Atmospheric CO 2 is naturally sequestered in ultramafi c mine tailings as a result of the weathering of serpen ne minerals [Mg 3 Si 2 O 5 (OH) 4 ] and brucite [Mg(OH) 2 ], and subsequent mineraliza on of CO 2 in hydrated magnesium carbonate minerals, such as hydromagnesite [Mg 5 (CO 3 ) 4 (OH) 2 ·4H 2 O]. Understanding the CO 2 trapping mechanisms is key to evalua ng the capacity of such tailings for carbon sequestra on. Natural CO 2 sequestra on in subaerially exposed ultramafi c tailings at a mine site near Mount Keith, Australia is assessed with a process-based reac ve transport model. The model formula on includes unsaturated fl ow, equa ons accoun ng for energy balance and vapor diff usion, fully coupled with solute transport, gas diff usion, and geochemical reac ons. Atmospheric boundary condi ons accoun ng for the eff ect of climate varia ons are also included. Kine c dissolu on of serpenne, dissolu on-precipita on of brucite and primary carbonates-calcite (CaCO 3 ), dolomite [MgCa(CO 3 ) 2 ], magnesite (MgCO 3 ), as well as the forma on of hydromagnesite, halite (NaCl), gypsum (CaSO 4 ·2H 2 O), blödite [Na 2 Mg(SO 4 ) 2 ·4H 2 O], and epsomite [MgSO 4 ·7H 2 O]-are considered. Simula on results are consistent with fi eld observa ons and mineralogical data from tailings that weathered for 10 yr. Precipita on of hydromagnesite is both predicted and observed, and is mainly controlled by the dissolu on of serpen ne (the source of Mg) and equilibrium with CO 2 ingressing from the atmosphere. The predicted rate for CO 2 entrapment in these tailings ranges between 0.6 and 1 kg m −2 yr −1 . However, modeling results suggest that this rate is sensi ve to CO 2 ingress through the mineral waste and may be enhanced by several mechanisms, including atmospheric pumping.Abbrevia ons: BET, Brunauer-Emme -Teller; SWCC, soil water characteris c curve; TIC, total inorganic carbon; TSF, tailings storage facility; XRPD, X-ray powder diff rac on.

Abstract. Arctic and subarctic regions are amongst the most susceptible regions on Earth to global warming and climate change. Understanding and predicting the impact of climate change in these regions require a proper process representation of the interactions between climate, carbon cycle, and hydrology in Earth system models. This study focuses on land surface models (LSMs) that represent the lower boundary condition of general circulation models (GCMs) and regional climate models (RCMs), which simulate climate change evolution at the global and regional scales, respectively. LSMs typically utilize a standard soil configuration with a depth of no more than 4 m, whereas for cold, permafrost regions, field experiments show that attention to deep soil profiles is needed to understand and close the water and energy balances, which are tightly coupled through the phase change. To address this gap, we design and run a series of model experiments with a one-dimensional LSM, called CLASS (Canadian Land Surface Scheme), as embedded in the MESH (Modélisation Environmentale Communautaire – Surface and Hydrology) modelling system, to (1) characterize the effect of soil profile depth under different climate conditions and in the presence of parameter uncertainty; (2) assess the effect of including or excluding the geothermal flux in the LSM at the bottom of the soil column; and (3) develop a methodology for temperature profile initialization in permafrost regions, where the system has an extended memory, by the use of paleo-records and bootstrapping. Our study area is in Norman Wells, Northwest Territories of Canada, where measurements of soil temperature profiles and historical reconstructed climate data are available. Our results demonstrate a dominant role for parameter uncertainty, that is often neglected in LSMs. Considering such high sensitivity to parameter values and dependency on the climate condition, we show that a minimum depth of 20 m is essential to adequately represent the temperature dynamics. We further show that our proposed initialization procedure is effective and robust to uncertainty in paleo-climate reconstructions and that more than 300 years of reconstructed climate time series are needed for proper model initialization.

Uruguay has stimulated the development of its forest sector since the promulgation of Forest Law N° 15 939 in December of 1987. Nevertheless, the substitution of natural grasslands with forest plantations for industrial use has raised concerns regarding hydrological processes of groundwater recharge and water consumption involving evapotranspiration. The purpose of this study is to assess the effects of this substitution approach on water resources. Input data were collected from two small experimental watersheds of roughly 100–200 hectares located in western Uruguay. The watersheds are characterized by Eucalyptus Globulus ssp. Maidenni and natural grasslands for cattle use. Total rainfall, stream discharge, rainfall redistribution, soil water content and groundwater level data were collected. Groundwater recharge was estimated from water table fluctuations and from groundwater contributions to base flows. Seasonal and annual water budgets were computed from October of 2006 to September of 2014 to evaluate changes in the hydrological processes. The data show a decrease in annual specific discharge of roughly 17% for mean hydrological years and no conclusive effects on annual groundwater recharge in the forested watershed relative to the reference pasture watershed. Reduced annual specific discharge is equivalent to the mean annual interception. The computed actual annual evapotranspiration is consistent with international catchment measurements. Reduction rates vary seasonally and according to accumulated rainfall and its temporary distribution. The degree of specific discharge decline is particularly high for drier autumns and winters (32 to 28%) when the corresponding rainfall varies from 275 to 400 mm. These results are of relevance for water resources management efforts, as water uses downstream can be affected. These findings, based on a study period dominated by anomalous wet springs and summers and by dry autumns and winters, oppose earlier results based on 34 years of rainfall and discharge data drawn from Uruguayan large basins. Copyright © 2016 John Wiley & Sons, Ltd.

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In the pandemic of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) many strategies have been performed in order to control viral spread in the population and known the real-time situation about the number of infected persons. In this sense, Wastewater Based Epidemiology (WBE) has been applied as an excellent tool to evaluate the virus circulation in a population. In order to obtain reliable results, three low-cost viral concentration methods were evaluated in this study, polyethylene glycol (PEG) precipitation, skimmed milk flocculation (SM) and Aluminum polychloride flocculation, for Pseudomonas aeruginosa bacteriophage PP7 as a surrogate for non-enveloped viruses and Bovine Coronavirus (BCoV) as a surrogate for enveloped virus, with emphasis for SARS- CoV-2. Our results suggest that PEG precipitation for viral concentration, for both enveloped and non-enveloped virus from wastewater is an appropriate approach since it was more sensitive compared to SM flocculation and Aluminum polychloride flocculation. This methodology can be used for WBE studies in order to follow the epidemiology of the SARS-CoV-2 pandemic, mainly in developing countries where the economic resources are frequently limited.