Spatio-temporal variations of selected pesticide residues in the Kurose River in Higashi-Hiroshima city, Japan

ABSTRACT

This study investigated spatio-temporal variations of selected pesticide residues in the Kurose River in Higashi-Hiroshima city (Hiroshima Prefecture), Japan. Water samples were collected from the river at seven sites every month for 1 year (March 2016 to February 2017). Pesticide residues were extracted from the samples by a solid phase extraction using Sep Pack C₁₈ cartridges. Once extracted, the samples were analyzed for cyanazine, simetryn, fenarimol, isoprothiolane, and diazinon using a reversed-phase high-performance liquid chromatography ultraviolet visible (HPLC-UV Vis) system. The limits of detection were 3.60, 4.10, 2.80, 6.50, and 7.30 ng L^-1 for cyanazine, simetryn, fenarimol, isoprothiolane, and diazinon, respectively. Good recovery rates (88%–102%), and mean percent relative standard deviation range (1.00%–5.70%) (n = 6) were obtained with a spiking at 0.20 µg L^-1. The maximum concentrations of 282, 391, 60, 1086, and 1194 ng L^-1 were obtained for cyanazine, simetryn, isoprothiolane, fenarimol, and diazinon, respectively. Cyanazine was the most frequently detected pesticide (64% of the samples, n = 84), followed by simetryn (58%), and then diazinon (57%). The highest and lowest pesticide concentrations were measured during the periods May–June, and January–February, respectively. Principal component analysis revealed three principal components in which the pesticides were linked to dissolved organic matter and total suspended solids. The major water quality parameters (electrical conductivity, pH, Na⁺, K⁺, Mg²⁺, Ca²⁺, NH₄⁺, NO₃⁻, Cl⁻, SO₄²⁻, NO₂⁻, and temperature) showed no clear trends for these pesticides. The presence of simetryn and isoprothiolane was largely attributed to rice paddy farms, whereas diazinon was associated mostly with vegetable farms and orchards. The diazinon and isoprothiolane patterns were consistent with their use of controlling insects and fungi in the prefecture. The maximum diazinon concentration detected was higher than the human safe level specified by the European Union (100 ng L^-1) in Council Directive 98/83/EC. This is of concern because of the bioconcentration potential of these residues in fish and other marine animals consumed by humans.

KEYWORDS:

• Liquid chromatography
• pesticide residue
• Kurose river
• seasonal variation
• water contamination
• cyanazine
• simetryn
• fenarimol
• isoprothiolane
• diazinon

Acknowledgments

The authors acknowledge Japan Society for the Promotion of Science (JSPS) (KAKENHI grant number 16KT0149) for sponsoring the work. The authors are also grateful to all members of our laboratory for their support during sample collection. Sincere thanks to Dr. W. Jadoon (Hiroshima University) and Dr. C. Kaonga (University of Malawi) for their valuable technical support. The authors recognize Stephen Crawford for his support in editing the manuscript, and Gabrielle David (Ph.D.), from Edanz Group (www.edanzediting.com/ac) for English editing of a final draft of this manuscript. Finally, the authors are grateful to anonymous reviewers whose comments helped greatly to improve the final version of the manuscript.