[Mechanism of Soil Eco-Functional Stability Under Pyrene/Cadmium Simplex and Combined Pollution Stress].

In current scenario,the soil pollution has become very severe and its effects on agricultural and ecological security issues cannot be ignored as various contaminants are discharged into soil.Thus,the soil pollution is exigent and has to be solved.This research took soil resistance (Rt),resilience (Rl) and stability (Sb) as evaluation indexes for judging soil quality by exerting different concentration (concentration ratio) gradient of pyrene (PYR),cadmium (Cd) and pyrene/cadmium (PYR/Cd) combined pollutants.A sympathetic description was showed from the aspects of microbial activity,diversity and abundance of soil ecosystem,and the models were constructed to describe the dose-response relationship between PYR-Sb and Cd-Rt.The research showed that different types of pollutants had certain inhibition on soil DOC content.In Cd and PYR simplex pollution,soil microbial mean biomass and colony number decreased with increasing concentration of pollutants.In PYR/Cd combined pollution,the ratio of PYR and Cd had a negative correlation with the decreasing rate of DOC and resistance,meanwhile Cd had a prominent influence on the above-mentioned correlations,in other words,the soil with higher concentration of Cd had lower DOC decrease rate and resistance,and Cd would have dominant inhibition effect on microorganisms under PYR/Cd combined pollution.In addition,this study found the significant correlation of cPYR-Sb and cCd-Rt,and built the binomial forecasting model to describe the dose-response relationship of cPYR-Sb and cCd-Rt.

Kinetics and mechanism of 2,3,5,4'-tetrahydroxystilbene-2-O-ß-d-glycoside (THSG) degradation in aqueous solutions.

The hydrolytic kinetics and degradation mechanism of 2,3,5,4'-tetrahydroxystilbene-2-O-ß-d-glycoside (THSG) extracted from Radix Polygoni Multiflori (a commonly used official Chinese herbal Heshouwu), were investigated using reversed-phase high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS). The influences of pH (1.5-9.9), temperature (25-60°C) and irradiation on the hydrolysis of THSG were studied in aqueous solutions. The results showed that the degradation of THSG was pH-, temperature- and irradiation-dependent and all followed first-order kinetics. The effect of temperature on the rate of THSG degradation was characterized using the Arrhenius equation. Maximum stability of THSG was found at pH 1.5 (t(0.5)=47.57 d). THSG was unstable in alkaline and irradiation conditions. The active energy (E(a)) of THSG degradation in aqueous solution at pH 6.8 (most frequently adopted extract solvent) under lucifugal and irradiation conditions was 47.7kJmol(-1) and 25.3kJmol(-1), respectively. Three hydrolytic products of THSG were identified by LC-MS. Cis-trans isomerism took place under irradiation, and hydrolysis took place in acid-base conditions. Moreover, further oxidation on aglycon occurred after hydrolytic cleavage of phenolic glycoside in acidic conditions. The possible hydrolytic pathways of THSG are proposed.