[Case study on groundwater health risk assessment and remediation strategy based on exposure pathway].

The carcinogenic risk originated from benzene in contaminated groundwater of a large-scale coke plant in Beijing was analyzed and assessed for different land use zones according to the site redevelopment plan. The results revealed that indoor vapor inhalation was the key exposure pathway for all the three zones. The carcinogenic risk in zone A as commercial area was 6.37 x 10(-8), below the maximum allowable level (1.0 x 10(-6)), but was 2.20 x 10(-4) in zone B as industrial park and 7.49 x 10(-5) in zone C as residential/commercial area, both beyond the acceptable level. Further, the remediation target for benzene was calculated at 118 microg x L(-1) and the corresponding remediation area was contoured to be 165 000 m2. Given the high permeability of the aquifer and the excellent volatility of benzene, air-sparging with a combination of engineering control measure was recommended to mitigate the risk of the groundwater contamination.

[Resistance of Anopheles sinensis to insecticides in Huaibin County of Henan Province].

Anopheles sinensis adults were captured from Huaibin County and raised in laboratory. Larvae dipping method and the WHO tubes were used to determine the resistance of F1 IV-stage larvae and 3-5 day-old adult mosquitoes to dimethyl dichlorovinyl phosphate (DDVP), deltamethrin, and arprocarb. The activity of acetylcholine esterase (AChE) of larvae and adult mosquitoes was measured by colorimetric method before and after the respective addition of the 3 insecticides. The results showed that the mortality of adult mosquitoes in 0.05% deltamethrin testing tube (0.017 8 g/m2) was 51.2%, which was less than 80% and judged as resistant group. The LC50 of larvae to DDVP, deltamethrin, and arprocarb were 2.76, 320.85, 754.32 mg/L, respectively. The inhibition rates of 0.005 mmol/L DDVP, deltamethrin, and arprocarb to AChE activity were 77.8%, 62.8%, and 58.9% in larvae, while 76.1%, 62.2%, and 58.22% in adults, respectively, showing a significant inhibition on the AChE activity of An. sinensis (P < 0.01).

[Effect of acidity on the interaction of Ofloxacin and bovine serum albumin].

Bovine serum albumin (BSA) exists as N(pH -7.0), B(pH -9.0), and E (pH < 3.5) = isomeric forms in the solution of different pH. Acid effect on the structure of bovine serum albumin and the interaction of different structure of BSA with Ofloxacin were studied by UV-Vis and fluorescence spectroscopy. Based on the fluorescence quenching of bovine serum albumin and Förster energy transfer mechanism, the quenching constants, energy transfer efficiencies and the binding distances were determined at four different pHs. The results showed that Ofloxacin has the ability to quench bovine serum albumin fluorescence with the optimal condition of fluorescence quenching constants of 1.928 1 x 10(5) L x mo l(-1), binding distance of r = 2.55 nm and quenching efficiency of 8.63 x 10(4) L x mo x l(-1) at pH 4.9. Non-radiative energy transfer and static quenching were the cause of fluorescence quenching. The influence on the binding of Ofloxacin and bovine serum albumin under neutral, subacidity and alkalescent conditions was not obviously observed, and the electrostatic interaction was not the main force. The effect of Oflx on the conformation of BSA was also investigated using synchronous fluorescence spectrometry.