Sylvia Copaja - Academia.edu (original) (raw)

Papers by Sylvia Copaja

Journal of the Chilean Chemical Society, Jun 1, 2023

Trace elements in aquatic ecosystems are considered as major pollutants due to their environmenta... more Trace elements in aquatic ecosystems are considered as major pollutants due to their environmental persistence, toxicity and ability to be incorporated into food webs. Contaminated sediments represent a threat to benthic macroinvertebrates which in turn expose high trophic organisms to hazardous trace elements, therefore metals accumulated in benthic organisms can also be bio concentrated in food webs. Direct toxic effects of metals include changes in diversity and abundance of benthic invertebrates while, indirect effects include modifications of species interactions and reductions in food quality. In this work, we study the potentially toxic metal concentrations in both sediments and benthic macroinvertebrates in the Maipo River basin (central Chile) evaluating the risk assessment of sediment, toxicity to the biota and bioaccumulation in the organisms. Sediments and benthic organisms were sampled in spring (October-December) 2016 from four sites of the Maipo River basin. Twelve trace elements (As, Al, Cd, Cu, Cr, Hg, Fe, Mn, Mo, Ni, Pb and Zn) were determined by AAE. The Geo accumulation index showed that Zn was moderate to strong pollute in all sites and the enrichment factor showed that there were no important anthropic impacts in the river. High level of contamination was found for Cu in PEL and the pollution index showed that PEL was extremely polluted. Three (Cu, Mn and Zn) out of the five metals analyzed were the elements which presented the largest toxicity to organisms in these aquatic systems based on the Threshold Effect Concentration (TEC) and Probable Effect Concentration (PEC) analysis. Most of the metals analyzed did not show bioaccumulation; however, Ni and Pb were the metals with the highest bioaccumulation factor in all the studied sites.

Journal of The Chilean Chemical Society, Nov 1, 2022

In Chile, metal mining is concentrated between the Administrative Regions IV and VI (which includ... more In Chile, metal mining is concentrated between the Administrative Regions IV and VI (which includes the Metropolitan Region). The northern and central zones of the country have abundant copper as well as mineral iodine and iron. Today, these residues are stored in tailing dams. Mine tailings constitute the toxic residues composed of trace elements, which in many occasions are deposited in areas neighboring human settlements and are a health hazard for the inhabitants In this work, the concentrations of trace elements such as: Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Zn were studied in 6 sites of the tailings located within Andacollo city, Northern Chile. The sampling points were recorded using GPS geographic coordinates and, in the laboratory, they were characterized determining: pH, electrical conductivity, soluble organic carbon, total organic carbon, available phosphorus, boron, total nitrogen and capacity cation exchange. The concentrations of trace elements in tailings samples, were quantified by atomic absorption spectrophotometry (AAS). Potential anthropogenic hotspots were assessed using indices including enrichment factor (EF), geoaccumulation index (Igeo), contamination factor (CF), Pollution load index, (PLI), ecological risk (Ei) and potential ecological risk (PERI) index. These indexes are used to assess the presence and intensity of anthropogenic contaminant deposition on surface soil. The physicochemical characterization of the tailings allowed establishing a profile of the environmental conditions of the sampled sites. The sites that presented a higher concentration of metals correspond to sites 4 and 6. The polluted index values than indicated, high degree of contamination for Cu, Hg and Mo by other hand PLI and Ri index indicated the sites more polluted are 4,5 and 6.

Annals of Applied Biology, Jun 1, 1993

SummaryThe effects of DIMBOA in cultivars of wheat on aphid antibiosis and tolerance to the insec... more SummaryThe effects of DIMBOA in cultivars of wheat on aphid antibiosis and tolerance to the insecticide deltamethrin were investigated for the aphid Sitobion auenae. Over 48 hours the mean relative growth rate differed significantly between nymphs of S. auenae reared on wheat cultivars containing different levels of DIMBOA. Nymphs on the resistant cv. Altar showed a significantly greater susceptibility to deltamethrin, with nearly a three‐fold increase in the relative toxicity of deltamethrin, compared with the susceptible cv. Dollarbird. The LC50, adjusted for weight, was reduced by 91% for nymphs reared on the high DIMBOA cultivar. The potential for the enhancement of predation under a reduced pesticide régime is discussed in relation to this research.

Journal of The Chilean Chemical Society, Sep 1, 2022

Herbicides are one of the most widely used agrochemical classes around the world. They help farme... more Herbicides are one of the most widely used agrochemical classes around the world. They help farmers to protect their crops against weeds. However, they can move through the soil profile polluting water resources and adversely affect human health. Groundwater is an important source for the production of drinking water in many places of the world and the presence of pesticide residues in groundwater is a serious threat to the health of consumers of drinking water. In this work, the behavior of two herbicides Atrazine and Trifluralin were study in an agricultural soil: Alhue soil and this soil modified whit clay (Kaolinite) and organic matter (Humus). The original soil and modified soil samples were characterized by their physicochemical properties: pH, EC, OC and texture. The analytical method was optimized for the quantification of Atrazine and Trifluralin by High Performance Liquid Chromatography (HPLC). The contact time, adsorption/desorption isotherms, persistence of both compounds in the soil samples and modified soil samples with clay and/or organic matter was studied. In general, all sorption curves for Trizine and Trifuralin in the modified soil samples were similar with relatively low adsorption for Trifuralin indicating that the soil modifications were not significant. The kinetic of sorption process was described by Elovich model. Both herbicides present a low Koc value, however, they present different types of adsorption, being for Atrazine a moderate adsorption and for Trifluralin a weak adsorption, which implies that both herbicides could be distributed in bodies of water as they are not fixed by organic matter. However, it should be noted that Atrazine presents higher Koc values than Trifluralin in all soil samples, which could mean that Atrazine would be less bioavailable than Trifluralin. Values obtained in the Pearson correlation of CO (%) and % of clay are expected since, when observing the results obtained in the Kd parameters for soils modified by both herbicides, they show that the higher the % of the physicochemical parameter, the higher the adsorption of the compound by the soil. The persistence of the pesticides showed that with both the addition of Kaolinite and Humus to the soil increases the half-life time for both herbicides. The results of the GUS index showed that both Atrazine and Trifluralin would be classified as leachable compounds in all soil samples.

Chemischer Informationsdienst, May 17, 1983

ChemInform Abstract Die Reaktionen der Sulfane (I) mit [Cu(H2O)6](ClO4), in Acetonitril und mit C... more ChemInform Abstract Die Reaktionen der Sulfane (I) mit [Cu(H2O)6](ClO4), in Acetonitril und mit CuCl2 rc 2 H2O in Ethanol liefern die Cu(I)-Verbindungen (II) bzw. (IV) und S02. Bei Reaktion von [Cu(H2O)6]-(ClO4), in Ethanol erhält man Cu(I)-sulfid ; ferner werden Sulfationen nachgewiesen. Reaktionsprodukt von (Ib) mit CuCl2 in wasserfreiem Ethanol ist die Verbindung (VI). Die Reaktionsweise der Sulfane (I) bei den beschriebenen Umsetzungen hängt von den Hydrolyse-bzw. Alkoholyseprodukten ab. Bei der Bildung dieser Zwischen-bzw. Endprodukte scheinen sich die S-und N-Atome in (I) gegenüber Wasser, Alkohol und Cu(II)-ionen als elektrophile bzw. nucleophile Zentren zu verhalten.

Journal of The Chilean Chemical Society, Sep 1, 2019

Lithium is an essential element for humans and animals, it is bio accumulated by plants and it is... more Lithium is an essential element for humans and animals, it is bio accumulated by plants and it is a relatively uncommon element in the Earth ś crust, on the contrary boron is widely distributed and it is micronutrient for plants. Boron and lithium are incorporated in fertilizers for agriculture and they used in many industries. Economically lithium is considered a strategic element because it is important in energy markets. There are two main economically recoverable sources of lithium, those being mineral ores and the evaporate deposits (playa lakes, called "salars" in Spanish). Direct extraction of lithium from brines at the salars is a low cost method and generates byproducts such as boron. Salars with high concentrations of Li have been reported in the Andean region near the borders of Chile, Bolivia, and Argentina. In Chile, the brines at Salar de Atacama are considered an important commercial source of lithium. To the northeast of Salar de Atacama it is located Salar de Ascotán (21º27`01, 9``S; 68º15`8,5``W) where the commercial boron extraction has been done for many decades but lacks published information about lithium extraction. In this study concentrations and distribution of lithium and boron in the water, sediment and salt crust were analyzed in some of the east-side springs which have a high endemic biodiversity. The concentrations in the salt crust were higher than in water and sediment. Geographically, the concentration of lithium in salt crust increases from north to south, but the boron concentration was higher in the extreme north and south, in the southernmost spring, Nº11. The average concentration of B in the salt crust was 149 [mg/Kg] and for Li was 3000 [mg/Kg] at the east side of the salar, thus it is the area with the highest concentration of lithium and boron. The concentrations in the salt crust were high and geographically heterogeneous for using a non-invasive method, for environmental protection we propose an exploration superficial on the western side which lack spring water and present the higher concentration of lithium and boron of the salar.

Journal of The Chilean Chemical Society, Mar 1, 2018

Northern Chile is characterized by water scarcity. The Lluta River, located in the XV region of A... more Northern Chile is characterized by water scarcity. The Lluta River, located in the XV region of Arica and Parinacota, is the one of the main rivers in northern Chile. The elevated levels of metals and metaloids in the river reduce the agricultural productivity and variety of species can be cultivated within the valley, which are of great importance for the consumption of the inhabitants of the area. Heavy metals in river bottoms may cause various effects on the water quality, as such the capacity to accumulate metals; levels of toxicity and metal stabilization in sediments have often been considered a pollution index of a territory. In this work the concentrations of Al, Cu, Fe, Mn, Mo, Pb and Zn from the pseudo-total and labile fraction of Lluta river sediments were studied. Samples from 10 sites along the river were collected. The sediments were characterized determining: pH, electrical conductivity, organic carbon (OC), organic total carbon (OTC), available phosphorus and boron. Heavy metals were analyzed by Atomic Absorption Spectroscopy (AAS). For the metals analyzed in the pseudo-total fraction, the highest concentrations found were: Al in the site 10, (17061 mg kg-1) and Fe on site 6, (29898 mg kg-1). For the labile fraction, highest concentrations of metals were: Al in site 6 (1079 mg kg-1), Fe in site 9, (275 mg kg-1) and Mn in site 9 (1578 mg kg-1). Using the Risk assessment code (RAC), the site 6 presents the greatest risk with high values of Cu, Mn, Pb and Zn, followed by site 1 with high values of Mn, Cu and Zn, and site 9 with high values of Mn, Cu and Pb. On the other hand, the MacDonald PEC (probable effect concentration) and TEC (threshold effect concentration) toxicity criteria, showed that the sites 4 and 6 have levels above the TEC for Cu, Fe, Pb and Zn, and levels above the PEC at six sites for Mn.

Journal of The Chilean Chemical Society, 2023

Allelopathy is one of the alternatives used for integrated weed management (IWM), in order to min... more Allelopathy is one of the alternatives used for integrated weed management (IWM), in order to minimize the use of synthetic herbicides. Allelopathy is defined as the effect produced by a chemical released by a donor plant on the development of another competitive recipient plant. Research on allelopathic interactions has been focused on agricultural crops, and allelopathic activity of indole alkaloids has been reported in cereals such as barley (Hordeum vulgare L.), whose principal natural secondary metabolite is Gramine. The degradation products of this metabolite in agricultural soils have not been investigated, however indole and derivatives substituted in aromatic ring and heterocyclic can be produced, so the role of soil in the allelopathic behavior of these compounds is not yet clear. In this work, phytotoxicity and dynamics of Gramine, indole and model series of substituted indoles in position 2 and 3 of the aromatic ring and position 5 of the aromatic ring were investigated in order to understanding the role of this metabolite in the allelopathy property of cereal barley. The phytotoxic activity against competitive cereals and weeds was determined in soil, from which the percent inhibition (% I) of seed germination and seedling growth was measured. In adsorptions study, according to the values obtained from the adsorption coefficient (Kd), it was obtained that all the series of indole alkaloids shows a moderate adsorption in Alhue soil, with the exception of indole 3-acetic acid. In the study of desorption, this compound showed a desorption percentage of 81%, according to the Kd values obtained. The persistence studies indicated a half-life (t1/2) with a range of values between 7 h and 18 days for the series of indole alkaloids studied, where the highest value of t1/2 was for indole 2-carboxylic acid and the minor one for indole 5-carbaldehyde. The dynamics of the compounds in Alhue soil affect phytotoxic activity, as well as bioavailability, so that soil plays an essential role in the phytotoxic effect of the compounds. Indole and Indole 2-carboxylic acid had the greatest phytotoxic effect, this behavior can be attributed to its greater persistence and low adsorption, that is, they are more bioavailable in Alhue soil and so the role as an allelochemical would be favorable.

Chemischer Informationsdienst, 1985

Revista Latinoamericana De Quimica, 2003

A test with the microalga Chlorella vulgaris was used to evaluate the allelopathic potential acti... more A test with the microalga Chlorella vulgaris was used to evaluate the allelopathic potential activity of indole alkaloids present in cereals. Gramine, the main indole alkaloid present in barley shows the highest toxicity. A model mechanism of action for auxin was used to analyze the structural effect on the observed toxicity.

Herbicides - Advances in Research, 2013

Phytochemistry, 1989

Seedlings of four wheat cultivars were infested with Metopolophium dirhodum nymphs. After aphids ... more Seedlings of four wheat cultivars were infested with Metopolophium dirhodum nymphs. After aphids had fed for 40 hr on the plants, the levels of the defense metabolite 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one had changed. The changes depended on the cultivar and the portion of the leaf examined. The increase was greater in cultivars Naofen (45.0% at the tip of the leaf, 96.2% at the base where aphids were feeding) and Quilafen (14.7 and 35.8% respectively). The increase was not significant in cultivars Huenufen and Sonka. A simple and sensitive high performance liquid chromatographic method is described for the quantitation of the above benzoxazinone and its demethoxylated analogue using small amounts of plant tissue.

Phosphorus and Sulfur and the Related Elements, 1985

ABSTRACT A series of alkoxythioamines, R2NSOR' (NR2=morpholino. piperidino and diethylami... more ABSTRACT A series of alkoxythioamines, R2NSOR' (NR2=morpholino. piperidino and diethylamino: R′ = Me, Et, i-Pr), has been prepared by the alcoholysis of N, N′-thiobisamines induced by the presence of CuCl2 and HCl. The products were characterized by their IR. H-NMR spectra and elemental analyses.

Zeitschrift für Naturforschung C, 2004

Secondary metabolites, DIBOA, HBOA, 7-OH-HBOA and BOA, were isolated and quantified from S. dulce... more Secondary metabolites, DIBOA, HBOA, 7-OH-HBOA and BOA, were isolated and quantified from S. dulce (Nees), a native species in Chile belonging to the Acanthaceae family. The highest DIBOA and HBOA contents were determined in leaves (9.25 mmol kg-1 fr. wt) and root (6.81 mmol kg-1 fr. wt), respectively. Aglycones, 7-OH-HBOA and HBOA, were isolated together from root extracts of Acanthaceae species. Both, HBOA and 7-OH-HBOA should be direct precursors in the biosynthesis of DIBOA and DIMBOA, respectively.

Wood Science and Technology, 2003

Systematic HPLC analysis of aqueous extracts from bark and woody parts of Quillaja saponaria Mol.... more Systematic HPLC analysis of aqueous extracts from bark and woody parts of Quillaja saponaria Mol. ('quillay') growing at three different localities in Central Chile, showed that saponin contents in 100 g of dried plant material ranged from 2.3 g to 15.8 g depending on the extraction method (soxhlet or maceration), the part of the plant analysed and the site of collection. Twigs and barks afforded in most cases extracts with higher levels of saponins as compared to those obtained with woody parts of the same specimen.

Phytochemistry, 1999

Hydroxamic acids, quanti®ed by HPLC, varied in concentration between three cultivars of wheat. Se... more Hydroxamic acids, quanti®ed by HPLC, varied in concentration between three cultivars of wheat. Seeds, roots, leaves and the entire plants were analysed separately. No hydroxamic acids were present in seeds throughout the 7 days of germination studied. Leaves accumulated relatively high concentrations of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) and lower concentrations of its demethoxylated analogue (DIBOA). Higher concentrations of DIBOA were recorded in roots than in leaves of two of the cultivars. Maximal concentrations of DIBOA in the entire plant occurred prior to those of DIMBOA. Although the concentrations of the two hydroxamic acids decreased in all parts of the plant at the latter stages of germination, the absolute quantity of these compounds remained stable, indicating a growth dilution eect. The results show that formation of hydroxamic acids is initiated in the early stages of germination and support the idea that DIBOA is a precursor of DIMBOA. In view of the relatively high concentrations of hydroxamic acids in roots, the possibility of allelopathic control of weeds and root-feeding pests is discussed.

Phosphorus, Sulfur, and Silicon and the Related Elements, 1991