Application of chemometrics to analysis of soil pollutants

Abstract

This overview focuses on the application of chemometrics techniques to the investigation of soils contaminated by polycyclic aromatic hydrocarbons (PAHs) and metals, because these two important and very diverse groups of pollutants are ubiquitous in soils. We highlight the salient features of studies carried out in the microenvironments and recreational environments of humans in the context of the multivariate statistical techniques available across the boundaries of disciplines used in soil studies. We pay particular attention to techniques employed in the geosciences that may be effectively utilized for environmental soil studies. We also discuss classical multivariate approaches that may be used in isolation or as complementary methods to these. Chemometrics techniques widely applied in atmospheric studies for identifying sources of pollutants or for determining the importance of contributions of contaminant sources to a particular site have seen little use in soil studies, but they may be employed effectively in such investigations. Suitable programs are also available for suggesting measures of mitigation in cases of soil contamination, and we also consider these. Specific techniques reviewed include: • pattern-recognition techniques [e.g., Principal Components Analysis (PCA), Fuzzy Clustering (FC) and Cluster Analysis (CA); • geostatistical tools [e.g., variograms, Geographical Information Systems (GISs), contour mapping and kriging]; and, • source-identification and contribution-estimation methods [e.g., Positive Matrix Factorization (PMF), and PCA on Absolute Principal Component Scores (PCA/APCS)]. Mitigating measures to limit or to eliminate pollutant sources may be suggested through the use of ranking analysis and multi-criteria decision-making methods (MCDMs), mainly represented in this review by studies employing the Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE) and its associated graphic output, Geometrical Analysis for Interactive Aid (GAIA).