Influence of sample matrix on the alkaline extraction of Cr(VI) in soils and industrial materials

An accurate and efficient determination of the highly toxic Cr(VI) in solid materials is important to determine the total Cr(VI) inventory of contaminated sites and the Cr(VI) release potential from such sites into the environment. Most commonly, total Cr(VI) is extracted from solid materials following a hot alkaline extraction procedure (US EPA method 3060A) where a complete release of water-extractable and sparingly soluble Cr(VI) phase is achieved. This work presents an evaluation of matrix effects that may occur during the hot alkaline extraction and in the determination of the total Cr(VI) inventory of variably composed contaminated soils and industrial materials (cement, fly ash) and is compared to water-extractable Cr(VI) results. Method validation including multiple extractions and matrix spiking along with chemical and mineralogical characterization showed satisfying results for total Cr(VI) contents for most of the tested materials. However, unreliable results were obtained by applying method 3060A to anoxic soils due to the degradation of organic material and/or reactions with Fe2+-bearing mineral phases. In addition, in certain samples discrepant spike recoveries have to be also attributed to sample heterogeneity. Separation of possible extracted Cr(III) by applying cation-exchange cartridges prior to solution analysis further shows that under the hot alkaline extraction conditions only Cr(VI) is present in solution in measurable amounts, whereas Cr(III) gets precipitated as amorphous Cr(OH)3(am). It is concluded that prior to routine application of method 3060A to a new material type, spiking tests are recommended for the identification of matrix effects. In addition, the mass of extracted solid material should to be well adjusted to the heterogeneity of the Cr(VI) distribution in the material in question.

A world soils agenda: Discussing international actions for the sustainable use of soils

Promoting sustainable forms of natural resource management is a challenge land users are unable to tackle solely on their own initiative. Soil and land degradation remains an unresolved problem of global environmental change. There is a need for concerted international action that directly addresses this issue at the global level. A discussion of action to promote the sustainable use of soils and land took place in a working group established by the International Union of Soil Sciences (IUSS) in 1998. The present publication reports on the results of this discussion and proposes that the international community establish a ‘world soils agenda’ that will enable the scientific community, international institutions and their national partners to work together towards the common goal of safeguarding soils and land as resources central to our own survival as well as the Earth’s biological wealth.