Olive mill waste biochar: a promising soil amendment for metal immobilization in contaminated soils

Abstract

The potential use of biochar from olive mill waste for in situ remediation of metal contaminated soils was evaluated. Biochar was mixed with metal contaminated soil originating from the vicinity of an old zinc smelter. Soil-biochar mixtures were equilibrated for 30 and 90 days. At these time points, Ca(NO3)2 exchangeable metals were determined, and effects of the biochar amendment on soil toxicity were investigated using plants, bacteria, and earthworms. Bean (Phaseolus vulgaris) growth, metal content, antioxidative enzymes activities, and soluble protein contents were determined. Furthermore, effects on soil microbial communities (activity, diversity, richness) were examined using Biolog ECOplates. After 120 days of soil-biochar equilibration, effects on weight and reproduction of Eisenia foetida were evaluated. With increasing biochar application rate and equilibration period, Ca(NO3)2 exchangeable metals decreased, and growth of bean plants improved; leaf metal contents reduced, the activities of antioxidative stress enzymes decreased, and soluble protein contents increased. Soil microbial activity, richness, and diversity were augmented. Earthworm mortality lowered, and their growth and reproduction showed increasing trends.

Using bamboo biochar with compost for the stabilization and phytotoxicity reduction of heavy metals in mine-contaminated soils of China

“…Another study reported as high as 55–78, 29–50 and 11–46% decreases in Zn, Pb and Cd, respectively after 90 days of incubation 13 . The soil pH increased after the application of BB in FC and TG soil.…”

“…Similarly, another study reported significant ( p  < 0.05) increases of 18 and 77% at 0.5 and 8% biochar amendments, respectively 11 . It is observed that higher doses of BB reduced the bioavailability of HMs, which minimized plant stress 13 . Biochar proved to be an effective amendment to reduce plant stress and facilitate the establishment of Brassica in the smelter/mine-polluted soil of FC and TG.…”

“…HMs induced ROS (reactive oxygen species) impair the biosynthesis of chlorophyll and carotene in plant cells, which can lead to leaf chlorosis 9, 13 . The application of bamboo biochar significantly increased chlorophyll ( a and b ) and the effect on the carotenoid content in Brassica leaves was not significant ( p <  0.05).…”

“…The reduced antioxidant enzyme activities can be associated to the HMs immobilization effect of BB followed by decreased metal translocation into plant tissues. This led to stress reduction at a cellular level in Brassica 13 .…”

Potential use of Sorghum bicolor and Carthamus tinctorius in phytoremediation of nickel, lead and zinc

“…In recent years, scientists generated cost-effective technologies, including the use of immobilizing soil amendments such as compost , biochar (Hmid et al 2014), bagasse fly ash (Gupta and Ali 2004;Gupta et al 2003; (Gupta and Ali 2000) and/or plants to clean polluted areas. Various additives were applied as soil Dipartimento di Scienze per l'Ambiente, Università degli Studi di Napoli ''Parthenope'', Via F. Acton, 38, 80133 Naples, Italy amendments to reduce metal plant uptake (Vangronsveld et al 2009).…”