Time filter

Source Type

Maple Plain, MN, United States

Beck B.F.,University of Minnesota | Beck B.F.,Wenck Associates Inc | Johnson N.W.,University of Minnesota
Applied Geochemistry | Year: 2014

The production of methylmercury (MeHg), a bioaccumulative neurotoxin, in freshwater systems is primarily driven by naturally occurring sulfate reducing bacteria in anoxic sediment and waters. This research used laboratory microcosms to examine the influence of sulfate on MeHg production and partitioning in sulfate-impacted freshwater estuary sediment. A laboratory sulfate addition experiment exposed 20cm diameter intact sediment cores with varying organic carbon content to sulfate concentrations in the overlying water ranging from 5 to 50mgL-1. Results from the 6month incubation suggest that net MeHg production in sediment from open-water areas of the St. Louis River Estuary was not directly related to overlying water sulfate. Mercury mobility, as indicated by porewater concentrations, appeared to be related to the quantity of organic carbon and sulfur in sediment. Laboratory flux estimates were consistent with porewater concentrations and provided a means to compare diffusion-driven MeHg loading from sediment to MeHg loading from upstream sources. © 2014 Elsevier Ltd. Source

Guerra S.A.,Wenck Associates Inc | Lane D.D.,University of Kansas | Carter R.E.,University of Kansas | Peltier E.,University of Kansas | And 2 more authors.
Proceedings of the Air and Waste Management Association's Annual Conference and Exhibition, AWMA | Year: 2012

A new data analysis technique developed while evaluating continuous emission data collected from a trash compactor is presented. The evaluation involved tailpipe sampling with a portable emission monitoring system from a diesel fueled 525-hp trash compactor. The sampling campaign took place by running the compactor with regular number 2 diesel, 20% biodiesel mix (B20) and ultra-low sulfur diesel (ULSD) fuels. The purpose was to determine the possible emission reductions in NOx and CO2 from the use of B20 and ULSD in an off-road vehicle. The technique allowed for a valid use of the general linear model with engine speed as the covariate factor to test day, fuel type and compactor factors. This is an abstract of a paper presented at the 106th AWMA Annual Conference and Exhibition (Chicago, IL 6/25-28/2013). Source

Langer T.A.,Central Michigan University | Langer T.A.,Wenck Associates Inc | Murry B.A.,Central Michigan University | Murry B.A.,U.S. Fish and Wildlife Service | And 2 more authors.
Hydrobiologia | Year: 2016

β dissimilarity indices have described community variation occurring from unique structuring processes: species turnover and nestedness. However, the importance of scale definition remains critical and challenging during β assessments with a need for simultaneous spatial and temporal assessment to determine ecological phenomena governing biological communities. We aim to examine the contribution of turnover and nestedness structuring processes across multiple spatial and temporal scales to demonstrate the importance of scale consideration in β assessments. Using a site-to-basin-wide spatiotemporal hierarchical design, we examined diversity patterns, testing spatial, and temporal facets of β diversity structuring Laurentian Great Lake coastal wetland fish and macroinvertebrate communities from 2000 to 2012. Both fish and macroinvertebrate communities were analyzed using β dissimilarity indices under the same hierarchical design. Results indicated strong spatial and temporal turnover structuring with increasing β diversity and community turnover as scale localized. We suggest that high turnover is the result of inhospitable winter conditions followed by random re-colonization events in the spring. With relatively unique communities across space and time, biodiversity-oriented management of coastal wetlands should consider an all-inclusive approach as biodiversity hotspots are not apparent. © 2016 Springer International Publishing Switzerland Source

Wenck Associates Inc. | Date: 2014-11-25

Emergency response equipment trailers.

Wenck Associates Inc. | Date: 2014-11-25

Emergency response equipment trailers.

Discover hidden collaborations