The effect of technological oil spill in soil within electrical generation substations, analysed by ecological regime in the context of relief properties

Technological oil spills within electrical substations are the source of considerable environmental contamination. The aim
of this study is to evaluate the relation between phytoindication assessments of ecological factors and geomorphological
covariates and investigate the effect of the technological oil spill on ecological regimes within electrical substations. During the
fieldwork 175 geobotanical releves were analysed in the years 2016–2017 within Dnipropetrovsk region (Ukraine). Within
each electrical substation the geobotanical prospecting was conducted both in plots with undisturbed vegetation cover (control,
the plot size 3 × 6 m) and in plots with technological oil spill (pollution, plot size 3 × 3 m). Phytoindication assessment of the
following ecological factors was made: soil water regime, soil aeration, soil acidity, total salt regime, carbonate content in the
soil, nitrogen content in the soil, radiation balance, aridity or humidity, continental climate, cryo-climate, light regime.
HydroSHEDS data were taken for the basis for creating a digital elevation model with resolution of the data layer 15
arcseconds. The phytoindication assessments of the ecological regimes are characterized by correlation of geomorphological
properties. The soil humidity is characterized by statistically significant negative correlation with the topographic position index
and positive correlation with the vector ruggedness measure. The variability of damping correlates with four geomorphological
predictors. This environmental regime has positive correlation with digital elevation model and diffuse insolation and negative
correlation with topographic wetness index and direct insolation. The soil acidity of the edaphotope within Dnipropetrovsk
region correlates with statistical signiicance with the vector ruggedness measure. The soil humidity of the edaphotope is
associated with variation of the topographic wetness index, direct insolation, diffuse insolation and entropy of terrain diversity.
The highest carbonate content in the soil correlates with higher risks of erosion, which is characterized by loss of soil and
vertical distance to channel network. The nitrogen content in the soil is very sensitive to geomorphological features of the area.
This results in the correlation of this indicator with six geomorphological predictors. Obviously, the most favourable supply of
the nitrogen content in the soil is formed on upland areas. This allows positive correlation of the phytoindication assessment of
the nitrogen content in the soil and the height relief. The use of relief variable as the covariate revealed the nature of the impact
of soil contamination on ecological factors. Technological oil pollution leads to deterioration of water regime, reducing the
availability of plant available forms of nitrogen and deterioration of soil aeration. There are also changes in microclimatic
properties. There are more extreme thermal regimes and greater level of illumination. A key task for further research is to study
the influence of relief features on the degree of negative transformation of soil due to technological oil pollution.