Levels Of Several Metals Research Articles

Bioavailability and crop uptake of trace elements in soil columns amended with sewage sludge products

In order to assess the potential impact of long-term sewage sludge application on soil health, the equivalent of about 25 years of agronomic applications of low-metal (`EQ') sewage sludge products were made to greenhouse soil columns. After a 6-year period of `equilibration', during which time successive crops were grown with irrigation by simulated acid rain, the plant-available quantities of trace elements were estimated in the soils by extraction with 0.01 M CaCl2 at 90 °C, and measured directly by uptake into a crop of red clover (Trifolium pratense L.). Soil pH had a strong influence on the level of extractable and plant-available metals, and because the tested sludge products affected soil pH differently, pH was directly factored into the comparison of different sludge treatments with controls. CaCl2-extractable levels of several metals (Cu, Zn, Mo), sulfur and phosphorus were found to be higher in the soils amended with organic-rich sludge products than in the control soils. However, extractable Cd and Ni were not significantly elevated by the sludge amendments, presumably because of the low total loading of these metals. Copper, Zn and Mo applied in the form of sludge ash had low soil extractability, suggesting that these trace metals were trapped in high-temperature mineral phases formed during sludge incineration, and resisted subsequent weathering in the soil environment. Extractable soil metals in the alkaline-stabilized sludge treatment were also generally low. Phytotoxicity from the sludge metal loadings (Zn≤125, Cu≤135 kg/ha), was not clearly indicated as long as soil pH was maintained in the 6–7 range by lime amendment. Nevertheless, unexplained depressions in yield were noted with some of the sludge products applied, particularly the dewatered and composted materials. On limed soil columns, the most consistent effect of sludge product amendment on red clover composition was a marked increase in plant Mo.

A Question of Dose

M etals have been adopted by biological systems because of their catalytic versatility, but their reactivity can also make them toxic at low concentrations. Hence they are classified as nutrients or poisons. But this is a misleading division, because many enzyme catalysts have reaction centers with diverse and variable metal associates. Such flexibility is useful for organisms living in metal-poor environments that may have to take what they can get, but it is potentially dangerous. Thus, the availability of trace metals may govern an organism's nutritional strategy in a particular environment. This special issue explores the double-edged nature of metal chemistry, how it can be exploited for our benefit, and the consequences if it is not tamed. ![Figure][1] CREDIT: PHOTODISK Transition metals, such as iron and copper, with their multiple oxidation states are vital for the cascades of electron transfer reactions that are characteristic of cellular processes. Without iron, life on our planet would be unrecognizable. It is the key to oxygen transport, photosynthesis, nitrogen fixation, and respiration in most modern organisms. How the complexity and organization of these processes originated is a matter of conjecture, but the traces of these beginnings may lie in the modern preponderance of iron-sulfur clusters in key enzymes (Rees and Howard, p. [929][2]). Normal, healthy cells may concentrate high levels of several metals, and to avoid poisoning, metals must be sequestered and transported by specific proteins. Ensuring easy and rapid transfer of such enveloped metals to their target proteins requires unusual coordination chemistry (Finney and O'Halloran, p. 931). Metals in cells are substantially influenced by cell signaling networks [see this week's STKE Focus issue ( )]. For example, nitric oxide affects the regulation of iron metabolism in response to inflammation (Bouton and Drapier in [STKE][3]). Zinc is also emerging as a transynaptic messenger, and zinc-sensitive dyes and imaging techniques have galvanized neurobiology (Li et al. and Frederickson in [STKE][3]). Complexation in a larger nontoxic molecule is also the key to exploiting metal chemistry for therapeutic purposes (Thompson and Orvig, p. [936][4]). But there is still a fine line between poisoning and salvation. Despite Paul Ehrlich's pioneering use of the arsenic-containing drug salvarsan to treat syphilis, arsenic is now more known for its contamination of borehole water supplies in southern and central Asia. Although those water supplies are no longer contaminated by pathogens, other bacteria capable of metabolizing arsenic appear to be involved in mobilizing the poison into the groundwater (Oremland and Stolz, p. 939). In contrast, the ubiquity of other metals in the environment sometimes makes it hard to discern their impact. For example, manganese is an essential trace element in the human diet, but when inhaled in mines it can trigger psychotic behavior and Parkinson's-like symptoms; it's unclear, however, whether low-dose exposures from car exhausts are harmful (see the News story by Kaiser, p. 926). In the oceans, metals are vanishingly scarce. Despite this dearth, microscopic plankton are the source of more than half the planet's primary production via metal-driven reactions. To be productive in these metal “deserts,” special salvage molecules have to be employed by planktonic organisms, but identifying such agents in the vastness of the open ocean is challenging. In this environment, both microorganisms and scientists are operating at the limits of what is biologically and experimentally feasible (Morel and Price, p. 944). In the world of the “metallome,” it is indeed a narrow path between poison and nutrient. [1]: pending:yes [2]: /lookup/doi/10.1126/science.1083075 [3]: http://www.stke.org/ [4]: /lookup/doi/10.1126/science.1083004

Development of a metallothionein based heavy metal biosorbent.

The potential utility of a recombinant E. coli expressing the Neurospora crassa metallothionein gene (NCP) as a heavy metal biosorbent was investigated. It was shown that the NCP was capable of efficiently removing low levels of several metals (including cadmium, lead, and mercury) from solutions. The reusability of the NCP was demonstrated through 5 cycles of metal binding, stripping with dilute acid, and regeneration of the binding sites with out any adverse effect on the metal binding activity. The NCP was successfully encapsulated in alginate and acrylamide without any inhibitory effect on its metal uptake activity. Furthermore, the metal uptake activity of the NCP was shown to be metabolism independent and resistant to solvents and other compounds (eg. polyaromatic hydrocarbons) which are often present along with heavy metals in waste waters thereby creating the potential for non-viable, encapsulated cells to be used.

Heavy Metals in Tissues of the Norway LobsterNephrops Norvegicus: Effects of Sex, Size and Season

Abstract Concentrations of mercury, cadmium, copper, zinc and iron were determined in the carapace, hepatopancreas, gills, tail muscle, ovary and eggs of 288 Norway lobsters, Nephrops norvegicus, caught in the Clyde Sea area, south of the Isle of Cumbrae, Scotland. Metal levels in males and females were examined separately in relation to size and the season in which the animals were caught. Cadmium, copper and zinc concentrations were highest in the hepatopancreas whereas mercury and iron concentrations were highest in the gill. Levels of metals showed variations between months, with highest levels tending to occur during molt. Metal levels were influenced by lobster size with pronounced size-related increases in mercury levels in the tail muscle and cadmium levels in the hepatopancreas. Levels of several metals in the various tissues differed between the sexes.

Correlation clusters in the accumulation of metals in human scalp hair: effects of age, community of residence, and abundances of metals in air and water supplies

Scalp hair samples taken from 122 children and 27 adults from three native Indian villages in northern Alberta, Canada were analyzed for 32 metals, in an attempt to tract industrial pollution into the human population. One of the villages has been exposed since 1967 to increased levels of several metals due to its proximity to the world's first two oil sands petroleum extraction plants (Suncor and Syncrude), which release large amounts of metals into the environment. Metal-enriched particulates are emitted at a rate of 547–780 kg h −1 for Suncor, and 713–1067 kg h −1 for Syncrude. To test the hypothesis that hair content reflected accumulation of environmental metals, water and aerometric samples were collected and analyzed for their metal content. These analyses demonstrated that elevated levels of nine metals in hair from children in one of the control villages (Garden River) are (with the exception of Al) correlated with increased levels of metals in water and air. Moreover, increased levels of Cu, but lowest levels of all other metals were found in hair and environmental samples from one control village (Fort Chipewyan). Correlation matrices for metals in the hair samples revealed three sets of highly intercorrelated metals (‘correlation clusters’): (i) Pb/Cd; (ii) Al/V/Fe; (iii) Ca/Mg/Sr/Ba. These groups of metals were significantly intercorrelated ( r > 0.6, p < 0.001) in the total population, and in both children and adults, or both males and females, as well as when the population was compared according to community of residence. The robustness of the clusters is particularly noteworthy in view of large differences in the proportions and absolute amounts of the various metals in hair from children in the three villages. Plots of metal levels in hair as a function of age of subject reveal a dramatic decrease in concentrations of Al, V, and Fe during the first years of life. The high levels of Al and V in hair from very young children may reveal a lower selectivity in metal absorption, and a higher risk of toxicity during a period of rapid growth when need for nutritionally essential metals is particularly high.

Role of epidemiologic studies in deriving drinking water standards for metals.

Epidemiological investigations are shown to have contributed in a significant way to our understanding of the potential adverse health effects of drinking water with elevated levels of several metals. Particular emphasis is given to an assessment of the epidemiological investigations concerned with characterizing the health effects of exposure to elevated levels of arsenic and sodium in drinking water.

Role of Epidemiologic Studies in Deriving Drinking Water Standards for Metals

Epidemiological investigations are shown to have contributed in a significant way to our understanding of the potential adverse health effects of drinking water with elevated levels of several metals. Particular emphasis is given to an assessment of the epidemiological investigations concerned with characterizing the health effects of exposure to elevated levels of arsenic and sodium in drinking water.

Examination of bioaccumulation and biomagnification of metals in a precambrian shield lake

This paper reports on a comprehensive examination of metal levels at various trophic levels within an undisturbed Precambrian shield lake ecosystem. Concentrations of 21 naturally occurring elements (Hg, Cu, Al, Ba, S, Ni, Cd, Ca, Be, Zn, P, Pb, Mg, Sr, Fe, V, Mo, Mn, Ti, B, Cc) were measured in sediments, clams, fish, birds and mammals. Mercury was the only element to exhibit biomagnification in both aquatic and terrestial food chains. The levels of several metals were elevated in fish-eating birds relative to concentrations observed in the fish. Mercury was the only metal which accumulated in muscle tissue with increased age and size of all fish species tested. The concentrations of a few other metals were correlated to fish length, but these relationships were not consistent between species.

Uranium and plutonium in hair as an indicator of body burden in mice of different age and sex.

The comparatively recent development of analytical techniques of great power and sensitivity has permitted investigators to establish correlations for ingestion and elemental hair levels of several metals from differing environmental exposures (e.g. YURACHEK et al. 1969, EADS & LAMBDIN 1973). Ease of collection, storage and analysis of human hair, together with its potential as the "recording filament" (STRAIN & PORIES 1966) to reveal retrospective information about an individual and his exposure, has increased its popularity as a forensic biopsy and autopsy material. For some trace elements, levels in hair have been examined forpossible applications in assessing nutritional status, medical diagnosis and the determination of both acute and chronic exposure to toxic elements. The entire topic of trace metals in human hair has been discussed in a recently published book (VALKOVIC 1978). However, while some authors such as KLEVAY (1970a,b) and KELLO & KOSTIAL (1978) have found positive correlations between plasma and hair elemental concentrations for particular population groups, others (e.g. DEEMING & WEBER 1978) could find no correlation between plasma and hair levels, when they are related to diet, age and sex. As part of a program to develop alternative bioassay techniques for potentially occupationally exposed uranium and plutonium workers (BENTLEY & WYATT 1980) hair is being examined as a potential practical biological dosimeter for these elements. For uranium, the results of toxicity (LD50), organ deposition and metabolic animal studies (mainly conducted in the wartime Manhattan Project) are such that quantitative comparisons are not possible. In many reported results, no reference is made to diet, age, sex or strain of the animal used although the importance of these parameters for uranium had been documented in early work (e.g. JACKSON 1910, VERNE 1931). For intraperitoneall y injected rats, an age-dependent increase in acute

HEAVY METAL ACCUMULATION BY SOME VEGETABLE CROPS GROWN ON SEWAGE-SLUDGE-AMENDED SOILS

The use of sewage sludge on vegetable gardens is a public health concern. A growth chamber experiment was employed to investigate the effect of sewage sludge application on the copper, zinc, lead and cadmium content of lettuce, carrot and pea crops. No yield reduction or other toxicity symptoms were noted, although tissue levels of several metals were elevated. There were small increases in copper in the three vegetables, but zinc and cadmium increased considerably with sludge application. The higher Zn levels present no problem, but the higher Cd levels are undesirable. Cadmium uptake by vegetables and the increased dietary intake of Cd should be considered when sewage sludge is used on vegetable gardens.

Nitrification in soil treated with domestic and industrial sewage sludge

Dried sewage sludge from either predominantly domestic or industrial sources was incorporated into soil at rates of 0, 1, 4 or 16 mg/g and the soils were incubated with or without the addition of 100 μg/g NH 4 + - N and 30° C. Samples were taken at weekly intervals for six weeks and analysed for NH 4 + - N and ( NO 3 − + NO 2 −) - N At the two highest rates, industrial sludge reduced nitrification during the first three to four weeks of the experiment, with the highest rate completely inhibiting nitrification for the first two weeks. At the highest rate, the domestic sludge reduced nitrification only slightly. Analyses showed that the industrial sludge contained higher levels of several metals, particularly Zn, Cd and Pb. It was concluded that reduced nitrification at the high rates of industrial sludge was caused by these metals. This conclusion was supported by the finding that nitrification was inhibited in soils treated with 16 mg/g of domestic sludge which had been treated with inorganic salts to give concentrations of metals comparable with those in the industrial sludge.