ABSTRACT The Lluta valley (Arica and Parinacota Region, Chile) is the site of a very unusual natural phenomenon where the soils in the valley are both saline and acidic. Soil conductivity was in the range of 1.4-16 dS/m (saturatedpaste extract) and 0.2-2.2 dS/m (1/5 soil/water extract). Soil pH was in the range of 5.1-6.9 (water), 4.9-6.3 (0.01 M CaCl 2 ), and 4.4-6.0 (1 M KCl) at a soil/solution ratio of 1/2.5. Acidic soils are rare in arid regions, and their occurrence in the Lluta valley is attributed to the unusually low pH (below 2) of the Azufre River, which may be related to volcanic activity in the area. The situation is further ex^cerbated by acidic run-off from old sulfur mine tailings.

RESUMEN El valle de Lluta (Región de Arica y Parinacota, Chile) presenta un fenómeno natural muy inusual dado que los suelos son tanto salinos como ácidos. La conductividad del suelo estuvo en el rango de 1,4-16 dS/m (extracto de pasta saturada) y 0,2-2,2 dS/m (extracto 1/5 de suelo/agua). El pH del suelo se ubicó en el rango de 5,1-6,9 (agua), 4,9-6,3 (0,01 M CaCl2) y 4,4-6,0 (1 M KCl), determinado en una relación suelo/solución de 1/2,5. Los suelos ácidos son poco comunes en regiones áridas. Su presencia en el valle de Lluta se atribuye al pH inusualmente bajo (menor de 2) del río Azufre, lo que puede estar relacionado con la actividad volcánica de la zona. La situación se ve aún más agravada por la escorrentía ácida de antiguos tranques de relave de minas de azufre.

ABSTRACT A significant portion of the current knowledge regarding the use of iron nanoparticles for remediating metal-contaminated soils is derived from laboratory experiments, leaving several unanswered questions. This article presents a field experiment comparing the efficacy of magnetite nanoparticles and microparticles for the immobilization of metals and the growth of plants in metal-contaminated soils. This study aimed to investigate the effects of magnetite particle size on metal immobilization and plant growth in soils exposed to airborne pollution from the Middle-Urals Copper Smelter in the southern taiga subzone near Revda, Russia, 50 km from Ekaterinburg. Magnetite nano- and microparticles were added to forest litter at a 4 % w/w dose. The total metal contents in litter from the study plots were 1-2 orders of magnitude higher than background metal concentrations. The magnetite nanoparticle treatment was found to decrease the concentration of exchangeable copper in soil and improve the growth of red fescue (Festuca rubra L.) on polluted soil compared to the control. In contrast, magnetite microparticles did not show any statistically significant effects. These findings are in line with laboratory results that demonstrated the superior metal adsorption properties of magnetite nanoparticles compared to microparticles. However, this study was limited in duration (2 months), and longer field studies would be necessary to confirm the role of iron particle size in the rehabilitation of metal-contaminated soils.

ABSTRACT The concept of attitude toward soil is emerging, with a slim choice of scales available to collect hard data. There is also a dearth of standard scales to acquire precise data on students’ knowledge of soil. Therefore, the objectives of the present study were: (1) to devise appropriate scales to quantify theoretical soil knowledge and attitude toward soil, and (2) to quantify the effect of laboratory studies and fieldwork on students’ theoretical soil knowledge and attitude toward soil. The study is based on data collected from undergraduate students of the introductory soil science course. Participating students were randomly divided into two groups. Teaching of the control group (n = 38) was classroom-based, while teaching of the intervention group (n = 43) was complemented with laboratory studies and fieldwork. Our test design included a pre-test and post-test. It appears that theoretical soil knowledge and students’ attitude toward soil can be improved using classroom-based education alone, without any need for laboratory or field components. However, future studies would be needed to develop questionnaires covering hands-on soil knowledge to better gauge the impact of lab work and field classes on student learning. The present study is an important step to elaborate reliable scales suitable for quantifying students’ knowledge and attitude toward the soil. It is impossible to test academic assumptions or create theoretical foundations for soil science education without a reliable device to weigh analytical concepts.

ABSTRACT In the present study, we assessed mercury exposure of residents of different sites of Valparaiso Region (Chile) due to fish consumption and atmospheric contamination from coal-burning power plant and copper smelter. Total mercury concentration was determined in 199 hair samples and in 14 species of marine fish, purchased in the supermarket or collected in the studied fishing villages. The total mercury (THg) concentrations ranged from 0.04 to 1.78 μg g-1 in human hair samples and from 0.04 to 3.87 μg g-1 in fish samples. Importantly, hair mercury concentration was significantly higher in the case of population exposed to mercury exclusively by fish consumption (e.g. Quintay and Zapallar), in comparison to the residents exposed to industrial emissions and fish consumption (e.g. Puchuncavi, Las Ventanas, Quintero). Finally, high mercury concentrations were observed in fish types commonly consumed by the residents of the fishing villages, evidencing human exposure to mercury through fish consumption.

ABSTRACT The aim of this study was to determine the toxicity of agricultural soils in areas with mining activities on worm Eisenia foetida. Total concentrations of As, Cu, Zn, Pb, and soluble As and Cu, pCu+2, granulometry, organic matter, pH and conductivity in the collected soil were determined. Toxicity was determined using bioassays of avoidance behavior and reproduction. The results show that the total concentrations of metals in soil have the following decreasing order: Cu > Zn > Pb > AS. Of the 14 soils studied, the two with highest concentrations of total copper had effect on the avoidance behavior of E. foetida. Soils with the highest percentage of organic matter and clay caused the lowest percentages of avoidance behavior. The production of cocoons was similar in most soils, except three in which it was significantly lower (p < 0.05); regarding juvenile production no significant variation (p > 0.05) was observed, except for one soil. These variables were inversely correlated to the concentration of total and soluble copper. In conclusion, most soils do not contain bioavailable chemical agents that provoke toxicity or affect the capacity of E. foetida both for habitat selection or reproduction. Avoidance behavior and reproduction were inversely related. Reproduction decreased in soils where evasion was higher. So the alternative use of bioassays of avoidance behavior, as an early warning tool, is suggested for monitoring soils that may contain potential toxic agents.

RESUMEN El objetivo de este estudio fue determinar la toxicidad de suelos agrícolas cercanos a zonas con actividad minera sobre la lombriz Eisenia foetida. Con este fin se determinaron en los suelos colectados las concentraciones totales de los metales As, Cu, Zn, Pb, y solubles de As y Cu, pCu+2, granulometría, materia orgánica, conductividad y pH. La toxicidad se determinó a través de bioensayos agudos de conducta de evasión y crónicos de reproducción. Los resultados muestran que las concentraciones totales de estos metales en los suelos tienen el siguiente orden decreciente: Cu > Zn > Pb > As. De los 14 suelos estudiados, los dos que presentaron las mayores concentraciones de cobre total afectaron el comportamiento de evasión de E. foetida. Por otra parte, los suelos con mayor porcentaje de materia orgánica y arcilla presentaron los menores porcentajes de evasión. La producción de capullos fue similar en la mayoría de los suelos, a excepción de tres, en los que fue significativamente menor (p < 0.05), en tanto que la producción de juveniles -con excepción de un suelo- no exhibió variación significativa [p > 0.05]). La producción de capullos y juveniles se relacionó inversamente con las concentraciones de cobre total y soluble. En conclusión, la mayoría de los suelos no contiene agentes químicos biodisponibles que provoquen toxicidad o afecten la capacidad de selección del hábitat ni la reproducción en E. foetida. Las variables de comportamiento de evasión y reproducción se relacionaron inversamente. Se sugiere el uso alternativo de bioensayos de comportamiento de evasión, como herramienta de alerta temprana en el monitoreo de suelos que puedan contener agentes tóxicos potenciales.

Microbiological bioassays of nitrification and nitrogen mineralization have been used for evaluation of soil quality on metal-contaminated soils. We evaluated the effectiveness of nitrification and nitrogen mineralization bioassays as quality indicators of soil degradation caused by metal contamination. We performed standard tests based on protocols of ISO 14238 (2012) and ISO 15685 (2012) on 90 soil samples collected from agricultural areas in central Chile that were historically contaminated by mining activities. Potential nitrification rate (PNR) was best explained by pH and organic matter content (OM) (R²=0.32), while nitrogen mineralization (Nmin) was best explained by OM and clay content (R²=0.44). Following normalization of the bioassays responses with respect to OM yielded significant correlations between PNR and pH and total Cu content (R²=0.22), and between Nmin and clay and total Cu contents (R²=0.19). However, inasmuch as total Cu content improved the regression model showing the inhibitory effect of Cu in both bioassays, it accounted for a mere small proportion of the variance. This was despite the wide range of Cu contents in the soils studied (51-2878 mg kg-1). Hence, due to the known sensitivity of the nitrification and nitrogen mineralization process to physicochemical characteristics of soils, these bioassays seem to have limited applicability for metal toxicity assessment in metal-contaminated soils.

The etiolation and layering technique that is used on avocados has two critical steps, namely, the rooting of clonal rootstock and graft union formation between the commercial variety and clonal rootstock. This study analyzed the rooting step of the clonal rootstock regarding its influence on graft union formation and development. The optimum times for grafting the commercial variety onto clonal avocado rootstock were determined under two greenhouse conditions, heating and no heating. The results showed that under greenhouse conditions without heating, there was higher survival (%) in plants that were grafted 60 days after the rooting steps in the clonal scion, and, in the experiments in a heated greenhouse, the highest survival rate (%) was observed in plants that were grafted 15 days after the rooting treatments. For both assays, the lowest survival rate was observed for grafts performed 30 days after the wounding and auxin application process. In histological cross sections of rootstocks at the wounding zone and in auxin treatments, a large number of emerging adventitious roots were developed at 30 days.

La técnica de etiolación y acodo utilizada en palto presenta dos etapas críticas: el enraizamiento del portainjerto clonal y el prendimiento del injerto entre la variedad comercial y el portainjerto clonal. En este estudio se evaluó la influencia de la fase de enraizamiento del portainjerto clonal sobre el prendimiento y desarrollo del injerto. Definiendo los momentos óptimos para realizar la injertación de la variedad comercial sobre el portainjerto clonal de palto, en dos condiciones de invernadero con y sin calefacción. Los resultados mostraron para las condiciones de invernadero sin calefacción, mayor prendimiento (%) en plantas injertadas a los 60 días después de los pasos de enraizamiento en la púa clonal, mientras que en el ensayo realizado en invernadero calefaccionado el mayor prendimiento (%) se observó en plantas injertadas a los 15 días después de realizados los tratamientos de enraizamiento. Para ambos ensayos, el menor prendimiento (%) se observó en plantas injertadas a los 30 días después de realizado el lesionado y la aplicación de auxinas. En cortes histológicos realizados al portainjerto, en la zona del lesionado y aplicación de la mezcla auxínica, a los 30 días, se observó gran cantidad de raíces adventicias emergiendo.

Oenothera picensis Phil. subsp. picensis can grow in soils that have been contaminated with copper from the metal smelting industry in central Chile, presenting characteristics that make it a candidate for phytoremediation processes. In order to know the real tolerance and capacity for copper extraction and to identify whether this characteristic is present solely in the exposed population, a hydroponic test was carried out using two populations of O. picensis, originated from Los Maitenes and Maitencillo, areas with high and normal Cu concentrations in the soil, respectively. The plants were exposed to copper concentration in solution between 0 and 0.16 mM, for one month. The plants presented symptoms of toxicity at 0.04 mM of Cu in the solution, without significant differences in the tolerance of both populations. The shoot copper concentrations observed in O. picensis reached the maximum of 1660±857 mg kg-1, in the treatment of 0.16 mM of Cu in the solution. However, in this treatment, the plant presented severe toxicity symptoms. Thus, it is not possible to classify it as a hyperaccumulating species.

Oenothera picensis Phil. subsp. picensis puede crecer en suelos contaminados por cobre proveniente de una fundición de metal en Chile central, y presenta características que la hacen candidata para procesos de fitorremediación. Para conocer la tolerancia real y capacidad de extracción de cobre, y si ello ocurre sólo en la población expuesta, se realizaron ensayos hidropónicos utilizando dos poblaciones de O. picensis, provenientes de los sectores Los Maitenes y Maitencillo, áreas con concentraciones altas y normales de Cu en el suelo, respectivamente. Las plantas fueron expuestas a concentraciones de cobre entre 0 y 0,16 mM en la solución, por un período de 1 mes. Las plantas mostraron síntomas de toxicidad a una concentración de 0,04 mM de Cu en la solución, sin diferencias significativas en la tolerancia de ambas poblaciones. Las concentraciones de cobre foliar observadas en O. picensis alcanzaron un máximo de 1660±857 mg kg-1, en el tratamiento de 0,16 mM de Cu en la solución. Sin embargo, en este tratamiento, la planta presentó severos síntomas de toxicidad. Por lo tanto, no es posible clasificarla como una especie hiperacumuladora.

There are many studies in the area of identifying and measuring arsenic (As) and its species in soil samples. However, stability of total As, As(V) and As(III) during sample drying and storage has received little attention. The present study evaluates the stability of total As, As(V) and As(III) in four soils with differing agricultural uses and physicochemical properties. Moisture elimination conditions were evaluated, i.e. lyophilization for 1 day vs. drying at 50°C for 3 days, along with different storage conditions, i.e. room temperature for 2 days vs. -20°C for 2 days. The results show that the recovered levels of native As(V) and As(III) are highest using lyophilization and storage at -20°C. Under these optimal conditions, total As content and the levels of As(V) and As(III) remain stable up to 10 days of storage with an error of ±20%.

The agricultural soils of the Aconcagua river basin in zones near to mining centers are characterized by having high copper concentrations. This is a risk for terrestrial organisms like plants. The studies of toxicity in plants on these kind of soils are few. We still do not know if these soils can provoke genotoxicity in plants. According to this, the aim of this investigation was to evaluate the genotoxicity and phytotoxicity of agricultural soils near to mining centers in the Aconcagua river basin (central Chile). In order to do this, Vicia faba seeds were exposed to extracts of contaminated soils by 144 h. At the end of the experiments, the germination percentage, root growth, micro-nuclei frequency and mitotic index of the seeds were determinated. The soils with the higher concentrations of total copper were 2 and 3, with 7658 y 789 mg/kg respectively. Significant inhibition in the germination porcentage in the soil 3 was observed. The higher percentage of inhibition in the mitotic index was in soils 2 and 4. A significative relationship between this parameter and the soluble copper concentration in soils was observed (R² = 0.67, p < 0.05). Soils 2 and 3, which have high copper concentrations,, are genotoxic and they would be a risk to plants growing in these kind of soils.

Los suelos agrícolas de la cuenca del río Aconcagua, en zonas cercanas a centros mineros se caracterizan por tener altas concentraciones de cobre. Esto puede ser un riesgo para los organismos expuestos. Los estudios de toxicidad en organismos vegetales que se asientan sobre estos suelos son pocos, no se sabe si pudieran provocarles efectos de genotoxicidad. De acuerdo con lo anterior, el objetivo de este trabajo fue evaluar la fitotoxicidad y la genotoxicidad de los suelos agrícolas cercanos a centros mineros en la cuenca del río Aconcagua (Chile central). Para ello, las semillas de Vicia faba fueron expuestas a extractos de cuatro suelos contaminados por 144 h. Al final de los experimentos se determinó el porcentaje de germinación, el crecimiento de la raíz, la frecuencia de micronúcleos y el índice mitótico de dichas semillas. Los suelos con las mayores concentraciones de cobre total fueron el 2 y el 3, con 7658 y 789 mg/kg, respectivamente. Los resultados muestran una inhibición significativa en la germinación de las semillas en el suelo 3. El mayor porcentaje de inhibición del índice mitótico fue en los suelos 2 y 4, se observó una relación significativa entre este parámetro y las concentraciones de cobre solubles en los suelos (R² = 0.67, p < 0.05). Los suelos 2 y 3 con concentraciones altas de cobre provocan genotoxicidad y podrían ser un riesgo para el crecimiento de diversas especies de plantas en estos suelos.

Soil erosion increases after building downward ridges along steep hillslopes, in particular during the first winter. This erosion decreases when trees grow, but runoff increases. This study presents results of erosion under five different treatments: (i) soil cover with native vegetation, (ii) bare downward ridges, (iii) downward ridges with six year-old avocado orchard, (iv) downward ridges with plant cover and (v) downward ridges covered with agroindustrial waste sludge. The results revealed 20 t ha-1 of soil erosion during the first year after ridges were built, while mitigation measures can reduce erosion in 90%. Adult orchard showed the largest runoff, which probably is due to the effect of a high and about constant soil moisture during irrigation period and smaller infiltration capacity of eroded soil.

La erosion de suelos en un huerto de paltos cultivados en camellones a favor de pendiente es alta en la condición de camellón desnudo, especialmente durante el primer invierno. Luego, la pérdida de suelo disminuye con el desarrollo de los árboles, ocurriendo lo contrario con la escorrentía. Esta práctica, masificada en Chile central durante las últimas décadas, deja el suelo descubierto y disgregado, favoreciendo la erosion y escorrentía. En el presente trabajo se cuantifica el transporte de sedimentos durante al menos tres años bajo tres cubiertas diferentes: i) antes de la preparación de suelo, con vegetación nativa, ii) camellón desnudo y iii) camellón con paltos adultos. De igual forma, se evalúan medidas de mitigación como i) camellón con cobertura herbácea y ii) camellón con lodos de agroindustria. Los resultados muestran una pérdida de más de 20 t ha-1 de suelo durante el primer invierno tras el establecimiento de camellones, en tanto que las medidas de mitigación reducen la erosión un 90%. La mayor escorrentía registrada en el huerto se debe, probablemente, al efecto del riego y la menor infiltración de un suelo ya erosionado.

The Puchuncaví valley (central Chile) has been exposed to aerial emissions from the Ventanas copper smelter. Nowadays, soils in the surroundings are sparsely-vegetated, acidic, nitrogen-deficient, and metal-contaminated. Their remediation is needed to reduce environmental risks. Phytostabilization considers the use of plants which are able to store metals in underground tissues, thus reducing their movement from contaminated soils to the air and water. The success of the treatment depends on application of suitable amendments in order to both limit metal solubility in soils and improve soil conditions for the plant development. We evaluated the effects of liming and nitrogen fertilization on cotyledon emergence, plant survival, biomass production and copper accumulation of Oenothera affinis grown in a soil from the Puchuncaví valley, under controlled conditions. Oenothera affinis is a native Chilean perennial herb, it is drought resistant, it is easy to propagate from seeds, and it produces a large biomass. The soil exhibited pH in salt extract of 4.6 and total copper concentration of 800 mg kg-1. Liming decreased Cu concentrations and Cu2+ activity in the soil solution, but did not affect cotyledon emergence. None of the plants survived in non-limed soils, while plant survival was 100% in the soils with near neutral pH. On the other hand, in limed soils, nitrogen fertilization did not affect biomass production and increased copper concentrations in both roots and shoots. It was concluded that liming is sufficient to improve soil conditions for development of O. affinis in acidic and metal-contaminated soils, allowing by this mean potential utilization of this species for phytostabilization.

El valle de Puchuncaví (Chile central) ha sido expuesto a las emisiones aéreas provenientes de la fundición de cobre Ventanas. Actualmente, los suelos en las cercanías de la fundición presentan una escasa vegetación, son ácidos, deficientes en nitrógeno y contaminados con metales. Para reducir el riesgo ambiental, es necesario remediar estos suelos. La fitoestabilización considera el uso de plantas capaces de almacenar los metales en sus estructuras subterráneas, reduciendo así su movimiento desde el suelo contaminado al aire y al agua. El éxito del tratamiento depende de la aplicación de enmiendas adecuadas que reducen la solubilidad de los metales en los suelos y, a la vez, mejoran sus condiciones para el desarrollo de la planta. Se evaluó el efecto del encalado y la fertilización nitrogenada sobre la emergencia de cotiledones, supervivencia, producción de biomasa y acumulación de cobre en Oenothera affinis cultivada en un suelo del valle de Puchuncaví bajo condiciones controladas. Oenothera affinis es una hierba perenne nativa, resistente a la sequía, fácil de propagar a partir de semillas y que produce una gran cantidad de biomasa. Los suelos presentaron un pH en sal de 4,6 y una concentración de cobre total de 800 mg kg-1. El encalado disminuyó las concentraciones de Cu y la actividad del Cu+2 en la solución del suelo, pero no afectó la emergencia de cotiledones. Las plantas no sobrevivieron en los suelos no-encalados, mientras que la supervivencia fue del 100% en los suelos con un pH cercano al neutro. Por otro lado, en los suelos encalados, la fertilización nitrogenada no afectó la producción de biomasa y aumentó las concentraciones de cobre tanto en las raíces como en los tejidos aéreos. Se concluyó que el encalado es suficiente para mejorar las condiciones del suelo para el desarrollo de O. affinis en suelos ácidos y contaminados por metales, permitiendo así la potencial utilización de esta especie para la fitoestabilización.

Copper toxicity in soil was evaluated using biomarkers of oxidative stress (catalase enzyme activity, superoxide dismutase and lipid peroxidation) in the earthworm Eisenia foetida. Agricultural topsoils from mining areas of the Aconcagua river basin were collected. Total copper concentrations were in the range of 94-959 mg kg-1, while the exchangeable copper concentrations were in the range of 46-2225 µg kg-1. Earthworms exposed to soil with exchangeable copper concentrations above 32 µg kg-1 showed an increase in catalase activity. Parameters of antioxidant activity were more sensitive than the weight change and thus can be used as appropriate biomarkers in Eisenia foetida.