Next Generation Passive Sampling for Monitoring Organic Contaminants in Water

Anthropogenic organic contaminants such as pharmaceuticals, pesticides, and industrial products are found in rivers, lakes, and estuaries, and pose a risk to both the natural environment and the humans that use it. Hence organic chemicals are one of the key pollutants that must be monitored in our natural waters, as stipulated in the water framework directive. Organic contaminants cannot be monitored using sensors however, due to the low concentrations and current available sensing technologies, hence monitoring must be done by sampling and lab analysis. One to two litre samples are typically taken, transported to a laboratory, and then analysed using liquid chromatography mass spectrometry (LC/MS). The collection and transport of samples is manually intensive, logistically demanding, and hence expensive, time-consuming, and carbon-intensive. The number and frequency of measurements are consequently limited, giving an incomplete picture of the water quality; the variation of concentration over time is uncertain, and acute short-lived pollution events are unlikely to be captured.

Passive sampling is an alternative approach. Rather than taking a sample of the water, a sorbent device is left in the water for several weeks during which time it accumulates pollutants that are present. It is complementary to spot sampling and has several advantages: firstly it gives a time-averaged picture of the pollution levels and will record the short-lived pollution events that might be missed by spot sampling; secondly by accumulating over time very low concentration contaminants can be recorded - for spot sampling this would necessitate larger samples (with an accompanying logistical expense); finally the sorbent discs are small (5-10 cm in diameter) so transport is easier. Passive sampling also comes with some disadvantages, however. Firstly, it offers no time resolution. This means that while all pollution events are recorded we have no information on when these happened - temporal variation of a pollutant is an invaluable clue for determining pollution sources. Secondly, it is still manually intensive as passive samplers can only be left for a maximum of two to three weeks and need to be replaced after this time. Finally, the LC/MS lab analysis produces a large amount of raw spectral data that needs laborious specialised processing to deliver final results for end-users.

In this project we aim to address these issues and create a new generation of passive sampling. Specifically, we will create versatile samplers that can autonomously expose the sorbent sampling discs to either give much more detailed data for the same operational costs (time resolutions of days rather than weeks); or much longer deployments (months rather than weeks) and hence lower operational costs for the current temporal resolution. These benefits will make pollution sources easier to identify and make passive sampling lower cost and less carbon intensive. Allied with this we will develop software to automate the process of going from raw data to final visualised data, saving time and making data more easily accessible.

Overall, the improvement in data quality and cost reduction in passive sampling will ultimately lead to better and more widespread monitoring of organic pollution in terrestrial waters. To ensure these benefits impact society via wider use of the technology we will be working with industry, governmental bodies, and non-governmental organisations during the project to lay the foundations for future exploitation beyond this project.