Multi-element analysis of trace element levels in human autopsy tissues by using inductively coupled atomic emission spectrometry technique (ICP-AES).

Autopsy tissue samples from the brain front lobe, cerebellum, heart, kidney (cortex and medulla), liver, pancreas, spleen and ovary were analysed for AL, B, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, Sr and Zn in 30 (17 women and 13 men) subjects ranging in age from 17 to 96 years at Haukeland University Hospital in Norway. The tissues were selected from macroscopically normal organs and samples were handled according to guidelines recommended to avoid contamination in the pre-analytical phase. Concentration of the trace elements were determined by the inductively coupled plasma atomic emission spectrometry technique (ICP-AES). In most tissues the concentrations of the essential trace elements followed the order Fe> Zn> Cu> Mn> Se> Cr> Co except in the ovary where Se was higher than Mn. The liver was the major site of deposition for Co, Cu and Mn as well as the spleen for Co, brain front lobe for Cu and pancreas for Mn. Ba, Sr and Ni built up in the ovary foLLowed by the kidney. Older subjects accumulated Ba and Sr in most tissues, whereas Al accumulated in the kidney cortex and Cd in the brain cerebellum. Generally males had higher concentrations of trace elements in the different tissue sampLes than females with the exception of Mn in the brain front lobe and heart and Sr in the liver. ICP-AES is a useful method to assess the concentration and the profiLe of trace elements in human autopsy tissues.     

Minor and trace elemental contents of cancerous breast tissue measured by instrumental and radiochemical neutron activation analysis

Many minor and trace elements influence the permeability of cell membranes by competing for binding sites, and exert direct or indirect action on the carcinogenic process. Instrumental and radiochemical neutron activation analysis has been employed for the determination of more than 20 elements in normal and cancerous breast tissues of 6 patients. Most trace elements, viz., Zn, Cu, Mn, Co, Se, Br, As, Sb and Cd, are elevated in cancerous tissue, whereas lower levels are observed for Fe, Cs, I, and Sr. Similarly, concentrations of minor constituents, such as Na, K, P, Cl, and Mg, are enhanced compared to normal tissue. Several elements incorporate into the normal cell, change its enzymatic activity, and accelerate the growth of tumor.

     

Trace Elements and Metallothionein in Liver and Kidney of <Emphasis Type="Italic">Felis catus</Emphasis>

Trace metals such as Zn, Cu, and Fe are essential for life; differently, no biochemical function is known for Cd. Changes in dietary metal concentrations can cause deficiency or toxicity. Studies on trace elements in cat are lacking. This paper aimed to analyze Zn, Cu, Fe and Cd concentrations in liver and kidney of pathological domestic cat and to isolate metallothionein (MT) in these tissues. It was not possible to explore a possible correlation between metal concentrations and pathologies because the incidence for each of them was too low. Fe was the most abundant metal; in particular, the liver accumulates average Fe concentrations one order of magnitude higher than Zn and Cu, ranging from 66.75 and 1,444.23 μg/g. Significantly, higher levels of Fe were found in the liver of elder animals. Zn concentrations varied between 26.31 and 84.78 μg/g in the liver whereas in the kidney, ranged between 7.69 and 71.15 μg/g. Cu concentrations were between 2.37 and 112.91 μg/g in liver and between 2.12 and 9.85 μg/g in kidney. Cd was the least abundant metal with the exception of the kidney of the oldest cats where it reached a maximum of 13.71 μg/g. Gel-filtration metal distribution profiles from cytosolic extracts revealed the presence of Cd, Cu, Zn thioneins either in the liver or in the kidney. Because tissue samples were taken from pathological cats from different breed and age, care must be taken to use these data as a baseline profile of trace elements in healthy animals. Our results are indicative that for some specimens the feed levels of Fe and Cu could be higher than the optimal dietary intake and in few cats, there was also an exposure to Cd that was counteracted by MT biosynthesis.     

Comparative Evaluation of Trace Metal Distribution and Correlation in Human Malignant and Benign Breast Tissues

Selected trace metals were analyzed in human malignant and nonmalignant (benign) breast tissue samples by the flame atomic absorption spectrophotometric method. In malignant tissues, dominant mean concentrations were revealed by Na, K, Ca, Mg, Fe, Zn, and Al at 927, 552, 231, 61.7, 36.5, 18.3, and 8.94 microg/g, respectively, while the mean metal levels in benign tissues were 903, 435, 183, 63.3, 24.7, 14.5, and 10.1 microg/g, respectively. Average concentrations of Cd, Co, Cr, Cu, Fe, Mn, K, Ca, and Zn were noted to be significantly higher in the malignant tissues compared with the benign tissues. Significantly strong correlations (r > 0.50) in malignant tissues were observed between Mn and Co, Mn and Cd, Cd and Cr, Fe and Mn, Cd and Co, Fe and Co, Mg and Pb, Cd and Fe, Mg and Ni, Pb and Ni, Ni and Sr, and Fe and Pb, whereas, Cd and Co, Cd and Mn, Co and Mg, Co and Mn, Cu and Mn, Co and Ni, Mg and Ni, Cd and Cu, Cd and Ni, Ca and Mg, Mn and Pb, Cu and Ni, Fe and Ni, Cd and Mg, Co and Cu, Cr and Na, and Cd and Cr revealed strong and significant relationships in benign tissues at p < 0.001. Principal component analysis of the metals data yielded six principal components for malignant tissues and five principal components for benign tissues, with considerably different loadings, duly supported by cluster analysis. The study revealed a considerably different pattern of distribution and mutual correlations of trace metals in the breast tissues of benign and cancerous patients.     

Accumulation of cadmium, zinc, and copper by Helianthus annuus L.: impact on plant growth and uptake of nutritional elements

We investigated the effects on physiological response, trace elements and nutrients accumulation of sunflower plants grown in soil contaminated with: 5 mg kg(-1) of Cd; 5 and 300 mg kg(-1) of Cd and Zn, respectively; 5, 300, and 400 mg kg(-1) of Cd, Zn, and Cu, respectively. Contaminants applied did not produce large effects on growth, except in Cd-Zn-Cu treatment in which leaf area and total dry matter were reduced, by 15%. The contamination with Cd alone did not affect neither growth nor physiological parameters, despite considerable amounts of Cd accumulated in roots and older leaves, with a high bioconcentration factor from soil to plant. By adding Zn and then Cu to Cd in soil, significant were the toxic effects on chlorophyll content and water relations due to greater accumulation of trace elements in tissues, with imbalances in nutrients uptake. Highly significant was the interaction between shoot elements concentration (Cd, Zn, Cu, Fe, Mg, K, Ca) and treatments. Heavy metals concentrations in roots always exceeded those in stem and leaves, with a lower translocation from roots to shoots, suggesting a strategy of sunflower to compartmentalise the potentially toxic elements in physiologically less active parts in order to preserve younger tissues.     

Biosorptive-flotation of copper(II) from environmental water samples using sugar beet pulp as sorbent and oleic acid as surfactant

Abstract

Wounds are likely to have existed ever since mankind has existed. Wound healing is an enormously complicated process and the actual scientific mechanisms and events that take place during healing are far more complex and dynamic than might be imagined. Essential elements, especially trace elements are believed to be pivotal to the wound healing process. Their involvement in tissue regeneration and repair appears to be wide ranging and their deficiencies have been reported to impair the healing process. However, further research is required to establish the involvement of trace elements and their specific species in the wound healing process.

Thus assessments of trace element levels in wound tissues using new, reliable, verified and validated technologies could be beneficial for trace element based wound healing. Here, is an attempt made to assess the link between trace element concentrations and healing processes of chronic and acute wounds. Wound tissue samples from 58 chronic leg ulcers and 50 acute wounds were analysed for concentrations of Fe, Zn, Cu, Mn, Ca, Sn, Cr, Cd and Pb using atomic absorption spectrophotometer. Blood samples were also collected from the same patients and analysed in the same manner. All the data were tested for normality by Ryan–Joiner normality test (α = 0.05) and one-way ANOVA was done for the normally distributed data.

The results showed that the concentration of Ca, Zn, Cu and Mn were similar in both acute and chronic wounds. Apart from Ca, which showed elevated concentrations, other metal concentrations are either similar or lower than the analysed concentrations in blood. It appears that there is a significant difference in the concentrations of iron accumulated in the tissues of chronic and acute wounds.

The concentrations of Sn, Cr, Cd and Pb, which are considered as toxic metals, were not present in detectable levels with the graphite furnace atomic absorption spectrophotometry in both types of wound tissues.     

Chemometric Methods for Studying the Relationships Between Trace Elements in Laryngeal Cancer and Healthy Tissues

A quick and reliable method for the evaluation and classification of two types of tissues is presented. Several chemometric methods were applied to evaluate multivariate data of the tissue samples with respect to the content of trace elements. The content of Pb, Al, Zn, Cd, Cu, Ni and Co was determined in samples of healthy and cancerous tissue obtained from 26 patients. Determination was done at milligram/kilogram level with inductively coupled plasma optical emission spectrometry (ICP-OES) and atomic absorption spectroscopy (AAS) techniques. Contents of trace metals in studied tissues are not normally distributed; however, normal distribution was confirmed for log values. There is a statistically significant difference in the content of Zn, Cd, Cu and Al (p?<?0.01) and Ni and Co (p?<?0.05) when healthy tissue is compared to cancerous one. Correlation between contents of trace elements for studied tissues was positive; the highest was found between Zn and Cu. A chemometric methodology seems to be a promising tool for classifications of the tissue samples.     

An elemental correlation study in cancerous breast tissue by total reflection x-ray fluorescence

The total reflection x-ray fluorescence method (TRXRF) has been employed to determine of P, S, K, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Se, Rb, Sr, and Pb concentration in the benign breast tumor tissue from 68 women and in the cancerous breast tissue from 26 women. Concentrations of most of elements show enhancement in cancerous breast tissue. Examined elements compete for binding sites in the cell, change its enzymatic activity, and exert direct or indirect action on the carcinogenic process accelerating the growth of rumors. Inhibition of enzymatic activity caused by variation in trace element concentrations results in immunological breakdown of the body system. An attempt has been made to correlate measured trace element concentrations with the clinical stage of cancer. Physical bases of used analytical method, experimental setup, and the procedure of sample preparation are described.     

An elemental correlation study in cancerous and normal breast tissue with successive clinical stages by neutron activation analysis

Influence of trace elements in body metabolism and their physiological importance in various diseases have motivated their accurate and quantitative determination in biological tissues and fluids. Instrumental Neutron Activation Analysis (INAA) using short and long term irradiation has been employed to determine five minor elements (Cl, K, Na, Mg, P) and 15 trace elements (As, Br, Co, Cr, Cs, Cu, Fe, Hg, Mn, Rb, Sb, Se, Sc, Sr, and Zn) in cancerous and normal breast tissue from 30 patients of four clinical stages. Several elements show enhancement in cancerous breast tissue. Selenium shows maximum enhancement of 94.7% followed by K (81.6%), Sc (66.7%), Cu (58.2%), Na (48.5%), P (44.4%), and Zn (39.2%). Some element, such as Fe, Cr, and Mn, are depressed by 30.8, 30.1, and 12.8%, respectively. These elements compete for binding sites in the cell, change its enzymatic activity and exert direct or indirect action on the carcinogenic process accelerating the growth of tumors. This is further evidenced by histopathological examination of cancerous cells showing poor cytological differentiation. An attempt has been made to correlate trace element concentrations of Se, Cu, Zn, Rb, Br, Hg, As, Co, Fe, Cr, and Mn and the ratios of Se/Zn, K/P, Cu/Zn, Na/K, and Se/Fe with the clinical stages of cancer. Inhibition of enzymatic activity caused by variation in trace element concentrations results in immunological breakdown of the body system.     

厦门中华白海豚体内微量元素的初步分析

对5头中华白海豚(Sousa chinensis)9种器官组织中的Cu、Zn、Cd、Pb、Hg、Ni、Se、As、Mg、Mn、Al等微量元素的含量进行了测定。结果表明,在少年个体中,Cu(P<0·05)和Mn(P<0·01)在肝中的含量及Zn在肝(P<0·01)、肠(P<0·05)、胃(P<0·05)和心(P<0·05)中的含量明显高于肌肉中相应微量元素的含量,其余微量元素在各种组织中变化不大;在成年个体中,Pb在肺中的含量明显高于肝(P<0·001)、肌肉(P<0·01)、胃(P<0·01)和心(P<0·05)中的含量,Hg在肝中的含量明显高于胰(P<0·05)。整体上来说,大多数微量元素在成体中的含量高于少年个体,表明微量元素是随年龄的增长而逐渐累积的。有毒重金属如Hg、Cd和Pb在肾、肝以及卵巢中累积较多,提示这些器官承受了较大的毒性压力。     

Elements in Lung Tissues of Patients from a High Lung Cancer Incidence Area of China

The concentrations of trace elements are closely related to tumor genesis, progression, and therapy. In order to establish the extent to which trace elements apply to lung cancer, 15 trace elements were determined in 60 lung tissue samples from residents of Xuanwei and Fuyuan, two counties with extremely high lung cancer incidences in Yunnan province, China. The results indicated that the levels of V, Fe, Zn, Cd, Ni, Cu, Se, and Pb in the lung cancer tissues were significantly different from those in benign tissues. Among the eight elements, the levels of V, Fe, Zn, and Cd in the lung cancer tissues were lower than those in the benign tissues, while those of Ni, Cu, Se, and Pb were higher. Multiple conditional logistic regression showed that among the 15 elements, Cu, Pb (β > 0, OR > 1), and Zn (β < 0, OR < 1) were closely related to the lung cancer. Cu and Pb were classified as risk factors for local lung cancer and Zn was identified as a protective factor. The results obtained will provide dietary suggestions in terms of how to reduce lung cancer risks by appropriately balancing the intakes of certain trace elements especially for individuals who are from those two counties.     

牛组织重金属含量与饲养环境的相关性

通过选择不同污染程度的区域进行取样,分析了贵州地区不同污染水平下牛组织中重金属(Cu、Zn、Pb、Cd)的含量和与饲养环境的相关性.结果表明:贵州不同污染水平下牛组织中的Cu、Zn基本符合国家食品卫生要求,Pb只有污染地区的肝脏和肾脏超过限量标准,Cd污染较严重,除非污染区肝脏外,牛肾脏和肝脏中Cd的平均含量均超过国家肉类制品卫生限量标准,但肌肉组织符合卫生标准;牛组织重金属元素含量与饲养环境中的土壤、饲料和饮用水源的重金属含量和污染程度密切相关,尤其是肾脏组织,其相关系数r＞0.78.饲料向牛组织的重金属迁移系数,随饲料元素含量的增加而逐渐降低,其中Cd的迁移系数最大,Pb的迁移系数最低;必需元素和有害元素在不同组织中的比值,随污染程度的增加而降低.肾脏的Cu/Cd和Zn/Cd值比其它组织低得多,Cd主要在肾脏中蓄积,Cu主要在肝脏组织蓄积,Zn主要在肌肉和肝脏,Pb主要在肾脏和肝脏.     

Trace elemental analysis of cancer-afflicted intestine by PIXE technique

Trace elemental analysis was carried out in the biological samples of cancer-afflicted intestine using the particle-induced X-ray emission technique (PIXE). A 2-MeV proton beam was employed to excite the samples. From the present results, it can be seen that the concentration of the elements Cr, Fe, and Ni are higher in the cancerous tissue of the intestine than those observed in the normal tissue, whereas the concentration levels of the element Zn is slightly lower in the cancer tissue of intestine than that observed in the normal tissue. The concentrations of S, Cl, K, Ca, Ti, Mn, Co, and Cu in the cancer tissue of the intestine are in agreement with those observed in the normal tissues within standard deviations. The present results support the previous observations that Ni and Cr are carcinogenic agents. The observed slightly low levels of zinc in the cancer tissue of the intestine suggest that zinc could possibly inhibit the tumor growth and development of neoplastic transformation. For correctly assessing the role played by the trace elements in initiating, promoting, or inhibiting cancer in various organs, there is a need for the acquisition of more data by trace elemental analysis from several investigations of this type undertaken in different regions.     

Accumulation of trace metals in eggs and hatchlings of Chelonia mydas

BackgroundThe objective of this study was to verify the accumulation of trace metals in eggs and hatchlings of Chelonia mydas, evaluating if metal accumulation is originated from maternal transfer and/or from the incubation environment. Other assessments were also performed, as metal distribution in different tissues (blood, kidney, liver, muscle, and turtle shells) of newly hatched turtles, and genotoxic analysis, to verify possible damages caused by the presence of metals.MethodsThe assessments were carried out by quantifying Cd, Ni, Pb, Mn and Fe in egg sample collected during laying time (eggshells (ELT) and egg content (EC)), eggshells from newly hatched turtles (ENH), hatchlings tissues (H - blood, kidney, liver, muscle, and shell)) (n = 18 for each biological sample - 3 of each nest) and nest sediments (n = 6, one of each nest). Comparative analysis were made between ELT and ENH, as well as between egg content (EC) and the sum of tissue samples from hatchlings, using Mann-Whitney hypothesis test (p < 0,05). The amount of metals in different hatchling was quantified and followed by the Dunn post-test. A principal component analysis (PCA) was also employed.ResultsMetals studied were found in all investigated samples. The concentration of a great amount of investigated metals was significantly higher (P=<0.001) in eggshells from ENH than in ELT. An increase in Cd (2.16-fold), Pb (3.47-fold), Fe (6.83-fold) and Mn (195.57-fold) concentration was noticed in ENH. We also observed an increase in Fe (1.59-fold), Mn (1.74-fold) and Ni (1.59-fold) concentration in hatchling, when compared with EC, due to transfer from nest sediments. In relation to the hatchling’s tissues, blood was shown to accumulate higher concentrations of Ni and Pb, while shells accumulated more Cd and Fe, and Mn is more associated with liver and kidney. Fe was the highest accumulated metal in both tissues, and muscles presented discrete concentrations of Ni, Mn, and Pb. A mean concentration of 1.25‰ MN was obtained in C. mydas hatchlings, indicating that the accumulation of metals in hatchlings didn’t cause toxicology effects.ConclusionHatchlings accumulate metals through the maternal and sediment transfer, although the levels of metal accumulation were not enough to cause genotoxic damage.     

Analysis of tissue cadmium distribution in chronic cadmium-exposed mice using in-air micro-PIXE

This study undertook the analysis of tissue cadmium (Cd) distribution using in-air micro-particle-induced X-ray emission (PIXE) and the examination of the involvement of metal ions in parenteral Cd toxicity. A mouse was injected intraperitoneally with 3 mg/kg body weight of CdCl₂ thrice weekly. After 27 wk, the liver and kidney were excised and fixed in 10% formalin solution for 4 h and then embedded in paraffin. Thin paraffin sections were used to analyze trace elements with in-air micro-PIXE and to examine metallothionein protein and histological changes. Cd distribution was determined by micro-PIXE in the liver and renal cortex of the Cd-exposed mouse, and the net Cd count was higher in the liver than in the renal cortex. The net iron (Fe) count was higher in the liver of the Cd-exposed mouse compared to the control, and an opposite tendency was observed in the renal cortex. Wide cellular Cd distribution was demonstrated in the liver and renal cortex of the chronic Cd-exposed mouse compared to the control. Metallothionein staining was increased by chronic exposure to Cd both in the liver and kidney, and nephrotoxicity was more apparent than hepatotoxicity. The modification of tissue Fe and calcium distribution by an intraperitoneal injection of Cd might be involved in Cd-induced toxicity.     

Tissue accumulation of cadmium as a function of blood concentration

We have provided data relating Cd concentration in tissue to about a 40-fold range in blood Cd concentration. Osmotic pumps containing cadmium chloride were subcutaneously implanted in male New Zealand white rabbits. The pumps continuously delivered either 0.15 or 1.5 mg Cd/d. Blood and plasma levels of Cd were measured weekly throughout the study. After 28 d, the rabbits were killed and tissue concentrations of Cd determined by atomic absorption spectrophotometry. Less than 10% of the total Cd in the blood was carried in the plasma, the remainder was associated with the blood cells, where it was bound mainly to metallothionein. We found the blood and tissue levels of Cd were correlated for each tissue we investigated. There was a wide range in affinity of the tissues for Cd; liver and kidney had the highest Cd uptake, whereas brain affinity was about 500 times less than liver.     

Effect of dietary Ca and Cd level of pregnant rats on reproduction and on dam and progeny tissue mineral concentrations.

Pregnant Sprague-Dawley rats were used to determine the effects of the addition of 200 ppm of Cd (as CdCl2) to the diet factorially with two levels of dietary Ca (0.07% and 0.96%) on reproductive performance, concentrations of Cd, Cu, Fe, Zn, Ca and Mg in dam liver and kidney and in newborn progeny. High Cd significantly increased liver and kidney Cd, Zn and Ca and decreased liver Fe. High dietary Ca partially protected against accumulation of Cd in liver and kidney but had no effect on concentration of other elements. Number of live or stillborn pups per litter was not significantly affected by diet but high Cd significantly reduced pup birth weight. No grossly abnormal pups were noted. Concentration of Cd in bodies of newborn pups was increased approximately 8.6-fold by high Cd in the diet of dams fed the 0.07% Ca-diet and 3.8-fold by high-Cd in the diet of dams fed the 0.96% Ca diet. Pup, Zn, Cu and Fe contents were significantly decreased and Ca was significantly increased by high-Cd in the maternal diet whereas pup Mg content was unchanged. Maternal Ca intake had no effect on concentration of Zn, Cu, Fe or Ca in newborn pups. The biological importance of the alteration in maternal and fetal tissue concentration of Zn, Cu and Fe by high-Cd maternal diets is unknown.     

Evaluating tissue levels of the eight trace elements and heavy metals among esophagus and gastric cancer patients: A comparison between cancerous and non-cancerous tissues

BackgroundConsidering the affecting role of environmental factors including trace elements and heavy metals on the upper gastrointestinal (GI) cancers, there is paucity of empirical research in tissue evaluations.ObjectivesThe present study aimed to measure the tissue content of some trace elements and heavy metals such as zinc (Zn), chromium (Cr), manganese (Mn), tin (Sn), copper (Cu), aluminum (Al), lead (Pb), and iron (Fe) in esophagus and gastric cancerous tissues compared to the adjacent healthy tissues.MethodsIn a cross-sectional study, the aforementioned trace elements and heavy metals were evaluated among patients with esophagus and gastric cancers. During endoscopy, multiple samples were taken from cancerous lesions and the adjacent healthy tissues. The classic flame atomic absorption spectroscopy (FAAS) method was employed as the study framework.ResultsFifty patients with the mean age of 53.92 ± 8.73 were enrolled in the current study. Thirteen patients suffered from esophageal cancer and thirty-seven patients were afflicted with gastric cancer. The results revealed significant differences in the median concentrations of Zn, Cr, Sn and, Cu (P < 0.05) between the two groups. Although there were no significant changes in the tissue content in the esophageal samples, in the median concentrations of Zn, Cr and, Sn (P < 0.05) in gastric tissues, significant differences were observed. Further, the results indicated that gender enacted an affecting role in the level of some trace elements and heavy metals.ConclusionThe tissue contents of some elements were altered in gastric and esophageal cancers; this difference may reflect the underlying mechanism of cellular changing during the tumorigenesis or direct exposure of these elements. It seems that under the shade of other coexisting risk factors, larger cohort studies are suggested to be conducted to investigate other probable aspects in this area of interest.     

Tissue distribution of some elements in rats

The concentrations of 14 elements were determined in rat whole blood, plasma, brain, heart, skeletal muscle, liver, kidney, spleen, thymus, and bone, using multielement ICP optical emission spectrometry. The tissue to plasma concentration ratios were calculated in order to determine tissue distribution and its homogeneity. The results show the likely sequences of element concentrations in tissues: RB>P≥K>(Fe)>Zn≥Mg>Cu>S>(Sr≥Ca>Na); and of the homogeneity of the distribution: (Fe)相似文献   

TRACE METAL CYCLING IN THE U.S. COASTAL ZONE: A SYNTHESIS

This synthesis of trace element research in estuarine communities of the U.S. coastline and the Caribbean provides a summary applicable to the shoreline of the tropical and temperate regions of the world which have mangroves, kelp beds, riverine marshes and seagrass communities. An inventory of sediments and leaf tissues shows Mn and Fe to be the most highly concentrated elements with Hg and Cd present in lowest concentrations. Generally, trace element concentrations in roots are much higher than in leaves and other tissues above the sediment. Tissue to sediment concentration ratios show that Cd is most likely to be bioamplified and that Cu, Hg, Sr and Zn may have relatively high concentration ratios which can exceed unity. A conceptual model was constructed to integrate the forcing functions, compartmental couplings, and dynamics common to these estuarine systems. Seasonality is important for changes in some trace element concentrations in plants and litter. Trace element additions to water or sediment increased certain trace element concentrations in plants and dead organic matter. It is clear that estuarine plant communities serve as living filters of estuarine trace elements. However, increased knowledge of trace element cycling in estuarine systems and relationships between trace element concentrations in plants and the estuarine food chain is needed, particularly food chains to man. There is a need for structured long-term estuarine research to allow direct comparison of results among estuarine study sites, to identify the similarity of population and system processes among estuaries and to define the geographical scale over which estuarine research results may be generalized.