Abstract Evaluation of wetland extent and changes in extent is a foundation of many wetland monitoring and assessment programs. Probabilistic sampling and mapping provides a cost‐effective alternative to comprehensive mapping for large geographic areas. One unresolved challenge for probabilistic or design‐based approaches is how best to monitor both status (e.g., extent at a single point in time) and trends (e.g., changes in extent over time) within a single monitoring program. Existing wetland status and trends (S&T) monitoring programs employ fixed sampling locations; however, theoretical evaluation and limited implementation in other landscape monitoring areas suggest that alternative designs could increase statistical efficiency and overall accuracy. In particular, designs that employ both fixed and nonfixed sampling locations (alternately termed permanent and temporary samples), termed sampling with partial replacement ( SPR ), are considered to efficiently and effectively balance monitoring current status with detection of trends. This study utilized simulated sampling to assess the performance of fixed sampling locations, SPR , and strictly nonfixed designs for monitoring wetland S&T over time. Modeled changes in wetland density over time were used as inputs for sampling simulations. In contrast to previous evaluations of SPR , the results of this study support the use of a fixed sampling design and show that SPR may underestimate both S&T.
Global use of biodiesel is increasing rapidly. Combustion of biodiesel changes the emissions profile of diesel engines, altering their impact on both urban air pollution and climate. Here, we characterize exhaust emissions from conventional petroleum diesel and three neat biodiesels manufactured from soybean, canola, and yellow grease feedstocks. Exhaust was sampled from a fixed-speed 4.8 kW diesel generator at idle and full loads, and mass emission rates were determined for nitrogen oxides (NO, NO2, and NOx), particulate matter (PM), and elemental, organic, and black carbon (EC, OC, and BC). Additionally, particle size distributions were characterized. Largely consistent with a growing body of data on emissions from biodiesel, biodiesel emissions were cleaner by most metrics than those for conventional diesel. Emissions from the two primary-oil fuels, synthesized from soy and canola feedstocks, were cleaner by most metrics than emissions from diesel, producing approximately 55, 65, and 60% less PM, EC, and OC at engine idle and 40, 20, and 15% less at engine load. In addition, while primary-oil NOx emissions were 5% higher than diesel emissions at engine idle, they were more than 30% lower at engine load. Yellow grease emissions of PM, EC, and OC were reduced in comparison to diesel at engine idle by 60, 30, and 20%. However, at engine load, most yellow grease emissions were increased in comparison to diesel, resulting in approximately 5, 60, and 70% more PM, EC, and OC. Organic vapor emissions from primary-oil biodiesels were also lower, and aromatic emissions were much lower compared to diesel. Yellow grease NOx emissions were increased in comparison to diesel by approximately 5% at engine idle and 10% at engine load. Notably, NO2 accounted for a smaller fraction of NOx for all three biodiesels compared to diesel, a difference that may be more important than the somewhat higher NOx emissions in determining the impact of biodiesel on urban ozone formation. Taken together, our results suggest that widespread implementation of primary-oil biodiesels could result in improvements in urban ozone and PM pollution. In addition, by reducing both the mass and the EC content of those particles, primary-oil biodiesels may reduce anthropogenic climate forcing.
Accurate estimates of wetlands and stream extent provide context for scientific investigations, enable informed management, and measure progress towards no-net-loss policy goals. However, the default approach for monitoring extent, comprehensive mapping, is prohibitively resource intensive over large areas, making it both impractical and statistically unreliable. Therefore, a number of national and state-level programs have begun to employ probabilistic approaches to monitor wetland and stream extent. These programs have proven practical for their intended applications but little information exists about the ability of the designs to meet diverse, state-level information needs such as accurately capturing rare wetland types or detecting small-scale changes in extent or spatial distribution. Here, I utilized a simulated sampling approach to empirically model and evaluate probabilistic methods for monitoring wetland and stream extent in California. The optimized design was then directly validated against comprehensive mapping through a pilot-scale implementation. The flexibility of the simulated sampling method enabled assessment of performance for a variety of objectives, beyond statistical precision. By employing this unique approach to sampling design, the results could be customized for the specific information needs of California. Results indicate that generalized random tessellation stratified (GRTS) sampling, a spatially balanced selection methodology, provides significant advantages over simple random sampling or stratification. In addition, fixed sampling locations over time provide the best power for both estimating the current extent and detecting changes in extent over time. The pilot-scale implementation was conducted in two separate regions of California. By using regions with existing, comprehensive aquatic resource maps, a direct comparison was made between the probabilistic and comprehensive mapping efforts. The pilot produced precise estimates of aquatic resource extent but suggested that mapping and classification methodologies may require more standardization in order to compare estimates between probabilistic approaches and comprehensive maps. In addition to systematic methodological differences, additional simulated sampling suggests that the expected accuracy of the 95% confidence interval is, in fact, dependent on the sample size. Final design conclusions from this dissertation will be recommended to the State of California for implementation in a California S&T program for aquatic resource extent.
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)
'/%3e%3cuse xlink:href='%23a' transform='scale(-1 1)'/%3e%3c/g%3e%3cuse xlink:href='%23b' transform='rotate(72)'/%3e%3c/g%3e%3cuse xlink:href='%23b' transform='rotate(-72)'/%3e%3cuse xlink:href='%23c' transform='rotate(144)'/%3e%3c/svg%3e)