Projects / Programmes
Quality and functioning of contaminated garden soil as a plant substrate after remediation
| Code |
Science |
Field |
Subfield |
| 4.03.02 |
Biotechnical sciences |
Plant production |
Soil and micro-climate |
| Code |
Science |
Field |
| B410 |
Biomedical sciences |
Soil science, agricultural hydrology |
| Code |
Science |
Field |
| 4.01 |
Agricultural and Veterinary Sciences |
Agriculture, Forestry and Fisheries |
Soil quality and functioning, food production, contamination, remediation
Researchers (16)
Organisations (2)
Abstract
Millions of hectares of agricultural land are contaminated world-wide. Soil degradation processes, now already enhanced by the effects of climate change, will increase the tendency to use contaminated land for food production, thus increasing the human health risk. Remediation technologies have the potential to preserve now contaminated soil for the safe production of food. However, before these emerging technologies are applied in full-scale, the effect of remediation on the long-term quality and safety of soils and on crops and vegetables grown on remediated soil need to be carefully examined. Currently there is almost no data on these effects in scientific literature.
Soil washing with chelants is an effective and potentially soil-friendly remediation option for heavy metal contaminated soils. However, soil washing cannot remove heavy metals from soil entirely, even at high chelant-to-metal ratios, and the long-term risks associated with residual heavy metals are still largely unknown.
The aim of the proposed project is a comprehensive analysis of the effects of soil washing with chelant EDTA on quality of Pb, Zn and Cd contaminated garden soil from the contaminated site in Mežica Valley, Slovenia. This goal will be achieved through the following project objectives:
1.) The remediated soil produced within an on-going pilot-scale remediation project will be used to design experimental plots for the growth of selected vegetables and crops.
2.) We will annually assess the quality of remediated garden soil by measuring soil physico-chemical, biological and toxicological properties.
3.) We will assess the safety of a variety of vegetables and crops produced on remediated soil, by determining the transfer of Pb, Zn and Cd, residual in soil after remediation, into the different parts of plants.
4.) We will study the plant performance on remediated soil by assessing their photochemical efficiency, photosynthetic activity and yield.
5.) We will investigate the dynamics of ecological successions in remediated soil, biodiversity, ability to form mycorrhizae, and soil functioning regarding the C and N cycle.
Furthermore:
6.) We will attempt to further the development of soil washing remediation technology by introducing a novel electrochemical method of EDTA recycling.
Significance for science
Soil contamination, caused by the large amounts of manmade pollutants and chemicals that are being anchored into agricultural and urban soils every day, is becoming a major problem. Many cities in Europe formed from an industrial nucleus and have inherited a long industrial history and an associated legacy of urban soil contamination. In particular toxic metals (commonly referred as heavy metals) are the main causes of concern as they are nondegradable and persists in the soil. Historically, excavation to landfill (dig and dump) has been the solution, offering a quick removal mechanism of a pollution source in the soil. Europe is now implementing the Landfill Directive (1999/31/EC) with heavy restriction on landfill and other treatments are needed to meet the need for remediation. Recently we demonstrated, first in laboratory and after in a pilots-cale level, the performance of the novel chelant-based soil washing technology for remediation of multi-metal (Pb, Zn and Cd,) contaminated soils from Meza Valley, Slovenia. In this novel technology the chelant (ethylenediamine tetraacetate, EDTA) and process water recycling relies on a combination of substitution / precipitation reactions in an imposed pH gradient for EDTA recovery, and on electrochemical polishing of process waters for total water recycle in a closed loop. By using Ca(OH)2 and H2SO4 as the base / acid pair the accumulation of added reagents in the process water after multiple soil remediation batches/recycles is prevented by precipitation and removal of poorly soluble CaSO4 during the process. Even though EDTA remediated soil effectively lowers the human health risk and leaching hazard, the remediated soil are deprived of micronutrients (removed collaterally with toxic metals) and most of the microbial life (depressed in stringent conditions of soil extraction) and has disturbed soil structure. Within the project the quality (chemical, physical and biological parameters), nutritional status and functioning of remediated soil was investigated. For revitalization of remediated soil complex and specific fertilizers, different fertilization strategies, composts, microbial inoculants and other amendments were investigated. Results of this project confirmed the (technical and economic) feasibility of effective remediation of toxic metal contaminated soils from Meza Valley. Soil concentration and availability (toxicity) of Pb Zn and Cd were significantly reduced. We confirmed the feasibility of revitalization measures to restore remediated soil into productive, fertile, healthy and safe plant substrate.
Significance for the country
The Meza Valley encompasses approximately 50 km2 in northern part of Slovenia and includes abandoned lead mining and smelting industrial complex and numerous confined and unconfined deposits. Specific topology and 500-years of mineral industry releases resulted in metal contamination of soils across all region. The site is home to more than 6000 people in three residential communities. Cities of Mezica, Crna and Zerjav (with Pb soil concentration up to 8000 mg kg-1) were developed around historically known locations of past Pb smelters. All three areas exhibit soil Pb concentrations well above critical value stipulated by Slovenian legislation. First analyses of blood Pb concentrations for the inhabitants of the Meza Valley were carried out during 1974 – 1976. The median blood Pb concentration of preschool children was over 400 µg-l. In 2007 the on-going Action program for improving the quality of the environment in Meza Valley was implemented. Despite accepted measures results of annual surveys of Pb blood concentration indicated that the number of children with levels higher than 100 ng L-1, stipulated by Slovenian legislation as hazardous, did not significantly change. To predict the risk of elevated blood Pb levels in children which are exposed to Pb USEPA introduced the Integrated Exposure Uptake Biokinetic (IEUBK) model. Using this model we concluded that Pb soil contamination is the main environmental factor explaining the elevated Pb blood level in children in the Meza Valley. For soils from Meza Valley we developed technically and economically feasible remediation technology. Geostatistical simulations showed that the contaminated area covers 19.4 km2 and that soil remediation has the potential to reduce the area with Pb above the critical regulatory threshold limit (530 mg kg-1) by 91%. The aim of current study was to investigate the potential of EDTA-based soil remediation in Meza Valley to reduce children’s risk from Pb poisoning. The total soil Pb concentration and concentration of bio-available Pb before and after EDTA extraction of soils from multiple locations in cities of Mezica, Zerjav and Crna in Meza Valley were measured and used in IEUBK model to predict Pb blood level in children before and after soil remediation. Mean blood Pb level before and after remediation was 93 and 48 µg L-1, 244 and 144 µg L-1, 115 and 54 µg L-1 for Mezica, Zerjav, Crna, respectively. The results of our study therefore indicate that except for city of Zerjav, the soil remediation has potential to decrease the blood Pb concentration in children under the level of concern. As a project partner Envit nvironmental technologies and engineering Ltd cooperated with Biotechnical Faculty, University of Ljubljana. Envit Ltd is an SME and has status of a private research organisation. The company was awarded in 2010 as the best startup company in Slovenia. Envit Ltd is leading partner in Life+ project ReSoil – development of demonstrational soil remediation facility with capacity 6 ton of soil per day in Meza Valley, Slovenia (LIFE 12 ENV/SI/000969)., based on patented technology developed largely within this completed project. Opportunity was give to pre-graduate and graduate students to work as a part of the project team. During the project 9 diploma (M.Sc) and 6 doctoral (Ph.D.) theses were completed.
Most important scientific results
Annual report
2011,
2012,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2011,
2012,
final report,
complete report on dLib.si
