Phytoremediation of heavy metals and PAHs at slag fill site: three-year field-scale investigation

Big Marsh is a 121-hectares site, representative of many other sites in the Calumet region (near Chicago, IL, USA), which has been significantly altered by the steel industry and decades of legal and illegal dumping and industrial filling. The slag-containing soil at the site has been found to be contaminated with polycyclic aromatic hydrocarbons (PAHs) and heavy metals. Due to the large size of the site to be remedied, and variable distribution of the contaminants throughout the shallow depth at slightly above the risk-based levels, phytoremediation is considered as a green and sustainable remedial option. The objective of this work was to investigate the use of phytoremediation in a three-year field-scale study, specifically determine plant survival and the fate of PAHs and heavy metals in soil and plant roots and stems. Replicate test plots were prepared by laying a thin layer of compost at the ground surface and then tilling and homogenizing the slag–soil fill to a depth of approximately 0.3 m. Nine native and restoration plant species were selected and planted at the site, and their survival and growth were monitored and fate of contaminants in soil and plants were also monitored for three growing seasons. Sequential extraction procedure was performed to determine the fractionation of the heavy metals in soils before and after planting. The results showed a decrease in PAHs concentrations in the soil, probably due to enhanced biodegradation within rhizosphere. No significant decrease in heavy metal concentrations in soil was found, but they were found to be immobilized. Contaminant concentrations were found below detection limits in the plant roots and shoots samples, demonstrating insignificant uptake by the plants. Overall, selected native grasses in combination with compost amendment to the soil proved to be able to survive under the harsh site slag fill conditions, helping to degrade or immobilize the contaminants and reducing the risk of the contaminants to public and the environment

Enhancing water resistance of earthen buildings with quicklime and oil

Earth as a building material is a very sustainable construction option. The vulnerability of earthen buildings to water action by rain, floods or capillary absorption is the main concern, especially in countries with a high rainfall. The historical earthen buildings that have survived these actions until today demonstrate that it is possible to build durable earthen constructions. A successfully used technique in ancient buildings is the incorporation of natural products with water resistant properties, such as oils, fats and other materials generally referred to as biopolymers. Another common practice has been the use of lime (slaked or quicklime) for stabilizing soils. The main aim of this research is to improve the resistance of compressed soil against rainwater action. For this purpose, ancient and contemporary knowledge was analysed. Different mixtures of stabilized soil were studied in order to test the effects of quicklime, oils and a mineral additive. The main results obtained in this research showed that quicklime leads to increased performance in compressive strength and significantly reduced erosion in the accelerated erosion test of rain simulation. This study provides a contribution to the scientific knowledge required to achieve increased durability for new earth buildings, as well as for conservation of existing earthen construction heritage, preserving the sustainability of the construction.(undefined)info:eu-repo/semantics/publishedVersio

Biomass bottom ash waste and by-products of the acetylene industry as raw materials for unfired bricks

This research aims to study the feasibility of using wastes: biomass bottom ash resulting from the combustion process of a mix of pine-olive pruning in power generation plants, and Geosilex, a by-product obtained in the acetylene industry, as raw materials in the manufacture of unfired bricks. These materials were characterized physically, chemically and mineralogically. Different proportions of raw materials have been investigated; biomass bottom ash (100-20 wt %) and Geosilex (0–80 wt %). The specimens were obtained by compression at 10 MPa and cured for 28 days in water. The physical, mechanical and thermal properties of the unfired bricks have been evaluated. Optimum results have been obtained for specimens with 70–60 wt % of biomass bottom ash and 30–40 wt % of Geosilex, presenting the best mechanical properties, with compressive strength values of 52 MPa and thermal conductivity of 0.52–0.57 W/mK, respectively. These unfired bricks presented a greater quantity of hydrated calcium silicates and hydrated calcium aluminates that provide mechanical properties. This fact is due to that these specimens had the optimal amount of pozzolanic materials, Ca(OH)2 present in the cementing agent Geosilex and SiO2 and Al2O3, present in the ash. Recycling these raw materials in unfired bricks implies significant economic and environmental benefits owing to wastes are used as substitutes for natural raw materials