Science Opportunities - Basic Research Opportunities in Earth Science - page 30

reforestation), as well as by silicate weathering. However, the temporal and
spatial variability of carbon sources and sinks is not well documented, especially
on longer time scales. New evidence regarding the influence of microscopic and
macroscopic organisms on the weathering of silicate minerals and the transfer of
soluble carbonates to the substratum may provide constraints on weathering
reactions and global climate change.
The Interactions of Life, Water, and Minerals
Organic molecules and microorganisms strongly affect the kinetics of
important geological and pedological processes. However, these materials studies
are only beginning to address the quantitative significance of microbial
interactions in mineral weathering, soil formation, and the geochemical cycling
of metals, nutrients, and other elements or isotopes ( Figure 2.3 ). For example, it
is clear that organic compounds influence the burial of reduced carbon and help
drive the decay or retention of toxins in natural soils and sediments, although
mechanisms for the preservation of carbon are still being debated. The
interactions of water with minerals and other materials in soils, sediments, and
rocks are critical in the dispersal and concentration of chemical species, the
migration of contaminants, and the accumulation of natural resources. The
architecture of porous media influences transmission dynamics, sorption-
desorption kinetics, and chemical fates. Models of physical transport in
heterogeneous media are being developed to understand chemical and biological
reactions, nutrient cycling, and the fates of contaminants. Such models are being
constrained by imaging and analytical measurements developed over the past few
years and will provide new insight into the physical, biological, and chemical
influences on water quality and availability.
The Land-Ocean Interface
New technology is yielding vastly improved insights to the nature and
dynamics of coastal sedimentary environments. 2 For example, scanning airborne
lasers are measuring seafloor bathymetry and topography of coastal areas with
unprecedented accuracy and spatial coverage allowing assessment and
understanding of coastal change in ways that were not possible only a
2 Coastal Sedimentary Geology Research: A Critical National and Global Priority,
results of a workshop held in Honolulu, Hawaii, November 9-12, 1999.