Calcined Oyster Shell-Humic Complex as Soil Amendment to Remediate Cd- and As-Contaminated Soil

Abstract

Soil acidification in the subtropical region reduces soil productivity and increases the bioavailability of heavy metal(loid)s in soil. Here 800 °C-calcined oyster shell and leonardite-derived humic substance were combined to form a Ca-humic complex to remediate an acidic soil contaminated by cadmium (Cd) and arsenic (As) for safe vegetable production. In the pot experiment, the complex was added to soil as a soil amendment at 0%, 0.5%, 1.0%, 2.0%, and 5.0%. A 2.0% dose reduced Cd and As contents of the vegetable bok choy by 98% and 71%, respectively, alleviating the human health risk of Cd and As from the food chain. The unified bio-accessibility method (UBM) was followed to estimate the bio-accessibility of Cd and As. The complex at a 2.0% dose lowered soil Cd and As bio-accessibility in simulated gastric (BioG) and intestine (BioGI) compartments by 15.5% for BioG-Cd, 39.2% for BioGI-Cd, 28.8% for BioG-As, and 45.0% for BioGI-As, thus reducing the human health risk of Cd and As from soil ingestion. The use of oyster shell waste to produce Ca-humic complex as a soil amendment is a practical means of achieving dual agronomic and environmental benefits, from the remediation of soil contamination to the safe disposal of shell waste.

Enhancing Soil Remediation of Copper-Contaminated Soil through Washing with a Soluble Humic Substance and Chemical Reductant

“…These results could be attributed to Cu resorption in the soil, Cu complexation with pepsin, or chemical precipitation of metals caused by the higher pH environment of the intestinal compartment [31]. The reducing agent's complexation with Cu makes them less soluble in the simulated gastric and intestinal environment [45]. Moreover, Cu had a higher bioaccessibility in the gastric compartment than in the intestinal one, mainly because the former had a much lower pH than the latter.…”

Humic Substances: Importance for Agriculture, Affinity and Interactions with Soil Amendments and Pollutants

“…In "Calcined Oyster Shell-Humic Complex as Soil Amendment to Remediate Cd-and As-Contaminated Soil" by G. Yuan, D. Bi, J. Wei, and L. Xiao, a Ca-humic complex from leonardite-derived humic substances was prepared and employed as a soil amendment to remediate an acidic soil contaminated with Cd and As for the production of consumptionsafe vegetables [2]. Pot experiments with bok choy vegetables demonstrated that the Ca-humic complex decreased the Cd and As contents in the plant by 98% and 71%, respectively, and lowered the soil Cd and As bio-accessibility in simulated gastric and intestinal compartments, reducing health risks for humans.…”