Chao Tai

Determination of hydroxyl radicals photochemically generated in surface waters under sunlight by high performance liquid chromatography with fluorescence detection

Hydroxyl radicals can be generated in various kinds of surface water under sunlight, which has a great impact on the transformation and degradation of pollutants in water due to its high reactivity. In this investigation, we report a sensitive and simple method for the determination of hydroxyl radicals based on trapping the hydroxyl radicals with dimethyl sulfoxide to quantitatively produce formaldehyde, which then reacts with ammonium and acetylacetone. The product, 3,5-diacetyl-1,4-dihydro-2,6-lutidine, was analyzed by high performance liquid chromatography with a fluorescence detector. Factors affecting the derivatization reaction of formaldehyde and trapping reaction of hydroxyl radical, as well as the applicability of the method in the determination of hydroxyl radicals in typical surface waters under sunlight, were investigated. Under optimized conditions, the quantitative limit for the hydroxyl radicals was 0.067 μmol L−1, with a quantitative range of 0.067–13.4 μmol L−1 and a correlation coefficient of 0.9978. By the proposed method, the generation of hydroxyl radicals in lake water, sea water and wetland water under sunlight in the presence and absence of nitrates and nitrites was measured.

Efficient decolorization of typical azo dyes using low-frequency ultrasound in presence of carbonate and hydrogen peroxide

The aims of this study as to evaluate and understand the decolorization of azo dyes using carbonate and hydrogen peroxide under low-frequency ultrasonic irradiation. Under optimal conditions, the decolorization ratio of acid orange 8 (AO 8), a typical azo dye, was > 90% after 2 h of irradiation. The decolorization rate of AO 8 was 0.023 min-1 under ultrasonic irradiation, which was about two times that without ultrasound. Different from the results of other published studies, OH played a minor role, while CO3- played the most important role in AO 8 ultrasonic decolorization in the presence of CO32- and H2O2, with a contribution of 56.52%, followed by CO42- (32.61%) and 1O2 (10.87%). Another difference is that CO3- formed through the cleavage of peroxymonocarbonate or peroxydicarbonate under ultrasonic irradiation rather than through reaction between hydroxyl radical and carbonate. Investigations for different azo dyes revealed that the decolorization rate decreased in the order AO 8 ≈ orange II > acid red 9 > acid yellow 11, probably because of molecular differences among the azo dyes.

Level and Source of Polycyclic Aromatic Hydrocarbons in River Water and Runoff from Danjiangkou Reservoir Area, China

The Haoping river, a second grade tributary of Danjiangkou reservoir, was selected as the studying region. To find out the polycyclic aromatic hydrocarbons (PAH) pollution level, the distribution of PAH in river water and runoff, the perhaps PAH pollution source, the artificial runoff pools were built, the samples of river water and runoff were collected and the levels and distribution of polycyclic aromatic hydrocarbons in the samples above were studied. It was found that: i) the PAHs content in the level water period (April) is higher than that in low water period (June) and abundant period (Sept.); ii) the runoff volume and the total PAHs content in runoff increase with the land slope; iii) the main source of PAHs from river water and runoff was combustion sources, such as coal and timber, and only a litter from the leak of petroleum products.

Degradation of 2,4,6-Trichlorophenol by Hydrogen Peroxide Catalyzed by Nano-Iron

In this paper, the degradation of 2,4,6-trichlorophenol (TCP) by hydrogen peroxide catalyzed by nano-iron was studied. Nano-iron was obtained through chemical reduction of FeSO4•7H2O and KBH4. The influences of pH, the concentration of H2O2, temperature, ionic strength and the amount of nano-iron on the degradation of TCP were investigated. The result showed that under the optimized condition, more than 95 percent of the TCP can be degraded in 60 min. Initial pH was proved to have significant effect on the degradation and lower pH brought faster degradation rate. When initial pH was 3, the effect was the best.

A New Method of Determinated Organochlorine Pesticides in the Surface Water

In this paper, an apparatus of inert gases-surfactants assistant liquid-liquid extraction(ISALLE) is described. Based on this apparatus, a method for the determination of 20 trace level organochlorine pesticides in the water was developed. The influence of various experiment conditions on the extraction efficiency of ISALLE for the organochlorine pesticides was studied. The linearity in the detecting range is good (R≫0.99) with the detection limits of 0.4-2 ng/L¿and the quantification limits of 4-8 ng/L¿The RSDs were lower than 6.7¿ and the recoveries were 83%-121%. The method had been used to determine the organochlorine pesticides in the surface water with satisfactory results.

Determination of Organic Chlorinated Pesticides in the Surface Water by Continuous Flow Solid-Phase Microextraction Combined with Gas Chromatography Method

In this paper, an apparatus of continuous flow solid-phase microextraction is described. Based on this apparatus, a method for the determination of 20 trace level organic chlorinated pesticides in the water was developed. The influence of various experiment conditions on the extraction efficiency of continuous flow solid phase microextraction for the organic chlorinated pesticides was studied. The linearity in the detecting range is good (R>0. 991) with the detection limits of 0.01-0.5 mugL-1, and the quantification limits of 0.02-1 mug/L. The RSDs were lower than 1% and the recoveries were 86%-118%. The method had been used to determine the organic chlorinated pesticides in the surface water with satisfactory results.

Levels and Distribution of Organic Chlorinated Pesticides in Water and Sediment from Mengjin Part of Yellow River Wetland, China

Mengjin wetland, located in the northeast of Mengjin county, with an area of 11700 hectares, is an important part of the Yellow River wetland which has been recognized to be a national conservation area. In the present study, the distribution characteristics of organochlorine pesticides (OCPs) in the surface water and sediments from the Mengjin wetland were studied. The concentration of organochlorine pesticides in the surface water and from the Mengjin wetland was analyzed by gas chromatography. The results show that 1) HCHs and DDTs are the dominating components of OCPs in both water and sediment samples. 2) In the water samples of Mengjin wetland, the OCPs content in the level water period is higher than that in low water period and abundant period. The HCHs are the dominating components. 3) In the sediment samples of Mengjin wetland, the OCPs content in the level water period is higher than that in low water period and abundant period. The DDTs are the dominating components.