Data on rates of atmospheric deposition is limited in many montane ecosystems, where high spatial variability in meteorological, topographic, and vegetation factors contributes to elevated atmospheric inputs and to the creation of deposition hotspots. Addressing the ecological consequences of increasing deposition in these areas will require a better understanding of surface controls influencing atmospheric deposition rates at both large and small-scales. The overarching objective of this thesis research was to understand the influence of vegetation structure and canopy exposure on small-scale patterns of atmospheric sulfate, nitrate, and chloride deposition inputs to a conifer forest in the Santa Cruz Mountains, California. Throughfall ion fluxes (i.e., ions delivered in water that pass from the forest canopy to the forest floor), bulk deposition (i.e., primarily wet deposition), and rainfall data were collected during the rainy period from October 2012 to May 2013. Throughfall SO42-, Cl-, and NO3- fluxes were measured beneath eight clusters of Douglas fir (Pseudotsuga menziesii) trees (three trees per cluster) differing in tree size (i.e., diameter at breast height; DBH) and canopy exposure. In each cluster, a throughfall collector was placed 1-meter from the bole of an individual tree, for a total of 24 individual collectors. The position of each throughfall collector was recorded with a Trimble® GPS. In addition, tree height, tree diameter, and leaf area index, were measured for all trees. LiDAR data were obtained from GeoEarthScope’s Northern California Airborne LiDAR project and used to model the elevation (DEM), canopy surface height (DSM), tree height (CHM), slope, and curvature of the canopy surface across the entire study area. Over the rainy season, total throughfall flux of SO42--S, a conservative tracer of total deposition (wet + dry + fog), to Douglas fir clusters ranged from 1.44 - 3.84 kg S ha-1 wet season-1, while dry and fog deposition ranged from 0.13 -2.37 kg S ha-1 wet season-1. Total deposition to exposed mature tree clusters was 1.7-2.7 times higher than other clusters. Patterns of total Cl- fluxes (17.10 – 54.14 kg Cl- ha-1 wet season-1) resembled patterns of total SO42--S inputs. Overall, net throughfall fluxes (throughfall – bulk deposition) to Douglas fir trees clusters were more variable than total throughfall fluxes. Net SO42--S and Cl- fluxes to individual collectors increased with tree DBH and the convexity of the canopy surface. Compared to SO42--S and Cl- in throughfall, total NO3--N fluxes (0.17 - 4.03 kg N ha-1 wet season-1) were low and appeared to vary with small-scale changes in elevation. Geospatial technologies and remote sensing tools, such as LiDAR, are promising in the study of relationships between atmospheric deposition and topography (including vegetation), and in scaling-up estimates of atmospheric deposition to larger spatial scales. Understanding small-scale surface controls on atmospheric deposition has implications for different areas of research within geography, including modeling the spread of emerging infectious disease and assessing the effects of nitrogen cycling on native and invasive plant species composition.

Ozone dry deposition, an important tropospheric ozone sink, is expected to evolve with climate and land use, but coarse representation of ozone dry deposition in most large-scale atmospheric chemistry models hinders understanding of the influence of this sink on ozone air quality. Ozone uptake by stomata, injurious to plants, has been emphasized in the atmospheric chemistry community as the predominant terrestrial ozone depositional sink. However, there is an abundance of observational evidence from monitoring sites around the world suggesting that nonstomatal deposition processes (e.g., surface-mediated aqueous reactions on leaf cuticles, reactions with soil organic matter) are important ozone sinks. With observations from one of the longest ozone eddy covariance datasets available and a model hierarchy, I find substantial variations in nonstomatal ozone dry deposition, which is a non-negligible amount of the total ozone dry deposition, and identify the individual deposition processes driving observed variability. I pinpoint the responses of ozone pollution to changes in precursor emissions, climate, and ozone dry deposition at the beginning and end of the 21st century using a new version of the NOAA GFDL chemistry-climate model that more explicitly resolves deposition processes by leveraging the interactive biophysics of the land component of the model. My work highlights that under strong precursor emission controls there is a shift in the high ozone pollution season over northern mid-latitudes to a wintertime peak, and that wintertime ozone is sensitive to ozone dry deposition due to the long ozone lifetime. For both summer and winter, I find that neglecting variations in nonstomatal deposition and dependencies on environmental conditions may hinder accurate identification of the processes driving observed trends and variability in ozone pollution. In light of the sensitivity of ozone to dry deposition during winter, I identify a need for developing observational constraints on the wintertime depositional sink.

An ammonia emissions inventory discovered that 90% of the ammonia emitted from Pinellas, Hillsborough, and Polk counties, originated from the latter two counties. This finding is significant and suggests that a substantial portion of the ammonia deposited to Tampa Bay is transported with easterly air masses. Ammonia and ammonium concentrations at the coastal Gandy Bridge site were seasonally and diurnally consistent, but the rural Sydney site showed greater variability. It was determined that wind direction was the most influential parameter affecting the Gandy Bridge site, which supports the hypothesis that an advection of ammonia from the east is a major source of ammonia to the estuary. Sequential sampling of ammonium in wet deposition at the Gandy Bridge site confirmed that between 35% and 60% of the ammonium (CNH4) in rainfall is deposited to Tampa Bay during the initial 20% of precipitation (D) according to a power law CNH4=aD-b. Ammonium concentrations were predicted with an aqueous-phase accumulation model and a relationship between I, rainfall intensity in mm min-1 and (beta), scavenging rate in min-1 was shown as (beta) = 0.08I0.66. This algorithm will facilitate future modeling studies that explore the relationship between the wet deposition of ammonium and ammonia reduction strategies in Tampa Bay. The NOAA Buoy model accurately predicts sensible heat flux, and is an effective tool for estimating the offshore air/water exchange rates of ammonia over Tampa Bay. If near-shore vs. offshore meteorological measurements are used, the model under-predicts flux parameters by as much as 30% in the summer season. The model was "calibrated" to correct this deficiency. Bi-directional ammonia flux measurements during the fall and winter seasons resulted in an average flux rate of 96.2 (mu)g-NH3 m-2 d-1, indicating a net transfer from air to water. During the 2003 summer season, an average ammonia flux rate of -117.9 (mu)g-NH3 m-2 d-1 and a 32% reduction in the annual ammonia dry deposition rate to Tampa Bay was calculated. Wet deposition likely contributes to ammonia reemission from the estuary. These results indicate that volatilization of ammonia reduces the nitrogen burden available for biological synthesis in Tampa Bay.

The atmospheric transport of various substances from the continents to the oceans plays an important role in biogeochemical processes. Trace metals, iron in particular is of great interest as its availability regulates the growth of phytoplankton over large areas of the ocean. This dissertation focuses on examining and characterizing the factors that affect the solubility of trace metals in Miami and Barbados aerosols and precipitation, in particular species that could play a role in surface seawater biogeochemistry (Fe and trace metals such as Al, V, Cr, Mn, Cu, Co, Ni, Zn, As, Tl, Ba, Cd, Pb, Th, Ti, Zr, and REE's). To enable this study existing methods of colorimetric spectroscopic and inductively coupled plasma mass spectrometry analysis were improved and modified. This dissertation examines several issues related to source inputs: 1.) Are single spot sources within the North African dust source distinguishable after long transport by their bulk metal composition and thus important in the characteristics of individual mineral dust samples? 2.) What is the temporal variability and controlling factors in trace metal solubility in trade wind aerosols collected over Barbados? 3.) Which factors control the observed trend of speciation and increasing iron solubility in decreasing aerosol loading? Additionally a kinetic model of species specific iron (II) to iron(III) oxidation kinetics in NaCl Brines was conducted at nano-molar levels. This study greatly expands the ability to predict rates of iron oxidation at concentrations closer to those observed in natural systems.

Thesis (Ph. D.) in Ecology and Environmental Science--University of Maine, 2003. / Includes vita. Includes bibliographical references (leaves 137-163).

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Abstract The thesis consists of regional forest condition studies, using different biomonitors. Heavy metal deposition was investigated in 1985–2000 on the basis of the heavy metal concentrations (As, Cd, Cr, Cu, Fe, Hg, Ni, Pb, V, Zn) in mosses in Finland. A comparison on the suitability of mosses, epiphytic lichens and pine bark as biomonitors of heavy metals was also carried. Bark was also used to study the dispersal of emissions from the Kola Peninsula into northern Finland. The occurrence of green algae on conifers in Finland was investigated in 1985 and 1995. Regional and temporal differences were found in the heavy metal concentrations of mosses in Finland. The concentrations of most metals were the highest in southern Finland, and they decreased towards the north. Some of the major emission source had a noticeable effect on the Cu, Ni and Cr concentrations of mosses in the surroundings of the emission sources. The Pb, Cd and V concentrations decreased the most during the study period. Mosses, lichens and bark gave a relatively similar result for heavy metal deposition in Finland. However, the comparisons indicated that mosses are better suited as biomonitors for regional surveys than epiphytic lichens, because the regional differences in heavy metal deposition were more readily reflected by concentrations in mosses than in lichens. Bark is relatively unsuitable for regional surveys due to the small range of variation in the concentrations. Emissions from the Kola Peninsula had a clear effect on the sulphur and heavy metal concentrations of pine bark. The concentrations in bark were at very high levels close to the smelters, but they rapidly decreased on moving towards the west. The effects of emissions were still clearly visible in north-eastern Lapland. There was strong increase in the abundance of green algae on conifers in southern and central Finland during the period 1985–1995. The increase is probably due to following factors: climate warming, and an increase in nitrogen and a decrease in sulphur in their habitats. Half of each biomonitor sample collected in the surveys has been stored in the specimen bank at Paljakka. The storage of samples offers advantages for monitoring purposes. The availability of long-term sample series makes it possible to construct retrospective time series of the pollutants. The specimen bank is to be further developed in the future by establishing a reputation as a storage facility for samples related to forest ecosystems.

Thesis (M.S.) -- Mississippi State University. Department of Geosciences. / Title from title screen. Includes bibliographical references.

Indiana University-Purdue University Indianapolis (IUPUI) / Mercury (Hg) has proven to be a risk to the public, mainly through the consumption of fish. Because of this, many fish consumption advisories have been issued in Indiana. Although much is known about the global cycle of mercury, little is known about how local and regional emission sources of mercury impact local and regional mercury cycling. This study’s objective was to determine the scope of mercury concentration in central Indiana by using a broad grid of soil mercury measurements. Sampling was designed to capture the net retained mercury content in soils, and to determine whether spatial patterns in exist in soil mercury contents that could be related to emission sources of mercury and post-emission transport patterns from wind. Results from this study revealed significant differences in mercury concentrations for soils in central Indiana. The core of the study area, concentrated in the urban area of Indianapolis, exhibited soil mercury contents that were 20 times higher than values in the outskirts of the study area. The spatial pattern resembled a bulls-eye shape centered on Indianapolis, and with comparison to the reported Hg emission from local sources, including a coal-fired power plant, indicates a strong regional deposition signal linked to those emission sources but marked by wind-driven transport to the northeast. This effect of local emission sources resulting in local deposition indicates that limiting mercury emissions will have a net beneficial impact on local environmental quality and human health.

Surface deposition is an important sink for tropospheric ozone. The rate of ozone deposition may be measured by measuring the downward flux of ozone in the atmospheric surface-layer. This thesis presents eddy correlation measurements of ozone fluxes, taken on eight days in August, 1994, at a grassland site located in the Lower Fraser Valley of British Columbia. Surface resistances to ozone deposition were calculated from the flux measurements. Much of the variability in measured surface resistances was found to be attributable to variations in ambient light levels and in the degree of moisture stress at the site. Measurements of surface resistance from this site agreed quite well with other measurements of ozone deposition to grassland surfaces. Measured surface resistances were compared to surface resistances calculated using the Wesely (1989) parameterization (W89) for surface resistance. W89 underestimated surface resistance, particularly in the mid afternoon and early evening. This was attributed to the model's neglect of the effects of water stress on stomatal resistance, as well as to a low value for resistance to ground surface deposition in the model. The eddy correlation fluxes were compared to ozone fluxes derived using an assumption of cospectral similarity between ozone and heat flux and to ozone fluxes measured using the variance method and the gradient method. The cospectral similarity method worked well and allowed a considerable relaxation of the sampling speed requirements of the eddy correlation method. The variance method produced biased flux measurements due to high frequency noise from the ozone sensor. Flux measurements using the gradient method had a great deal of scatter, due to inaccuracies in the measurement of gradients.