Geology topics

C. Trettin

Publications and source records attributed to C. Trettin.

3 recordsLinked to original sources

USGS2006

The carbon balance of North American wetlands

We examine the carbon balance of North American wetlands by reviewing and synthesizing the published literature and soil databases. North American wetlands contain about 220 Pg C, most of which is in peat. They are a small to moderate carbon sink of about 49 Tg C yr-1, although the uncertainty around this estimate is greater than 100%, with the largest unknown being the role of carbon sequestration by sedimentation in freshwater mineral-soil wetlands. We estimate that North American wetlands emit 9 Tg methane (CH 4) yr-1; however, the uncertainty of this estimate is also greater than 100%. With the exception of estuarine wetlands, CH4 emissions from wetlands may largely offset any positive benefits of carbon sequestration in soils and plants in terms of climate forcing. Historically, the destruction of wetlands through land-use changes has had the largest effects on the carbon fluxes and consequent radiative forcing of North American wetlands. The primary effects have been a reduction in their ability to sequester carbon (a small to moderate increase in radiative forcing), oxidation of their soil carbon reserves upon drainage (a small increase in radiative forcing), and reduction in CH4 emissions (a small to large decrease in radiative forcing). It is uncertain how global changes will affect the carbon pools and fluxes of North American wetlands. We will not be able to predict accurately the role of wetlands as potential positive or negative feedbacks to anthropogenic global change without knowing the integrative effects of changes in temperature, precipitation, atmospheric carbon dioxide concentrations, and atmospheric deposition of nitrogen and sulfur on the carbon balance of North American wetlands.

Wetlands↗

USGS2005

Results of the acid rain program: Status and trends of emissions and environmental impacts (1990–2002)

Both SO2 and NOx emissions from power generation sources have significantly declined under Title IV. In 2002, SO2 emissions from Title IV-affected sources totaled 10.2 million tons and NOx emissions from all Title IV-affected sources totaled 4.5 million tons, down 35% and 33% respectively from 1990 levels. Sources in states with the highest emissions continue to reduce their emissions the most, and there have been no significant geographic shifts in emissions. The benefits of these emission reductions include improvements in air quality (which are expected to lead to significant human health benefits), broad-scale reductions in sulfate deposition, and improvements in visibility. While surface waters in some areas have begun to show signs of recovery from acidification, acidification is still occurring in many areas. Although there have been no broad-scale regional reductions in nitrogen deposition, nitrogen deposition has declined in some areas, benefiting some nitrogen-sensitive forests and coastal waters and acid-sensitive lakes and streams.

Book chapter↗

USGS2005

Assessing acid deposition: Advances in the state of science

NAPAP has a long history of conducting research related to acid deposition. Throughout the 1980s NAPAP supported a large number of research projects that confirmed the link between SO 2 and NO x emissions and acidic lakes and streams hundreds of miles away. Recent research is confirming the tight link between emissions of SO 2 and the amount of several different forms of sulfur in the atmosphere and in precipitation, and improving our ability to measure acid deposition. Research has continued since 1990, albeit on a smaller scale, to increase our understanding of how acid deposition affects trees, soils, lakes, streams, coastal waters, and building materials such as stone and copper. Some of the areas where the most research has been done include: the importance of calcium in mediating soil and forest response to acidification; the role of nitrogen in acidification and recovery from acidification; and the role of nitrogen deposition in coastal ecosystems. In addition, substantial advances have been made in understanding the human health impacts of fine particles, including sulfates and nitrates, which are briefly mentioned here.

Book chapter↗