Shugui Dai

Plant uptake of aldicarb from contaminated soil and its enhanced degradation in the rhizosphere

Experiments were conducted to investigate the degradation of aldicarb, an oxime carbamate insecticide, in sterile, non-sterile and plant-grown soils, and the capability of different plant species to accumulate the pesticide. The degradation of aldicarb in soil followed first-order kinetics. Half lives (t1/2) of aldicarb in sterile and non-sterile soil were 12.0 and 2.7 days, respectively, which indicated that microorganisms played an important part in the degradation of aldicarb in soil. Aldicarb disappeared more quickly (p< or =0.05) in the soil with the presence of plants, and t1/2 of the pesticide were 1.6, 1.4 and 1.7 days in the soil grown with corn, mung bean and cowpea, respectively. Comparison of plant-promoted degradation and plant uptake showed that the enhanced removal of aldicarb in plant-grown soil was mainly due to plant-promoted degradation in the rhizosphere.

Bioaccumulation of Butyltins via an Estuarine Food Chain

An estuarine food chain of threetrophic levels–algae (Platymonas sp.), rotifers (Brachionus plicatilis) and mysids (Neomysis awatschensis Brandt) was setup in laboratory in order to investigate contributionsof water and food to the accumulation of butyltins inupper trophic organisms, as well as to evaluate thelikelihood of biomagnification of butyltins throughthe aquatic food chain. Kinetics of bioaccumulationand depuration of butyltins through the food chainwere studied. Bioconcentration factors of butyltins inthe three organisms were high (103–104).Butyltin burdens in the upper trophic organisms atsteady-state of bioaccumulation by the ingestion oftainted food exceeded those observed by exposure towater only. For total butyltins, food chain transfernumber was 1.44 for algae to rotifers and 0.59 forrotifers to mysids, respectively. Biomagnification wasnot confirmed. It is concluded that whether or notbiomagnification occurs depends not only on theproperty of compounds but also on the organisms involved.

The sorption behavior of complex pollution system composed of aldicarb and surfactant—SDBS

The behavior of complex pollution system in soil composed of aldicarb, a carbamate pesticide, and sodium dodecylbenzenesulfonate (SDBS), an anionic surfactant, was studied by the experiment of shaking sorption balance. The range of concentration of aldicarb and SDBS was 0.4-5.0 and 1-1000 mg/kg of dried soil, respectively. Linear sorption isotherm was well fitted for these two chemicals. SDBS can decrease the sorption of aldicarb in soil remarkably. While the concentration of SDBS increased from 0 to 1000 mg/kg, the linear sorption coefficient can be decreased by 50%. But aldicarb showed no effect on the sorption of SDBS in experiment. In addition the mechanism of the effect of SDBS on sorption of aldicarb was discussed.

Photodegradation of nonylphenol polyethoxylates in aqueous solution

Two lamps, including simulated sunlight lamp and UVA-365 nm lamp, were used to study the kinetics and changes of component distribution of NPEOs mixture in solution during photodegradation, as well as the effect of H2O2 on the photodegradation. LC-MS was used to analyze the products of NPEOs photodegradation. It was found that photodegradation of NPEOs occurred under both simulated sunlight and UVA irradiation, with the degradation rate being 6.20 x 10(-3) micromol/(L x h) and 1.18 x 10(-2) micromol/(L x h), respectively. The component distribution of short chain NPEO(1,3) increased during the photodegradation process under simulated sunlight, while no obvious change was observed under UVA irradiation. The presence of the oxidant, H2O2, was found to be propitious to the photodegradation of NPEOs, especially under the irradiation of simulated sunlight. At different added concentrations of H2O2, the 96 h degradation percentage of NPEOs increased from 20.9% (non-H2O2) to 44.4% (0.01 mmol/L H2O2) and even 91.5% (1.00 mmol/L H2O2), respectively. The analysis for degradation products using LC-MS suggested that CA(3-9)PEC3 might he the major photodegradation products of NPEOs, based on which the reaction mechanism of NPEOs photodegradation was speculated.

Experimental Study on Effect of Anion Surfactant on Degradation Rate of Aldicarb in Soil

Degradation kinetics of aldicarb [2‐methyl‐2‐(methylthio) propionaldehyde O‐(methyl carbamoyl) oxime] in surface and subsurface soil containing different levels of sodium dodecylbenzenesulfonate (SDBS) were determined to understand complex effect of SDBS on aldicarb degradation process. The results showed that degradation curves of aldicarb in soil can be described with first order kinetics formula and the degradation rate constant, k (d− 1), in surface soil was larger than that in subsurface soil. SDBS can accelerate the degradation of aldicarb in soil and there was a good linear relationship between degradation rate constant and the logarithm of SDBS concentration. The possible reasons were that SDBS could change pH value of soil, have solubilization effect on aldicarb, and be used as carbon source of microorganisms. But SDBS had a larger promotion to the degradation of aldicarb in surface than in subsurface soil. When SDBS concentration was 1000 mg/kg of dried soil the first order degradation rate constant of aldicarb could be increased by 56.6 percent in surface soil and by 27.6 percent in subsurface soil, respectively.

The Leaching Behavior of Aldicar Among Complex Pollution System Composed of Surfactant SDBS and Aldicarb

The leaching behavior of aldicarb among the complex pollutionsystem composed of aldicarb and surfactant – sodiumdodecylbenzenesulfonate (SDBS) was studied by soil column.Distilled water was used to simulate rain in order to obtain therainfall of 235 mm for each time. Three simulations were carriedout successively to give 705 mm rainfall in all. The results ofmulti-step leaching experiment showed that compared with controlcolumn, SDBS can increase the vertical distance of aldicarbmoving and accelerate the leaching. As the concentration of SDBSincreased from 250 to 500 mg kg-1 of soil, not only theleaching depth of aldicarb increased by 20 cm, but also below10 cm depth in soil column the concentration of aldicarb at thesame depth increased obviously. This will enhance the danger ofgroundwater pollution. SDBS affected the leaching behaviour ofaldicarb in soil by influencing its water solubility, adsorptioncapacity and degradation process. The mechanism of this complexeffect has been discussed in this article.