Effect of heating history on the emission of volatile organic compounds from asphalt materials.

Asphalt binders release hazardous fumes during high-temperature heating that severely endanger human health and pollute the environment. In this study, a volatile organic compound (VOC) generation and detection device comprising a portable VOC detector was developed, and two heating modes (intermittent and continuous heating) were established to explore the influence of heating history on the VOC emission behavior of five asphalt samples. The changes in the VOC species and content, as determined by the heating history, were analyzed via gas chromatography-mass spectrometry (GC-MS). Finally, the key factors affecting the emission of VOCs from asphalt are discussed based on the four components of asphalt materials. The results indicated that the emission of VOCs from asphalt materials under intermittent heating conditions decreased significantly with increasing heating history (significantly fewer VOCs, including 13 common components such as alkanes, benzenes, and hydrocarbon derivatives, were emitted under this condition than under continuous heating conditions at the same temperature point). Compared with continuous heating, intermittent heating is more conducive for studying asphalt VOCs. Under intermittent heating, different asphalt materials exhibited similar VOC emission curves; the VOCs were mainly emitted during the first two heating stages (200 and 180 °C, respectively). Thus, it can be deduced that asphalt VOC emissions were induced by the synchronized actions of the four components of asphalt materials. Therefore, different components can contribute to the emission of several VOCs of the same composition. The heavy and light components mainly facilitate the emission of common components with carbon atomic numbers <18 and > 18, respectively.

[Analysis of HLA-A, B, and DRB1 polymorphism and genetic distance in Han population living in Yantai and Weihai regions of Shandong province].

OBJECTIVE: To investigate allelic and haplotypic polymorphisms of human leukocyte antigen(HLA) genes at A, B and DRB1 loci in Yantai and Weihai Han population and analyze the genetic relationship between Yantai, Weihai Han population and other populations. METHODS: A total of 4062 unrelated Han ethnic individual from Yantai and Weihai regions were genotyped by polymerase chain reaction-sequence specific olignucleotide probe(PCR-SSOP) for HLA-A, B and DRB1 loci. Allelic and haplotypic frequencies were estimated by maximum likelihood estimation method using Arlequin 3.5 software. Genetic distances were computed, and phylogenetic tree was constructed using Mega5.0 software. RESULTS: Respectively 18, 33 and 13 alleles were observed at HLA-A, B and DRB1 loci. The most frequent alleles were HLA-A*02(0.2935), HLA-B*15(0.1485) and HLA-DRB1*15(0.1621). And the most common three loci haplotype was A*30-B*13-DRB1*07(0.0649). A*33-B*58, A*66-DRB1*13 and B*08-DRB1*03 showed the strongest linkage disequilibrium. Yantai and Weihai Han population has the shortest genetic distance with Jilin Han population (0.0034). CONCLUSION: The HLA-A, B and DRB1 loci are highly polymorphic in Han population from Yantai and Weihai, and this population has closest relationship with Han population from Jilin province.