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1. Role of landfill cover materials in mitigating GHG emissions in biogeochemical landfill cover system

   https://doi.org/10.1061/9780784482322.006  

   Rai, Raksha K. ; Reddy, Krishna R. ( May 2019 , Proc. World Environmental and Water Resources Congress 2019: Emerging Innovative Technologies and International Perspectives, ASCE)

   Municipal solid waste (MSW) landfills are known to be one of the major sources of greenhouse gas (GHG) emissions into the atmosphere. In order to alleviate these emissions, an innovative biogeochemical cover system is proposed to mitigate both methane (CH4) and carbon dioxide (CO2) emissions, which are the predominant gases in landfill gas (LFG) emissions. This paper investigates four materials: soil, non-activated biochar, methanotrophic activated biochar, and basic oxygen furnace (BOF) slag for their CH4 and CO2 uptake capacity. First, the physical and chemical properties of the four materials were tested. Thereafter, several series of batch tests were conducted to determine CH4 and CO2 uptake by each material. The results demonstrate that the soil has the potential to oxidize CH4 into CO2 due to presence of CH4 oxidizing (methanotrophic) bacteria, while the BOF steel slag has potential to sequester CO2. The methanotrophic activated biochar showed enhanced biological activity due to high methanotrophic population, mitigating CH4 efficiently. However, the non-activated biochar had little to no effect on the uptake of either CH4 or CO2. Finally, the combination of these cover materials at different proportions in different configurations is being investigated to optimize the biogeochemical cover system to mitigate both CH4 and CO2 emissions. 

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2. Strong correlations of sea ice cover with macroalgal cover along the Antarctic Peninsula: Ramifications for present and future benthic communities

   https://doi.org/10.1525/elementa.2023.00020  

   Amsler, Charles D. ; Amsler, Margaret O. ; Klein, Andrew G. ; Galloway, Aaron W. ; Iken, Katrin ; McClintock, James B. ; Heiser, Sabrina ; Lowe, Alex T. ; Schram, Julie B. ; Whippo, Ross ( January 2023 , Elem Sci Anth)

   Macroalgal forests dominate shallow hard bottom areas along the northern portion of the Western Antarctic Peninsula (WAP). Macroalgal biomass and diversity are known to be dramatically lower in the southern WAP and at similar latitudes around Antarctica, but few reports detail the distributions of macroalgae or associated macroinvertebrates in the central WAP. We used satellite imagery to identify 14 sites differing in sea ice coverage but similar in terms of turbidity along the central WAP. Fleshy macroalgal cover was strongly, negatively correlated with ice concentration, but there was no significant correlation between macroinvertebrate cover and sea ice. Overall community (all organisms) diversity correlated negatively with sea ice concentration and positively with fleshy macroalgal cover, which ranged from around zero at high ice sites to 80% at the lowest ice sites. Nonparametric, multivariate analyses resulted in clustering of macroalgal assemblages across most of the northern sites of the study area, although they differed greatly with respect to macroalgal percent cover and diversity. Analyses of the overall communities resulted in three site clusters corresponding to high, medium, and low fleshy macroalgal cover. At most northern sites, macroalgal cover was similar across depths, but macroalgal and macroinvertebrate distributions suggested increasing effects of ice scour in shallower depths towards the south. Hindcast projections based on correlations of ice and macroalgal cover data suggest that macroalgal cover at many sites could have been varying substantially over the past 40 years. Similarly, based on predicted likely sea ice decreases by 2100, projected increases in macroalgal cover at sites that currently have high ice cover and low macroalgal cover are substantial, often with only a future 15% decrease in sea ice. Such changes would have important ramifications to future benthic communities and to understanding how Antarctic macroalgae may contribute to future blue carbon sequestration. 

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3. Smart Webcam Cover: Exploring the Design of an Intelligent Webcam Cover to Improve Usability and Trust

   https://doi.org/10.1145/3494983  

   Do, Youngwook ; Park, Jung Wook ; Wu, Yuxi ; Basu, Avinandan ; Zhang, Dingtian ; Abowd, Gregory D. ; Das, Sauvik ( December 2021 , Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies)

   Laptop webcams can be covertly activated by malware and law enforcement agencies. Consequently, 59% percent of Americans manually cover their webcams to avoid being surveilled. However, manual covers are prone to human error---through a survey with 200 users, we found that 61.5% occasionally forget to re-attach their cover after using their webcam. To address this problem, we developed Smart Webcam Cover (SWC): a thin film that covers the webcam (PDLC-overlay) by default until a user manually uncovers the webcam, and automatically covers the webcam when not in use. Through a two-phased design iteration process, we evaluated SWC with 20 webcam cover users through a remote study with a video prototype of SWC, compared to manual operation, and discussed factors that influence users' trust in the effectiveness of SWC and their perceptions of its utility. 

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4. Probability Distribution of Soil Suction of Engineered Turf Cover and Compacted Clay Cover

   https://doi.org/10.1051/e3sconf/202338224002  

   Alam, Md Jobair ; Aggarwal, Maalvika ( January 2023 , E3S Web of Conferences)

   Bardanis, M. (Ed.)

   It is unlikely to predict the distribution of soil suction in the field deterministically. It is well established that there are various sources of uncertainty in the measurement of matric suction, and the suction measurements in the field are even more critical because of the heterogeneities in the field conditions. Hence it becomes necessary to probabilistically characterize the suction in the field for enhanced reliability. The objective of this study was to conduct a probabilistic analysis of measured soil suction of two different test landfill covers, compacted clay cover (CC) and engineered turf cover (ETC), under similar meteorological events. The size of the two test landfill covers was 3 m × 3 m (10 ft. × 10 ft.) and 1.2 m (4ft.) in depth. The covers were constructed by excavating the existing subgrade, placing 6-mil plastic sheets, and backfilling the excavated soil, followed by layered compaction. Then the covers were instrumented identically with soil water potential sensors up to specified depths. One of the covers acted as the CC, and the other cover was ETC. In ETC, engineered turf was laid over the compacted soil. The engineered turf consisted of a structured LLDPE geomembrane overlain by synthetic turf (polyethylene fibers tufted through a double layer of woven polypropylene geotextiles). The sensors were connected to an automated data logging system and the collected data were probabilistically analyzed using the R program. There were significant inconsistencies in the descriptive statistical parameters of the measured soil suction at both covers under the same climatic conditions. Soil suction measured in the field ranged between almost 12 to 44 kPa in ETC, while it was in the range of almost 1 to 2020 kPa in the CC. The histogram and quantile-quantile (Q-Q) plot showed the data to be non-normally distributed in the field. A heavy-tailed leptokurtic (Kurtosis=13) distribution of suction was observed in the ETC with substantial outliers. In contrast, the suction distribution in CC was observed skewed to the right containing a thinner tail indicating an almost platykurtic distribution. The distribution of suction in the field under engineered turf was observed to be reasonably consistent with time compared to bare soil under the same meteorological events. The results obtained from this study revealed the engineered turf system to be an effective barrier to inducing changes in soil suction against climatic events. 

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5. Elevation, canopy cover and grass cover structure patterns of seedling establishment in a subtropical post‐fire restoration

   https://doi.org/10.1002/2688-8319.12280  

   Warneke, Christopher ; Brudvig, Lars A. ; Gregg, Makani ; McDaniel, Sierra ; Yelenik, Stephanie ( October 2023 , Ecological Solutions and Evidence)

   Ecological restoration is beneficial to ecological communities in this era of large‐scale landscape change and ecological disruption. However, restoration outcomes are notoriously variable, which makes fine‐scale decision‐making challenging. This is true for restoration efforts that follow large fires, which are increasingly common as the climate changes.

   Post‐fire restoration efforts, like tree planting and seeding have shown mixed success, though the causes of the variation in restoration outcomes remain unclear. Abiotic factors such as elevation and fire severity, as well as biotic factors, such as residual canopy cover and abundance of competitive understorey grasses, can vary across a burned area and may all influence the success of restoration efforts to re‐establish trees following forest fires.

   We examined the effect of these factors on the early seedling establishment of a tree species—māmane (Sophora chrysophylla)—in a subtropical montane woodland in Hawaiʻi. Following a human‐caused wildfire, we sowed seeds of māmane as part of a restoration effort. We co‐designed a project to examine māmane seedling establishment.

   We found that elevation was of overriding importance, structuring total levels of plant establishment, with fewer seedlings establishing at higher elevations. Residual canopy cover was positively correlated with seedling establishment, while cover by invasive, competitive understorey grasses very weakly positively correlated with increased seedling establishment.

   Our results point to specific factors structuring plant establishment following a large fire and suggest additional targeted restoration actions within this subtropical system. For example, if greater native woody recruitment is a management goal, then actions could include targeted seed placement at lower elevations where establishment is more likely, increased seeding densities at high elevation where recruitment rates are lower, and/or invasive grass removal prior to seeding. Such actions may result in faster native ecosystem recovery, which is a goal of local land managers.

    

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