Baez-Villanueva, O. M., Zambrano-Bigiarini, M., Miralles, D. G., Beck, H. E., Siegmund, J. F., Alvarez-Garreton, C., et al. (2024). On the timescale of drought indices for monitoring streamflow drought considering catchment hydrological regimes. Hydrol. Earth Syst. Sci., 28(6), 1415–1439.
Abstract: There is a wide variety of drought indices, yet a consensus on suitable indices and temporal scales for monitoring streamflow drought remains elusive across diverse hydrological settings. Considering the growing interest in spatially distributed indices for ungauged areas, this study addresses the following questions: (i) What temporal scales of precipitation-based indices are most suitable to assess streamflow drought in catchments with different hydrological regimes? (ii) Do soil moisture indices outperform meteorological indices as proxies for streamflow drought? (iii) Are snow indices more effective than meteorological indices for assessing streamflow drought in snow-influenced catchments? To answer these questions, we examined 100 near-natural catchments in Chile with four hydrological regimes, using the standardised precipitation index (SPI), standardised precipitation evapotranspiration index (SPEI), empirical standardised soil moisture index (ESSMI), and standardised snow water equivalent index (SWEI), aggregated across various temporal scales. Cross-correlation and event coincidence analysis were applied between these indices and the standardised streamflow index at a temporal scale of 1 month (SSI-1), as representative of streamflow drought events. Our results underscore that there is not a single drought index and temporal scale best suited to characterise all streamflow droughts in Chile, and their suitability largely depends on catchment memory. Specifically, in snowmelt-driven catchments characterised by a slow streamflow response to precipitation, the SPI at accumulation periods of 12-24 months serves as the best proxy for characterising streamflow droughts, with median correlation and coincidence rates of approximately 0.70-0.75 and 0.58-0.75, respectively. In contrast, the SPI at a 3-month accumulation period is the best proxy over faster-response rainfall-driven catchments, with median coincidence rates of around 0.55. Despite soil moisture and snowpack being key variables that modulate the propagation of meteorological deficits into hydrological ones, meteorological indices are better proxies for streamflow drought. Finally, to exclude the influence of non-drought periods, we recommend using the event coincidence analysis, a method that helps assessing the suitability of meteorological, soil moisture, and/or snow drought indices as proxies for streamflow drought events.
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Campos, J. L., Crutchik, D., Franchi, O., Pavissich, J. P., Belmonte, M., Pedrouso, A., et al. (2019). Nitrogen and Phosphorus Recovery From Anaerobically Pretreated Agro-Food Wastes: A Review. Front. Sustain. Food Syst., 2, 11 pp.
Abstract: Anaerobic digestion (AD) is commonly used for the stabilization of agro-food wastes and recovery of energy as methane. Since AD removes organic C but not nutrients (N and P), additional processes to remove them are usually applied to meet the stringent effluent criteria. However, in the past years, there was a shift from the removal to the recovery of nutrients as a result of increasing concerns regarding limited natural resources and the importance given to the sustainable treatment technologies. Recovering N and P from anaerobically pretreated agro-food wastes as easily transportable and marketable products has gained increasing importance to meet both regulatory requirements and increase revenue. For this reason, this review paper gives a critical comparison of the available and emerging technologies for N and P recovery from AD residues.
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Chang, M., Liu, B., Wang, B., Martinez-Villalobos, C., Ren, G., & Zhou, T. (2022). Understanding future increases in precipitation extremes in global land monsoon regions. J. Clim., 35, 1839–1851.
Abstract: This study investigates future changes in daily precipitation extremes and the involved physics over the global land monsoon (GM) region using climate models from the Coupled Model Intercomparison Project Phase 6 (CMIP6). The daily precipitation extreme is identified by the cutoff scale, measuring the extreme tail of the precipitation distribution. Compared to the historical period, multi-model results reveal a continuous increase in precipitation extremes under four scenarios, with a progressively higher fraction of precipitation exceeding the historical cutoff scale when moving into the future. The rise of the cutoff-scale by the end of the century is reduced by 57.8% in the moderate emission scenario relative to the highest scenario, underscoring the social benefit in reducing emissions. The cutoff scale sensitivity, defined by the increasing rates of the cutoff scale over the GM region to the global mean surface temperature increase, is nearly independent of the projected periods and emission scenarios, roughly 8.0% K−1 by averaging all periods and scenarios. To understand the cause of the changes, we applied a physical scaling diagnostic to decompose them into thermodynamic and dynamic contributions. We find that thermodynamics and dynamics have comparable contributions to the intensified precipitation extremes in the GM region. Changes in thermodynamic scaling contribute to a spatially uniform increase pattern, while changes in dynamic scaling dominate the regional differences in the increased precipitation extremes. Furthermore, the large inter-model spread of the projection is primarily attributed to variations of dynamic scaling among models.
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Fustos-Toribio, I., Manque-Roa, N., Vasquez Antipan, D., Hermosilla Sotomayor, M., & Gonzalez, V. L. (2022). Rainfall-induced landslide early warning system based on corrected mesoscale numerical models: an application for the southern Andes. Nat. Hazards Earth Syst. Sci., 22(6), 2169–2183.
Abstract: Rainfall-induced landslides (RILs) are an issue in the southern Andes nowadays. RILs cause loss of life and damage to critical infrastructure. Rainfall-induced landslide early warning systems (RILEWSs) can reduce and mitigate economic and social damages related to RIL events. The southern Andes do not have an operational-scale RILEWS yet. In this contribution, we present a pre-operational RILEWS based on the Weather and Research Forecast (WRF) model and geomorphological features coupled to logistic models in the southern Andes. The models have been forced using precipitation simulations. We correct the precipitation derived from WRF using 12 weather stations through a bias correction approach. The models were trained using 57 well-characterized RILs and validated by ROC analysis. We show that WRF has strong limitations in representing the spatial variability in the precipitation. Therefore, accurate precipitation needs a bias correction in the study zone. We used accurate precipitation simulation and slope, demonstrating a high predicting capacity (area under the curve, AUC, of 0.80). We conclude that our proposal could be suitable at an operational level under determined conditions. A reliable RIL database and operational weather networks that allow real-time correction of the mesoscale model in the implemented zone are needed. The RILEWSs could become a support to decision-makers during extreme-precipitation events related to climate change in the south of the Andes.
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Jarpa, M., Rozas, O., Salazar, C., Baeza, C., Campos, J. L., Mansilla, H. D., et al. (2016). Comparison of the chemical precipitation, UV/H2O2 and Fenton processes to optimize removal of chronic toxicity from kraft mill effluents. Desalin. Water Treat., 57(30), 13887–13896.
Abstract: Secondary Treatment Effluents (STE) from Kraft mill effluents are discharged into aquatic ecosystems with high color and chronic toxicity contents owing to the recalcitrance of compounds in the effluents. The goal of the study was to evaluate the chemical precipitation, UV/H2O2, and the Fenton processes (H2O2/Fe2+) for chemical oxygen demand (COD) and for removing chronic toxicity from STE. A circumscribed central composite model and a response surface methodology were used to evaluate the effects of variables such as Al-2(SO4)(3), Fe(II), and H2O2 concentration and pH range for each treatment. The optimal conditions were 984.2mg Al-2(SO4)(3)/L and pH 5.2 for chemical precipitation; 51.4mM H2O2 and pH 5.1 for UV/H2O2; and 5.5mM Fe(II): 25mM H2O2 concentration and pH 2.8 for H2O2/Fe2+. Under such optimal conditions, COD removal was 84.7, 80.0, and 93.6%, with reaction times of 57, 75, and 10min for the chemical precipitation, UV/H2O2, and H2O2/Fe2+ methods, respectively. This study recorded chronic toxicity in STE and sludge formed during chemical precipitation with maximum reductions in percentages of Allometric Growth Rate (AGR) of 11.5 for STE without dilution (100%, p<0.05). For chemical precipitation sludge, the maximum reduction of AGR was 3.4% for a dilution of 75%. We concluded that all the assessed treatments effectively removed chronic toxicity in the treated effluents.
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Martinez-Villalobos, C., & Neelin, J. D. (2023). Regionally high risk increase for precipitation extreme events under global warming. Sci. Rep., 13, 5579.
Abstract: Daily precipitation extremes are projected to intensify with increasing moisture under global warming following the Clausius-Clapeyron (CC) relationship at about 7%/∘C
. However, this increase is not spatially homogeneous. Projections in individual models exhibit regions with substantially larger increases than expected from the CC scaling. Here, we leverage theory and observations of the form of the precipitation probability distribution to substantially improve intermodel agreement in the medium to high precipitation intensity regime, and to interpret projected changes in frequency in the Coupled Model Intercomparison Project Phase 6. Besides particular regions where models consistently display super-CC behavior, we find substantial occurrence of super-CC behavior within a given latitude band when the multi-model average does not require that the models agree point-wise on location within that band. About 13% of the globe and almost 25% of the tropics (30% for tropical land) display increases exceeding 2CC. Over 40% of tropical land points exceed 1.5CC. Risk-ratio analysis shows that even small increases above CC scaling can have disproportionately large effects in the frequency of the most extreme events. Risk due to regional enhancement of precipitation scale increase by dynamical effects must thus be included in vulnerability assessment even if locations are imprecise.
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Neelin, J. D., Martinez-Villalobos, C., Stechmann, S. N., Ahmed, F., Chen, G., Norris, J. M., et al. (2022). Precipitation Extremes and Water Vapor Relationships in Current Climate and Implications for Climate Change. Curr. Clim. Change Rep., 8(1), 17–33.
Abstract: Purpose of Review: Review our current understanding of how precipitation is related to its thermodynamic environment, i.e., the water vapor and temperature in the surroundings, and implications for changes in extremes in a warmer climate. Recent Findings: Multiple research threads have i) sought empirical relationships that govern onset of strong convective precipitation, or that might identify how precipitation extremes scale with changes in temperature; ii) examined how such extremes change with water vapor in global and regional climate models under warming scenarios; iii) identified fundamental processes that set the characteristic shapes of precipitation distributions. While water vapor increases tend to be governed by the Clausius-Clapeyron relationship to temperature, precipitation extreme changes are more complex and can increase more rapidly, particularly in the tropics. Progress may be aided by bringing separate research threads together and by casting theory in terms of a full explanation of the precipitation probability distribution.
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Zuniga-Barra, H., Ortega-Martinez, E., Toledo-Alarcon, J., Torres-Aravena, A., Jorquera, L., Rivas, M., et al. (2023). Potential Use of Microbially Induced Calcite Precipitation for the Biocementation of Mine Tailings. Minerals, 13(4), 506.
Abstract: Mining activities offer clear economic benefits for mineral-rich countries. However, mining operations can produce several environmental impacts. Many of these are associated with generating and managing mining waste known as tailings, which are typically stored in surface facilities. Windblown dust emissions from tailing deposits can cause severe damage to local ecosystems and adverse health effects for the surrounding population. Microbially induced calcite precipitation (MICP) can be used for the superficial biocementation of tailings, thereby preventing such emissions. This research studied the capacity of MICP for the biocementation of tailings. The effect of applying different doses of biocementation reagents and two different methods for their application were evaluated. Results show that a relevant increase in surface strength can be achieved, especially if reagents are mechanically mixed with the tailings to induce a more homogeneous distribution of precipitates. Micrographical and mineralogical analysis by SEM, FTIR and XRD analysis showed the precipitation of calcium in the form of anorthite, calcite or vaterite. Overall results indicate that calcite precipitation can be induced in tailing by microorganisms with urease activity, providing a potential technique for the biocementation of this material.
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Zuniga-Barra, H., Toledo-Alarcon, J., Torres-Aravena, A., Jorquera, L., Rivas, M., Gutierrez, L., et al. (2022). Improving the sustainable management of mining tailings through microbially induced calcite precipitation: A review. Miner. Eng., 189, 107855.
Abstract: Mining activities offers evident potential economic benefits for mineral rich countries. However, mining operations can produce a series of environmental impacts. Many of them are associated with the generation and management of tailings. Biogeochemical processes have potential to modify the properties of particulate solids, such as tailings. Microbial induced calcite precipitation (MICP) is probably the most studied biogeochemical process. It promotes calcite precipitation, as a result of biological activity of different microorganisms. Available research indicates that MICP is a tool that has the potential to contribute to a more sustainable management of tailing deposits. Indeed, MICP have been reported as a technology suitable for removal and/or immobilization of heavy metals, creation of impermeable barriers, prevention of soil liquefaction and control of windblown dust emissions. However, several challenges still need to be addressed to enable relible full-scale implementation, requiring research in the near future. These are consideration of the particular chemical composition of tailings, reduction of urea requirements, determination of optimal reagents dosage, evaluation of the long term stability of the treatment and calculation of costs associated to ecah particular application.
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