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The possibility of turning base metals into gold has intrigued many scientists since the early alchemists, and the discovery of significant gold uptake by plants has long been a ‘philosopher's stone’. But background levels of gold in plants are usually very low, rarely exceeding 10 ng per g dry tissue (10 p.p.b.)1. Hyperaccumulator plants2, however, have 100 times the elemental concentrations of normal vegetation, a level of 1 mg per g dry tissue (1 p.p.m.). They can be used in phytoremediation3, the in situ improvement of polluted sites. Hyperaccumulation can be induced by adding a chemical amendment, such as EDTA, to a plant substrate to make soluble an otherwise insoluble target metal, such as lead4. Here we have induced plants to accumulate gold from ores by treating the substrate with ammonium thiocyanate. This technique might be used as a form of biological mining (phytomining) for gold5,6.

— The Iguaracu meteorite, a single stone of 1200 g, fell in Parana State, Brazil in October 1977. It is classified as an H5 ordinary chondrite with olivine of composition Fa 18.7.

The Manitouwabing meteorite whose trace constituents have not been previously quantified was analysed for Au, As, Ga, Ge, Ir, Ni, Os, Pd, Pt, Rh and Ru. Our data confirm that it belongs to subgroup IIIA of the IIIAB group and on the basis of the much higher concentrations of As, Ir, Os, Pt, Rh and Ru, it is not paired with Madoc as had previously been proposed.

The bulk composition, petrography, mineralogy and trace-element content of three New Zealand chondrites (Kimbolton, Morven and Wairarapa Valley) were investigated. Considered as a group, the composition and atomic ratios (Fe/Si, Mg/Si, Ca/Si, Al/Si, Ni/Si, Ir/Ni, Ir/Au and Ir/Si) of these chondrites were relatively consistent and clearly diagnostic of H-type stones. Petrographic studies and microprobe determinations of fayalite and ferrosilite in the olivine and pyroxene of the silicate phases of the New Zealand meteorites showed that the Wairarapa Valley specimen differs from the other two in being well equilibrated. The two non-equilibrated chondrites (Morven and Kimbolton), though potentially derived from the same parent body on the basis of their chemical composition, have a geographical separation distance (650 km) which renders this unlikely. On the basis of petrographic studies, the meteorites are now classified as follows: Kimbolton — type H 4 ; Morven — type H4/5; Wairarapa Valley — type H 6 .

Iridium and 26 other elements were determined in shale from the Cretaceous-Tertiary boundary at the locus classicus (for iridium anomalies) at Woodside Creek, New Zealand. Iridium, gold, copper, cobalt, chromium, nickel, arsenic, molybdenum, and iron were enriched in the basal 2 millimeters of the 8-millimeter shale parting as compared with the rest of the stratigraphic column. No other shale partings in the column had anomalous concentrations of any element when the data were expressed on a carbonate-free basis. The boundary material showed striking compositional similarities with the Stevns Klint Danish boundary shale. Elemental concentrations were in general much higher in the New Zealand material than in nonboundary shales from elsewhere in the world. The high concentration of iridium (153 nanograms per gram) in the basal layer of the boundary, together with the enrichment of other siderophile elements supports the idea of an extraterrestrial source for much of the material. The iridium/gold ratio of 2.1 is also in accordance with such a source. The iridium content of the basal layer is higher than for any other marine boundary shale obtained on land. The integrated iridium value is 187 nanograms per square centimeter of boundary surface.

Gold contents are reported for basaltic lavas and dykes from the Tertiary succession of eastern Iceland. In unsaturated (olivine-normative) tholeiites Au decreases in concentration with degree of differentiation. However, in saturated (quartz-normative) and more differentiated varieties, Au shows a high degree of positive correlation with incompatible elements such as Y and Zr. This behaviour suggests that in the latter rocks Au is not held in early crystallized phases but is enriched in the residual melt so that it follows the trend of the incompatible elements. Thus basaltic andesites and silica-rich icelandites contain twice as much Au ( x = 4.1 ng/g −1 ) as basalts. This general trend appears to follow an erratic but concomitant enrichment of S in the rocks. Oxidation and zeolite alteration have led to mobilization and to enrichment of Au in volcaniclastic units and in the porous top of a lava flow. It is suggested that in older volcanic piles of Icelandic type the most suitable source rocks for Au mineralization could be in the more evolved quartz-normative tholeiites (ferrobasalts), and basaltic andesites and icelandites, particularly dykes and volcaniclastic units. Loosely-held Au is readily mobilized from volcanic glass and sulfides due to weathering, burial metamorphism and hydrothermal alteration. Therefore only the freshest, glassy rocks should be expected to retain their primary Au concentrations.

Automotive emissions are by far the most serious source of environmental lead pollution because of their ubiquitous nature. Their effects on humans have been extensively studied during the past decade and have been reviewed by BROOKS (1977). Blood lead levels are generally considered to be the best indices of the lead burden of humans (LUDWIG et al. 1965) and of domestic animals (BLOOM et al. 1976, WARD et al. 1977).

The species Peltaria emarginata (Boiss.) Hausskn., from areas of serpentine in northern Greece and Euboea, has been found to accumulate extremely high concentrations of nickel, often exceeding 1% of the dry mass of the plant leaf. Extreme behaviour of this kind is not found in other species of Peltaria, nor in related genera such as Ricotia, even for those plants which have grown on a nickel-rich substrate. Several herbarium specimens labelled Peltaria dumulosa Post have also been shown to have very high nickel levels. P. dumulosa appears never to have been described properly, and the specimens have now been identified as Alyssum samariferum Boiss. & Hausskn., a species in which nickel accumulation has been demonstrated previously.

Herbarium specimens (over 700) of Melandrium dioicum and Viscaria alpina from throughout Fennoscandia were analysed for their Cu, Pb and Ni content. About 80 specimens had anomalous levels of one or more of these elements as determined by cumulative frequency plots. Inspection of collection localities of plants with anomalous heavy metal levels showed that some of the main copper mining districts of Norway and Sweden had been identified as well as several major ultrabasic regions of Fennoscandia. Although over half of the observed anomalies could be explained from previous knowledge of nearby sulphide mineralization, it is suggested that the more promising of the remainder are worthy of follow-up investigations.

Orpanoxin, a nonsteroidal anti-inflammatory drug (NSAID) lacking gastric ulcerogenic effects in the therapeutic dose range in rats, was compared with six reference NSAIDs for oral activity in the rat paw carrageenin-induced edema assay. Tested NSAIDs were ranked on the basis of oral mg/kg ED50 values: piroxicam, 0.55; orpanoxin, 35.6; diflunisal, 59.6; benoxaprofen, greater than 300; tolmetin sodium, greater than 300; and sulindac, greater than 300. Zomepirac sodium was inactive. Only the three most potent compounds produced greater than 60% inhibition of edema. Inhibition was generally greater at 4 h than at 6 h post carrageenin for all compounds. Oral activity of orpanoxin was also demonstrated in the guinea-pig u.v.-induced erythema model (ED50 = 24.2 mg/kg p.o. when given 1 h before irradiation) and in the mouse ear croton oil induced edema test (ED50 value = 131 mg/kg p.o.). Topical activity of orpanoxin was assessed in both the guinea-pig and mouse models. In the guinea-pig u.v.-induced erythema model, application (1 h after u.v.) of 1, 5, and 10% (w/v) orpanoxin creams (containing 10% urea) significantly inhibited erythema at 2, 3, and 4 h post-irradiation. Orpanoxin, mefenamic acid, and indomethacin as 1% creams inhibited total erythema scores 70, 92 and 74%, respectively. Evidence for topical activity in the mouse ear assay was also obtained for orpanoxin in diethyl ether or 10% urea cream, but not in dimethylsulfoxide. It was concluded that orpanoxin has anti-inflammatory activity comparable to reference NSAIDs in the rat paw edema test, is active orally in rat, mouse, and guinea-pig models, and shows topical activity in the guinea-pig and the mouse.

Herbarium specimens of all except one of the 168 recognized species ofAlyssumLinnaeus have been analysed for their nickel content in order to identify hyperaccumulators ( > 1000 μg per g dry mass) of nickel. A further 31 hyperaccumulators (all in section Odontarrhena) were dis­covered in addition to the 14 European species reported earlier. Pot trials on the non-accumulatorA. serpyllifoliumDesfontaines and the hyperaccumulatorA. pintodasilvaeDudleyin ed.involving addition of nickel to the medium in which the plants were growing, showed that not all species of section Odontarrhena were able to act as hyperaccumulators of nickel. Hyperaccumulation occurred almost exclusively in the eastern Mediterranean area and Turkey. There appeared to be a definite cor­relation between species diversity, proliferation and endemism on the one hand, and extremely high nickel concentrations ( > 1 %) on the other. The data have been used to assess the evidence for promoting section Odontarrhena to generic rank.

Measurements were made of the lead content of soils and pasture species adjacent to a moderately busy highway (5000 vehicles/24 h) near Bulls. There was an exponential decrease in lead in surface soils away from the road for distances less than 30 m. Highest lead values occurred in autumn and indicated the possibility of splash from wet roads after accumulation of lead during the summer. The immobility of lead in soils was reflected by a sharp concentration gradient in undisturbed soil profiles. Soil profiles in recently-ploughed land showed little differentiation of lead. Lead levels in the pasture species Lolium perenne were invariably higher in leaves than roots, indicating uptake of airborne particulates rather than via root systems. Seasonal variation of lead in leaves of Trifolium repens was much less than for L. perenne and probably reflects differences in growth rates and in relative pasture cover.

The analysis of herbarium specimens has shown that unusual metal uptake by European species of Thlaspi (Cruciferae, mustard family) is not confined to the well-known accumulation of zinc from calaminiferous soils. At least twelve species show unusual accumulation of nickel, to levels of 1000–30,000 μg/g (dry-mass basis), from serpentine or other nickel-rich substrates. In addition, accumulation of zinc to levels above 1000 μg/g in the dry mass of the plant is widespread; about three-quarters of the European species, from a wide variety of soil types, have been found to exhibit this behaviour in the natural state. These observations are significant in many fields, including taxonomy, plant physiology and phytochemistry, but are particularly important in extending the potential of biogeochemical methods of mineral exploration.

The role of indicator plants in geobotanical methods of mineral exploration is reviewed. Some 85 species are discussed and a critical examination is made of their probable role in indicating the presence of aluminum boron, cobalt, copper, gold, iron, lead, manganese, nickel, selenium, silver, uranium and zinc. The efficacy of some of the historical plant indicators is questioned and reviewed in the light of more recent findings. It is observed that over a third of all indicator plants belongs to the families Caryophyllaceae (pink family), Labiatae (mint family) and Leguminosae (pea family).

Rocks and bark samples of Pinus radiata from Union Hill, Waihi, New Zealand were analyzed for 19 elements to establish whether the elemental content of bark could be used to delineate subterranean auriferous quartz reefs and veins. Three elemental concentrations in bark (chromium, nickel and sodium) show sufficiently great differences (P

Pot trials were carried out on plants ofHaumaniastrum katangense, Haumaniastrum robertii andAeolanthus biformifolius. These metallophytes from Zaire were grown in substrates containing from 0–10,000 μg/g (0–1%) copper or cobalt. The tolerance of each species was determined and for cobalt was highest inH. robertii (4000 μg/g) and for copper was highest inAeolanthus biformifolius (9000 μg/g). Discontinuities in the plant-soil curves for each element indicate an exclusion mechanism operating for all three species at lower concentrations of the element in the soil. All species would grow in soils containing only traces of cobalt or copper and this indicated that uptake of heavy metals was not linked to a physiological requirement for either element. The plant-soil relationship for cobalt (P

A method was developed for the determination of Bi and Pd in geological materials. The elements are extracted into methylisobutyl ketone (MIBK) from 3 M HCl using ammonium pyrrolidine dithiocarbamate (APDC) as the ligand. The organic phase is analysed for both elements by graphite furnace atomic absorption spectrometry (GFAAS). The limit of detection (on the original rock sample) was 1 ng g −1 (ppb) for Pd and 200 ng g −1 for Bi. Detection limits could be reduced considerably by increasing the organic/aqueous phase ratios. The precision and accuracy of the method were tested by analysis of the standard soil GXR- 1 and Pt ore PTC- 1 . Precisions of ±6.0% and ±5.2% and accuracies of ±2.5% and ±2.0% were reported for Bi and Pd, respectively. The method was employed to determine Pd and Bi in a Cretaceous-Tertiary (KT) boundary sequence from New Zealand. The correlation between Pd and Ir (determined elsewhere) concentrations was very good and showed that our method could provide a means of determining Pd rather than Ir, and using it as a marker for an extraterrestrial component in boundary shales. Bi concentrations ( −1 ) were very low in the boundary material and these values lend credence to a theory that chalcophiles in KT boundary shales originate from ejecta from an asteroidal or cometary impact with carbonaceous shales in the Earth's crust. Such shales have a low Bi content but high concentrations of other chalcophiles such as As that are enriched in boundary material.

Rocks and constituent minerals of the Meguma Group from southeastern Nova Scotia were analyzed for gold. By far the highest levels (4311 ng/g = ppb, whole rocks (1.0 ppb) and other minerals (

A method is described for determining nanogram quantities of gold in vegetation. The sample is digested with fuming nitric acid. After addition of hydrochloric acid, the gold is extracted into 1 ml of 4-methylpentan-2-one; the organic layer is back-extracted with distilled water to remove iron interference, and gold in the organic layer is determined by electrothermal (graphite furnace) atomic absorption spectrometry. Limits of detection depend on the volume of organic phase used but can be as low as 0.2 ng g −1 for an original sample weight of 1 g.

Nearly 1500 herbarium specimens of 284 of the 438 known species of African Crotalaria were analysed for their cobalt and copper content in order to identify accumulator species of interest for the fields of ecology, mineral exploration and plant physiology. Significant concentrations (> 5 μg/g Co and/or > 50 μg/g Cu) were found in C. cornetii Taub. & Dewèvre, C. peschiana Duvign. & Timp., C. prolongata Baker, and C. variegata Welw. ex Baker, and a few other species. All except one species were from Central Africa and were found mainly in the ‘Copperbelt’ area of Zaïre—Zambia. Accumulator species were confined to 4 of the 15 sections and subsections of the genus, and were found mainly in the closely related sections Dispermae and Crotalaria Longirostres. Discovery of metal accumulation by these species should assist further studies on their ecology and possible role in mineral exploration.

Gold and 16 other elements were determined in 36 plant and 17 till samples from a zone of Au mineralization near Yathkyed Lake in Northwest Territories, Canada. Species sampled were: Salix lanata (willow), Betula glandulosa (birch) Empetrum nigrum (crowberry), Arctostaphylos alpina (bearberry), Vaccinium uliginosum (blueberry), and Ledum decumbens (Labrador tea), all typical tundra species. Within the till there was a strong geochemical association between Au and As, Cu, Fe, Na and S. The Au-As relationship was suggestive of the presence of the mineral arsenopyrite. The Au content of dried vegetation (max. 99 ng g−1) was correlated directly with Al, As, Cu and Fe, and inversely with Ca. For the plant-till relationship, Au in vegetation correlated directly with Au and Fe in the till and inversely with B, Ca,P and Sr in the same medium. The inverse relationship was presumed to be due to an excess of Fe causing antagonism to uptake of the other elements. The Au content of all six species considered as one unit, and of L. decumbens in particular, delineated Au anomalies in the substrate equally as well as the till itself. We believe that biogeochemical prospecting in the Canadian Arctic has merit, particularly since representative plant samples for Au are about one tenth of the weight required for till or soil sampling.

On the basis of biostratigraphy data, it is shown that the Flaxbourne River Cretaceous-Tertiary boundary is among the most complete and least disturbed marine sequences yet found; this is particularly true with respect to its post-Ir anomaly and prelowermost Paleocene sequence. INAA and ICP analyses reveal that the boundary clay is also enriched in Cr and Ni, mainly from meteoritic material, and As, Co, Cu, Sb, and Zn from terrestrial sources. It is found that Zn/Sb, As/Sb, and Zn/As ratios generally fall between crustal and oceanic values, suggesting contributions from both sources.

Elevated copper concentrations were detected in 20 species from the 1913 herbarium collection of W.M. Docters van Leeuwen at Utrecht. These plants had been collected from Salajar Island (near Sulawesi), Indonesia. Anomalous copper concentrations ranged from 80–600 μg/g (dry weight) in leaves of these species. Values for the same species collected outside of Salajar were invariably far lower ( μg/g ) and indicated that the Salajar samples may have been growing over copper-rich substrates. The area has not yet been investigated by other geochemical methods, though extrapolation from the adjacent coast of Sulawesi of presumably similar geology indicates the possibility that the biogeochemical anomalies could be caused by copper-rich tephrites.

Nolinium bromide inhibits gastric acid secretion and gastrointestinal smooth muscle contraction. While the compound's gastric antisecretory action has been attributed in part to inhibition of gastric adenylate cyclase and the gastric proton-transport ATPase, the mechanism of nolinium bromide's relaxant effect on smooth muscle has not been elucidated. We have determined that nolinium bromide inhibits contraction of vascular smooth muscle, using isolated rabbit aortic strips. This report characterizes the specificity of this inhibition (by using several agonists) and its Ca2+ dependence (by using contractile conditions of known dependence on various Ca2+ pools). Nolinium bromide (50-200 microM) was a reversible, insurmountable inhibitor of contractions induced by Ca2+ (in 40 mM KC1 depolarizing medium) and norepinephrine, with IC50 values of 96 and 118 microM, respectively, for suppression of maximum contractile force. Contractions in response to Asn1Val5-angiotensin II in both 2.5 mM Ca2+ and 0 mM Ca2+ medium were also inhibited (IC50 value = 110 microM under both conditions). Initial contraction rates for all these conditions were depressed by nolinium bromide. Nolinium bromide inhibited equally the phasic (internal Ca2+-dependent) and tonic (external Ca2+-dependent) components of norepinephrine-induced contractions. These results extend the muscle relaxant profile of nolinium bromide to include, albeit with low potency, vascular smooth muscle, and show that its potency is similar in inhibiting the contractile response to three different stimuli: angiotensin II, Ca2+, and norepinephrine.

Acetylsalicylic acid (aspirin) can irritate the gastrointestinal tract of man and of animals ultimately resulting in hemorrhagic erosions and ulcers. Since Pepto-Bismol liquid also contains salicylates (primarily bismuth subsalicylate), the relative sensitivity of the GI tract of the rat to hemorrhage and subsequent blood loss in response to Pepto-Bismol and to aspirin was determined. The appearance of blood in the feces of male Sprague-Dawley rats 22 hr after the peroral administration of aspirin or Pepto-Bismol at equivalent salicylate doses was measured spectrophotometrically using the modified benzidine assay. Aspirin, administered in total salicylate doses of 38.4, 57.5, 76.7 or 153 mg/kg caused a dose-dependent increase in blood loss ranging from 53 to 276 μl/kg body weight, the latter 2 values being significantly different from control. Pepto-Bismol at total salicylate doses of 38.4, 57.5 or 76.7 mg/kg failed to cause blood loss. Neither Pepto-Bismol nor aspirin obscured recovery of orally-dosed blood in rat feces. The sensitivity of the benzidine assay allowed for the quantitative assessment of 5 μl or less blood per gram of feces. It was concluded that at equivalent salicylate dose levels, Pepto-Bismol, unlike aspirin, did not cause a dose-dependent increase in blood in the feces of rats, suggesting that salicylates should not be collectively categorized as inducing gastric mucosal damage.

Abundances for iridium and 18 other elements were determined in samples from a Cretaceous-Tertiary (K-T) boundary sequence near Wharanui, Marlborough Province, South Island, New Zealand. Physical correlation and biostratigraphic evidence pinpointed a 20 mm layer of calcified boundary clay containing highly anomalous concentrations of indium (33 ng/g [ppb]) and other siderophiles such as nickel (497 μg/g [ppm]), chromium (140 μg/g), and cobalt (137 μg/g). Concentrations expressed on a decalcified (CaCO3-free) basis to avoid false anomalies caused by redissolution of carbonates after deposition are: 62 ng/g, 929 μg/g, 262 ng/g, and 256 μg/g, respectively. The integrated iridium deposition is 132 ng/cm2 after correction for background, and is almost exactly the same as the 134 ng/cm2 recorded for the Flaxbourne River K-T boundary sequence which is virtually complete. This indicates the probable completeness of the Wharanui sequence, though thorough paleontological confirmation will be difficult to o...

Plant and soil sampling was carried out across scheelite-bearing ore-bodies at six areas of different geological, vegetational, climatic and topographical environments in the South Island of New Zealand. The feasibility of using the concentration of tungsten in plants and soils to locate the scheelite was investigated for all the areas. These regions may be classified into two main groups according to their lithology and vegetation. The first group, comprising Clenorchy, Paradise, Macrae's Flat and Top Valley, is underlain by the schists of the New Zealand geosyncline, has a low rainfall and a predominantly shallow-rooted vegetation such as tussock grass and bracken. In these areas soil sampling was generally more effective than plant sampling, although the latter sometimes gave sharper anomalies. The areas of the second group, Barrytown and Canaan, are both underlain by predominantly granitic material, have a high rainfall, rugged topography and a predominantly beech forest vegetation. In these areas, although soil sampling was in general satisfactory, tree-trunk sampling was found to have certain advantages in locating extensions of known scheelite-bearing reefs.

Herbarium specimens (over 400) of all the 64 species of Alyssum listed in the Flora Europaea were analysed for their nickel and cobalt content in order to identify hyperaccumulators ( > 1000 μg/g dry mass) of either element. In addition to the three previously recorded hyperaccumulators of nickel ( A. bertolonii , A. murale and A. serpyllifolium s. sp. lusitanicum ), a further 11 were identified. With the exception of A. fischerianum , all hyperaccumulating species are from Section Odontarrhena of the genus and include A. alpestre, A. argenteum, A. corsicum, A. euboeum, A. fallacinum, A. heldreichii, A. markgrafii, A. robertianum, A. smolikanum and A. tenium . Nickel contents exceeding 10000 μg/g (1%) were recorded in A. bertolonii, A. corsicum, A. heldreichii, A. markgrafii and A. roberti­anum . The occurrence of 14 hyperaccumulators in a single genus is the highest density so far recorded and poses interesting questions concern­ing the plant chemistry of these species.

Herbarium specimens of the genus Haumaniastrum (mainly from Shaba Province Zaire) were analysed for copper and cobalt.H. homblei showed elevated copper levels and indicated its tolerance to mineralized ground.H. robertii (previously-known as a “copper flower”) showed the expected high copper concentrations, but contained abnormally high concentrations of cobalt (av. 4304 μg/g dry weight) far exceeding those of copper. This species has the highest cobalt content of any phanerogam and its distribution may be controlled by cobalt rather than by copper. re]19761220

Experiments were carried out on 11 species of Alyssum of which 9 had the capacity to accumulate very high concentrations of nickel. These hyperaccumulators were grown in substrates containing 30–10000 μg/g nickel. Their nickel content after 6 weeks was a function of the nickel content of the soil and reached a limiting value of approx. 10 000 μg/g in dried leaves of the 9 species. The tolerance of 4 of the species towards nickel was determined by measuring the length of new roots on excised seedlings suspended in aerated solutions containing 0–100 μg/ml nickel. Four hyperaccumulating taxa tolerated nickel concentrations in the range 15–60 μg/ml. In rate-of-uptake experiments on A. euboeum, it was observed that nickel uptake was complete in approx. 6 days after addition of nickel to the substrate.

A herbarium collection of plants from Obi Island (North Moluccas) was analyzed for nickel and other elements in order to identify new hyperaccumulators (> 1000 μg/g dry weight) which are indicative of ultrabasic substrates. Ultrabasic substrates are usually hosts for important economic minerals. Planchonella oxyedra Dubard and Trichospermum kjellbergii Burret were found to be hyperaccumulators of nickel and the work was therefore followed up by analysis of further specimens of these two species from localities throughout their range in Southeast Asia and Oceania. The data pinpointed previously known ultrabasic areas in Sulawesi (Celebes) and West Irian (Indonesian New Guinea) as well as one in Ambon (South Moluccas) which is not recorded on geological maps.

Biological methods (geobotany, biogeochemistry and geozoology) of exploration for gold are reviewed. Data are also presented for the gold content of 134 species of plants. Methods of chemical analysis for gold are also reviewed. The section on geozoology includes a discussion of the use of termite hills in prospecting for gold in Central Africa.

Lead levels were determined in organs of sheep exposed to lead pollution from automotive exhaust emissions. In three experiments involving (a) sheep grazed near busy highways, (b) sheep kept away from emissions but fed with contaminated grass and (c) sheep exposed to emissions but fed with uncontaminated grass, considerable accumulation of lead was observed in livers, kidneys (cortex) and bones. Highest concentrations of lead in lungs were observed for sheep exposed to traffic but fed with uncontaminated grass. Six months after removal from a source of lead pollution, the lead content of soft organs of sheep had approached, but not reached, background levels. The lead content of bones had not changed appreciably in this time. Edible muscle tissue showed only slight accumulation of lead. It is suggested that offal of animals grazed adjacent to highways should be discarded because of the risk of its finding its way into pet foods which are sometimes consumed by humans.

Cretaceous-Tertiary boundary clays rich in iridium from five sites in Europe and New Zealand were investigated. The clays are found to be 100-10,000-fold-enriched in elemental carbon (mainly soot), which is isotopically uniform and apparently comes from a single global fire. The soot layer coincides with the iridium layer, suggesting that the fire was triggered by meteorite impact and began before the ejecta had settled.

Experiments were carried out on the tolerance to and uptake of copper and cobalt by three members of a phylogenetic series of taxa within the genusSilene from Zaire which were reputed to represent a progression of increasing adaptation to metalliferous soils. Plants studied were the widespread and presumably non-tolerantSilene burchelli var.angustifolia (B), a more tolerant variant of this taxon (E) designated an ecotype, and the metallophyteS. cobalticola (C). Studies on the effects of both metals, singly and in combination, on seed germination, seedling and plant performance and yield, and metal uptake from soil cultures, confirmed in general the sequence B

Biogeochemical prospecting for tungsten was carried out at a mineralised area near Barrytown, New Zealand. The tungsten content of the ash of the shallow-rooted tree ferns Cyathea medullaris and Dicksonia squarrosa correlated well with the concentrations of this element in the soil. Sampling of these species therefore provides a possible method of detecting general soil anomalies and moreover is considerably faster than soil sampling under local conditions. Trend surface analysis of the concentrations of tungsten in the trunks of all species of common large evergreen trees sampled on belt transects, could be used to delineate extensions of known tungsten mineralisation in bedrock, and was to some extent superior to soil geochemistry in this respect.

Herbarium specimens (89) of Rinorea bengalensis collected throughout Southeast Asia, were analysed for their nickel content. Concentrations of up to 17,500 μg/g (dry weight) place this species in the hyperaccumulator (> 1000 μg/g) class. Plants growing over ultrabasic substrates invariably contained over 3000 μg/g Ni. Most major ultrabasic regions in the area covered by this plant's distribution were identified from the nickel content of the herbarium specimens and one previously unrecorded ultrabasic area in West Irian (Indonesia) was pinpointed.

This article reviews the role of three copper-indicating plants in prospecting for minerals in Central Africa. New original data are presented for the Zairean ‘copper flower’ (Haumaniastrum katangense) which has escaped from its original habitat on cupriferous outcrops of the Central African Copperbelt and has been observed on sites of precolonial copper smelters. Excavation of these sites has revealed numerous ceramics and copper crosses, and other items of much archaeological interest. It is evident that phytoarchaeology may be valuable in a much wider context.

Summary Thirty-two Psychotria species from New Caledonia and 178 from other islands of the Pacific Basin were analyzed for nickel in order to identify hyperaccumulators (> 1000 g/g dry mass) of nickel. P. douarrei was the only taxon which possessed this character and contained a mean concentration of 2.24% nickel in its leaves. This is higher than for any other known hyperaccumulator of nickel. Pot trials showed that P. douarrei can grow in substrates containing up to 1% plant-available nickel. It is suggested that P. dourarrei is a neoendemic taxon possibly derived from P. baillonii which occupies complementary ecological niches on non-nickeliferous soils adjacent to the ultramafic substrates supporting P. douarrei. Evolution may have proceeded via an intermediate nickel-tolerant ecotype of P. baillonii which can still be found growing in association with P. douarrei.

The atomic absorption signals obtained from the reduction of arsenic(V) by sodium borohydride solution are strongly dependent on a number of parameters which are examined in this paper. If the arsine produced by sodium borohydride reduction is condensed in a cold trap and then released suddenly, the atomic absorption peak is larger and more reproducible. The procedure is more satisfactory if the borohydride solution is added to the reaction mixture in small aliquots. Peak height depends on the total volume of the reaction mixture and on the carrier gas flow rate. Peak height is also a function of the time elapsed after addition of the final aliquot of borohydride, and increases as the interval between successive aliquots is increased. Optimum conditions established were: initial volume of reaction mixture, 30 mL; 12 mL 3% NaBH4 solution added in 2 mL aliquots at 30 s intervals; carrier gas flow 1.25 L/ min; 60 s time lapse from last addition of borohydride until removal of the cold trap. Under these conditions, linear absorbance-concentration curves were obtained for 0.05–3.0 μg arsenic, with a relative standard deviation of 4.2% at the 2 %g level.

An investigation was made of the silver content of soils, stream sediments, waters and vegetation near a silver mine and treatment plant at Maratoto, New Zealand. Silver in soils showed elevated levels near the treatment plant (due to aerial fall-out), and also in natural vegetation growing over the ore deposits. Pasture soils showed silver contamination derived partly from deposition from ore trucks and partly from flooding by mineralized stream sediments. Silver in pasture species reflected the same pattern. Silver levels in leaves and trunks of Beilschmiedia tawa (A. Cunn.) Benth. et Hook f. ex Kirk showed distinctly different mechanisms of uptake from aerial fall-out and natural uptake by root systems. The silver content of stream waters and stream sediments, though anomalous near the deposits and treatment plant, showed a progressive decrease with increasing distance from the source.

EU-5476 is a new, orally active angiotensin I-converting enzyme (ACE) inhibitor. In vitro, EU-5476 produced a concentration-dependent inhibition of ACE purified from rabbit lung (IC50 = 0.084 μ). Inhibition showed complex kinetics and was reversible as determined by equilibrium dialysis. EU-5476 inhibited plasma ACE in mice (93.8% inhibition at 5 μmol/kg) and produced dose-dependent inhibition of plasma ACE in dogs (ID50 = 2.52 μmol/kg) after oral administration. In acute aortic coarctate hypertensive rats, EU-5476 administered orally produced dose-dependent decreases in blood pressure (ED30 = 0.53 μmol/kg). The magnitude and duration of blood pressure reduction in hypertensive rats were similar to those of plasma ACE inhibition in dogs, suggesting that plasma ACE inhibition per se is one of the mechanisms of the antipertensive action of EU-5476. Comparative studies showed that EU-5476, like enalapril, was more potent and longer acting than captopril in producing plasma ACE inhibition and an antihypertensive response. EU-5476 is a potent and long-acting, orally effective ACE inhibitor potentially useful in the treatment of hypertension.