Effect of Aging on Solar Reflectance of White Cool Roof Coatings:Natural Weathering and the Influence on Building Energy Needs for Different Climate Conditions in Brazil

The use of cool materials on the building envelope is one of the most cost-effective ways to increase indoor thermal comfort conditions in hot climates and decrease the cooling energy needs.Despite the benefit of reducing cooling loads,researches have demonstrated that aging of roof coatings changes the initial solar reflectance(SR),which influences the long term building thermal and energy performance.Thus,this work presents preliminary natural weathering tests performed on samples of nine white coatings exposed to natural weathering for one year in the city of Sao Carlos,Brazil.Solar reflectances were measured with a spectrophotometer before and after exposure,every 3 months,for identifying the effect of aging along the time.The findings showed changes of 13%to 23%on SR after one year of natural weathering,with higher decrease on SR for rougher surfaces.The cleaning process restored from 90%to 100%of the original SR,which means maintenance can be an effective solution to restore the initial SR.Simulations indicated that roofs with higher solar reflectance increase indoor thermal comfort conditions and decrease the cooling energy need for buildings in hot climates,but the aging of white coatings increased the cooling energy needs along the time.

Dynamic change and diagnosis of physical, chemical and biological properties in bauxite residue disposal areas

Vegetation encroachment occurred in bauxite residue disposal area(BRDA)following natural weathering processes,whilst the typical indicators of soil formation are still uncertain.Residue samples were collected from the BRDA in Central China,and related physical,chemical and biological indicators of bauxite residue with different storage years were determined.The indicators of soil formation in bauxite residue were selected using principal component analysis,factor analysis,and comprehensive evaluation to establish soil quality diagnostic index model on disposal areas.Following natural weathering processes,the texture of bauxite residue changed from silty loam to sandy loam.The pH and EC decreased,whilst porosity,nutrient element content and microbial biomass increased.The identified minimum data set(MDS)included available phosphorus(AP),moisture content(MC),C/N,sand content,total nitrogen(TN),microbial biomass carbon(MBC),and pH.The soil quality index of bauxite residue increased,and the relative soil quality index decreased from 1.89 to 0.15,which indicated that natural weathering had a significant effect on improveing the quality of bauxite residue and forming a new soil-like matrix.The diagnostic model of bauxite residue was established to provide data support for the regeneration on disposal area.

Assessment of the Erosive Wear Kinetics of Epoxy Coatings Modified with Nanofillers

The paper presents results of investigation on the erosive wear kinetics of epoxy coatings modified with alumina or silica nanoparticles. Natural weathering caused a decrease of their erosive wear resistance. After a 3-year natural weathering, highest erosive wear resistance showed the epoxy coating modified with alumina nanoparticles.

The dynamic development of bacterial community following long-term weathering of bauxite residue

Bauxite residue is the industrial waste generated from alumina production and commonly deposited in impoundments.These sites are bare of vegetation due to the extreme high salinity and alkalinity,as well as lack of nutrients.However,long term weathering processes could improve residue properties to support the plant establishment.Here we investigate the development of bacterial communities and the geochemical drivers in bauxite residue,using Illumina high-throughput sequencing technology.Long term weathering reduced the pH in bauxite residue and increased its nutrients content.The bacterial community also significantly developed during long term weathering processes.Taxonomic analysis revealed that natural weathering processes encouraged the populations of Proteobacteria,Chloroflexi,Acidobacteria and Planctomycetes,whereas reducing the populations of Firmicutes and Actinobacteria.Redundancy analysis(RDA)indicated that total organic carbon(TOC)was the dominant factors affecting microbial structure.The results have demonstrated that natural weathering processes improved the soil development on the abandoned bauxite residue disposal areas,which also increased our understanding of the correlation between microbial variation and residue properties during natural weathering processes in Bauxite residue disposal areas.

Comparison of surface water chemistry and weathering effects of two lake basins in the Changtang Nature Reserve,China

The geochemistry of natural waters in the Changtang Nature Reserve,northern Tibet,can help us understand the geology of catchments,and provide additional insight in surface processes that influence water chemistry such as rock weathering on the Qinghai–Tibet Plateau.However,severe natural conditions are responsible for a lack of scientific data for this area.This study represents the first investigation of the chemical composition of surface waters and weathering effects in two lake basins in the reserve（Lake Dogaicoring Qiangco and Lake Longwei Co）.The results indicate that total dissolved solids（TDS）in the two lakes are significantly higher than in other gauged lakes on the Qinghai–Tibet Plateau,reaching 20–40 g/L,and that TDS of the tectonic lake（Lake Dogaicoring Qiangco）is significantly higher than that of the barrier lake（Lake Longwei Co）.Na＋and Cl-are the dominant ions in the lake waters as well as in the glacier-fed lake inflows,with chemical compositions mainly affected by halite weathering.In contrast,ion contents of inflowing rivers fed by nearby runoff are lower and concentrations of dominant ions are not significant.Evaporite,silicate,and carbonate weathering has relatively equal effects on these rivers.Due to their limited scope,small streams near the lakes are less affected by carbonate than by silicate weathering.