Accumulation of 99Tc in duckweed Lemna minor L. as a function of growth rate and 99Tc concentration.

This study focuses on the question of whether short-term studies can be used to forecast the accumulation of the long-lived fission product 99Tc in duckweed, Lemna minor L., grown in the field; in other words, are the accumulation parameters independent of changing growth rates typical of natural populations of duckweed. Two processes determine the 99Tc accumulation: (i) uptake and release of 99TcO4-, characterised by a concentration factor, Kd, and (ii) first-order reduction and complexation of TcVII, characterised by kred. At various 99Tc concentrations, the growth, total Tc and TcO4- accumulation were monitored over 10 days; parameters were fitted and compared with earlier results. Both Kd and kred turn out to be independent of time, concentration and growth rate up to a concentration of 10(-6)mol l(-1) 99TcO4-. Concentrations above this level result in toxic effects. The Tc accumulation in field populations of duckweed at Tc concentrations which generally occur in the environment can be forecasted by using the results from short-term experiments.     

Interspecies comparison of lichens as biomonitors of trace-element air pollution

The linearity of the interspecies relation between the elemental contents in Parmelia sulcata and Lecanora conizaeoides, sampled in a polluted area, was examined by the function y=az+b and yz ^–1=a+bz ^–1, with y and z being the elemental content in Parmelia and Lecanora, respectively. For As, Co, V and Zn significant positive a and b values were found, allowing interspecies calibration. For Br, Cd, Cr, Fe, La, Sb, Se and W the a values were zero and the b values were positive, indicating saturation of Parmelia and thus ruling out interspecies calibration. For Cu a part of the data set showed saturation effects in Lecanora. The results showed that the average concentration ratio could not be used for intercalibration purposes, because the concentration ratios were dependent on the concentrations.     

Availability of copper from phytoplankton and water for the bivalveMacoma balthica. I. Separation of uptake pathways using the radiotracer64Cu

To study the role of food in Cu accumulation by bivalves, algae spiked with Cu can be used. With spiked algae, however, redistribution of Cu between the disolved solved and the particulate phase hampers the assessment of the contribution of food. This occurred in efforts to label algae with the radiotracer⁶⁴Cu. A method was designed to overcome this problem of redistribution. By adding excess EDTA to seawater, the biological availability of dissolved Cu was minimized. The effectiveness of complexation by EDTA was controlled through adsorption onMacoma balthica shells and uptake inM. balthica tissue.Communication number 644 of the Centre for Estuarine and Coastal Ecology, Yerseke, The Netherlands     

Bioaccumulation behaviour of transplants of the lichen Flavoparmelia caperata in relation to total deposition at a polluted location in Portugal

This experiment compares the short and long time element accumulation behaviour of transplants of Flavoparmelia caperata lichen thalli and total deposition in an atmospheric polluted area. It was found that lichens exposed for a short time behaved differently from lichens in cumulative exposition suggesting the presence of acclimatization behaviour. The lichen transplant elemental content does not unequivocally represent the average or cumulative environmental availability of the exposure period. Reflection characteristics depend on the element and the lichen physiological conditions. Good correlations between lichen elemental contents and total deposition were obtained when a physiological lichen parameter was introduced in a mathematical model, suggesting that metabolically mediated accumulation is important.     

The uptake and distribution of cadmium in tomato plants as affected by ethylenediaminetetraacetic acid and 2,4-dinitrophenol

The uptake and distribution of cadmium in tomato plants (Lycopersicon esculentum, Mill, cv. Tiny Tim) were examined with and without the presence of ethylenediaminetetraacetic acid (EDTA) as chelating agent and 2,4-dinitrophenol (DNP) as metabolic inhibitor. Eight-week-old intact and derooted tomato seedlings were used in hydroculture experiments with cadmium applied as (115)Cd(NO(3))(2) in a range of concentrations. Measurements of the (115)Cd content of roots, stems and leaves were carried out by gamma-ray spectroscopy. The data showed that applications of both EDTA and DNP resulted in reduced total Cd accumulation in the plants, but relatively enhanced Cd transport into the above-ground plant parts. The Cd mobility in the transport channels in the shoots was increased by EDTA in both intact and derooted plants. Application of DNP leads to increased relative Cd import to leaves in derooted plants, but a reduced import into leaves of intact plants. These results suggest that Cd-complexes are formed in root cells before root-to-shoot transport. Furthermore, initial Cd uptake may be associated with adsorption on the negative charges of the cell walls of the root system. The high Cd mobility in shoots, in experiments with intact plants and Cd-EDTA application, indicates the possibility of simultaneous uptake of Cd and EDTA, possibly as a Cd-EDTA complex.     

Biomonitoring of trace element air pollution: principles,possibilities and perspectives

This paper discusses the biomonitoring of trace element air pollution. Much attention is given to both lichens and mosses as the dominant plant species used in biomonitoring surveys. Biomonitoring is regarded as a means to assess trace element concentrations in aerosols and deposition. This implies that the monitor should concentrate the elements of interest and quantitatively reflect its elemental ambient conditions. Environmental impact on the biomonitor's behaviour is viewed as resulting in changes in the dose-response relationships. The current literature is briefly reviewed, for plant's behaviour modelling, for laboratory studies on physiological processes responsible for accumulation, retention and release, and for field work on quantification of dose-response relationships. Monitoring of elemental atmospheric availability is presented as deriving its relevance from presumed impact on both ecosystem performance and human health; source apportionment is regarded as an important parallel result for purposes of emission regulatory management. For source apportionment, the paper argues in favor of multi-elemental determinations, supplemented by information on organic compounds and elemental chemical forms. Furthermore, the discussion points towards more explicit coupling of biomonitoring data to knowledge and databases on both emission registration, ecosystem performance and human health. This means that multidisciplinary programs should be set up, which accommodate expert inputs from biomonitoring, emission control programs, analytical chemistry, ecology, and epidemiology.     

Correlating element atmospheric deposition and cancer mortality in Portugal: data handling and preliminary results

This study, framed within geographical epidemiology, presents preliminary findings concerning the association between the concentrations of chemical elements obtained through atmospheric biomonitoring with lichens and cancer mortality in the Portuguese population. Exploratory analyses were performed to identify potential confounders for the relationships between chemical elements and neoplasm mortality and to assess the extent of their interference. The results of this study highlight some methodological and conceptual difficulties inherent to observational and geographical studies, in the specific context of the Portuguese population, and the challenge posed by the large numbers of pollutants considered.     

Judging Survey Quality: Local Variances

The present study was undertaken to explore possibilities to judge survey quality on basis of a limited and restricted number of a-priori observations. Here, quality is defined as the ratio between survey and local variance (signal-to-noiseratio). The results indicate that the presented surveys do not permit such judgement. Furthermore, the discussion alsosuggests that the 5-fold local sampling strategies do not merit any sound judgement in about 10% of all cases.The results further imply that surveys will benefit from procedures, controls and approaches in sampling and sample handling, to assess both average, variance and the nature of the distribution of elemental concentrations in local sites. This reasoning is compatible with the idea of the site as a basic homogeneous survey unit, which is implicitly and conceptually underlying any survey performed.     

Relations between sulphate,ammonia, nitrate,acidity and trace element concentrations in tree bark in The Netherlands

Bark flakes were sampled in a biomonitoring survey throughout The Netherlands. Tree species used were oak (65 samples) and non-oak (58 samples) (poplar, elm, willow). Bark elemental analysis was carried out for As, Br, Ca, Cd, Ce, Co, Cr, Cs, Fe, Hg, K, La, Na, Ni, Pb, Rb, Sb, Sc, Se, Sm, Th, and Zn. Furthermore, bark acidity, SO₄, NH₄ and NO₃ were determined. Further variables introduced into the data-set were DIST (closest distance to sea water) and the dummy variably OAK (tree species).Straightforward multivariate correlation analysis was performed to check the effects on bark metal retention of the non-metal pollutants SO₄, NH₄ and NO₃, and of bark acidity. The OAK variable served to identify species-specific metal and non-metal pollutant behaviour. The DIST variable was used to visualize geography(source)-related variations in bark metal and non-metal pollutant concentrations, and to account for the non-random distribution of OAK and non-OAK tree species.The results indicate that the non-oak and oak bark samples may be combined to form 123 samples containing data-set for As, Br, Cd, Ce, Co, Fe, La, Na, Sc, Sm, Th, Zn, NH₄, NO₄, SO₄ and acidity, but not for Rb, Cs, Se, K, Ni, Pb and Sb (species-specific) and for Ca and Hg (H⁺-dependent). In the presented data-set, bark sulphate, ammonia and nitrate could not be shown to significantly affect bark metal retention.