Acute toxicities of eleven metals to early life-history stages of the yellow crab Cancer anthonyi

We report findings from the first laboratory experiments to assess toxicities of metals found in drilling muds to embryos and prezoeae of a brachyuran crab. Embryos of Cancer anthonyi are brooded externally on the abdomen of female crabs; thus, embryos may be continuously exposed to pollutants contained in sediments of contaminated benthic habitats. Lethal concentrations of metals to embryos after 7 d exposures were: iron and barium (sulfate), 1 000 mg l^–1; barium (chloride), 100 mg l^–1; aluminum and nickel, 10 mg l^–1; copper and lead, l mg l^–1; cadmium, chromium VI and manganese, 0.01 mg l^–1; mercury, 0.001 mg l^–1. All metals effectively retarded embryos from hatching at concentrations equal or lower to those causing mortality, except for cadmium. Particularly impressive was iron, which suppressed hatching at l to 10 mg l^–1, concentrations previously found non-deleterious to marine organisms and 100 times more dilute than concentrations causing significant embryo mortality. The effects of metals on embryos increased as a function of exposure duration. Embryo mortality was delayed for at least 120 h at concentrations 1.0 mg l^–1, with the exception of mercury. Lethal concentrations established at 96 h were meaningless for crab embryos, because acute toxic thresholds were not attained by that time. Larval survivorship to chromium VI, copper, and zinc increased following exposure of embryos to these metals at low concentrations (1.0 mg l^–1), suggesting induction of biochemical pathways for products which bind or metabolize metals. Identical exposures of embryos to lead failed to enhance subsequent larval survivorship, showing that inductions may be metal-specific. We suggest that exposures of brachyuran embryos at field sites and the success of their subsequent hatching in the laboratory may be a means of assessing environmental contamination otherwise difficult to monitor.     

Nitrate reductase activity in Zostera marina

Eelgrass (Zostera marina L.) has access to nutrient pools in both the water column and sediments. We investigated the potential for eelgrass to utilize nitrate nitrogen by measuring nitrate reductase (NR) activity with an in vivo tissue assay. Optimal incubation media contained 60 mM nitrate, 100 mM phosphate, and 0.5% 1-propanol at pH 7.0. Leaves had significantly higher NR activity than roots (350 vs 50 nmoles NO ₂ ^– produced g FW^–1 h^–1). The effects of growing depth (0.8 m MLW, 1.2 m, 3.0 m, 5.0 m) and location within the eelgrass meadow (patch edge vs middle) on NR activity were examined using plants collected from three locations in the Woods Hole area, Massachusetts, USA, in July 1987. Neither depth nor position within the meadow appear to affect NR activity. Nitrate enrichment experiments (200 M NO ₃ ^– for 6 d) were conducted in the laboratory to determine if NR activity could be induced. Certain plants from shallow depth (1.2 m) showed a significant response to enrichment, with NR activity increasing from >100 up to 950 nmoles NO ₂ ^– g FW^–1 h^–1 over 6 d. It appears that Z. marina growing in very shallow water (0.8 m) near a shoreline may be affected by ground water or surface run-off enrichments, since plants from this area exhibited rates up to 1 600 nmol NO ₂ ^– g FW^–1 h^–1. Water samples from this location consistently had slightly higher NO ₃ ^– concentrations (1.4 M) than all other collection sites (0.7 M). Thus, it is possible that chronic run-off or localized groundwater inputs can create sufficient NO ₃ ^– enrichment in the water column to induce nitrate reductase activity in Zostera leaves.     

Environmental impact of heavy metals (Fe, Ni, Cr, Co) in soils waters and plants of triada in euboea from ultrabasic rocks and nickeliferous mineralisation

Soil, water and vegetation samples were collected from the Triada area of Central Euboea and analysed for heavy metals in order to evaluate their environmental impact. The geology of the area studied includes ultrabasic rocks that are overlaid by Upper Cretaceous limestones whereas Fe–Ni mineralisation is intercalated between either the ultrabasic parent rocks or the karstified Jurassic/Triassic carbonates and the transgessive Upper Cretaceous limestones. All the samples were analysed for heavy metals by using atomic absorption spectroscopy. The heavy metal ranges (in g g^–1) for soils samples are: Ni 480–4000, Cr 240–2720, Co 40–208, Fe 24,000–380,000, Mn 46–1680, Pb 16–56, Zn 40–144, Cu 2–82. The values of soil samples of the Triada area are much higher than the values found for Ni, Cr, Co and Fe, in normal soils of the world. The heavy metal ranges (in g L^–1) for water samples are: Ni 19–24, Cr 19–476, Co <5, Fe <100, Mn <100, Mg 5.7–220.5, As 30–69, Cd <2, Pd <10, Zn 5–11, Cu 2–7. The water samples of the Triada area have Cr and Mg concentrations higher than the permittable values. The heavy metal ranges (in g g^–1) for vegetation samples are: Ni 1–135, Cr 0–24, Co 1–21.5, Fe 20–680, Mn 10–206, Cd 0–10, Pb 0–14, Zn 14–70, Cu 0–10.5. The vegetation samples of the Triada area have so high values of Ni, Cr and Co that are considered toxic. The intercorrelated elements Fe, Ni, Cr, Co of the Triada soils, waters and vegetation reflect their association with the ultrabasic rocks and with the Fe–Ni mineralisation.     

Determination of arsenic in crude petroleum and liquid hydrocarbons

Total arsenic was determined in crude petroleum and liquid hydrocarbons derived from crude petroleum by extraction with boiling water or boiling aqueous nitric acid (concentration 0.25 to 2.5 M), mineralization of the extracts with concentrated nitric/sulphuric acid, and reduction of the arsenate to arsine in a hydride generator. The arsine was flushed into a helium-DC plasma. The arsenic emission was monitored at 228.8 nm. The total arsenic concentration in 53 crude oil samples ranged from 0.04 to 514 mg L^–1 (median 0.84 mg L^–1). Arsenic was also determined in several refined liquid hydrocarbons and in a commercially available arsenic standard in an organic matrix (triphenylarsine in xylene). The method was checked with NIST 1634b Trace Elements in Residual Fuel Oil. The arsenic concentration found in this standard agreed with the certified value (0.12±0.2 g g^–1) within experimental error. Viscous hydrocarbons such as the fuel oil must be dissolved in xylene for the extraction to be successful. Hydride generation applied to an aqueous not-mineralized extract from an oil containing 1.67 g As mL^–1 revealed, that trimethylated arsenic (520 ng mL^–1) is the predominant arsenic species among the reducible and detectable arsenic compounds. Monomethylated arsenic (104 ng ml^–1), inorganic arsenic (23 ng mL^–1), and dimethylated arsenic (low ng mL^–1) were also detected. The sum of the concentrations of these arsenic species accounts for only 39% of the total arsenic in the sample.On leave from Department of Chemistry, Indian Institute of Technology, New Delhi, India     

Spring and summer growth rates of subarctic Pacific phytoplankton assemblages determined from carbon uptake and cell volumes estimated using epifluorescence microscopy

In order to determine whether phytoplankton growth rates were normal or depressed, total plant carbon (g l^–1) and in situ production rates (g C l^–1 d^–1) were measured for phytoplankton assemblages at Weathership Station P (50°N; 145°W) and at 53°N; 145°W in the subarctic Pacific in May and August 1984. Plant carbon, estimated from cell volumes determined using epifluorescence microscopy, was distributed as follow: 28% in the <2 m fraction, 38% in the 2 to 5 m size fraction, and the remainder in size classes >5 m. Carbon-specific growth rates (k), as doublings d^–1, were calculated for the phytoplankton assemblages as a whole at each sampling depth down to 100 m for three days in May and for four days in August. The populations in the upper part of the euphotic zone showed average doubling rates of 1 d^–1 and thus appeared to be growing at rates normally expected for the prevailing conditions of light and temperature. The low chlorophyll concentrations (0.3 to 0.4 mg chl a m^–3) characteristically found in this oceanic region do not seem to be due to very slow growth of algal populations.Contribution No. 1695 of the School of Oceanography, University of Washington, Seattle, Washington 98195, USA     

Arsenic and other toxic elemental contamination of groundwater, surface water and soil in Bangladesh and its possible effects on human health

The problems of contamination caused by arsenic (As) and other toxic metals in groundwater, surface water and soils in the Bengal basin of Bangladesh have been studied. Altogether 10 groundwater, seven surface water and 31 soil samples were collected from arsenic-affected areas and analysed chemically. The geologic and anthropogenic sources of As and other toxic metals are discussed in this paper. The chemical results show that the mean As concentrations in groundwater in the Char Ruppur (0.253mg As L^–1), Rajarampur (1.955mg As L^–1) and Shamta areas (0.996mg As L^–1) greatly exceed the WHO recommended value, which is 0.01mg As L^–1. The concentrations of As in groundwater are very high compared to those in surface water and in surface soil in the three (As-affected) areas studied. This indicates that the source of As in groundwater could be bedrock. The relatively high concentrations of Cr, Cu, Ni, Pb and Zn in surface water, compared to world typical value, are due to the solubility of metal ions, organometalic complexes, coprecipitation or co-existance with the colloidal clay fraction. In the soil, the elevated concentrations of As, Cr, Cu, Ni, Pb and Zn are due to their strong affinity to organic matter, hydrous oxides of Fe and Mn, and clay minerals.     

Primary productivity and sizes of pools of organic carbon in the mixed layer of the ocean

We estimated primary productivity and distributions of carbon in the phytoplankton, micro-zooplankton, and suspended and dissolved matter in various areas of the World Ocean to increase our information about the organic carbon cycle in the surface layer of the sea. Primary productivity ranged from about 0.1 gC m^–2 day^–1 in the Gulf of Mexico to 9 gC m^–2 day^–1 in nutrient-rich water off Peru. Phytoplankton carbon ranged from less than 10 g/l in the former to 750 g/l in the latter and in nutrient-rich water off southwest Africa. Micro-zooplankton carbon usually was less than 50 g/l in all waters, and was dominated by ciliates, copepodids, and copepod nauplii in all areas. Concentrations of particulate carbon ranged from 12 g/l off the east coast of South America to 850 g/l off southwest Africa. Concentrations of dissolved organic carbon varied between 0.5 and 1.5 mg/l in all areas except off Peru, where maximum values of 4.5 mg/l were observed. Turnover rates of carbon by small standing crops of micro-flagellates (1 to 5 longest dimension) and dinoflagellates in nutrient-poor waters were lower than those by large standing crops of diatoms and micro-flagellates in nutrient-rich waters. Concentrations of phytoplankton usually accounted for 20 to 55% and micro-zooplankton for 2 to 30% of the particulate carbon in the surface layer of the sea. Concentrations of dissolved organic carbon were not related to concentrations of particulate carbon in most waters except off Peru, where they appear to be directly related.     

Hydrochemical Monitoring and Heavy Metal Contaminations at the Narim Mine Creek in the Sulcheon District, Republic of Korea

The Narim gold mine is located approximately 200km southeast of Seoul within the Sulcheon mineralised district in the Yeongnam massif, Korea. In this study, environmental geochemical analyses were undertaken for soil, sediment and water samples collected in April, September and November in 1998 from the Narim mine creek. The mine area consists mainly of granitic gneiss; however, mineral constituents of soil and sediment near the mine were mainly composed of quartz, feldspar, mica, amphibole, some pyrite and clay minerals. Also were found some pyrite, arsenopyrite, chalcopyrite, sphalerite, galena, malachite, goethite, various hydroxide and unidentified secondary minerals. Generally, high concentrations of heavy metals in the soil and sediment are correlated with a high proportion of secondary minerals. Hydrochemical compositions of water samples are characterised by relative significant enrichment of Na⁺+K⁺ and alkali metals in the ground water, whereas the surface and mine waters are relatively enriched in Ca²⁺+Mg²⁺ and heavy metals. Anion contents of the ground waters are typically enriched in HCO₃ ^–, NO₃ ^– and Cl^–, whereas the surface and mine waters are highly enriched in HCO₃ ^– and SO₄ ^2–. The pH and EC values of the surface water from the non-mine creek are relatively lower compared with those of the surface water around the mine and waste dump. The range of D and ¹⁸O values (d parameters) of the water samples are shown in distinct two groups for the April waters of 10.1–13.1, and for the November waters of 5.8–7.9, respectively. This range variation indicates that two group water were composed of distinct waters because of seasonal difference. Geochemical modelling showed that mostly heavy toxic metals may exist largely in the form of free metal (M²⁺) and metal-sulphate (MSO₄ ^2–), and SO₄ ^2– concentration influenced the speciation of heavy metals in the mine water. These metals in the ground water could be formed of CO₃ ^– and OH^– complex ions. Using a computer program, saturation indices of albite, calcite, dolomite in mostly surface water show undersaturated and progressively evolved toward the saturation state, however, ground and mine waters are nearly saturated. The gibbsite, kaolinite and smectite are supersaturated in the surface and ground water, respectively. Calculated water-mineral reaction and stabilities suggest that the weathering of silicate minerals may be stable kaolinite. The clay minerals of K-illite and Na-smectite will be transformed to more stable kaolinite owing to the continuous reaction.     

Ammonium regeneration by microzooplankton in the Oslofjord

Concentrations of dissolved inorganic nitrogen compounds above the pycnocline in the Oslofjord are very low in the summer, with turnover times of the inorganic N pools of no more than a few hours. To investigate the possibility that continued phytoplankton growth in the summer depends on ammonium excretion by microzooplankton, rates of NH ₄ ⁺ regeneration and assimilation were measured by a ¹⁵N isotope dilution method. Daytime regeneration rates at 0–2 m depth were 0–28% of the calculated assimilation rates at ambient NH ₄ ⁺ concentrations. Regeneration was faster during a dinoflagellate bloom in August than in mixed diatom-dinoflagellate blooms in June and September. Most of the NH ₄ ⁺ appeared to be produced by juvenile copepods, rotifers, tintinnids, and heterotrophic dinoflagellates in the size fraction 45–200 m.     

A study on the landfill leachate and its impact on the groundwater quality of the greater area

Characterisation of the leachate originating from the Ano Liosia landfill (situated in Attica region, Greece) as well as assessment on the quality of the local aquifer were carried out. The experimental results showed that most of the parameters examined in the leachate samples such as colour, conductivity, TS, COD, NH₃–N, PO₄–P, SO₄ ^2–, Cl^–, K⁺, Fe and Pb were found in high levels. The organic load was quite high since the COD concentrations were in the range of 3250–6125mgL^–1. In addition, the low BOD/COD ratio (0.096–0.195), confirmed that the majority of this organic matter is not easily biodegradable. The groundwater near the landfill site was characterised as not potable and not suitable for irrigation water, since most of the physical and chemical parameters examined – such as colour, conductivity, DS, hardness, Cl^–, NH₃–N, COD, K⁺, Na⁺, Ca²⁺, Fe, Ni and Pb exceeded the permissible limits given by EE, EPA and the Greek Ministry of Agriculture. Furthermore, this study presents the application of the hydrologic evaluation of landfill performance (HELP) model for the determination of the yearly leakage from the base of the landfill after the final capping.     

Seasonal variations of organic-carbon and nutrient transport through a tropical estuary (Tsengwen) in southwestern Taiwan

This paper reports the fluvial fluxes and estuarine transport of organic carbon and nutrients from a tropical river (Tsengwen River), southwestern Taiwan. Riverine fluxes of organic carbon and nutrients were highly variable temporally, due primarily to temporal variations in river discharge and suspended load. The sediment yield of the drainage basin during the study period (1995–1996, 616 tonne km^–2 year^–1) was ca. 15 times lower than that of the long-term (1960–1998) average (9379 tonne km² year^–1), resulting mainly from the damming effect and historically low record of river water discharge (5.02 m³ s^–1) in 1995. The flushing time of river water in the estuary varied from 5 months in the dry season to >4.5 days in the wet season and about 1 day in the flood period. Consequently, distributions of nutrients, dissolved organic carbon (DOC) and particulate organic carbon (POC) were of highly seasonal variability in the estuary. Nutrients and POC behaved nonconservatively but DOC behaved conservatively in the estuary. DOC fluxes were generally greater than POC fluxes with the exception that POC fluxes considerably exceeded DOC fluxes during the flood period. Degradation of DOC and POC within the span of flushing time was insignificant and may contribute little amount of CO₂ to the estuary during the wet season and flood period. Net estuarine fluxes of nutrients were determined by riverine fluxes and estuarine removals (or additions) of nutrients. The magnitude of estuarine removal or addition for a nutrient was also seasonally variable, and these processes must be considered for net flux estimates from the river to the sea. As a result, nonconservative fluxes of dissolved inorganic phosphorus (DIP) from the estuary are –0.002, –0.09 and –0.59 mmol m^–2 day^–1, respectively, for dry season, wet season and flood period, indicating internal sinks of DIP during all seasons. Due to high turbidity and short flushing time of estuarine water, DIP in the flood period may be derived largely from geochemical processes rather than biological removal, and this DIP should not be included in an annual estimate of carbon budget. The internal sink of phosphorus corresponds to a net organic carbon production (photosynthesis–respiration, p–r) during dry (0.21 mmol m^–2 day^–1) and wet (9.5 mmol m^–2 day^–1) seasons. The magnitude of net production (p–r) is 1.5 mol m^–2 year^–1, indicating that the estuary is autotrophic in 1995. However, there is a net nitrogen loss (nitrogen fixation–denitrification < 0) in 1995, but the magnitude is small (–0.17 mol m^–2 year^–1).     

Thallium in marine plankton

Concentrations of thallium in phytoplankton (0.02 to 0.8 g g^–1), zooplankton (0.03 to 0.5 g g^–1) and ichthyoplankton (0.1 g g^–1) from the central Pacific were comparable , as were the atomic ratios of thallium to calcium (3x10^–6) and to potassium (1x10^–6) in those organisms. These relatively constant ratios, plus the biounlimited ocean profile of thallium, indicate that it is rapidly cycled through plankton in the same manner as potassium, its principal biogeochemical analogue. The higher atomic ratios of thallium to potassium in pelagic clays (6x10^–6) and ferromanganese nodules (4x10^–3) suggest that both biological transport processes and abiotic transport processes influence this trace element's oceanic cycle.     

Growth and size structure in a baltic Mytilus edulis population

Since Mytilus edulis L. has very few predators and competitors for space, it has become a biomass dominant in the Baltic proper covering hard substrates from the water surface to more than 30 m depth. In order to investigate the factors controlling size and production in a Baltic M. edulis population, growth was studied by the analysis of annual growth rings, measurements of caged individuals and the analysis of size classes in the population, and on settlement ropes. The total number of mussels in a representative mussel bed at 4 m depth varied between 36 000 and 158 000 ind · m^-2 during the year, mainly due to variations in very small mussels (<2 mm), whereas the abundance of mussels 2mm was rather constant between about 17 000 and 28 000 ind · m^-2. Maximum numbes of mussels < 2 mm, amounting to 132 000 ind · m^-2, were found after settlement in summer, but still half a year later in spring, 65 000 ind · m^-2 < 2 mm were registered, due to very strong intraspecific competition for food and space leading to the competitive suppression of small individuals and large variations in growth rates. Due to the special size-structure of the population only the analysis of annual growth rings could be used to estimate natural shell growth. From being very low in the smallest mussels, growth was linear between about 2–10 yr of age, corresponding to about 3–20 mm length, after which it decreased with a L=32 mm. Over the linear interval, growth in the populations from 3–6 m and 10–15m depth was 3.1 and 2.2 mm · yr^-1, respectively. Meat growth showed strong annual variations mainly due to gonad production. Starving mussels could, however, while utilizing energy reserves, survive losses of up to 78% of their meat biomass. This ability of M. edulis to respire away its own biomass and its apparent tolerance of weight loss has important implication. It will drastically reduce the energy flow to destruents from mussels dying naturally, which is of special significance in the Baltic, where predators and scavengers are scarce. It enables the mussels to endure bad food conditions and buffer strong seasonal variations in food abundance, maintaining the strongly food-and space-limited Baltic M. edulis population at the carrying capacity of the area.     

The arsenic content of bottled mineral waters

The arsenic levels of 23 mineral waters on sale to the public in the United Kingdom were measured. The arsenic content of most waters was below 1 g L^–1 but the statutory limits of 50 ug L^–1 for natural mineral waters and 100 g L^–1 for non-alcoholic beverages were exceeded by the French mineral water, Vichy Célestins (220 ug L^–1). Regular consumption of mineral water of such elevated concentration could make a significant contribution to the intake of the more toxic inorganic species of arsenic, with possible adverse long-term effects on the health of some individuals. The general need for analytical speciation studies of dietary arsenic is emphasised.     

The influence of acidic mine and spoil drainage on water quality in the mid-Wales area

The many abandoned base metal mines of the mid-Wales ore field are sources of extensive pollution. Some of the mineralised veins contain large amounts of pyrite and marcasite and oxidative weathering of these produces sulphuric acid resulting in very acidic mine drainage waters. In addition, the spoil tips associated with these mines can contain abundant iron sulphides. Drainage waters from these sources have pH values as low as 2.6 and are heavily contaminated with metals such as Al, Zn, Cd and Ni.Two of the main rivers of the area, the Rheidol and Ystwyth, intercept heavily contaminated acidic drainage which has a marked effect on water quality. The Rheidol contains over 100 g L^–1 Zn for 16 km downstream of the acid water influx. This level is over three times the recommended EEC limit for Zn in salmonoid waters of low hardness.     

A Geochemical Survey of Topsoil in the City of Oslo, Norway

The city of Oslo is situated centrally in the Oslo-graben, which is a Permian rift basin consisting of different kinds of volcanic and sedimentary rocks. In the summer of 1998, approximately 300 samples of surface soil (2–3cm) were taken systematically, 1km^–2. The investigated area covers about 500km². Samples were dissolved in 7M HNO₃ and analysed for 29 elements with ICP-AES, mercury with cold-vapour technique (CV-AAS) and arsenic and cadmium with a graphite furnace (GF-AAS). A factor analysis is frequently used to identify relationships among sets of interrelated variables. To describe the covariant relationships among the elements, a factor analysis has been completed. The first factor contains the elements Sc, Fe, Li, Co, Al, Cr, Be, K, Ni, V, Mg, Y, Ba, Zr, Mn and As (listed with decreasing communality). These elements are typical for the minerals in the area and most of these elements have a near normal distribution. Sources for this factor are probably geological. The second factor contains Cd, Hg, P, Zn, Cu, Ba and Pb. They have a log-normal distribution. Road traffic is probably one of the sources contributing to this factor. In Norway studded tyres are used frequently in the winter season which results in large amounts of road dust. Leaded petrol has been a major source for Pb but is not in use any more. Wear and tear of tyres and brakes contribute also to this factor. Other sources contributing to this factor are probably industry, rubbish incineration, crematoria and release of some of these elements from structural material by fire. Factors 3, 4 and 6 with elements such as Ca, Na, La, Ti and Sr probably have geological sources. They are associated with minerals like amphiboles, pyroxenes and feldspars and some of the elements are from sea aerosols. Factor 5 contains Mn, Cd, Zn, As and Pb. Manganese may be derived from many different sources such as rock weathering, windblown dust, agriculture and traffic. Since As and Mn are placed in both factor 1 and 5 they probably have both geological and anthropogenic sources. Concentrations of the elements in the second factor are much higher in the central parts of Oslo, than in the rest of Oslo. The median value of Hg in the centre is 0.48mgkg^–1, which is 8 times higher than that in the rest of the city. Also, the other elements have much higher levels in the centre. The industrial district north-east of the centre also has high values. The distribution of arsenic is regular throughout the whole city, but has a slightly higher level in the centre. Norm values for contaminated land used by the Norwegian authorities are 2mg As kg^–1 and 25mg Cr kg^–1. Of 297 samples, 61% contain more than 25mg Cr kg^–1 and 79% more than 3mg As kg^–1, which is the detection limit of the analysis. These samples will therefore be regarded as contaminated. Factor analysis places these elements in the geological factor. The Norm value of zinc is 150mgkg^–1, and 40% of the samples contain more than this. The Norm value of lead is 150mgkg^–1, and 35% of the samples contain. Road traffic is probably the major source for these elements.     

Lead and cadmium in urban allotment and garden soils and vegetables in the United Kingdom

In order to assess the intake of lead and cadmium by consumers of home grown vegetables in urban areas, replicated experimental plots of uniform size, comprising summer and winter crops, were established in 94 gardens and allotments in nine towns and cities in England.The geometric mean lead and cadmium concentrations for the soils (n = 94) were 217 g g^–1 (ranging from 27 to 1,676 g g^–1) and 0.53 g g^–1 (<0.2–5.9 g g^–1), respectively. Compared with agricultural soils, the garden and allotment soils contained elevated levels of lead but not cadmium.Lead concentrations in the vegetables ranged from <0.25 g g^–1 to 16.7 g g^–1 dry weight and cadmium concentrations ranged from <0.025 g g^–1 to 10.4 g g^–1 dry weight. Lead concentrations were higher than reported background levels, although <1% exceeded the statutory limit for saleable food in the UK (1 g g^–1 fresh weight). Cadmium concentrations were generally similar to background levels.     

Hydrobiological parameters during an annual cycle in the Arcachon Basin

Temperature, salinity, nutrients and phytoplankton biomass were monitored on a weekly to bimonthly frequency at six stations in the Bay of Arcachon from July 1984 to July 1985. This particular period appears to have differed from the last ten years in displaying higher amplitudes of both temperature and salinity (1.5° to 24.5°C and 20 to 34.5) at high tide. However, although in spring both temperature and salinity were normal (14°C, 28), an important phytoplankton spring bloom occurred, with maximum chlorophyll levels reaching 15 g l^-1 in April. Utilization of nutrients was high, particularly for nitrate and silicate, the concentrations of which decreased, respectively, from 10–15 to 0.1–2 M and 10–20 to 0.25–3 M from February to May. Exhaustion of nitrate was observed in May, except in areas subjected to river input. In contrast, silicate increased throughout the study area from May to July.     

A Preliminary Study on Soil–Gas Radon Geochemistry According to Different Bedrock Geology in Korea

Three study areas of Kwanak campus (Seoul National University), Boeun (Choongbuk) and Gapyung (Kyonggi) were selected and classified according to their bedrock types in order to investigate soil–gas radon concentrations. The mean values of radon concentrations decreased in the order of Gapyung (40BqL^–1) > Kwanak campus (30BqL^–1) > Boeun (22BqL^–1), and decreased in the order of granite gneiss > banded gneiss > granite > black slate–shale > mica schist > shale–limestone > phyllite schist according to bed rock types. Variation in radon emanation with water content in soils and with soil grain size was assessed by the modified Morse (1976) 3min method. Soil–gas radon concentrations increased with increasing water content in the range of less than about 6–16wt.%, but decreased above 6–16wt.%. Radon concentrations also increased with decreasing soil grain size. Radioactivity analysis of radionuclides of ²³⁸U series in some soil samples indicated their possible radioactive disequilibrium between ²²⁶Ra and ²³⁸U due to the differing geochemical behaviour of intermediate radionuclides. Thus, a radioactive isotope geochemical approach should be necessary for soil–gas radon study.     

Heavy metals in the Sea-Skater Halobates robustus from the Galápagos Islands: Concentrations in nature and uptake experiments,with special reference to cadmium

Samples of Halobates robustus Barber (Heteroptera: Gerridae) from the Galápagos Islands were analysed by optical emission spectrometry. The levels (in g g^-1 dry weight) of Zn (134), Cu (155), Pb (< 1), Cd (7), and Cr (3) were not significantly different among insects of different sexes or developmental stages. The low natural levels of Cd in H. robustus from the relatively unpolluted environment of the Galápagos Islands are compared to the high concentrations of Cd in Halobates spp. from relatively polluted regions. Since the measured levels of Cd in their natural zooplankton food rarely exceed 10 g g^-1, and very little of the Cd is found in the soft tissues, the high Cd concentrations (100 to 200 g g^–1) in some seaskater species have evidently been derived by drinking from the surface microlayer of the seawater.