Browsing by Author "Bonilla, Carlos A."

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    A comparative study of soil metal concentrations in Chilean urban parks using four pollution indexes
    (2022) Vega, Alejandra; Arce, Guillermo; Rivera, Javier I.; Acevedo, Sara E.; Reyes Paecke, Sonia; Bonilla, Carlos A.; Pasten Gonzalez, Pablo Arturo; CEDEUS (Chile)
    Toxic metal enrichment in urban soils from natural and anthropogenic sources is a public health concern thatchallenges sustainable urban development. Active and legacy mining is likely a major contributor of localizedmetal pollution in resource-based economies, although other sources associated with industrial and trans-portation activities may also contribute in urban settings. In mining countries, such as Chile, with no soil qualityregulation, public policies that seek to protect human health should assess metal distribution and pollution in-dexes to guide interventions, especially in urban green spaces. To assess the role of active and legacy miningwaste sites within the urban and peri-urban areas, metal concentrations in the soils of urban parks weremeasured in this study, and four pollution indexes were calculated for four cities of Chile. Copiap ́o and Andacolloin northern Chile represented the cities with several active and legacy mining waste sites located within theurban and peri-urban areas, while conurbation La Serena-Coquimbo and Gran Santiago represented the cities inmining districts that lacked major mining waste sites within their urban perimeters. A total of 82 (Copiap ́o), 30(Andacollo), 26 (La Serena-Coquimbo), and 59 (Gran Santiago) composite surface soil samples were collectedfrom the urban parks. Considering Canadian guidelines for residential/parkland soils, the value for Cu (63 mg/kg) was found to be exceeded in 99%, 50%, 100%, and 97% of samples collected from Copiap ́o, La Serena-Coquimbo, Andacollo, and Gran Santiago, respectively. The guidelines for lead (140 mg/kg) and zinc (250mg/kg) were exceeded in less than 12% of samples collected from Copiap ́o and Gran Santiago. Arsenic was notmainly quantified (<10% quantification frequency, quantification limit = 36 mg/kg). The calculated modifiedpollution load, Nemerow, and soil quality indexes indicated that soils in the urban parks were more polluted incities with urban mine wastes, however, the pollution load index ranked higher metal pollution in Gran Santiago.This study presented the first comparative study of metals in urban parks of Chile, highlighting a large proportionof parks with soil copper concentrations above the international guidelines, while showing higher median values in cities containing urban mine waste disposal sites.
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    A new method of assessing water erosion risk in forest operations based on rainfall variability
    (UNIV AUSTRAL CHILE, FAC CIENCIAS FORESTALES, 2012) Contreras, Juan; Bonilla, Carlos A.; Troncoso, Juan
    Water erosion has been a major environmental problem associated to forest harvesting operations in humid and temperate climates. The incorporation of this factor in the decision making process has been complex due to the high variability observed in rainfall intensity and magnitude. This paper presents a methodology for incorporating the temporal variability of rainfall in the planning of forest operations. We used a monthly index based on the R-RUSLE erosivity factor. This index allows knowing the most likely value of soil loss and associating a confidence level. Thus, the forest planner has an estimate of erosion rates related to the operations, and an index that reflects the rainfall variability. With this methodology it is possible to identify, for a given level of soil loss, those months in which there is a higher uncertainty. This methodology was applied to a pine plantation in Santa Barbara, Biobio Region, Chile, where the rainfall erosivity ranges from 16 MJ mm ha(-1) h(-1) to 271 MJ mm ha(-1) h(-1) depending on the month of the year.
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    Arsenic occurrence in fluvial sediments: Challenges for planning sustainable water infrastructure in the Lluta river basin
    (2011) Rios, Paulina L.; Guerra, Paula A.; Bonilla, Carlos A.; Escauriaza, Cristian R.; Pizarro Puccio, Gonzalo Ernesto; Pasten, Pablo A.
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    Modeling changes to the hydrodynamic characteristics of agglomerated copper tailings
    (ELSEVIER, 2011) Fernanda Hernandez Lopez, Maria; Ortiz, Cristian; Bonilla, Carlos A.; Gironas, Jorge; Francisco Munoz, Jose
    This paper describes the effect of acid leaching on the hydrodynamic properties of agglomerated copper tailings. Both the suction and the hydraulic conductivity curves were obtained before and after acid application in laboratory columns under unsaturated flow conditions. Using a classical approach originally developed for water and soil, we determined whether the post-acid application characteristic curves could be obtained from the pre-acid application ones. Results showed that acid modified the hydrodynamic properties of agglomerated tailings. Both the macropore volume and the saturated hydraulic conductivity decreased. For the same water content, the unsaturated hydraulic conductivity decreased and the suction head increased. The pre-acid application characteristic curves can be used to estimate the corresponding post-acid application curves. (C) 2011 Elsevier B.V. All rights reserved.
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    Rainfall erosivity in Central Chile
    (ELSEVIER, 2011) Bonilla, Carlos A.; Vidal, Karim L.
    One of the most widely used indicators of potential water erosion risk is the rainfall-runoff erosivity factor (R) of the Revised Universal Soil Loss Equation (RUSLE). R is traditionally determined by calculating a long-term average of the annual sum of the product of a storm's kinetic energy (E) and its maximum 30-min intensity (130), known as the E130. The original method used to calculate Elm requires pluviograph records for at most 30-min time intervals. Such high resolution data is difficult to obtain in many parts of the world, and processing it is laborious and time-consuming. In Chile, even though there is a well-distributed rain gauge network, there is no systematic characterization of the territory in terms of rainfall erosivity. This study presents a rainfall erosivity map for most of the cultivated land in the country. R values were calculated by the prescribed method for 16 stations with continuous graphical record rain gauges in Central Chile. The stations were distributed along 800 km (north-south), and spanned a precipitation gradient of 140-2200 mm yr(-1). More than 270 years of data were used, and 5400 storms were analyzed. Additionally, 241 spatially distributed R values were generated by using an empirical procedure based on annual rainfall. Point estimates generated by both methods were interpolated by using kriging to create a map of rainfall erosivity for Central Chile. The results show that the empirical procedure used in this study predicted the annual rainfall erosivity well (model efficiency = 0.88). Also, an increment in the rainfall erosivities was found as a result of the rainfall depths, a regional feature determined by elevation and increasing with latitude from north to south. R values in the study area range from 90 MJ mm ha(-1) h(-1) yr(-1) in the north up to 7375 MJ mm ha(-1) h(-1) yr(-1) in the southern area, at the foothills of the Andes Mountains. Although the map and the estimates could be improved in the future by generating additional data points, the erosivity map should prove to be a good tool for land-use planners in Chile and other areas with similar rainfall characteristics. (C) 2011 Elsevier B.V. All rights reserved.
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    Soil erodibility mapping and its correlation with soil properties in Central Chile
    (ELSEVIER SCIENCE BV, 2012) Bonilla, Carlos A.; Johnson, Odette I.
    In the Revised Universal Soil Loss Equation (RUSLE), erodibility accounts for the influence of soil properties on soil loss during storm events in upland areas, which is represented by the soil erodibility factor (K). K-factor values are best obtained from long-term direct measurements on natural runoff plots; however, in the absence of field tests, these values can be estimated using relationships based on physical and chemical soil properties. Soil erosion by water is a major concern in Central Chile, and the application of many prediction technologies, such as the RUSLE, is limited due to the lack of information about erodibility factors. Because the direct measurement of K-factor values requires long-term erosion plot studies, the objective of this research was to use existing soil survey data to provide a first approximation of soil erodibility in the region and examine its relationship to soil properties in Central Chile. Erodibility values for a large variety of soil types and surface conditions (535 soil series) were calculated in this study, providing the first soil erodibility map for most of the country's cultivated land areas. Erodibility factors were calculated using two alternative relationships based on physical and chemical properties of surface soils. Results showed that the average K-factor value in the study area was 0.039 +/- 0.011 t ha h ha(-1) MJ(-1) mm(-1), and 67% of soils had values between 0.03 and 0.05 t ha h ha(-1) MJ(-1) mm(-1). The erodibility factors did not show a pattern with latitude or longitude mainly due to the lack of trends in the soil properties within the study area. Soil erodibility increased with silt content (r=0.607), and soil textures that contained predominantly silt as the primary particles were estimated to be the most vulnerable to water erosion. Organic matter content was not correlated to soil erodibility (r=0.086), and Mollisols and Entisols were the two only taxonomic orders that showed different erodibilities. The results of this study demonstrated the convenience of using silt content instead of clay, organic matter, or taxonomic order in preliminary classifications of water erosion vulnerability in Central Chile or areas with similar soil characteristics. (C) 2012 Elsevier B.V. All rights reserved.
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    Testing a Grid-Based Soil Erosion Model across Topographically Complex Landscapes
    (SOIL SCI SOC AMER, 2008) Bonilla, Carlos A.; Norman, John M.; Molling, Christine C.; Karthikeyan, K. G.; Miller, Paul S.
    This study was conducted to evaluate the overall performance of the Precision Agricultural-Landscape Modeling System (PALMS) for calculating runoff and soil loss under cropped conditions. The PALMS model uses a lognormal distribution of saturated hydraulic conductivity across the fields to simulate typical soil heterogeneity within soil texture classes. Runoff and soil loss data were collected in three farm fields for a total of 75 runoff events during 2 yr under six cropping scenarios (alfalfa [Medicago sativa L.] and corn [Zed mays L.] no-tilled, corn and soybean [Glycine max (L.) Merr.] moldboard plowed, and alfalfa and corn chisel plowed). For individual storms, calculated runoff and sediment loss from PALMS were compared with corresponding measurements for each farm during the entire cropping season. The coefficient of determination (r(2)) between runoff calculations and measurements was 0.84. The r(2) between soil loss calculations and measurements with the storm-by-storm simulations during both seasons was 0.78. Based on these continuous simulation results, the PALMS calculations appear to have lower relative errors with large events than small events, a desirable result because large events are most important in assessing the environmental consequences of management practices.
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    Water erosion estimation in topographically complex landscapes: Model description and first verifications
    (SOIL SCI SOC AMER, 2007) Bonilla, Carlos A.; Norman, John M.; Molling, Christine C.
    Two of the most important limitations when predicting soil movement are the natural complexity and the spatial heterogeneity of the processes. Sod erosion can vary significantly across short distances as a function of local soil properties and microtopography; but regardless of this, many erosion models assume homogeneity in topography and soil characteristics. The objective of this research was to develop a method for estimating soil loss from agricultural fields that is faithful to the complex topography and spatial heterogeneity common to managed landscapes. Sediment loss for individual storms was achieved by linking sod detachment-deposition equations adapted from the Water Erosion Prediction Project (WEPP) model to the existing water-flow subroutine in the Precision Agricultural-Landscape Modeling System (PALMS). In PALMS, sediment was routed appropriately in a two-dimensional grid, defining the pathways taken by the eroded material. Usually PALMS works on a grid-cell size of 5 to 20 m and simulates runoff and sod erosion patterns as affected by slope, soil texture, anisotropic surface roughness, soil consolidation, canopy cover, and tillage interactions with topography. In this study, PALMS and WEPP were used to simulate the sediment transport on an idealized field with a complex hillslope profile. Both models showed a consistent soil loss pattern and only minor differences in transport capacities. The models were also compared with data from actual erosion Plots, where both runoff and soil loss were predicted with similar errors for both PALMS and WEPP To illustrate the capability of PALMS, it was applied to a field with complex topography.