Effects of incomplete combustion on atmospheric chemistry: Black carbon climate forcing and global carbon monoxide emissions

This thesis is actually the composition of two separate studies aimed at further understanding the role of incomplete combustion products on atmospheric chemistry. The first explores the sensitivity of black carbon (BC) forcing to aerosol vertical location since BC has an increased forcing per unit mass when it is located above reflective clouds. We used a column radiative transfer model to produce globally-averaged values of normalized direct radiative forcing (NDRF) for BC over and under different types of clouds. We developed a simple column-weighting scheme based on the mass fractions of BC that are over and under clouds in measured vertical profiles. The resulting NDRF is in good agreement with global 3-D model estimates, supporting the column-weighted model as a tool for exploring uncertainties due to diversity in vertical distribution. BC above low clouds accounts for about 20% of the global burden but 50% of the forcing. We estimate maximum-minimum spread in NDRF due to modeled profiles as about 40% and uncertainty as about 25%. Models overestimate BC in the upper troposphere compared with measurements; modeled NDRF might need to be reduced by about 15%. Redistributing BC within the lowest 4 km of the atmosphere affects modeled NDRF by only about 5% and cannot account for very high forcing estimates. The second study estimated global year 2000 carbon monoxide (CO) emissions using a traditional bottom-up inventory. We applied literature-derived emission factors to a variety of fuel and technology combinations. Combining these with regional fuel use and production data we produced CO emissions estimates that were separable by sector, fuel type, technology, and region. We estimated year 2000 stationary source emissions of 685.9 Tg/yr and 885 Tg/yr if we included adopted mobile sources from EDGAR v3.2FT2000. Open/biomass burning contributed most significantly to global CO burden, while the residential sector, primarily in Asia and Africa, were the largest contributors with respect to contained combustion sources. Industry production in Asia, including brick, cement, iron and steel-making, also contributed significantly to CO emissions. Our estimates of biofuel emissions are lower than most previously published bottom-up estimates while our other fuel emissions are generally in good agreement. Our values are also universally lower than recently estimated CO emissions from models using top-down methods.

Sexuality in the media and emotional well-being among lesbian, gay, & bisexual adolescents

LGB teens’ feelings, desires, and physical attractions run contrary to the heteronormative standards of American society. As such, LGB youth often experience feelings of sadness and dejection that can lead to depression and suicidal tendencies (Russell & Joyner, 2001). Evaluating the factors that could possibly influence the emotional well-being of LGB youth would be an important undertaking given the hindrances LGB adolescents face during sexual socialization. The purpose of this dissertation was to study the portrayal of sexuality in media popular with LGB adolescents and to assess the relationship between media exposure and emotional well-being among LGB teens. In particular, this dissertation distinguished between mainstream media and gay- and lesbian-oriented (GLO) media. GLO media were defined as any media outlet specifically designed, produced, and marketed for gay and lesbian audiences. Two studies were conducted to serve as the initial investigation in a program of research that will be designed to better understand the role of media in the lives of LGB individuals. The first study of this dissertation was a content analysis of the television programs, films, songs, and magazines most popular with LGB teens as determined by self-reports of media consumption in a survey of media use. A total of 96 media vehicles composed the content analysis sample, including 48 television programs, 22 films, 25 musical artists, and 6 magazines. Using a coding scheme that was adapted from previous media sex research, Study 1 measured the frequency of sexual instances as well as the type, nature, and source characteristics for each sexual instance. Results of the content analysis suggest that heterosexuality reigns supreme in mainstream media. When LGB sexuality is depicted in mainstream media, it is often sanitized. LGB sexual talk is rarely sexual; rather it is primarily about the social or cultural components of being lesbian, gay, or bisexual. LGB sexual behavior is also rare in mainstream media, which tend to depict LGB individuals as non-sexually as possible. LGB sexuality in mainstream media exists, but is more about proclaiming LGB identity than actually living it. GLO media depicted LGB sexuality more frequently than mainstream media did. GLO media often depict LGB sexuality in a more realistic manner. LGB sexual talk is about LGB identity, as well as the relational and sexual aspects of being a sexual minority. LGB sexual behavior is commonplace in GLO media, depicting LGB individuals as sexual beings. LGB sexuality in GLO media is prevalent and relatively authentic. The second study was a survey that assessed the relationship between media exposure (both mainstream media and GLO media) and LGB teens’ emotional well-being, considering self-discrepancy as an important mediating variable in that relationship. Study 2 also considered age, sex, and sexual identity commitment as possible moderating variables in the relationship between media exposure and emotional well-being. In Study 2, emotional well-being was defined as lower levels of dejection-related emotions. LGB adolescents (N = 573) completed a questionnaire that was used to investigate the relationships between media exposure and emotional well-being. Results of the survey indicated that mainstream media exposure was not significantly associated with dejection-related emotions. In contrast, GLO media exposure was negatively related to feelings of dejection even when controlling for age, sex, race, perceived social support, school climate, religiosity, geographical location, sexuality of peers, and motivation for viewing LGB inclusive media content. Neither age nor sex moderated the relationships between media exposure variables and dejection, but sexual identity commitment did act as a moderator in the relationship between GLO media exposure and dejection. The negative relationship between GLO media exposure and dejection was stronger for participants lower in sexual identity commitment than for participants higher in sexual identity commitment. In addition, the magnitude of discrepancies between the actual self and the ideal self mediated the relationship between GLO media exposure and dejection for LGB adolescents low in sexual identity commitment. However, self-discrepancy did not mediate the relationship between GLO media exposure and dejection for LGB teens highly committed to their sexual identities. Results of both the content analysis and the survey are discussed in terms of implications for theory and method. Practical implications of this dissertation’s findings are also discussed, as well as directions for future research.