Comparison of acid extraction and total digestion methods for measuring Cd isotope ratios of environmental samples.

To evaluate the pretreatment processing for Cd isotope analysis of environmental samples, acid extractions and total digestions were examined with various environmental certified reference materials. Four certified reference material samples, including fly ash, polluted soil, domestic sludge, and industrial sludge, were digested by six different acid extraction and total digestion methods, and then Cd was separated to remove other matrix by anion-exchange column. The Cd recovery rates of the acid extraction methods were 2.6-89.1%, while those of the total digestion methods were 21.6-88.7%. In these results, the Cd recovery rates were dependent on the sample type. More than 80% of the Cd in the polluted soil and domestic sludge samples could be recovered regardless of the decomposition method, except one method. On the other hand, the Cd recovery rate from fly ash was low when total digestion was performed using a HF mixture, and the recovery rate by total digestion methods for industrial sludge was higher than that by acid extraction. In our results, Cd isotope ratios tended to be more positive by increasing the Cd recovery rates, suggesting that the light isotope of Cd was decomposed preferentially during the decomposition procedures. However, when more than 80% of the Cd in the samples was recovered, the Cd isotope ratios were determined to be similar. This indicated that at least 80% of the Cd should be recovered from environmental samples to accurately measure the Cd isotopic ratio of environmental samples.

Estimation of Cadmium uptake by tobacco plants from laboratory leaching tests.

The objective of the present study was to determine the impact of cadmium (Cd) concentration in the soil on its uptake by tobacco plants, and to compare the ability of diverse extraction procedures for determining Cd bioavailability and predicting soil-to-plant transfer and Cd plant concentrations. The pseudo-total digestion procedure, modified Tessier sequential extraction and six standard single-extraction tests for estimation of metal mobility and bioavailability were used for the leaching of Cd from a native soil, as well as samples artificially contaminated over a wide range of Cd concentrations. The results of various leaching tests were compared between each other, as well as with the amounts of Cd taken up by tobacco plants in pot experiments. In the native soil sample, most of the Cd was found in fractions not readily available under natural conditions, but with increasing pollution level, Cd amounts in readily available forms increased. With increasing concentrations of Cd in the soil, the quantity of pollutant taken up in tobacco also increased, while the transfer factor (TF) decreased. Linear and non-linear empirical models were developed for predicting the uptake of Cd by tobacco plants based on the results of selected leaching tests. The non-linear equations for ISO 14870 (diethylenetriaminepentaacetic acid extraction - DTPA), ISO/TS 21268-2 (CaCl2 leaching procedure), US EPA 1311 (toxicity characteristic leaching procedure - TCLP) single step extractions, and the sum of the first two fractions of the sequential extraction, exhibited the best correlation with the experimentally determined concentrations of Cd in plants over the entire range of pollutant concentrations. This approach can improve and facilitate the assessment of human exposure to Cd by tobacco smoking, but may also have wider applicability in predicting soil-to-plant transfer.

Assessment of bioavailability and mobility of major and trace elements in agricultural soils collected in Port St Johns, Eastern Cape, South Africa using single extraction procedures and pseudo-total digestion.

PURPOSE: The aim of this study was to evaluate the applicability of ultrasound assisted single extraction and pseudo-total digestion procedures to investigate the bioavailability and mobility of major and trace elements collected from agricultural soil collected in Mzimvubu farmstead area located in Port St Johns, Eastern Cape Province (South Africa). MATERIALS AND METHODS: The potential metal availability was assessed using complexing agent (ethylenediaminetetraacetic acid (EDTA)), mild (cacium chloride (CaCl2) and ammonium nitrate (NH4NO3)), deionized water and acidic (CH3COOH) extractants with the assistance of ultrasound to evaluate mobility and bioavailability of metals. The ultrasound radiation was used to assist the single extraction of major and trace metals from agricultural soils as well shortening the extraction time. The pseudo-total metal content in agricultural soils was obtained using pseudo-total digestion employing aqua-regia. RESULTS AND DISCUSSION: The results obtained using different solvents for single extraction procedures, revealed that higher extraction of Al (256-681 mg kg-1), Fe (172-430 mg kg-1) and Mn (35-136 mg kg-1), was observed compared to other metals. Among the investigated solvents, deionized water, acetic acid and EDTA proved to be the most aggressive extractants. The geo-accumulation index (2-6) and contamination factor (3-6) demonstrated that Fe, Cr, Mn, Co, Cu, Ni, and Zn could pose significant environmental contamination risk. CONCLUSIONS: Based on the results obtained, it can be concluded that the high levels of some studied metals was due to anthropogenic activities. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40201-020-00581-x.

Assessment of major and trace element bioavailability in vineyard soil applying different single extraction procedures and pseudo-total digestion.

A different single extraction procedures (CH3COOH, Na2EDTA, CaCl2, NH4NO3, deionized water), and pseudo-total digestion (aqua regia) were applied to determine major (Al, Fe, K, Mn, Na, P, S, and Si) and trace (Cd, Co, Cr, Cu, Mo, Ni, Pb, V, and Zn) element bioavailability in a topsoil from the experimental vineyard ("Radmilovac", Belgrade, Serbia). For the first time, the extraction with deionized water during 16 h was tested as an alternative method for isolating bioavailable major and trace elements from the soil. Concentrations of the elements were determined by inductively coupled plasma - optical emission spectroscopy (ICP-OES). The extraction of Cu and S from the soil by deionized water during 16 h extracting, NH4NO3, and CaCl2 indicated that these elements could originate from the anthropogenic sources, such as fungicide. In addition according to the soil - plant experiment, performed as a preliminary experiment for future studies in vineyards, deionized water was recommended for isolation of bioavailable elements from grape seed and grape pulp; CH3COOH, Na2EDTA, CaCl2 and NH4NO3 for grape skin, while for assessment of leaf bioavailable elements from soil fraction, aqua regia was recommended. In addition, identification of similarities between the plant parts and the plant species were performed. Applying environmental risk assessment formulas, the most polluted vineyard parcel in the vineyard region "Radmilovac" was determined. The leaves of some grapevine species showed the high ability for accumulation some of the potentially toxic trace elements from the soil.

Efficiency of two digestion methods in determining the presence of metals (Cd, Cu, Cr, Pb and Zn) in geopropolis produced by Melipona scutellaris / Eficacia de dos métodos de digestión para determinar metales (Cd, Cu, Cr, Pb y Zn) en geopropóleos producidos por Melipona scutellaris / Eficiência de dois métodos de digestão para determinar metais (Cd, Cu, Cr, Pb e Zn) na geoprópolis produzida por Melipona scutellaris

Abstract This study evaluates the efficiency of acid extraction and total digestion to determine the presence of metals in geopropolis produced by the stingless bee Melipona scutellaris. Geopropolis samples were collected at five meliponaries in the city and in the metropolitan region of Salvador, Bahia State, Brazil. The sample treatment methods comprised acid extraction and total digestion. The Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES) technique was used to quantify Cd, Cu, Cr, Pb, and Zn. Geopropolis samples submitted to both digestion methods showed statistical differences. For both methods, Cr and Zn showed the highest concentrations, while those of Cd were the lowest. The Cr concentration for determination by total digestion was 37.53 mg/kg, while for acid extraction it was 32.90 mg/kg. For Zn, the concentration was 17.65 mg/kg and 8.85 mg/kg for total digestion and acid extraction, respectively. The total digestion method showed the highest concentrations of the metals evaluated; however, acid extraction (USEPA 3050b) is a more straightforward procedure for metal evaluation in geopropolis samples and presented values that support the use of geopropolis as a bioindicator. The acid extraction method USEPA 3050b, in combination with detection using ICP OES, showed efficiency in analyses carried out to determine metals in geopropolis.

Resumen El objetivo de este artículo fue evaluar la eficacia da extracción ácida y de la digestión total para determinación de metales absorbidos en geopropóleos producidos por Melipona scutellaris. Se colectaron muestras de geopropóleos en cinco meliponarios localizadas en la región metropolitana del Salvador, estado de Bahia, Brasil. Se utilizaron como métodos de tratamiento para muestras, la extracción ácida y la digestión total. Para determinar los metales Cd, Cu, Cr, Pb y Zn se utilizó Espectroscopia de Emisión Óptica con Plasma Acoplado Inductivamente (ICP OES). Se encontraron diferencias estadísticas en la concentración de metales hallados en las muestras de geopropóleos sometidas a los diferentes métodos de digestión. Para ambos métodos de digestión, las mayores concentraciones de metal fueron observadas para Cr y Zn. Entre los metales evaluados Cd presentó la menor concentración. La concentración de Cr para la determinación por digestión total fue de 37,53 mg/kg y para la extracción ácida fue de 32,90 mg/ kg. Para el Zn, la concentración fue de 17,65 mg/kg y 8,85 mg/kg para la digestión total y la extracción ácida, respectivamente. El método de digestión total mostró los mayores valores para concentraciones de los metales evaluados. Entretanto, la extracción ácida, USEPA 3050b, es un procedimiento más simple para la evaluación de metales en muestras de geopropóleos y también mostró valores que pueden satisfacer la necesidad de su uso en evaluaciones de colmenas como bio-indicador. El método de extracción ácida USEPA 3050b en combinación con la detección a través de ICP OES se mostró eficiente para el análisis de metales en geopropóleos.

Resumo O objetivo deste estudo foi avaliar a eficiência da extração ácida e da digestão total para determinação de metais adsorvidos na geoprópolis produzida por Melipona scutellaris. Foram coletadas amostras de geoprópolis em cinco meliponários, situados em Salvador, Estado da Bahia e região metropolitana. Foram utilizados como métodos de tratamento das amostras a extração ácida e a digestão total. Para determinação dos metais Cd, Cu, Cr, Pb e Zn utilizou-se a Espectrometria de Emissão Óptica com Plasma Indutivamente Acoplado (ICP OES). Houve diferença estatística na concentração de metais encontrados nas amostras de geoprópolis submetidas aos diferentes métodos de digestão. Para ambos os métodos de digestão as maiores concentrações de metais foi observada para o Cr e Zn. Dentre os metais avaliados o Cd apresentou a menor concentração. A concentração de Cr para determinação por digestão total foi de 37,53 mg/kg e para extração ácida de 32,90 mg/ kg. Para o Zn, a concentração foi de 17,65 mg/kg e 8,85 mg/kg para digestão total e extração ácida, respectivamente. O método de digestão total apresentou os maiores valores para concentrações dos metais avaliados. No entanto, a extração ácida, USEPA 3050b, é um procedimento mais simples para a avaliação dos metais em amostras de geoprópolis e também apresentou valores que podem satisfazer a necessidade de utilização na avaliação deste produto da colmeia como bioindicador. O método de extração ácida USEPA 3050b em combinação com a detecção por ICP OES mostrou eficiência para análise de metais em geoprópolis.