Joyce E. Sloof

Lichens as quantitative biomonitors for atmospheric trace-element deposition, using transplants

At 8 stations spread over The Netherlands transplants of Parmelia sulcata Taylor and impregnated cloth (rag) as a non-biological monitor were exposed to the atmosphere for periods of up to 12 months. At the same stations bulk (wet and dry) deposition was collected on a monthly basis. Quantitative linear relationships between the concentrations in the 12 months exposed lichens and the cumulative bulk deposition during the same period, yielded accumulation factors for cobalt, scandium and zinc. The lichens reflected the bulk deposition. The ratios between the accumulation factors for cobalt, scandium and zinc in lichens and rag are comparable. This gave some insight in the uptake mechanism, probably mainly passive, such as particulate trapping, adsorption/desorption and/or ion exchange.

Lichens as biomonitors for radiocaesium following the chernobyl accident

Caesium-137 resulting from the Chernobyl accident was monitored in lichens in The Netherlands. Caesium-137 activity in Parmelia sulcata ranged from 550 to 6100 (average 2500) Bq kg−1 dry weight. The similarity between the lichen data (geographical 137Cs activity gradients and radioactivity values) and data of wet and dry deposition, indicate the validity of lichen monitoring of atmospheric 137Cs. The ratio between the 137Cs activity deposited per unit surface area (m2) was approximately one. Measurements of 137Cs accumulation in Xanthoria parietina show that the activity concentration could be expressed both on a dry weight and on a contour surface area basis. The determination of the biological half-life of 137Cs in lichens was shown to be subject to sources of error such as growth and non-atmospheric/indirect 137Cs influxes.

Substrate influence on epiphytic lichens

The origin of the presence of soil elements in the epiphytic lichen Lecanora conizaeoides was investigated in an area of heavily polluted soil (The Broekpolder The Netherlands). Analysis results of lichens, bark and tree rings of the supporting trees indicated that for As, Co, Cr, Cu, Fe, Hg, Sc and V the levels in lichens may be considered to originate from wet and dry deposition. The Cd, Mn and Zn levels in lichens might have originated from both wet and dry deposition and the substrate bark. For these three elements, in particular, accumulation characteristics in lichens should be further investigated.

The use of Monte Carlo methods in factor analysis

Abstract Monte Carlo techniques are introduced in target transformation factor analysis (TTFA), in combination with the concept of the principal factor model, in order to account for local variances in the data set and to estimate the uncertainties in the obtained source profiles. The new method is validated using several types of artificial data sets. It was found that application of the Monte Carlo method leads to a significant improvement of the accuracy of the derived source profiles in comparison with standard TTFA. From the introduction of (known) error sources to the artificial data sets it was found that the source-profile reproduction quality is optimal if the magnitudes of the Monte Carlo variations are chosen equal to the magnitudes of the introduced errors.

Kinetics of cadmium uptake by green algae

The kinetics of cadmium uptake by Selenastrum capricornutum Printz was studied at 21 °C and 0 °C and at four different concentrations of free cadmium (10−9, 10−8, 10−7 and 10−3 M). The free cadmium concentrations in the medium were kept constant through buffering by a chelating agent (NTA).Initial uptake occurred within 10 min at both temperatures, indicating a fast process. At 21 °C, the cadmium uptake increased during the experimental sampling times from 0.12 to 50 h, whereas at 0 °C, the cadmium uptake remained constant after the first sampling time. Apparently, two different processes were involved in cadmium uptake, a first fast, probably passive process and a second slower, possibly physiological process.The cadmium uptake processes are described with a generalized metalligand complex formation model. The experimental dissociation constants for the fast (KR,F) and the slow process (KR,S) were reproducible for different experiments and they were both in the order of 5 10−6 mol L−1. For the slow process, the uptake- and release rate constants (k1 and k2) were quantified; for two experiments, the mean value for ki was 111±28 L mol−1 h−1 and the mean value for k2 was (5.1±1.8) 10−4 h−1. These values were calculated using the fitted value of the cadmium uptake in the fast process.

On the uptake and release of zinc (65Zn) in the growing alga Selenastrum capricornutum Printz.

A Zn- and pH-buffered medium was used to study the accumulation of Zn in batch-cultured algae (Selenastrum capricornutum Printz.). All experiments were carried out using (65)Zn radiotracers, which were measured by gamma-ray spectrometry. Zinc was applied in the presence of nitrilotriacetic acid (NTA), leading to free Zn(2+) concentrations ranging from 4.2 x 10(-11) to 1.6 x 10(-7) mol litre(-1). During the 75-h experiments, the rates of Zn influx and efflux were determined, the latter with full consideration for algal growth rates. Algal growth stopped completely at a free Zn(2+) concentration of 1.6 x 10(-8) mol litre(-1). Initial Zn binding was determined and, based on free Zn(2+) concentrations, presented by the apparent dissociation constant K(diss) and capacity C as 4.6 x 10(-9) mol litre(-1) and 19.8 x 10(6) mol gDW(-1), respectively. The rate constant of Zn efflux could be calculated as a constant 0.021 +/- 0.003 h(-1), irrespective of the Zn concentrations applied. The rates of Zn influx were expressed by the V(max) and K(M) values as 3.3 x 10(-10) mol gDW(-1) s(-1) and 6.3 x 10(-9) mol litre(-1), respectively. These values, which are based on applied free Zn(2+) concentrations, are compatible with the operation of a high-affinity low-concentration carrier mechanism. The results suggest that, under the conditions applied, free Zn(2+) may be the most relevant Zn species for Zn uptake; furthermore, relative growth rate may be regarded as a relatively sensitive signal for Zn stress circumstances.

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.

Application of Monte Carlo-assisted factor analysis to large sets of environmental pollution data

Abstract Target Transformation Factor Analysis (TTFA) has been applied to large data sets of trace element concentrations in lichens with the aim to resolve sources of environmental pollution. The concept of the principal factor model is used in order to account for local variances in the data set. Monte Carlo techniques are used to estimate the uncertainties in the obtained source profiles. It was found that the Monte Carlo method offers a new approach to the problem of the determination of the number of factors to be used in the analysis.

Patterns in trace elements in lichens

Epiphytic lichens were sampled in a Dutch national monitoring survey, which was carried out twice within 5 yr. The samples were analyzed by neutron activation analysis. The lichen data sets were presented in plots of geographical concentration patterns. These gave insight in the possible location of pollution sources. Comparison of the lichen data sets showed changes in the (geographical) concentration patterns with time. For all elements the areas with enhanced concentration classes increased from 1982–1983 to 1986–1987. The most striking change in concentration pattern was found for Cd. The application of factor analysis techniques in interpreting the concentration data yielded the composition of the various polluting components, which may facilitate identification of the associated sources.

Pattern recognition in lichens for source apportionment

Abstract Monte-Carlo-assisted factor analysis has been applied to a lichen data set, obtained from a monitoring survey on a national scale in The Netherlands for source apportionment purposes. The factor analysis as applied revealed 10 factors, of which 8 could be interpreted in terms of realistic sources of pollution. Geographical distribution patterns of the factor values were used to facilitate and to support the identification of the associated sources.