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

ABSTRACTThis 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.

摘要：本研究通过开发并验证一套气相色谱-离子阱质谱法（gas chromatography-ion trap mass spectrometry, GC-IT-MS），实现了近岸地表水中56种农药的同时定量测定。样品（500 mL）采用OASIS™ HLB小柱进行固相萃取（solid phase extraction），完成2500倍富集。目标化合物可在35分钟内分别通过气相色谱-串联质谱（GC tandem mass spectrometry, GC-MS/MS）完成定性鉴定、气相色谱-质谱（gas chromatography-mass spectrometry, GC-MS）完成定量分析。该方法对所有目标农药均具有极高特异性，线性相关系数平均值达0.99。方法的检出限（detection limits）与回收率（recovery rates）分别介于0.4~1.3 ng·L⁻¹与71%~120%之间。本研究于2010年各季度从葡萄牙南部里亚福尔摩沙泻湖自然公园（Ria Formosa Lagoon Natural Park）沿岸的9个采样点采集水样（共54份），以此验证该方法的性能。各品类农药（杀菌剂、除草剂与杀虫剂）的年总浓度分别为1.4、0.6与9.0 μg·L⁻¹。此外，本次检测的农药中有89%被检出，84%可实现定量分析，另有25%的农药浓度超出欧盟2013/39/EU号指令规定的限值。农药总负荷最高值出现在春季，这与农药的季节性施用规律相符。亚硝酸盐、硝酸盐、氨与磷酸盐等理化参数也显示该水域水质不佳，佐证了里亚福尔摩沙泻湖确实需要建立有效的监测方案，以维护其作为自然保护区的地位。