Complete actions

July 2016 - Deliverable A1: Report on analytical and biological characterization of bottom and fly ash, organic materials, soil samples and water samples

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The objectives of Action A1 were: (i) to provide a full characterization of materials with potential use as soil additives; (ii) to provide a preliminary characterization of degraded soils in mining areas in Portugal as well as the collection and characterization of samples to be used in Action A2; and (iii) to select specific types of bottom ash (BA) and fly ash (FA) samples as well as types of organic materials to be mixed and tested as soil additives in Action A2.

At  the  end  of  July  2016,  all  objectives  of  the  action  A1  were  successfully accomplished. Expected results for this action were successfully attained, as summarized next.



Four ash sampling campaigns were conducted in the first six months of 2016 (January, April, May and June) in order to evaluate the seasonal variability of their properties as well as to assess the influence of type of residual forest biomass used as fuel in the pulp and paper industry. Ash from six specific origins was sampled separately. A thorough physico-chemical characterization of biomass ash materials was performed, including the analysis of: pH, moisture content, loss-on-ignition, particle size distribution, major and minor chemical elements, mineralogical analysis by X-ray diffraction, leachability and water soluble chemical elements.



The sludge from a secondary wastewater treatment process was sampled with the same periodicity of ashes from biomass combustion. A thorough physico-chemical characterization of these materials was performed and included analyses of parameters determined by Portuguese Decree-Law 276/2009 on the agricultural use of sewage sludge as well as additional parameters considered necessary in the scope of this project (pH, moisture content, total nitrogen, total phosphorous, major and minor chemical elements, organic contaminants - LAS, NPE, PAH, PCB, PCDD/F - and pathogenic microorganisms).



Two sampling campaigns were performed to collect a total of 122 mining soil samples, divided for the three study areas (Aljustrel – 39 samples; Lousal – 39 samples and São Domingos – 44 samples). A full characterization of the mining soils samples was performed. Soil analyses included: pH; electrical conductivity; loss-on ignition; total and organic carbon; texture; cation exchange capacity; water holding capacity; bulk density; total nitrogen and phosphorous; available phosphorous and potassium; mineralogical analysis; Aqua-regia digestion and analysis of As, Cu, Pb, Zn, Cd, Ni, Cr, Co, Ba, U, Fe, Mn, Al, Sb, Li, Be, Se, B and Mo; total Hg concentrations; extraction of potentially available elemental concentrations (using both 0.43 M HNO3 and 0.01 M CaCl2 extractions).



Soils and materials to be tested in Action A2 were selected.

July 2017: A2. Preparation of soil additives and mesocosm experiments to test their effect on mining soils

 

In this Action, materials previously selected in Action A1 (ashes and organic materials) were tested as soil additives. Methods for preparation, pre-treatment and mixing of materials were developed and optimized. Mesocosm tests (pot and column experiments) were performed to optimize application rates, necessary to achieve the following targets: to correct soil pH, to increase soil nutrient pools, to reduce availability of potentially toxic elements, to avoid salt stress for plants; to comply with the criteria from the ‘Sewage sludge Directive’ (86/278/EEC) and relevant Portuguese legislation Decree-Laws No. 276/2009 (sludge application to agriculture), No. 73/2011 (waste management) and No. 103/2015 (fertilizing materials). The effects of the soil additives on soil properties were quantified.

 

December 2019: Monitoring Actions

 

  • Action C.1 - Technical support – monitoring of soil properties and plant cover during the Pilot Project
  • Action C.2 - Technical support - field and laboratory testing of availability of contaminants to sensitive receptors and ecotoxicological risk assessment
  • Action C.3 - Technical support - monitoring of the impact of soil improvers on soil functions
  • Action C.4 - Monitoring of the socio-economic and environmental impact of project actions


Monitoring Actions (C.1, C.2, C.3, C.4) were all completed.


Major conclusions and outcomes from monitoring Actions were:
 - All the three types of soil improvers (biomass ash granules; biomass ash granules + composted biological sludge; unstabilized mixture of biomass ash and biological sludge) developed and tested in the project allowed to restore the chemical and ecological quality of severely degraded mining soils suffering from extreme pollution with heavy metals, salinity and low pH;
 - Long-term effects of the new soil improvers included: neutralization of soil acidity (from pH 3.3-4.5 to pH values in the range of 4.8-7.6); increase in soil total organic carbon (from 0.3-0.7% to 4% TOC); increase in the soil water holding capacity (from 0.3 to 0.6 L/kg); significant increase the fraction of available nutrients (namely Ca, K, Mg, P); significant decrease in lability of potentially toxic elements in soils (Al, Cd, Co, Cu, Mn, Ni, Pb and Zn);
 - All the three types of soil improvers promoted plant growth in otherwise unvegetated soils; significantly increased soil microbial biomass and activity; and significantly improved survival and reproduction of soil organisms;
 - The combined application of stabilized biomass ash granules + composted sludge exhibited the best balance between maximization of environmental and social-economic benefits and minimization of potential environmental risks among the three treatments tested (and when compared with commercial potential alternative solutions from the market).