DSpace Angular :: Browsing by Author "Bonilla, Carlos A."

Browsing by Author "Bonilla, Carlos A."

Now showing 1 - 15 of 15

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.
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.
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.
Changes in macroaggregate stability as a result of wetting/drying cycles of soils with different organic matter and clay contents
(2024) Melej, Maria Jesus; Acevedo, Sara E.; Contreras, Cristina P.; Giraldo, Carolina, V; Maurer, Tessa; Calderon, Francisco J.; Bonilla, Carlos A.
The wetting-drying (WD) cycles, caused by natural or anthropogenic processes such as rainfall or irrigation, can affect many soil properties. Among these properties, soil aggregate stability has been introduced as a convenient soil health indicator because of its relation to the soil's primary particles (sand, silt, and clay) and organic matter content (OM). However, previous studies have shown erratic effects depending on soil type and WD cycle setup when measuring aggregate stability. Therefore, this study aimed to characterize the soil primary particles composition and organic matter (OM) content of macroaggregates and measure the effects of WD cycles on aggregate stability. A series of soils with distinctive properties, such as OM and clay contents from five different USDA textural classes (loam, sandy loam, silty clay loam, silty loam, and clay loam) were used. Particle size distribution, OM, and mass fraction were measured in three aggregate size classes (2-1 mm, 1-0.5 mm, and 0.5-0.25 mm), and isolated aggregates were exposed to 3, 6, and 12 wetting and drying cycles. The main results indicate that soils with a high OM content have macroaggregates with finer particles, and the OM in soils is linearly related to the macroaggregate OM content. For 2-1 mm aggregates, a statistically significant reduction (p < 0.05) of water-stable aggregates compared to the control sample (0 cycles) was observed for every cycle, with reduction values between 4.8-7.3 %. An increase was observed only between 6-12 cycles (1.84 %). Additionally, statistically significant reductions were observed after the first three cycles in 1-0.5 mm aggregates and the first six in 0.5-0.25 mm aggregates. Finally, the macroaggregates were more resistant to the WD cycles when their clay and OM contents increased or the soil pH decreased. This study provides high-resolution results of macroaggregate particle size distribution and OM. It relates them to the effects of WD cycles in water-stable aggregates and soils with different land uses.
Effect of data availability and pedotransfer estimates on water flow modelling in wildfire-affected soils
(2023) Acevedo, Sara E.; Martinez, Sofia I.; Contreras, Cristina P.; Bonilla, Carlos A.
Understanding the impact of wildfires on soils exposed to fire is critical, especially in the current climate sce-nario, where an increase in the occurrence of wildfires is expected. Near-surface soil physical properties are affected by temperature increases caused by wildfires; therefore, changes in the soil water retention curve (SWRC) are expected. Parameters describing the SWRC can be obtained either by measuring or deriving using pedotransfer functions (PTF). However, PTFs have been developed using data from agricultural soils without major heating events; therefore, it is uncertain whether the estimation of parameters in fire-affected soils is reliable. This study evaluated changes in the hydraulic properties of near-surface soil due to fire during three wildfire events of different magnitudes. The objectives were: a) to identify changes in soil properties and SWRC due to wildfires, b) to assess the PTF performance (Rosetta versions 1, 2, and 3) of non-affected and fire-affected soils and (c) to evaluate changes in SWRC due to wildfires and water flow behavior changes through modelling using the HYDRUS-1D model. Decreases in organic matter (OM) and Ksat and increases in pH and bulk density (BD) were observed in fire-affected soils compared to non-affected soils. Based on sand, silt, clay, bulk density, and field capacity, Rosetta version 1 had the lowest values of root-mean-square error for the entire range of suctions, although it did not accurately estimate theta s or Ksat. Among Rosetta's estimations, Ksat showed the highest variations, which were more marked in fire-affected soils, when measured values were 15.85 cm d-1 while those estimated were 79.14 cm d-1 on average. The implications for hydrologic modelling were translated into lower annual water content and higher infiltration when using Rosetta inputs compared to inputs based on the measured SWRC.
Effects of soil heating changes on soil hydraulic properties in Central Chile
(2024) Giraldo, Carolina V.; Acevedo, Sara E.; Contreras, Cristina P.; Santibanez, Fernando; Saez, Esteban; Calderon, Francisco J.; Bonilla, Carlos A.
Wildfires are natural phenomena for most ecosystems on Earth. Many soil properties are impacted by fire, including soil hydraulic properties. We used a laboratory experiment to replicate the temperatures reached by a natural wildfire and documented the effects on soil hydraulic properties. This study hypothesizes that the impact of heating on soil hydrological properties can be explained by the interaction of a number of variables especially organic matter content (OM), cation exchange capacity (CEC), texture, pH, and electrical conductivity (EC). The main objective of this study is to explore the interconnections between soil hydraulic, chemical, and physical properties, focusing on understanding how these relationships change across different ecoregions and temperatures. Sixteen soils were collected across 16 sites susceptible to forest fires in the Central Zone of Chile and heated to 100 degrees C and 300 degrees C for two hours. These sites were representative of two distinct ecoregions: the Chilean Matorral (CM) and the Valdivian Temperate Forests (VTF). Chemical, physical, and hydraulic soil properties were measured before and after heating. At 100 degrees C, there were no significant changes in chemical, physical, or hydraulic soil properties. At 300 degrees C, significant changes were observed in most soil properties in soils from both ecoregions. The OM content and CEC decreased, whereas pH and electrical conductivity increased. In addition, clay content and water aggregate stability (WSA) decreased, while all hydraulic properties increased their values. The aforementioned results demonstrate that infiltration increased after the soil was heated. This can be attributed primarily to decreases in clay content. At the same time, the water repellency (R) index decreased, allowing water to more easily wet the soil particles. Correlations revealed that CEC and clay are the main factors ruling soil hydraulic properties at all temperatures. Clay mineralogy also contributes to the soil hydraulic behavior observed. Nonlinear models were developed to estimate hydraulic properties at 100 degrees C and 300 degrees C, using the main soil properties. The models illustrated that the soils of the CM ecoregion, which are characterized by lower OM and influence of clay/CEC ratio, would be less affected by fire compared to the soils of VTF. The water holding capacity would decrease in both ecoregions. However, due to the greater changes in OM and clay in VTF, the impact would be greater than in CM.1
Environmental controls and long-term changes on carbon stocks under agricultural lands
(2019) Ramirez, Paulina B.; Calderon, Francisco J.; Fonte, Steven J.; Bonilla, Carlos A.
Improved understanding of changes in soil organic carbon (SOC) stocks is critical for developing strategies that ensure effective climate change mitigation and the long-term productivity. Changes in SOC are likely to vary across soil and climate conditions, yet long-term data to elucidate these trends across different ecosystems remains limited. In this study we evaluated long-term changes in SOC across a gradient of climate conditions (from arid to hyper humid), soil orders, and land uses (non-cultivated, woody perennial, and cultivated) in central Chile. Thus, we sought to find evidence for SOC changes in the agricultural lands over past three or four decades. Surface soils (8-29 cm depth) were sampled between 2014 and 2016 and analyzed for total C and N content, aggregate stability, texture, bulk density, pH as well as spectral properties using Mid-infrared (MidIR) and Near-infrared spectroscopy. SOC stocks were compared to those previously measured at the same sites between 1968 and 1994, covering a wide range of SOC values (from 12 Mg C ha(-1) to 128 Mg C ha(-1)). Our findings show that the largest SOC losses occurred in semiarid and subhumid areas for the time frame considered, decreasing from their initial C stocks by 24.7% and 26.1%, respectively. Moreover, cultivated soils in semiarid regions were more vulnerable than those in arid regions to SOC losses. The results also indicated that in cooler and humid regions, SOC stocks were stable or increased over time. Among soil orders, Mollisols showed the largest losses (29.9% reduction between sampling dates). The MidIR results indicate that the mineral bands for clays and silicates were associated with these sites demonstrating SOC conservation, suggesting that mineral protection played an important role in the long-term SOC storage in semiarid areas. This study provides a better understanding of temporal changes of SOC to address the restoration of degraded land and adaptation for future trends in global change.
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.
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.
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.
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.
Testing the Wisconsin Phosphorus Index with Year-Round, Field-Scale Runoff Monitoring
(2012) Good, Laura W.; Vadas, Peter; Panuska, John C.; Bonilla, Carlos A.; Jokela, William E.
The Wisconsin Phosphorus Index (WPI) is one of several P indices in the United States that use equations to describe actual P loss. processes. Although for nutrient management planning the WPI is reported as a dimensionless whole number, it is calculated as average, annual dissolved P (DP) and particulate P (PP) mass delivered per unit area. The WPI calculations use soil P concentration, applied manure and fertilizer P, and estimates of average annual erosion and average annual runoff. We compared WPI estimated P losses to annual P loads measured in surface runoff from 86 field-years on crop fields and pastures. As the erosion and runoff generated by the weather in the monitoring years varied substantially from the average annual estimates used in the WPI, the WPI and measured loads were not well correlated. However, when measured runoff and erosion were used in the WPI field loss calculations, the WPI accurately estimated annual total P loads with a Nash-Sutcliffe Model Efficiency (NSE) of 0.87. The DP loss estimates were not as close to measured values (NSE = 0.40) as the PP loss estimates (NSE = 0.89). Some errors in estimating DP losses may be unavoidable due to uncertainties in estimating on-farm manure P application rates. The WPI is sensitive to field management that affects its erosion and runoff estimates. Provided that the WPI methods for estimating average annual erosion and runoff are accurately reflecting the effects of management, the WPI is an accurate field-level assessment tool for managing runoff P losses.
The R package infiltrodiscR: A package for infiltrometer data analysis and an experience for improving data reproducibility in soil physics
(2024) V. Giraldo, Carolina; Acevedo, Sara E.; Bonilla, Carlos A.
This paper discusses the interest in utilizing R, a programming language, in soil physics for enhanced data reproducibility. Reproducibility is challenging across scientific disciplines, including soil science, and it is encouraged by demands for transparency from funding bodies and governments. Open and reproducible soil physics research can benefit the scientific community. With a focus on open science practices, the authors developed {infiltrodiscR}, leveraging existing R knowledge in soil physics. The package facilitates analysis of infiltration data, demonstrated through analysing changes in infiltration using published data. Results align with previous findings, showcasing {infiltrodiscR}'s potential in promoting reproducibility in soil science research.
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.
WATER EROSION PREDICTION USING THE REVISED UNIVERSAL SOIL LOSS EQUATION (RUSLE) IN A GIS FRAMEWORK, CENTRAL CHILE
(2010) Bonilla, Carlos A.; Reyes, Jose L.; Magri, Antoni
Soil erosion is a growing problem in Central Chile, particularly in coastal dry lands, where it can significantly decrease the productivity of rainfed agriculture and forestry. In this study, the Revised Universal Soil Loss Equation (RUSLE) was integrated into a Geographic Information System (GIS), and used to evaluate the effects of different combinations of vegetative cover on soil erosion rates for Santo Domingo County in Central Chile. Implementing RUSLE in the GIS required a complete description of the county's soils, climate, topography and current land use/land cover. This information was compiled in rasters of 25 x 25 m cells. RUSLE parameter values were assigned to each cell and annual soil loss estimates were generated on a cell by cell basis. Soil losses were estimated for the current and for three alternate scenarios of vegetative cover. Under current conditions, 39.7% of the county is predicted to have low erosion rates ( 0.1 t ha(-1) yr(-1)), 39.8% has intermediate rates (0.1-1.0 t ha(-1) yr(-1)), and 10.4% has high erosion rates (> 1.1 t ha(-1) yr(-1)). The remainder of the surface (10.2%) is not subject to erosion. Under the recommended alternate scenario, 89.3% of the county is predicted to have low erosion rates, and no areas are affected by high soil loss, reducing soil erosion to a level that will not affect long term productivity. This paper describes how RUSLE was implemented in the GIS, and the methodology and equations used to evaluate the effects of the land use/land cover changes.

Browsing by Author "Bonilla, Carlos A."

Results Per Page

Sort Options