Trace metals (Cd,Cu, Ni,and Zn) and nutrients in coastal waters adjacent to San Francisco Bay,California

Samples collected in December 1990 and July 1991 show that dissolved Cd, Cu, Ni, and Zn distributions in the Gulf of the Farallones are dominated by mixing of two end-members: (1) metal-enriched San Francisco Bay water and (2) offshore California Current water. The range of dissolved metal concentrations observed is 0.2–0.9 nmol kg^?1 for Cd, 1–20 nmol kg^?1 for Cu, 4–16 nmol kg^?1 for Ni, and 0.2–20 nmol kg^?1 for Zn. Effective concentrations in fresh water discharged into San Francisco Bay during 1990–1991 (estimated by extrapolation to zero salinity) are 740–860 μmol kg^?1 for silicate, 21–44 μmol kg^?1 for phosphate, 10–15 nmol kg^?1 for Cd, 210–450 nmol kg^?1 for Cu, 210–270 nmol kg^?1 for Ni, and 190–390 nmol kg^?1 for Zn. Comparison with effective trace metal and nutrient concentrations for freshwater discharge reported by Flegal et al. (1991) shows that input of these constituents to the northern reaches of San Francisco Bay accounts for only a fraction of the input to Gulf of the Farallones from the estuary system as a whole. The nutrient and trace metal composition of shelf water outside a 30-km radius from the mouth of the estuary closely resembles that of California Current water further offshore. In contrast to coastal waters elsewhere, there is little evidence of Cd, Cu, Ni, and Zn input by sediment diagenesis in continental shelf waters of California.     

Short-term biogeochemical influence of a diatom bloom on the nutrient and trace metal concentrations in South San Francisco Bay microcosm experiments

Two laboratory microcosm experiments were conducted to mimic an annual spring diatom bloom in South San Francisco Bay by isolating the phytoplankton community from the benthic grazing pressure to induce a phytoplankton bloom. The purpose of these experiments was to isolate the impact of a spring diatom bloom on the nutrient and trace metal geochemical cycling. Microcosms were created in 2.5 L incubation bottles and subjected to one of 4 treatments (control, copper [Cu] addition, manganese [Mn] addition, and both Cu and Mn addition) to investigate the toxicity of Cu on the resident plankton and the potential antagonistic effects of Mn on reducing Cu toxicity. Dissolved macronutrient (nitrate + nitrite, phosphate, and silicate), and dissolved and particulate trace metal (Cu, Ni, Mn) concentrations were monitored in the grow-out incubations on a daily basis. Chlorophylla concentrations were also monitored over the course of the experiment and used to calculate diatom-specific growth rates. In the experiments containing ambient South San Francisco Bay surface waters, average specific growth rates were on the order of 1.1 d^?1. The induced diatom blooms resulted in significant removal of macronutrients from the microcosms over the course of the experiments. Our research supports previous suggestions that dissolved Ni and Cu concentrations in South San Francisco Bay have a very low biological availability as a result of organic chelation. Ni(EDTA)^2? has been found to be the dominant dissolved Ni species by other researchers and Cu speciation analyses from this study and others indicate that > 99% of the dissolved Cu in South San Francisco Bay is strongly chelated as CuL₁. The free cupric ion concentration was on the order of 10^?12 M. Marked removal of dissolved Mn was observed in the control treatments, well exceeding expected dissolved Mn removal by diatom uptake. Additions of 375 nM Cu resulted in the complete titration of the chelating ligand (L₁) concentrations. The elevated [Cu²⁺] (≈10^?8MM) appeared to have a toxic effect on the diatom community observed in the significant decreases in their specific growth rates (μ=0.4 d^?1). The suppression of dissolved Mn removal from solution was also observed in treatments spiked with high levels of dissolved Cu, providing support that Mn precipitation was due to biologically mediated oxidation not phytoplankton assimilation. The observed geochemical behavior in the concurrent Cu and Mn addition treatments provide evidence in support of Mn alleviation of Cu toxicity. The biological role in the ambient short-term biogeochemical cycling of Cu and Ni in South San Francisco Bay appears to be minimal due to the inert character of the organic ligand-metal complexes. A significant portion of the annual macronutrient and Mn cycling occurs as a result of spring diatom blooms in South San Francisco Bay.     

The Distribution and Seasonal Variation of Dissolved Trace Metals in Florida Bay and Adjacent Waters

Florida Bay is a shallow carbonate estuary in South Florida. It receives fresh waters from the Everglades that contribute a number of metals to the Bay. The Bay is the largest estuary in Florida with nearly pristine conditions. In this paper we report the first extensive studies of trace metals in the Bay. The seasonal distributions of trace metals (Sc, V, Cr, Co, Cu, Fe, Pb, Mn, Ni and Al) were determined on surface waters in Florida Bay and adjacent waters. The measurements in the Bay were made from May 2000 to May 2001, and the adjacent waters were sampled in September 2000 and May 2002. Most of the dissolved trace metals exhibited their maximum concentrations in summer, except Al and Pb that did not show any seasonal variability. The seasonal variations of the metals are related to the influx of fresh water from rainfall. The lowest concentrations are found during the dry season in the winter and the highest during the wet season in the summer. Several metals (V, Mn, Al, Sc, Fe, Co, Ni and Cr) exhibited their highest concentrations in the western zone of the Bay. These waters from agricultural areas are influenced by Gulf of Mexico waters, which carry metals coming from Barron, Broad and Shark rivers into the Bay. The Shark River always exhibited high concentrations of V, Mn, Al, Sc, Co and Cr. Other possible influences in the western and north-central zone of the Bay are from Flamingo Center, the creeks of Taylor Slough and the mangrove fringe of the Everglades. High concentrations of Al, Co, Ni, Cr, Cu, Fe, and Pb were detected in the eastern zone. The high values found in the northeast are influenced by Taylor Slough runoff and in the southeast by Key Largo, Tavernier Marina and the drainage from the main highway (US1) on Tavernier Key. The minimum concentrations for most of the metals were found in areas near the Key channels that exchange waters between Florida Bay and the Atlantic Ocean (Gulf Stream). The adjacent waters in the Atlantic side including the Gulf Stream waters showed very low concentrations for all the metals studied except for V. In the Bay correlations of V were found: (1) V with salinity and Al and (2) Sc with Si. Most of the other metals did not show any strong correlations with nutrients or salinity. Florida Bay is thus not a typical estuary due to the unique structure of its mud banks and multiple inputs of metals from the mangrove fringe in the north.     

Geochemical variations of major and trace elements in recent sediments,off the Gulf of Mannar,the southeast coast of India

The Gulf of Mannar along the Tuticorin coast is a coral base of the southeast coast of India. To obtain a preliminary view of its environmental conditions, geochemical distribution of major elements (Si, Al, Fe, Ca, Mg, Na, K, P), trace elements (Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd) and acid leachable elements (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd) were analyzed in surface sediment samples from two seasons. Geochemical fractionation confirmed the lithogenic origin of metals, which were mainly associated with the detrital phase. The sediments in the gulf are sandy with abundant calcareous debris, which controls the distribution of total and acid leachable elements. Enrichment factors relative to crust vary by a magnitude of two to three and the presence of trace metals indicates the input of Cr, Pb, Cd, Cu and Zn in both forms through industrial activities. Factor analysis supports the above observation with higher loadings on acid leachable elements and its association with CaCO₃. The increase in concentration of trace metals (Cr, Pb, Cd, Cu, Co, Ni, Zn) along the Gulf of Mannar indicates that the area has been contaminated by the input from riverine sources and the industries nearby. The present study indicates that other sources should be evaluated in the long-term monitoring program.     

Hydrological and geochemical control of metals and arsenic in a Mediterranean river contaminated by acid mine drainage (the Amous River,France); preliminary assessment of impacts on fish (Leuciscus cephalus)

Dissolved and particulate concentrations of metals (Fe, Al, Mn, Co, Ni, Cu, Zn, Cd, Tl, Pb) and As were monitored over a 5 year period in the Amous River downstream of its confluence with a creek severely affected by acid mine drainage (AMD) originating from a former Pb–Zn mine. Water pH ranged from 6.5 to 8.8. Metals were predominantly in dissolved form, except Fe and Pb, which were in particulate form. In the particulate phase, metals were generally associated with Al oxides, whereas As was linked to Fe oxides. Metal concentrations in the dissolved and/or particulate phase were generally higher during the wet season due to higher generation of AMD. Average dissolved (size < 0.22 μm) metal concentrations (μg/L) were 1 ± 4 (Fe), 69 ± 49 (Al), 140 ± 118 (Mn), 4 ± 3 Co, 6 ± 4 (Ni), 1.3 ± 0.8 (Cu), 126 ± 81 (Zn), 1.1 ± 0.7 (Cd), 0.9 ± 0.5 (Tl), 2 ± 3 (Pb). Dissolved As concentrations ranged from 5 to 134 μg/L (30 ± 23 μg/L). During the survey, the concentration of colloidal metals (5 kDa < size < 0.22 μm) was less than 25% of dissolved concentrations. Dissolved metal concentrations were generally higher than the maximum concentrations allowed in European surface waters for priority substances (Ni, Cd and Pb) and higher than the environmental quality standards for other compounds. Using Diffusion Gradient in Thin Film (DGT) probes, metals were shown to be in potentially bioavailable form. The concentrations in Leuciscus cephalus were below the maximum Pb and Cd concentrations allowed in fish muscle for human consumption by the European Water Directive. Amongst the elements studied, only As, Pb and Tl were shown to bioaccumulate in liver tissue (As, Pb) or otoliths (Tl). Bioaccumulation of metals or As was not detected in muscle.     

Dissolved sulfides in the oxic water column of San Francisco Bay,California

Trace contaminants enter major estuaries such as San Francisco Bay from a variety of point and nonpoint sources and may then be repartitioned between solid and aqueous phases or altered in chemical speciation. Chemical speciation affects the bioavailability of metals as well as organic ligands to planktonic and benthic organisms, and the partitioning of these solutes between phases. Our previous, work in south San Francisco Bay indicated that sulfide complexation with metals may be of particular importance because of the thermodynamic stability of these complexes. Although the water column of the bay is consistently well-oxygenated and typically unstratified with respect to dissolved oxygen, the kinetics of sulfide oxidation could exert at least transient controls on metal speciation. Our initial data on dissolved sulfides in the main channel of both the northern and southern components of the bay consistently indicate submicromolar concenrations (from <1 nM to 162 nM), as one would expect in an oxidizing environment. However, chemical speciation calculations over the range of observed sulfide concentrations indicate that these trace concentrations in the bay water column can markedly affect chemical speciation of ecologically significant trace metals such as cadmium, copper, and zinc.     

Importance of geochemical transformations in determining submarine groundwater discharge-derived trace metal and nutrient fluxes

Seasonal (Spring and Summer 2002) concentrations of dissolved (<0.22 μm) trace metals (Ag, Al, Co, Cu, Mn, Ni, Pb), inorganic nutrients (NO₃, PO₄, Si), and DOC were determined in groundwater samples from 5 wells aligned along a 30 m shore-normal transect in West Neck Bay, Long Island, NY. Results show that significant, systematic changes in groundwater trace metal and nutrient composition occur along the flowpath from land to sea. While conservative mixing between West Neck Bay water and the groundwaters explains the behavior of Si and DOC, non-conservative inputs for Co and Ni were observed (concentration increases of 10- and 2-fold, respectively) and removal of PO₄ and NO₃ (decreases to about half) along the transport pathway. Groundwater-associated chemical fluxes from the aquifer to the embayment calculated for constituents not exhibiting conservative behavior can vary by orders of magnitude depending on sampling location and season (e.g. Co, 3.4 × 10²– 8.2 × 10³ μmol d⁻¹). Using measured values from different wells as being representative of the true groundwater endmember chemical composition also results in calculation of very different fluxes (e.g., Cu, 6.3 × 10³ μmol d⁻¹ (inland, freshwater well) vs. 2.1 × 10⁵ μmol d⁻¹(seaward well, S = 17 ppt)). This study suggests that seasonal variability and chemical changes occurring within the subterranean estuary must be taken into account when determining the groundwater flux of dissolved trace metals and nutrients to the coastal ocean.     

Tracing Ni, Cu, and Zn kinetics and equilibrium partitioning between dissolved and particulate phases in South San Francisco Bay, California, using stable isotopes and high-resolution inductively coupled plasma mass spectrometry

Additions of the low occurrence stable isotopes ⁶¹Ni, ⁶⁵Cu, and ⁶⁸Zn were used as tracers to determine the exchange kinetics of metals between dissolved and particulate forms in laboratory studies of natural water and suspended sediments from South San Francisco Bay, CA. Dissolved metal isotope additions were made so that the isotope ratios (rather than total metal partitioning) were significantly altered from initial ambient conditions. Dissolved metal concentrations were determined using an organic ligand sequential extraction technique followed by analysis with high-resolution inductively coupled plasma mass spectrometry (HR-ICPMS). Exchangeable particulate concentrations were extracted using a 20% acetic acid leach followed by determination using HR-ICPMS. Equilibrium and kinetic sorption parameters were quantified according to a general model for trace metal partitioning assuming pseudo-first-order kinetics. Partition coefficients (K_D) were tracked as a function of time over the fortnight experiment. For Ni, Cu, and Zn the initial ambient K_D values were found to be 10^3.65, 10^3.88, and 10^4.52 L kg⁻¹, respectively. As a result of the dissolved metal isotope additions, the partition coefficients for all three metals dropped and then increased back to near ambient K_D values after 14 days. Curve-fitting concentration versus time profiles from both dissolved and exchangeable particulate data sets allowed determination of kinetic rate constants. The best estimates of forward and backward kinetic rate constants for Ni, Cu, and Zn respectively are k′_f = 0.03, 0.07, 0.12 d⁻¹ and k_b = 0.13, 0.12, 0.15 d⁻¹. These results predict that sorption equilibria in South Bay should be reached on the order of a month for Ni, on the order of 3 weeks for Cu, and on the order of 2 weeks for Zn. Together, the dissolved and exchangeable particulate data indicate more sluggish sorption kinetics for Ni than for Cu and Zn and suggest that different chemical forms control the speciation of these three metals in South Bay. Order of magnitude metal sorption exchange rates were estimated using these kinetic results. These calculations indicate that sorption exchange between dissolved and suspended particulate phases can cause dynamic internal cycling of these metals in South San Francisco Bay.     

Mobility of major-, minor- and trace elements in solutions of a planosolic soil: Distribution and controlling factors

Subsurface waters circulating in an unpolluted soil of a planosolic horizon (Massif Central, France) were studied in order to determine their physico-chemical characteristics. Three water sampling sites were chosen along a toposequence. For each site, two piezometers were placed above and in the gravelly and concretion-rich horizon (Fe- and Mn- oxyhydroxides). Concentrations of major-, minor- (cations, anions, Fe, Mn, P and Si) and trace elements (Al, Ba, Cd, Co, Cr, Cu, Ni, Pb, Rb, Sr, Zn and U) were monitored on bulk and filtered water (0.45 μm) to study both the particulate and the dissolved components, from 2004 to 2006, during the soil saturation period (i.e., from November to May). Chemical characteristics of soil solutions provide evidence for various chemical water compositions and for temporal variations of water quality, revealing that the hydrodynamic and chemical reactivity in the solution is different for the three sites. Calculations of pe values indicate a range of redox state of the soil solutions. The pe ranges are different for each piezometer but correspond to anoxic solution. For all piezometers, distribution between the dissolved and the particulate fraction and correlations between the various elements in the soil solutions indicate that: (i) Al and Fe show similar behaviour, (ii) Al is mainly present as oxyhydroxides and (iii) some trace metals are mainly associated with particles which have a mixed nature. The impact of a concretion-rich horizon is noticed both on the nature of particles and on the speciation of trace metals and could be explained by the hydrodynamic and chemical reactivity of the circulating solution. Very few correlations exist between elements in the dissolved phase.     

Metals in the river waters of Primorye

New data are presented on the contents of Fe, Mn, Zn, Cu, Pb, Cd, and Ni in dissolved and particulate modes of occurrence in unpolluted or anthropogenically contaminated major rivers of Primorye. The background contents of dissolved metals are as follows: 0.1–0.5 μg/l for Zn and Ni, 0.3–0.7 μg/l for Cu, 0.01–0.04 μg/l for Pb and Cd, and 2–20 μg/l for Fe and Mn. Common anthropogenic loading (communal wastewaters) notably increases the dissolved Fe and Mn concentrations Industrial wastes lead to a local increase in the contents of dissolved metals in river waters by one to three orders of magnitude. The effect of hydrological regime is expressed most clearly in the areas of anthropogenic impact. The metal contents in the particulate matter are controlled mainly by its granulometric composition. Original Russian Text ? V.M. Shulkin, N.N. Bogdanov, V.I. Kiselev, 2007, published in Geokhimiya, 2007, No. 1, pp. 79–88.     

Heavy metals in sediments from San Antonio Bay and the northwest Gulf of Mexico

Sediments from San Antonio Bay, the northwest Gulf of Mexico, and the Mississippi River Delta were acid leached and analyzed for Fe, Mn, Pb, Zn, Cd, Cu and Ni by atomic absorption spectrophotometry. In order to account for differences in sediment clay, carbonate, and organic matter content, metal concentrations were normalized to Fe. Significant linear correlations of metals to Fe were obtained for unpolluted sediments and deviations from these “natural” statistical populations were found for areas thought to have metal input caused by man. San Antonio Bay sediments show little evidence of metal pollution despite 70 years of shell dredging in the bay. However, the San Antonio-Guadalupe River system, the bay's prime sediment source, has 10% to 50% higher than natural levels of Pb, Cd and Cu. Sediments from a 1500 km² area of the Mississippi River Delta have Pb and Cd concentrations 10% to 100% higher than expected levels. The vertical distribution of Pb and Cd in these sediments suggests that inputs have occurred during the past 30 to 40 years. We find no indication of metal pollution in other areas of the Delta or along the continental shelf of the northwest Gulf of Mexico.     

New operational method of testing colloid complexation with metals in natural waters

A dialysis procedure was used to assess the distribution coefficients of ∼50 major and trace elements (TEs) between colloidal (1 kDa–0.22 μm) and truly dissolved (<1 kDa) phases in Fe- and organic-rich boreal surface waters. These measurements allowed quantification of both TE partitioning coefficients and the proportion of colloidal forms as a function of solution pH (from 3 to 8). Two groups of elements can be distinguished according to their behaviour during dialysis: (i) elements which are strongly associated with colloids and exhibit significant increases of relative proportion of colloidal forms with pH increase (Al, Ba, Cd, Co, Cr, Cu, Fe, Ga, Hf, Mn, Ni, Pb, rare earth elements (REEs), Sr, Th, U, Y, Zn, Zr and dissolved organic C) and (ii) elements that are weakly associated with colloids and whose distribution coefficients between colloidal and truly dissolved phases are not significantly affected by solution pH (As, B, Ca, Cs, Ge, K, Li, Mg, Mo, Na, Nb, Rb, Sb, Si, Sn, Ti, V). Element speciation was assessed using the Visual MINTEQ computer code with an implemented NICA-Donnan humic ion binding model and database. The model reproduces quantitatively the pH-dependence of colloidal form proportion for alkaline-earth (Ba, Ca, Mg, Sr) and most divalent metals (Co, Cd, Mn, Ni, Pb, Zn) implying that the complexation of these metals with low molecular weight organic matter (<1 kDa fraction) is negligible. In contrast, model prediction of colloidal proportion (fraction of 1 kDa–0.22 μm) of Cu²⁺ and all trivalent and tetravalent metals is much higher than that measured in the experiment. This difference may be explained by (i) the presence of strong metal-binding organic ligands in the <1 kDa fraction whose stability constants are several orders of magnitude higher than those of colloidal humic and fulvic acids and/or (ii) coprecipitation of TE with Fe(Al) oxy(hydr)oxides in the colloidal fraction, whose dissolution and aggregation controls the pH-dependent pattern of TE partitioning. Quantitative modeling of metal – organic ligand complexation and empirical distribution coefficients corroborate the existence of two colloidal pools, formerly reported in boreal surface waters: “classic” fulvic or humic acids binding divalent transition metals and alkaline-earth elements and large-size organo-ferric colloids transporting insoluble trivalent and tetravalent elements.     

Rates of trace metal and nutrient diagenesis in an intertidal creek bank

Carbon mineralization in marine sediments is a key process involved in the cycling of carbon, nutrients and trace metals. However, as marine sediments are usually diffusion dominated, the pace of element and nutrient cycling is slow, because consumption of oxidants and/or nutrients in the pore waters via microbial activity often outpaces resupply. Adding an advective flow component to such a system should change the biogeochemical dynamics considerably. Numerical simulations show that shallow coastal aquifers affected by tidal forces can establish ground water velocities of up to 7 cm h⁻¹, driving a circulation of sea water through the sediments with subsequent discharge. Although known to enhance solute exchange, the impact of advection on early diagenesis has not received much attention.To address this issue we mapped the interstitial water chemistry down to 2.5 m sediment depth along a transect on an intertidal creek bank that is subject to a periodic advective flow. Additionally a recently developed hydrogeological simulation of the creek bank was applied to calculate ages of the sampled pore waters. Sample ages obtained were used to quantify (flow path integrated) production or depletion rates for trace metals, nutrients, and sulphate.We find young sea water percolating relatively fast through sediments close to the creek showing strong signs of alteration, whereas pore waters from diffusion dominated regions are less altered. The increase in inorganic nutrients and some trace elements along the flow path requires high rates of turnover. Sulphate, molybdenum, and uranium are almost completely depleted after 200 days, while dissolved inorganic carbon (DIC), ammonia, and manganese increase. Averaged production rates for DIC appear to be three times higher when advection dominated the subsurface flow regime. Our results demonstrate that sites dominated by advection generally show signs of faster rates of diagenetic reactions.     

Early diagenesis of redox-sensitive trace metals in the Peru upwelling area - response to ENSO-related oxygen fluctuations in the water column

Pore water and solid phase data for redox-sensitive metals (Mn, Fe, V, Mo and U) were collected on a transect across the Peru upwelling area (11°S) at water depths between 78 and 2025 m and bottom water oxygen concentrations ranging from ∼0 to 93 μM. By comparing authigenic mass accumulation rates and diffusive benthic fluxes, we evaluate the respective mechanisms of trace metal accumulation, retention and remobilization across the oxygen minimum zone (OMZ) and with respect to oxygen fluctuations in the water column related to the El Niño Southern Oscillation (ENSO).Sediments within the permanent OMZ are characterized by diffusive uptake and authigenic fixation of U, V and Mo as well as diffusive loss of Mn and Fe across the benthic boundary. Some of the dissolved Mn and Fe in the water column re-precipitate at the oxycline and shuttle particle-reactive trace metals to the sediment surface at the lower and upper boundary of the OMZ. At the lower boundary, pore waters are not sufficiently sulfidic as to enable an efficient authigenic V and Mo fixation. As a consequence, sediments below the OMZ are preferentially enriched in U which is delivered via both in situ precipitation and lateral supply of U-rich phosphorites from further upslope. Trace metal cycling on the Peruvian shelf is strongly affected by ENSO-related oxygen fluctuations in bottom water. During periods of shelf oxygenation, surface sediments receive particulate V and Mo with metal (oxyhydr)oxides that derive from both terrigenous sources and precipitation at the retreating oxycline. After the recurrence of anoxic conditions, metal (oxyhydr)oxides are reductively dissolved and the hereby liberated V and Mo are authigenically removed. This alternation between supply of particle-reactive trace metals during oxic periods and fixation during anoxic periods leads to a preferential accumulation of V and Mo compared to U on the Peruvian shelf. The decoupling of V, Mo and U accumulation is further accentuated by the varying susceptibility to re-oxidation of the different authigenic metal phases. While authigenic U and V are readily re-oxidized and recycled during periods of shelf oxygenation, the sequestration of Mo by authigenic pyrite is favored by the transient occurrence of oxidizing conditions.Our findings reveal that redox-sensitive trace metals respond in specific manner to short-term oxygen fluctuations in the water column. The relative enrichment patterns identified might be useful for the reconstruction of past OMZ extension and large-scale redox oscillations in the geological record.     

Fluvial Fluxes of Water, Suspended Particulate Matter, and Nutrients and Potential Impacts on Tropical Coastal Water Biogeochemistry: Oahu, Hawai‘i

Baseflow and storm runoff fluxes of water, suspended particulate matter (SPM), and nutrients (N and P) were assessed in conservation, urban, and agricultural streams discharging to coastal waters around the tropical island of Oahu, Hawai‘i. Despite unusually low storm frequency and intensity during the study, storms accounted for 8–77% (median 30%) of discharge, 57–99% (median 93%) of SPM fluxes, 11–79% (median 36%) of dissolved nutrient fluxes and 52–99% (median 85%) of particulate nutrient fluxes to coastal waters. Fluvial nutrient concentrations varied with hydrologic conditions and land use; land use also affected water and particulate fluxes at some sites. Reactive dissolved N:P ratios typically were ≥16 (the ‘Redfield ratio’ for marine phytoplankton), indicating that inputs could support new production by coastal phytoplankton, but uptake of dissolved nutrients is probably inefficient due to rapid dilution and export of fluvial dissolved inputs. Particulate N and P fluxes were similar to or larger than dissolved fluxes at all sites (median 49% of total nitrogen, range 22–82%; median 69% of total phosphorus, range 49–93%). Impacts of particulate nutrients on coastal ecosystems will depend on how efficiently SPM is retained in nearshore areas, and on the timing and degree of transformation to reactive dissolved forms. Nevertheless, the magnitude of particulate nutrient fluxes suggests that they represent a significant nutrient source for many coastal ecosystems over relatively long time scales (weeks–years), and that reductions in particulate nutrient loading actually may have negative impacts on some coastal ecosystems.     

Temporal variability of trace metals in new jersey pinelands streams: relationships to discharge and pH

Dissolved and particulate trace metal (Al, Cd, Cu, Pb, and Zn) concentrations were determined over a 21 month time period at four streamwater sites in the Pinelands (New Jersey, USA), a coastal plain region characterized by low-pH waters and highly weathered soils. Al and Zn were also determined at two sites over a 5 day period following a major precipitation event. In the Batsto River (pH 4.4–6.3), a representative Pinelands stream draining a largely forested watershed moderately impacted by agriculture, discharge-weighted mean concentrations of dissolved metals were (in nM): Al = 4610; Cd = 0.39; Cu = 4.6; Pb = 1.0; and Zn = 149. Dissolved Cd, Cu, and Zn in the undeveloped Bass River (pH 4.1–4.8) are in a similar range, but Pb concentration is 2–3 times greater. Dissolved metals show highly significant positive correlations to discharge, and weaker inverse relationships to pH over both the long- and short-term time series. Overall, seasonal and short-term variability in dissolved metal concentrations is most consistent with control by hydrologic flow path changes during high discharge, when shallow groundwaters mobilize anthropogenic metals stored in near-surface soil horizons and bypass potential metal removal processes in bordering wetlands. The data also suggest that in-stream metal removal driven by summertime biological productivity may further reduce low-discharge metal concentrations, as a secondary effect. For these metals, the particulate fraction is generally minor, and variations in solution/particle partitioning are unimportant to spatial/temporal variations dissolved concentrations, except for Pb. Estimates of atmospheric input can account for riverine fluxes of these metals, and suggest that Zn retention is minimal in this system, while Pb, Cu and Cd are more strongly retained. The positive relationship between discharge and metals concentration, and the unusually high concentrations in Pinelands streams compared to other world rivers, suggest that riverine effects on metals distributions in the estuary and nearby coastal ocean will be measurable and strongly seasonal.     

Distribution of colloidal trace metals in the San Francisco Bay estuary

The size distribution of trace metals (Al, Ag, Cd, Cu, Fe, Mn, Ni, Sr, and Zn) was examined in surface waters of the San Francisco Bay estuary. Water samples were collected in January 1994 across the whole salinity gradient and fractionated into total dissolved (<0.2 μm colloidal (10 KDa–0.2 μm) and < 10 kDa molecular weight phases. In the low salinity region of the estuary, concentrations of colloidal A1, Ag, and Fe accounted for ≥84% of the total dissolved fraction, and colloidal Cu and Mn accounted for 16–20% of the total. At high salinities, while colloidal Fe was still relatively high (40% of the dissolved), very little colloidal Al, Mn, and Cu (<10%) and no colloidal Ag was detectable. Colloidal Zn accounted for <3% of the total dissolved along the estuary, and colloidal Ni was only detectable (<2%) at the river endmember. All of the total dissolved Cd and Sr throughout the estuary consisted of relatively low molecular weight (<10 kDa) species. The relative affinity of metals for humic substances and their reactivity with particle surfaces appear to determine the amounts of metal associated with colloids. The mixing behavior of metals along the estuary appears to be determined by the relative contribution of the colloidal phase to the total dissolved pool. Metals with a small or undetectable colloidal fraction showed a nonconservative excess (Cd, Cu, Ni, and Mn) or conservative mixing (Sr) in the total dissolved fraction, relative to ideal dilution of river water and seawater along the estuary.

The salt-induced coagulation of colloidal A1, Fe, and Cu is indicated by their highly nonconservative removal along the salinity gradient. However, colloidal metals with low affinity for humic substances (Mn and Zn) showed conservative mixing behavior, indicating that some riverine colloids are not effectively aggregated during their transport to the sea. While colloidal metal concentrations correlated with dissolved organic carbon, they also covaried with colloidal Al, suggesting that colloids are a mixture of organic and inorganic components. Furthermore, the similarity between the colloidal metal:A1 ratios with the crustal ratios indicated that colloids could be the product of weathering processes or particle resuspension. Distribution coefficients for colloidal particles (K_c) and for large, filter-retained particles (K_d) were of the same magnitude, suggesting similar binding strength for the two types of particles. Also, the dependence of the distribution coefficients on the amount of suspended particulate matter (the so-called particle concentration effect) was still evident for the colloids-corrected distribution coefficient (K_p+c) and for metals (e.g., Ni) without affinity for colloidal particles.     

Delivery of Trace Metals (Al,Fe, Mn,V, Co,Ni, Cu,Cd, Ag,Pb) from the Trinity River Watershed Towards the Ocean

The Trinity River (Texas, USA) contains in its watershed 23 different reservoir lakes, the largest one being Lake Livingston situated in the lower Trinity River watershed and two potentially polluting metroplexes, Dallas and Houston. In order to determine fluxes of nutrients and trace metals to Galveston Bay, a survey that included 24 discreet samples collected over a year and at various stages of discharge was carried out during 2000–2001. Geochemical (i.e., sorption by Fe oxyhydroxides), biological (i.e., seasonal uptake by sinking algae in Lake Livingston), and hydrological (i.e., dilution effects by increasing flow rates) controls were found to be mainly responsible for variations in dissolved trace metal concentrations rather than pollution sources. The Trinity River loads of suspended sediments and pollutant trace metals entering Galveston Bay at Anahuac were <20% of those reaching Lake Livingston, and only a few percent of the total upstream trace metal load is entering the Gulf of Mexico. Thus, during the transit through the 23 man-made lakes and an estuary, >96% of the pollutant trace metal load is lost to sediments.     

Major and trace element geochemistry in Zeekoevlei, South Africa: A lacustrine record of present and past processes

This study reports a multi-parameter geochemical investigation in water and sediments of a shallow hyper-eutrophic urban freshwater coastal lake, Zeekoevlei, in South Africa. Zeekoevlei receives a greater fraction of dissolved major and trace elements from natural sources (e.g., chemical weathering and sea salt). Fertilizers, agricultural wastes, raw sewage effluents and road runoff in contrast, constitute the predominant anthropogenic sources, which supply As, Cd, Cu, Pb and Zn in this lake. The overall low dissolved metal load results from negligible industrial pollution, high pH and elevated metal uptake by phytoplankton. However, the surface sediments are highly polluted with Pb, Cd and Zn. Wind-induced sediment resuspension results in increased particulate and dissolved element concentrations in bottom waters. Low C/N ratio (10) indicates primarily an algal source for the sedimentary organic matter. Variation in sedimentary organic C content with depth indicates a change in primary productivity in response to historical events (e.g., seepage from wastewater treatment plant, dredging and urbanization). Primary productivity controls the enrichment of most of the metals in sediments, and elevated productivity with higher accumulation of planktonic debris (and siltation) results in increased element concentration in surface and deeper sediments. Aluminium, Fe and/or Mn oxy-hydroxides, clay minerals and calcareous sediments also play an important role in adsorbing metals in Zeekoevlei sediments.     

Distribution and Removal of Silver and Lead in the Nearshore Waters of Western Taiwan

Concentrations of Al, Mn, Fe, Ag, and Pb in dissolved and particulate phases of the surface water were determined at 15 stations along the coastline off western Taiwan in April of 2007. This study presents the first set of data for Al, Ag, and Pb in the nearshore waters. Latitudinal distribution of these metals showed that high values were present in the regions affected by high fluvial discharge from the Dan-Sui River and the Cho-Sui River. Using the particle fluxes from ²¹⁰Po/²¹⁰Pb disequilibria, the removal fluxes and the residence times of the trace metals were calculated. Based on the K _d values, the sequence of particle affinity of trace metals, Fe ~ Al >> Pb > Mn > Ag, was found. The correlation of the residence times and of the partitioning coefficients of multiple metals in the nearshore waters implies that the affinities to the particles determine the geochemical cycling of metals in the coastal water.