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Papers by Ed Boyle

Deep Sea Research Part A. Oceanographic Research Papers, 1982

Trace element samples spanning the salinity range were collected in the Amazon plume in June 1974... more Trace element samples spanning the salinity range were collected in the Amazon plume in June 1974 and 1976. In 1976, laboratory mixing experiments using unfiltered fiver water and seawater were undertaken. The studies show that copper and nickel are unreactive in the Amazon plume on a time scale of a few days: in both field and laboratory studies the elements are related linearly to salinity, so that neither adsorption and precipitation nor desorpfion reactions significantly alter the net flux of these elements. The 1974 field data indicate there may be up to 25% removal of copper, probably biologically, although a conservative interpretation could be entertained ff systematic deviations from the resulting copper-salinity plot are ignored. Cadmium behavior was not clearly defined. There is some indication of desorption, and the estuarine data can be used to set an upper limit on the net flux. The net effective contribution of the elements to the ocean from the Amazon is copper, 24 nmol kg-'; nickel, 4 to 5 nmol kg-~; and cadmium, <0.1 nmol kg-'.

Deep Sea Research Part A. Oceanographic Research Papers, 1988

Mediterranean surface waters contain elevated levels of zinc and chromium and slightly lower leve... more Mediterranean surface waters contain elevated levels of zinc and chromium and slightly lower levels of vanadium compared to similar nutrient-depleted open ocean waters. A detailed mapping of surface concentrations in the Alboran Sea (immediately east of the Strait of Gibraltar) reveals that maximum total dissolvable concentrations of Zn (9.4 nmol kg t), Cr (3.9 nmol kg-1), V (35 nmol kg-1) and total Fe (53 nmol kg t) occur in the core of the Atlantic inflow jet. These distributions imply that a portion of Mediterranean trace metal enrichment occurs during passage of surface water through the coastal region and into the Strait, as observed previously for Cu and Cd. Mass balance indicates that about half of the Mediterranean Zn enrichment, and most of the Cr enrichment, is due to sources within the basin itself. High concentrations of particulate Fe in the Alboran Sea suggest eolian input or recent sediment resuspension, but in general metal sources are difficult to identify and could be fluvial or anthropogenic as well as eolian and sedimentary. Chromium and V levels in Mediterranean deep water are similar to surface water concentrations near deep-water formation regions, but Zn is enriched in deep water, implying some vertical transport by biological cycling. A simple steady-state box model indicates that about 30% of the Zn transport is particulate and that the Zn : nutrient ratio in sinking particulate matter is similar to that in open ocean particulates.

Marine Chemistry, 2015

The spatial and temporal variations of Pb were reconstructed from three corals along an east-west... more The spatial and temporal variations of Pb were reconstructed from three corals along an east-west transect of the Singapore Straitsin proximity to one of the largest emerging Asian cities and one of the world's busiest ports. In addition to establish the variation in seawater Pb concentration, sources of Pb were also investigated via Pb isotopes in seawater and corals and compared with the isotopes in local aerosols and other potential Pb sources. The annual variation of Pb in Singapore corals seems to be related to local annual precipitation while the decadalscale variation may be related to the long-term development of the region. The decrease of Pb/Ca in coral after 2005 coincided with the regional phasing out of leaded gasoline. The 206 Pb/ 207 Pb ratios in Singapore corals rose from as low as~1.166 during the 1960s to~1.189 by the late 1990s, and fluctuated between 1.180-1.198 from the late 1990s to 2010. 206 Pb/ 207 Pb in recent Singapore corals was elevated relative to Singapore atmospheric aerosols (~1.147, which is typical of urban aerosols throughout the southeastern Asian and Indonesian region). The linear distribution of 206 Pb/ 207 Pb vs. 208 Pb/ 207 Pb in triple isotope plots suggests two end-member mixing between the aerosol-Pb as a low 206 Pb/ 207 Pb end-member and an unidentified source with higher 206 Pb/ 207 Pb. Possible high 206 Pb/ 207 Pb sources include: surface runoff from imported south Chinese Pb, crustal materials from riverine inputs (sediments and suspended matter) or land reclamation, and vessels/dockyard activities.

The marine geochemical cycles of iron, copper, nickel, and cadmium were studied in order to provi... more The marine geochemical cycles of iron, copper, nickel, and cadmium were studied in order to provide a basis for oceanographic models for trace metals. Copper, nickel, and cadmium can be determined in a 100 ml seawater sample using cobalt pyrrolidine di thiocarbamate chelate coprecipi tat ion and graphite atomizer atomic absorption spectrometry. Concentration ranges likely to be encountered and estimated (10) analytical precisions are copper, 1 to 6 nanomole/kg (10.1); nickel, 3 to 12 nanomole/kg (i 0. 3); and cadmium, o. 0 to 1.1 nanomole/kg (i 0. l). The technique may be applied to freshwater samples with slight modification.-5-ACKNOWLEDGEMENT S I am grateful to John M. Edmond for being my advisor and friend and for providing a stimulating environment in which to do and learn research.

Paleoceanography, 1990

Foraminiferal Ba can be used to reconstruct the distribution of deeply regenerated chemical compo... more Foraminiferal Ba can be used to reconstruct the distribution of deeply regenerated chemical components in past oceans. The Ba contents of benthic foraminifera recovered from cores in the Atlantic Ocean indicate that waters deeper than 2900 m had •-30-60% higher Ba during the last glacial maximum (LGM). These changes are consistent with previously observed glacial nutrient enrichments based on foraminiferal Cd and •j13C. Increases in deepwater nutrient contents in the Atlantic can be explained by reductions in North Atlantic Deep Water formation during the LGM. Ba/Ca of benthic foraminifera from the glacial sections of intermediate depth Atlantic cores are equal to or lower than Holocene values. This Ba evidence argues against the Mediterranean as a greatly increased source to Atlantic intermediate waters during the LGM, since the Mediterranean is enriched in Ba today and apparently remained enriched during the LGM. Benthic foraminiferal Ba from the glacial sections of cores from the eastern equatorial Pacific suggest that deep waters of the Glacial Pacific were about 25% lower in Ba (at •-3000m). Taken together, the foraminiferal evidence indicates that the Ba content of deep waters of the Atlantic, Antarctic, and Pacific were similar at the LGM.

Journal of Geophysical Research: Oceans, 1992

Decreased consumption of leaded gasoline in the United States over the past two decades has drast... more Decreased consumption of leaded gasoline in the United States over the past two decades has drastically altered the flux and isotopic composition of Pb entering the western North Atlantic from the atmosphere. Here we exploit the resulting temporal changes in the distribution and isotopic composition of oceanic Pb to investigate interactions between dissolved and particulate Pb in the oceanic water column. Measurements of dissolved Pb isotopic composition on samples collected in 1987 in the upper water column near Bermuda demonstrate that surface water 206Pb/207Pb decreased from ∼1.203 to ∼1.192 since 1983 and that a measurable change propagated to 300–500 m since the 1984 profile of Shen and Boyle (1988). The first accurate measurements of suspended particulate Pb in an open ocean profile show concentrations of 1–3 pmol/L, equal to 2–4% of total Pb. Vertical profiles of (1) the stable lead isotopic composition and (2) the ratio of total Pb to 210Pb in suspended particles closely tra...

Global Biogeochemical Cycles, 2004

We describe a model of the ocean transport and biogeochemical cycling of iron and the subsequent ... more We describe a model of the ocean transport and biogeochemical cycling of iron and the subsequent control on export production and macronutrient distributions. Ocean transport of phosphorus and iron are represented by a highly idealized six‐box ocean model. Export production is parameterized simply; it is limited by light, phosphate, and iron availability in the surface ocean. We prescribe the regional variations in aeolian deposition of iron and examine three parameterizations of iron cycling in the deep ocean: (1) net scavenging onto particles, the simplest model; (2) scavenging and desorption of iron to and from particles, analogous to thorium; and (3) complexation. Provided that some unknown parameter values can be set appropriately, all three biogeochemical models are capable of reproducing the broad features of the iron distribution observed in the modern ocean and explicitly lead to regions of elevated surface phosphate, particularly in the Southern Ocean. We compare the sensi...

Geochimica et Cosmochimica Acta, 1997

16-year time series of lead concentrations in the western North Atlantic Ocean shows that lead co... more 16-year time series of lead concentrations in the western North Atlantic Ocean shows that lead concentrations decreased markedly during the 1980s but that the decline slowed in the 1990s. The decrease during the 1980s can be attributed to the phasing out of leaded gasoline in the United States. Lead concentration levels of the 1990s may be supported by emissions from high temperature industrial activities in the USA rather than by residual leaded gasoline emissions. Lead concentrations in the thermocline above-700 m depth have continued to decrease over this time period. Further decreases in surface water Pb concentrations may be minimal in coming decades, but continued propagation and evolution of the lead distribution in deener waters should be expected.

Geochimica et Cosmochimica Acta, 2005

In Table 5 on page 949, some of the Pb data were omitted. The complete data table is shown on the... more In Table 5 on page 949, some of the Pb data were omitted. The complete data table is shown on the next page. A corrected pdf file for the entire article is provided as an electronic annex to this erratum.

Geochemistry, Geophysics, Geosystems, 2000

We present a decade-long (1981-1990) high-resolution (subseasonal) record of Pb and Cd concentrat... more We present a decade-long (1981-1990) high-resolution (subseasonal) record of Pb and Cd concentrations and Pb isotopic composition in a series of 119 snow samples from a 6-m snow pit at Summit, Greenland. Both metals show order of magnitude seasonal variability, with maxima in spring of every year, coinciding with sulfate peaks. These short-term features complicate attempts to quantify secular decadal-scale trends associated with anthropogenic source changes (e.g., phasing out of leaded gasoline). A small (<50%) decrease during the decade is estimated for Pb, but no significant trend is observed for Cd. Mean concentrations for the snow pit (Pb = 216, Cd = 11 pmol kg À1) are indistinguishable from mean values for nearly continuous samples of the 1-6 m section of a firn core drilled 1 km away, suggesting freedom from contamination artifact. An evaluation of potential sources confirms that Pb and Cd are dominated by anthropogenic inputs. Isotopic ratios (206 Pb/ 207 Pb and 208 Pb/ 207 Pb) determined on a subset of snow pit samples of varying ages within the decade indicate that springtime Pb concentration maxima are consistent with a mixture of eastern European, former Soviet Union, and western European sources, while seasonal Pb minima, especially from the early portion of the decade, plot along a different mixing line, suggesting a mixture of U.S. and European sources. The combination of Pb concentration and isotopic composition are consistent with an estimated decrease in U.S. Pb contributions of about twofold over the decade, which predicts a decadal concentration decrease in the snow of $30%. However, the secular trends in both concentration and isotopes are barely detectable against seasonal and interannual variability. The evidence for seasonally distinct source regions may be useful for interpretation of high-resolution records of other chemical species in Greenland snow and ice. Analyses of two deep core sections dated at 1699-1700 and 1780-1788, compared to the snow pit data, indicate that both Pb and Cd deposition in central Greenland roughly doubled during the eighteenth century, then doubled again by the 1980s.

Earth and Planetary Science Letters, 1977

The general form of Cu-depth profiles is unique. In the central North Pacific, values decrease fr... more The general form of Cu-depth profiles is unique. In the central North Pacific, values decrease from a surface maximum of about 3 nmol/kg to 1.5 nmol/kg in the upper thermocline. Below about 750 m there is an increase to over 6 nmol/kg in the bottom waters with no mid-depth extremum. The profiles in the boundary regions are similar in the deep water but do not have the surface maximum. This unique elemental distribution is maintained by aeolean input to the surface waters comparable in magnitude to the fluvial component, ubiquitous scavenging in the subsurface and deep water, and a strong bottom source. Apparently the scavenging agent, presumably sinking particles, loses its Cu-binding capacity during early diagenesis. The half-life with respect to scavenging is about 1100 years and the overall residence time with respect to input or final removal about 5000 years.

Earth and Planetary Science Letters, 1992

Trace metal partitioning between seawater and particles, both suspended and sinking, must be dete... more Trace metal partitioning between seawater and particles, both suspended and sinking, must be determined to understand and model oceanic trace metal scavenging processes. In order to improve the oceanic particulate trace metal data base, a new in-situ pump was developed and deployed to collect suspended particles from 0-4000 m in the Sargasso Sea near Bermuda. These particles were analyzed for AI, Fe, Mn, Co, Zn, Cu, Ni, Cd and Pb; major particulate carrier phases were estimated from Ca, opaline Si, and P. Cd is the only trace element of this group with a particulate maximum in near-surface waters. The other metals have low particulate concentrations (mol/l) in near-surface waters, and increase with depth into the upper thermocline. Particulate A1 and Fe are then uniform with depth below about 1000 m until increasing in the bottom nepheloid layer. The remaining elements (Mn, Co, Zn, Cu, Ni and Pb) decrease from the mid-thermocline values to lower and relatively uniform concentrations in deep waters, The similarities among the vertical profiles for these metals suggest that authigenic Mn oxides influence their uptake from the dissolved pool, although an important or dominant role for other host phases, specifically particulate organic matter, is not ruled out by the data.

Earth and Planetary Science Letters, 2008

Many of the heaviest and lightest natural zinc (Zn) isotope ratios have been discovered in hydrot... more Many of the heaviest and lightest natural zinc (Zn) isotope ratios have been discovered in hydrothermal ore deposits. However, the processes responsible for fractionating Zn isotopes in hydrothermal systems are poorly understood. In order to better assess the total range of Zn isotopes in hydrothermal systems and to understand the factors which are responsible for this isotopic fractionation, we have measured Zn isotopes in seafloor hydrothermal fluids from numerous vents at 9-10°N and 21°N on the East Pacific Rise (EPR), the TAG hydrothermal field on the Mid-Atlantic Ridge, and in the Guaymas Basin. Fluid δ 66 Zn values measured at these sites range from +0.00‰ to +1.04‰. Of the many physical and chemical parameters examined, only temperature was found to correlate with fluid δ 66 Zn values. Lower temperature fluids (b250°C) had both heavier and more variable δ 66 Zn values compared to higher temperature fluids from the same hydrothermal fields. We suggest that subsurface cooling of hydrothermal fluids leads to precipitation of isotopically light sphalerite (Zn sulfide), and that this process is a primary cause of Zn isotope variation in hydrothermal fluids. Thermodynamic calculations carried out to determine saturation state of sphalerite in the vent fluids support this hypothesis with isotopically heaviest Zn found in fluids that were calculated to be saturated with respect to sphalerite. We have also measured Zn isotopes in chimney sulfides recovered from a high-temperature (383°C) and a low-temperature (203°C) vent at 9-10°N on the EPR and, in both cases, found that the δ 66 Zn of chimney minerals was lighter or similar to the fluid δ 66 Zn. The first measurements of Zn isotopes in hydrothermal fluids have revealed large variations in hydrothermal fluid δ 66 Zn, and suggest that subsurface Zn sulfide precipitation is a primary factor in causing variations in fluid δ 66 Zn. By understanding how chemical processes that occur beneath the seafloor affect hydrothermal fluid δ 66 Zn, Zn isotopes may be used as a tracer for studying hydrothermal processes.

Deep Sea Research Part I: Oceanographic Research Papers, 2000

A towed surface sampling device coupled to two automated #ow injection analysis (FIA) systems is ... more A towed surface sampling device coupled to two automated #ow injection analysis (FIA) systems is described. The towed system permits uncontaminated sampling of seawater from research vessels while underway at full speed. Coupling the sampler to the FIA systems permits automatic determination of Al and Fe in surface waters at natural levels at 5 min intervals, equivalent to &1.5 km spacing at a ship speed of 10 knots (5 m s\). Results from the tropical Atlantic indicate signi"cant (50%) variation in concentrations of both Al and Fe on space scales of less than 90 km. The combined system facilitates surface mapping of large regions of the ocean for dissolved Al and Fe, thus identifying the sites and magnitude of eolian deposition to the surface ocean. In combination with the determination of nutrients and other biological parameters this permits the investigation of the role that eolian deposition plays in modifying surface water biogeochemical cycles.

Chemical Geology, 2003

A consistent method for stable lead isotope analysis of marine carbonates and seawater is present... more A consistent method for stable lead isotope analysis of marine carbonates and seawater is presented, utilizing multiple collector ICP-MS (MC-ICP-MS). This study presents new observations of the large (0.7% amu À 1), time-dependent mass bias determined by thallium normalization, including preferential light ion transmission induced by the acceleration potential and plasma interface (b = À 1.3 to 0.9). These experiments show equivalent results for three empirical correction laws, and the previously proposed b Pb /b Tl correction does not improve isotope ratio accuracy under these conditions. External normalization to SRM-981 following the thallium correction provides one simple alternative, and a rationale is provided based on secondary bias effects. With current intensities less than 1.5 Â 10 À 12 A, external isotope ratio precision better than 250 ppm for SRM-981 207 Pb/ 206 Pb and 208 Pb/ 206 Pb ratios is observed (2r). From reconstructed lead isotopic variability in the North Atlantic, this instrumental precision results in a signal-to-noise ratio greater than 100. Matrix effects are significant with concomitant calcium in SRM-981 (À 280 ppm at 257 AM [Ca]). With the appropriate corrections and minimal concomitants, MC-ICP-MS can reliably determine 207 Pb/ 206 Pb and 208 Pb/ 206 Pb ratios of marine carbonates (30 mg) and seawater (160-200 g).

Analytical Chemistry, 1997

A simple low-blank method is described for the analysis of Pb, Cu, and Cd in seawater using Mg(OH... more A simple low-blank method is described for the analysis of Pb, Cu, and Cd in seawater using Mg(OH) 2 coprecipitation and isotope dilution inductively coupled plasma mass spectrometry (ICPMS). Here, 20-40 µL of 9 M aqueous NH 3 is mixed into a 1.3 mL seawater sample spiked with enriched isotopes of Pb, Cu, and Cd. After centrifugation, the supernatant is discarded and the Mg-(OH) 2 precipitate dissolved in 100 µL of 5% HNO 3 for ICPMS analysis. This method is simple, accurate, and precise, with detection limits of Pb) 1.3 pM, Cu) 39 pM, and Cd) 5.0 pM and blanks of Pb) 0.62 pM, Cu) 27 pM, and Cd) 6.0 pM. The method is demonstrated by oceanographically consistent profiles of these trace metals at an ocean station in the eastern North Atlantic.

Analytical Chemistry, 2013

Organic ligands dominate the speciation of iron in the ocean. Little is known, however, about the... more Organic ligands dominate the speciation of iron in the ocean. Little is known, however, about the chemical composition and distribution of these compounds. Here, we describe a method to detect low concentrations of organic Fe ligands using reverse-phase high-performance liquid chromatography (HPLC) tandem multicollector inductively coupled plasma mass spectrometry. This technique can be used to screen seawater and marine cultures for target compounds that can be isolated and structurally characterized. Sensitive detection (<1 picomole Fe) is achieved using an iron-free HPLC system to reduce background Fe levels, minimizing 40 Ar 16 O + interferences on 56 Fe with a hexapole collision cell, and introducing oxygen into the sample carrier gas to prevent the formation of reduced carbon deposits that decrease sensitivity. This method was tested with a chromatographic separation of five trace metal complexes that represent the polarity range likely found in seawater. Good separation was achieved with a 20 min water/methanol gradient, although sensitivity decreased by a factor of 2 at high organic solvent concentrations. Finally, Fe ligand complexes were detected from the organic extract of surface South Pacific seawater and from culture media of the siderophore producing cyanobacteria Synechococcus sp. PCC 7002.

Deep Sea Research Part I: Oceanographic Research Papers, 2002

We have designed, constructed and tested a trace element clean sampling device for long term depl... more We have designed, constructed and tested a trace element clean sampling device for long term deployment (6 months or longer) on deep-sea moorings. The device collects unfiltered 500 ml samples by opening and closing a bottle originally filled with dilute acid (passively replaced by denser seawater). Each sample is collected by an independent module, so failure of a single unit does not affect others. Seven years of deployments have refined the sampler into a rugged and reliable device. The device also can be hung below a wire to collect water column samples. Automated trace element sampler (ATE), a spinoff from moored in situ trace element serial sampler, is a single-module device for allowing trace metal clean near-surface samples to be collected by personnel not trained in trace element sampling. ATE/VANE, another variation, allows the same personnel to collect upper water column profiles on conventional hydrowire. The systems have been tested by comparing samples collected for lead and iron with those collected by previously proven sampling techniques.