Seasonal changes in the lead content of pasture grass growing near a motorway

The above-ground portion of perennial ryegrass (Lolium perenne), in fields both bordering and distant from the M6 motorway in Cheshire (Great Britain), was sampled monthly during the period October 1977–October 1978.

A 10-fold seasonal variation in lead level was found at all sites. The maximum level near the motorway (285 μg/g) was found during the ‘winter’ months, whilst the lowest level (15 μg/g) was found from May to August. It was concluded that the seasonal variation was a result of changes in the growth form of the plant. Other factors such as seasonal changes in atmospheric lead concentration and lead uptake from the soil may be of minor significance.

It is believed that present levels of lead in pasture grass, both close to and distant from the motorway, present no toxic hazard to grazing animals, but it may be advisable to restrict the use of pasture bordering major roads during the period December–April.