There are two major types of risk assessments as noted by Jensen et al. (2006). The first is undertaken prior to the release of a new substance, such as pesticides, to determine if it is safe to use in the natural environment. The second type of ecological risk assessment (ERA) is a description of the changes, which are observed in populations or ecosystems at sites that have become contaminated, and can therefore also be referred to as an impact assessment.
This assessment can conduct using empirical equations or and other developed mechanisms (Jensen et al., 2006). The ERA is performed to evaluate the likelihood of adverse ecological effects occurring as a result of exposure to physical or chemical stressors. These stressors are defined as any biological, physical, or chemical factor that causes adverse responses in the environment (Mustafa et al., 2015).
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At EPA, ecological risk assessments are used to support many types of actions, including:
regulation of hazardous waste sites, industrial chemicals, and pesticides; or the management of watersheds or other ecosystems affected by multiple chemical, physical, or biological stressors. Risk assessment provides a systematic procedure for predicting potential risks to human health or the environment. The aim of a chemical risk assessment is to investigate if a chemical is being used or can be used as intended without causing detrimental effects to human health or the environment.
In several countries, the problems of contamination with metal elements are increasing;
therefore the application of principal component analysis and risk index method become very useful tool for assessing the environmental impact of ecological risk of metal elements in environment (Mustafa et al., 2015). Figure 2.12 displays the procedure of environmental risk assessment and thus components of human and ecological risk assessment. From the ecological point of view the contamination indexes provides useful information to public, decision makers and managers in processing and analyzing the environmental data.
The researchers report that multivariate statistical techniques are the right tool for viewing and analyzing some of complex data (Wei et al., 2011). In addition, the potential ecological risk index (PERI) is a method that is used for the risk assessment of metal elements. This method was first suggested by Håkanson in 1980 with the aim of indicating the environmental agents and prioritizing contamination studies in hazard contamination sites, lakes and coastal systems (Håkanson, 1980). Although potential risk factor was originally used by Håkanson for the purpose of controlling water contamination, in recent years it was very successfully used for the quality of sediments and soil in the environment with metal elements using various indices.
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Figure 2.12: Components of human health risk and ecological risk (Source: UNEP, 1996).
In addition, assessment of metal contamination by indices including potential contamination (Cp), contamination factor (CF), contamination load index (CLI), modified contamination degree (mCD), numerical integrated contamination factor (NICF), enrichment factor (EF), geo-accumulation index (Igeo), potential ecological risk factor (ER) and potential ecological risk index (PERI) are common for soil and stream sediments or surface sediment along different water bodies such as river, lake, sea (Kalender and Uçar, 2013). In the same way, analysis method being used for possible metal contaminated soil such as landfill soil, soil of industrial area, agricultural soil etc. (Mustafa et al., 2015; Wang et al., 2013).
Pearson’s correlation analysis and principal component analysis (PCA) are one of unsupervised methods that estimate the correlation structure of the variables by finding hypothetical new variables (principal components-PC) that account the variance in a multidimensional data set (Wei et al., 2011). In addition, geostatistical technique like ordinary kriging (OK) is a common method to distribute metal contamination spatially.
Environmental Risk Assessments RESOURCES air, water, soil, biota
Wildlife, natural vegetation, agriculture, forests, wetlands, streams/
lakes Occupational health,
Environmental health, domestic livelihood,
livability cultural heritage
Problem Identification
Human Health Risk Assessment
Ecological Risk Assessment Hazard Identification
Exposure - Response Risk characterization
Problem formulation Analysis Risk characterization
35 2.18 Pearson’s Correlation Analysis
The technique of Pearson’s correlation is a parametric measurement developed by Karl Pearson from a related idea introduced by Francis Galton in 1880s (Galton, 1886; Pearson, 1895). The Pearson’s correlation produces a sample correlation coefficient, r, which measures the strength and direction of linear relationships between pairs of continuous variables. Such affiliation is probably going to prompt thinking about causal association between the factors (Srinivasa and Pradip, 2010). The correlation analysis is a preliminary descriptive technique to estimate the degree of association among the variables involved.
The values of correlation coefficients will help in selecting proper treatment to minimize groundwater pollution from the contaminated soil. In case of metal element contamination in soil, several studies were performed to find the association between metal elements and the similarity of their contamination sources. Zou et al. (2015) studied on sources of metal elements in farmland soils of beijing suburbs, China based on pearson’s correlation. It was found that some metal eelments such as Cr was moderately correlated with Cd and Zn, whereas, Hg was only correlated with As and not with the other elements as the pair. In this study, the principal of pearson’s correlation was performed using XLSTAT to examine the association of metal elements in soil of the waste disposal site.