Trace metals in waters.

The topic of this paper is extremely broad, and to allow more useful discussion, emphasis is placed on trace (less than 1 mg/l) metals in fresh surface waters and in drinking waters. An attempt is made to give a broad overview of current knowledge, problems and research with particular reference to the following: (1) metals of interest, current standards of water quality relevant to health, and concentrations of metals in waters; (2) sources of, and other factors affecting, the concentrations of metals; (3) general problems in the measurement of metal concentrations; (4) important research topics.     

Trace metals in Swedish natural fresh waters

Water samples were collected from unpolluted waters in southern and northern Sweden to show the range of natural trace metal concentrations. The results do not indicate any significant differences in metal levels between the two study areas. Negative correlations with pH exist for total concentrations of Cd, Pb, Al, Mn and Zn. The dissolved (dialysable) metal fractions also increase with increasing acidity. The concentration of humic substances influences the distribution of Fe, Mn, Al, Pb, Cr, Co and As, as shown by positive correlations with water colour.Increasing alkalinity has a limiting effect upon concentrations and annual fluctuations of Cd and Pb, and to some extent on Zn, in running waters.     

Trace metals in coastal sediments from Costa Rica

Marine sediment samples from four coastal ecosystems in Costa Rica were taken between the years 2000-2002 and their iron, lead, copper and zinc concentrations were determined by the atomic absorption technique with flame or graphite furnace. In the Pacific coast, Culebra Bay (Papagayo Gulf), Gulf of Nicoya, and Golfito Bay (Dulce Gulf), were selected as representative sites, and Moín Bay, at the Caribbean coast. Mean metal concentrations for all ecosystems followed the same pattern: Fe > Zn > Cu > Pb. No temporal pattern was found for any metal. Iron and copper mean concentrations were higher in Golfito Bay (5.8% and 87 microg/g, respectively) and lower in Moín Bay (3.4% and 52 microg/g, respectively). Zinc mean concentration was also higher in Golfito Bay (96 microg/g), but lower in Culebra Bay (66 microg/g). Lead mean concentration was higher in Moín Bay (6.4 microg/g) and lower in Culebra Bay (3.0 microg/g). Lead highest concentrations occurred in the Caribbean and in Golfito Bay, and for the rest of the elements the maximum values were found in Golfito Bay. On the basis of data obtained in this work, Culebra Bay was considered a relatively unpolluted location; Golfito Bay was more contaminated, and Moín Bay and the Gulf of Nicoya showed an intermediate condition.     

Trace metals in edible marine molluscs and crustaceans from Lebanon

Samples of the edible tissue of cephalopod molluscs (cuttlefish, squid, octopus) and crustaceans (lobster, shrimp) collected off the coast of Lebanon were found to concentrate similar levels of cadmium, copper, nickel, and chromium. Lead and zinc were highest in the cephalopods and iron was highest in the crustaceans.The molluscs collected from Beirut had higher levels of many metals than those taken from the other locations. The Beirut octopus had higher lead, cadmium, copper, iron, and chromium. Lead, cadmium, and copper were also highest in the Beirut cuttlefish while iron and zinc were elevated. The crustaceans from Beirut showed no strong tendency to concentrate higher metal levels, except for the Beirut lobster which had higher copper than the other samples.In the cuttlefish, the analysis of bone showed generally higher cadmium, zinc, nickel, and chromium but lower copper and iron than the muscle. However, at Beirut, the bone samples had much higher iron. Levels of most metals in the exoskeletons of the lobster and shrimp were quite similar to those in the muscle tissue with the exception of iron in the lobster which was highest in the exoskeleton, and zinc in both crustaceans, which was more highly concentrated in the muscle.     

Trace metals in large agglomerates (marine snow)

Marine agglomerates were collected by SCUBA from surface watersof Monterey Bay, California and one coastal site 100 km offPoint Sur, California using trace metal clean techniques. Concentrationsof Al, Fe, Mn, Cu, Ni, Zn, Cd and Pb were measured for bothweak acid soluble and refractory metals and compared to suspendmaterial collected in water bottles at the same locations. Gravimetricanalysis of agglomerate and surrounding suspended particulatematter indicated that although agglomerates represented <0.1%of total water sample volume (determined photographically),they contained up to 50% of the total particulate dry weight;trace metal concentrations in the agglomerate fraction werealso disproportionately high. Agglomerates collected withinMonterey Bay contained large quantitites of inorganic material(>40% dry weight), with most of the associated metals containedprimarily within the refractory fraction. In contrast, the offshorestation agglomerates contained <0.3% inorganic material withmetals primarily associated with the weak acid soluble fraction.Both the metal concentrations and leach characteristics of theoffshore station suggest that these agglomerates were comprisedof an active phytoplankton assemblage highly enriched in Cd.Metal concentrations in the offshore samples in conjunctionwith agglomerate abundance indicate that agglomerates may bea major transporter of trace metals out of the euphotic zone.     

Trace metals in vertebral columns of deep-sea teleost fish

Deep-sea teleost fish were collected from the Sagami Bay near a deep fissure in the Pacific Ocean. Fish were identified as Chlorophthalmis albatrosis, Engyprosopan xystrias, Satyrichthys hians, Ventrifossa garmani, and Halieutaea stellata. The Etmopterus lucifer is not a teleost, but a deepsea shark. Just after being caught and fixed in neutral 20% formol, the vertebral column was resected and prepared for measurement by inductively coupled plasma-atomic emission spectrometry. Trace elements were found to be Al, Si, Ti, Fe, Cu, Cd, Zn, and Hg at micrograms per gram levels. Major elements were Mg, Ca, P, and S at the milligram per gram level. Some of trace elements, Zn and Hg, were also usually found at this level.     

Trace metals and metalloenzymes in placenta after oral administration of lead acetate

The present study was carried out to find the effects of Pb acetate (10-50 mg/kg body wt) after oral administration on:

1. The distribution of elements, such as Fe, Cu, Zn, and Mn;
2. The activity of 6-amino levulenic acid dehydratase (δ-ALAD) and alkaline phosphatase (PAP); and
3. On the level of reduced glutathione (GSH) in murine placenta.

Pb toxicity expressed on a dry-wt basis was reflected in terms of deficiency of δ-ALAD and PAP and enhanced content of GSH. Analysis of trace elements following Pb exposure showed low levels of Mn and Cu. Although Fe composition of placenta remained within normal range with increasing load of endogeneous Pb, Zn decline was not consistent after oral feeding of Pb acetate. Deficiency of PAP after Pb exposure did not correlate with the endogeneous levels of Pb or Zn therein, but correlated with endogeneous levels of Mn. Placental deficiencies of Cu and Mn have been related to the disturbed placental functions by Pb accumulation.     

Trace metals in barnacles:the significance of trophic transfer

Barnacles have very high accumulated trace metal body concentrations that vary with local trace metal bioavailabilities and represent integrated measures of the supply of bioavailable metals. Pioneering work in Chinese waters in Hong Kong highlighted the potential value of barnacles (particularly Balanus amphitrite) as trace metal biomonitors in coastal waters, identifying differences in local trace metal bioavailabilities over space and time. Work in Hong Kong has also shown that although barnacles have very high rates of trace metal uptake from solution, they also have very high trace metal assimilation efficiencies from the diet. High assimilation efficiencies coupled with high ingestion rates ensure that trophic uptake is by far the dominant trace metal uptake route in barnacles, as verified for cadmium and zinc. Kinetic modelling has shown that low efflux rate constants and high uptake rates from the diet combine to bring about accumulated trace metal concentrations in barnacles that are amongst the     

Trace metals in barnacles: the significance of trophic transfer

Barnacles have very high accumulated trace metal body concentrations that vary with local trace metal bioavailabilities and represent integrated measures of the supply of bioavailable metals. Pioneering work in Chinese waters in Hong Kong highlighted the potential value of barnacles (particularly Balanus amphitrite) as trace metal biomonitors in coastal waters,identifying differences in local trace metal bioavailabilities over space and time. Work in Hong Kong has also shown that although barnacles have very high rates of trace metal uptake from solution, they also have very high trace metal assimilation efficiencies from the diet. High assimilation efficiencies coupled with high ingestion rates ensure that trophic uptake is by far the dominant trace metal uptake route in barnacles, as verified for cadmium and zinc. Kinetic modelling has shown that low efflux rate constants and high uptake rates from the diet combine to bring about accumulated trace metal concentrations in barnacles that are amongst the highest known in marine invertebrates.     

Trace metals in barnacles: the significance of trophic transfer

Barnacles have very high accumulated trace metal body concentrations that vary with local trace metal bioavailabilities and represent integrated measures of the supply of bioavailable metals. Pioneering work in Chinese waters in Hong Kong highlighted the potential value of barnacles (particularlyBalanus amphitrite) as trace metal biomonitors in coastal waters, identifying differences in local trace metal bioavailabilities over space and time. Work in Hong Kong has also shown that although barnacles have very high rates of trace metal uptake from solution, they also have very high trace metal assimilation efficiencies from the diet. High assimilation efficiencies coupled with high ingestion rates ensure that trophic uptake is by far the dominant trace metal uptake route in barnacles, as verified for cadmium and zinc. Kinetic modelling has shown that low efflux rate constants and high uptake rates from the diet combine to bring about accumulated trace metal concentrations in barnacles that are amongst the highest known in marine invertebrates.     

Trace metals in mangrove seedlings: role of iron plaque formation

Metal-rich mineral deposits on the roots of aquatic plants, denominated iron plaques, may moderate the uptake of essential, but potentially toxic metals by roots. We investigated the iron plaque formation on the fine, nutritive roots of mangrove seedlings growing in contrasting environments (oxidizing sand flat sediments and reducing mangrove forest sediments) in southeast Brazil. The results indicate that Avicennia schaueriana, Laguncularia racemosa, and Rhizophora mangle seedlings developed an efficient exclusion of Fe, Mn, and Zn through iron plaque formation. This process seems to be influenced substantially by species-specific responses to environmental conditions. While Fe and Zn translocation to leaves appear to be suppressed by accumulation within root tissues, this did not appear to occur for Mn, suggesting that Mn trapping in rhizosphere sediments and iron plaque formation are the main mechanisms responsible for the Mn exclusion from the organism level. In addition to factors well recognized as affecting mangrove seedling development (e.g., salinity stress and nutrient availability), the mediation of trace metal uptake by iron plaque formation possibly contribute to determine the seedling adaptability to waterlogged conditions.     

Trace metals with seasonal considerations in coastal algae and molluscs from Beirut,Lebanon

Twelve species of intertidal algae and molluscs from Ras Beirut, Lebanon have been investigated for their heavy metal content. Atomic absorption spectrophotometric analysis showed that the algae and molluscs concentrated similar levels of most metals. However, of the twelve organisms, Brachydontes variabilis had the highest copper, Patella coerulea and Colpomenia sinuosa had the highest iron, and Pinctada radiata had the highest zinc values with rather elevated cadmium. Cystoseira spinosa concentrated the lowest levels of zinc, and nickel was variable in all organisms.Seasonal comparisons of metal levels were also considered in three algae and three molluscs studied previously. The only signs of seasonal variation in the algae were with nickel and iron in Halimeda tuna and lead in Pterocladia pinnata. Both cadmium and lead were generally lowest in the spring samples of the algae. Lead and nickel concentrations in the molluscs were generally highest in the summer and lowest in the spring. Slight seasonal trends were seen with lead and iron in Brachydontes variabilis and lead in Monodonta turbinata.The lack of comparison data from the Mediterranean, particularly the eastern basin, makes it essential that studies of this nature be continued.     

Trace metals in the benthic habitat of the Maarsseveen Lakes system,The Netherlands

The cadmium, zinc, lead and copper concentrations in benthic invertebrates and sediment were determined during two consecutive winters in the Maarsseveen Lakes system. A sequential extraction procedure was applied to estimate the bioavailability of the trace metals in the sediment. Based on the trace metal analyses of organisms and sediment, it is concluded that the Maarsseveen Lakes system has background levels of cadmium, zinc, lead and copper. As the majority of metals was present in geochemically more stable sediment phases, the sequential extractions provided limited additional information on trace metal bioavailability.     

Iron and neoplasia

Normal and neoplastic cells (like nonpathogenic and pathogenic microorganisms) apparently have similar needs and tolerances for iron, but neoplastic cells (like pathogenic microorganisms) may exhibit altered mechanisms of iron acquisition that permit continued growth in host iron-restricted tissues. Excess iron tends to interfere with host defense against malignant cells (as well as against microbial invaders); severe iron deficiency may likewise be detrimental. Elevated temperature is more toxic towards neoplastic than to normal host cells; it is not yet known whether the site of action of heat might be associated with iron acquisition (as has been demonstrated for gram negative bacteria). Persons or animals with iron overload tend to be at greater risk than normal hosts in the development of neoplasms. Construction of animal models of iron overload, although difficult, is strongly indicated at this time. Based on such models, decisions then can be made about the extent to which (a) nutritional immunity against neoplastic cells is practiced by vertebrate hosts and (b) clinical procedures could be employed to strengthen such immunity as an adjunct to radiotherapy, chemotherapy, and surgery.     

Trace metals in marine,brackish and freshwater prawns (Crustacea,Decapoda) from northeast Algeria

The concentrations of the trace metals Zn, Cu, Fe, Cd and Pb were measured in four caridean decapods; Atyaephyra desmaresti, Palaemonetes varians, Parapenaeus longirostris and Aristeus antennatus, from freshwater , estuarine and marine habitats in northeast Algeria variably affected by anthropogenic metal contamination. The two coastal species (P. longirostris and A. antennatus) are a food source for the local population. Accumulated metal concentrations varied interspecifically, and intraspecifically between sites and between seasons, except in the case of Aristeus antennatus. The fresh and brackish water species (Atyaephyra desmaresti and Palaemonetes varians) accumulated more Cd and Pb than their marine counterparts. Results are discussed with respect to anthropogenic inputs and the environmental conditions of the regions studied.     

Trace metals in sediments from the humber estuary: A statistical analysis of spatial uniformity

Concentrations of seven heavy metals (Cu, Zn, Ni, Cr, Nb, Pb, As) in sediments of the Humber estuary and its tributary rivers have been examined using a variety of statistical methods. Concentrations of metals are rather uniform once the effect of grain size is adjusted for. This uniformity extends for some distance beyond the turbidity maximum, and in fact well beyond the normal limit of salt penetration. Detailed statistical analysis of the data do however reveal some trend of concentrations with position in the estuary, with concentrations of Zn, Ni, and Pb being slightly lower towards the mouth of the estuary. Nb concentrations are higher near the mouth of the Humber, but this reflects the location of two large discharges of Nb here. Once these anomalous samples are removed, Nb concentrations are also shown to be spatially homogeneous. The spatial trends in Zn, Ni and Pb may be due to inputs of very contaminated particulate matter to the upper estuary, to inward transport of uncontaminated clay particles from the North Sea to the lower estuary or to the exchange of metals between particulate matter and water. There are however also spatial trends in sediment particle diameter, so some caution needs to be exercised in drawing conclusions.