Zs. P. Komáromy szerk.: Studia Botanica Hungarica 16. 1982 (Budapest, 1982)

Hably, Lilla: The relation between Pb-pollution along mainroads and the trace element-composition in soil and vegetation (Examination of section rectangular to M3 mainroad)

even more harmful for children. According to data of the World Health Organization the daily lead consumption of children is 300 ug/day. This is the upper limit which their organism can still tolerate although not without dangerous effects. Lead gets integrated in the biochemical system of the body, inhibits the functioning of p-amino levulin acid dehidrataze (ALAD) enzime, and interfers with the hémoglobine structure. Normally the Pb-level of the blood is 0.25 ppm; in polluted areas this may rise significantly. Researches so far have been confined mainly to the indication of lead and this is the stage researches in Hungary have reached till today. Other tests refer to the changes in human organisms, caused by the harmful effect of lead, a third group goal is to clarify in what processes lead has a role to play and with what consequences. Our present examinations, in addition to the detection of lead, try to find explanation for the relations of lead to other trace elements, to the pH, the organic material content, clay mineral and carbonate content. Within these examinations we attempted to explain the factors influencing the trace element composition as well as the reasons for changes and connections. These examinations are predominantly of agrogeological significance. The trace element content of soils is always in connection with the plants living in them. It is not irrelevant what kinds of factors control what quantities of trace elements can be integrated, and regularities of their changes. The examination of some plant samples may reveal the connection between the soil and the trace element-composition of plants. We took samples from a section at right angle to the mainroad. Thus in this study first of all the "road-effect" is demonstrated which exerts its harmful influence not only by means of lead pollution but also by its influence on a great number of other parameters. Its destructive role can be empirically observed in the must susceptible natural vegetation and in the fauna. A scientific explanation makes it possible through the knowledge of these effects to protect them against it. This is of special significance today, when conservation areas, forests and fields are broken by an ever increasing number of highways. These roads change the geochemical environment, thus fundamentally changing the outward appearance of the area can be the cause of the perishing of rare and protected plants. I. Sampling and Testing Methods The sampling area is the M 3 mainroad, between Mezőkövesd and Mezőnyárad. Geographically this territory belongs to the Great Hungarian Plain, and is situated near the Downs of the Bükk. Geologically it is an extremely complex territory bordered by great tectonic lines and its deeper structure having not been fully penetrated yet. 1. Sampling In order to clarify the role of the soil-section and the bedrock we took samples from 2meter-deep sections (holes dug in the soil). The sampling holes were dug in right angle to the M 3 road at a point on either side of the road between Mezőkeresztes and Mezőnyárád (Fig. 1). This method was chosen because the direction of the wind may influence the areal distribution of the lead coming from the exhaust fumes. The sampling sites were selected so as to show whether the quantity of lead altered while getting further away from the road, and if so, what the measure of the change was. The relatively distant sampling points could give an estimate of the background trace element-distribution of the area. The samples were taken from each hole at spaces of 20 cm, they were put into nylon bags and numbered, and written records were made of the observations. Our area is flat, slightly sloping to the south at larger distances. Nearby flows the Tardi brook which crosses the road not far from our sampling lines. The furthest sampling points were 35 m north of the road and 106 m to the south from the surface of the road. The area has lost its natural vegetation since on either side of the road, at a distance of about 20-40 m the land is cultivated. To the north, about 10-30 m away from the road there is a wide patch of shrubs. Apart from some natural species, the vegetation consists of planted and adventive species such as Celtis, Amorpha fruticosa. From these and some others samples were taken. This belt of shrubs and trees is parallel with the mainroad. In right angle