Chemometric Analysis of Selected Organic Contaminants in Surface Water of Langat River Basin

Abstract

Chemometric techniques namely hierarchical agglomerative cluster analysis (HACA), discriminant analysis (DA), principal component analysis (PCA) and factor analysis (FA) were applied to the distribution of selected organic contaminants (polycyclic aromatic hydrocarbons (PAHs), sterols, pesticides (chlorpyrifos), and phenol) to assess the potential of using these organic contaminants as chemical markers in Langat River Basin. Water samples were collected from February 2012 to January 2013 on a monthly basis for nine monitoring sites along Langat River Basin. HACA was able to classify the sampling sites into three clusters which can be correlated to the level of contamination (low, moderate and high contamination sites). DA was used to discriminate the sources of contamination using the selected organic contaminants and relate to the existing DOE local activities groupings. Forward and backward stepwise DA was able to discriminate two and five organic contaminants variables, respectively, from the original 13 selected variables. The five significant variables identified using backward stepwise DA were fluorene, pyrene, stigmastanol, stigmasterol and phenol. PCA and FA (varimax functionality) were used to identify the possible sources of each organic contaminant based on the inventory of local activities. Five principal components were obtained with 66.5% of the total variation. Result from FA indicated that PAHs (pyrene, fluorene, acenaphthene, benzo[a]anthracene) originated from industrial activity and socio-economic activities; while sterols (coprostanol, stigmastanol and stigmasterol) were associated to domestic sewage and local socio-economic activities. The occurrence of chlorpyrifos was correlated to agricultural activities, urban and domestic discharges. This study showed that the application of chemometrics on the distribution of selected organic contaminants was able to trace the sources of contamination in surface water. Keywords: chemometrics, organic contaminants, chemical markers, Langat River AbstrakTeknik kemometriks iaitu Analisis Kelompok Agglomeratif Berhieraki (HACA), Analisis Diskriminan (DA), Analisis Komponen Utama (PCA) dan Analisis Faktor (FA) telah diaplikasi ke atas taburan bahan pencemar organik terpilih (aromatik hidrokarbon polisiklik (PAH), sterol, racun perosak (klorpirifos), dan fenol) untuk menilai potensi penggunaan bahan pencemar organik ini sebagai bahan pengesan di Lembangan Sungai Langat. Sampel air diambil dari bulan Februari 2012 hingga Januari 2013 pada setiap bulan di sembilan stesen pemantauan sepanjang Lembangan Sungai Langat. HACA dapat mengkelaskan kawasan persampelan kepada tiga kelompok yang boleh dikaitkan dengan tahap pencemaran (pencemaran rendah, pencemaran sederhana dan pencemaran tinggi). DA telah digunakan untuk membezakan sumber -sumber pencemaran dengan menggunakan bahan -bahan organik terpilih dan mengaitkannya dengan aktiviti -aktiviti setempat berdasarkan DOE. Analisis Diskriminan Langkah Hadapan dan Belakang masing -masing dapat mendiskriminasika...

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“…This method is expected to facilitate the classification process and identify a set of observations that show significant homogeneity features (P < 0.05). Then, Discriminant Analysis (DA) used as a calibration and validation process for the HACA classification [ [77] , [78] , [79] , [80] , [81] ]. Principal Component Analysis (PCA) is also used to reduce the dimensionality of data sets by explaining the correlation between larger and smaller data sets [ 45 , [80] , [81] , [82] ].…”