ) - v ¯ ( B ( OH ) 3 ) Δ κ = κ ¯ ( H + ) + κ ¯ ( B ( OH ) 4 - ) - κ ¯ ( H 2 O ) - κ ¯ ( B ( OH ) 3 ) The calculated values of ΔV and Δκ were used to estimate the effect of applied pressure (P) on the dissociation constants (KP/K0) ln ( K P / K 0 ) = - Δ V P / RT + 0.5 Δ κ P 2 / RT The new values of Δκ in water from 0 to 1000 bar give values of KP/K0 that are in good agreement with the measured values. The values of KP/K0 at P = 1942 bar in water are slightly higher than the measured values. The new calculated values of KP/ K0 in seawater from 0 to 25 °C and to P = 1000 bar are in good agreement with the measured values. This means that the contributions of boric acid to the alkalinity of seawater in deep waters are not affected by the new values of KP/K0 determined from volume studies.

An important property of aqueous solutions is pH because it affects chemical and biochemical properties such as chemical reactions, equilibrium conditions, and biological toxicity. With the increasing uptake of fossil fuel CO 2 into the oceans, a decrease in pH is important to consider at this time. Unfortunately, many different methods for assessing pH have been used by different groups. The objectives of this review were to (1) briefly examine the concept of pH as it was introduced and developed, up to the current scientific developments, assumptions, and recommendations, (2) critically assess the various approaches that different scientific groups have adopted for pH, balancing their preferences and arguments, (3) compare measuring vs. modeling pH, and (4) issue recommendations on an optimized approach or approaches for pH. The main conclusions of this review are: (1) pH definitions and conventions are highly variable, which leads to highly variable estimates of pH. For example, for seawater at S A = 35.165 g/(kg soln), t = 25 °C, P = 1.0 atm, and fCO 2 = 3.33E-4 atm, model calculated pH values varied from 8.08 to 8.33 on the various pH scales; (2) An acceptable nomenclature is needed to keep pH variability unambiguous, due to alternative definitions and conventions. A nomenclature example is given in this paper. It is the (still unsolved) task of international bodies such as IUPAC or IOC to develop and promote such widely recognized conventions; (3) pH can be accurately estimated based on measurement (potentiometric, spectrophotometric) and modeling approaches. Accuracy via different definitions and conventions clearly requires consistency with respect to experimental measurements, equilibrium constants, activity coefficients, and buffer solutions that are used for specific approaches; (4) “Total” pH accuracy that includes the Bates–Guggenheim convention is ± 0.01 pH units. Removing the Bates–Guggenheim convention from the accuracy calculation can lead to “conventional” accuracies of ± 0.004 pH units; (5) pH extensions to high solution concentrations are capable using the Pitzer modeling approach. Modeling can, in principle, lead to pH estimates that are more accurate than measurements, which is illustrated with two Pitzer models for natural waters made up of the major components of seawater. But this principle still needs to be proven; (6) It is recommended that ocean scientists use the free concentration or activity of the proton to examine the effect of pH on processes in the oceans.

Measurements on the speed of sound (U) in seawater as a function of salinity at 1 atm (P = 0 bar applied pressure) have been measured from 25 to 95 °C. The new measurements have been combined with the earlier studies to determine the adiabatic compressibility (βS = −(1/ρ)(∂ρ/∂P)S) of seawater from 0 to 95 °C β S = 1 / ρU 2 where ρ is the density and S is the entropy of seawater. The isothermal compressibility of seawater were determined from β T = β S α 2 T / ρCp where the thermal expansively, α = −(1/ρ)(∂ρ/∂T)P and heat capacity (Cp) were determine from earlier measurements. The values of the isothermal compressibility at 1 atm (βT0) have been used to estimate the effect of pressure on the secant bulk modulus of seawater (KP at applied pressure P) K P = v 0 P / v 0 – v P = K 0 + A P + B P 2 where the specific volume v = 1/ρ and K0 = 1/(βT0). The values of A and B at high pressures have been determined from literature high pressure measurements. This allows one to make reasonable estimates of the density of seawater as a function of pressure to 100 °C when seawater is used as a cooling agent and for desalination (Feistel, 2010).

Great Salt Lake (GSL) is one of the largest and most saline lakes in the world. In order to accurately model limnological processes in GSL, hydrodynamic calculations require the precise estimation of water density (ρ) under a variety of environmental conditions. An equation of state was developed with water samples collected from GSL to estimate density as a function of salinity and water temperature. The ρ of water samples from the south arm of GSL was measured as a function of temperature ranging from 278 to 323 degrees Kelvin (oK) and conductivity salinities ranging from 23 to 182 g L−1 using an Anton Paar density meter. These results have been used to develop the following equation of state for GSL (σ = ± 0.32 kg m−3): $$ \rho - \rho^{0} = { 184}.0 10 6 2 { } + { 1}.0 4 70 8*{\text{S}} - 1. 2 10 6 1*{\text{T }} + { 3}. 1 4 7 2 1 {\text{E}} - 4*{\text{S}}^{ 2} + \, 0.00 1 9 9 {\text{T}}^{ 2} - 0.00 1 1 2*{\text{S}}*{\text{T}}, $$ where ρ 0 is the density of pure water in kg m−3, S is conductivity salinity g L−1, and T is water temperature in degrees Kelvin.

As seawater circulates through the global ocean, its relative composition undergoes small variations. This results in changes to the conductivity/salinity/density relationship, which is currently well-defined only for Standard Seawater obtained from a particular area in the North Atlantic. These changes are investigated here by analysis of laboratory experiments in which salts are added to seawater, by analysis of oceanic observations of density and composition anomalies, and by mathematical investigation using a model relating composition, conductivity, and density of arbitrary seawaters. Mathematical analysis shows that understanding and describing the effect of changes in relative composition on operational estimates of salinity using the Practical Salinity Scale 1978 and on density using an equation of state for Standard Seawater require the use of a number of different salinity variables and a family of haline contraction coefficients. These salinity variables include an absolute Salinity SAsoln, a density salinity SAdens, the reference salinity SR, and an added-mass salinity SAadd. In addition, a new salinity variable S∗ is defined, which represents the preformed salinity of a Standard Seawater component of real seawater to which biogeochemical processes add material. In spite of this complexity, observed correlations between different ocean biogeochemical processes allow the creation of simple formulas that can be used to convert between the different salinity and density measures, allowing for the operational reduction of routine oceanographic observations.

The effect of pressure ( P ) on the activity coefficients ( γ i P / γ i 0 ) of ions ( i ) in seawater can be estimated from the partial molal volumes and compressibilities of the ions in water ( V ¯ 0 and κ ¯ 0 ) and seawater ( V ¯ ⁎ and κ ¯ ⁎ ) ln ( γ P / γ 0 ) = ( V ¯ ⁎ − V ¯ 0 ) P / R T − 0. 5 ( κ ¯ ⁎ − κ ¯ 0 ) P 2 / R T where R and T have their normal meaning. One can also use the partial molal volumes and compressibilities of ions to estimate the effect of pressure ( K P / K 0 ) on ionic equilibria constants M 2 + + X 2 − = MX , K = [ MX ] / [ M 2 + ] [ X 2 − ] from the changes in the volume for the chemical reaction in seawater Δ V ⁎ = V ¯ ⁎ ( MX ) − V ¯ ⁎ ( M 2 + ) − V ¯ ⁎ ( X 2 − ) , Δ κ ⁎ = κ ¯ ⁎ ( MX ) − κ ¯ ⁎ ( M 2 + ) − κ ¯ ⁎ ( X 2 − ) using ln ( K ⁎ P / K ⁎ 0 ) = ( Δ V ⁎ / R T ) P − 0. 5 ( Δ κ ⁎ / R T ) P 2 The densities and sound speeds of a number of transition metal chlorides have been determined in 0.725 m NaCl solutions (the ionic strength of average seawater, S ∼35) at 25 °C. These results have been used to determine the partial molal volumes and compressibilities of transition metal ions (Mn 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ and Cd 2+ ). These results and our earlier measurements (Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ ) were used to develop correlations between the values in water and NaCl. These correlations were used to predict the values of other divalent ions in water and NaCl (Be 2+ , Pb 2+ , Hg 2+ and Fe 2+ ) that were difficult to directly measure. These studies allow one to make estimates of the effect of pressure on the activity coefficients of these ions in seawater and ionic equilibria in the deep oceans. The lower stability constants will result in increased concentrations of free transition metals in the deep ocean.

The oxidation of organosulfur compounds requires the transfer of oxygen atoms and is important in decontamination of chemical warfare agents, desulfurization of fossil fuel for high quality, deodorization of wastewater and sludge, and remediation of industrial effluents. The kinetics of the oxidation of organosulfur compounds (sulfur-containing amino acids, aliphatic and aromatic thiols, and mercaptans) by the environmentally-friendly oxidant, ferrate(VI) FeO(4)(2-), was quantitatively examined in this study using a kinetic model considering possible reactions among the species of ferrate(VI) and organosulfur compounds. The ratios of ferrate(VI) to the various organosulfur compounds for the one oxygen-atom transfer were 0.50 and 0.67 for Fe(II) and Fe(III) as final products, respectively. The second-order rate constants for the oxidation of organosulfur compounds by protonated ferrate(VI) HFeO(4)(-) ion were correlated with thermodynamic 1-e(-) and 2-e(-) reduction potentials in order to understand the mechanisms of the reactions. The oxidation of the compounds involved a 1-e(-) transfer step from Fe(VI) to Fe(V), followed by 2-e(-) transfer to Fe(III) as the reduced product (Fe(VI)→Fe(V)→Fe(III)). The 2-e(-) transfer steps resulted in the formation of Fe(II) (Fe(VI)→Fe(IV)→Fe(II)). Conclusions drawn from the correlations are consistent with the experimentally determined stoichiometries and products of the reactions. The calculated half-lives for the oxidation were in the range of ms to s at a dose of 10mg K(2)FeO(4)L(-1) and hence ferrate(VI) has a great potential in treating organosulfur compounds present in water and wastewater.

At constant temperature, the density of deep waters in the oceans is higher than that of surface waters due to the oxidation of plant material that adds NO3, PO4, and Si(OH)4, and the dissolution of CaCO3(s) that adds Ca2+ and HCO3. These increases in the density have been used to estimate the absolute salinity of seawater that is needed to determine its thermodynamic properties. Density (ρ), total alkalinity (TA), and dissolved organic carbon (DOC) measurements were taken on waters collected in the eastern Arctic Ocean. The results were examined relative to the properties of North Atlantic Waters. The excess densities (Δρ = ρMeas − ρCalc) in the surface Arctic waters were higher than expected (maximum of 0.008 kg m−3) when compared to Standard Seawater. This excess is due to the higher values of the normalized total alkalinity (NTA = TA * 35/S) (up to ~2,650 μmol kg−1) and DOC (up to ~130 μmol kg−1) resulting from river water input. New measurements are needed to determine how the DOC in the river waters contributes to the TA of the surface waters. The values of Δρ in deep waters are slightly lower (−0.004 ± 0.002 kg m−3) than that in Standard Seawater. The deep waters in the Arctic Ocean, unlike the Atlantic, Pacific, Indian, and Southern Oceans, do not have significant concentrations of silicate (maximum ~15 μmol kg−1) and that can affect the densities. Since the NTA of the deep Arctic waters (2,305 ± 6 μmol kg−1) is the same as Standard Seawater (2,306 ± 3 μmol kg−1), the decrease in the density may be caused by the lower concentrations of DOC in the deep waters (44–50 μmol kg−1 compared to the Standard Seawater value of 57 ± 2 μmol kg−1). The relative deficit of DOC (7–13 μmol kg−1) in the deep Arctic waters appears to cause the lower densities (−0.004 kg m−3) and Absolute Salinities (S A, −0.004 g kg−1). The effect of increases or decreases in Δρ and δS A due to DOC in other deep ocean waters may be hidden in the correlations of the changes with silicate. Further work is needed to separate the effects of SiO2 and DOC on the density of deep waters of the world oceans.

To model chemically stratified lakes numerically, chemical transformations must be reflected in the density function. In this contribution, partial molal volumes are used to calculate density from the chemical composition of lake water. Such values have been evaluated for cations and anions separately, to facilitate an easy implementation into geochemical stratification models for lakes. Coefficients for temperature dependence and variation for higher ionic strengths were evaluated from previously published data. An algorithm RHOMV to calculate density with a second order approximation for temperature dependence and ionic strength dependence is proposed. The accuracy is tested for seawater composition. We conclude that this approach delivers a representation of density based on the actual chemical composition of the lake water, which is accurate enough for most limnological purposes. The implementation of RHOMV into geochemical stratification models facilitates the numerical tackling of pressing questions, such as meromixis or double diffusive features or altered circulation patterns of lakes due to changing climate or change of use.

The burning of fossil fuels has increased the concentration of carbon dioxide (CO2) in the atmosphere from 280 ppmv (volume parts per million) to 385 ppmv over the last 200 years. This increase is larger than has occurred over the past 800,000 years. Equilibration of increasing amounts of CO2 with surface waters will decrease the pH of the oceans (called ocean acidification ) from a current value of 8.1 to values as low as 7.4 over the next 200 years. Decreasing the pH affects the production of solid CaCO3 by microorganisms in surface waters and its subsequent dissolution. CO2 dissolution in the ocean can also affect acid–base equilibria, metal complex formation, solid–liquid equilibria, and the adsorption of ions to charged surfaces. Thermodynamic principles can be used to understand these processes in natural waters.

Large quantities of African dust are carried across the North Atlantic by Trade Winds every summer. The deposition of this dust has an impact on biogeochemical processes in the Tropical and Western Atlantic Ocean and Caribbean and it contributes to the formation of soils on Caribbean islands, the Bahamas, and the southeastern US. Here we report on a study of the temporal and spatial variability of the elemental composition of aerosol samples collected in the Trade Winds at Barbados and Miami over the summers of 2003 and 2004. Our objective is to identify characteristics that might serve as a useful tool to identify natural and anthropogenic sources of specific elements or element classes placing a special focus on dust-linked species. To this end we measured a large suite of elements: Al, As, Ba, Be, Cd, Ce, Co, Cr Cs, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ho, La, Li, Lu, Nd, Ni, Pb, Pr, Rb, Sc, Sm, Sr, Th, Tl, Tm, U, V, Y, Yb and Zn. Most elements exhibited a surprising uniformity that is highly correlated with dust concentration as determined by aerosol filter ash residues and by Mn concentration, shown to be an excellent proxy for dust. The concentrations of most elements are very close to average upper crustal abundances. We measured the greatest enrichments and the largest variability for As, Cd, Cu, Cr, Ni, Pb, V, and Zn, elements known to have major anthropogenic sources. For some elements, most notably the Lanthanides, we found statistically significant differences between high-dust-load samples and low-load samples and also between individual dust peaks. However, the absolute differences were generally quite small. Consequently we feel that on a sample-by-sample basis the elemental composition of dust is unlikely to serve as useful indicator of source regions with the possible exception of the Lanthanides. The uniformity of dust composition suggests that a major fraction of the dust is either derived from regions having similar composition or from multiple different sources followed by mixing during transport.

The inorganic behavior of most divalent metals in natural waters is affected by the formation of carbonate complexes. The acidification of the oceans will lower the carbonate concentration in the oceans. This will increase the concentration of free copper that is toxic to marine organisms. To be able to determine the effect of this acidification, reliable stability constants are needed for the formation of copper carbonate complexes. In this paper, the speciation of Cu(II) with bicarbonate and carbonate ions $$\begin{array}{rcl}&&\mathrm{Cu}^{2+}+\mathrm{HCO}_{3}^{-}\rightleftharpoons \mathrm{CuCO}_{3(\mathrm{aq})}+\mathrm{H}^{+}\\[4pt]&&\mathrm{Cu}^{2+}+2\mathrm{HCO}_{3}^{-}\rightleftharpoons \mathrm{Cu}(\mathrm{CO}_{3})_{2}^{2-}+2\mathrm{H}^{+}\\[4pt]&&\mathrm{Cu}^{2+}+\mathrm{CO}_{3}^{2-}\rightleftharpoons \mathrm{CuCO}_{3(\mathrm{aq})}\\[4pt]&&\mathrm{Cu}^{2+}+2\mathrm{CO}_{3}^{2-}\rightleftharpoons \mathrm{Cu}(\mathrm{CO}_{3})_{2}^{2-}\\[4pt]&&\mathrm{Cu}^{2+}+\mathrm{HCO}_{3}^{-}\rightleftharpoons \mathrm{CuHCO}_{3}^{+}\end{array}$$ is investigated as a function of ionic strength and temperature in NaClO4 solutions.