Decision Tree Algorithm for Detection of Spatial Processes in Landscape Transformation

The conversion of landscapes by human activities results in widespread changes in landscape spatial structure. Regardless of the type of land conversion, there appears to be a limited number of common spatial configurations that result from such land transformation processes. Some of these configurations are considered optimal or more desirable than others. Based on pattern geometry, we define ten processes responsible for pattern change: aggregation, attrition, creation, deformation, dissection, enlargement, fragmentation, perforation, shift, and shrinkage. A novelty in this contribution is the inclusion of transformation processes causing expansion of the land cover of interest. Consequently, we propose a decision tree algorithm that enables detection of these processes, based on three parameters that have to be determined before and after the transformation of the landscape: area, perimeter length, and number of patches of the focal landscape class. As an example, the decision tree algorithm is applied to determine the transformation processes of three divergent land cover change scenarios: deciduous woodland degradation in Cadiz Township (Wisconsin, USA) 1831–1950, canopy gap formation in a terra firme rain forest at the Tiputini Biodiversity Station (Amazonian Ecuador) 1997–1998, and forest regrowth in Petersham Township (Massachusetts, USA) 1830–1985. The examples signal the importance of the temporal resolution of the data, since long-term pattern conversions can be subdivided in stadia in which particular pattern components are altered by specific transformation processes.     

Airborne emissions of mercury from municipal solid waste. I: new measurements from six operating landfills in Florida

Mercury-bearing material enters municipal landfills from a wide array of sources, including fluorescent lights, batteries, electrical switches, thermometers, and general waste; however, the fate of mercury (Hg) in landfills has not been widely studied. Using automated flux chambers and downwind atmospheric sampling, we quantified the primary pathways of Hg vapor releases to the atmosphere at six municipal landfill operations in Florida. These pathways included landfill gas (LFG) releases from active vent systems, passive emissions from landfill surface covers, and emissions from daily activities at each working face (WF). We spiked the WF at two sites with known Hg sources; these were readily detected downwind, and were used to test our emission modeling approaches. Gaseous elemental mercury (Hg(O)) was released to the atmosphere at readily detectable rates from all sources measured; rates ranged from approximately 1-10 ng m(-2) hr(-1) over aged landfill cover, from approximately 8-20 mg/hr from LFG flares (LFG included Hg(O) at microg/m3 concentrations), and from approximately 200-400 mg/hr at the WF. These fluxes exceed our earlier published estimates. Attempts to identify specific Hg sources in excavated and sorted waste indicated few readily identifiable sources; because of effective mixing and diffusion of Hg(O), the entire waste mass acts as a source. We estimate that atmospheric Hg releases from municipal landfill operations in the state of Florida are on the order of 10-50 kg/yr, substantially larger than our original estimates, but still a small fraction of current overall anthropogenic losses.     

Airborne emissions of mercury from municipal solid waste. II: potential losses of airborne mercury before landfill

Waste distribution and compaction at the working face of municipal waste landfills releases mercury vapor (Hg(o)) to the atmosphere, as does the flaring of landfill gas. Waste storage and processing before its addition to the landfill also has the potential to release Hg(o) to the air if it is initially present or formed by chemical reduction of Hg(II) to Hg(o) within collected waste. We measured the release of Hg vapor to the atmosphere during dumpster and transfer station activities and waste storage before landfilling at a municipal landfill operation in central Florida. We also quantified the potential contribution of specific Hg-bearing wastes, including mercury (Hg) thermometers and fluorescent bulbs, and searched for primary Hg sources in sorted wastes at three different landfills. Surprisingly large fluxes were estimated for Hg losses at transfer facilities (approximately 100 mg/hr) and from dumpsters in the field (approximately 30 mg/hr for 1000 dumpsters), suggesting that Hg emissions occurring before landfilling may constitute a significant fraction of the total emission from the disposal/landfill cycle and a need for more measurements on these sources. Reducing conditions of landfill burial were obviously not needed to generate strong Hg(o) signals, indicating that much of the Hg was already present in a metallic (Hg(o)) form. Attempts to identify specific Hg sources in excavated and sorted waste indicated few readily identifiable sources; because of effective mixing and diffusion of Hg(o), the entire waste mass acts as a source. Broken fluorescent bulbs and thermometers in dumpsters emitted Hg(o) at 10 to >100 microg/hr and continued to act as near constant sources for several days.     

Mercury bioaccumulation in aquatic biota along a salinity gradient in the Saint John River estuary

Although estuaries are critical habitats for many aquatic species, the spatial trends of toxic methylmercury(MeHg) in biota from fresh to marine waters are poorly understood. Our objective was to determine if MeHg concentrations in biota changed along a salinity gradient in an estuary. Fourspine Stickleback(Apeltes quadracus), invertebrates(snails,amphipods, and chironomids), sediments, and water were collected from ten sites along the Saint John River estuary, New Brunswick, Canada in 2015 and 2016, with salinities ranging from 0.06 to 6.96. Total mercury(proxy for MeHg) was measured in whole fish and MeHg was measured in a subset of fish, pooled invertebrates, sediments, and water. Stable sulfur(δ~(34)S), carbon(δ~(13) C), and nitrogen(δ~(15)N) isotope values were measured to assess energy sources(S, C) and relative trophic level(N). There were increases in biotic δ~(13)C and δ~(34)S from fresh to more saline sites and these measures were correlated with salinity.Though aqueous MeHg was higher at the freshwater than more saline sites, only chironomid MeHg increased significantly with salinity. In the Saint John River estuary, there was little evidence that MeHg and its associated risks increased along a salinity gradient.     

Atmospheric Emissions from Oxidation Ponds

The electrodes in industrial precipitators collect many tons of dust daily, and the efficient transfer of this dust burden to the hoppers is a challenging problem in mechanical engineering. Many varieties of devices have been tried; hammers, vibrators, scrapers, water flushing, gas blasting, etc. Impact devices for this purpose are usually called “rappers.” Laboratory experiments described in this paper show that normal (perpendicular) rapping is more effective than shear rapping; that thick dust layers are more easily removed by rapping than thin ones; that rapping becomes easier with increasing temperature, within limits; and that the electrostatic forces acting upon the precipitated dust layer play an important role. Quantitative data are shown graphically. The relation of these results to previous studies by other investigators is discussed.     

Estimation of regional building-related C&D debris generation and composition: case study for Florida, US

Methodology for the accounting, generation, and composition of building-related construction and demolition (C&D) at a regional level was explored. Six specific categories of debris were examined: residential construction, nonresidential construction, residential demolition, nonresidential demolition, residential renovation, and nonresidential renovation. Debris produced from each activity was calculated as the product of the total area of activity and waste generated per unit area of activity. Similarly, composition was estimated as the product of the total area of activity and the amount of each waste component generated per unit area. The area of activity was calculated using statistical data, and individual site studies were used to assess the average amount of waste generated per unit area. The application of the methodology was illustrated using Florida, US approximately 3,750,000 metric tons of building-related C&D debris were estimated as generated in Florida in 2000. Of that amount, concrete represented 56%, wood 13%, drywall 11%, miscellaneous debris 8%, asphalt roofing materials 7%, metal 3%, cardboard 1%, and plastic 1%. This model differs from others because it accommodates regional construction styles and available data. The resulting generation amount per capita is less than the US estimate - attributable to the high construction, low demolition activity seen in Florida.     

Behavioral responses of bison and elk in Yellowstone to snowmobiles and snow coaches.

Managers of public lands are charged with protecting some of our most important natural resources and ecosystems, while providing for their use and enjoyment by visitors. Almost one million visitors entered Yellowstone National Park by motorized means on snowmobiles (87%) or snow coaches (13%) during 1992-2003. Most vehicles toured the central portion of the park where bison (Bison bison) and elk (Cervus elaphus) concentrate in geothermal areas. We sampled >6500 interactions between groups of these species and groups of snowmobiles and snow coaches (collectively, OSV, over-snow vehicles) during five winters (1999-2000, 2002-2004). Multinomial logits models were used to identify conditions leading to behavioral responses. Elk responded three times as often (52%) as bison (19%) during interactions with groups of snowmobiles and snow coaches due to increased vigilance responses (elk, 44%; bison, 10%). However, the frequency of higher-intensity movement responses by bison and elk were similar (6-7% travel, 1-2% flight, <1% defense) and relatively low compared to other studies of ungulates and snowmobile disturbance. The likelihood of active responses by bison and elk increased significantly if animals were on or near roads, groups were smaller, or humans approached. The likelihood of an active response by bison decreased within winters having the largest visitation, suggesting some habituation to snowmobiles and snow coaches. There was no evidence that snowmobile use during the past 35 years affected the population dynamics or demography of bison or elk. Thus, we suggest that regulations restricting levels and travel routes of over-snow vehicles (OSVs) were effective at reducing disturbances to bison and elk below a level that would cause measurable fitness effects. We recommend park managers consider maintaining OSV traffic levels at or below those observed during our study. Regardless, differing interpretations of the behavioral and physiological response data will continue to exist because of the diverse values and beliefs of the many constituencies of Yellowstone.     

Sustainable disposal of municipal solid waste: Post bioreactor landfill polishing

Sustainable disposal of municipal solid waste (MSW) requires assurance that contaminant release will be minimized or prevented within a reasonable time frame before the landfill is abandoned so that the risk of contamination release is not passed to future generations. This could be accomplished through waste acceptance criteria such as those established by the European Union (EU) that prohibit land disposal of untreated organic matter. In the EU, mechanical, biological and/or thermal pretreatment of MSW is therefore necessary prior to landfilling which is complicated and costly. In other parts of the world, treatment within highly engineered landfills is under development, known as bioreactor landfills. However, the completed bioreactor landfill still contains material, largely nonbiodegradable carbon and ammonia that may be released to the environment over the long-term. This paper provides a conceptual analysis of an approach to ensure landfill sustainability by the rapid removal of these remaining materials, leachate treatment and recirculation combined with aeration. The analysis in this paper includes a preliminary experimental evaluation using real mature leachate and waste samples, a modeling effort using a simplified mass balance approach and input parameters from real typical bioreactor cases, and a cost estimate for the suggested treatment method.