A SYSTEM-APPROACH PRESENTATION OF PROCESSES IN THE SAMPLE AREA

methodological research scientifically founding the protection of natural values is reported on.

A SYSTEM-APPROACH PRESENTATION OF PROCESSES IN THE SAMPLE AREA

ronment is distinct from the natural subsystem comprising rocks, soils, relief, surface waters and farming crops. The atmosphere and the climatic effects as not decisive parts of the visible structure of the landscape are shown outside the limits of the system. Their influence is indicated by including some major impacts.

The sample area is a typical agricultural area in rural environment, where large-scale arable farming prevails and, in addition, vineyards occupy considerable areas and vegetable gardens occur over a small percentage of the land. In order to achieve higher yields irrigation (1) is practised regularly. Nutrient recharge is ensured through the application of manure (2), fertilisers (3) and sewage sludge (4). Against plant dis­

eases various pesticides (5) are used. It can be seen that the amounts of various material inputs of the system are controlled by man. It is an essential point as manure, fertilisers, sewage sludge and pesticides contain compounds harmful to human health. Nitrogen fertilizers, for instance, may increase the nitrate contents of soils and of groundwater. In phosphate fertilizers cadmium concentration is often high and sewage sludge may also contain heavy metals in considerable amounts. Therefore, the appropriate control of input is of primary importance for in its absence the pollution of the environment may reach critical levels.

The amounts of pollutants arriving in the area through atmospheric deposition (9) cannot be influenced by man on the site of immission, the rate of which primarily depends on the distance from emission source, the amount of pollutants in air and at­

mospheric conditions. The sample area lies quite a distance away from major industrial areas, and thus, no sizeable deposition has to be taken into account.

104 SOCIAL SUBSYSTEM NATURAL SUBSYSTEM

irrigation

organic manures“

a rtificial__

fertilizers sewage sludgespesticides

-1,2/a, 3/a, 4/a, 5/a, '6/a, 7/a, 8/a, 9/a

precipitation

atmospheric deposition

waste deposition crop

---► matter and energy flow --- ► effect

The population in the villages of the sample area uses the water o f groundwater wells. The model shows how diverse sources supply pollutants into the groundwater, and thus, also into drinking water. Nitrate is a major danger. Therefore, the nitrate content of groundwater have been monitored for several years. From hundreds of measurements it has been established that in a considerable percentage of wells nitrate content exceeds the health limit o f 40 mg/l. Values between 100-200 mg/1 were frequently found and a nitrate content above 700 mg/1 has also been measured. The investigations revealed that a main source of nitrate content in groundwater was nitrogen fertilizers spread from the neighbouring agricultural area. Topographic conditions allow the redeposition of part of the fertilizer amount in the lower lying terrain through sheet wash during major rainfall events. Lysimeter observations and auger holes revealed that it takes only some years for the nitrates of fertilizers to be washed into the groundwater, which also flows towards villages situated in valleys. In addition, pollution sources within the built-up areas o f settlements (manure heaps, privy pits, sewage septic tanks) also contributed to high nitrate contents.

In addition to the considerable nitrate levels, using the GC/MC method, various chemical residuals (DDT, DDE, atrazine), decomposition products of the mentioned manures and pesticides (2/a, 3/a, 4/a, 5/a), fuels like oil derivates used for agricultural machines and road vehicles (6/a) as well as for heating homes (8/a) have also been found in groundwater, (/a marks chemically transformed compounds of the material or group of materials indicated by Figure 3) A further source of pollution can be domestic waste (7/a) from settlements as its safe disposal is not yet solved.

The model clearly shows that polluted groundwater is not only a direct risk for human health, but since plant roots are able to take up dissolved pollutants from the soil, indirectly, through plants, may also cause problems.

Various toxic heavy metals may present an additional danger. For this reason, the horizontal and vertical distribution of these metals in the soils of the sample area has been studied in detail with atomic absorption spectrometer. It was found that the role o f morphology is decisive in the distribution of certain metals. In the case of metals accu­

mulating in topsoil, for instance, maximum values of concentration are often measured on the valley floor. This might be attributed to erosion induced by sheet wash, which mainly affects the uppermost soil layer. From the interpretation of several thousands of measurements, it was found that the heavy metal content o f soils in the sample area is — disregarding some exceptions - below the health limit.

The factors influencing the behaviour of heavy metals, controlling the migra­

tion of these elements with in the soil-plant system, have been analysed in detail. It is claimed that in the soils of the sample area among the heavy metals investigated, lead, cobalt, chromium, nickel, manganese and vanadium are present in forms not easily available for the plants, while - compared to the metal content of soils - much higher amounts of zinc and copper are taken up by plants.

Another important issue is the distribution o f heavy metals within plants. It is not at all indifferent in which organ of the plant they accumulate. In the three most widely grown crops of the area, corn (maize), wheat and sunflower, heavy metal distri­

butions have been investigated and the highest metal contents are found in roots. From

the viewpoint of toxicity it is favourable, since the roots of these plants are not suitable for human consumption or animal feeding. On some occasions, however, primarily in the case of sunflower, leaves contained the highest amounts of metals. It can be con­

ceived that atmospheric deposition (9) is most efficient at this plant of the largest leaf area of the three most frequent crops and the epidermis is rich in plant hair, which fur­

ther increases specific leaf area. It is remarkable that large amounts o f copper and par­

ticularly zinc accumulate in the fruits of the crops studied. Consequently, if crops are grown on soils contaminated with the two metals mentioned, the danger is high.

The model shows that various chemical residuals, pollutants are carried by sheet washand the resulting soil erosion into surface waters. In the sample area Hór stream collects waters and transports them (together with pollutants) out of the area.

The sample area lies in the contact zone of sedimentary and volcanic rocks, which control soil formation mechanisms and determine the mineral components of soils. The investigations suggest that the territorial variation of heavy metal content in soils is partly due to differences in parent rocks.

The system model is naturally unsuitable to include all minor details but the routes o f matter and energy flows most important for the operation of the system and the major impacts are demonstrated. It is clearly visible that the dangers which emerge during functioning are almost exclusively the consequences o f human activities and it is also unambiguously stated that the key o f regulation is in the hand o f man.

RESEARCH FOR FOUNDING THE PROTECTION OF PHYSICAL