thus disturbing the overview of the process efficiency. Chemical assays may provide
valuable information about changes in contaminant concentration and are well
known and widely used. However, the decrease in the contaminant content is not
always related to decrease in soil ecotoxicity (Shen et al. 2016). The uncertainty of
chemical assays may be caused by several methodology steps like, e.g., analytical
extraction of TPH from soil or detection limit of the device used for quantification.
As chemical assays are based on the quantification of target contaminants, the other
xenobiotics or toxic metabolites remain undetected. Also, chemical assay does not
provide information regarding synergistic effects, which may occur between contaminants, resulting in enhanced toxicity (Płaza et al. 2005). As highlighted by
several authors, chemical analysis does not provide full overview of the bioremediation performance, and does not include all of the factors responsible for occurrence
of ecotoxicity (Shen et al. 2016; Płaza et al. 2005).
5.4.2 Molecular Markers and Microbial Analysis
Monitoring changes in soil enzymatic activity also may provide useful information
about the progress of bioremediation. Common monitored enzymes are dehydrogenase, lipase, β-glucosidase, arylsulfatase, acid and alkaline phosphatases, ureases, Nbenzoyl-L-argininamid (BAA)-hydrolyzing protease and hydrolase (Namkoong
et al. 2002; Ceccanti et al. 2006; Labud et al. 2006; Tejada et al. 2008; GarcíaRuiz et al. 2009). However, the activity of a single enzyme may not be representative
in case of multi-contamination and results may differ according to environmental
conditions. The activity of enzymes in soil may be affected by many factors other
than the contaminant, like TOC, EC, TN, TP, or C:N ratio (Gao et al. 2013). Results
obtained from the analysis of soil quality markers should be analyzed carefully, with
attention to the fact that individual parameters should not be taken for granted as a
soil quality indicator. Thus, the activity increase of a single soil enzyme cannot be
associated with soil detoxification (Gao et al. 2013). Moreover, soil enzymatic
activity exhibits natural variability, which may render the interpretation of results
more difficult. Thus this method also requires frequent sampling. Instead of single
enzyme approach, the geometric mean of enzymes activities (GMea) is
recommended (García-Ruiz et al. 2009). Another solution is also utilization of
nonspecific technics measuring total hydrolytic activity in soil. An example may
be the method of fluorescein diacetate (FDA) hydrolysis (Lu et al. 2009).
Statistical data processing through principal component analysis (PCA) and
factorial analysis are also recommended for monitoring chemical and physical soil
parameters. In the study of Gao et al. (2013) a strong correlation between TPH and
total organic carbon was shown to be useful in monitoring. However, in case organic
matter applied to soil this correlation may be disturbed. In that case, the observed
decrease of total organic carbon may be connected to biodegradation of organic
matter, not contaminants.
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A. Gielnik et al.
valuable information about changes in contaminant concentration and are well
known and widely used. However, the decrease in the contaminant content is not
always related to decrease in soil ecotoxicity (Shen et al. 2016). The uncertainty of
chemical assays may be caused by several methodology steps like, e.g., analytical
extraction of TPH from soil or detection limit of the device used for quantification.
As chemical assays are based on the quantification of target contaminants, the other
xenobiotics or toxic metabolites remain undetected. Also, chemical assay does not
provide information regarding synergistic effects, which may occur between contaminants, resulting in enhanced toxicity (Płaza et al. 2005). As highlighted by
several authors, chemical analysis does not provide full overview of the bioremediation performance, and does not include all of the factors responsible for occurrence
of ecotoxicity (Shen et al. 2016; Płaza et al. 2005).
5.4.2 Molecular Markers and Microbial Analysis
Monitoring changes in soil enzymatic activity also may provide useful information
about the progress of bioremediation. Common monitored enzymes are dehydrogenase, lipase, β-glucosidase, arylsulfatase, acid and alkaline phosphatases, ureases, Nbenzoyl-L-argininamid (BAA)-hydrolyzing protease and hydrolase (Namkoong
et al. 2002; Ceccanti et al. 2006; Labud et al. 2006; Tejada et al. 2008; GarcíaRuiz et al. 2009). However, the activity of a single enzyme may not be representative
in case of multi-contamination and results may differ according to environmental
conditions. The activity of enzymes in soil may be affected by many factors other
than the contaminant, like TOC, EC, TN, TP, or C:N ratio (Gao et al. 2013). Results
obtained from the analysis of soil quality markers should be analyzed carefully, with
attention to the fact that individual parameters should not be taken for granted as a
soil quality indicator. Thus, the activity increase of a single soil enzyme cannot be
associated with soil detoxification (Gao et al. 2013). Moreover, soil enzymatic
activity exhibits natural variability, which may render the interpretation of results
more difficult. Thus this method also requires frequent sampling. Instead of single
enzyme approach, the geometric mean of enzymes activities (GMea) is
recommended (García-Ruiz et al. 2009). Another solution is also utilization of
nonspecific technics measuring total hydrolytic activity in soil. An example may
be the method of fluorescein diacetate (FDA) hydrolysis (Lu et al. 2009).
Statistical data processing through principal component analysis (PCA) and
factorial analysis are also recommended for monitoring chemical and physical soil
parameters. In the study of Gao et al. (2013) a strong correlation between TPH and
total organic carbon was shown to be useful in monitoring. However, in case organic
matter applied to soil this correlation may be disturbed. In that case, the observed
decrease of total organic carbon may be connected to biodegradation of organic
matter, not contaminants.
268
A. Gielnik et al.