The Use of Leaching Tests to Study the Potential Mobilization of Heavy Metals from Soils and Sediments: A Comparison

摘要

In the present study, different leaching testswere applied on well-characterised samples in orderto obtain information on the potential mobility ofheavy metals and arsenic. The information deducedfrom the different methods was compared andevaluated. Besides the comparison of heavy metalrelease in cascade-, column- and pHstat leaching tests,attention was also paid to the assessment of releasekinetics during leaching tests and to the mathematicalmodelling of leaching behaviour. The aim of thisstudy was to understand the origin of possiblediscrepancies between the results of different leachingtests. The compatibility of the results of differentleaching tests is, besides the inherent differencesbetween methods (single batch tests versus dynamicleaching tests, the duration of the tests, liquid/solid(L/S) ratio,…) to a major extent determined by keyfactorssuch as pH and redox potential. Depending onsoil and sediment properties (e.g. acid neutralizingcapacity (ANC)) these ‘key-factors’ varied during andat the end of extractions and leaching tests, even whenthe initial test conditions (e.g. the pH of the reagent)were equal for all test cases. During cascade- andcolumn leaching tests, pH (which is initially 4) willmostly increase, but the extent of this pH-increasemainly depends on the acid neutralizing capacity ofthe sample. Therefore, measuring the pH of allleachates that are collected during these tests ismandatory for the interpretation of the results.Moreover, the monitoring of other variables such asDOC, anions and major elements can give indicationson the reactions that are responsible for the release ofelements (e.g. the dissolution of organic matter) andgreatly improve the interpretation of the results.