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)

Zone 0-20 cm, that is the first sampling level. It is clearly seen in Figures 2-9 that the soluble trace element content of all the elements (Mn + Zn + Cu + Pb) is almost always high. This phenomenon could suggest that the enrichment occurred under surface effect thus it is bound up with organic materials. This is refuted by the fact that it is only Zn which shows constantly good correlation with the organic material content. Fig. 10 clearly shows that the accumulation levels are grouped around certain pH-levels independently of their position in depth. Thus a significant level is formed around the neutral pH-interval (at ± 7.5,'pH), then in two directions from this at around 8 pH and in the level of 6 pH. In an interval more acidic than that at 5. 5 pH significant accumulation can be found. Section No.

38 is a good proof of the fact that this element enrichment is governed not by depth but by chemical reaction. In this section the enrichment is the highest at level 3 (between 40 and 60 cm) at 5.7 pH. Thus enrichment in the first level corresponds to the level of enrichment is pH 6 interval. This shows the analogous origin of surface enrichments in the different samples. Enrichment levels are the results of the following: Section No. 38: pH = 5,5, section No. 37: pH = 6, section No. 36j, 30, 3L* pH = ± 7.5, section No. 32 and No. 33: pH = 6, No. 34: pH = 5.5, as in the first one. From the above it directly follows why no good correlation results were obtained horizontally when the relations of levels A, B, C were being examined (Chapter II. 3. 6.). It is to be seen that identical depths from the surface mark geochemically very different levels. This is the reason why there was no correlation between the different elements or between the elements and pH. Correlations calculated according to depth indicated that there is close connection between soluble element content and organic material content only in case of Zn (Chapter II. 3. 3.). At the same time Zn was the only element showing no close correlation with pH (Chapter H. 3. 2.). This can be explained by the above model. Zn appears bound to organic material, so it is contained in the greatest quantity by the upper soil level. At the same time we know that this soil level means different pH-values in different samples. While the rest of the elements follow the pH, to a certain extent independently of depth Zn follows mainly the organic material. Those correlations which in certain cases were obtained for Pb and Mn are the results of accidental coincidence. In Chapter II. 3. 1. some correlational relationship has been established concerning the changes of the different element pairs. This demonstrated that actually it is Zn that shows divergence, Mn, Pb, Cu on the whole changed according to identical rules. This likeness to regularity can also be explained by the above facts. Zn follows the organic material, its soluble quantity is enriched not according to pH, but the other three elements change first and foremost with pH. On the basis of our model it is possible to explain the correlations between element content and carbonate content. Given different sections of identical elements in some cases the correlation is good, in others there is no correlation. Zn never showed connection with the change of carbonate content. The former explanation applies to this, too. The concentration of Zn changes in connection with the organic material while the carbonate content depends on pH. This statement, however, does not explain why the quantity of the other trace elements examined (Mn, Cu, Pb) shows occassional good correlation with the carbonate content and why there is no correlation in other cases. This phenomenon can be explained by the fact that - as already seen - the above elements have more than one enrichment level, out of which two are in the acidic interval. Here carbonate is absent. When the carbonate content and the enrichment levels are jointly present, there is a correlation, but no correlation can be found where the section enters the acidic interval. Thus the connection between carbonate content and Mn, Cu, Pb is realized with pH, i.e. it is a secondary phenomenon. The dependence of the quantity of soluble lead on different parameters has previously been given since our findings related also to this. As lead has harmful biological effect it is worthwhile demonstrating it on its own. The separation of natural lead and pollution lead presents the greatest difficulty. If, however, the general element enrichment levels are known it can be detected where lead concentration is the result of different components and where lead exists in its natural form. Fig. 12 demonstrates that the concentration of lead changes as follows: At 5 m from the road it is 10 ppm, at 20 m it is 6.5 ppm, and at 35 m it is 9 ppm. This shows that there is no linear proportion between the decrease in the quantity of lead and the increase of distance. This shows that there is no linear proportion between the decrease in the quantity of lead and the increase of distance. This phenomenon has two reasons. On one hand 9 ppm lead content of section No.

38 at a distance of 35 m is within a high enrichment area while the 6.5 ppm of section No. 37 nearer the road is within a low enrichment zone. This explains