Abstract: | Particular hazards to the environment are caused by hydrocarbon
products introduced as a result of industrial and
military activity. It leads to contamination of shallow
sub-surface layers, as well as groundwater.
The presence of hydrocarbon pollutants in the geological
environment causes changes in its many physical properties
(e.g. electrical conductivity and resistivity). This results
in the anomalies observed. However, hydrocarbons,
despite being excellent insulators, can generate both anomalies
of low conductivity (i.e high resistivity), high conductivity,
or do not cause any changes in values of the parameter
measured. Changes in its values in short time
intervals can be irregular and fall into the measurement error
range. Simultaneously, these values can gradually decrease
over the time, which is associated with the loss of
contamination weight and gradual remediation of the environment
due to natural biological processes.
The monograph presents the possibility of applying
geoelectrical methods — conductometric in frequency domain
and resistivity imaging — to identify petroleum contaminations
and to monitor the process of their bioremediation
by Yarrowia lipolytica yeast. The applied research
methodology allowed also to trace models of contamination
evolution. The results of field measurements were interpreted
by the inversion method of resistivity imaging,
1D with the conductometric one, and 2D taking the topography
into account. In the final interpretation, the laboratory
tests (determination of hydrocarbons and metals contents,
determination of mineral composition, indication of
electrical resistivity as a function of humidity, indication of
electrical conductivity as a function of the concentration of
citric acid) are included.
The study was carried out in two areas of former military
fuel bases JAR in the Borne Sulinowo and Szprotawa
sites, differing in geological structure and vegetation. Both
centers are sandy, the first one shows high resistivity whereas
the second one — low resistivity.
The complex field and laboratory studies were performed
under conditions of high-resistivity environment.
First of all, the possibility to use both methods for the
identification of perennial petroleum contamination was recognizedwith an assessment of their quality by the
correlation with historical data and results of laboratory research.
Next, the methods were applied to identify the
fresh contamination and to control their dispersion in geological
complex, together with laboratory tests and the atmogeochemical
method.
In the following research, the process of supported bioremediation
was monitored at two contamination sites: the
historical and fresh controlled ones. The influence of atmospheric
conditions on values of the parameters measured
was estimated, as well as their changes in time. Using
laboratory and atmogeochemical research, bioremediation
rate has been assessed, whereas basing on resistivity
cross-sections, the percentage loss of the contaminants has
been calculated.
Under conditions of the low-resistivity environment
such as the area of former JAR fuel storage in Szprotawa,
the research was carried out to the limited extend, along
only one profile running from the contaminated site to the
clean one. It enabled to trace evolution of contamination
from:
clean environment contamination high-resitivity
model low-resitivity clean environment
Application of geoelectrical methods enabled to investigate
qualitatively petroleum contamination sites. It also
enabled to estimate their spatial distribution, whereas parameters
measured in situ correlated well with the results of
laboratory tests.
It has been shown that, depend on the occurrence of organic
acids or their absence in the geological environment,
the contaminated sites can generate anomalies of low conductivity
or high conductivity. The presence of organic
acids depends on the geological structure and hydrogeological
and environmental conditions. In the high-resistivity
environment natural bioremediation is hindered and occurs
slowly. Thus production of organic acids is limited. In the
low-resistivity environment microorganisms populations
are various and numerous, thus natural bioremediation
occurs rapidly. As a result, a low-resistivity model of con-tamination is generated over the contaminated site just
after its contamination.
It has been shown that immediately after contamination
of the sandy environment, there is a distinctive increase inelectrical resistivity, which is related to high resistivity of
hydrocarbons. Moreover, the progression of bioremediation
with Yarrowia lipolytica yeast can be effectively and
continuously monitored by modern geoelectrical methods. |