Residue from coal combustion for plastic soil improvement

The combustion of coal in Hoffman-type furnaces generates ash as one of the process residues. This research seeks to make use of this residue to improve plastic subgrade soils in tertiary roads, considering that in Colombia a large percentage of these are not paved. A soil with high plasticity has been selected to make mixtures with ash dosages that vary from 0% to 15% with respect to the dry weight of the soil. To determine the variation of the physical and mechanical properties of the soil-ash mixtures tests of consistency limits, compaction tests, and California bearing ratio were carried out. The results showed that the mixture in which 12% of the coal combustion residue is added to the soil, as a percentage for the dry weight of the soil, has a better physical behavior and bearing capacity than the soil in its natural state. obtaining an increase of up to 75% in the California bearing ratio.

Heavy Metal Contamination and Its Risk for Swampy Agricultural Soils of Keffi, Nasarawa West, Nigeria

Swampy agricultural soils could be contaminated as a result of accumulation of heavy metals through emission from industrial areas, mines tailings, metal wastes, gasoline, paints, fertilizers, manure, sewage sludge, pesticide, waste water irrigation, coal combustion residue, spillage of petrochemicals and atmospheric deposition. This study aimed at evaluating the carcinogenic and non-carcinogenic risk of the study area using X-Ray fluoroscopy. The results shows that, mean concentration level in the area was in decreasing order Ni(525) > Cu(515.9) > Zn(367.6) > Cr(336.6) > Cd(260.9) > Pb(219.5) > As(18.9). The Hazard Quotient (HQ) was all recorded to be low except ingestion adult which is higher than unity. The Hazard Index (HI) was also recorded to be 2.3 a value greater than one (>>1). This makes non-carcinogenic effects significant to the population and poses serious effects in the area under study. The total excess life cancer risk were found to be (5.0 x 10-2), a value greater than that of U.S (1.0x10-4 to 1.0x10-6) and above that of South Africa (5.0x10-6). This implies that there is a probability that one person in 1,000 may be affected. Regular monitoring and evaluation of the soils and the crops cultivated at the sample locations is recommended.