Transfer of 65Zn from sediments by marine polychaete worms

Silty marine sediments spiked with ⁶⁵Zn lose only small fractions of their radioactivity when exposed to slowly flowing seawater for several weeks. However, polychaete worms (Nereis diversicolor), burrowing through the sediment, cause ⁶⁵Zn losses 3 to 7 times higher than in sediment without worms. Long-term experiments on the uptake and loss of ⁶⁵Zn by the polychaete Hermione hystrix indicate that 60 or more days exposure are required for this worm to approach steady state with ⁶⁵Zn in the sediment. Biological half-life estimates for ⁶⁵Zn accumulated from sediment by H. hystrix are extremely variable (52 to 197 days), depending on the loss-time interval chosen for the calculation. Following 5 days exposure to 16 cm³ of radioactive sediment, N. diversicolor individuals contained an average of 0.2% of the total ⁶⁵Zn in the sediment. When these worms were transferred to non-radioactive sediment, estimates of biological half-life for ⁶⁵Zn averaged 14 to 17 days during the loss period Day 3 to Day 15. Based on these experimental results, it is estimated that a population of N. diversicolor could cause an annual loss of 3% or more of the ⁶⁵Zn in the upper 2 cm of the sediment of a hypothetical radioactive estuary.     

Factors affecting methyl and inorganic mercury dynamics in mussels and shrimp

Radiotracer experiments were designed to study the effect of certain factors on the accumulation and loss of methyl and inorganic mercury in mussels (Mytilus galloprovincialis) and benthic shrimp (Lysmata seticaudata). Methyl mercury was accumulated from both food and water to a greater degree than inorganic mercury by both species. There was a tendency for small mussels to concentrate more mercury than larger individuals, but the reason for this difference remains unclear. A trend towards greater mercury accumulation at higher temperatures was noted for mussels, but the temperature effect was relatively small over a 10 C^o range between 8° and 19°C. Methyl mercury residues were eliminated by both species more slowly than those of the inorganic form. Loss from mussels was somewhat more rapid at higher temperatures; however, as in the case of accumulation, the effect of temperature was relatively small. Loss rates for small mussels were not significantly different from those for large individuals. Enhanced methyl mercury elimination was noted for the group of mussels maintained in their natural environment. The more rapid metal turnover in these individuals compared with mussels held in the laboratory was attributed to differences in the availability of natural particulate food matter and, hence, subsequent growth of the animals in the two experimental systems. The observed differences underscore the need for caution in predicting in situ flux of metals such as mercury in certain species based solely on data derived from laboratory experiments.     

Ammonia excretion of Artemia sp. (crustacea: Branchiopoda) under axenic conditions)

Ammonia excretion of the Utah strain of Artemia sp. grown in axenic culture media was followed throughout the different stages of larval development. The ammonia accumulated in the culture medium does not affect ammonia excretion rates under our laboratory conditions. Growth rate, density and starvation all affect ammonia excretion. Ammonia excretion is directly related to the numerical growth index and inversely related to Artemia sp. density. Starved adult Artemia sp. excrete considerably lower amounts of ammonia than brine shrimp grown in nutritive medium. In view of the difficulties often encountered in estimating the excretion rates of small crustaceans, our culture conditions would appear advantageous for further studies on the purine metabolism of Artemia sp.     

Nitrogen regeneration by the surf zone penaeid prawn Macropetasma africanus

Nitrogen excretion of individual Macropetasma africanus (Balss) from an exposed beach/surf zone in Algoa Bay, South Africa was monitored under laboratory and field conditions in relation to body mass, temperature and feeding during 1985. Excretion rate experiments were performed on starved prawns at 15°, 18°, 20° and 25°C, as well as on individuals fed on four different diets (mussel, fish, shrimp and natural diet) at 15° and 20°C. The ratios of the excreted compounds to total nitrogen excreted were similar for the four diets despite differences in their nitrogen content and in the amount of food consumed. At 15° and 20°C, ammonia excretion rates of fed individuals were four to seven times higher than in starved prawns. the excretion rates were not correlated with nitrogen content of diets. M. africanus recycles 1 557 g NH₄–N per metre strip per year or 1 832 g total nitrogen m^-1 yr^-1, which constitute 12 and 14%, respectively, of total phytoplankton requirements of the surf zone. This study indicates that large motile crustaceans, when abundant, can play an important role in nutrient recycling in turbulent marine environments.     

Influence du niveau sonore de bruit ambiant sur le métabolisme de Crangon crangon (Decapoda: Natantia) en élevage

The influence of ambient noise on the metabolism of the sand-shrimp Crangon crangon L. was estimated from NH₄ excretion and O₂ consumption rates. Two ambient noise levels were compared: the first (+32 dB bar⁺¹) was that present under usual rearing conditions, the second (+5 to 0 dB bar⁺¹) was the level in a soundproof rearing tank. Over a 24 h period, NH₄ excretion and O₂ consumption rates were higher by 1.4 times and 1.2 to 1.4 times, respectively, under the noisy conditions than in the sound-proof tank. The influence of ambient noise level on the shrimp's metabolic level appears to be long-lasting(>1 month). When the acoustic pressure of the environment was increased abruptly, the excretion rate was strongly enhanced but oxygen consumption was reduced; these stress-effects usually disappeared within 3 h. The influence of ambient noise on the metabolic level of this shrimp should be taken into consideration during physiological studies as well as rearing experiments in the laboratory.     

Experimental studies on elimination of zinc-65, cesium-137 and cerium-144 by euphausiids

The elimination of 3 radionuclides from Euphausia pacifica was measured over a 5 month period. The biological half-lives for ⁶⁵Zn, ¹³⁷Cs, and ¹⁴⁴Ce, calculated after the euphausiids had ingested radioactive Artemia nauplii, were found to be 140 days, 6 days, and 7.5 h, respectively. The percentages of body burdens lost in molts were greatest for the fission products, ¹⁴⁴Ce (21%) and ¹³⁷Cs (7%), and least for ⁶⁵Zn (1%). Elimination of the isotopes in the feces could not be followed because of the difficulty in collecting fecal material for analysis; however, 1 sample collected 2 months after the beginning of the elimination experiment had no measurable radioactivity. Loss of ⁶⁵Zn from molts and time to disintegration of the molts were found to be temperature dependent over a 5° to 15°C range, and the sinking rate of molts was both temperature and salinity dependent. Calculations showed that, in areas in the North Pacific outside the influence of upwelling, percentage ⁶⁵Zn loss from sinking molts (before disintegration of the molts) was likely to be the same throughout the year, since the molts would be exposed to about the same mean temperature in the water column in all seasons. Even though temperature structure in the upper layers changes with season, mean temperatures change very little when calculated over the sinking distance of intact molts. Intact molts would sink to slightly over 400 m in the absence of turbulence, and would lose 87% of their ⁶⁵Zn by the time they reached this depth. Sinking molts thus might contribute substantially to the vertical transport of ⁶⁵Zn in the sea. If loss of ⁶⁵Zn in fecal pellets is assumed to be small under our experimental conditions, and molting loss is only 1% of ⁶⁵Zn body burden, the major mechanism of ⁶⁵Zn loss from euphausiids feeding on non-radioactive food must be isotopic exchange with the water. Approximately 96% of the initial body burden was eliminated over a period of 5 months.Supported by USAEC research contract AT (45-1)1830, PHS grant ES00026, and a Richland Graduate Fellowship to S. W. Fowler.     

Risk assessment of heavy metal contamination in shrimp farming in Mai Po Nature Reserve, Hong Kong

An ecological survey was carried out to determine the sediment concentrations of nutrients and heavy metals and bioaccumulation of heavy metals in fish and shrimp including tilapia (Oreochromis mossambicus×O. nilotica), grey mullet (Mugil cephalus), gei wai shrimp (Metapenaeus ensis) and caridean shrimp (Macrobrachium nipponensis) in the traditional tidal shrimp ponds (gei wais) of Mai Po Nature Reserve, Hong Kong. The sediments collected from the landward sites contained higher nutrient contents, as well as zinc (Zn), chromium (Cr), copper (Cu), nickel (Ni) and cadmium (Cd) than those collected from the seaward sites, but vice versa for lead (Pb) and mercury (Hg). However, the concentrations of all metals were exceptionally high in the two sites located outside the reserve, suggesting that waters from Deep Bay might be the possible source of metal contamination affecting the reserve. All metals studied seemed to accumulate in the viscera of fish. Body size was the determining factor for the accumulation of heavy metals in caridean shrimp and gei wai shrimp but not fish. Concentrations of the metals studied in tissues of grey mullet and gei wai shrimp were found to be safe for human consumption. Concentrations of Cr in tilapia whole body (0.68–1.10 mg kg⁻¹ wet weight) were close to or over the guideline value of 1 mg kg⁻¹ set by the Food Adulteration (Metallic Contamination) Regulations of Hong Kong. Tilapia flesh and small caridean shrimp collected from gei wais were contaminated by Cr and Pb but still fit for human consumption. Caution is required if large caridean shrimp is to be consumed in large amounts continuously because the concentration of Pb exceeded the maximum permitted concentration (6 mg kg⁻¹). The rather high Cr concentrations in tilapia whole body should not be overlooked as the fish will serve as a food source for migratory birds visiting the site.     

Daily energy requirements and trophic positioning of the sand shrimp<Emphasis Type="Italic"> Crangon septemspinosa</Emphasis>

Sand shrimp, Crangon septemspinosa Say, are important to the trophic dynamics of coastal systems in the northwestern Atlantic. To evaluate predatory impacts of sand shrimp, daily energy requirements (J ind.^–1 day^–1) were calculated for this species from laboratory estimates of energy losses due to routine (R_R), active (R_A), and feeding (R_SDA) oxygen consumption rates (J ind.^–1 h^–1), coupled with measurements of diel motile activity. Shrimp used in this study were collected biweekly from the Niantic River, Connecticut (41°33N; 72°19W) during late spring and summer of 2000 and 2001. The rates of shrimp energy loss due to R_R and R_A increased exponentially with increasing temperature, with the magnitude of increase greater between 6°C and 10°C (Q₁₀=3.01) than between 10°C and 14°C (Q₁₀=2.85). Rates of R_R doubled with a twofold increase in shrimp mass, and R_SDA was 0.130 J h^–1+R_R, irrespective of shrimp body size. Shrimp motile activity was significantly greater during dark periods relative to light periods, indicating nocturnal behavior. Nocturnal activity also increased significantly at higher temperatures, and at 20°C shifted from a unimodal to a bimodal pattern. Laboratory estimates of daily metabolic expenditures (1.7–307.4 J ind.^–1 day^–1 for 0.05 and 1.5 g wet weight shrimp, respectively, between 0°C and 20°C) were combined with results from previous investigations to construct a bioenergetic model and make inferences regarding the trophic positioning of C. septemspinosa. Bioenergetic model estimates indicated that juvenile and adult shrimp could meet daily energy demands via opportunistic omnivory, selectively preying upon items of high energy content (e.g. invertebrate and fish tissue) and compensating for limited prey availability by ingesting readily accessible lower energy food (e.g. detritus and plant material).Electronic Supplementary Material Supplementary material is available in the online version of this article at Communicated by J.P. Grassle, New Brunswick     

Relative contributions of food and water in the accumulation of zinc by two species of marine fish

A model food chain, utilizing ⁶⁵Zn-labeled and nonlabeled food organisms, was used to measure the relative contributions of food and water to Zn accumulation by Gambusia affinis and Leiostomus xanthurus. Chlamydomonas sp. was fed to Artemia sp. which in turn was fed to G. affinis and L. xanthurus. A trace metal-chelate buffer system was used to maintain a stable free Zn ion activity (10^-8.5 mol l^-1) in the experimental seawater. Food represented 78 to 82% of total accumulation of ⁶⁵Zn by the fish. Thus, food cannot be ignored in assessing the accumulation and toxicity of trace metals.     

The uptake and distribution of 65Zn in oysters

Over a period of 6 weeks in aquaria, Portuguese oysters Crassostrea angulata, accumulate ⁶⁵Zn to a greater extent than do native Ostrea edulis, although intake rates for any particular organ in either species are quite similar. The general distribution pattern of radioactivity in the tissues is similar to that observed for stable zine and ⁶⁵Zn in other oyster species, concentration occurring to the greatest extent in gills and mantle, and least in muscle. The observed equilibrium concentrations and biological half-lives are considerably less than those measured in the natural environment, and the significance of this and its bearing on the mechanism of uptake is discussed. Cobalt and iron depress the rate of ⁶⁵Zn uptake by both oyster soft tissues and the shell. The limiting effect in soft tissues is probably due to competition for sites at the actual point of uptake. The distribution of ⁶⁵Zn in tissue subcellular fractions separated by centrifugation shows the greatest concentration of the radioisotope in the insoluble tissue components of gills, mantle and heart. Appreciable amounts of ⁶⁵Zn are associated with tissue proteins.     

Mechanism of toxicity of zinc to the marine diatomNitzschia closterium

The effect of zinc on cell division, photosynthesis, ultrastructure, respiration, ATP levels, mitochondrial electron-transport chain (ETC)-activity, total thiols and glutathione in the marine diatomNitzschia closterium (Ehrenberg) W. Smith was investigated. Although 65µg Zn 1^–1 halved the cell division rate, photosynthesis and respiration were unaffected by zinc concentrations up to 500µg Zn 1^–1. Most of the zinc associated with the cells was bound at the cell surface, with only 3 to 4% of this extracellular zinc penetrating the cell membrane. Once inside the cell, zinc exerted its toxicity at a number of sites. Increased ATP production and ETC activity were observed in zinc-treated cells. Zinc also enhanced cellular thiols (SH) and total glutathione, and zinc toxicity was reversible by the addition of thiol compounds such as cysteine. Zinc-thiol binding may be a detoxification mechanism for the cell. It is suggested that increased ATP production may provide the energy required for increased glutathione synthesis at the expense of other energy-requiring processes including cell division. The mechanisms of toxicity of ionic zinc and copper toN. closterium were compared.     

The effect of laboratory conditions on the extrapolation of experimental measurements to the ecology of marine zooplankton. IV. Changes in respiration and excretion rates of boreal zooplankton species maintained under fed and starved conditions

Herbivorous zooplankton species (Calanus plumchrus, Paracalanus parvus and Euphausia pacifica) and carnivorous species (Parathemisto pacifica and Pleurobrachia pileus) collected from Saanich Inlet, British Columbia, Canada, were maintained in the laboratory under fed and starved conditions. Respiration rate and excretion rates of ammonia and inorganic phosphate were measured successively on the same batch populations of each species in different feeding conditions. Respiration rate remained at a constant level or increased during the feeding experiment but decreased progressively in starved individuals. Herbivorous, but not carnivorous, species showed a rapid decrease in both excretion rates for the first few days of an experiment irrespective of feeding conditions. However, the general level of excretion rates of fed specimens was higher than that of starved ones. The O:N, N:P and O:P ratios were calculated from respiration, ammonia excretion and phosphate excretion and discussed in relation to metabolic substrates of animals during the experiment. A marked difference was shown in the O:N ratio between fed hervivores (>16) and fed carnivores (7 to 19), suggesting highly protein-oriented metabolism in the latter. One unknown factor causing variation in excretion rates is speculated to be the physiological stress on animals during sampling from the field. It is suggested that the laboratory measurement of realistic excretion rates of zooplankton is difficult owing to their large fluctuations, but this is not the case with respiration rate.     

Patterns of trace-metal distribution in tissues of Pleoticus muelleri (Crustacea: Decapoda: Solenoceridae)

Trace-metal distribution in tissues of the shrimp Pleoticus muelleri Bate from the Patagonian region, Argentina, was related to sex, size and physiological condition. Concentrations of cadmium, copper, manganese and zinc were determined in the digestive gland, male reproductive system and muscle of adult specimens. Significant (p<0.01) sex-dependent differences in mean metal concentrations (g g^-1 wet wt) were found in the following tissues of males and females, respectively: digestive gland, Cu, 82.9 and 30.8; Zn, 32.5 and 44.9; reproductive system, Zn, 12.8 and 38.6; Mn, 1.7 and 3.1; Cd, 0.29 and 0.58. Metal levels of muscle showed no significant differences between sexes. Cadmium was not detected in muscle, suggesting that its incorporation into this tissue was strictly regulated. Metal concentrations in the male reproductive system were in general weakly correlated (0.001<p<0.05) with either body size or the concentration of metals in the digestive gland. The developing ovary incorporated substantial amounts of zinc, while cadmium and copper levels decreased at proportional rates (p<0.001). The patterns of the variations in the concentrations of these metals in the ovary strongly suggested that a regulatory mechanism operated throughout oogenesis. Manganese was not involved in this presumptive mechanism. The results of this study are discussed in terms of concentrations and in absolute amounts for standardized individuals.     

Prey selection by larval weakfish (Cynoscion regalis): the effects of prey size,speed, and abundance

We examined feeding by larval weakfish, Cynoscion regalis (Bloch and Schneider), in laboratory experiments conducted during the 1991 spawning season. under natural conditions weakfish larval development is ca. 3 wk, and we ran separate experiments with larvae of five different ages (5, 8, 11, 14, and 17 d post-hatching). We used two different size classes of rotifers (Brachionus plicatilis) and brine shrimp nauplii (Artemia sp.) as prey organisms. Contrary to results of previous research, weakfish larvae did not select prey based on size alone. When prey abundance was above 100 itemsl^-1 weakfish, larvae always chose large rotifers (length = 216 m) over small rotifers (length = 160 m). At 11 d post-hatching, larvae switched their diet from large rotifers to small brine shrimp nauplii (length = 449 m); however, when fed small rotifers and small brine shrimp nauplii the change in diet occurred at 14 d post-hatching. This pattern of selectivity was maintained in each larval age class. Early-stage larvae (5 and 8 d post-hatching) did not feed selectively when prey abundance was less than 100 itemsl^-1. Late-stage larvae (17 d post-hatching) fed selectively at abundances ranging from 10 to 10000 items^-1. Lwimming speeds of prey items, which ranged from 1 to 6 mms^-1, had no consistent effect on prey selection. These results suggest that weakfish larvae are able to feed selectively, that selectivity changes as larvae age, and that selectivity is also influenced by prey abundance.     

Dynamics of zinc-65 specific activity and total zinc in benthic fishes on the outer continental shelf off Central Oregon

The dynamics of ⁶⁵Zn specific activity and total zinc in benthic fishes on the outer continental shelf off central Oregon (USA) were examined. A differential equation that relates specific activity of ⁶⁵Zn in fish to that in fish food was used to estimate 's (zinc uptake-rate coefficients) for 3 different size classes of the flounder Lyopsetta exillis, a small predator of pelagic Crustacea, and for 1 size class of the flounder Microstromus pacificus, a large predator of infauna. The 's obtained for L. exilis were very close to the obtained in the laboratory for the flounder Pleuronectes platessa. The estimated for M. pacificus was very much smaller than the 's estimated for the other two species. A model that related to predicted weight-specific feeding rates suggested that the smaller of M. pacificus was caused by a low absorption efficiency of zinc from its prey. Sensitivity studies indicated that time histories of specific activity in the fishes are not sensitive to moderate changes in . The negative correlation between specific activity in the diet and in the weight of L. exilis was the major cause of the negative correlative between specific activity and weight in this species. In M. pacificus, where composition of diet does not vary with size, specific activity was independent of weight. The time history of specific activity in M. pacificus was very much lower than those in the different size classes of L. exilis, a result caused mainly by the much lower specific activity of the prey of M. pacificus. Differences in specific activity among other benthic fishes were also correlated with differences in specific activity of their prey. The food-web dynamics responsible for these patterns are discussed. Variation in total zinc concentrations among species was small. Within species of flounder, zinc concentration varied only slightly or not at all with weight.     

Toxicity of metals to tadpoles of the common Sunda toad,Duttaphrynus melanostictus

Tadpoles of the common freshwater Sunda toad, Duttaphrynus melanostictus (Amphibia, Bufonidae), were exposed for a 4-day period under laboratory conditions to copper (Cu), cadmium (Cd), zinc (Zn), lead (Pb), nickel (Ni), iron (Fe), aluminum (Al), and manganese (Mn) at various concentrations. Mortality was assessed and median times of death (LT₅₀) and lethal concentrations (LC₅₀) were calculated. LT₅₀ and LC₅₀ increased with the decrease in mean exposure times and concentrations for all metals. LC₅₀ (96?h) for Cu, Cd, Zn, Pb, Ni, Fe, Al, and Mn were 0.03, 0.3, 4.2, 1.5, 8.8, 0.4, 1.9, and 39?mg?L^?1, respectively. Cu was the most toxic to D. melanostictus, followed by Cd, Fe, Al, Pb, Zn, Ni, and Mn (Cu?>?Cd?>?Fe?>?Al?>?Pb?>?Zn?>?Ni?>?Mn). Duttaphrynus melanostictus is similarly sensitive to these metals as other amphibian tadpoles.     

Effects of zinc stress on growth and antioxidant enzyme responses of Kandelia obovata seedlings

This study evaluated the tolerance and accumulation potential in the mangrove Kandelia obovata under moderate and high levels of external Zn. A greenhouse experiment was conducted to investigate the effects of a range of external Zn concentrations (0–400 mg L^?1) on the growth of this species by counting the lateral root number and measuring the root length, leaf area, and total dry biomass. We also determined the Zn accumulation in plant tissues. K. obovata survived with external Zn concentrations of up to 400 mg L^?1, although the excess metal resulted in a biomass reduction of 34%. A significant increase in antioxidant enzyme activities occurred in roots of plants under high-level Zn stress, suggesting that K. obovata seedlings could tolerate up to 200 mg L^?1 zinc treatment.     

Metabolism and elemental composition of zooplankton from the Barents Sea during early Arctic summer

Rates of oxygen consumption, ammonia excretion and phosphate excretion were measured on a hydromedusae (Aglantha digitale), pteropods (Limacia helicina, Clione limacina), copepods (Calanus finmarchicus, C. glacialis, C. hyperboreus, Metridia longa), an amphipod (Parathemisto libellula), a euphausiid (Thysanoessa inermis) and a chaetognath (Sagitta elegans), all of which were dominant species in the Barents Sea during early summer 1987. Water and ash contents and elemental composition (C and N) were also analysed on the specimens used in these metabolic experiments. Between species variations were 67.8% to 94.7% of wet weight in water content, 6.4% to 56.5% of dry weight in ash content, 16.7% to 61.0% of dry weight in carbon content, and 4.3% to 11.2% of dry weight in nitrogen content. Oxygen consumption rates ranged from 0.33 to 13.8 l O₂ individual^-1 h^-1, ammonia excretion rates, from 0.0072 to 0.885 gN individual^-1 h^-1 and phosphate excretion rates, from 0.0036 to 0.33 g P individual^-1 h^-1. In general, higher rates were associated with larger species, but considerable differences were also seen between species. The ratios between the rates (O : N, N : P, O : P) exhibited a wide species-specific variation, indicating differences in dominant metabolic substrates. Typical protein oriented metabolism was identified only in S. elegans. From the results of metabolic rate measurements and elemental analyses, daily losses of body carbon and nitrogen were estimated to be 0.50 to 4.15% and 0.084 to 1.87%, respectively, showing faster turnover rates of carbon than that of nitrogen. Comparison of daily loss of body carbon of the Barents Sea zooplankton with that of the Antarctic zooplankton indicated reduced rates of the former (63% on average).     

Kinetics of zinc uptake from solution,accumulation and excretion by the decapod crustacean<Emphasis Type="Italic"> Penaeus indicus</Emphasis>

Juveniles of the dendrobranchiate decapod Penaeus indicus take up radiolabelled zinc from solution at all exposure concentrations studied from 5.6 to 100 g l^–1, with an uptake rate constant of 0.045 l g^–1 day^–1 at 15 salinity and 25°C. Over the first 10 days of zinc exposure, the new zinc taken up is added to the existing zinc content of the prawn with no significant excretion; over this period the rate of accumulation of radiolabelled zinc is a measure of the absolute zinc uptake rate from solution. Over the next 10 days of zinc exposure to 10 g Zn l^–1, however, zinc is excreted at about half the rate of uptake resulting in a raised body concentration of zinc. Moulting had no significant effect on the accumulation of zinc. Newly accumulated zinc is distributed to all organs with the highest proportions of body content being found in the exoskeleton, followed by the muscle, the hepatopancreas and the antennal organs. Radiolabelled zinc is subsequently lost from all organs. Unlike caridean shrimps or prawns (pleocyemate decapods), therefore, penaeids (dendrobranchiate decapods) do not show regulation of zinc body concentrations to a constant level over a range of dissolved zinc bioavailabilities by matching zinc excretion to zinc uptake. Nevertheless, unlike amphipod crustaceans, P. indicus does excrete some of the zinc newly accumulated from solution after a time delay. Unlike their caridean counterparts, penaeid prawns inhabiting anthropogenically contaminated coastal waters with raised zinc bioavailabilities can be expected to contain raised body concentrations of zinc.Communicated by J.P. Thorpe, Port Erin     

Heavy metal pollution in soil and plants at bone char site

This study determined the heavy metal concentration in soil and plants at a bone char site in Umuahia, Nigeria. Soil and plant samples collected in a randomized complete block design (RCBD) were analyzed for zinc (Zn), lead (Pb), cadmium (Cd), nickel (Ni), and arsenic (As). The concentration of metals in soil and plants in the vicinity of the bone char site are as follows: Zn (172?mg?kg^?1) and Ni (0.62?mg?kg^?1) in soil were highest at site P₃, Pb (2.37?mg?kg^?1) and As (0.08?mg?kg^?1) at site P₁, and Cd (18.30?mg?kg^?1) at site P₂. In plants, the concentrations of Zn (41.17?mg?kg^?1) and Cd (3?mg?kg^?1) were highest in Albizia ferruginea, Ni in Dialium guineense (0.09?mg?kg^?1), while Pb was in D. guineense (0.08?mg?kg^?1) and Spathodea companulata (0.06?mg?kg^?1). The levels of Zn, Cd, Pb, Ni, and As in soil ranged from 11.2 to 172, 2.68 to 18.2, 0.026 to 2.37, 0.33 to 0.62, and 0.02 to 0.08?mg?kg^?1, respectively. In plants, the concentration of Zn, Cd, Pb, and Ni ranged from 2.01 to 41.17, 0.12 to 3, 0.02 to 0.08, and 0.03 to 0.09?mg?kg^?1, respectively. There were significant correlations between Zn and Cd, and Pb and As in soil. The high concentration of Cd in soil might affect soil productivity.