Publications by authors named "Deb Niemeier"

14 Publications

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Are stay-at-home orders more difficult to follow for low-income groups?

J Transp Geogr 2020 Dec 30;89:102894. Epub 2020 Oct 30.

Department of Civil and Environmental Engineering, University of Maryland, College Park, MD 20742, USA.

In response to the COVID-19 pandemic, a growing number of states, counties and cities in the United States issued mandatory stay-at-home orders as part of their efforts to slow down the spread of the virus. We argue that the consequences of this one-size-fits-all order will be differentially distributed among economic groups. In this paper, we examine social distance behavior changes for lower income populations. We conduct a comparative analysis of responses between lower-income and upper-income groups and assess their relative exposure to COVID-19 risks. Using a difference-in-difference-in-differences analysis of 3140 counties, we find social distance policy effect on the lower-income group is smaller than that of the upper-income group, by as much as 46% to 54%. Our explorations of the mechanisms behind the disparate effects suggest that for the work-related trips the stay-at-home orders do not significantly reduce low income work trips and this result is statistically significant. That is, the share of essential business defined by stay-at-home orders is significantly negatively correlated with income at county level. In the non-work-related trips, we find that both the lower-income and upper-income groups reduced visits to retail, recreation, grocery, and pharmacy visits after the stay-at-home order, with the upper-income group reducing trips more compared to lower-income group.
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http://dx.doi.org/10.1016/j.jtrangeo.2020.102894DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7832451PMC
December 2020

Managing high fiber food waste for the cultivation of black soldier fly larvae.

NPJ Sci Food 2019 2;3:15. Epub 2019 Sep 2.

1Department of Biological and Agricultural Engineering, University of California, One Shields Avenue, Davis, CA 95616 USA.

Increases in global human population are leading to increasing demands for food production and waste management. Insect biomass is a sustainable alternative to traditional animal feeds when insects are produced on lignocellulosic by-products. Resources high in lignocellulose have high carbon to nitrogen ratios and require nitrogen supplementation to accelerate bioconversion. Here we report on studies that examine the influence of nitrogen supplementation of almond hull-based feedstocks on black soldier fly larvae ( L.) cultivation and composition. Decreasing carbon to nitrogen ratio from 49 to 16 increased larvae harvest dry weight, specific larvae growth, and yield by 36%, 31%, and 51%, respectively. However, the decrease in carbon to nitrogen ratio decreased larvae methionine and cysteine contents by 11% and 13%, respectively. The findings demonstrate that carbon to nitrogen ratio can be managed to enhance bioconversion of lignocellulose to larvae, but that this management approach can reduce larvae amino acid content.
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http://dx.doi.org/10.1038/s41538-019-0047-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6718667PMC
September 2019

Validating and Refining EPA's Traffic Exposure Screening Measure.

Int J Environ Res Public Health 2018 12 20;16(1). Epub 2018 Dec 20.

Department of Civil and Environmental Engineering, University of California, Davis, CA 95616, USA.

Exposure to high air pollutant concentrations results in significant health risks. Many communities of color and low-income communities face disproportionately higher levels of air pollution exposure. Environmental justice (EJ) screening tools play a critical role in focusing early attention on areas with a high likelihood of disparate health impacts. In 2015, the United States Environmental Protection Agency (US EPA) released EJScreen, a screening tool with indicators of a range of pollution burdens across the US. However, little is known about the accuracy of the screening estimates of pollution exposure. This study compares EJScreen's traffic proximity air quality metric to dispersion modeling results. Using the area around the Houston Ship Channel, we conduct fine-grained air pollution dispersion modeling to evaluate how closely EJScreen's indicator approximates estimated roadway air pollution concentrations. We find low correlation between modeled concentrations and the EJScreen roadway air pollution indicator. We extend EJScreen's roadway air pollution screening method in three ways: (1) using a smaller unit of analysis, (2) accounting for the length of each road segment, and (3) accounting for wind direction. Using the Houston region, we use two of the methods and show that the proposed extensions provide a more accurate transportation air pollution screening assessment at the regional and local level.
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http://dx.doi.org/10.3390/ijerph16010003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6338909PMC
December 2018

Feeding and lighting practices on small-scale extensive pastured poultry commercial farms in the United States.

Poult Sci 2019 Feb;98(2):785-788

UC Davis College of Engineering, Department of Civil & Environmental Engineering, One Shields Ave, Davis, CA 95616, USA.

As commercial free-range and pastured poultry production has gained increased popularity in the United States in recent years, there is a greater need to understand basic husbandry practices including feeding and lighting practices. Because husbandry practices vary greatly between individual commercial pastured poultry and free-range operations, gaining knowledge across a wide cross-section of producers is necessary to better understand current practices. Specifically, because feed is considered the most expensive part of poultry production with respect to operating cost, in collaboration with the American Pastured Poultry Producers Association, an on-line survey of commercial free-range and pastured poultry producers was conducted aimed primarily at evaluating feeding and lighting practices. Data were collected from 14 commercial pastured (n = 13) and free-range (n = 1) producers (6 broiler, 1 layer, and 7 broiler/layer facilities) across 9 U.S. states. Results showed that these operations most commonly use Cornish Cross for broiler production and ISA Brown and Australorp for egg production. Only 1 of the 14 farms calculates feed conversion ratio on a monthly basis. Estimates of Hen Month Egg Production (HMEP) resulted in HMEP percentages that were over 100% in 6 of the 7 farms that provided data. 5 of the 7 farms that have layers used supplemental lighting but do not use a lux meter. These lack of data reflect an important challenge with this segment of the poultry industry. Extension based outreach focused on enabling data collection and record-keeping and analysis are necessary. Despite its small sample size, this study's results provide some valuable insights with respect to feeding equipment and the current state of data collection for this segment of the poultry industry.
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http://dx.doi.org/10.3382/ps/pey470DOI Listing
February 2019

Cultivation of black soldier fly larvae on almond byproducts: impacts of aeration and moisture on larvae growth and composition.

J Sci Food Agric 2018 Dec 29;98(15):5893-5900. Epub 2018 Aug 29.

Department of Biological and Agricultural Engineering, University of California, Davis, CA, USA.

Background: The increasing production of almonds worldwide has resulted in the significant generation of byproduct streams that require end uses. One potential use for byproducts is for cultivation of additional food sources including insects. Studies were performed to determine if black soldier fly larvae (Hermetia illucens L.) could be cultivated on almond byproducts (hulls and shells) and to examine the effect of aeration and moisture on larvae growth and hull composition.

Results: Increasing aeration from 0.04 to 0.36 mL min g dry weight tripled the harvest weight of larvae and increased larvae yield by a factor of five. Larvae calcium content increased by 18% with an increase in aeration from 0.04 to 0.95 mL min g dry weight . Moisture content also affected harvest dry weight and yield; increasing moisture content from 480 g kg (wet basis) to 680 g kg increased harvest weight by 56% and yield by a factor of 2. Variables did not affect larvae methionine and cysteine content. Low moisture content and aeration rate yielded an environment that supported microbial consumption of hulls over larvae consumption and growth.

Conclusions: The results demonstrate that almond hulls are a suitable feedstock for larvae production under controlled management of moisture content and aeration. © 2018 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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http://dx.doi.org/10.1002/jsfa.9252DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6282619PMC
December 2018

Building a Wall on the Imaginary Line.

Authors:
Deb Niemeier

Environ Sci Technol 2017 02 9;51(3):1053. Epub 2017 Jan 9.

Department of Civil and Environmental Engineering, University of California , Davis, California 95616, United States.

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http://dx.doi.org/10.1021/acs.est.6b05220DOI Listing
February 2017

Descriptive survey and Salmonella surveillance of pastured poultry layer farms in California.

Poult Sci 2017 Apr;96(4):957-965

UC Davis School of Veterinary Medicine, Department of Population Health and Reproduction, One Shields Ave, Davis, CA 95616, USA.

While pasture-raised poultry comprises a small portion of the commercial poultry industry in North America, these alternative rearing systems have become increasingly popular. As such, it is critical to improve our understanding of husbandry practices and prevalence of zoonotic and epizoonotic diseases in these systems. This research reviews the results of a survey sent to 82 commercial pastured poultry farms in California. While the survey response was low (13.4%), it was enhanced by detailed in-person interviews and farm visits. In addition, we conducted drag swabs for Salmonella Enteritidis. On average, farms utilized 12.3% of their total farmland for pastured poultry operations, which often coexisted with other livestock (45%), touch crops (27%), and non-touch crops (45%). While the mean (44.6 sq. ft./hen) and median (22.2 sq. ft./hen) pasture stocking densities were within auditing guidelines, the mean (1.2 sq. ft./hen) and median (0.5 sq. ft./hen) coop stocking densities were below the pending USDA (2016) guidelines recommended in 7 CFR Part 205. Drag swab results showed the presence of Salmonella Enteritidis (SE) in the environment of one of the 11 farms (9.1%). In addition, Salmonella Pullorum (SP) whole blood agglutination tests were used to understand the prevalence of Salmonella spp. in laying hens within the studied farms. Results showed the presence of antibodies in flocks at six of the seven non-SE vaccinated farms, with a mean on-farm prevalence of 25.6% in laying hens. Logistic regression was used to determine risk factors for Group D Salmonella exposure in non-vaccinated flocks, using the SP blood agglutination data as the dependent variable and the survey questions as the independent variables. Statistically significant (P < 0.05) risk factors included exposed wire floors and flock size. These results improve our understanding of Salmonella prevalence and husbandry practices on commercial pastured poultry farms in California.
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http://dx.doi.org/10.3382/ps/pew360DOI Listing
April 2017

School locations and traffic emissions—environmental (in)justice findings using a new screening method.

Int J Environ Res Public Health 2015 Feb 11;12(2):2009-25. Epub 2015 Feb 11.

Department of Civil and Environmental Engineering, University of California Davis, One Shields Avenue, Davis, CA 95616, USA.

It has been shown that the location of schools near heavily trafficked roads can have detrimental effects on the health of children attending those schools. It is therefore desirable to screen both existing school locations and potential new school sites to assess either the need for remedial measures or suitability for the intended use. Current screening tools and public guidance on school siting are either too coarse in their spatial resolution for assessing individual sites or are highly resource intensive in their execution (e.g., through dispersion modeling). We propose a new method to help bridge the gap between these two approaches. Using this method, we also examine the public K-12 schools in the Sacramento Area Council of Governments Region, California (USA) from an environmental justice perspective. We find that PM2.5 emissions from road traffic affecting a school site are significantly positively correlated with the following metrics: percent share of Black, Hispanic and multi-ethnic students, percent share of students eligible for subsidized meals. The emissions metric correlates negatively with the schools' Academic Performance Index, the share of White students and average parental education levels. Our PM2.5 metric also correlates with the traffic related, census tract level screening indicators from the California Communities Environmental Health Screening Tool and the tool's tract level rate of asthma related emergency department visits.
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http://dx.doi.org/10.3390/ijerph120202009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4344707PMC
February 2015

How to transform the practice of engineering to meet global health needs.

Science 2014 Sep;345(6202):1287-90

Department of Bioengineering, Rice University, Houston, TX 77005, USA.

More of the world's population has access to cell phones than to basic sanitation facilities, a gap that can only be closed if the engineering and international aid communities adopt new approaches to design for scarcity and scalability.
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http://dx.doi.org/10.1126/science.1257085DOI Listing
September 2014

Spatial assignment of emissions using a new locomotive emissions model.

Environ Sci Technol 2011 Jul 24;45(13):5846-52. Epub 2011 May 24.

Department of Civil and Environmental Engineering, University of California, One Shields Avenue, Davis, California 95616, United States.

Estimates of fuel use and air pollutant emissions from freight rail currently rely highly on aggregate methods and largely obsolete data which offer little insight into contemporary air quality problems. Because the freight industry is for the most part privately held and data are closely guarded for competitive reasons, the challenge is to produce robust estimates using current reporting requirements, while accurately portraying the spatial nature of freight rail impacts. This research presents a new spatially resolved model for estimating air pollutant emissions (hydrocarbons, carbon monoxide, nitrogen oxides, particulate matter less than 10 μm in diameter, sulfur dioxide, and carbon dioxide) from locomotives. Emission estimates are based on track segment level data including track grade, type of train traffic (bulk, intermodal, or manifest) and the local locomotive fleet (EPA tier certification level and fuel efficiency). We model the California Class I freight rail system and compare our results to regional estimates from the California Air Resources Board and to estimates following U.S. Environmental Protection Agency guidance. We find that our results vary considerably from the other methods depending on the region or corridor analyzed. We also find large differences in fuel and emission intensity for individual rail corridors.
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http://dx.doi.org/10.1021/es103660rDOI Listing
July 2011

Future sustainability forecasting by exchange markets: basic theory and an application.

Environ Sci Technol 2010 Dec 8;44(23):9134-42. Epub 2010 Nov 8.

University of California, Davis, The Department of Civil and Environmental Engineering, One Shields Avenue, Davis, California 95616, United States.

Setting sustainability targets and evaluating systems progress are of great importance nowadays due to threats to the human society, to economic development and to ecosystems, posed by unsustainable human activities. This research establishes a probabilistic theoretical approach based on market expectations reflected in prices of publicly traded securities to estimate the time horizon until the appearance of new technologies related to replacement of nonrenewable resources, for example, crude oil and oil products. To assess time T when technological innovations are likely to appear, we apply advanced pricing equations, based on a stochastic discount factor to those traded securities whose future cash flows critically depend on appearance of such innovations. In a simple approximation of the proposed approach applied to replacement of crude oil and oil products, we obtain T ≈ (P(0)(oil)/C(0))·ln (Δ·P(0)(oil)/P(0)(alt)), where P(0)(oil) and P(0)(alt) are the current aggregate market capitalizations of oil and alternative-energy companies, C(0) is the annual aggregate dividends that oil companies pay to their shareholders at the present, and Δ is the fraction of the oil (oil products) replaced at time T. This formula gives T ≈ 131 years for replacement of gasoline and diesel. The proposed market-expectations approach may allow policymakers to effectively develop policies and plan for long-term changes.
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http://dx.doi.org/10.1021/es100730qDOI Listing
December 2010

Near-roadway air quality: synthesizing the findings from real-world data.

Environ Sci Technol 2010 Jul;44(14):5334-44

U.C. Davis-Caltrans Air Quality Project, Department of Civil and Environmental Engineering, University of California, Davis, California 95616, USA.

Despite increasing regulatory attention and literature linking roadside air pollution to health outcomes, studies on near roadway air quality have not yet been well synthesized. We employ data collected from 1978 as reported in 41 roadside monitoring studies, encompassing more than 700 air pollutant concentration measurements, published as of June 2008. Two types of normalization, background and edge-of-road, were applied to the observed concentrations. Local regression models were specified to the concentration-distance relationship and analysis of variance was used to determine the statistical significance of trends. Using an edge-of-road normalization, almost all pollutants decay to background by 115-570 m from the edge of road; using the more standard background normalization, almost all pollutants decay to background by 160-570 m from the edge of road. Differences between the normalization methods arose due to the likely bias inherent in background normalization, since some reported background values tend to underpredict (be lower than) actual background. Changes in pollutant concentrations with increasing distance from the road fell into one of three groups: at least a 50% decrease in peak/edge-of-road concentration by 150 m, followed by consistent but gradual decay toward background (e.g., carbon monoxide, some ultrafine particulate matter number concentrations); consistent decay or change over the entire distance range (e.g., benzene, nitrogen dioxide); or no trend with distance (e.g., particulate matter mass concentrations).
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http://dx.doi.org/10.1021/es100008xDOI Listing
July 2010

A critical review of the effectiveness of I/M programs for monitoring PM emissions from heavy duty vehicles.

Environ Sci Technol 2008 Nov;42(21):7856-65

Department of Civil and Environmental Engineering, University of California, One Shields Ave., Davis, CA 95616, USA.

Heavy-duty vehicles (HDV) are estimated to contribute up to 36% of particulate matter (PM) emissions in urban areas. In response, many agencies have established HDV inspection and maintenance (I/M) programs designed to target and repair vehicles with excess emissions. In this review, we conduct an international comparison of legislative context and HDV I/M program characteristics across Europe, North America, and Australia. The results of this analysis show that HDV-I/M programs vary greatly in terms of the ways in which testing is organized, for example, roadside versus periodic testing, whether the fleet is self-tested, and how nonfleet and age exemptions are handled. We also show how the I/M test criteria have changed little in the last 15 years while regulations for new heavy-duty diesel engine emissions have become increasingly stringent. In the U.S., HDV engine PM emissions limits were reduced by a factor of 26 between 1997 and 2007. Most I/M programs have continued to test according to EPA (and often with state legislative confirmation) guidance procedures having cut-points established in 1992. An analysis of data from Washington State show that only a minority of post-1997 vehicles actually exceeds the detection levels of the free-acceleration smoke-opacity test procedures, with the result that malfunctions of these vehicles may not actually be detected. From our review, it is clear that even with the potential adoption of new technologies and a more systematic and efficient framework for HDV-I/M, more research must be conducted in the efficacies of periodic versus roadside testing (and location selection), the use of evaluation methods like fail rates and opacity distributions, and finally, in development of better methods for identifying excess emissions with sensors and duty cycles.
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http://dx.doi.org/10.1021/es8001794DOI Listing
November 2008

CO2-forced climate and vegetation instability during Late Paleozoic deglaciation.

Science 2007 Jan;315(5808):87-91

Department of Geology, University of California, Davis, CA 95616, USA.

The late Paleozoic deglaciation is the vegetated Earth's only recorded icehouse-to-greenhouse transition, yet the climate dynamics remain enigmatic. By using the stable isotopic compositions of soil-formed minerals, fossil-plant matter, and shallow-water brachiopods, we estimated atmospheric partial pressure of carbon dioxide (pCO2) and tropical marine surface temperatures during this climate transition. Comparison to southern Gondwanan glacial records documents covariance between inferred shifts in pCO2, temperature, and ice volume consistent with greenhouse gas forcing of climate. Major restructuring of paleotropical flora in western Euramerica occurred in step with climate and pCO2 shifts, illustrating the biotic impact associated with past CO2-forced turnover to a permanent ice-free world.
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http://dx.doi.org/10.1126/science.1134207DOI Listing
January 2007