[Revaluation of soil heavy metals pollution in Zhangshi irrigation area of Shenyang and analysis of Cd forms in soil].

This paper revaluated the situation of cadmium (Cd) pollution in rice field soils of Zhangshi irrigation area in Shenyang. The results indicated that the soil Cd pollution of test area was still quite serious. The Cd content in brown rice samples ranged from 0.435 to 0.855 mg x kg(-1), which exceeded the national criteria for food sanitation in China, and increased by 335%-755% compared with that 20 years ago. Brown rice Cd had a significant negative correlation with soil pH, and a positive correlation with soil available Cd. The decrease of soil pH induced more soil Cd transformed into available Cd which occupied 22.8%-52.0% of the total Cd and was easy to be absorbed by rice plant, inducing the Cd in brown rice exceeded national criteria. The pollutant Cd could transfer along with surface runoff, ground water and flying dust, making the pollution extend gradually.

Impact of anions on the heavy metals release from marine sediments.

Marine sediments from Lianshan Bay in Huludao, China, were studied in laboratory. A series of simulated experiments were carried out to investigate the influences of three kinds of anions Cl-, SO42- and HCO3 on the release of Cd, Pb, Cu and Zn from the sediments. The results showed that the sequences about the impact of the three anions were Cl- >HCO3 > SO42. The release potential of heavy metals in the presence of each anions was in the following order: Cd>>Cu>Zn approximately equal to Pb. The correlations were positive between Cl content and the quantity of Cd released from the marine sediment, whereas there was no significant relationship between Cl-content and amount of Cu and Zn released. For SO42- and HCO3-, the release of the heavy metals from marine sediments was not obvious.

Selective extraction and separation of Fe, Mn oxides and organic materials in river surficial sediments.

In order to investigate the adsorption mechanism of trace metals to surficial sediments (SSs), a selective extraction procedure was improved in the present work. The selective extraction procedure has been proved to selectively remove and separate Fe, Mn oxides and organic materials (OMs) in the non-residual fraction from the SSs collected in Songhua River, China. After screening different kinds of conventional extractants of Fe and Mn oxides and OMs used for separation of heavy metals in the soils and sediments, NH2OH x HC1 (0.1 mol/L) + HNO3 (0.1 mol/L), (NH4)2C204 (0.2 mol/L) + H2C2O4 (pH 3.0), and 30% of H2O2 were respectively applied to selectively extract Mn oxides, Fe/Mn oxides and OMs. After the extraction treatments, the target components were removed with extraction efficiencies between 86.09% -93.36% for the hydroxylamine hydrochloride treatment, 80.63% -101.09% for the oxalate solution extraction, and 94.76%-102.83% for the hydrogen peroxide digestion, respectively. The results indicate that this selective extraction technology was effective for the extraction and separation of Fe, Mn oxides and OMs in the SSs, and important for further mechanism study of trace metal adsorption onto SSs.