Glasgow Caledonian University1
Introduction Presented are the results of a sampling campaign investigating the spatial distribution of pharmaceutical micropollutants, in the upper and middle reaches of a river catchment. The River Almond and its tributaries receive effluent from multiple sewage treatment works (STW). Pharmaceutical concentrations in surface waters depend on the pollutant input load, environmental degradation and / or sequestration during transport and the available dilution. There are 20 distinct Water Bodies, in the sense of the River Basin Management Plan, within the River Almond catchment. Under the Environmental Quality Standards (EQS) Directive (2008/105/EC) (1), all water bodies must comply with EQS. Following the inclusion of three pharmaceutical products on a 'watch list' (2) and with a real possibility of pharmaceuticals being identified as Priority Substances in the future, a better understanding of the environmental distribution and fate of such pollutants is desirable. Materials and Methods Daily grab samples were taken at 5 locations within the catchment for 4 consecutive days in June 2013, during dry weather. The locations were chosen to generally build up a picture of concentrations across the catchment and with the specific objectives to 1) compare river loads and concentrations upstream, 400m downstream and 10km downstream from a trickling filter plant, and 2) establish mass balance before and after a confluence of a tributary and the main river. In order to be able to calculate load, a depth profile was taken at each river location and flow velocity readings were taken daily using a simple handheld flow meter (Geopacks MFP51). Temperature readings were also obtained. Alongside conventional water quality parameters, concentrations for 20 pharmaceutical compounds were determined by using a Thermo Scientific Q Exactive orbitrap mass spec with a Dionex Ultimate 3000 LC system; below we report results for Atenolol, Ibuprofen, Bezafibrate, Carbamazepine, Lidocaine and Clarithromycin. Results and Discussion NB Loads have not yet been calculated as the flow data is still awaiting analysis. All compounds were found on most days at all locations, apart from one location upstream from all STW, which - as expected - did not show any pharmaceutical pollution. Concentrations at other locations in the river were generally measurable but below 1ng/l. For Ibuprofen, concentrations at each location were consistent within a factor 2 over the sampling period. Clarithromycin, Bezafibrate, Lidocaine and Carbamazepine showed a little more variation across the days, generally up to a factor 6, whereas Atenolol showed the most variation across the days as this compound was not detected every day. In respect of objective 1), comparing the locations 400m and 10km downstream from STW, we found that the mean concentrations of Atenolol and Clarithromycin were a factor 5 (Atenolol) and 6 (Clarithromycin) lower at the downstream location The mean values for Carbamazepine and Ibuprofen however were only slightly (around 30%) reduced. For Bezafibrate, concentrations were also lower by 30% on 3 days, but on the 4th day the downstream location concentration was below LOQ. Unexpectedly, Lidocaine was found in higher concentrations at the downstream location. A suggested explanation is the presence of other possible inputs: although no other STW inputs are present along the stretch, there are 18 authorised private sewage discharge points (e.g. septic tanks) in the tributary's catchment. Whilst the total population served by these is likely to be small compared to that served by the STW, which serves 5000 people, they may have contributed to the downstream concentrations. As Lidocaine is also used in veterinary practice, farm run-off may also play a role. Further data on the nature and size of the authorised discharges into the river is currently being sought. Two smaller tributaries join the investigated stretch of water between the two sampling points, so that additional dilution will have been a factor in the reduction of concentrations. Once the flow data are analysed we will be able to report on relative attribution to flow and load in more detail. In respect of objective 2), samples were taken in the River Almond itself and in one of its tributaries upstream from the confluence, and in the River Almond downstream from the confluence. Both streams contain treated effluent. We see that for Atenolol, the lowest concentration was found downstream from the confluence. It is likely that degradation between the upstream and the downstream sampling points played a role as no other dilution takes place. As concentrations for Bezafibrate, Carbamazepine, and Clarithromycin in the two contributing streams are similar, it is no surprise that the concentrations downstream from the confluence are also similar. For Lidocaine and Ibuprofen, concentrations in the tributary are higher than in the upstream River Almond, resulting -- as expected - in an increase of concentrations in the River Almond downstream from the confluence. Whilst mass balance calculations have not yet been possible pending the processing of flow data, the results appear to be broadly consistent with expectations. Conclusion From the results, it is clear that pharmaceutical pollutants can be transported over a long range. Some compounds, such as Atenolol, appear to be degraded or sequestered considerably along a 10km stretch of river, but Carbamazepine and Ibuprofen are not, although the influence of private sewage discharges must be investigated further. Despite multiple larger STW discharging into the River Almond, it is the smaller tributary, which receives effluent only from one relatively small STW, that shows the highest levels of pharmaceutical pollution due to low available dilution. The high levels of Lidocaine apparently not issuing from any STW remind us that other sources of pharmaceutical pollution should not be ignored. 1. European Parliament (2008) Directive 2008/105/C of the European Parliament and of the Council on 16 December 2008 on environmental quality standards in the field of water policy. Council of the European Union 16/12/2008 2. European Parliament (2013) Surface waters: 12 new controlled chemicals, three pharmaceuticals on watch list. Press Release Plenary Sessions 01072013 edn, EU.