Chris Kollöffel

Polycyclic aromatic hydrocarbons in soil and plant samples from the vicinity of an oil refinery.

Soil samples, and samples of leaves of Plantago major (great plantain) and grass (mixed species) were collected from the vicinity of an oil refinery in Zelzate, Belgium, and analysed for seven polycyclic aromatic hydrocarbons (PAHs). The samples from the site adjacent to the refinery (site 1) contained very high total PAH-concentrations: namely 300, 8 and 2 microg/g dry wt. for soil, P. major and grass, respectively. Concentrations in samples from more remote sites (up to 4 km from the refinery) were a factor of 10-30 lower than those from site 1, but between them the differences were small. The PAH-profiles of the plant samples, in contrast with those of the soil samples, appeared to shift to higher contributions of gaseous PAHs with increasing distance from the refinery. This can be explained by particle-bound PAHs being deposited closer to the source than gaseous PAHs. It is suggested that particle-bound deposition is relatively more important for deposition to soil than to plants, due to blow-off and wash-off of the compounds from the leaves. The total PAH-concentrations in the leaves of P. major were higher than those measured in the grass samples, probably due to differences in aerodynamic surface roughness, leaf orientation and/or leaf age. However, the concentration ratios of P. major/grass were not constant for the different sites, varying from 1.2 to 8.8. Therefore, it appears that a precise prediction of PAH-concentrations for one plant species from known concentrations of another species is not possible. When errors in predicted concentrations need to be smaller than a factor of approximately 10, the sampling strategy has to be focussed on all species of interest.

Dry deposition of atmospheric polycyclic aromatic hydrocarbons in three Plantago species

The concentrations of polycyclic aromatic hydrocarbons (PAHs) in the leaf wax of three Plantago species were determined weekly for 3 weeks. The almost glabrous, free-standing leaves of Plantago major and the sparsely hairy Plantago lanceolata leaves were more heavily contaminated with low molecular weight (MW) PAHs (MW < 228) than the densely hairy, partly overlapping Plantago media leaves. This may be caused by the lower canopy roughness (higher aerodynamic resistance), the higher amount of leaf hairs (higher boundary resistance), and/or the higher leaf overlap (smaller accessible leaf area) of P. media. On the other hand, PAHs with MW ≥ 252 tended to show higher concentrations in P. media than in the other two species. This is likely caused by the dense layer of hairs on P. media leaves, which can efficiently intercept the largely particle-bound high MW PAHs. When the PAH concentrations were normalized to projected leaf surface area, the differences between P. media and the other two species became significant (p < 0.05) for the high MW PAHs, while the differences for the low MW PAHs decreased. Although the differences in PAH concentrations between species are relatively small (factor 2-5), this study clearly shows that plant architecture and leaf hairs influence the dry deposition of PAHs.

Leaf wax of Lactuca sativa and Plantago major

Abstract Wax layers of plants are able to accumulate semivolatile organic compounds (SOCs) from the atmosphere. In this study, the composition of the leaf cuticular waxes of lettuce ( Lactuca sativa ) and common plantain ( Plantago major ) was determined for future studies on the role of cuticular waxes in the uptake and bioaccumulation of SOCs. In addition, to find a suitable extraction solvent to be used in these studies, the extraction efficiency of several solvents for the cuticular wax of the plants was studied. Leaf wax of L. sativa consists mainly of long-chain linear alcohols and minor amounts of fatty acids, while the major components of leaf wax of P. major are the free polar triterpene acids, oleanolic and ursolic acid, and the linear alkanes C 27 H 56 C 33 H 58 . The wax composition of both species only slightly changes with leaf developmental stage. This property makes them highly suitable as test plants in studies on uptake of SOCs. The waxes of both plant species are readily extractable with chloroform, toluene and dichloromethane. A mixture of chloroform and methanol 2:1 additionally extracted internal lipids and chlorophyll and, therefore, is not suitable. The apolar solvent, n -hexane, did not extract the triterpene acids of P. major . However, this solvent readily extracted the relatively apolar leaf wax of L. sativa . Since the extraction of SOCs (also from deeper embedded wax layers) can only be efficient if all the components of the cuticular wax are removed, we recommend to test the extraction efficiency of the solvent for each plant species beforehand.

Ornithine carbamyltransferase activity from the cotyledons of developing and germinating seeds of Vicia faba

Abstract During maturation the ornithine carbamyltransferase activity from cotyledons of Vicia faba sharply decreased. It declined further during subsequent germination. On the other hand, arginase activity was low in mature, air-dry seeds but increased considerably during germination. After centrifugation at 40 000 g, more than 90% of the ornithine carbamyltransferase activity remained in the supernatant. The fractions containing tightly coupled mitochondria, showed hardly any omithine carbamyltransferase activity.