Distribution of terpenes in heartwood and sapwood of loblolly pine

The purpose of this study was to investigate the distribution of terpenes in loblolly pine with respect to the potential impact of volatile organic compound emissions during drying. The total terpene content in the inside, middle, and outside of increment core sections from twelve 40-year-old loblolly pines was determined over a period of 14 months. A method for extracting and analyzing terpenes from increment core sections is described. The average terpene contents and standard deviations (in parentheses) in the heartwood, inner sapwood, and outer sapwood of the increment core samples were 2.3 (0.42), 0.77 (0.31), and 0.35 (0.16) percent, respectively. The distribution profile of terpenes in pines could be better defined by analyzing smaller increment core sections from locations throughout a large number of trees. Pines and other softwood species contain a variety of monoterpenes and other compounds with boiling points in the range of 150° to 215°C. The monoterpenes have been observed to make up a substantial fraction of volatile organic compounds (VOCs) that are emitted during drying of southern pine lumber (Ingram et al. 2000b). This paper reports a portion of our efforts to gain a better understanding of the occurrence and distribution of terpenes in loblolly pine and the impact on VOC emissions during drying of lumber. Drew and Pylant (1966) reported the composition and laboratory yields of turpentine from 28 pulpwoods commonly used in the United States and Canada. The turpentine yield from samples of loblolly pine was 0.970 gal/ton of wood on a dry weight basis (about 7 lb/dry ton). The major components were -pinene, camphene, -pinene, myrcene, limonene, -phellandrene, trans -terpineol, 4-allylanisole, and isoborneol. Samples for this study were representative of the species and yields were determined by condensing the volatile oil from simulated pulping conditions. The major components found in the exhaust from a laboratory scale kiln when drying samples of loblolly pine were -pinene, camphene, -pinene, myrcene, limonene, and 4-allylanisole (Ingram et al. 2000b). In a study of VOC emissions from drying lumber samples with different frequency of knot occurrences, the concentrations of terpenes found in sapwood, heartwood, and knot samples by methylene chloride extraction were 0.31, 1.51, and 3.31 percent, respectively. Results from this study also indicated that an increase in the presence of heartwood and knots in lumber could result in an increase in VOC emissions during drying (Ingram et al. 2000a). The distribution and composition of terpenes in 24to 45year-old radiata pine were previously reported (Kininmonth and Whitehouse 1991). The concentration of terpenes was found to be highest in samples of heartwood and decreased in samples nearer the outside of the tree bole. The average concentration of extractives was 1.8 to 2.3 percent on a dry weight basis and approximately one-third of the extractive content was assumed to be terpenes. The concentration of extractives also decreased toward the top of the stem. The overall objective of this research project was to investigate the seasonal and climatic variation of terpenes in loblolly pines and the potential impact on VOC emissions. The results from that part of the research project were reported by Conners et al. (2001). The objective of the research reported in this paper was to determine the percent concentration of terpenes in different tissue types of loblolly pine and the potential impact on VOC emissions during the drying of lumber. The authors are, respectively, Former Graduate Student (currently employed by Novartis Pharmaceuticals, Co.), Research Associate II, and Professor, Dept. of Forest Products, Mississippi State Univ., Mississippi State, MS ([email protected]). This paper was received for publication in February 2005 Article No 10014 ✳Forest Products Society Member. ©Forest Products Society 2006. Forest Prod J 56(7/8):46-48.