Study of ultrasound-assisted sequential extraction procedure for potentially toxic element content of soils and sediments

doi:10.1016/j.microc.2016.10.006

Microchemical Journal

Volume 136, January 2018, Pages 80-84

https://doi.org/10.1016/j.microc.2016.10.006 Get rights and content

Highlights

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Shortening possibility of 16h shaking process of BCR sequential extraction procedure was studied by ultrasonic pretreatment.
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By 1 hour u.s. pretreatment and 1 hour shaking 77% of certified element concentrations can be extracted.
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On the basis of this results appropriate correction factors can be proposed to the shortened procedure.

Abstract

For risk assessment of potentially toxic element (PTE) pollution of sediments and soils the fractionation by sequential extraction procedures are applied which require longtime leaching-shaking periods to achieve the dissolution equilibria. In this work an attempt is described for reduction the duration these leaching-shaking periods of the sequential extraction procedure proposed by Community Bureau of Reference (BCR) in 1993 by application of ultrasonic treatment. The fractionation of PTE content of BCR 701 certified reference sample was performed in three experiments: “A” experiment was the control, all extraction steps were performed with 16 hours shaking according to the BCR prescription; “B” experiment: in each extraction step was applied 1 hour preliminary ultrasonic treatment and after this 1 hour shaking; “C” experiment: only 1 hour ultrasonic treatment and no shaking was applied. It was experienced that by ultrasonic treatment can be efficiently increased the rate of dissolution when constant temperature of assisting medium was kept. 77% and 63% of element content extractable with the control “A” experiment can be extracted in “B” and “C” experiments, respectively. To achieve the 100% efficiency further experiments are in process.

Section snippets

Introduction, aim of the study

The growing industrialization and urbanization in the 20th century prompted biologists and environmental researchers to call for the mapping of biogeochemical cycles of various elements which is essential to ensure conditions for a healthy life in harmony with our environment. This revelation significantly affected the requirements to be met by the methods and instruments in the field of analytical chemistry [1]. Improvements in the speed and cost of the supplying of data as well as the

Sample

Commercially available BCR-701 sediment certified reference material (CRM) was used which is recommended for the validation of the BCR procedure. It is certified for extractable concentrations of six elements (Cd, Cr, Cu, Ni, Pb, Zn) by the 1st, 2nd and 3rd BCR extraction steps [15].

BCR sequential extraction procedure

The three-plus-one-step BCR sequential extraction procedure is presented in Table 1. For estimation of total soluble PTE content the microwave-assisted digestion with HNO₃/H₂O₂ mixture as described in STEP 4 was

Results and discussion

The results of the “A”, “B” and “C” experiments are summarized in Table 2. In this table the measured concentrations in BCR 1, 2 and 3 steps were compared with the Student-test with each other and the symbols > and < mean the significant difference, while the symbols ≥ and ≤ mean the nonsignificant differences at p = 5% level. The results of test “A” were compared with the certified concentration values of BCR-701 CRM sample by the student test too and only Cr concentration obtained in step 1

Conclusion

In present work the shortening possibility of BCR sequential extraction procedure was studied how the very time-consuming shaking process can be shortened or left out using ultrasonic pretreatment. The same certified reference material was used in three experiments. In the test “A” the procedure was performed according to the original protocol, whereas in the test “B” the 16-hour shaking was replaced by one hour shaking prescriptions after one hour ultrasonic pretreatment for each step, the

Acknowledgement

This work was supported by the Hungarian Scientific Research Fund (OTKA 108558) and Research Centre of Excellence - 11476-3/2016/FEKUT.

Supported through the New National Excellence Program of the Ministry of Human Capacities.

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Metal ions in BCR extraction method are classified into four fractions: water/acid soluble and exchangeable fraction, reducible fraction, oxidizable fraction, and residual fraction (Zhu et al., 2018). However, the conventional sequential extraction (CSE) procedure is time-consuming and labor-intensive, which require longtime leaching-shaking time to achieve the dissolution equilibria (Kovacs et al., 2018). The application of ultrasound and microwave technology can accelerate the extraction process.
Coal-fired power plant is one of the main anthropogenic sources of lead emission and most of lead in coal can be transferred to its combustion products (fly ash, desulfurization gypsum and slag) after burning. The fraction distribution of lead in coal, fly ash (FA), desulfurization gypsum and slag can reveal their environmental stability and migration ability. However, the conventional sequential extraction method (CSE) for screening lead fractions is time-consuming and labor-intensive. In this paper, two high efficiency methods including ultrasonic-assisted sequential extraction (UASE) method and microwave-assisted sequential extraction (MASE) method were developed. The working parameters were optimized by comparing the concentration obtained from the UASE and MASE with the optimized BCR method. The whole extraction time shorten from 48 h to 20 min. The recoveries of the first three fractions were on average of 85% for the UASE method and 95% for the MASE method in coal, fly ash, desulfurization gypsum and slag. The accuracies of the developed methods were verified by the analysis of the coal CRM (GBW11156) and FA CRM (GBW08401). The high reproducibility and applicability of the methods were demonstrated by analyzing lead in coal, fly ash, desulfurization gypsum and slag samples from 12 different power plants in China. The developed UASE and MASE were more efficient methods for accelerated screening of lead fractions in coal and its combustion products.
Optimization and validation test of a sonoreactor-assisted methodology for fast and miniaturized extraction of trace elements from soils
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Several authors have described the use of ultrasonic baths for the quantitative extraction of trace elements within 15–30 min from environmental and biological samples [13], estuarine sediment samples [14], inorganic fertilizers in heated baths [15] or fractionation of trace elements in agricultural soils [16]. Recently, Kovács et al. [17] have described the use of the ultrasonic bath to speed the sequential extraction of trace elements in soils and sediments. The probe is the most potent ultrasonic sample pretreatment system (100 times more potent than the bath on average).
We have proven the overall applicability of the novel sonoreactor VialTweeter as a tool for a fast, miniaturized and economical extraction of trace elements, namely Cu, Zn, As, Cd, Pb, from soil samples, followed by ICP-MS. The proposed analytical approach applicable in the context of environmental monitoring of elemental soil pollutants, since the selected analytes are relevant pollutants whose presence in soils produces significant effects on their quality affecting animals, plants and humans. The optimum conditions for the extraction of trace metals assisted by the sonoreactor, selected by a Box-Behnken (BBD) experiment design along combined with a response surface methodology were 93% sonication amplitude, 450 s sonication time, 80% HNO₃ and a solvent/sample ratio of 0.18 mL/mg. The proposed sonoreactor-assisted extraction methodology provides several advantages of respect to the standard acid digestion taken as comparison term for validation, including a shorter pretreatment time and use of less sample and reagents amounts. However, mixed validation results against the standard acid digestion (taken as a model providing accurate results) were obtained depending on the analyte, with the best results in the case of cadmium that could be measured after US extraction without systematic error respect to the standard acid digestion. Copper and lead can be determined by the proposed US extraction plus ICP-MS only after applying a correction factor based on the slope of the correlation with the standard acid digestion. US treatment for As determination can be only useable by applying a constant correction factor based on the intercept of the correlation line, whereas Zn determination requires a correction based both in the slope and intercept of the correlation line.
Evaluation of mobility, fractionation, and potential environmental risk of trace metals present in soils from Struibult gold mine dumps
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The SEP is therefore applied to understand the different chemical forms of metals present in the soil fractions. A widely used procedure, Community Bureau of Reference (BCR) which originated in 1979 has been applied and recently been modified due to its limitations (Quevauviller et al., 1997; Heltai et al., 2000, 2018, 2005; Tokalioglu et al., 2003a, 2003b; Arian et al., 2008; Anju and Banerjee, 2010; Wang et al., 2010; Alonso et al., 2011; Mittermuller et al., 2016; Fernandez et al., 2017; Kovacs et al., 2018). The main disadvantages of this method are that it is tedious and requires longer extraction times (more than 16 h per step).
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Recent Progress on Ex Situ Remediation Technology and Resource Utilization for Heavy Metal Contaminated Sediment
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Chemical Speciation, Bioavailability and Human Health Risk Assessment of Metals in Surface Dust from an Industrial Cluster in India
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Study of ultrasound-assisted sequential extraction procedure for potentially toxic element content of soils and sediments

Highlights

Abstract

Section snippets

Introduction, aim of the study

Sample

BCR sequential extraction procedure

Results and discussion

Conclusion

Acknowledgement

Sci. Total Environ.

Guidelines for terms related to chemical speciation and fractionation of elements. Definitions, structural aspects, and methodological approaches

Pure Appl. Chem.

Soil analysis and nutrition capacity

Microchem. J.

Trace metal speciation in sediment and soils

Element Speciation in Bioorganic Chemistry

Speciation of trace metals in sediments and combustion waste

Sequential extraction procedure for the speciation of particulate trace metals

Anal. Chem.

Determination of the soluble nutrient element content of the soil