Abstract
Background, aim, and scope
Diffusive gradients in thin films (DGT) have been recognized as a suitable tool to assess in situ metal bioavailability in soils. Mine tailings have some singular characteristics such as high heavy-metal concentrations, low pH, or absence of water retention capacity that may compromise the correct application of this technique whose applicability is known to be pH dependent. The goal of this study was to determine the response of DGT devices in heavy-metal-polluted mine tailings with different pH. In addition some experiments were performed in order to determine the effect of acidic pH and dissolved ions on the binding properties of the chelating resin.
Materials and methods
We tested DGT devices on three different mine tailings: acid pH 3, acid tailing limed to pH 5.5, and neutral pH 7.2. The tailings showed high metal concentrations, e.g., 7,000 mg kg−1 Pb, 9,000 mg kg−1 Zn, and 380 mg kg−1 Cu. Diffusive and Chelex resin gels were prepared according to previously published methods. Two chelating resins and diffusive gels thicknesses (0.4 and 0.7 mm) were tested. Four DGT devices of each type were placed during 24 h in pots (one device per pot) containing 1 kg mine tailings in a climate chamber with humidity (50–90%) and controlled temperature conditions (night 16°C and day 23°C). Pots were irrigated with deionized water to field capacity, and then two different experiments were performed: (a) allowing free drainage and (b) maintaining the water saturation. In addition, we tested DGT devices in solutions at pH 3 with similar properties to the soil solution measured in the acid tailing. Eluted Zn, Cd, Pb, and Cu from the chelating resins were measured using inductively coupled plasma–optical emission spectrometer (ICP–OES; Vista-MPX Varian).
Results and discussion
The metal concentrations taken up by the DGT devices were affected by the different pH values of the tailings. The highest metal concentrations measured with DGT (C DGT) were obtained in the pH 3 treatments (both saturated and free drainage). Significant differences for C DGT were observed between water-saturated and free drainage treatments in the acid pH 3 tailing. When limed pH 5.5 tailing and neutral pH 7 tailing were considered, these differences were lower and not significant. In pH 3 tailings low values for C DGT/C soil solution were obtained (<0.06), indicating that these soils have a low capacity to resupply depleted metals to the solution. The limed acid tailing and the neutral tailing showed values between 0.05 and 0.94 indicating a much more rapid resupply from the solid phase. Deployment under water-saturated conditions yielded much higher C DGT values than under free drainage, indicating the importance to adequately control the moisture content in these soils with poor water retention capacity. In solutions with pH 3 mimicking the soil solution composition of the tailings, a loss of the binding capacity of the resin of 50–60% and 60–80% for Zn in 0.7-mm DGT and 0.4-mm DGT devices, respectively, was observed. As a consequence, 0.7-mm DGT devices had better reliability to carry out in situ determinations in solutions with high metal concentrations and low pH.
Conclusions
The use of DGT in mining soils can be a promising tool to study bioavailable metals concentrations in mine tailings but it has to be used carefully under acidic pH. Competition with other cations that are present at very high concentrations may hinder the accumulation of metals by the chelating resins, which should be tested under the conditions of the particular mine tailing.
Similar content being viewed by others
References
Conesa HM, Faz Á, Arnaldos R (2006) Heavy metal accumulation and tolerance in plants from mine tailings of the semiarid Cartagena–La Unión mining district (SE Spain). Sci Total Environ 366:1–11. doi:10.1016/j.scitotenv.2005.12.008
Conesa HM, Robinson BH, Schulin R, Nowack B (2007a) Growth of Lygeum spartum in acid mine tailings: response of plants developed from seedlings, rhizomes and at field conditions. Environ Pollut 145:700–707. doi:10.1016/j.envpol.2006.06.002
Conesa HM, Robinson BH, Schulin R, Nowack B (2007b) A laboratory study on revegetation and metal uptake in native plant species from neutral tailings. Water Air Soil Poll 183:201–212. doi:10.1007/s11270-007-9369-1
Conesa HM, Robinson BH, Schulin R, Nowack B (2008) Metal extractability in acidic and neutral mine tailings from the Cartagena-La Unión Mining District (SE Spain). Appl Geochem 23:1232–1240. doi:10.1016/j.apgeochem.2007.11.013
Davison W, Zhang H (1994) In situ speciation measurements of trace components in natural waters using thin-film gels. Nature 367:546–548
Degryse F, Smolders E, Oliver I, Zhang H (2003) Relating soil solution Zn concentration to diffusive gradients in thin films measurements in contaminated soils. Environ Sci Technol 37:3958–3965. doi:10.1021/es034075p
Garmo ØA, Røyset O, Steinnes E, Flaten TP (2003) Performance study of diffusive gradients in thin films for 55 elements. Anal Chem 75:3573–3580. doi:10.1021/ac026374n
Gimpel J, Zhang H, Hutchinson W, Davison W (2001) Effect of solution composition, flow and deployment time on the measurement of trace metals by the diffusive gradient in thin films technique. Anal Chim Acta 448:90–103
INAP (International Network for Acid Prevention) (2002) Diffusive gradients in thin films (DGT). A technique for determining bioavailable metal concentrations. http://www.inap.com.au/public_downloads/Research_Projects/Diffusive_Gradients_in_Thin-films.pdf. Accessed 14 May 5 2009
McGrath SP, Knight B, Killham K, Preston S, Paton GI (1999) Assessment of the toxicity of metals in soils amended with sewage sludge using a chemical speciation technique and a lux-based biosensor. Environ Toxicol Chem 18:659–663
Moradi AB, Conesa HM, Robinson BH, Lehmann E, Kaestner A, Schulin R (2009) Root responses to soil Ni heterogeneity in a hyperaccumulator and a non-accumulator species. Environ Pollut 157:2189–2196. doi:10.1016/j.envpol.2009.04.015
Nowack B, Koehler S, Schulin R (2004) Use of diffusive gradients in thin films (DGT) in undisturbed field soils. Environ Sci Technol 38:1133–1138. doi:10.1021/es034867j
Planquart P, Bonin G, Prone A, Massiani C (1999) Distribution, movement and plant availability of trace metals in soils amended with sewage sludge composts: application to low metal loadings. Sci Total Environ 241:161–179
Sondergaard J (2007) In situ measurements of labile Al and Mn in acid mine drainage using diffusive gradient in thin films. Anal Chem 79:6419–6423. doi:10.1021/ac0708442
Systat (2002) Version 10.2 Systat Software Inc. Richmond, California, USA
Wang Z, Schan XQ, Zhang S (2002) Comparison between fractionation and bioavailability of trace elements in rhizosphere and bulk soils. Chemosphere 46:1163–1171
Zhang H, Davison W, Miller S, Tych W (1995) In situ high resolution measurements of fluxes of Ni, Cu, Fe, and Mn and concentrations of Zn and Cd in porewaters by DGT. Geochim Cosmochim Acta 59:4181–4192
Zhang H, Davison W (1995) Performance characteristics of diffusion gradients in thin films for the in situ measurement of trace metals in aqueous solution. Anal Chem 67:3391–3400
Zhang H, Davison W, Knight B, McGrath S (1998) In situ measurements of solution concentrations and fluxes of trace metals in soils using DGT. Environ Sci Technol 32:704–710
Zhang H, Davison W (1999) Diffusional characteristics of hydrogels used in DGT and DET techniques. Anal Chim Acta 398:329–340
Zhang H, Davison W (2001) In situ speciation measurements. Using diffusive gradients in thin films (DGT) to determine inorganically and organically complexed metals. Pure Appl Chem 73:9–15
Zhang H, Zhao F-J, Sun B, Davison W, McGrath SP (2001) A new method to measure effective soil solution concentration predicts copper availability to plants. Environ Sci Technol 35:2602–2607. doi:10.1021/es000268q
Acknowledgments
We thank Anna Grünwald and René Saladin from the ETH Zürich for their technical assistance and to the Fundación Séneca de la Comunidad Autónoma de la Región de Murcia for financial support for HMC.
Author information
Authors and Affiliations
Corresponding author
Additional information
Responsible editor: Hailong Wang
Rights and permissions
About this article
Cite this article
Conesa, H.M., Schulin, R. & Nowack, B. Suitability of using diffusive gradients in thin films (DGT) to study metal bioavailability in mine tailings: possibilities and constraints. Environ Sci Pollut Res 17, 657–664 (2010). https://doi.org/10.1007/s11356-009-0254-x
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11356-009-0254-x