HIGH levels of pollutants have been found in waterways across the Downend area in sampling by ‘citizen scientists’.
Every summer the Bristol Avon Rivers Trust asks volunteers to collect samples from waterways across the region to test them for common pollutants, including phosphates and nitrates.
This year more than 130 volunteers collected 202 samples in early July as part of the ninth RiverBlitz campaign.
The results have been published by BART, which found that locally, high nitrate and medium phosphate pollution was found in the River Frome at Lincombe Barn woods, and close to Frenchay Bridge.
Samples taken from the stream at the Overndale Road end of Lincombe Barn woods had varying levels of pollutants, but three out of four of them contained high levels of nitrates.
At Leap Valley, high levels of nitrates and varying levels of phosphates were found in the stream, with medium levels of both pollutants found in a pond in the woods.
Medium levels of nitrates and high levels of phosphates were found in the Frome at Moorend.
The nearby Bradley Brook, which runs into the Frome at Hambrook, had medium levels of both nitrates and phosphates.
BART says nutrients, particularly phosphates and nitrates, are among the most common pollutants of freshwater worldwide and are widely used as indicators of water quality.
Although they occur naturally in healthy rivers, high concentrations lead to harmful algal blooms which can harm other plant life and fish.
High levels are caused by pollutants including fertilisers, manure, sewage, urban surface water run-off and household products like detergents.
Across the region, BART said 69% of samples had high nutrient loads of phosphate and nitrate combined, with 3.5% recording low nutrient levels.
However, this was an improvement on last year, when 88% of samples confirmed high nutrient loads and only one out of 290 samples showed low nutrient concentrations.
BART chief executive Simon Hunter said: “The Bristol Avon RiverBlitz provides a snapshot of the catchment’s water quality during a week in July.
“While it may not offer detailed insights into individual streams, the expanding dataset from multiple years reveals trends across the catchment.”
He said that across the region, high pollutant levels were recorded along the Bristol Frome, River Trym, and the Avon between Bristol and Bath.
Areas with high nitrate levels included the Avon between Bristol and Bath, the lower Bristol Frome, south Bristol streams and most sites on the Trym, with only 5% of samples showing low nitrate levels.
Mr Hunter said: “The data collected suggests, during the week of the Bristol Avon RiverBlitz, that nutrient pollution is likely impacting water quality and, consequently, the health of some watercourses and wildlife across the Bristol Avon.”
He said this year’s milder summer may have resulted in lower nutrient levels than in the previous two years’ surveys, adding: “It’s important to note that the Bristol Avon RiverBlitz captures water quality measurements at a specific moment in time, and there are several other parameters we did not test that could also impact river health, such as bacterial and chemical readings.”
To view figures from the survey visit bristolavonriverstrust.org/riverblitz.