Influence of Light and Temperature on Monoterpene Emission Rates from Slash Pine

Abstract

High levels of ozone have been measured in rural and remote locations, far from significant anthropogenic sources of oxidant precursors. Elevated oxidant concentrations in these areas could be the result of transport into these areas and/or photooxidation of locally produced biogenic hydrocarbons. Volatile organics, including monoterpenes, have been detected in the atmosphere (I 1, 15, 18, 25), and the reports suggested that the hydrocarbons had a biogenic origin. Robinson (17) proposed that hydrocarbon concentrations were governed by both long distance transport and local production. However, there are only limited data available concerning the biogenic emission rates of potential photochemically reactive hydrocarbons such as the monoterpenes.The data used to estimate emission rates for monoterpenes were collected using a variety of experimental techniques ranging from static encapsulation chambers to profile measurements in the field.The degree of environmental control during the measurement period was highly variable making it difficult to establish a clear relationship between monoterpene emission rates and environmental conditions. The data base for monoterpene emission rates is limited almost exclusively to a-pinene. Only limited data are available conceming the influence of the environment, particularly light and temperature, on monoterpene emission rates. Apparently light does not directly influence monoterpene emissions even though photosynthate is required for biosynthesis (4,13).The emissions of camphor (23) and a-pinene increase with temperature (1, 10, 13).The objectives of this study were to (a) determine the monoterpene emission rates from intact plants under controlled environmental conditions using a dynamic mass balance gas exchange chamber; (b) determine the independent influence of light and temperature on monoterpene emission rates; (c) determine the emission rates of monoterpenes from dead needles; and (d) approximately 15 months old when sampled and appeared healthy. The plants had both mature and recently elongated needles, none of which appeared to be defective, and there were no significant bark lacerations or gum exudations.Gas Exchange Chamber. A dynamic mass balance gas exchange chamber was used to determine monoterpene emission and photosynthetic rates (22). The gas exchange chamber was housed in a controlled environment chamber which regulated light intensity and cooling. Ambient air was pumped through an Aadco pure air generator to remove hydrocarbons and CO2 and to reduce the dewpoint. CO2 and water vapor were added back to the air stream to obtain the desired concentrations within the gas exchange chamber. C02, water vapor and hydrocarbons were measured at the gas exchange chamber's inlet and outlet ports, and air flow was measured at the chamber inlet. Photosynthetic and monoterpene emission rates were determined using the equations for calculating gas fluxes in an open gas exchange chamber (19).During experiments, the CO2 concentration in the gas exchange chamber wa...

Reassessment of biogenic volatile organic compound emissions in the Atlanta area

“…BVOC emission rates increase exponentially (up to approximately 38°C for isoprene) with. increasing leaf temperature, while isoprene emission rate also increases with increasing light intensity up to approximately 1000~tmolm-2s -1 (Guentber et al, 1993;Tingey et al, 1979Tingey et al, , 1980. Chameides et al (1988) assumed that forests in the llcounty Atlanta ozone nonattainmcnt area emit no isoprene at night, increased linearly to a rate of 2100 pg-C m-2 h-1 at noon, remained constant until 3 PM local time, and then decreased linearly to zero at 7 PM local time.…”

Monoterpene emissions from a Pacific Northwest Old-Growth Forest and impact on regional biogenic VOC emission estimates

“…Monoterpene emissions from most plants are known to increase exponentially with temperature (Tingey et al, 1980;Juuti et al, 1990;Guenther et al, 1993). Standard emission factors (sometimes referred to as basal emission rates) are typically calculated using the Guenther et al (1993) algorithm; E meas ¼ E s exp½bðT2T s Þ that normalizes the measured emission rates at ambient temperatures to a standard temperature of 30 C. In this equation, E meas is the measured emission rate at leaf temperature T ( C), E s is the emission rate at standard temperature T s (30 C) and b ( C À1 ) is an empirical temperature coefficient ranging from 0.06 C À1 to 0.14 C À1 , with an average value of 0.09 C À1 .…”

Light dependency of VOC emissions from selected Mediterranean plant species

“…Tingey et al, 1981;Monson and Fall, 1989;Sharkey and Loreto, 1993), nor on monoterpene emissions (e.g. Tingey et al, 1980;Loreto et al, 1996), The apparent non-dependence of VOC emissions on G s has been explained by the low concentrations of these compounds in the leaf tissue, which increase when G s decreases and which compensate for stomatal closure. Kesselmeier and Staudt (1999) also suggested that increased internal VOC concentrations could increase diffusion of monoterpene compounds through the leaf cuticular membrane.…”