Uncovering seasonal patterns of 56 pesticides in surface coastal waters of the Ria Formosa lagoon (Portugal), using a GC-MS method

ABSTRACT

This study describes the simultaneous quantification of 56 pesticides in surface coastal water, supported by the development and validation of a gas chromatography (GC)–ion trap (IT) mass spectrometry (MS) method. Samples (500 mL) were pre-concentrated 2500 times by solid phase extraction (OASISTMHLB). The compounds were identified and quantified, within 35 minutes, by GC tandem mass spectrometry (GC-MS/MS) and GC-MS, respectively. The methodology proved to be highly specific for all target pesticides, with an average linearity of 0.99. Detection limits and recovery rates ranged from 0.4 to 1.3 ng L⁻¹ and 71% to 120%, respectively. The performance of the method was checked using water samples collected from nine sampling sites along the Ria Formosa Lagoon Natural Park (south of Portugal, n = 54) in each season (2010). The total annual concentrations of all pesticides in each category (fungicides, herbicides and insecticides) were 1.4, 0.6 and 9.0 µg L⁻¹, respectively. Moreover, 89% of the pesticides tested for were detected, 84% could be quantified and 25% had concentrations above the European recommended levels (2013/39/EU). The highest total loads of pesticides were found in the spring, which is in agreement with their seasonal application. Physicochemical parameters such as, nitrites, nitrates, ammonia and phosphates, also indicate poor water quality, supporting the fact that the Ria Formosa lagoon actually needs an effective monitoring programme for effective preservation of its natural reserve status.

KEYWORDS:

• Environmental monitoring
• GC-MS/MS
• pesticides
• SPE
• surface waters

Acknowledgements

Acknowledgements are due to Eng. Bartolomeu Pereira (Unicam Sistemas Analíticos, Lda) by his technical advices.

Additional information

Funding

This study was partially supported by the European Regional Development Fund (ERDF), through the Competitiveness and Trade Expansion Program (COMPETE) and by national funds provided by the Foundation for Science and Technology (FCT), with the grant [SFRH/BD/79305/2011] and the projects PTDC/MAR/70436/2006 [FCOMP-01-0124.FEDER-7382] and PEst-C/MAR/LA0015/2013.