The use of open-top chambers to study the effects of air pollutants, in particular sulphur dioxide, on the growth of ryegrass Lolium perenne L. Part II—The long-term effect of filtering polluted urban air or adding SO 2 to rural air

Abstract

Two long-term (10-month) investigations were conducted during consecutive years (1978–1979 and 1979–1980) to determine the effect on the growth of ryegrass Lolium perenne L., cv S23, of both filtering polluted urban air and adding SO 2 to clean rural air. Four open-top chambers and two unchambered plots were used at each of two sites in NW England: St Helens, Lancashire, a polluted urban site where ambient air was charcoal filtered in two of the chambers, and Ness, Cheshire, a relatively unpolluted rural site, where SO 2 was added to the ambient air in two of the chambers. There were no significant differences between the yield of grasses grown in unfiltered (∼90 μg SO 2 m −3) or filtered (∼35 μg SO 2 m −3) air at St Helens. At Ness there was a significant 12% reduction in the overall shoot yield of grasses grown in the presence of additional SO 2 (annual mean ∼120 μg m −3) compared with those grown in ambient air (annual mean ∼38 μg m −3) in 1978–1979, but in 1979–1980 only a 6% depression ( p⩽0·05) in the shoot yield of the grasses grown in 165 μg SO 2 m −3 compared with those grown in 35 μg m −3 was recorded. Effects of additional SO 2 occurred mainly in the winter and early spring months, when SO 2 levels were 135 and 220 μg m −3, respectively, in the two experiments. Summer concentrations of less than 100 μg SO 2 m −3 produced no yield reductions during the most rapid growth period. The results are discussed in relation to interactions between environmental factors and SO 2 on shoot and root growth.