Lead dissociation and redistribution properties of actual contaminated farmland soil after long-term EKAPR treatment.

Electrokinetic-assisted phytoremediation (EKAPR) is a potential technology much affected by the metal species and accessibility to plant roots. In this study, Pb-contaminated red soil was remediated with Sedum plumbizincicola to investigate the changes in soil pH, available nutrients, dissociation and redistribution of Pb under a long-term periodic reversal direct-current electric field. This approach could effectively activate soil P, K, organic matter (OM) and Pb, without significant soil acidification; the effect was positively correlated with applied voltage. Soil Pb can be continuously dissociated, migrated, and tended to accumulate in the middle region. The maximum Pb removal rate in the anodic section of the EKAPR system was 21.4%, and the aggregation rate in middle regions was 14.4%, higher than the available Pb content of the original soil. The Pb desorption in aqueous solution increased significantly with increasing voltage, irrespective of the solution pH. At a voltage of 20 V, the Pb cumulative desorption content reached 91.1 mg kg-1 (pH = 7), which was 2.7 times than that without electric field (33.2 mg kg-1). Compared to original soil (2.80 mg kg-1) and the control (14.54 mg kg-1), the available Pb in the anode section of EKAPR system (20.66 mg kg-1) increased by 637.9% and 42.1%, respectively. These results indicated that except for the indirect influence of soil pH changes, electrodynamics can directly promote the bioavailability and dissociation of Pb at the soil-water interface. This finding provides a new perspective for further studies on the mechanism of Pb speciation evolution and accumulation changes using EKAPR.

[Origin traceability of main root of spring Panax notoginseng based on stable isotope fingerprint].

This paper established the identification technology of the main root origin of three-year-old spring Panax notoginseng aiming at providing theoretical basis for the protection and traceability of geographical indication products of P. notoginseng. Forty-four samples of three-year-old spring P. notoginseng from Guangxi Baise, Yunnan Wenshan, Yunnan new cultivating regions. The stable isotopic ratios of carbon, nitrogen, hydrogen and oxygen were determined by elemental analysis and stable isotope mass spectrometer. Combined with Duncan multiple comparative analysis, fisher discriminant analysis and sequential discriminant analysis, a origin discriminant model for the main root of three-year-old spring P. notoginseng was established for 3 production areas of P. notoginseng. The geographical climate and environment of three production areas of P. notoginseng are obviously different. From Guangxi Baise-Yunnan Wenshan-Yunnan new cultivating regions, the longitude, average annual temperature and annual precipitation gradually decrease, and the elevation and latitude are increasing. The results of multiple comparative analysis showed that there were significant or very signi-ficant differences in the δ~(13)C,δ~(15)N,δ~2H,δ~(18)O of the main roots of P. notoginseng in three regions. The results of fisher's discriminant analysis and sequential discriminant analysis showed that the correct discriminant rates of the main roots of P. notoginseng for three regions were 80.05%,76.47% and 90.91%, respectively, based on four stable isotope ratios, with an average of 84.09%. Using stable isotope fingerprint and chemometrics method, we can distinguish the origin of the main raw materials and products of P. notoginseng.

[Study on correlations between total saponins content in rhizome or mycorrhizal infection rate of Pairs polyphylla var. yunnanensis and soil factors].

OBJECTIVE: Through correlation and path analysis between total saponins content in rhizome/mycorrhizal infection rate in roots of Pairs polyphylla var. yunnanensis and soil factors, to make an inquiry into the role of soil factors in the quality formation of P. polyphylla var. yunnanensis. METHOD: Tested total saponins in rhizome, mycorrhizal fungal infection rate in root and physical and chemical properties in rhizosphere soil in 25 different growth areas, and statistically analyzed the relationship between total saponins in rhizome/mycorrhizal infection rate in roots of P. polyphylla var. yunnanensis and soil factors by using correlation and path analysis. RESULT: The symbiosis relationship between AM mycorrhizal and roots of P. polyphylla var. yunnanensis were better established under natural condition, of which the infection ratio between 36.41%, 83.37%. There were significantly positive correlation between total saponins content in rhizome and urease activity or alkaline phosphatase activities or organic matter in soil, but there was significantly negative correlation between total saponins content and bulk density. There was significantly positive correlation between AM infection ratio and alkaline nitrogen. Path analysis indicated that total saponins of rhizome mainly affected by alkaline nitrogen in soil rhizosphere, secondly by soil organic matter and soil urease activity. While the mycorrhizal fungal colonization ratio was mainly affected by soil pH, secondly by alkaline nitrogen, urease activity, and available phospherus in soil. CONCLUSION: There is closed relationship between quality formation of P. polyphylla var. yunnanensis and soil factors. Path analysis is better for reflecting the contribution of soil factors to total saponins and mycorrhizal infection ratio.