Valerie Cover Garcia

Valerie Cover Garcia
United States Environmental Protection Agency | US EPA · Office of Research and Development

PhD Forestry

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34
Publications
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281
Citations

Publications

Publications (34)
Article
Eutrophication and excessive algal growth pose a threat on aquatic organisms and the health of the public, environment, and the economy. Understanding what drives excessive algal growth can inform mitigation measures and aid in advance planning to minimize impacts. We demonstrate how simulated data from weather, hydrological, and agroecosystem nume...
Article
Full-text available
Regional-scale air pollution models are routinely being used worldwide for research, forecasting air quality, and regulatory purposes. It is well recognized that there are both reducible (systematic) and irreducible (unsystematic) errors in the meteorology–atmospheric-chemistry modeling systems. The inherent (random) uncertainty stems from our inab...
Chapter
We used linked and coupled physical models to identify relationships among environmental variables across multiple sources and pathways to examine the impact of nitrogen loadings on chlorophyll α concentrations.
Article
Full-text available
This study demonstrates the value of a coupled chemical transport modeling system for investigating groundwater nitrate contamination responses associated with nitrogen (N) fertilizer application and increased corn production. The coupled Community Multiscale Air Quality Bidirectional and Environmental Policy Integrated Climate modeling system inco...
Chapter
Attributing nitrogen (N) in the environment to emissions from agricultural management practices is difficult because of the complex and inter-related chemical and biological reactions associated with N and its cascading effects across land, air and water. Such analyses are critical, however, in understanding the benefits and disbenefits associated...
Article
Full-text available
Unlabelled: Despite observed geographic and temporal variation in particulate matter (PM)-related health morbidities, only a small number of epidemiologic studies have evaluated the relation between PM2.5 chemical constituents and respiratory disease. Most assessments are limited by inadequate spatial and temporal resolution of ambient PM measurem...
Article
Full-text available
Exposure studies rely on detailed characterization of air quality, either from sparsely located routine ambient monitors or from central monitoring sites that may lack spatial representativeness. Alternatively, some studies use models of various complexities to characterize local-scale air quality, but often with poor representation of background c...
Chapter
The results from epidemiology time series models that relate air quality to human health are often used in determining the need for emission controls in the United States. These epidemiology models, however, can be sensitive to collinearity among co-variates, potentially magnifying biases in the parameter estimates caused by exposure misclassificat...
Article
Epidemiological analyses of air quality often estimate human exposure from ambient monitoring data, potentially leading to exposure misclassification and subsequent bias in estimated health risks. To investigate this, we conducted a case-crossover study of summertime ambient ozone and fine particulate matter (PM2.5) levels and daily respiratory hos...
Article
To date, only a limited number of studies have examined the impact of ambient pollutant policy on respiratory morbidities. This accountability study examined the effect of a regional pollution control policy, namely, the US Environmental Protection Agency's (EPA) nitrogen oxides (NO(x)) Budget Trading Program (NBP), on respiratory health in New Yor...
Article
Full-text available
Nitrogen oxides (NOx) are important components of ambient and indoor air pollution and are emitted from a range of combustion sources, including on-road mobile sources, electric power generators, and non-road mobile sources. While anthropogenic sources dominate, NOx is also formed by lightning strikes and wildland fires and is also emitted by soil....
Conference Paper
The ability of four (4) enhancements of gridded PM2.5 concentrations derived from observations and air quality models to detect the relative risk of long-term exposure to PM2.5 are evaluated with a simulation study. The four enhancements include nearest-neighbor (NN or central monitor), ordinary kriging (OK), FUSED (bias-adjusted model output), and...
Chapter
Full-text available
The Clean Air Act (CAA) requires that the United States (U.S.) Environmental Protection Agency (EPA) set National Ambient Air Quality Standards (NAAQS) for pollutants considered harmful to human health and the environment. Previous research has shown that high ambient ozone levels are harmful to human health (e.g., Bell ML, Dominici F, Samet JM, Ep...
Article
Nitrogen oxides (NOX) are important components of ambient and indoor air pollution and are emitted from a range of combustion sources, including on-road mobile sources, electric power generators, and non-road mobile sources. While anthropogenic sources dominate, NOX is also formed by lightning and wildland fires and is emitted by soil. Reduced nitr...
Conference Paper
Background: Few studies have examined the impacts of federal environmental policy on outdoor pollutants and health outcomes. The objective of this accountability study was to examine the health impact of the NOx State Implementation Plans (NOx SIP), a US Environmental Protection Agency mandate to reduce transport of nitrogen oxides (NOx) from neigh...
Article
Full-text available
We used wavelet analysis and generalized additive models (GAM) to study timescale effects in the acute association between mortality and air-pollution. Daily averages of measured NO2 concentrations in the metropolitan Paris area are used as indicators of human exposure to urban air pollution from 2000 to 2004. The NO2 time series was decomposed wit...
Article
Full-text available
Human exposure to air pollution transported from the Midwest is evaluated in eight New York State (NYS) regions over ten summers (1997 - 2006) for association with respiratory-related hospital admissions. Days when pollution is transported into the Northeastern United States (U. S.) were identified by using back-trajectories from the eight regions....
Conference Paper
Detailed, time-varying spatial fields of air contaminant concentrations are valuable to public health professionals seeking to identify relationships between human health and ambient air quality, and policy makers interested in assessing compliance with air quality regulations. In this paper PM25 fields are created from a linear model that predicts...
Article
The regulatory community is increasingly recognizing the importance of addressing.accountability in its program assessments. In this article, we propose a system of metrics (predictions) and indicators (results) that could be adopted to assess the impact of CAIR, and suggest approaches for discerning a subtle signal of change in emissions embedded...
Article
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Air quality surfaces representing pollutant concentrations across space and time are needed for many applications, including tracking trends and relating air quality to human and ecosystem health. The spatial and temporal characteristics of these surfaces may reveal new information about the associations between emissions, pollution levels, and hum...
Article
In its mission to protect human health and the environment, the United States (U.S.) Environmental Protection Agency (EPA) implemented the NOx Budget Trading Program (NBP) to reduce the emissions of nitrogen oxides (NOx) in the Eastern U.S., with the intent of reducing ambient concentrations of both NOx and the secondarily-formed ozone chemicals. T...
Article
Several studies have demonstrated that an accurate assessment of temporal and spatial variations in ambient concentrations is critical for the interpretation of time-series epidemiology studies. The immediate solution is to apply spatial interpolation techniques to the available monitoring data to provide air quality information between monitoring...
Conference Paper
Full-text available
The Hierarchical Bayesian space-time Modeling System (HBM) incorporates ambient (outdoor) air quality (air pollution concentration) data from EPA-specified Federal Reference Method (FRM) monitors and retrospective air quality modeling data from the Community Multiscale Air Quality (CMAQ) computer model into a single estimated pollution concentratio...
Chapter
Full-text available
This paper presents three simple techniques for fusing observations and numerical model predictions. The techniques rely on model/observation bias being considered either as error free, or containing some uncertainty, the latter mitigated with a Kalman filter approach or a spatial smoothing method. The fusion techniques are applied to the daily max...
Article
Advancements in remote sensing over the past decade have been recognized by governments around the world and led to the development of the international Global Earth Observation System of Systems 10-Year Implementation Plan. The plan for the U.S. contribution to GEOSS has been put forth in The Strategic Plan for the U.S. Integrated Earth Observatio...
Article
Full-text available
Keywords: headwaters streams, GIS, LIDAR, topographic maps, stream extraction, stream maps. Thesis (M.S.)--North Carolina State University. Includes bibliographical references. Includes vita.

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