Susan J. Tewalt

Bio: Susan J. Tewalt is an academic researcher from United States Geological Survey. The author has contributed to research in topics: Coal & Coal mining. The author has an hindex of 11, co-authored 31 publications receiving 571 citations.

Global mercury emissions to the atmosphere from anthropogenic and natural sources

Abstract: . This paper provides an up-to-date assessment of global mercury emissions from anthropogenic and natural sources. On an annual basis, natural sources account for 5207 Mg of mercury released to the global atmosphere, including the contribution from re-emission processes, which are emissions of previously deposited mercury originating from anthropogenic and natural sources, and primary emissions from natural reservoirs. Anthropogenic sources, which include a large number of industrial point sources, are estimated to account for 2320 Mg of mercury emitted annually. The major contributions are from fossil-fuel fired power plants (810 Mg yr−1), artisanal small scale gold mining (400 Mg yr−1), non-ferrous metals manufacturing (310 Mg yr−1), cement production (236 Mg yr−1), waste disposal (187 Mg yr−1) and caustic soda production (163 Mg yr−1). Therefore, our current estimate of global mercury emissions suggests that the overall contribution from natural sources (primary emissions + re-emissions) and anthropogenic sources is nearly 7527 Mg per year, the uncertainty associated with these estimates are related to the typology of emission sources and source regions.

Commodity Price Shocks and Civil Conflict: Evidence from Colombia

Abstract: How do income shocks aect armed con‡ict? Theory suggests two op- posite eects. If labor is used to appropriate resources violently, higher wages may lower con‡ict by reducing labor supplied to appropriation. This is the opportunity cost eect. Alternatively, a rise in contestable income may increase violence by raising gains from appropriation. This is the rapacity eect. Our paper exploits exogenous price shocks in inter- national commodity markets and a rich dataset on civil war in Colombia to assess how dierent income shocks aect con‡ict. We examine changes in the price of agricultural goods (which are labor intensive) and natural resources (which are capital intensive). We focus on coee and oil, the two largest exports. We …nd that a sharp fall in coee prices in the 1990s increased violence dierentially in regions growing more coee, by lower- ing wages and the opportunity cost of joining armed groups. In contrast, a rise in oil prices increased violence dierentially in the oil region, by in- creasing municipal revenue siphoned through rapacity. This pattern holds in several other agricultural and natural resource sectors, providing robust evidence that price shocks aect con‡ict in opposite directions depending on the factor intensity of the commodity.

Advances in Membrane Distillation for Water Desalination and Purification Applications

Abstract: Membrane distillation is a process that utilizes differences in vapor pressure to permeate water through a macro-porous membrane and reject other non-volatile constituents present in the influent water. This review considers the fundamental heat and mass transfer processes in membrane distillation, recent advances in membrane technology, module configurations, and the applications and economics of membrane distillation, and identifies areas that may lead to technological improvements in membrane distillation as well as the application characteristics required for commercial deployment.