[Toxicity thresholds and predicted model of Pb added to soils with various properties and its leaching factors as determined by barley root-elongation test].

Ten field soils with various properties were added with Pb at 8 levels, and treated with or without leaching using simulated rain to test the Pb toxicity threshold (EC10, EC50) according to the ISO 11269-1 root elongation toxicity testing method. The leaching factors of Pb toxicity to barley root elongation were determined and the predicted models of Pb toxicity thresholds in soils with various properties were developed. The results indicated that the determined toxicity threshold (EC10, EC50) of Pb varied significantly (P<0.01) among the soils, and the EC10 and EC50 of Pb to barley in the soils ranged from 300-4130 mg . kg-1 and 55-633 mg . kg-1, respectively. The Pb toxicity decreased sharply after leaching treatment. The determined leaching factors (LF) ranged from 0.96-1.96 (LFEC50) and 1.03-1.81 (LFEC10) respectively, and the obvious effect was observed for the Pb toxicity decreasing in the soils with pH<6.81. The predicted models for Pb toxicity thresholds in soils were developed based on main soil properties (soil pH, organic carbon content and cation exchange capacity), and the determined Pb toxicity thresholds (ECx, x = 10,50) in soils fell in the range of mean values with ± 2 standard error (SD) prediction interval for the leached and unleached soils except for the red soil of Jiangxi Province, which indicated that the models based on the main soil properties could well predict the Pb toxicity in soils with various soil properties.

[Effects of aging time on the form transformation and eco-toxicity threshold (ECx) of added Zn in typical China soils].

Six typical China soils with different properties were selected and added with seven concentrations of ZnCl2 to study the effects of different aging time (14, 90, 180, 360, and 540 days) on the form transformation and eco-toxicity threshold (ECx) of added Zn in the soils, with the main affecting factors analyzed. The results indicated that with the increase of aging time, the fraction of 0.01 mol x L(-1) CaCl2-extracted Zn in the soils decreased sharply initially, then slowed down, and reached the dynamic balance after 540 d incubation. The eco-toxicity thresholds (ECx, x = 10, 50) of Zn to bok choy increased significantly with aging time (P < 0.05), which implied the marked decrease of the phyto-toxicity of Zn. The measured aging factors AF10 and AF50 of Zn ranged from 1.077-1.743 and 1.174-1.441, respectively, and increased with aging time. The balanced concentration of Zn in the soils was significantly negatively correlated with soil pH, CEC, and organic carbon (Org-C) content, and soil pH was the most important controlling factor, followed by CEC and Org-C. It took shorter time to reach Zn balance in the soils with higher pH. The prediction model of the ECx of Zn was developed based on the aging factors and the main soil properties, and could be well validated by the measured ECx under field condition. This study would provide theoretical basis for the normalization of the eco-toxicity thresholds of added Zn in different soils and the formulation of the environmental criterion of Zn in China soils.

[Application of nanoscale material in environmental remediation and its eco-environmental toxicity assessment: a review].

Though it has been claimed that nanotechnology has great potential in environmental cleaning, caution is required to the application of nano-particles (<100 nm). The studies relevant to organism exposure have shown that nano-particles can be hazardous. Currently, more papers are available about the remediation efficiency, characteristics, and mechanisms of manufactured nanoparticles after applied into polluted environment, but few studies are conducted about the ecotoxicological effects of the nano-particles. This paper reviewed the current researches on the hazards of nano- or ultrafine particles in environmental detoxification, discussed the potential environmental risks of applying nano-particles, and prospected the perspectives of the nanoparticles in environmental cleaning research.

Effect of bone char application on Pb bioavailability in a Pb-contaminated soil.

The effects of bone char (BC) application on the bioavailability of Pb in a polluted soil from Hunan Province, China were examined. The Pb-contaminated soil was treated with two types of bone char, one from the UK and the other from China. The bioavailability of Pb was determined in terms of the uptake by Chinese cabbage (Brassica chinensis L.), sequential extraction and X-ray diffraction analysis. The results indicate that the Pb concentrations in both shoots and roots decreased with increasing quantities of added bone char, and the application of BC from the UK at the rate of 1.6% (w:w) had the largest effect. Lead Pb concentrations in the shoots and roots decreased by 56.0% and 75.9%, respectively, whereas the application of BC from Zhejiang Province, China at the rate of 1.6% (w:w) reduced Pb concentrations in the shoots and roots to 2.04 mgkg(-1) and 8.42 mgkg(-1), respectively, only 45.8% and 30.2% compared to the control treatment. Sequential extraction results indicate that the addition of bone char, as a metal-immobilizing agent, substantially transforms soil Pb from non-residual fractions to the residual fraction. The transformation was further confirmed using X-ray diffraction studies.