Identification of Major Interfering Substances for Heavy Metal Determination in Northern Sea Areas of Sri Lanka

Abstract

This study investigated the physicochemical characteristics of seawater from five locations along the northern Sri Lankan coast, encompassing areas with varying degrees of anthropogenic activity. The analysis revealed significant variations in several parameters, potentially influenced by human influences. The results reveal significant variations in several parameters. For instance, turbidity levels varied from 1.88 NTU in Thalaiyadi to 13.3 NTU in Pannai, with Pannai, Myliddy, and Kakkaithivu exceeding the recommended limit of 5 NTU. Total suspended solids (TSS) ranged from 3 mg/L in Thalaiyadi to 83 mg/L in Pannai, surpassing the recommended limit of 30 mg/L. Electrical conductivity (EC) ranged from 45,700 µS/cm in Nainathivu to 49,500 µS/cm in Pannai, exceeding the typical seawater range. Nitrate levels ranged from 10.4 mg/L in Thalaiyadi to 19.1 mg/L in Myliddy. Major cations such as calcium (361 mg/L to 417 mg/L), magnesium (1,222 mg/L to 1,327 mg/L), and sodium (10,140 mg/L to 10,530 mg/L) also showed significant differences across locations. These findings highlight the need for continuous monitoring and effective management strategies to mitigate the negative impacts of anthropogenic activities on these coastal ecosystems. Furthermore, the complex seawater matrix presents challenges for heavy metal determination using Graphite Furnace Atomic Absorption Spectroscopy (GFAAS) due to spectral interferences from major cations, non-specific matrix effects, and interferences from organic matter, turbidity, and suspended solids. Careful consideration of these factors through background correction techniques, matrix modifiers, sample pre-treatment, and optimization of analysis parameters is crucial for accurate heavy metal determination in these environments. This study contributes to a better understanding of the environmental conditions and emphasizes the need for further research on heavy metal contamination and the development of robust analytical methods tailored to address the challenges posed by the complex seawater matrix in northern Sri Lanka.