Designing for Air Pollution Control

This paper was one of several presented at the Workshop on Air Pollution Control in Portland, Oregon, on May 6, 1968. The Workshop was sponsored by the Manufacturing Chemists Association and the Chemical Industry Council of the Pacific Northwest in cooperation with the Association of Oregon Industries, Association of Washington Industries, and the Environmental Committee of the Portland Chamber of Commerce. While many of the papers were of localized interest, this paper speaks to anyone designing air pollution control systems.     

Characterization of the lignin signature in Lake Mead,NV, sediment: comparison of on-line flash chemopyrolysis (600°C) and off-line chemolysis (250°C)

The distribution of lignin in sediment is a useful tool for tracing the transport of land-derived organic matter in an aquatic environment. Tetramethylammonium hydroxide (TMAH) flash chemopyrolysis, or chemolysis followed by GC–MS analysis can be used for evaluating the origin of organic carbon in sediments. TMAH chemopyrolysis or chemolysis of organic matter produces a myriad of semi-volatile products. Among these products are methylated phenols which are an indirect measure of lignin in sediment. In this study, total organic carbon, elemental carbon, and lignin were measured in Lake Mead sediments. This study indicates that terrestrial runoff makes a contribution to Lake Mead sediments, and that this contribution is most apparent in sediment that is close to the Las Vegas Wash. Two chemolysis methods (on-line and off-line) were examined and compared for detection of lignin phenols. The results from these sediment cores indicate that comparable results can be obtained from the two approaches, although detection levels are significantly lower for the off-line approach.     

Economics at the fringe: Non-market valuation studies and their role in land use plans in the United States

Over the past fifty years, economists have developed methods for estimating the public benefits of green spaces, allowing such information to be incorporated into land use planning. But the extent to which it is ever used is unclear. This paper reviews the literature on public values for lands on urban outskirts, not just to survey their methods or empirical findings, but to evaluate the role they have played – or have the potential to play – in actual US land use plans.Based on interviews with authors and representatives of land trusts and governments, it appears that academic work has had a mixed reception in the policy world. Reasons include a lack of interest in making academic work accessible to policy makers, emphasizing revealed preference methods which ignore important non-use values, and emphasizing average values over distributions of values. Nevertheless, some success stories illustrate how such information can play a role in the design of conservation policies.     

Marsh surface sediment deposition and the role of tidal creeks: Implications for created and managed coastal marshes

The need to understand the processes contributing to marsh sedimentation has become more urgent with the recent recognition of the role of tidal marshes as sea defences, as well as the many restoration efforts currently under way. This study was designed to build upon previous sedimentation work at Scolt Head Island by Combining techniques for measuring short-term sedimentation, with detailed assessment of hydroperiod, previously used only in comparison with longer-term accretion measurements or in micro-tidal systems. Measurements of water level, sediment deposition (at various distances from the creek margin) and suspended sediment concentration (SSC) (creek margin and an interior site) were made at Hut Marsh over three sequential over-marsh tides during May 1994. Sediment trap data show a significant trend of declining sediment deposition away from the creek when data from all three tides are combined. All tides show higher SSC on the flood tide than on the ebb tide at the creek margin location. There is little difference in flood and ebb SSCs at the interior site. An order of magnitude decrease in sediment deposition within 20 m on the creek shows the rapidity with which sediment is deposited on these marshes. Higher tides influence both the magnitude and pattern of marsh surface sediment deposition. Increased creek velocities on higher tides provide more potential for resuspension within the creek and increase the supply of sediment to the marsh surface. This study suggests that the design of tidal creeks may be essential for the development of sustainable coastal marshes in restoration projects.     

A deterministic approach to evaluate and implement monitored natural attenuation for chlorinated solvents

A US EPA directive and related technical protocol outline the information needed to determine if monitored natural attenuation (MNA) for chlorinated solvents is a suitable remedy for a site. For some sites, conditions such as complex hydrology or perturbation of the contaminant plume caused by an existing remediation technology (e.g., pump‐and‐treat) make evaluation of MNA using only field data difficult. In these cases, a deterministic approach using reactive transport modeling can provide a technical basis to estimate how the plume will change and whether it can be expected to stabilize in the future and meet remediation goals. This type of approach was applied at the Petro‐Processors Inc. Brooklawn site near Baton Rouge, Louisiana, to evaluate and implement MNA. This site consists of a multicomponent nonaqueous‐phase source area creating a dissolved groundwater contamination plume in alluvial material near the Mississippi River. The hydraulic gradient of the groundwater varies seasonally with changes in the river stage. Due to the transient nature of the hydraulic gradient and the impact of a hydraulic containment system operated at the site for six years, direct field measurements could not be used to estimate natural attenuation processes. Reactive transport of contaminants were modeled using the RT3D code to estimate whether MNA has the potential to meet the site‐specific remediation goals and the requirements of the US EPA Office of Solid Waste and Emergency Response Directive 9200.4‐17P. Modeling results were incorporated into the long‐term monitoring plan as a basis for evaluating the effectiveness of the MNA remedy. As part of the long‐term monitoring plan, monitoring data will be compared to predictive simulation results to evaluate whether the plume is changing over time as predicted and can be expected to stabilize and meet remediation goals. This deterministic approach was used to support acceptance of MNA as a remedy. © 2007 Wiley Periodicals, Inc.     

A high performance liquid chromatography method for determination of gas-phase hydrogen peroxide in ambient air using Fenton's chemistry

A new method for determination of hydrogen peroxide in atmospheric samples is described. Cryogenically collected H2O2 is reacted with sodium salicylate in the presence of Fe(2+) to produce dihydroxybenzoate, which is separated from the reaction mixture by high performance liquid chromatography and detected by UV absorption. Measurements of atmospheric H2O2 were conducted in Las Vegas, NV from June 1999 to December 1999 to evaluate and characterize the method. Measured mixing ratios of H2O2 (there were also non-detects) ranged from 0.012 to 2.74 ppbv, with expected correlations to primary gaseous pollutants and strong seasonal variation consistent with a photochemically derived species. It was concluded that the method is easy to use and has sufficient sensitivity and selectivity to be useful in atmospheric monitoring.     

Assessing the local economic impacts of land protection

Land protection, whether public or private, is often controversial at the local level because residents worry about lost economic activity. We used panel data and a quasi-experimental impact-evaluation approach to determine how key economic indicators were related to the percentage of land protected. Specifically, we estimated the impacts of public and private land protection based on local area employment and housing permits data from 5 periods spanning 1990–2015 for all major towns and cities in New England. To generate rigorous impact estimates, we modeled economic outcomes as a function of the percentage of land protected in the prior period, conditional on town fixed effects, metro-region trends, and controls for period and neighboring protection. Contrary to narratives that conservation depresses economic growth, land protection was associated with a modest increase in the number of people employed and in the labor force and did not affect new housing permits, population, or median income. Public and private protection led to different patterns of positive employment impacts at distances close to and far from cities, indicating the importance of investing in both types of land protection to increase local opportunities. The greatest magnitude of employment impacts was due to protection in more rural areas, where opportunities for both visitation and amenity-related economic growth may be greatest. Overall, we provide novel evidence that land protection can be compatible with local economic growth and illustrate a method that can be broadly applied to assess the net economic impacts of protection.