Abstract
Many researchers have written about the presence of pharmaceuticals, personal care products and plant protection products commonly termed as polar organic pollutants in surface waters globally, and the possibility of their presence affecting the biodiversity of macroinvertebrates. To my knowledge there has been very little work on the presence of these contaminants and their likely effect on the biodiversity of macroinvertebrates in chalk rivers.The intention of this research was to assess the presence and concentration of these pollutants within the benthic zone of two chalk streams in England over the course of one year. The research used passive sampling in specially designed equipment, and liquid chromatography tandem mass spectrometry, using the results to calculate an ecotoxicological hazard and risk rating. Assessments of the biodiversity and community structure of macroinvertebrates were used to determine the differences in the spring and autumn seasons over a period of four years, and to compare them with a database of reference sites.
A total of 121 polar contaminants including their metabolites and transformation products were identified consisting of 58 pharmaceuticals, 3 personal care products and 60 plant protection products. Many of the contaminants were present in every season, some at every site and others were present seasonally. Sources were identified as point sources from wastewater treatment plants, septic tanks, storm overflows and run off, and non-point sources such as on-site-package-treatment plants via groundwater. High risk sites were more likely to be found where wastewater discharged direct to the river in all seasons. The risk assessment was evaluated using a hazard quotient of the mixtures of pollutants present at every site in every season.
There was an overall 10% total decrease in macroinvertebrate abundance, a 97% decrease in aquatic fly abundance, and a change in diversity compared with the data contained in the database of reference sites. There was a notable decrease in abundance during a period when a drought was experienced in the region which would have caused concentrations of the pollutants identified in this thesis to increase, this was followed by flooding when macroinvertebrates may also have drifted downstream. Both factors may have contributed to the decline seen, however, there was little evidence of any recovery.
In conclusion, an unequivocal link between the presence of anthropogenic compounds and the overall and continuing decline in the abundance and biodiversity of river fly life and of the impact on community structure was identified.
| Date of Award | 9 May 2025 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Gary Fones (Supervisor), Alex Ford (Supervisor) & Graham Mills (Supervisor) |