28 April 1995

Non-farm pesticide widespread in water

By Liz Mason

MOST groundwater pollution is caused by non-agricultural pesticides, says a report for the National Rivers Authority.

It says pesticides, used on roads and railway lines, are widespread in groundwaters and a detailed survey is needed to assess their impact.

"The land use with least known about it, but with the most observed impact on groundwater, is the non-agricultural use for weed control on our road and rail systems," says the report by the Water Research Council.

Non-agricultural use of atrazine and simazine has been banned by MAFF, forcing a switch to alternatives. Tests to detect these, and other new pesticides, in water are being "actively pursued", says the report.

It summarises results of long-term studies on the River Granta catchment near Cambridge, which lies on a chalk aquifer, and Assarts Farm, near Warsop, Notts on Sherwood Sandstone.

The research, which began in 1984, shows that under normal agricultural use, most acid herbicides, including isoproturon and the carbamates, are rarely detected below 3m from the soil surface.

Present little threat

They are "believed to present little threat to groundwater quality", the report says.

"Triazines are more persistent beneath crops and do present a distinct threat to groundwater quality," it adds. "Mecoprop, an acid herbicide, appears to be persistent in sandstone but there is no evidence of deep penetration."

Surface water monitoring showed more pesticides at higher concentrations in the winter when river flows were highest. "Simazine occurs quite commonly but the most common pesticide in the Granta is isoproturon," it says. In the winter months it "consistently exceeds" the ECs limit for drinking water.

Other recommendations made by the report include:

lA study into transformation products (TPs) produced by the breakdown of pesticides in the environment.

lA study to determine the rate of breakdown of major pesticides.

lA comprehensive database of the physical and chemical properties of pesticides and their TPs.

lA review of UK research into the transport and into the fate of pesticides.

Another NRA report, due to be published this summer, is expected to update the status of pesticides in aquifers. &#42