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PubMed2004

Heavy metals in petroleum-contaminated surface soils in Serbia.

Investigation of heavy metal contamination levels as well as their association types with substrates in petroleum-contaminated surface soil was carried out using modified sequential extraction method. In that way, remobilization capacity of metal cations, both in natural conditions and in accidents, has been studied. Moreover, partitioning of heavy metals, originating from spilt oil derivative, among surface soil substrates was estimated. Extreme contamination with lead was discovered, as well as the increased concentrations of zinc and copper. Oil-derived Pb and Zn were found to be distributed between carbonates and amorphous Fe-oxides, whereas Cu was found to be dominantly associated with amorphous Fe-oxides. Appreciable amounts of these metals were also found to be incorporated into more resistant structures. In petroleum-contaminated surface soil, substrates of cadmium are carbonates, whereas nickel has the great affinity toward hydrous Mn-oxides. Cd is proven to be the most mobile metal in oil-contaminated surface soil.

Cadmium↗

PubMedDate not supplied

Risk factors for complications in clean-contaminated head and neck surgical procedures.

BACKGROUND: Contamination of a head and neck surgical wound with oropharyngeal secretions has been shown to dramatically increase the incidence of wound complications. Appropriate perioperative antibiotic prophylaxis has significantly reduced contaminated wound infection rates in several previous reports. The current study examined multiple patient parameters to determine risk factors for all perioperative complications following clean-contaminated head and neck surgical procedures. METHODS: Retrospective review of medical records from 159 patients who underwent clean-contaminated major head and neck surgical procedures at the University of Washington between 1985 and 1991. More than 30 preoperative and operative parameters were evaluated, and all complications were recorded. The data were examined using a multivariate statistical analysis. RESULTS: An overall complication rate of 63% included 22% with wound infections (oro/pharyngocutaneous fistula or purulent drainage), 22% with other types of infections, and 51% with noninfectious complications. The overall perioperative mortality rate was 1.2% (two patients). Prior radiotherapy, operative time, perioperative transfusion, and flap reconstruction were all associated with a significantly higher overall complication rate (p < or = 0.05). Only prior radiotherapy therapy correlated with an increase in wound infection rate (p = 0.05). CONCLUSIONS: Prior radiotherapy significantly increases the risk of perioperative complications and wound infections following clean-contaminated head and neck surgical procedures. Other factors reflecting the complexity of the procedure also influence the overall complication rate.

Adult↗

PubMed2005

Maternal cell contamination of prenatal samples assessed by QF-PCR genotyping.

OBJECTIVES: To establish the genotype of cultured cells from a cohort of amniotic fluid and chorionic villus samples, and compare this genotype with that obtained from uncultured material from the same sample, in order to assess the frequency and significance of maternal cell contamination of prenatal samples. METHODS: Quantitative fluorescence-polymerase chain reaction (QF-PCR) was carried out by amplification of microsatellite markers using fluorescence-labelled primers, followed by quantitative analysis of the allele peaks on a genetic analyser. A multiplex of 12 primer pairs for four loci on each of chromosomes 13, 18 and 21 was used. RESULTS: A total of 307 prenatal samples were tested. Of the 254 amniotic fluid samples, 39.8% had some degree of bloodstaining, ranging from 5% bloodstaining in the cell pellet to heavily bloodstained fluid. Uncultured samples were tested by QF-PCR analysis and the cultured cells were tested by both QF-PCR and karyotype analysis. Of the samples, 90.2% had the same single genotype on direct and cultured material. Two samples (0.65%) were mosaic for an aneuploidy cell line. A second genotype, interpreted as maternal cell contamination, was identified in direct and/or cultured preparations in 9.1% of samples, 17.8% of which were not bloodstained. Seven amniotic fluid samples (2.8%) showed maternal cell contamination in cultured material. CONCLUSIONS: For heavily bloodstained amniotic fluid samples, a maternal blood specimen may help interpret the results of rapid trisomy testing, followed by confirmation of the fetal origin of cultured cells. QF-PCR analysis has established a higher incidence of maternal cell contamination of cultured amniocytes than previous reports; the presence of MCC (maternal cell contamination) in cultured cells from samples with no bloodstaining underlines the need for karyotype analysis of more than one XX culture.

Adult↗

PubMed2005

The impact of blood contamination on the proteome of cerebrospinal fluid.

Human cerebrospinal fluid (CSF) is in direct contact with the brain extracellular space. Beside the secretion of CSF by the choroid plexus the fluid also derives directly from the brain by the ependymal lining of the ventricular system and the glial membrane and from blood vessels in the arachnoid. Therefore, biochemical change in the brain may be reflected in the CSF. CSF is a potential source of protein molecular indices of central nervous system function and pathology. However, various amounts of blood contamination in CSF may arise during sample acquisition. The concentration of protein in the CSF is only 0.2 to 0.5% that of blood. Minor contamination of CSF with blood during collection of the fluid may dramatically alter the protein profile confounding the identification of potential biomarkers. We have analyzed CSF and CSF spiked with increasing amounts of whole blood using proteomic techniques. We detected at least four blood specific highly abundant proteins: hemoglobin, catalase, peroxiredoxin and carbonic anhydrase I. These proteins can be used as blood contamination markers for proteomic analysis of CSF. Proteins in blood contaminated CSF samples were less stable compared to neat CSF at 37 degrees C suggesting that blood borne protease may induce protein degradation in CSF during sample acquisition. This analysis was aimed at identification of proteins found primarily in CSF, those found primarily in blood and assessment of the impact of blood contamination on those proteins found in both fluids.

Amino Acid Sequence↗

PubMed1998

Contaminant inclusion into protein crystals analyzed by electrospray mass spectrometry and X-ray crystallography.

The inclusion of protein contaminants into crystals of turkey egg white lysozyme (TEWL) was investigated by electrospray mass spectrometry of the dissolved crystals. The results show that significant amounts of the structurally related contaminant hen egg white lysozyme (HEWL) are included in the crystals of TEWL. The structurally unrelated contaminant RNAse A, on the other hand, is not included. The X-ray diffraction data statistics of a hybrid TEWL/HEWL crystal and an uncontaminated TEWL crystal were of similar quality. This indicates that, even though the crystals contain much higher levels of the contaminant than one would have expected after a recrystallization experiment, they are still suitable for X-ray diffraction experiments. However, attempts to detect the presence of the contaminant in the crystal by crystallographic structure refinement did not yield conclusive results.

Animals↗

PubMed2001

Changes in androgenic steroid profile due to urine contamination by microorganisms: a prospective study in the context of doping control.

Urine contamination by microorganisms may affect the interpretation of urinalysis in different areas of clinical diagnosis. This is particularly relevant in doping control. A prospective study was designed to assess the effects of urine contamination by selected pathogens on the endogenous androgenic steroid profile. Pooled urine from a healthy male volunteer with standard steroid profile compared with reference values for the Caucasian population was sterilized by filtration and stored in sterile glass tubes. Aliquots were inoculated with known amounts of 15 different organisms (bacteria, fungi, and moulds) and incubated at 37 degrees C for 2 weeks. Different markers of urine contamination, such as pH, deconjugation of steroids, and metabolic by-products, were determined. Alkalization of urinary pH was not a reliable indicator of urine contamination as several organisms grew in this medium and no alteration of this parameter was found. In uncontaminated urine, less than 10% of steroid glucuronide conjugates were spontaneously hydrolyzed. Higher rates of hydrolysis for sulfate conjugates were found. An unconjugated fraction higher than 10% of the total amount of testosterone was a reliable indicator of urine contamination. However, microbial production of testosterone or epitestosterone was not detected. In contrast, a few organisms were able to synthesize 5alpha-androstanedione, 5beta-androstanedione, and androstenedione using endogenous steroids as substrates.

Androgens↗

PubMed1997

Evidence from whole-sediment, porewater, and elutriate testing in toxicity assessment of contaminated sediments.

Bioassays with microorganisms are widely used as tools in estimating the potential risk of contaminated sediments. Although whole-sediment testing seems the most realistic approach to evaluate the bioavailability of contaminants in sediments, porewaters and aqueous extracts are frequently used. The object of this study was to compare whole sediment, porewater, and elutriate exposure of contaminated sediment simultaneously with two bacterial bioassays. Artificial sediment was spiked with five chemicals of different chemical and physical properties as single substances and as a mixture of all substances. Depending on the quality of the toxicants the test organisms were affected via aqueous phase (elutriate or porewater) or via solid phase (whole sediment). Sediment quality criteria based on the distribution of chemicals between sediment and aqueous phase and assessment of the toxicity of a sediment with water quality criteria were not confirmed by this study. The DHA solid-phase assay illustrated that threshold concentrations based on the NOEC values of single chemicals are not always sufficient to assess the risk of polluted sediments for organisms. It is suggested that for the evaluation of the potential hazard of a sediment contaminated with an unknown mixture of chemicals all exposure routes of contaminants should be examined by elutriate, porewater, and whole-sediment testing.

Bacillus cereus↗

PubMed2003

The effect of plants on the degradation and toxicity of petroleum contaminants in soil: a field assessment.

A field project located at the US Naval Base at Port Hueneme, California was designed to evaluate changes in contaminant concentrations and toxicity during phytoremediation. Vegetated plots were established in petroleum (diesel and heavy oil) contaminated soil and were evaluated over a two-year period. Plant species were chosen based on initial germination studies and included native California grasses. The toxicity of the impacted soil in vegetated and unvegetated plots was evaluated using Microtox, earthworm, and seed germination assays. The reduction of toxicity was affected more by contaminant aging than the establishment of plants. However, total petroleum hydrocarbon concentrations were lower by the end of the study in the vegetated plots when compared to the unvegetated soil. Although phytoremediation is an effective approach for cleaning-up of petroleum contaminated soil, a long-term management plan is required for significant reductions in contaminant concentrations.

Bacteria↗

PubMed1994

Organochlorine contamination in pinnipeds.

Organochlorines, such as PCBs and DDT, are ubiquitous contaminants. Most studies reporting concentrations of organochlorines in pinnipeds have investigated ringed, grey, and harbour seals. Very few studies have been carried out on pinnipeds from the southern hemisphere. Pre-1980, the highest mean wet-weight blubber concentrations of DDT and related metabolites (911 +/- 582 micrograms g-1) were recorded in sea lions from California. The highest pre-1980 blubber concentrations of PCBs (1470 +/- 922 micrograms g-1) were recorded in harbour seals from the Netherlands. In later studies, the highest blubber concentrations of PCBs have been recorded from grey seals of the Dee estuary, UK [46.79 (10.17-116.68) micrograms g-1]. The highest DDT concentrations measured in individual pinnipeds appear to be in the 1-15 micrograms g-1 range, and such levels have been recorded from ringed, grey, and harbour seals and Australian fur seals. There are problems in identifying trends based on different studies. These include the improvement in analytical methods with time and the lack of uniformity in analytical methodology between laboratories as well as in the biological material analyzed. Insufficient standardized studies have been undertaken for a clear picture of temporal trends in DDT and PCB concentrations in pinniped tissues to be identified. Reported results show variations in contaminant concentrations between pinniped colonies from different sites, and special reference has been made to comparison of contaminant burdens between the UK colonies. Insufficient standardized information is currently available for patterns of contamination in pinnipeds to be assessed on a global scale. Many, although not all, studies have shown evidence for age and sex correlation for organochlorine concentrations in pinnipeds; male seals continuing to accumulate certain organochlorines throughout their lives; female seals accumulating these compounds until maturity when they lose part of their body burdens to their offspring via transplancental transfer and, more importantly, via lactation. The ability of pinnipeds to metabolize organochlorine compounds appears to be less well developed than in terrestrial mammals and seems to vary between seal species. Reported effects on pinnipeds, which have been suggested to result from organochlorine contamination, include skeletal deformities and impacts on reproduction, such as uterine blockages. The evidence of a relationship between recent epizootics in marine mammal populations and organochlorine pollution suggests that viruses and pollution are potential significant contributors to mortalities, but other factors, such as unseasonably warm temperatures and high seal densities, cannot be precluded.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1988

Bioengineering issues related to in situ remediation of contaminated soils and groundwater.

This chapter presents some of the engineering challenges in biological degradation of organic contaminants in surface soils and the subsurface environment. Extraction of contaminants from the subsurface is generally costly, slow, and difficult. This has led to an interest in using in situ techniques for biodegradation of contaminants. For some contaminants that can be readily used as primary energy sources for bacteria with or without the presence of oxygen, bacterial removal is relatively simple and, in some situations, occurs naturally. In other cases, such as hydrocarbon spills, in situ treatment is still attractive, but has the added cost and difficulty of supplying required oxygen and nutrients for the fairly efficient aerobic oxidation. There are some indications that hydrocarbons may be biodegraded in the absence of oxygen; but, in these cases, the rates of degradation appear to be slow. More research in this area is desirable. The major challenge to both engineers and scientists lies in the decomposition of hazardous chemicals that appear to be transformed by the process of co-metabolism, or else are so low in concentration that they can only serve as secondary substrates. In either case, primary substrates are required to supply the major energy requirements for bacterial growth and/or for activation of enzymes necessary for the transformation. Engineering experience in the utilization of such processes for degradation of contaminants in the environment is very limited. Little is currently known about substrate interactions and how to optimize the bacterial transformations. Chemical requirements for achieving co-metabolism are high. In addition, knowledge is lacking about methods for getting the correct amounts of chemicals to the locations where needed and in the form needed. The solution of these important issues presents a significant challenge to the engineering and science communities, requiring both basic laboratory studies and field demonstrations in well-characterized environments.

Bacteria↗

PubMed1998

Population responses to contaminant exposure in marine animals: influences of genetic diversity measured as allozyme polymorphism.

Current understanding of the genetic and metabolic basis of relations between heterozygosity and animal performance under non-polluted conditions is relevent to interpreting apparently inconsistent findings concerning the relative advantage of allozyme polymorphism during contaminant exposure. Many interrelated factors which may influence and even compromise those relations include species (lifestyle, reproductive behaviour etc), lifestage, environmental influences and a variety of background genetic effects (limited parentage, null alleles, aneuploidy, genomic imprinting etc). Nevertheless, there is some promise that single-locus responses may be diagnostic for specific pollutants. In addition, limited evidence to date supports the a priori expectation that reduced energy requirements for maintenance metabolism may facilitate longer survival of multiple-locus heterozygotes during exposure to contaminants with toxic effects that result either in the reduced acquisition or availability of metabolizable energy, and/or a reduction in the efficiency with which metabolizable energy is used to fuel metabolic processes. More work is required to fully establish this trend in response to specific contaminant types, to assess any direct consequences of underlying differences in protein metabolism, and to resolve the interactive effects of contaminant mixtures. But the functional value of genetic variation within populations is confirmed. Reduced genetic diversity may not only compromise the capacity of an impacted population for genetic adaptation in the face of further environmental challenge, but may also result in increased energy requirements, lower production efficiency and reduced reproductive output. These metabolic consequences of reduced genetic polymorphism would further lower that population's potential for survival under lethal conditions of contaminant exposure, and also affect the genetic makeup of populations through differential reproduction under conditions of sublethal stress.

Animals↗

PubMed1996

Isolation of hexavalent chromium-reducing anaerobes from hexavalent-chromium-contaminated and noncontaminated environments.

Hexavalent chromium [Cr(VI)], is a toxic, water-soluble contaminant present in many soils and industrial effluents. Bacteria from various soils were examined for Cr(VI) resistance and reducing potential. Microbes selected from both Cr(VI)-contaminated and -noncontaminated soils and sediments were capable of catalyzing the reduction of Cr(VI) to Cr(III) a less toxic, less water-soluble form of Cr, demonstrating the utility of using a selection strategy for indigenous Cr(VI)-reducing bacteria in a bioprocess. As a result, indigenous Cr(VI)- reducing microbes from contaminated sites should provide the means for developing a bioprocess to reduce Cr(VI) to Cr(III) in nonsterile effluents such as those from soil washes. This approach also avoids the contamination problems associated with pure cultures of allochthonous microorganisms. In addition the apparent ubiquity of Cr(VI)-reducing bacteria in soil and sediments indicates potential for in situ bioremediation of Cr(VI)-contaminated soils and ground water.

Bacteria, Anaerobic↗

PubMed1992

Uptake of environmental contaminants by small mammals in pickleweed habitats at San Francisco Bay, California.

Small mammals were live-trapped in pickleweed (Salicornia virginica) habitats near San Francisco Bay, California in order to measure the uptake of several contaminants and to evaluate the potential effects of these contaminants on the endangered salt marsh harvest mouse (Reithrodontomys raviventris). Tissues of house mice (Mus musculus), deer mice (Peromyscus maniculatus), and California voles (Microtus californicus) from nine sites were analyzed for chemical contaminants including mercury, selenium, cadmium, lead, and polychlorinated biphenyls (PCBs). Concentrations of contaminants differed significantly among sites and species. Mean concentrations at sites where uptake was greatest were less than maximum means for the same or similar species recorded elsewhere. Harvest mice (Reithrodontomys spp.) were captured only at sites where concentrations of mercury or PCBs were below specific levels in house mice. Additional studies aimed at the protection of the salt marsh harvest mouse are suggested. These include contaminant feeding studies in the laboratory as well as field monitoring of surrogate species and community structure in salt marsh harvest mouse habitats.

Animals↗

PubMed1996

Development of greenhouse screening for resistance to Aspergillus parasiticus infection and preharvest aflatoxin contamination in peanut.

Aspergillus flavus Link ex Fries and A. parasiticus Speare can invade peanut kernels and under certain environmental conditions produce unacceptable levels of the mycotoxin aflatoxin. A concerted effort is underway to reduce aflatoxin contamination in peanut and peanut products. A potentially effective method of control in peanut is the discovery and use of genes for resistance to either fungal invasion or aflatoxin formation. The objective of the present experimental study was to develop an effective and efficient procedure for screening individual plants or pods of single plants for resistance to invasion by the aflatoxigenic fungi and subsequent aflatoxin production. Methods of obtaining adequate drought-stress and fungal infection were developed through this series of experiments. By completely isolating the pods from the root zone and imposing drought-stress only on pegs and pods, high levels of fungal infection were observed. High amounts of preharvest aflatoxin accumulation were also produced by completely isolating the pods from the root zone. Mid-bloom inoculation with A. parasiticus-contaminated cracked corn and drought-stress periods of 40 to 60 days were the most effective procedures. This technique was used to assess peanut genotypes previously identified as being partially resistant to A. parasiticus infection or aflatoxin contamination, and segregating populations from four crosses. Variability in aflatoxin contamination was found among the 11 genotypes evaluated, however, none were significantly lower than the standard cultivars. Broad-sense heritability of four crosses was estimated through evaluation of seed from individual plants in the F2 generation. The heritability estimates of crosses GFA-2 x NC-V11 and Tifton-8 X NC-V11 were 0.46 and 0.29, respectively, but mean aflatoxin contamination levels were high (73,295 and 27,305 ppb). This greenhouse screening method could be an effective tool when genes for superior aflatoxin resistance are identified.

Aflatoxins↗

PubMed1991

Contaminated sediments from tributaries of the Great Lakes: chemical characterization and carcinogenic effects in medaka (Oryzias latipes).

Sediments from four inshore industrial sites and a reference site in the Great Lakes were extracted with organic solvents to produce a crude extract, which was separated on alumina into two fractions: predominantly polycyclic aromatic hydrocarbons; and predominantly nitrogen-containing polycyclic aromatic compounds. Crude extracts were redissolved in acetone and analyzed by gas chromatography and gas chromatography-mass spectrometry. The acetone-redissolved crude extracts from the four industrialized sites contained 5.6-313.3 micrograms total polycyclic aromatic compounds/g sediment and 3.0-36.4 micrograms other compounds/g sediment. In addition to the typical EPA priority pollutants, a substantial amount (228.7 micrograms/g sediment) of alkyl-polycyclic-aromatic compounds was detected in sediments from one of the industrialized sites. Extracts from the reference site contained 1.55 micrograms total polycyclic aromatic compounds/g sediment. Medaka (Oryzias latipes) were exposed to multiple pulse doses of acetone-redissolved extracts and fractions. Medaka were also exposed to a known carcinogen, methylazoxymethanol acetate, to verify that chemicals produced tumors in the test fish. Acetone-redissolved extracts and fractions from contaminated sediments were toxic to medaka. Fin erosion and non-neoplastic liver abnormalities were more prevalent in medaka after exposure to acetone-redissolved extracts and fractions from contaminated sediments. Neoplasms previously associated with chemical exposure in wild fishes were induced in medaka exposed to acetone-redissolved extracts and fractions from two of the contaminated sites, but not from the reference site or controls. These findings further support the hypothesis that chemical contaminants in sediments are involved in epizootics of neoplasms in wild fishes at contaminated sites.

Animals↗

PubMedDate not supplied

Environmental contaminant concentrations in biota from the lower Savannah River, Georgia and South Carolina.

Planned harbor expansion and industrial developments may adversely affect the economically important aquatic resources of the lower Savannah River, including those at the Savannah National Wildlife Refuge. To establish the present level of chemical contamination in this system, we collected a total of 102 samples of nine species of fish and fiddler crabs (Uca pugilator) from eleven sites in the lower Savannah River and on the Savannah National Wildlife Refuge, and analyzed them for concentrations of organochlorine chemicals, aliphatic and aromatic petroleum hydrocarbons, and 13 elemental contaminants: aluminum, arsenic, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, nickel, selenium, and zinc. Residues of DDT (mainly as DDE), trans-nonachlor, dieldrin, Aroclor 1260, mirex, and petroleum hydrocarbons were common in fish from the lower Savannah River, but concentrations were below those warranting environmental concern. In general, the concentrations of elemental contaminants also were low; however, arsenic, cadmium, and chromium concentrations were elevated in fish from river stations near the city of Savannah, and lead was elevated in samples from the National Wildlife Refuge. Contamination of the lower Savannah River by organic and elemental contaminants, as indicated by concentrations in fishes and fiddler crabs, did not appear to pose a hazard.

Animals↗

PubMed1991

Hepatic activities of xenobiotic metabolizing enzymes and biliary levels of xenobiotics in English sole (Parophrys vetulus) exposed to environmental contaminants.

English sole (Parophrys vetulus) are susceptible to the development of hepatic disease, including neoplasia, as a result of environmental exposure to polycyclic aromatic hydrocarbons (PAHs). The metabolism of PAHs, believed to be an essential factor in the development of neoplasia, has received considerable study in English sole, except that xenobiotic metabolizing enzymes (XMEs) have not been well-studied in this species. In the present work, the activities of hepatic aryl hydrocarbon hydroxylase (AHH), glutathione-S-transferase (GST), and epoxide hydrolase (EH) were measured in English sole exposed to several organic xenobiotics. These studies included an examination of the effects of captivity, the short-term responses of hepatic XME activities to several xenobiotic compounds, and detailed studies of the time- and dose-responses of hepatic XME activities to both a representative carcinogenic PAH (benzo[a]pyrene) and to a complex mixture of contaminants extracted from a sediment collected from a polluted area of Puget Sound, WA. Additionally, during the captivity and time- and dose-response studies, the levels of fluorescent aromatic compounds (FACs) were measured in the bile of the fish, both to provide an estimation of contaminant exposure and to evaluate the time- and dose-responses of this measure. The results of the captivity studies showed that the levels of FACs in bile were most affected by captivity, primarily as a result of changes in feeding status. The results of the exposure studies showed that xenobiotic metabolism, as reflected in hepatic activities of XMEs and levels of FACs in the bile, is altered by exposure to environmental contaminants. Whereas hepatic AHH activity could be rapidly and substantially increased by such exposure, activities of GST and EH were not affected, even up to 42 days after exposure. Moreover, because fish were exposed to a wide range of doses of chemicals or mixtures of chemicals which are known to be present in contaminated estuaries, and the responses of the hepatic AHH system and the levels of FACs in bile were measured at several time periods after exposure, the results provided substantial validation for the use of these two measures as bioindicators of exposure to environmental contamination in benthic fish.

Animals↗

PubMed1991

Cs-134/137 contamination and root uptake of different forest trees before and after the Chernobyl accident.

The Cs-134/137 activities were measured from different tree organs of spruce, larch and sycamore maple. Two locations in South Bavaria were monitored during a period of 2.5 years following the Chernobyl accident. Samples taken in 1985 allow to determine the Cs-137 contamination before the accident. Increasing Cs-137 activities from older to younger needle years of Picea abies caused by root-uptake of the global weapons' fallout are due to the high phloem mobility of this element and the remaining of the needles at the tree for about 6-7 years. In contrast, the Cs-137 activity was much smaller in leaves of larch and sycamore maple. After the Chernobyl accident, the higher contamination of spruce greater than larch greater than sycamore maple is dependent on the roughness of bark, absolute bark surface and the existence of leaves during the deposition of Chernobyl-derived radioactivity. The Cs-134/137 activity (Bq/kg d.w.) was about 25-times higher in bark compared to wood of Picea abies and 1.5-4.7 times higher in directly contaminated twig-axes than in leaves. Till the end of the investigation the major contamination of the shoots was due to direct deposition of cesium on the trees. A maximum of 5-15% of the total activity of the directly contaminated branches of the plants was calculated to be part of root-uptake, depending on the amount of initial retention. 20% of the translocated cesium into new leaves of larch and about 50% into sycamore maple resulted from root-uptake 2.5 years after the accident.

Accidents↗