Chemical Forms Of Metals Research Articles

Speciation and stabilization of some heavy metals in the sediments from drains, Egypt

Speciation has been used to indicate the chemical forms of metals and to measure their distribution in the sediment. Therefore, sequential extraction techniques were used to distinguish between different physicochemical states of metals and give detailed information on mobilization and their transportation. This work aimed to determine the total metals concentrations and their fractionation pattern (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in the sediment samples. Also, solidification/ stabilization processes were used to reduce the mobility of metal contaminants by the addition of an agent that solidifies and then immobilizes the metals. The data showed that metal fractionation is relatively stable under normal conditions except for Cd, Zn, and Mn, which were distributed mainly in the mobile fraction for all samples of Talkha drain, Egypt, while, in Rahway drain, Egypt, all heavy metals were found in the stable form bound to organic sulfide and residual fractions except for, Mn and Zn, which distributed mainly in the unstable form. The data showed that 50% of cement kiln dust was sufficient to reduce the mobility of metals by increasing their percentages in the stable forms.

Arbuscular Mycorrhizal Colonization Alters Subcellular Distribution and Chemical Forms of Cadmium in Medicago sativa L. and Resists Cadmium Toxicity

Some plants can tolerate and even detoxify soils contaminated with heavy metals. This detoxification ability may depend on what chemical forms of metals are taken up by plants and how the plants distribute the toxins in their tissues. This, in turn, may have an important impact on phytoremediation. We investigated the impact of arbuscular mycorrhizal (AM) fungus, Glomus intraradices, on the subcellular distribution and chemical forms of cadmium (Cd) in alfalfa (Medicago sativa L.) that were grown in Cd-added soils. The fungus significantly colonized alfalfa roots by day 25 after planting. Colonization of alfalfa by G. intraradices in soils contaminated with Cd ranged from 17% to 69% after 25–60 days and then decreased to 43%. The biomass of plant shoots with AM fungi showed significant 1.7-fold increases compared to no AM fungi addition under the treatment of 20 mg·kg−1 Cd. Concentrations of Cd in the shoots of alfalfa under 0.5, 5, and 20 mg·kg−1 Cd without AM fungal inoculation are 1.87, 2.92, and 2.38 times higher, respectively, than those of fungi-inoculated plants. Fungal inoculation increased Cd (37.2–80.5%) in the cell walls of roots and shoots and decreased in membranes after 80 days of incubation compared to untreated plants. The proportion of the inactive forms of Cd in roots was higher in fungi-treated plants than in controls. Furthermore, although fungi-treated plants had less overall Cd in subcellular fragments in shoots, they had more inactive Cd in shoots than did control plants. These results provide a basis for further research on plant-microbe symbioses in soils contaminated with heavy metals, which may potentially help us develop management regimes for phytoremediation.

The effects on soil/water/plant/animal systems by platinum group elements

Abstract Emissions of toxic substances such as oxides of carbon, nitrogen, sulphur, and, in addition, aromatic hydrocarbons, aldehydes and heavy metals are the most serious problem of road traffic affecting landscape. Platinum group elements (PGE), which are the main component of the catalyst, are one of the main sources of heavy metals in the environment. Here, we review the way by which emissions and forms of the emitted PGE end up in the environment especially to the soil-water-plant-animal system. The major points discussed are the following: 1) the main sources of PGE emission are automobile exhaust catalysts; 2) hospitals, where platinum is widely used to treat malignant neoplasm, and urban waste water belonging to other important sources of PGE in the environment; 3) soil is one of the most important components of the environment that may be contaminated with platinum metals; 4) phytotoxicity of PGE depends on the following conditions: the concentration of metals in the soil, time of exposure, the chemical form of metal, the chemical composition of exposed soil and plant species; 5) animals are also endangered by the increasing concentration of PGE in the environment. Moreover, we pay our attention to thiol-based mechanisms of how an organism protects itself against platinum group elements.

Speciation study of Cr(VI/III) reacting with humic substances and determination of local structure of Cr binding humic substances using XAFS spectroscopy

Copyright © 2012 by The Geochemical Society of Japan. phenomenon presenting important implications for environmental problems (Wittbrodt and Palmer, 1996, 1997; Kožuh et al., 2000). Reduction-oxidation studies of Cr in soils have mainly targeted estimation of the reduction kinetics and stability constants (complexation capacities), or have addressed the presence of Cr(VI) (Fukushima et al., 1995; Wittbrodt and Palmer, 1995, 1996, 1997; Nakayasu et al., 1999; Kožuh et al., 2000). Information about the detailed chemical structure of Cr in nature is also necessary for complete understanding of toxicity and stability. However, determining a chemical state of Cr during or after a reaction process of Cr(VI) and soils is challenging because the soil system is too complex for speciation studies of Cr. Analysis using X-ray absorption fine structure (XAFS) spectroscopy is effective for determination of a valence state and a chemical form of metals in heterogeneous materials because it yields information with elemental selectivity obtained through Speciation study of Cr(VI/III) reacting with humic substances and determination of local structure of Cr binding humic substances using XAFS spectroscopy

Chemical form of metals in traditional medicines underlines potential toxicity in cell cultures

Mercury (Hg) and arsenic (As) are frequently found in traditional medicines as sulfides, such as cinnabar (HgS) and realgar (As(4)S(4)). There is a general perception that any medicinal use of such metal-containing remedies is unacceptable. An opposing opinion is that different chemical forms of arsenic and mercury have different toxic potentials. To clarify this question, cinnabar, realgar, and cinnabar- and realgar-containing traditional medicine An-Gong-Niu-HuangWan (AGNH), were compared to well-known mercurials (HgS, HgCl(2) and MeHg) and arsenicals (As(2)S(2), As(2)O(3), NaAsO(2), and Na(2)HAsO(4)) for their cytotoxicity in human and rodent cell lines. Cultured cells derived from target organs such as brain (HAPI) and liver (Hep3B, HepG2 and TRL1215) were treated with chemicals for 48 h and cytotoxicity was determined by the MTS assay. MeHg was most toxic with LC(50) of 4-20μM, followed by NaAsO(2) (LC(50), 25-250 μM) and HgCl(2) (LC(50,) 50-100 μM), Na(2)HAsO(4)(LC(50), 60-400μM), As(2)O(3)(LC(50), 30-900 μM), and As(2)S(2) (LC(50), 100-500 μM). In comparison, the LC(50) of realgar ranged from 250 to1500 μM; whereas cinnabar or HgS were approximately 20,000 μM and the toxicity of AGNH was in the range of 1500-8000 μM. Approximately 5000-fold differences exist between MeHg and HgS, and over 10-fold differences exist between NaAsO(2) and As(4)S(4). Chemical forms of metals are important factor in determining their toxicity in traditional medicines, both cinnabar and realgar are much less toxic than well-known mercurial and arsenicals.

Metal speciation in surface sediments of the Vigo Ria (NW Iberian Peninsula)

Total concentrations and chemical forms of metals in surface sediments of the Vigo Ria (NW Iberian Peninsula) were determined following the sequential extraction method proposed by Tessier et al. (1979). Total values ranged from 7 to 14 µgCo g-1, 52 to 76 µgCr g-1, 18 to 82 µgCu g g-1, 136 to 209 µgMn g g-1, 18 to 30 µgNi g g-1, 24 to 112 µgPb g g-1, 62 to 185 µgZn g g-1 and 18 to 34 mg g g-1 for Fe. The distribution of metals is strongly influenced by the presence of urban and industrial centres. A decreasing concentration trend was observed towards (i) the outer-oceanic part of the ria and (ii) the northern shore in the middle part. Cobalt, Cr, Fe, Mn, and Ni were found to be strongly associated with the residual fraction of the sediment (65-78%), whereas Cu is significantly present in the oxidisable phase (34-72%) and Pb and Zn are found in both the reducible (14-49%) and the oxidisable (14-39%) phases. The speciation patterns reflect natural uncontaminated conditions in the outer part of the ria. However, a significant fraction of the Cu, Pb, and Zn in the sediments of the southern margin of the middle part of the ria, which supports most of the population and industrial activities, is present in labile forms, so a potential pollution risk may exist.

Effects of Chloride and Co-Contaminated Zinc on Cadmium Accumulation within Thlaspi caerulescens and Durum wheat

Cadmium is a potentially toxic heavy metal with no known benefit to humans. Soils are the main source of Cd in plants, and plant-derived foods are the main source of Cd in human diets. Cadmium is present in all soils, usually as a trace constituent. The plant availability of Cd in soil is determined by the characteristics that affect the availability of most trace metals. These characteristics include plant species, the concentration and chemical forms of metal in the soil, pH, organic matter content, clay content, its interactions with other elements, and fertilizer practices. In addition, an increase in Cl concentrations in the soil or soil solution was shown to increase Cd concentration in plants in laboratory studies, such as Swiss chard, sunflower, potato, kenaf, sorghum and wheat (Smolders et al. 1997; Hattori et al. 2006). Under field conditions, Cd concentrations in plants were found to positively relate to Cl concentration in soil as well (Norvell et al. 2000; Wu et al. 2002). Chloride is known to reduce soil sorption of Cd, probably due to the fact that chloride forms relatively strong complexes with Cd depending on solution Cl concentration. Chloro-Cd complexation and the resulting improved diffusion of Cd through the soil to plant roots and possibly increased uptake of Cd-chloro complexes are suspected to be the reasons for the Cl effect on Cd uptake (Mclaughlin et al. 1997). Unlike Cd, Zn is an essential nutrient both for plants and animals, but if present in high concentration in plants and animals it can also be highly toxic. It is generally accepted that Zn status in soils and plants plays an important role in Cd accumulation in crop plants. Generally, Zn application decrease Cd uptake and accumulation in plants (Jiao et al. 2004; Zhang and Song 2006), which may be caused by Cd and Zn competivite adsorption in soils and absorption by roots as well as an interaction in the transport system of plant (Hart et al. 2002). However, the effects of Zn application on Cd uptake and accumulation in plants are not consistent. Nan et al. (2002) showed that increases in Zn application enhanced Cd concentration in wheat or vice versa. Similar observations were also made by other researchers (Wu and Zhang 2002). Most of studies under actual field situations, soil environments are often contaminated with multiple heavy metals, such as Cd, Zn, Pb, etc. The study of the Cd accumulation influenced by the interaction between these ions is of practical importance. Durum wheat is an important and valuable crop in many parts of the world that can accumulate Cd to approach or exceed the toxic concentration limits in some places. Durum wheat is a non-accumulator, but Thlaspi caerulescens is a hyperaccumulator of Cd and Zn that can accumulate more than 100 mg Cd kg in their leaves (Baker et al. 1994). Recently, there has been considerable interest in the use of Thlaspi caerulescens as a green technology for phytoremediation of surface soils contaminated with toxic Q. Liu (&) Institute of Soil Science, Chinese Academy of Sciences, 71 East Beijing Road, Nanjing 210008, China e-mail: qliu@issas.ac.cn

Heavy metal speciation in solid-phase materials from a bacterial sulfate reducing bioreactor using sequential extraction procedure combined with acid volatile sulfide analysis

Heavy metal mobility, bioavailability and toxicity depends largely on the chemical form of metals and ultimately determines potential for environmental pollution. For this reason, determining the chemical form of heavy metals and metalloids, immobilized in sludges by biological mediated sulfate reduction, is important to evaluate their mobility and bioavailability. A modified Tessier sequential extraction procedure (SEP), complemented with acid volatile sulfide (AVS) and simultaneous extracted metals (SEM) measurements, were applied to determine the partitioning of five heavy metals (defined as Fe, Ni, Zn and Cu, and the metalloid As) in anoxic solid-phase material (ASM) from an anaerobic, sulfate reducing bioreactor into six operationally defined fractions. These fractions were water soluble, exchangeable, bound to carbonates (acid soluble), bound to Fe-Mn oxides (reducible), bound to organic matter and sulfides (oxidizable) and residual. It was found that the distribution of Fe, Ni, Zn, Cu and As in ASM was strongly influenced by its association with the above solid fractions. The fraction corresponding to organic matter and sulfides appeared to be the most important scavenging phases of As, Fe, Ni, Zn and Cu in ASM (59.8-86.7%). This result was supported by AVS and SEM (Sigma Zn, Ni and Cu) measurements, which indicated that the heavy metals existed overwhelmingly as sulfides in the organic matter and sulfide fraction. A substantial amount of Fe and Ni at 16.4 and 20.1%, respectively, were also present in the carbonate fraction, while an appreciable portion of As (18.3%) and Zn (19.4%) was bound to Fe-Mn oxides. A significant amount of heavy metals was also associated with the residual fraction, ranging from 2.1% for Zn to 18.8% for As. Based on the average total extractable heavy metal (TEHM) values, the concentration of heavy metals in the ASM was in the order of Cu > Ni > Zn > Fe > As. If the mobility and bioavailability of heavy metals are assumed to be related to their solubility and chemical forms, and that they decrease with each successive extraction step, then the apparent mobility and bioavailability of these five heavy metals in ASM increase in the order of Cu < As < Ni < Fe < Zn. The SEM/AVS ratio was less than one in eight replicate ASM samples, indicating that the ASM was non-toxic with regards to having a low probability of bioavailable metals in the pore water.

Optimization of a Sequential Extraction Scheme for Speciation of Metals in Fine Urban Particles

A sequential extraction procedure fractioned in four steps was optimized with the purpose of improving a previous scheme for determining the chemical forms of metals in fine airborne particles. The optimization was tested on synthetic samples and then confirmed on real samples of fine particles, optimizing the type of reagent, its concentration, pH, temperature and extraction time. Synthetic samples were prepared in the laboratory with compounds of reagent grade. The analytical method applied consisted of extracting the metals from each sample in a rotator with each type of reagent under different conditions of the parameters and then centrifuging before measuring by ICP-AES. The improved and previous scheme was checked on real samples and the differences were significant in the percentages of the soluble chemical forms in the improved scheme (5.2% in front to 22.0% for Pb, 27.0% in front to 50.0% for Cd and 32.4% in front to 9.0% for Ni) from 55.6, 0.23 and 1.48 ng m− 3 of total metal concentrations respectively.

Quantitative determination of cerussite (lead carbonate) by X-ray powder diffraction and inferences for lead speciation and transport in stream sediments from a former lead mining area in Scotland

Most current investigations of sites contaminated with heavy metals (e.g. Pb, Zn, Cu) emphasise the importance of determining the amounts of physical and chemical forms of metals rather than just the total amounts present. Chemical extraction techniques used for this purpose are inevitably operationally defined. A more direct approach to the identification of crystalline forms can be made by mineralogical techniques such as X-ray powder diffraction (XRPD), but quantitative determination of a particular form is not often attempted. Recent advances in methods of analysis and sample preparation for XRPD mean that it is now a relatively simple matter to obtain quantitative XRPD data. Here, it is applied to the quantitative determination of the forms of Pb in different size-fractions of stream sediment samples from Leadhills/Wanlockhead, SW Scotland, an historic Pb mining area. Comparison of the XRPD analyses with determinations of Pb by atomic absorption spectrophotometry demonstrates that a large proportion of the Pb present in the stream sediments is in the form of cerussite (PbCO 3). Furthermore, the cerussite tends to be concentrated in the silt fraction and is even a minor component of the clay-size fraction. However, quantitative analysis of fractions <6 μm indicates that cerussite alone cannot account for all the Pb in this size range. Indirectly, this result suggests that Pb adsorbed to clay minerals, organic matter and/or amorphous Fe and Mn oxides may be proportionally more important for the <6 μm materials. Sediment in this size range, however, typically accounts for no more than 1% by weight of the total stream bed sediment samples collected in the study area. In relation to its size distribution, the mobility of Pb within the wider environment is most likely to occur principally through physical transport of fine particles.

Copper amendments and soil ph affect distribution of different chemical forms of metals and their uptake by Swingle citrumelo seedlings

This study was conducted to evaluate the effects of various rates of Copper (Cu) amendments (as CuSO4.5H2O at either 0, 25, 50, 100, 200, or 400 mg Cu kg‐1) to soils with different pH values on the distribution of various chemical forms of Zinc (Zn), Iron (Fe), Manganese (Mn), and Aluminum (Al) in soils and their uptake by Swingle citrumelo citrus rootstock seedlings. The soils included Myakka fine sand (pH 5.70), Candler fine sand (pH 6.45), and Oldsmar fine sand (pH 8.16). The chemical forms of metals evaluated in this study included exchangeable, sorbed, organically bound, precipitated, and residual forms. An increase in Cu rates, lowered the pH in the Myakka and Candler fine sands, but not in the Oldsmar fine sand. This, in turn, resulted in an increase in the proportion of the readily soluble forms (the exchangeable + sorbed forms) of Zn and Mn, and decreased that of Fe in the Myakka and Candler fine sands. In those two soils, the organically bound forms of Zn, Fe, and Mn decreased with an increase in Cu rates. However, the proportion of readily soluble forms was not significantly influenced by increasing Cu rates in the Oldsmar fine sand. The total content of Zn, Fe, and Mn in citrus roots and that of Zn and Fe in the leaves, significantly decreased with an increase in Cu rates in the Myakka and Candler fine sands. In the Oldsmar fine sand, Cu rates through the entire range had no significant effects on the total contents of Zn, Fe, and Mn in the leaves or in the roots of Swingle citrumelo rootstock seedlings.

SEASONAL VARIATIONS AND CHEMICAL FORMS OF HEAVY METALS IN SOILS AND DUSTS FROM THE SATELLITE CITIES OF SEOUL, KOREA

This research investigated heavy metal pollution of soils and dusts in two representative satellite cities of Seoul, Korea and studied the seasonal variations in metal concentrations through the rainy season and the chemical forms of metals using a sequential extraction analysis. The metal dispersion pattern was illustrated to match with urban structure. Soil and dust samples were collected from the cities of Uijeongbu and Koyang, which are the northern and northwestern satellite cities of Seoul (the capital), before and after rainy season. Concentrations of Cu, Pb and Zn were higher than those of the world averages for soils, and their levels decreased after rain, particularly in highly contaminated samples. Relatively high pH values were found in roadside soils, but no seasonal variation was found after the rainy season. The three metals (Cu, Pb and Zn) in soils and dusts were associated with various chemical fractions of soils and dusts as distinguished by the sequential extraction scheme, and a strong similarity of metal association between soils and dusts was found, which indicates that airborne dust may be a principle source of soil contamination. Copper is uniformly distributed, and Pb is largely associated with the reducible phase. There is an appreciable proportion of total Zn in the exchangeable/water-acid soluble fraction. After the rainy season, the most soluble fractions in soils and dusts were leached away. In terms of mobility and bioavailability of metals in soils and dusts, the order Zn >> Cu > Pb is suggested. Geographical variations of total metals corresponded well with urbanised areas of cities, especially the industrial complex and major motorways.

Copper Transfer and Influence on a Marine Food Chain

Copper is an essential element, required for normal growth by all plants and animals; and a regular constituent in the environment (Lewis and Cave 1982; Lewis 1994). This heavy metal is an essential micronutrient that at higher concentrations can be deleterious to algae and other aquatic biota (Chang and Sibley 1993). Copper toxicity to algae depends upon the individual species, their physiological and environmental conditions, and the chemical forms of metal in the medium (Sunda and Gullard 1976). When copper is accumulated by phytoplankton it can be transferred and may produce toxic effects on zooplankton (Wikfors and Ukeles 1982). Different species of microalgae present different capacities of resistance to copper. Cyanophyceae pre-cultured in a Cu-enriched medium (635 {mu}gCu{center_dot}L{sup {minus}1}) showed an EC{sub 50} that could reach 318 {mu}gCu{center_dot}L{sup {minus}1} for Plectonema radiosum and 339 {mu}gCu{center_dot}L{sup {minus}1} in Phormidium sp. (Takamura et al. 1990). Scenedesmus, Selenastrum and Chlorella were reported able to accumulate copper and other metal ions with an efficiency of 67-98% (Brady et al. 1994). Also, Dunaliella resisted concentrations form 0.38 mgCu{center_dot}L{sup {minus}1} (D. minuta) up to 50.8 mgCu{center_dot}L{sup {minus}1} (D. acidophila), depending on the pH of the medium (Grimmler et al. 1991). One the microalgae are copper-enriched, themore » copper that is part of the cell can be transferred to the surrounding water and to its predator producing uncertain effects. This study observed the effect of copper on the growth of Dunaliella tertiolecta and Isochrysis galbana that are currently used as food for hatchery-grown scallop larvae (Argopecten purpuratus). We observed the path of copper form the water column into the microalgal cell and the effect of copper-enriched food on the scallop larvae. 16 refs., 3 figs., 2 tabs.« less

Impacts of mining on the environment; some local, regional and global issues

The mining, processing and utilisation of metals dates back to Roman times and earlier with extensive developments in many parts of the world by the eighteenth and nineteenth centuries. Many mineralised areas are no longer worked leaving a legacy of dereliction and contaminated land and drainage. This paper discusses the sources and dispersion of metals from mining and smelting activities, factors influencing their pathways into the foodchain and potential impacts on plant, animal and human health. The importance of mineral and chemical forms of metals in soils is discussed in relation to their bioavailability. Reference is made to research in the U.K., Greece and Brazil.

Evaluation of “labile” metal in sediments by anodic stripping voltammetry

A procedure for determining the “labile” metal content of contaminated sediments (in different chemical environments) has been critically examined. The sediments were extracted overnight with different chemical solutions and the suspensions were analysed by differential pulse anodic stripping voltammetry. The extractants used have been recommended for soil/sediment speciation schemes, and by examination of the suspensions directly in the ASV cell, errors due to re-adsorption of released metal ion were minimized. The existence of different chemical forms of metal was signified by changes in peak shape and position or by the appearance of additional peaks. With complexing agents present the peak size was pH-dependent. The limitations of the ASV/suspension analysis technique have been carefully evaluated by using ten different extractants and seventeen sediments. The “lability” results obtained have been compared with the values obtained from a cation-exchanger transfer procedure. For characterizing the lability behaviour of the metal contents of sediments, preliminary extraction into a minimum of four base solutions is advisable, e.g., 0.02 M nitric acid (low-pH labile); hydroxylamine in acetic acid (reducing conditions); acetic acid/acetate buffer (weakly sorbed and carbonate-bound) and 0.05 M calcium chloride (exchangeable fraction at natural system pH), where the terms in parentheses describe the character of the fraction. The results are critically compared with those obtained by atomic-absorption analysis of the extracts and with those obtained by an earlier ion-exchange fractionation scheme. The advantages and limitations of the ASY systems are discussed.

Eco-biotoxicology of chemical pollutants.

The major toxicological problem today is to establish a useful method to cope with a low level and prolonged pollution. The toxicological method under such circumstances should include ecotoxicology and biotoxicology as well as classical toxicology, and is named as eco-biotoxicology. This method includes not only investigations on kinetics and levels of chemicals in the environment, human reaction and adaptation to chemicals or biophysiological and pathophysiological clarification of the effects, but also the establishment of countermeasures to prevent health hazards from chemicals, including biological monitoring and development of exposure parameters. The followings were the results recently obtained in our laboratory in support of the object of eco-biotoxicology. 1. Two low-molecular-weight chromium binding substances were purified from the liver of dogs. Chromium bound to them showed a lower toxicity and higher rates of urinary excretion than inorganic chromium compounds. A low-molecular-weight nickel binding substance was also purified from the liver of rats. Nickel bound to it showed a lower cytotoxity, but a higher malignant transformation induction of cultured cells than inorganic nickel compounds. These results indicate that chemical form of metals and binding protein in the body are important factors in their toxicity. 2. Triphenyl and tributyltins showed to inhibit insulin release from pancreas, collagen-induced aggregation of platelets, O2-production and chemotaxis of leukocytes, histamine release from mast cells, etc. A common mechanism seemed to be an inhibition of the stimulus-response coupling in the cell membrane. 3. Carcinogenic heterocyclic amines were measured in food and biological materials by a newly developed method. Their levels in plasma of uremic patients were higher than normal subjects and decreased by the treatment with hemodialysis. 4. Safety evaluation of bis (tri-n-butyltin) oxide (TBTO) in fishes was carried out according to a toxicological approach. Acceptable daily intake of TBTO in food was estimated to be 1.6 μg/kg/d.

Pathophysiological Approach to the Study of Matal Toxicity (Panel Discussion) (Proceedings of the 10th Symposium on Environmental Pollutants and Toxicology)

Environmental toxicology of metals, like that of other chemicals, consists of ecotoxicology and biotoxicology. Among the biotoxicology, pathophysiological approach, along with toxicological approach, is of particular importance for understanding effects of metals on human health and establishing measures to cope with them including biological monitoring and development of exposure parameters and preventive methods. Experiments have been carride out on chemical biology of chromium and clinical biochemistry of organic tin compounds. The aim of these studies is to demonstrate and evaluate the pathophysiological approach in the study of metal toxicity. Recent results in our laboratory are as follows. 1. Chemical toxicology of chromium. Two low-molecular-weight chromium-binding substances, LMCrI and II, were purified from the liver of dogs. Chromium bound to them showed a lower acute toxicity and higher rates of urinary excretion and renal clearance than potassium dichromate (VI) and chromium (III) chloride. The results together with other findings indicate that LMCrs play an important role in the detoxification and excretion of chromium in mammals. They also show that chemical form of metals and binding protein in the body are important factors in metal toxicity. 2. Clinical biochemistry of organic tin compounds Triphenyltin and tributyltin have been shown to inhibit insulin release from pancreatic islets, subsequently inducing diabetic lipemia due to insulin deficiency. The organic tins also inhibited collagen-induced aggregation and ATP secretion of platelets. Furthermore, they showed a dosedependent inhibition of O2- production, O2 consumption and degranulation of leukocytes. These results indicate that organic tins affect a common mechanism of the stumulus-response coupling in the cell membrane.

Dredging of contaminated sediments in the weser estuary: Chemical forms of some heavy metals

Abstract Concentration and chemical forms of metals in bottom sediments and dredged mud of the Weser Estuary were studied. The sediments with the highest metal contents are found in the harbour basins of Bremen and in the mud shoal near Nordenham. Association types of the metals can be divided into 2 groups: metals with relatively high potential of mobilization, such as Cd, Zn, Mn, and Ni and those that are strongly bound on particles ‐ Cr, Cu, Pb and Fe. An estimation of the bioavailability of these metals based on chemical extraction studies is relevant to problems encountered during disposal of dredged materials.

Effects of decreased pH on marine organisms

Sea water scrubbing of flue gas may result in a significant pH decrease in the waters of coastal areas with restricted dilution capacity. A review of the literature on pH tolerance of marine organisms indicates that there is little evidence of harm caused by decrease of 0.5–1.0 pH units. However, few long term or life cycle studies have been conducted. As pH may influence seawater chemistry in several important ways, notably the carbonic acid equilibrium, chemical form of metals, and the characteristics of dissolved substances, it is concluded that pH tolerance deserves more interest from marine biologists than it has received hitherto.

The infrared spectroscopic study of metals intruded into a silica framework

The chemical form of metals in a silica framework was studied by infrared spectrescopy. Specimens were prepared by heating vitreous silica with metals during periods ranging from several to 200 hr. The intrusion patterns of metals were classified into three types: silicate, metallic suspension and coordination. The silicate types are characterized by the shift of the 1110 cm −1 v 3 peak to lower wave numbers and development of the 1030 and/or 950 cm −1 peaks. Metallic suspensions show the 625 cm −1 v 2 peak which became i.r. active. Cobalt is uniquely classified into coordination type. It shows many peaks at 500–1000 cm −1, which may be assigned to some new bonds between silica and metal. A short discussion is given about the chemical form of silica inclusion in steel on the basis of the above results.