Nitrate increases the capacity of an aerobic moving-bed biofilm reactor (MBBR) for winery wastewater treatment.

We used bench-scale tests and mathematical modeling to explore chemical oxygen demand (COD) removal rates in a moving-bed biofilm reactor (MBBR) for winery wastewater treatment, using either urea or nitrate as a nitrogen source. With urea addition, the COD removal fluxes ranged from 34 to 45 gCOD/m2-d. However, when nitrate was added, fluxes increased up to 65 gCOD/m2-d, twice the amount reported for aerobic biofilms for winery wastewater treatment. A one-dimensional biofilm model, calibrated with data from respirometric tests, accurately captured the experimental results. Both experimental and modelling results suggest that nitrate significantly increased MBBR capacity by stimulating COD oxidation in the deeper, oxygen-limited regions of the biofilm. Our research suggests that the addition of nitrate, or other energetic and broadly used electron acceptors, may provide a cost-effective means of covering peak COD loads in biofilm processes for winery or another industrial wastewater treatment.

Toward sustainability and resilience in Chilean cities: Lessons and recommendations for air, water, and soil issues.

Achieving sustainability and resilience depends on the conciliation of environmental, social, and economic issues integrated into a long-term perspective to ensure communities flourish. Many nations are transitioning toward both objectives, while at the same time addressing structural concerns that have not allowed them to look after the environment in the past. Chile is one of these nations dealing with such challenges within a particular administrative context, an increasing environmental awareness, and a set of unique and complex geophysical boundaries that impose a plethora of hazards for cities, ecosystems, and human health. This paper presents recent accomplishments and gaps, mostly from an environmental perspective, on issues related to air pollution, the urban water cycle, and soil contamination, in the path being followed by Chile toward urban sustainability and resilience. The focus is on the bonds between cities and their geophysical context, as well as the relationships between environmental issues, the built environment, and public health. The description and diagnosis are illustrated using two cities as case studies, Temuco and Copiapó, whose socioeconomic, geographical, and environmental attributes differ considerably. Particulate matter pollution produced by the residential sector, drinking water availability, wastewater treatment, stormwater management, and soil contamination from the mining industry are discussed for these cities. Overall, the case studies highlight how tackling these issues requires coordinated actions in multiple areas, including regulatory, information, and financial incentive measures. Finally, the policy analysis discusses frameworks and opportunities for Chilean cities, which may be of interest when conceiving transitional paths toward sustainability and resilience for other cities elsewhere.

Perchlorate and chlorate assessment in drinking water in northern Chilean cities.

Perchlorate and chlorate are endocrine disruptors considered emerging contaminants (ECs). Both oxyanions are commonly associated with anthropogenic contamination from fertilizers, pesticides, explosives, and disinfection byproducts. However, the soils of the Atacama Desert are the most extensive natural reservoirs of perchlorate in the world, compromising drinking water sources in northern Chile. Field campaigns were carried (2014-2018) to assess the presence of these ECs in the water supply networks of twelve Chilean cities. Additionally, the occurrence of perchlorate, chlorate and other anions typically observed in drinking water matrices of the Atacama Desert (i.e., nitrate, chloride, sulfate) was evaluated using a Spearman correlation analysis to determine predictors for perchlorate and chlorate. High concentrations of perchlorate (up to 114.48 µg L-1) and chlorate (up to 9650 µg L-1) were found in three northern cities. Spatial heterogeneities were observed in the physicochemical properties and anion concentrations of the water supply network. Spearman correlation analysis indicated that nitrate, chloride, and sulfate were not useful predictors for the presence of perchlorate and chlorate in drinking water in Chile. Hence, this study highlights the need to establish systematic monitoring, regulation, and treatment for these EC of drinking water sources in northern Chilean cities for public health protection.

Global assessment of chemical quality of drinking water: The case of trihalomethanes.

BACKGROUND: Trihalomethanes (THM), a major class of disinfection by-products, are widespread and are associated with adverse health effects. We conducted a global evaluation of current THM regulations and concentrations in drinking water. METHODS: We included 120 countries (∼7000 million inhabitants in 2016), representing 94% of the world population. We searched for country regulations and THM routine monitoring data using a questionnaire addressed to referent contacts. Scientific and gray literature was reviewed where contacts were not identified or declined participation. We obtained or estimated annual average THM concentrations, weighted to the population served when possible. RESULTS: Drinking water regulations were ascertained for 116/120 (97%) countries, with 89/116 (77%) including THM regulations. Routine monitoring was implemented in 47/89 (53%) of countries with THM regulations. THM data with a varying population coverage was obtained for 69/120 (58%) countries consisting of ∼5600 million inhabitants (76% of world's population in 2016). Population coverage was ≥90% in 14 countries, mostly in the Global North, 50-89% in 19 countries, 11-49% among 21 countries, and ≤10% in 14 countries including India, China, Russian Federation and Nigeria (40% of world's population). DISCUSSION: An enormous gap exists in THM regulatory status, routine monitoring practice, reporting and data availability among countries, especially between high- vs. low- and middle-income countries (LMICs). More efforts are warranted to regulate and systematically assess chemical quality of drinking water, centralize, harmonize, and openly report data, particularly in LMICs.

Challenges and opportunities for drinking water treatment residuals (DWTRs) in metal-rich areas: an integrated approach.

The physicochemistry and production rate of drinking water treatment residuals (DWTRs) depends on the raw water composition and the plant operational parameters. DWTRs usually contain Fe and/or Al oxyhydroxides, sand, clay, organic matter, and other compounds such as metal(oids), which are relevant in mining countries. This work proposes a simple approach to identify DWTRs reuse opportunities and threats, relevant for public policies in countries with diverse geochemical conditions. Raw water pollution indexes and compositions of DWTRs were estimated for Chile as a model case. About 23% of the raw drinking water sources had moderate or seriously contamination from high turbidity and metal(loid) pollution If the untapped reactivity of clean DWRTs was used to treat resources water in the same water company, the 73 and 64% of these companies would be able to treat water sources with As and Cu above the drinking water regulations, respectively. Integrating plant operational data and the hydrochemical characteristics of raw waters allows the prediction of DWTRs production, chemical composition, and reactivity, which is necessary to identify challenges and opportunities for DWTRs management.

Empatía y declinación empática por curso y sexo en estudiantes de enfermería / Empathy and Empathic Decline by Academic Year and Sex in Nursing Students

Introducción: La empatía es un atributo importante en la comunicación entre el profesional de salud (médicos y enfermeras de todas las especialidades) y el paciente; permite la conexión intersubjetiva entre ellos y contribuye a una mejor atención, mayor adherencia al tratamiento, entre otros muchos beneficios. Dada la complejidad de la empatía, la formación de este atributo es una tarea que se debe asumir durante la formación de pregrado y no durante la formación de especialistas. Por lo tanto, los estudios de empatía, así como las intervenciones que pueden derivarse de un diagnóstico empático adecuado, deben realizarse precisamente en dicho nivel formativo. Objetivo: Determinar la presencia de declinación empática, atendiendo a las variables curso y sexo, sobre la base de los niveles de empatía y de sus dimensiones en estudiantes de enfermería. Métodos: Estudio exploratorio, transversal. Se estudiaron 166 estudiantes de un total poblacional de 188, utilizando la Escala de Empatía de Jefferson, estudiando las posibles diferencias en la empatía y sus componentes mediante pruebas no paramétricas. Resultados: No hubo diferencias en los componentes de la empatía en relación con la variable curso; sin embargo, la empatía (en general) si las tuvo. La empatía y los componentes no se diferenciaron en el sexo, con excepción de Toma de Perspectiva que fue mayor en mujeres. Conclusiones: Los niveles de empatía entre los cursos no fueron diferentes y no se manifestó la declinación empática. No existieron diferencias entre los sexos y solo el componente Toma de Perspectiva fue mayor en mujeres(AU)

Introduction: Empathy is an important attribute for communication between the health professional (doctors and nurses of all specialties) and the patient; it allows intersubjective connection between them and contributes to better care, greater adherence to treatment, among many other benefits. Given the complexity of empathy, educating this attribute is a task that must be assumed during undergraduate training and not during specialized training. Therefore, studies about empathy, as well as the interventions that can be derived from an adequate empathic diagnosis, must be carried out precisely at this training level. Objective: To determine the presence of empathic decline, with a focus on the variables academic years and sex, based on the levels of empathy and its dimensions in Nursing students. Methods: Exploratory and cross-sectional study carried out with 166 students, from a total population of 188. The Jefferson Empathy Scale was used. The possible differences in empathy and its components were studied using nonparametric tests. Results: There were no differences in the components of empathy regarding the variable academic year; however, empathy, in general, did have differences. Empathy and its components did not differ by sex, with the exception of perspective taking, which was higher in women(AU) Conclusions: The levels of empathy between academic years were not different and empathic decline was not manifested. There were no differences between the sexes and only the component perspective taking was higher in women.

Psychometric properties of the Jefferson Empathy Scale in four nursing student faculties.

OBJECTIVE: To evaluate the psychometric properties of the Jefferson Medical Empathy Scale, Spanish version (JSE-S), its factorial structure, reliability, and the presence of invariance between genders in the behavior of empathy levels among Chilean nursing students. METHOD: Instrumental research design. The JSE-S was applied to 1,320 nursing students. A confirmatory factor analysis was used. An invariance study between genders was carried out. Descriptive statistics were estimated. Between genders, Student's T distribution was applied alongside a homoscedasticity analysis. The level of significance was α ≤ 0.05. RESULTS: The confirmatory factor analysis determined the existence of three dimensions in the matrix. The statistical results of the invariance tests were significant, and allowed comparison between genders. Differences were found between mean empathy values, as well as in some of its dimensions between genders. CONCLUSION: The factor structure of empathy data and its dimensions is in correspondence with the underlying three-dimensional model. There are differences in empathy levels and their dimensions between genders, with the exception of the compassionate care dimension, which was distributed similarly. Women were more empathetic than men.

Psychometric properties of the Jefferson Empathy Scale in four nursing student faculties / Propriedades psicométricas da Jefferson Empathy Scale em quatro faculdades de estudantes de enfermagem / Propiedades psicométricas de la Jefferson Empathy Scale en cuatro facultades de estudiantes de enfermería

ABSTRACT Objective To evaluate the psychometric properties of the Jefferson Medical Empathy Scale, Spanish version (JSE-S), its factorial structure, reliability, and the presence of invariance between genders in the behavior of empathy levels among Chilean nursing students. Method Instrumental research design. The JSE-S was applied to 1,320 nursing students. A confirmatory factor analysis was used. An invariance study between genders was carried out. Descriptive statistics were estimated. Between genders, Student's T distribution was applied alongside a homoscedasticity analysis. The level of significance was α ≤ 0.05. Results The confirmatory factor analysis determined the existence of three dimensions in the matrix. The statistical results of the invariance tests were significant, and allowed comparison between genders. Differences were found between mean empathy values, as well as in some of its dimensions between genders. Conclusion The factor structure of empathy data and its dimensions is in correspondence with the underlying three-dimensional model. There are differences in empathy levels and their dimensions between genders, with the exception of the compassionate care dimension, which was distributed similarly. Women were more empathetic than men.

RESUMO Objetivo Avaliar as propriedades psicométricas da Jefferson Medical Empathy Scale , versão em espanhol (JSE-S), sua estrutura fatorial, confiabilidade e a presença de invariância entre os sexos no comportamento dos níveis de empatia entre estudantes de enfermagem chilenos. Método Desenho de pesquisa instrumental. O JSE-S foi aplicado a 1.320 estudantes de enfermagem. Uma análise fatorial confirmatória foi usada. Foi realizado um estudo de invariância entre os gêneros. Estatísticas descritivas foram estimadas. Entre os gêneros, a distribuição T de Student foi aplicada juntamente com uma análise de homocedasticidade. O nível de significância adotado foi α ≤ 0,05. Resultados A análise fatorial confirmatória determinou a existência de três dimensões na matriz. Os resultados estatísticos dos testes de invariância foram significativos e permitiram a comparação entre os gêneros. Foram encontradas diferenças entre os valores médios de empatia, bem como em algumas de suas dimensões entre os gêneros. Conclusão A estrutura fatorial dos dados de empatia e suas dimensões está em correspondência com o modelo tridimensional subjacente. Existem diferenças nos níveis de empatia e suas dimensões entre os gêneros, com exceção da dimensão do cuidado compassivo, que se distribuiu de forma semelhante. As mulheres eram mais empáticas do que os homens.

RESUMEN Objetivo Evaluar las propiedades psicométricas de la Jefferson Medical Empathy Scale , versión en español (JSE-S), su estructura factorial, confiabilidad y la presencia de invariancia entre géneros en el comportamiento de los niveles de empatía entre estudiantes de enfermería chilenos. Método Diseño de investigación instrumental. La JSE-S se aplicó a 1.320 estudiantes de enfermería. Se utilizó un análisis factorial confirmatorio. Se realizó un estudio de invariancia entre géneros. Se estimaron estadísticas descriptivas. Entre los géneros, la distribución T de Student se aplicó junto con el análisis de homocedasticidad. El nivel de significancia fue α ≤ 0,05. Resultados El análisis factorial confirmatorio determinó la existencia de tres dimensiones en la matriz. Los resultados estadísticos de las pruebas de invariancia fueron significativos y permitieron la comparación entre géneros. Se encontraron diferencias entre los valores medios de empatía, así como en algunas de sus dimensiones entre géneros. Conclusión La estructura factorial de los datos de empatía y sus dimensiones está en correspondencia con el modelo tridimensional subyacente. Existen diferencias en los niveles de empatía y sus dimensiones entre géneros, a excepción de la dimensión de cuidado compasivo, que se distribuyó de manera similar. Las mujeres eran más empáticas que los hombres.

Cell-free biosensors for rapid detection of water contaminants.

Lack of access to safe drinking water is a global problem, and methods to reliably and easily detect contaminants could be transformative. We report the development of a cell-free in vitro transcription system that uses RNA Output Sensors Activated by Ligand Induction (ROSALIND) to detect contaminants in water. A combination of highly processive RNA polymerases, allosteric protein transcription factors and synthetic DNA transcription templates regulates the synthesis of a fluorescence-activating RNA aptamer. The presence of a target contaminant induces the transcription of the aptamer, and a fluorescent signal is produced. We apply ROSALIND to detect a range of water contaminants, including antibiotics, small molecules and metals. We also show that adding RNA circuitry can invert responses, reduce crosstalk and improve sensitivity without protein engineering. The ROSALIND system can be freeze-dried for easy storage and distribution, and we apply it in the field to test municipal water supplies, demonstrating its potential use for monitoring water quality.

Partitioning of copper at the confluences of Andean rivers.

The fate of copper (Cu) in rivers impacted by acid drainage remains poorly studied in waters with comparatively low Al and Fe concentrations. This work addresses the role of confluences in controlling the physical and chemical fate of Cu in a system with total molar ratio Cu/Al > 0.2 and Cu/Fe > 0.15. Two consecutive confluences were studied in the upper Mapocho watershed, a densely populated basin with intensive mining located in the Chilean Andes. The inflow had acidic conditions with seasonal variations and Cu up to 9 mg L-1. Lability measurements with diffusive gradient in thin films showed that Cu entered as a dissolved labile form. However, downstream from the confluences a higher pH shifted Cu toward nonlabile compounds and solid phases enriched with Cu. Measurements of x-ray absorption spectroscopy of freshly formed particles showed that composition was dominated by sorbed Cu and Cu(OH)2(s) precipitates, with a higher proportion of sorbed Cu downstream from confluences when pH < 5. Particle size distributions (PSD) measured in field showed that downstream from the confluences the total volume and average diameter of the suspended particles grew progressively, with estimated mean settling velocities increasing from 0.3 to 4.2 cm s-1. As a result, 7-30% of the influent Cu was removed from the river flow. These results highlight that shifts in chemical partition and PSDs in river confluences and the hydrodynamic environments at the river reach level control the mobility of Cu in systems with high Cu/Al and Cu/Fe.

Chlorine Reduction Kinetics and its Mass Balance in Copper Premise Plumbing Systems During Corrosion Events.

Hypochlorous acid has been reported as the main oxidant agent responsible for the corrosion of copper plumbing systems in chlorinated water supplies. However, there is little information about chlorine consumption kinetics in a combined system (i.e., with dissolved oxygen (DO) and free chlorine), as well as its complete mass balance within a copper pipe during stagnation. The results of our experiments using copper pipes filled with synthetic drinking water, with a moderate alkalinity (pH = 7.2; dissolved inorganic carbon = 80 mg as CaCO3 /L), and tested under chlorine concentrations from 0 to 8 mg/L, show that chlorine depletion is associated with pipe wall reactions (i.e., copper oxidation and scale formation processes). Free chlorine was depleted after 4 h of stagnation and its kinetic constant depend on the initial concentration, probably due to diffusion processes. Surface analysis including scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and total reflection X-ray fluorescence (T-XRF) suggest chlorine precipitation, probably as CuCl. The obtained kinetics of chlorine and DO reduction would be critical for modeling and prediction of corrosion events of copper premise plumbing systems. In addition, our results indicate that the pipe's surface reactions due to corrosion induces a loss of free chlorine in the bulk water, decreasing chlorine added for disinfection and the subsequent effect on water quality.

An integrated study of health, environmental and socioeconomic indicators in a mining-impacted community exposed to metal enrichment.

The occurrence of toxic metals and metalloids associated with mine tailings is a serious public health concern for communities living in mining areas. This work explores the relationship between metal occurrence (e.g., spatial distribution in street dusts), human health indicators (e.g., metals in urine samples, lifestyle and self-reported diseases) and socioeconomic status (SES) using Chañaral city (in northern Chile) as study site, where a copper mine tailing was disposed in the periurban area. This study model may shed light on the development of environmental and health surveillance plans on arid cities where legacy mining is a sustainability challenge. High concentrations of metals were found in street dust, with arsenic and copper concentrations of 24 ± 13 and 607 ± 911 mg/kg, respectively. The arsenic concentration in street dust correlated with distance to the mine tailing (r = - 0.32, p-value = 0.009), suggesting that arsenic is dispersed from this source toward the city. Despite these high environmental concentrations, urinary levels of metals were low, while 90% of the population had concentrations of inorganic arsenic and its metabolites in urine below 33.2 µg/L, copper was detected in few urine samples (< 6%). Our results detected statistically significant differences in environmental exposures across SES, but, surprisingly, there was no significant correlation between urinary levels of metals and SES. Despite this, future assessment and control strategies in follow-up research or surveillance programs should consider environmental and urinary concentrations and SES as indicators of environmental exposure to metals in mining communities.

Rusty river: Effects of tufa precipitation on sediment entrainment in the Estero Morales in the central Chilean Andes.

Rivers and streams continuously shape and reform their channels through the transport of sediment. One of the most important parameter used to assess this transformation is the threshold for incipient grain motion. To date, limited studies have reported that several biotic and abiotic factors can affect this parameter. However, the effects of tufa precipitation on sediment entrainment and dynamics are still unexplored. The Estero Morales is an Andean stream in Central Chile affected by the phenomenon of tufa precipitation during the winter. Along the wetted channels, tufa precipitate creates a thin solid layer that covers the sediments. A series of field surveys and flume experiments were conducted to analyze the effect of tufa precipitation on the initiation of motion and sediment dynamics. Along the wetted areas of the river, a portable dynamometer was used to explore the force needed to dislocate the grains affected by tufa precipitation from the surrounding sediments. Flume experiments were conducted to compare the incipient motion of sediment covered by tufa precipitation with unaffected sediment. Geochemical analyses were conducted to study the precipitate chemistry, mineralogy and texture. The results demonstrate that greater force is needed to move sediment particles affected by tufa precipitation compared to unaffected ones. In addition, lower sediment transport rates were measured on sediment affected by tufa precipitation, especially for the largest sediment size. These results could have important implications for studies concerning sediment dynamics and contaminant fate in the environment. Moreover, the results allow us to make some assumptions regarding the long-term role that tufa precipitation can play in rivers. Such analysis can help us to better understand and predict the changes in sediment transport rates due to tufa precipitation.

A new aerobic chemolithoautotrophic arsenic oxidizing microorganism isolated from a high Andean watershed.

Biological arsenic oxidation has been suggested as a key biogeochemical process that controls the mobilization and fate of this metalloid in aqueous environments. To the best of our knowledge, only four aerobic chemolithoautotrophic arsenite-oxidizing (CAO) bacteria have been shown to grow via direct arsenic oxidation and to have the essential genes for chemolithoautotrophic arsenite oxidation. In this study, a new CAO bacterium was isolated from a high Andean watershed evidencing natural dissolved arsenic attenuation. The bacterial isolate, designated TS-1, is closely related to the Ancylobacter genus, in the Alphaproteobacteria class. Results showed that TS-1 has genes for arsenite oxidation and carbon fixation. The dependence of bacterial growth from arsenite oxidation was demonstrated. In addition, a mathematical model was suggested and the kinetic parameters were obtained by simultaneously fitting the biomass growth, arsenite depletion curves, and arsenate production. This research increases the knowledge of chemolithoautotrophic arsenic oxidizing microorganisms and its potential role as a driver for natural arsenic attenuation.

Copper Corrosion and Biocorrosion Events in Premise Plumbing.

Corrosion of copper pipes may release high amounts of copper into the water, exceeding the maximum concentration of copper for drinking water standards. Typically, the events with the highest release of copper into drinking water are related to the presence of biofilms. This article reviews this phenomenon, focusing on copper ingestion and its health impacts, the physicochemical mechanisms and the microbial involvement on copper release, the techniques used to describe and understand this phenomenon, and the hydrodynamic effects. A conceptual model is proposed and the mathematical models are reviewed.

Enhancement of particle aggregation in the presence of organic matter during neutralization of acid drainage in a stream confluence and its effect on arsenic immobilization.

Acid drainage (AD) is an important environmental concern that impacts water quality. The formation of reactive Fe and Al oxyhydroxides during the neutralization of AD at river confluences is a natural attenuation process. Although it is known that organic matter (OM) can affect the aggregation of Fe and Al oxyhydroxides and the sorption of As onto their surfaces, the role of OM during the neutralization of AD at river confluences has not been studied. Field and experimental approaches were used to understand this role, using the Azufre River (pH 2) - Caracarani River (pH 8.6) confluence (northern Chile) as model system. Field measurements of organic carbon revealed a 10-15% loss of OM downstream the confluence, which was attributed to associations with Fe and Al oxyhydroxides that settle in the river bed. Laboratory mixtures of AD water with synthetic Caracarani waters under varying conditions of pH, concentration and type of OM revealed that OM promoted the aggregation of Fe oxyhydroxides without reducing As sorption, enhancing the removal of As at slightly acidic conditions (pH ∼4.5). At acidic conditions (pH ∼3), aggregation of OM - metal complexes at high OM concentrations could become the main removal mechanism. One type of OM promoted bimodal particle size distributions with larger mean sizes, possibly increasing the settling velocity of aggregates. This work contributes to a better understanding of the role of OM in AD affected basins, showing that the presence of OM during processes of neutralization of AD can enhance the removal of toxic elements.

Active and legacy mining in an arid urban environment: challenges and perspectives for Copiapó, Northern Chile.

Urban expansion in areas of active and legacy mining imposes a sustainability challenge, especially in arid environments where cities compete for resources with agriculture and industry. The city of Copiapó, with 150,000 inhabitants in the Atacama Desert, reflects this challenge. More than 30 abandoned tailings from legacy mining are scattered throughout its urban and peri-urban area, which include an active copper smelter. Despite the public concern generated by the mining-related pollution, no geochemical information is currently available for Copiapó, particularly for metal concentration in environmental solid phases. A geochemical screening of soils (n = 42), street dusts (n = 71) and tailings (n = 68) was conducted in November 2014 and April 2015. Organic matter, pH and elemental composition measurements were taken. Notably, copper in soils (60-2120 mg/kg) and street dusts (110-10,200 mg/kg) consistently exceeded international guidelines for residential and industrial use, while a lower proportion of samples exceeded international guidelines for arsenic, zinc and lead. Metal enrichment occurred in residential, industrial and agricultural areas near tailings and the copper smelter. This first screening of metal contamination sets the basis for future risk assessments toward defining knowledge-based policies and urban planning. Challenges include developing: (1) adequate intervention guideline values; (2) appropriate geochemical background levels for key metals; (3) urban planning that considers contaminated areas; (4) cost-effective control strategies for abandoned tailings in water-scarce areas; and (5) scenarios and technologies for tailings reprocessing. Assessing urban geochemical risks is a critical endeavor for areas where extreme events triggered by climate change are likely, as the mud flooding that impacted Copiapó in late March 2015.

Sediment composition for the assessment of water erosion and nonpoint source pollution in natural and fire-affected landscapes.

Water erosion is a leading cause of soil degradation and a major nonpoint source pollution problem. Many efforts have been undertaken to estimate the amount and size distribution of the sediment leaving the field. Multi-size class water erosion models subdivide eroded soil into different sizes and estimate the aggregate's composition based on empirical equations derived from agricultural soils. The objective of this study was to evaluate these equations on soil samples collected from natural landscapes (uncultivated) and fire-affected soils. Chemical, physical, and soil fractions and aggregate composition analyses were performed on samples collected in the Chilean Patagonia and later compared with the equations' estimates. The results showed that the empirical equations were not suitable for predicting the sediment fractions. Fine particles, including primary clay, primary silt, and small aggregates (<53 µm) were over-estimated, and large aggregates (>53 µm) and primary sand were under-estimated. The uncultivated and fire-affected soils showed a reduced fraction of fine particles in the sediment, as clay and silt were mostly in the form of large aggregates. Thus, a new set of equations was developed for these soils, where small aggregates were defined as particles with sizes between 53 µm and 250 µm and large aggregates as particles>250 µm. With r(2) values between 0.47 and 0.98, the new equations provided better estimates for primary sand and large aggregates. The aggregate's composition was also well predicted, especially the silt and clay fractions in the large aggregates from uncultivated soils (r(2)=0.63 and 0.83, respectively) and the fractions of silt in the small aggregates (r(2)=0.84) and clay in the large aggregates (r(2)=0.78) from fire-affected soils. Overall, these new equations proved to be better predictors for the sediment and aggregate's composition in uncultivated and fire-affected soils, and they reduce the error when estimating soil loss in natural landscapes.

Modeling MIC copper release from drinking water pipes.

Copper is used for household drinking water distribution systems given its physical and chemical properties that make it resistant to corrosion. However, there is evidence that, under certain conditions, it can corrode and release unsafe concentrations of copper to the water. Research on drinking water copper pipes has developed conceptual models that include several physical-chemical mechanisms. Nevertheless, there is still a necessity for the development of mathematical models of this phenomenon, which consider the interaction among physical-chemical processes at different spatial scales. We developed a conceptual and a mathematical model that reproduces the main processes in copper release from copper pipes subject to stagnation and flow cycles, and corrosion is associated with biofilm growth on the surface of the pipes. We discuss the influence of the reactive surface and the copper release curves observed. The modeling and experimental observations indicated that after 10h stagnation, the main concentration of copper is located close to the surface of the pipe. This copper is associated with the reactive surface, which acts as a reservoir of labile copper. Thus, for pipes with the presence of biofilm the complexation of copper with the biomass and the hydrodynamics are the main mechanisms for copper release.

Differential arsenic binding in the sediments of two sites in Chile's lower Loa River basin.

Fluvial sediments from two lower Loa River basin sites in northern Chile were compared in order to probe the effects of vegetation and organic matter (OM) on As accumulation in fluvial environments. The two sites were the Sloman dam, which lacks macrophytes and has a low OM content (2.4%) in sediments, and the Quillagua Oasis, which is 23 km downstream from the Sloman site and has a higher OM (6.2%) in sediments and abundant aquatic plant life. The Quillagua site had preferential As enrichment with a co-occurrence pattern that differed from that of the Sloman site, which had a lower As concentration (1528 vs. 262 mg/kg d.w., respectively). At the Quillagua site, As concentration was strongly correlated with Mn and OM (r = 0.91 and 0.85, respectively); while at the Sloman site, As concentration in sediments was significantly correlated with Ca and Sr (r = 0.63 and 0.54, respectively). Sequential extraction analyses showed that the Sloman site had higher percentage of easily exchangeable As within the surface sediment (12%, 45 mg/kg d.w.) compared with the Quillagua site (3%, 40 mg/kg d.w.). These contrasting results suggest that both vegetation and OM control the immobilization and accumulation of As in the arid Loa River basin.