Degree Of Metal Enrichment Research Articles

Heavy Metal Contamination in Soil and Health Risk Assessment through Onion Consumption in Mojo and Koka, Ethiopia

The objective of this study was to determine the concentration of heavy metals in the soil and horticultural crops grown under irrigation in the Mojo and Koka sites in Oromia, Ethiopia, and to evaluate the potential health risks that these metals may cause to consumers. For this investigation, a total of 50 onion (Allium porrum L.) and 50 soil samples were gathered. The content of heavy metals was measured using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) after the samples were digested using microwave-assisted digestion. The mean concentrations of examined trace elements in onion (mg/kg) were found in the range of 0.80 to 0.95, for As 1.77 to 0.91 for Sn, 2.09 to 1.49 for Pb, 12.29 to 7.31 for B, 13.85 to 12.33 for Zn, 0.34 to 0.25 for Cd, 1.83 to 1.78 for Hg, 11.29 to 7.54 for Cu, 0.83 to 0.78 for Ni, 0.34 to 0.31 for Co, 78.39 to 42.19 for Fe, 17.03 to 11.56 for Mn, and 1.03to 1.02 for Cr. Given that the average levels of Pb, Hg, Cd, and As in onions at both irrigation sites surpassed the upper limit of allowable levels established by the joint FAO/WHO commission. These metals’ concentrations in soil are found to be within acceptable bounds. As compared to other literatures, their concentration exceeded in both irrigation sites. According to the metal pollution load index, the overall pollution load of trace metals, including As, Pb, Cd, and Hg, was found to be moderately higher in both irrigation locations for the majority of the onions under study. The results, which were computed using an adult consumer’s food intake, indicated that the Pb and Hg dietary exposure levels were much higher than the daily intake amounts that were considered tentatively tolerated. The soil-to-onion transfer factor showed that whereas Fe has a strong sorption to the soil colloids, metal Cu is comparatively poorly maintained in the soil. The degree of metal enrichment in soils and sediments is higher than in other literature, according to the soil pollution indices. Thus, swift action is needed to stop the issue and guarantee public safety along the food system’s supply chain.

Heavy metal contamination and health risk assessment of horticultural crops in two sub-cities of Addis Ababa, Ethiopia

This particular study was aimed to establish the level of heavy metals in different horticultural crops cultivated by irrigation and the soil in two sub-cities of Addis Ababa, Ethiopia, and quantitatively assess the health treat they pose for the consumer. A total of 151 vegetable samples comprised of lettuce (Lactuca sativa), cabbage (Brassica oleracea var. capitate), cucumber (Cucumis sativus), potato (Solanum tuberosum), parsley (Petroselinum crispum), Swiss chard (Beta vulgaris subsp. vulgaris), beetroot (Beta vulgaris), green onion (Allium porrum L.) and 28 soil samples were collected for this study. Six toxic elements were analyzed using microwave plasma atomic emission spectroscopy (MP-AES) after microwave assisted digestion of the samples. The concentrations of examined trace elements in vegetables (mg/kg) were found in the range of 5.50–93.00 for zinc; below detection limit (BDL)− 18.50 for copper; BDL-2.50 for nickel; BDL-17.00 for lead; 5.00–4256.50 for manganese and 22.00–8708.00 for iron. Considering the mean Pb content values, all vegetables exceeded the maximum permissible level set by the joint FAO/WHO commission in both irrigation sites. In case of Mn parsley, swiss chard, and green onion all from site two exceeded the maximum allowable values. With the exception of potato from irrigation site one, all vegetables exceeded the maximum permissible limit set for Fe concentration and out of which parsley, swiss chard, and green onion, all from site two, exceeded by more than double amount. The same trend is observed for the concentration of Mn and Fe in the soil samples. In fact, in both irrigation sites their concentration exceeded the allowable limits set by United Nation Environment Program (UNEP) for agricultural soils. The metal pollution load index revealed that in most of the vegetables studied the overall pollution load of trace metals were higher in Kolfe Keranyo irrigation site. The risk assessment study using indices like estimation of daily/weekly dietary exposure, hazard quotient and metal pollution load index all suggested consumption of the studied vegetables poses a significant health risk for the consumer. For adults the calculated target hazard quotient for the trace element Pb is higher than 1 (one) for all of studied vegetables ranging from 11.086 (cucumber) to 17.881 (beetroot) with a 98.216% and 98.464% contribution to the hazard indices, respectively. For a child consumer, Mn showed a higher target hazard quotient vales ranged from 0.0107 (cucumber) to 0.0495 (green onion) with a 70.86% and 88.85% contribution to the total hazard indices, respectively. The soil pollution indices also indicated that the degree of metal enrichment in soils and sediments are higher than the allowable limits. Therefore, a prompt action is required to curb the problem and ensure the public safety along the food system line.

Trace and rare earth element geochemistry of the black and grey shales of the Calabar Flank, Southeastern Nigeria: constraints on the depositional environment and the degree of metal enrichment

This study focuses on the trace and rare earth elements (REE) geochemistry of the Nkporo and Ekenkpon Shales of the Calabar Flank. The main aim is to infer their depositional environment and the degree of their metal enrichment. The shale samples were analyzed using inductively coupled plasma mass spectrometry. The results indicated that the mean concentrations of K, Na, and Fe in Nkporo and Ekenkpon Shales are 1.45, 0.4, and 4.17 wt%, and 1.11, 0.44, and 5.42 wt%; respectively. The Nkporo Shale is enriched with the following trace elements; P > Mn > Sr > Ba > Zn > Ce > Rb > Zr > V>Cr > Ni and depleted in the following trace elements; Ta > Ge > Sb > Bi > Cd > Ag > Te > In > Hg. While the Ekenkpon Shale is enriched with the following trace elements; P > Mn > Ba > Sr > V>Ce > Zr > Rb > Cr > Zn > Ni and depleted in; Sb > Ge > Bi > Ag > Ce > Te > In > Hg. The concentration of redox-sensitive elements such as V, Ni, Mo, U, Cu, Cr, Re, Cd, Sb, Ti, Mn, and their ratio V/Mo and U/Mo in the black and grey shale samples show different patterns. The REE obtained from the Nkporo and Ekenkpon Shales were PAAS normalized. The Nkporo Shale showed a slightly flat light rare-earth element (LREE), middle rare-earth element (MREE), and heavy rare earth element (HREE) pattern enrichment. Ce/Ce* ranges from 0.95 to 1.09 in Nkporo Shale and 0.67 to 1.40 in Ekenkpon Shale. The Ekenkpon Shale showed a slight LREE, MREE enrichment, and depleted HREE patterns. The Mn contents and U/Mo ratio in Nkporo and Ekenkpon Shales suggests a poor oxygen transitional environment. The V/Mo and V/(V + Ni) ratios indicated that the Nkporo shales were deposited in an anoxic to suboxic conditions and Ekenkpon shales were also deposited under an anoxic to suboxic conditions. The V/Ni ratio indicated that the organic matter in the Nkporo shale is terrigenous while that of the Ekenkpon shales are both terrigenous and marine in origin.

Occurrence and risk assessment of heavy metals in sediments of the Xiangjiang River, China.

Sediment samples were collected from 22 typical metal-polluted sections along the Xiangjiang River (XJR). Spatial distribution and speciation characteristics of heavy metals in sediments of XJR were determined. Furthermore, ecological risk and enrichment degree of metals were assessed by different indices. The results showed that combined metal pollution occurred in sediments of XJR, with content range of Cd, Pb, Zn, Cu, As, Mn, Cr, and Hg reaching 2.95-29.15, 30.93-235.83, 61.50-3771.11, 9.56-81.81, 3.93-46.28, 774.83-8700.72, 10.64-65.16, and 0.13-5.09mgkg-1, respectively. Pollution levels increased in period of industrialization but decreased after thousands of pollution enterprises were banned. Sections with serious pollution and higher risk were mainly located at Hengyang and Chang-Zhu-Tan regions (Changsha, Zhuzhou, and Xiangtan) for contaminations of Cd, As, Pb, and Hg. Values of both enrichment factor and geo-accumulation index followed the order Cd > Hg > Zn > Mn > Pb > Cu > As > Cr. Bioavailable fractions followed the order Cd (66.93%), Zn (33.80%), Pb (30.81%), Mn (18.38%), Hg (17.58%), Cu (10.20%), As (9.81%), and Cr (7.65%). Considering their bioavailability, biotoxicity, or abundance, contamination of Cd was the most dominant, and pollution of other metals should not be ignored.

Early Cambrian Black Shale-Hosted Mo-Ni and V Mineralization on the Rifted Margin of the Yangtze Platform, China: Reconnaissance Chromium Isotope Data and a Refined Metallogenic Model

The transgressive basal unit of the Early Cambrian black-shale sequence along the rifted margin of the southeastern Yangtze platform hosts a wide spectrum of marine sedimentary rocks distributed over more than a length of 1,000 km. A few-centimeter-thick sulfide-rich black shale units have spectacular metal tenors (Mo and Ni in the percent range, PGE + Au around 1 ppm) and consist of submillimeter-scale laminated sulfide and carbonaceous material and centimeter-sized pebble-like rip-up clasts of Mo-S-C compounds, pyrite, and Ni-rich polymetallic sulfides in carbonaceous and phosphate-rich matrix. The δ 53/52 Cr authigenic values of Mo-Ni sulfide-rich black shale samples from the Zunyi mining district (Guizhou province), as well as from the Sancha district (Hunan province), 400 km northeast, have a mean of 0.96 ± 0.22‰ ( n = 8), while V-rich black shale from both districts has a mean of 1.34 ± 0.46‰ ( n = 5). These data indicate significantly positively fractionated values compared to igneous silicate Earth. The Cr isotope values of the studied shales compare with recent findings of positively fractionated δ 53/52 Cr values in Late Neoproterozoic-Phanerozoic marine carbonates and shale/mudstones and attest for the operation of an intensified oxidative surface Cr cycle from at least around ~0.75 Gyr ago. We propose that the major change in Cr cycling around the Precambrian-Cambrian boundary was caused by a significant rise of atmospheric oxygen levels. The Cr isotope data confirm earlier conclusions from Mo and Os isotopes, which indicate a seawater metal source with ultimate metal supply by oxidative weathering of continental crust. In particular, covariation trends of Re-Os and of platinum-group elements display a distinct seawater signature, and a degree of metal enrichment which is an extension of the normal black shale pattern. The Mo-Ni sulfide-rich black shale units are probably produced by winnowing of subaquatic hardground deposited under euxinic conditions. The same stratigraphic level also hosts anoxic/suboxic V-rich black shale (V in illite) and huge phosphorite deposits in oxic/suboxic settings, bedded barite, as well as 10s of meter-thick sapropelic alginite (combustible shale). We show that the extreme metal enrichment of the Mo-Ni sulfide-rich black shale can be understood as a combination of redox cycling and bottom-water/sediment-interface scavenging under euxinic conditions (Mo, noble metals), and of oxidation (remineralization) of organic matter settling from the photic zone, with sulfide fixation of Ni and other biophile elements under denitrifying and sulfate-reducing conditions. High biological activity (as in coastal upwelling settings with high nutrient supply), very low clastic accumulation rate (as in protected basins), and low organic matter deposition (high rate of remineralization) in stratified oxic-suboxic-euxinic basins are requirements for advanced metal enrichment in black shales. A special bathymetric condition of slope deposition with intrabasinal olistostrome-like mass movement and gravitational winnowing explains both the peculiar ore textures and the further metal enrichment to ore grade in the Early Cambrian rock units on the Yangtze platform. The Mo-Ni sulfide-rich sediments can be regarded as the euxinic variant of the marine hydrogenous ore deposit spectrum, where ferromanganese nodules/crusts represent the oxic variant of extreme fractionation from seawater.

Comparison of metal accumulation in the azooxanthellate scleractinian coral (Tubastraea coccinea) from different polluted environments

The response of metal accumulation in coral Tubastraea coccinea to various degrees of metal enrichment was investigated from the Yin-Yang Sea (YYS) receiving abandoned mining effluents, the Kueishan Islet (KI) hydrothermal vent field, and the nearshore area of remoted Green Island (GI). The concentrations of most dissolved metals were highest in seawater at YYS, followed by KI, and then GI, showing the effects of anthropogenic and venting inputs on metal levels. Five metals (Co, Fe, Mn, Ni, and Zn) yielded significant differences (p<0.05) among the skeleton samples. We identified similar patterns in the metal–Ca ratios, indicating that the elevated metals in skeletons was a consequence of external inputs. The coral tissues were relatively sensitive in monitoring metal accumulation, showing significant differences among three locations for Cd, Co, Cu, Fe, Pb, Ni, and Zn. Specific bioconcentration factors provided strong support for the differential metal accumulation in skeletons and tissues.

Accumulation of heavy metals in leaf vegetables from agricultural soils and associated potential health risks in the Pearl River Delta, South China.

This study investigated the extent of heavy metal accumulation in leaf vegetables and associated potential health risks in agricultural areas of the Pearl River Delta (PRD), South China. Total concentrations of mercury (Hg), cadmium (Cd), lead (Pb), chromium (Cr) and arsenic (As) were determined in 92 pairs of soil and leaf vegetable (flowering Chinese cabbage, lettuce, pakchoi, Chinese cabbage, loose-leaf lettuce, and Chinese leaf mustard) samples collected from seven agricultural areas (cities). The bioconcentration factors (BCF) of heavy metals from soil to vegetables were estimated, and the potential health risks of heavy metal exposure to the PRD residents through consumption of local leaf vegetables were assessed. Results showed that among the six leaf vegetables, pakchoi had the lowest capacity for heavy metal enrichment, whereas among the five heavy metals, Cd had the highest capacity for transferring from soil into vegetables, with BCF values 30-fold those of Hg and 50-fold those of Cr, Pb and As. Sewage irrigation and fertilization were likely the main sources of heavy metals accumulated in leaf vegetables grown in agricultural areas of the PRD region. Different from previous findings, soil pH had no clear effect on metal accumulation in leaf vegetables. Despite a certain degree of metal enrichment from soil to leaf vegetables, the PRD residents were not exposed to significant health risks associated with consumption of local leaf vegetables. Nevertheless, more attention should be paid to children due to their sensitivity to metal pollutants.

Gamma-ray Bursts and the First Stars

Gamma-ray bursts (GRBs) triggered by the death of the first stars promise to provide a powerful probe into the state of the high-redshift universe. I will review the basic physics of how the first stars formed, evaluating whether they are suitable GRB progenitors. After providing estimates of the high-redshift GRB number density, I will discuss the utility of such bursts in probing the ionization state, and the degree of metal enrichment, of the early intergalactic medium. The prospects for these studies are bright, provided that we can fly a dedicated mission that combines a gamma-ray detector with on-board near-infrared capabilities.

Scavenging of atmospheric trace metal pollutants by mineral dusts: Inter-regional transport of Australian trace metal pollution to New Zealand

Dust samples collected from the surface of glaciers and in dust traps on the remote West Coast of New Zealand's South Island can reliably be identified as being of both Australian and New Zealand origin. Most are, however, found to be enriched in Cu, Zn, Cd, Sb, Sn, Pb, Ni and Cr, when compared with their source-area sediments. The degree of metal enrichment in the dust samples is proportionally related to the percentage of Australian dust implying that the pollutants were transported with dust from eastern Australia. Pollution enrichment factors for these metals in dusts were calculated with a high degree of certainty, because the specific source regions of the dust could be identified. Rates of trace metal pollution transport were then calculated using a record of Australian dust transport over New Zealand. Results show that significant concentrations of trace metal pollutants are transported to New Zealand at levels that are between 1.5 and 100 times background conditions. Results also show that Sb, Pb and Cr are highly particle reactive and their transport in this region is almost exclusively associated with dust scavenging (up-take of pollutants by dust). By comparison, Cu, Zn, Cd, Sn and Ni may also be transported independently of dust. While the rates of pollution metal transport reported here are lower than in more industrialised regions of the globe, the majority of these metals are being deposited in a region internationally recognised for its environmental and conservation values.

Comparison of metal accumulation in mussels at different local and global scales

Cadmium and zinc uptake from the dissolved phase, assimilation efficiency (AE) from the dietary phase, and body burden as well as clearance rate were measured in green mussels, Perna viridis, and blue mussels Mytilus edulis, M. galloprovincialis and Mytilus trossulus. Perna viridis was collected from four sites differentially enriched with trace metals in Hong Kong and blue mussels were collected from different climatic zones, i.e., subarctic and temperate, to allow comparisons with the more tropical green mussels. Despite similar shell length, the dry weight of mussels varied significantly between sites and species and this had a large effect on Cd and Zn accumulation, clearance rate, and metal body burden. All data were, therefore, weight adjusted to allow comparison without this confounding factor. Trace-metal body concentrations were significantly different between sites, and P. viridis collected from Tsing Yi, Hong Kong, had the highest levels of all measured metals when compared with other Hong Kong sites. There was, however, no relationship between the degree of metal enrichment and the Cd and Zn uptake (both from dissolved and particulate sources) and clearance rates. Furthermore, Cd and Zn uptake (dissolved and particulate) and clearance rate varied little between species or climatic zones of collection. Thus, over the range of body trace-metal concentrations measured and between mussel species over large geographical distances and climatic zones, the uptake rates, AEs, and clearance rates are similar when measured under the same laboratory conditions after body-size correction. When other factors such as salinity are also corrected, biomonitoring data from different areas and even utilizing different mussel species may be directly comparable. This study therefore provides important evidence in support of Mussel Watch Programs.

Heavy metal pollution in freshly deposited sediments of the Yamuna River (the Ganges River tributary): a case study from Delhi and Agra urban centres, India

The Yamuna River sediments, collected from Delhi and Agra urban centres, were analysed for concentration and distribution of nine heavy metals by means of atomic adsorption spectrometry. Total metal contents varied in the following ranges (in mg/kg): Cr (157–817), Mn (515–1015), Fe (28,700–45,300), Co(11.7–28.4), Ni (40–538), Cu (40–1204), Zn (107–1974), Pb (22–856) and Cd (0.50–114.8). The degree of metal enrichment was compared with the average shale concentration and shows exceptionally high values for Cr, Ni, Cu, Zn, Pb and Cd in both urban centres. In the total heavy metal concentration, anthropogenic input contains 70% Cr, 74% Cu, 59% Zn, 46% Pb, 90% Cd in Delhi and 61% Cr, 23% Ni, 71% Cu, 72% Zn, 63% Pb, 94% Cd in Agra. A significant correlation was observed between increasing Cr, Ni, Zn, and Cu concentrations with increasing total sediment carbon and total sediment sulfur content. Based on the Muller's geoaccumulation index, the quality of the river sediments can be regarded as being moderately polluted to very highly polluted with Cr, Ni, Cu, Zn, Pb and Cd in the Delhi and Agra urban centres. The present sediment analysis, therefore, plays an important role in environmental measures for the Yamuna River and the planning of these city centres.

Importance of geomorphology and sedimentation processes for metal dispersion in sediments and soils of the Ganga Plain: identification of geochemical domains

The Ganga Plain, one of the largest alluvial plains of the earth is under severe environmental stress due to rapid industrial and urban development and exploding population growth. Disposal of industrial and urban wastes and the ignorance of their management have resulted severe environmental problems, especially metal pollution. In the present study, an attempt is made to understand the transport and dispersion processes of metal contaminants in sediments and soils in Kanpur–Unnao industrial region of the Ganga Plain. The significance of geomorphology and monsoon rain is assessed in determining the distribution of contaminated sediments in this area. Three regional geomorphic surfaces (T 0, T 1 and T 2) are identified, each with its characteristic river channel patterns and sediment distribution system which influence the dispersion and accumulation of the metal contaminants. The sediment and water distribution regime depends on the nature of geomorphic features and character of the river channels. Geomorphic features, sedimentation processes, the nature of the river channels and distribution of excess rain water of the monsoon season have given the bases to delineate five geochemical domains in the study area. Each geochemical domain is an independently operating system with its own geomorphic and geochemical characters. Chemical parameters (e.g., pH), metal concentrations, and dispersion of metal-contaminated sediments and soils vary from domain to domain. In comparison to reference values, each domain exhibits its own enrichment of elements, namely the Loni River domain has high contents of C-org, Cd, Cr, Zn; the Ganda Nala domain of C-org, Cu, Cr; the Ganga River domain of C-org, Cr, Cu, Pb, Sn, Zn; the Sewage Network domain of C-org, Cd, Cr, Cu, Pb, Ni, Sn, Zn; and the Pandu River domain of C-org, Cd, Cu, Ni, Zn. Patterns of changes in metal concentrations from one monsoon year to the other and in different seasons of a monsoon flood cycle are also domain specific. Each geochemical domain exhibits its own degree of metal enrichment in sediments and soils by anthropogenic activities and physico-chemical processes. Identification of geochemical domains with their specific physico-chemical processes in the fluvial system of the Ganga Plain will certainly help in assessing the environmental problems and land contamination of this region.

HIRES Spectroscopy of APM 08279+5255: Metal Abundances in the Lyα Forest

We present high-S/N echelle spectra of the recently discovered ultraluminous QSO APM 08279+5255 and use these data to reexamine the abundance of carbon in Ly? forest clouds. In agreement with previous work, we find that approximately 50% of Ly? clouds with hydrogen column densities of log N (H I) ? 14.5 have associated weak C IV absorption, with log N(C IV) 12.0, and we derive a median N(C IV)/N(H I) = 1.4 ? 10-3. The agreement with earlier estimates of this ratio may be somewhat fortuitous, however, because we show that previous analyses have probably overestimated the number of Ly? clouds that should be included in this statistic. We then investigate whether there is any C IV absorption associated with lower H I column densities by stacking 51 C IV regions corresponding to 51 Ly? lines with 13.5 ? log N(H I) ? 14.0. The coadded spectrum has a S/N 580 but shows no composite C IV absorption. In order to understand the significance of this nondetection, we have stacked together 51 theoretical C IV ?1548 lines with individual values of column density and velocity dispersion scaled appropriately from the values measured in the corresponding Ly? lines. We find that even if the typical value of N(C IV)/N(H I) = 1.4 ? 10-3 applies to these lower column density clouds, the corresponding signal in the stacked C IV region is smeared by the likely random difference in redshift between C IV and Ly? absorption and becomes very difficult to recognize. This seems to be a fundamental limitation of the stacking method, which may well explain why in the past it has led to underestimates of the metallicity of the Ly? forest. We also analyze our spectra with the pixel-by-pixel optical depth technique recently developed by Cowie & Songaila and find evidence for net C IV absorption in Ly? clouds with optical depths as low as ?(Ly?) = 0.5-2, as these authors did. However, we show with simulations that even this method requires higher sensitivities than reached up to now to be confident that the ratio N(C IV)/N(H I) remains constant down to column densities below log N(H I) 14.0. We conclude that the question of whether there is a uniform degree of metal enrichment in the Ly? forest at all column densities has yet to be fully answered. Future progress in this area will probably require concerted efforts to push further the detection limit for C IV lines in selected bright QSOs.

Dynamics of Galaxy Merging and the Origin of the Color‐Magnitude Relation of Elliptical Galaxies

We numerically investigate both chemical and dynamical evolution of gas-rich galaxy mergers in a self-consistent manner in order to explore the origin of the color-magnitude (C-M) relation of elliptical galaxies. We especially investigate the dependence of the mean stellar metallicity of merger remnants on the rapidity of gas consumption by star formation during merging. We found that galaxy mergers with more (less) rapid gas consumption by star formation show a larger (smaller) degree of metal enrichment. The reason for this dependence can be explained as follows. For a galaxy merger with more rapid star formation, a lesser amount of interstellar gas is tidally stripped away from the system during galaxy merging principally because a greater amount of initial gas has been already converted to a stellar component before the system suffers more severely from the violently varying gravitational potential of galaxy merging. As a result of this, a greater amount of the gas is consequently enriched to a larger extent with metals and is converted to a stellar component during merging. Thus, greater amounts of metals are shared by the stellar component in the remnant of the galaxy merger with more rapid star formation. This result implies that if more luminous elliptical galaxies are formed by galaxy merging with more rapid star formation, the C-M relation can be reproduced at least in a qualitative way. This result furthermore demonstrates that the origin of the C-M relation of elliptical galaxies can be closely associated with the details of the dynamical process of galaxy merging, which depends principally on the rapidity of gas consumption by star formation in merging galaxies.

Monitoring trace metal contamination in salt marshes of the Westerschelde estuary

A survey is given of the possibilities and restrictions of (bio)monitoring trace metals in the salt marsh as exemplified for the Scheldt estuary. The objectives for monitoring in the salt marsh are enumerated as well as the requirements they should meet. Previous studies on monitoring trace metals in the salt marsh are reviewed.Problems in monitoring trace metals in the soil subsystem are due to variations in the input of these metals, the type of esturine circulation and the distribution of physical and chemical conditions in the salt-marsh deposits. The degree of metal enrichment and the spectrum of chemical speciation of the metals by means of a sequential extraction procedure is shortly discussed.Problems in monitoring trace metals in salt-marsh plants are discussed with respect to the bioavailability of these metals from soil and inundation water as sources of contamination, the allocation and seasonal variation in metal accumulations, and the role of adhesive particulate matter carried on the shoots by the floods. Aster tripolium seems to be a good species for biomonitoring trace metals in the vegetational component of the salt-marsh ecosystem.