|Lapworth, D J, Crane, E J, Stuart, M E, Talbot, J C, Besien, T, and Civil, W. 2018. Micro-organic contaminants in groundwater in England: summary results from the Environment Agency LC-MS and GC-MS screening data. British Geological Survey Internal Report, OR/18/052.|
This report describes the results from summarising Environment Agency groundwater monitoring data for trace organic compounds from two targeted scanning semi-quantitative methods. The Gas chromatography mass spectroscopy (GC-MS)[note 1] method has been regularly used for groundwater samples since 2001 and provides semi-quantitative data for neutral, hydrophobic compounds amenable to separation by gas chromatography. These include a wide range of industrial compounds, halogenated solvents and trihalomethanes (THMs), plasticisers and pesticides, with relatively few pharmaceuticals. The Ultra-High-Definition (UHD) Accurate-Mass Quadrupole Time-of-Flight (Q-TOF) liquid chromatography-mass spectrometry (LC-MS) method has been used from 2012 onwards for groundwater samples and complements the GC-MS method by providing data on polar, more hydrophilic compounds including many pesticides and pharmaceuticals, as well as perfluorinated compounds (PFCs). Some compounds, such as atrazine, are detected by both methods.
The aim of this project was to analyse Environment Agency GC-MS (2009–2017) and LC-MS (2016–2017) semi-quantitative (targeted) screening data for emerging contaminants in groundwater and to produce summary statistics, selected charts, maps and a summary report. When interpreting the results of this report additional caution is required because of the semi-quantitative nature of these screening methods and also because these screening methods are so sensitive unforeseen sample contamination can be an issue.
The results from the GC-MS method showed that out of the top 50 most frequently detected compounds 13 were industrial compounds, 8 were pesticides and their transformation products, 9 were pharmaceuticals, personal care products or lifestyle compounds (PPCL), 8 were polyaromatic hydrocarbons, 7 were halogenated solvents and 5 were plasticisers. Limits of quantification for this method are predominantly 0.01 μg/L with higher limits for four compounds, the industrial compound 2,4,7,9-Tetramethyl-5-decyne-4,7-diol (TMDD), the food additive Butylated hydroxytoluene (BHT), and the plasticisers benzenesulfonamide, N-butyl (BBSA) and Bis(2-ethylhexyl)phthalate DEHP.
The results were similar to those reported in 2016 but with some key differences:
- There were fewer overall detections due to the removal of non-GC-MS specific data from the analysis: this was most obvious for the halogenated solvents
- Some compounds were less prominent possibly due to analytical methodology improvements with the reduction in the umber of false positives. An example of this would be caffeine
- Some new compounds appeared in the top 50 most frequently detected compounds, e.g. butanedioic acid, and dimethyl ester (dimethyl succinate)
Ordering the results using maximum concentrations gives a very different set of compounds with the plasticiser BBSA having the highest maximum concentration.
For the LC-MS data 36 of the top 50 most frequently detected compounds were pesticides, with others being 8 PPCL and 6 industrial compounds. Ordering the results by maximum concentration indicates that 3 out of 5 of the highest concentrations were for the PPCLs clopidol, sucralose and pentobarbital.
The quantification limits for the LC-MS method which are at 0.001 μg/L are predominantly an order of magnitude lower than for the GC-MS, increasing for perfluorinated compounds and also for the PPCLs sucralose, sulphanilamide and sulfamethoxazole, and the pesticides boscalid, trietazine and mecoprop. The percentage of samples with positive detections is much higher, 5–65%, for the LC-MS data compared to typically 1–2% for the GC-MS.
The ranges of LODs for Environment Agency quantitative analytical suites are of a similar order of magnitude to the LC-MS method with higher limits for PAHs and difficult compounds, such as the pesticides chlormequat and glyphosate which can only be analysed with quantitative methods.
Both the target GC-MS and the LC-MS methods detect a much wider range of compounds than the Environment Agency standard suites (also using GC-MS and LC-MS) currently cover.
- Please see the glossary for expansions of acronyms