Estimation of the Radon Risk Under Different European Climates and Soil Textures.

Radon is a radioactive gas produced from the natural radioactive decay of uranium and is found in almost all rocks and soils. In confined places (e.g., dwellings, workplaces, caves, and underground mines), radon may accumulate and become a substantial health risk since it is considered the second most important cause of lung cancer in many developed countries. Radon risk assessment commonly considers either field or estimate values of the radon concentration and the gas permeability of soils. However, radon risk assessment from single measurement surveys to radon potential largescale mapping is strongly sensitive to the soil texture variability and climate changes, and particularly, to the soil water content dynamic and its effect on soil gas permeability. In this paper, the gas permeability of soils, and thus, the estimation of radon risk, is studied considering the effect of three different climates following the Köppen classification and four soil textures on soil water content dynamics. This investigation considers the CLIGEN weather simulator to elaborate 100-year length climatic series; Rosseta 3 pedotransfer function to calculate soil hydraulics parameters, and the HYDRUS-1D software to model the dynamics of water content in the soil. Results reveal that climate strongly affects gas permeability of soils and they must be considered as an additional factor during the evaluation of radon exposure risk. The impact of climate and texture defines the soil water content dynamic. Coarse soils show smaller gas permeability variations and then radon risk, in this case, is less affected by the climate type. However, in clay soils, the effect of climate and the differences in soil water content derive in gas permeability variations between 100 and 1,000 times through an annual cycle. As a result, it may cross the boundary between two radon risk categories. Results deeply confirm that both climate and texture should be compulsory considered when calculating the radon exposure risk and in the definition of new strategies for the elaboration of more reliable geogenic radon potential largescale maps.

Land-use changes and precipitation cycles to understand hydrodynamic responses in semiarid Mediterranean karstic watersheds.

Non-planned agricultural land abandonment is affecting natural hydrological processes. This is especially relevant in vulnerable arid karstic watersheds, where water resources are scarce but vital for sustaining natural ecosystems and human settlements. However, studies assessing the spatiotemporal evolution of the hydrological responses considering land-use changes and precipitation cycles for long periods are rare in karstic environments. In this research, we selected a representative karstic watershed in a Mediterranean semiarid domain, since in this belt, karst environments are prone to land degradation processes due to human impacts. Geographic Information Systems-based tools and hydrological modeling considering daily time steps were combined with temporal analysis of climate variables (wavelet analysis) to demonstrate possible interactions and vulnerable responses. Observed daily flow data were used to calibrate/validate these hydrological models by applying statistic indicators such as the NSE efficiency and a self-developed index (the ANSE index). This new index could enhance goodness-of-fit measurements obtained with traditional statistics during the model optimization. We hypothesize that this is key to adding new inputs to this research line. Our results revealed that: i) changes in the type of sclerophyllous vegetation (Quercus calliprinos, ilex, rotundifolia, suber, etc.) from 81.5% during the initial stage (1990) to natural grasslands by 81.6% (2018); and, ii) decreases in agricultural areas (crops) by approximately 60% and their transformation into coniferous forests, rock outcrops, sparsely natural grasslands, etc. in the same period. Consequently, increases in the curve number (CN) rates were identified as a result of land abandonment. As a result, an increase in peak flow events jointly with a relevant decrease of the average flow rates (water scarcity) in the watershed was predicted by the HEC-HMS model and verified through the observed data. This research provides useful information about the effects of anthropogenic changes in the hydrodynamic behaviour of karstic watersheds and water resource impacts, especially key in water-scarce areas that depict important hazards for the water supply of related populations and natural ecosystems.

Effectiveness of two lightweight aggregates for the removal of heavy metals from contaminated urban stormwater.

Contaminated runoff stormwater from urban environments carries several contaminants to water bodies, thereby affecting the health of living beings and ecological systems. Among all the contaminants, heavy metals possess high toxicity and impact water quality. The stormwater management through green infrastructures composed by adequate materials can provide an excellent solution, simultaneously ensuring the appropriate hydraulic performance and contaminant removal rate. The proposed research aims at the elimination of heavy metals (i.e. Ni, Cu, Zn, Cd and Pb) through column experiments by selecting four possible and novel treatments for urban stormwaters. Two lightweight aggregates (Arlita and Filtralite) were tested separately and in combination with CaCO3. The study determines the efficiency and lifetime of each treatment by varying the interaction time between the filter materials and contaminated water and the type of filter. The observed removal mechanisms were closely related to the changes in pH due to the interactions between water and different materials. The reductions in heavy metal concentrations depend on the type of heavy metal, interaction time and type of filter material. Results indicate that the combined use of CaCO3, Arlita and Filtralite did not improve the removal rates of heavy metals. However, it decreased the efficiency of the decontamination process. The significance of this study lies on the removal efficiency of Arlita and Filtralite as decontamination treatments. Both the tested lightweight aggregates led to a considerable decrease in the heavy metal concentrations in urban runoff stormwater although Filtralite was particularly efficient. After 4 weeks, the treatments were still successfully reducing and stabilising 99% of the heavy metals in the contaminated stormwater. These results confirm that the lifetime of the tested lightweight aggregates is adequate and emphasise, as a novel application of these materials, on their feasibility for the improvement of urban stormwater quality.

Remediation by waste marble powder and lime of jarosite-rich sediments from Portman Bay (Spain).

We investigate the use of hydrated lime and calcite waste marble powder as remediation treatments of contaminated jarosite-rich sediments from Portman Bay (SE, Spain), one of the most contaminated points in the Mediterranean coast by mining-metallurgical activities. We tested two commercial hydrated limes with different Ca(OH)2 percentages (28 and 60% for Lime-1 and Lime-2 respectively) and two different waste marble powder, WMP, from the marble industry (60 and 96% of calcite for WMP-1 and WMP-2 respectively). Mixture and column experiments and modelling of geochemical reactions using PHREEQC were performed. Lime caused the precipitation of hematite, gypsum and calcite, whereas WMP treatments formed iron carbonates and hematite. The fraction of amorphous phases was mainly composed of iron oxides, hydroxides and oxyhydroxides that was notably higher in the lime treatment in comparison to the WMP treatment. The reactive surface area showed a positive trend with the amorphous phase concentration. Results highlighted the effectiveness of lime treatments, where Lime-2 showed a complete elimination of jarosite. Column experiments revealed a clear reduction of heavy metal concentration in the lixiviate for the treated sediments compared to the original sediments. Particularly, Lime-2 showed the highest reduction in the peak concentration of Fe, Mn, Zn and Cd. The studied treatments limited the stabilisation of Cr and Ni, whereas contrarily As increases in the treated sediment. PHREEQC calculations showed that the most concentrated heavy metals (Zn and Mn) are stabilized mainly by precipitation whereas Cu, Pb and Cd by a combination of precipitation and sorption processes. This chemical environment leads to the precipitation of stable iron phases, which sorb and co-precipitate considerable amounts of potentially toxic elements. Lime is significantly more effective than WMP, although it is recommended that the pH value of the mixture should remain below 9 due to the amphoteric behaviour of heavy metals.

Estimation of soil gas permeability for assessing radon risk using Rosetta pedotransfer function based on soil texture and water content.

Radon is a natural source of radioactivity and it can be found in all soils and rocks in the Earth. The presence of radon gas in indoor environments implies a serious risk for human health, already listed as carcinogenic by the World Health Organization. The most relevant methods to infer the risk for radon exposure are based on soil radon concentration and gas permeability that describe the effective radon movement in the soil. However, they neglect crucial soil properties and water content in soil, which can affect greatly soil permeability to gases. Additionally, soil permeability measurement remains expensive, difficult and time-consuming. In this paper we show a new and simple methodology to infer radon risk based on Rosetta3 pedotransfer function as well as soil texture and water content. We also determine the influence of soil texture both on the gas permeability variation in dependence on water content and on the parameter n of the van Genuchten -Mualem model, which establishes the shape of the relative permeability curves. We show that radon risk exposure may change importantly for the same soil with different soil water contents. We finally apply and validate the proposed method using radon permeability data from the Canadian component of the North American Soil Geochemical Landscapes Project (NASGLP). Results highlight that the proposed methodology provides reliable estimations of the gas permeability and reveal that the presence of water content may cross the boundary between two radon risk categories, and consequently, may change the radon risk category to safer situations.

Impact of land use changes on flash flood prediction using a sub-daily SWAT model in five Mediterranean ungauged watersheds (SE Spain).

Flash floods cause severe natural disasters over the world generating property and infrastructures damages, poverty and loss of human life, among others. Mediterranean coastal watersheds are specially sensible to flash floods effects due to their typical drainage basin features (steep slopes, short concentration times, complex orography, etc.) and the high rainfall intensity typical of convective systems. In the present study, the temporal evolution of the hydrological answer in five Mediterranean (SE Spain) ravine basins with sizes from 10.2 km2 to 200.9 km2 were analysed. A sub-daily SWAT model was used at watershed scale to capture the complex hydrological dynamics. Five land use scenarios corresponding to no-urbanization (baseline), 1990, 2000, 2006 and 2012 were evaluated using GIS-based tools. Additionally, statistical significant differences among the studied scenarios were checked employing the Kruskal-Wallis and post-hoc tests based on Mann-Whitney test with BH correction. Our results show that flash flood risks have increased in the studied catchments due to changes in land uses, particularly affected by a large urban growth. Observed changes in soil uses have been important since the sixties of the last century, because of a high demographic and touristic pressure and specially the urban area has enhanced considerably during the last 22 years. Currently, some of these catchments present around 70% of their surface occupied by urban land uses with high population density producing curve number surpasses 85 and 90 levels. The hydrological response of the studied basins changed to higher flow rate peaks and shorter concentration times. Some discharges increased significantly from the baseline land use scenario (≈50 m3/s, 190 m3/s, 380 m3/s) to the most urbanised scenario (≈235 m3/s, 385 m3/s, 940 m3/s), respectively. These findings provide to urban planning policy makers very useful information in the face of flash flood effects, which have cost even human lifes in the studied ravine basins during last years.

MATLAB algorithm to implement soil water data assimilation with the Ensemble Kalman Filter using HYDRUS.

Data assimilation is becoming a promising technique in hydrologic modelling to update not only model states but also to infer model parameters, specifically to infer soil hydraulic properties in Richard-equation-based soil water models. The Ensemble Kalman Filter method is one of the most widely employed method among the different data assimilation alternatives. In this study the complete Matlab© code used to study soil data assimilation efficiency under different soil and climatic conditions is shown. The code shows the method how data assimilation through EnKF was implemented. Richards equation was solved by the used of Hydrus-1D software which was run from Matlab. •MATLAB routines are released to be used/modified without restrictions for other researchers•Data assimilation Ensemble Kalman Filter method code.•Soil water Richard equation flow solved by Hydrus-1D.

Vinasse application to sugar cane fields. Effect on the unsaturated zone and groundwater at Valle del Cauca (Colombia).

Extensive application of vinasse, a subproduct from sugar cane plantations for bioethanol production, is currently taking place as a source of nutrients that forms part of agricultural management in different agroclimatic regions. Liquid vinasse composition is characterised by high variability of organic compounds and major ions, acid pH (4.7), high TDS concentration (117,416-599,400mgL(-1)) and elevated EC (14,350-64,099µScm(-1)). A large-scale sugar cane field application is taking place in Valle del Cauca (Colombia), where monitoring of soil, unsaturated zone and the aquifer underneath has been made since 2006 to evaluate possible impacts on three experimental plots. For this assessment, monitoring wells and piezometers were installed to determine groundwater flow and water samples were collected for chemical analysis. In the unsaturated zone, tensiometers were installed at different depths to determine flow patterns, while suction lysimeters were used for water sample chemical determinations. The findings show that in the sandy loam plot (Hacienda Real), the unsaturated zone is characterised by low water retention, showing a high transport capacity, while the other two plots of silty composition presented temporal saturation due to La Niña event (2010-2011). The strong La Niña effect on aquifer recharge which would dilute the infiltrated water during the monitoring period and, on the other hand dissolution of possible precipitated salts bringing them back into solution may occur. A slight increase in the concentration of major ions was observed in groundwater (~5% of TDS), which can be attributed to a combination of factors: vinasse dilution produced by water input and hydrochemical processes along with nutrient removal produced by sugar cane uptake. This fact may make the aquifer vulnerable to contamination.