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 I—characteristics of modified open-top chambers used for both air-filtration and SO 2-fumigation experiments

Abstract

Open-top chambers were developed to study the effect on the shoot growth of ryegrass Lolium perenne L., cv S23, of filtering the atmosphere in an urban area in northwest England. Modifications to standard open-top chambers minimised differences in microclimatic conditions within these chambers but small differences were still measured, such as a 15–25% reduction in light intensity, a 1–2°C temperature rise at low ambient temperatures and the absence of hoar frost due to the continuous air movement. In a preliminary experiment the effect of the chambers on shoot yield overwinter was small but there was a 29% decrease of early summer growth. The filtering efficiency of these chambers produced a 56% reduction in SO 2 concentration over an 8-month study period, and the reduction of urban SO 2 concentrations from 125 to 61 μ m −3 in the preliminary experiment resulted in a significant 16% increase in shoot yield. This effect may, however, also be ascribed to a reduction in the concentrations of O 3 and NO 2, and to a lesser extent NO, which are now generally present in urban areas of the UK at concentrations equal to or greater than SO 2. These chambers were also used in subsequent experiments for assessing the effects of adding SO 2 to unfiltered air rural site.