Allelopathic effect of rhubarb extracts on the growth of Microcystis aeruginosa.

With its advantages of ecological safety, environmental affinity, and high selectivity, allelopathic technology has been widely developed for algae inhibition. However, obtaining effective allelochemicals and realizing their mechanism are difficult. In this paper, a Chinese herbal medicine, namely, Rheum palmatum L. (Chinese rhubarb), was utilized as a source of allelopathic substances for the first time. Four units of rhubarb organic extracts were collected to study the inhibition of growth, photosynthesis, proteins, and algal toxin of Microcystis aeruginosa. Results showed that the ethyl acetate, n-butanol, and aqueous phases of the rhubarb extracts have notable inhibitory effects. After a 16-day treatment, the four extracts reduced M. aeruginosa by 64.1%, 59.3%, 61.9%, and 7.2% with disruption of algal photosynthesis and protein synthesis and reduction of algal toxin.

Experimental study on cyanide-contaminated soil (China) treatment by leaching and decomposition.

The removal of cyanide compounds in soil by leaching was investigated in flask and column tests. All the experiments were conducted under alkaline conditions to prevent loss of hydrogen cyanide. Results showed that leaching progressed rapidly when the leaching temperature or the initial cyanide concentration was high. The obtained cyanide data in the flask test fitted an inner diffusion process, as described by a shrinking core model. In the batch column test, the cyanide concentration decreased from 44.06 to 9.86 mg/kg when the leaching intensity was 79 L/(m2 h) after 23.8 h leaching. The leaching process for the cyanide compounds was divided into two stages according to the batch column test despite the decrease in the leaching velocity as the cyanide concentration in soil declined. Cyanide removal in the batch column test was better than that in the flask test due to the higher gradient of cyanide concentration. The aqueous solution containing cyanide compounds was decomposed effectively by the hybrid process of ozone and UV rays. Furthermore, the leaching and decomposition of the soil and leaching wastewater were performed with a continuous column test with circulating leaching liquid. The cyanide compounds in the soil and wastewater were removed effectively.