Malcolm Nimmo

The toxicity of copper(II) species to marine algae, with particular reference to macroalgae

Ambient concentrations of dissolved copper(II) in seawater are very low. However, levels can increase as a result of natural and anthropogenic sources. Such increase can have profound effects on organisms in the vicinity resulting in inhibition of growth, reduced fecundity, and even death. This paper highlights the importance of pecieation when considering the toxic effects of cooper, with particular reference to macroalgae in a marine environment, and to encourage more biologists to take account of this in their studies of metal pollution. 104 refs., 2 figs., 4 tabs.

Dry atmospheric inputs of trace metals at the Mediterranean coast of Israel (SE Mediterranean) : sources and fluxes

Abstract This study presents the first detailed data on aerosol concentrations of trace metals (Cd, Pb, Cu, Zn, Cr, Mn, Fe and Al) at the SE Mediterranean coast of Israel, and assesses their sources and fluxes. Aerosol samples were collected at two sampling stations (Tel-Shikmona and Maagan Michael) along the coast between 1994 and 1997. Two broad categories of aerosol trace metal sources were defined; anthropogenic (Cd, Cu, Pb and Zn) and naturally derived elements (Al, Fe, Mn and Cr). The extent of the anthropogenic contribution was estimated by the degree of enrichment of these elements compared to the average crustal composition (EFcrust). High values (median >100) were calculated for Cd, Pb and Zn, minor values for Cu and relatively low values (

Resuspension, reactivity and recycling of trace metals in the Mersey Estuary, UK

Distributions of dissolved and non-detrital (available to 1 M HCl) particulate Cd, Co, Cu, Ni, Pb and Zn have been determined in samples collected from the Mersey Estuary, UK, during four high-resolution axial transects. With the exception of Cu, dissolved metal concentrations displayed positive deviations from conservative behaviour. Cobalt and Ni appeared to have a common source, while dissolved Pb peaks coincided with maximum turbidities in the upper estuary. Concentrations of Cd, Co, Ni and Pb in the <63-μm grain size fraction of bed sediment were greater than those in suspended particulate matter (SPM). Magnitudes of dissolved metal peaks reflected the extent of metal enrichment in fine bed sediment compared with SPM, suggesting that addition of dissolved metal was effected primarily by desorption from resuspendable bed particles. An empirical sorption model, based on the mass balance of metal resuspended from the bed, was able to reproduce the axial distributions of dissolved metals that exhibited the most pronounced peaks (namely, Co and Pb) with reasonable success. More generally, model results indicated that bed sediment need only be moderately enriched in trace metal compared with SPM to cause measurable addition of dissolved metal to the overlying water column. Addition of dissolved metals on estuarine mixing is a common observation in macrotidal environments of western Europe, and it is proposed that resuspension of metal-enriched, fine bed sediment may be a significant agency for metal remobilisation in contaminated, turbid estuaries.

Nutrification impacts on coral reefs from northern Bahia, Brazil

Coral reefs extend for 20 km along the north coast of the state of Bahia, Brazil. Over the last 15 years, this region has experienced an acceleration of generally unplanned urbanisation, with the irregular and indiscriminate use of septic tanks in urban centres contaminating the groundwater. This infiltration of nutrients and pathogens is facilitated by both the soil permeability and an accented hydraulic head, which eventually leads to the percolation of nutrient-rich groundwater seaward to the reefs. The groundwater nutrient concentrations (nitrate, nitrite, ammonia, phosphate and silicate) from Guarajuba beach (a highly urbanised area) are over 10 times higher than groundwater from Papa Gente beach, an area of low human occupation. The pH values of the groundwater samples also indicate the predominance of reducing conditions in Guarajuba, due to the high availability of organic matter and consequent bacterial activity. Additionally, faecal coliform data indicate domestic wastewater as the source of groundwater contamination. High densities of macroalgae and heterotrophic organisms on the impacted reefs, as well as higher concentrations of nutrients, evoke the effects of eutrophication on this coral reef ecosystem. These data suggest that the high availability of nutrients is affecting the trophic structure in the study area, especially in Guarajuba, with the increased turf and macroalgae growth reducing light penetration to the coral colonies, competing with them for space and inhibiting the settlement of new coral larvae.

Determination of dissolved organic carbon in seawater using high temperature catalytic oxidation techniques

The high temperature catalytic oxidation (HTCO)-discrete injection method for liquid samples is currently the preferred analytical technique for the determination of dissolved organic carbon (DOC) in natural water samples. This approach yields equivalent or greater amounts of DOC than wet chemical oxidation methods, is suitable for routine analyses and is stable for shipboard determinations. However, a limited understanding of evaluation criteria for instrument performance presents a number of analytical challenges. This article discusses current practical problems encountered in the (i) collection and handling, (ii) preservation, (iii) decarbonation and (iv) analysis of seawater samples and reviews recent improvements in HTCO systems. Particular reference is made to the issue of certified reference materials and the oxidation efficiency of the technique. Copyright (C) 2000 Elsevier Science B.V.

Rain water-aerosol trace metal relationships at cap ferrat: A coastal site in the Western Mediterranean

Abstract The factors controlling the distributions of the trace metals Al, Co, Ni, Cu and Pb in a series of 25 individual rain water samples collected at Cap Ferrat, a site on the Western Mediterranean coast, are interpreted in relation to aerosols taken simultaneously at the same site. The trace metal chemistry and pH of the rain waters are constrained by the scavenged aerosols, which are composed of a mixture of urban-dominated (European) and crust-dominated (Saharan) components. Thus, the pH values of the rain waters, which range between 3.95 to 6.77, reflect the type of aerosol scavenged from the air; urban-dominated aerosol components giving rise to acidic rains, and crust-dominated aerosol resulting in neutral to basic rains. The average solubilities of the trace metals in the rain waters increase in the order Al (17%), Co (36%), Ni (53%), Pb (65%) and Cu (76%). The paniculate ↔ dissolved speciation of the non-crust-dominated metals Cu and Pb varies with pH, being more soluble at lower pH values, and exhibits the classical pH ‘adsorption edge’. However, the pH of rain can vary during an individual rain event in response to the sequential scavenging of crust-dominated and urban-dominated aerosol components. As a result, the solubility of non-crust-dominated trace metals, such as Pb, can also vary sequentially during an individual rain event; the maximum solubility being related to a ‘dip’ in pH associated with the scavenging of urban-rich aerosol components, followed by a return to the initial pH as the pH-influencing components are exhausted. Data from the present study therefore indicate that the pH-controlled trace metal solubility relationship reported for individual rain events can also occur sequentially in the same event. The particulate material in the rain waters does not contain the relatively high concentrations of Ni, Cu and Pb found in the parent aerosols, and its composition approaches that of crust-dominated aerosols transported to the Mediterranean. Data from the present study, together with those for other Western European coastal locations, indicate that there is a Pb-Cu fractionation between aerosols and rainwaters which results in a significantly greater fraction of the aerosol Pb, relative to Cu, escaping precipitation scavenging in the coastal zone and so becoming available for long-range atmospheric transport.

Trace metal chemistry of particulate aerosols from the UK mainland coastal rim of the NE Irish sea

Data are provided on the long-term average trace metal composition of aerosols collected at two urban (Liverpool and Preston) and one rural (Lancaster) site on the UK mainland coastal rim of the NE Irish Sea. There are variations in the trace metal composition of aerosols at the urban and rural sites, with evidence of local urban `hot spot’ sources of Ni, Zn and Cr. Data from the three sites are combined to give an average trace metal composition of the aerosol at the NE Irish Sea UK coastal sites. This aerosol has higher average concentrations and EFcrust values for some trace metals, e.g. Ni and Cr, than those at other Western European coastal sites but, relative to crustal material, there is general `uniformity of composition’ in the extent to which Ni, Cr, Cu, Zn and Pb are enriched in all the coastal aerosols. To estimate the composition of the aerosol transported to the NE Irish Sea across the UK mainland coast, the coastal strip is partitioned into urban and rural regions and an average trace metal composition for the `whole rim’ aerosol is given. This is used to make an `upper limit’ estimate of the trace metal composition of the aerosol transported to open-sea regions of the NE Irish Sea, which shows a generally similar enrichment of trace metals, relative to crustal material, as that of the North Sea aerosol.

THE RELEASE OF COPPER-COMPLEXING LIGANDS BY THE BROWN ALGA FUCUS VESICULOSUS (PHAEOPHYCEAE) IN RESPONSE TO INCREASING TOTAL COPPER LEVELS

The growth of Fucus vesiculosus L. germlings in chemically defined culture media containing a range of Cu concentrations (20–1000 nM) was monitored simultaneously with measurement of the Cu speciation in the media by competitive equilibrium‐adsorptive cathodic stripping voltammetry. Fucus vesiculosus germlings were found to exude Cu‐complexing ligands with conditional stability constants of the order of 1.6 × 1011. Ligand concentrations increased with increasing total dissolved Cu concentrations (CuT) until a concentration of 500–800 neq Cu·L−1 was reached. Concentrations of the ligand exceeded CuT in treatments containing 20 and 100 nM Cu, were similar to CuT in the 500‐nM Cu treatment, but were less than CuT in the 1000‐nM treatment. Therefore, [Cu2+] were calculated to be at concentrations of 10−11− 10−10 M in the 20‐ and 100‐nM treatments, 10−9 M in the 500‐nM treatment, and 10−7 M in the 1000‐nM treatment. Growth rates were lowest at Cu2+ concentration > 10−9. These results are discussed within the context of the potential roles for exuded copper‐complexing ligands.

Speciation and sorptive behaviour of nickel in an organic-rich estuary (Beaulieu, UK)

Abstract The speciation of dissolved and particulate Ni has been determined along an axial transect of the Beaulieu Estuary, southern England, using adsorptive cathodic stripping voltammetry (ACSV). Total dissolved concentrations ranged from about 80 nM in the river end-member to about 15 nM in the marine end-member, and the ACSV-non-labile fraction, comprising Ni complexes whose alpha coefficients exceed 10 9.2 , contributed between about 15 and 60% of the total dissolved pool. The axial distributions of total dissolved Ni and species thereof, and dissolved organic carbon, could be defined in terms of simple end-member mixing, suggesting little biogeochemical reactivity in the estuary. Particulate Ni was dominated (≥70%) by the fraction available to acetic acid, and a distinct seaward decrease from about 35 to 2 μg g −1 could, likewise, be largely accounted for by mixing of (particle) end-members of different composition. The uptake of Ni by Beaulieu particles was monitored in a series of laboratory simulations employing 63 Ni and liquid scintillation counting. Adsorption was dependent to some degree on salinity, pH and particle type, but most importantly on the presence of dissolved organic matter. Thus, particle–water distribution coefficients ( K D s) were almost doubled when artificial river and sea waters, containing no pre-existing dissolved organic matter, were used in place of organic-rich Beaulieu end-members, and increased by seven-fold when UV-irradiated river water was used in place of untreated river water. These observations were interpreted in terms of the formation of small (sub-colloidal) and relatively strong organic complexes which are relatively resistant to adsorption, and a simple model was developed, incorporating the K D s, to predict the ratio of this fraction of dissolved Ni to the remaining fraction of dissolved Ni as a function of suspended particle concentration. The ACSV (field) measurements of labile and non-labile dissolved Ni from the Beaulieu conformed with the model prediction when K D s for UV-irradiated and untreated river waters were employed, implying that the ACSV-non-labile fraction of dissolved Ni (log 10 α>9.2) affords a good indication of the fraction which is resistant to adsorption. It is suggested that the low biogeochemical reactivity of Ni in the Beaulieu results from a combination of its low particle affinity, maintained by the presence of specific dissolved organic ligands, and small suspended sediment fluxes throughout the estuary. The distributions of Ni in other estuaries are examined and implications for the more general estuarine behaviour of Ni are discussed.

The Influence of Saharan and Middle Eastern Desert-Derived Dust on the Trace Metal Composition of Mediterranean Aerosols and Rainwaters: An Overview

The particulate aerosol over the Mediterranean Sea consists largely of a ‘background’ of European-derived anthropogenic-rich material which has a trace metal composition similar to that over other European coastal seas, but which is subject to sporadic inputs of crustal-rich material from Saharan and Middle East desert sources which are often transported in the form of dust ‘pulses’. The input of Saharan dust results in increases in the total concentrations of crust-controlled trace metals (NEEs), such as Al and Fe, and to decreases in the values of AEEs, such as Cu, Zn and Pb, in the aerosol. Variations in the concentrations of trace metals at any one site in the Mediterranean Sea are largely controlled by: (i) the magnitude of the inputs of crust-rich dusts which are mixed with the anthropogenic-rich ‘background’ material, and (ii) precipitation scavenging, which removes both anthropogenic and crust-rich material from the air.