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In industrialized countries, large amounts of mineral wastes are produced. They are re-used in various ways, particularly in road and earth constructions, substituting primary resources such as gravel. However, they may also contain pollutants, such as heavy metals, which may be leached to the groundwater. The toxic impacts of these emissions are so far often neglected within Life Cycle Assessments (LCA) of products or waste treatment services and thus, potentially large environmental impacts are currently missed. This study aims at closing this gap by assessing the ecotoxic impacts of heavy metal leaching from industrial mineral wastes in road and earth constructions. The flows of metals such as Sb, As, Pb, Cd, Cr, Cu, Mo, Ni, V and Zn originating from three typical constructions to the environment are quantified, their fate in the environment is assessed and potential ecotoxic effects evaluated. For our reference country, Germany, the industrial wastes that are applied as Granular Secondary Construction Material (GSCM) carry more than 45,000 t of diverse heavy metals per year. Depending on the material quality and construction type applied, up to 150 t of heavy metals may leach to the environment within the first 100 years after construction. Heavy metal retardation in subsoil can potentially reduce the fate to groundwater by up to 100%. One major challenge of integrating leaching from constructions into macro-scale LCA frameworks is the high variability in micro-scale technical and geographical factors, such as material qualities, construction types and soil types. In our work, we consider a broad range of parameter values in the modeling of leaching and fate. This allows distinguishing between the impacts of various road constructions, as well as sites with different soil properties. The findings of this study promote the quantitative consideration of environmental impacts of long-term leaching in Life Cycle Assessment, complementing site-specific risk assessment, for the design of waste management strategies, particularly in the construction sector.

Moisture availability is a strong determinant of decomposition rates in forests worldwide. Climate models suggest that many terrestrial ecosystems are at risk from future droughts, suggesting moisture limiting conditions will develop across a range of forests worldwide. The impacts of increasing drought conditions on forest carbon (C) fluxes due to shifts in organic matter decay rates may be poorly characterised due to limited experimental research. To appraise this question, we conducted a meta-analysis of forest drought experiment studies worldwide, examining spatial limits, knowledge gaps and potential biases. To identify limits to experimental knowledge, we projected the global distribution of forest drought experiments against spatially modelled estimates of (i) future precipitation change, (ii) ecosystem total above-ground C and (iii) soil C storage. Our assessment, involving 115 individual experimental study locations, found a mismatch between the distribution of forest drought experiments and regions with higher levels of future drought risk and C storage, such as Central America, Amazonia, the Atlantic Forest of Brazil, equatorial Africa and Indonesia. Decomposition rate responses in litter and soil were also relatively under-studied, with only 30 experiments specifically examining the potential experimental impacts of drought on C fluxes from soil or litter. We propose new approaches for engaging experimentally with forest drought research, utilising standardised protocols to appraise the impacts of drought on the C cycle, while targeting the most vulnerable and relevant forests.

Anaerobic nitrogen removal technologies offer advantages in terms of energy and cost savings over conventional nitrification-denitrification systems. A mathematical model was constructed to evaluate the influence of process operation on the coexistence of nitrite dependent anaerobic methane oxidizing bacteria (n-damo) and anaerobic ammonium oxidizing bacteria (anammox) in a single granule. The nitrite and methane affinity constants of n-damo bacteria were measured experimentally. The biomass yield of n-damo bacteria was derived from experimental data and a thermodynamic state analysis. Through simulations, it was found that the possible survival of n-damo besides anammox bacteria was sensitive to the nitrite/ammonium influent ratio. If ammonium was supplied in excess, n-damo bacteria were outcompeted. At low biomass concentration, n-damo bacteria lost the competition against anammox bacteria. When the biomass loading closely matched the biomass concentration needed for full nutrient removal, strong substrate competition occurred resulting in oscillating removal rates. The simulation results further reveal that smaller granules enabled higher simultaneous ammonium and methane removal efficiencies. The implementation of simultaneous anaerobic methane and ammonium removal will decrease greenhouse gas emissions, but an economic analysis showed that adding anaerobic methane removal to a partial nitritation/anammox process may increase the aeration costs with over 20%. Finally, some considerations were given regarding the practical implementation of the process.

Climate change is a growing concern across the globe, and the Provincial Government of Ontario recognizes that climate change impacts need to be considered in all decision-making. In Southern Ontario, a critical and ongoing challenge is balancing the competing water demands under changing climate for various uses to ensure prosperity and sustainability in the future. A better understanding and quantification of impacts of possible climate change on regional hydrology are necessary for sustainable water resources management and maintaining healthy ecosystems in this region. In order to study the impacts of future climate on the regional water resources, a large-scale hydrologic model was developed for Southern Ontario within the Great Lakes basin using the Soil and Water Assessment Tool (SWAT). The study area includes four basins: Eastern Georgian Bay, Eastern Lake Huron, Northern Lake Erie, and Lake Ontario and Niagara Peninsula basins, covering a total area of about 84,650 km2. The hydrologic model was calibrated and validated using monthly observed streamflow data at 40 gauging stations, and spatially validated at another 40 gauging stations across the study area. The developed model was employed to estimate water budget components for a reference period (1971-2000), and to assess climate change impacts on the hydrologic regime during the mid-century (2041-2070) and the end-century (2071-2100). Projected climate data from five GCM-RCMs simulations for RCP4.5 and RCP8.5 scenarios were obtained from the NA-CORDEX archive. After bias correction, climate data sets were used in the SWAT model for the impact assessment. Based on the model calibration and validation results, the overall performance of the model was found to be satisfactory. Its performance was better in the predominantly agricultural Northern Lake Erie and Eastern Lake Huron basins than the other two basins. The average annual precipitation, evapotranspiration (ET), surface runoff and water yields for the study area over the period 1971-2000 were estimated at 979 mm, 540 mm, 183 mm and 410 mm, respectively. The average annual precipitation in the four basins varied from 923 mm to 1049 mm, and water yields were found to vary between 377 mm and 465 mm. The projected increases in mean annual temperature are 3.0oC and 2.4oC by the mid-century, while the increases are 5.2oC and 3.2oC by the end-century for RCP8.5 and RCP4.5 scenarios, respectively. The average annual precipitation of the study area is projected to increase by 8% to 16%, depending on the scenario and time period. The possible increases in precipitation are relatively high for the RCP8.5 scenario and likely to vary between 13% and 18% in the four basins by the end of the 21st century. By the mid-century, the average annual water yields in the four basins are predicted to increase by 7% to 20%, and 5% to 13% under RCP8.5 and RCP4.5 scenarios, respectively. By the end-century, the projected increases in the annual water yields of the basins are 5% to 26% for RCP8.5 scenario and 3% to 11% for RCP4.5 scenario. In general, the average monthly water yield in the study area is likely to increase during December to February, but decrease in the months of March and April. The results are also presented spatially for the subwatersheds across the study area. The study results would help in planning and management of water resources, and in developing climate change adaptation plans and strategies.

The activity of methanogens and related bacteria which inhabit the coal beds is essential for stimulating new biogenic coal bed methane (CBM) production from the coal matrix. In this study, the microbial community structure and methanogenesis were investigated in Southern Qinshui Basin in China, and the composition and stable isotopic ratios of CBM were also determined. Although geochemical analysis suggested a mainly thermogenic origin for CBM, the microbial community structure and activities strongly implied the presence of methanogens in situ. 454 pyrosequencing analysis combined with methyl coenzyme-M reductase (mcrA) gene clone library analysis revealed that the archaeal communities in the water samples from both coal seams were similar, with the dominance of hydrogenotrophic methanogen Methanobacterium. The activity and potential of these populations to produce methane were confirmed by the observation of methane production in enrichments supplemented with H2 + CO2 and formate, and the only archaea successfully propagated in the tested water samples was from the genus Methanobacterium. 454 pyrosequencing analysis also recovered the diverse bacterial communities in the water samples, which have the potential to play a role in the coal biodegradation fueling methanogens. These results suggest that the biogenic CBM was generated by coal degradation via the hydrogenotrophic methanogens and related bacteria, which also contribute to the huge CBM reserves in Southern Qinshui Basin, China.

Abstract The co-pyrolysis technology of the second-generation feedstocks has both engineering and environmental advantages towards resource recovery, waste stream reduction, and energy generation. However, there exists a large knowledge gap about the co-pyrolytic mechanisms, kinetics, emissions and products of biomass wastes. This study aimed to quantify the co-pyrolytic interactions between the five (N2, CO2, and three mixed) atmospheres and the two feedstocks of sewage sludge (SS) and coffee grounds (CG) as well as their emissions and products. Thermogravimetric-Fourier transform infrared spectrometry, two-dimensional correlation spectroscopy and pyrolysis-gas chromatography/mass spectrometry analyses were combined. An eight-parallel distributed activation energy model was adopted to elucidate the dynamic reaction mechanisms in the co-pyrolytic atmospheres. The co-pyrolytic interaction changed the maximum weight loss rate of the first peak by −2.5 to 38.6% and −1.9 to 36.9% in the N2 and CO2 atmospheres, respectively. The mass loss rate peak in the first stage was higher in the N2 than CO2 and mixed atmospheres, while the peak temperature of the maximum mass loss rate in the second stage declined with the elevated CO2 concentration. The replacement of N2 with the different CO2 concentrations significantly increased the activation energies of the 5th and 7th pseudo-components. The temperature dependency of evolved gases was of the following order: ethers/esters → acids/ketones/aldehydes/CO2 → hydrocarbons in the N2 atmosphere, and acids/ketones/aldehydes → esters/ethers → hydrocarbons in the CO2 atmosphere. The co-pyrolysis improved the yields of the hydrocarbon and phenol-type compounds and reduced the formations of the acid and nitrogenous compounds. Our results yielded valuable insights into a cleaner co-pyrolysis process.