The Effect of Compost and Fly Ash Treatment of Contaminated Soil on the Immobilisation and Bioavailability of Lead

Monika Jakubus,Małgorzata Graczyk

doi:10.3390/agronomy11061188

Abstract

The study discusses changes in lead contents in soil and crops after application of compost and fly ash. A three-year experiment was conducted on narrow-leaved lupine (Lupinus angustifolius L.), camelina (Camelina sativa L.) and oat (Avena sativa L.), which were grown on medium soil fertilised with compost or fly ash (FA). The lead amounts in various combinations were evaluated using sequential (BCR analysis) and single (DTPA solution) methods. The total contents of lead and amounts of selected macronutrients were assessed in the biomass of plants. The Pb contents in the soil and plants were used to calculate the risk assessment code (RAC), individual contamination factor (ICF), bioconcentration factor (BCF) and contamination coefficient level (CCL). Lower amounts of bioavailable Pb in the soil were observed as a result of compost and FA application. Fly ash immobilised Pb more effectively, as evidenced by the BCF and CCL values. The increase in the Pb contents in the sequentially separated fractions and in plant biomass were caused by applied compost or FA. The Pb contents in exchangeable forms decreased, whereas its contents in residual forms increased.

Highlights

In recent decades heavy metal contamination has become a global problem and was listed as a threat to soil in The Thematic Strategy for Soil Protection—a document published by the European Commission in 2006 and updated in 2012 [1]
Compost made from biowaste and manure mixed at a 1:1 ratio and fly ash (FA) formed as a by-product of lignite combustion were used as immobilising agents
The Pb content in Fr. 2 in the soil with FA was lowest in the first year of the study, but it increased in the subsequent years

Summary

Introduction

In recent decades heavy metal contamination has become a global problem and was listed as a threat to soil in The Thematic Strategy for Soil Protection—a document published by the European Commission in 2006 and updated in 2012 [1]. Oil drilling, mining, smelting, improper disposal of sewage sludge and other human activities have heavily polluted soil with various heavy metals and considerably reduced its fertility [2]. This element is considered as the most problematic and toxic heavy metal among toxic threats among all the substances on earth because of its risk of global health impact [3]. Authors of recent studies have emphasised its negative impact on the quality of crops, its easy incorporation in the food chain and the resulting threats to human health [4,5]. In view of the need to protect the soil environment and produce uncontaminated food, it is necessary to control agricultural soils for their

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