5 Conclusions
This study concluded that Mg-rich, alkaline dust causes long-lasting
soil degradation, which is manifested mainly near both magnesite
processing factories, and the excess of available Mg along the direction
of the prevailing spreading of alkaline emissions.
Dominant influence of excessive content of total and available magnesium
compounds on soil chemical properties was confirmed by a significant
increase of soil pH, carbonate content, and conductivity, while total
and available Ca did not affect the mentioned characteristics. On the
contrary, Ca was positively related to available Cu and Ni.
Negative relationship between the labile fraction of soil organic matter
and available Mg suggests that in more affected localities weaker
formation and stock of newly formed organic matter prevails, and
consequently lower enzymatic activity. Thus, in addition to effective,
alkaline emissions capturing filters, an important measure supporting
the microbial activity of affected soil is enrichment by organic matter.
Research of soil enzymatic activities are essential, as these processes
reflect the degree and size of contamination of the natural environment
or any revisions by humans. It is important that the high enzymatic
activity in soil was observed during a period of two to three
consecutive years. This may indicate that the soil condition has become
more stable.
At present, when the entry of Mg-rich, alkaline dust into the soil has
been significantly reduced (by 99.75% compared to 1970), the
application of measures can bring more lasting positive results than in
the past, when the high deposition of Mg dust did not allow successful
land reclamation.
Nevertheless, classical methods are still the most effective for
reclaiming the most affected areas. It is suggested that the impermeable
Mg-rich crust is mechanically removed, milled, and use as a magnesium
fertilizer. Subsequently, the soil where the available Mg exceeded 2,000
mg kg-1 has to be treated chemically, by incorporating
gypsum, phosphogypsum, citric-gypsum, sulphite leaches, anionic
polyacrylamide and calcium dihydrogen phosphate as well as high doses of
farmyard manure.
Recent methods are applicable to less affected areas. These involve the
growing of Mg hyper-accumulating plants that, after composting, can be
used as an organic fertilizer enriched with Mg, or growing plants that
can be used for energy purposes. In the studied area, among naturally
occurring vegetation, only Phragmites australis is characterised
by high biomass production.
Sampling sites, where the available Mg decreased under the critical
level of 1,000 mg kg-1, can be reused for agricultural
production. Over the whole affected area, care must be taken to maintain
a favourable state of natural vegetation. Consistent application of
measures will enable a gradual return of the soil and landscape to a
more productive state.