Total suspended particulate （TSP） samples were collected at three sites along the coast of Qingdao, China, before and during a major dust storm in March, 2002. For comparison, PM10（particulate matter with aerodynam...Total suspended particulate （TSP） samples were collected at three sites along the coast of Qingdao, China, before and during a major dust storm in March, 2002. For comparison, PM10（particulate matter with aerodynamic diameters less than 10μm） samples were collected at one of the three sites. The morphological observation and compositional analysis of bulk and individual particles were performed by using scanning electron microscopy equipped with an energy dispersive X-ray system （SEM/EDX） for the TSP and PM10 samples. The results showed that the particles of different kinds of morphology had different elemental compositions, but the particles of similar morphology did not always have the same elemental composition for non-dust samples. The morphology and composition of non-dust particles were different at different sites. The fractal and spherical particles existed mainly in the coarse fraction for non-dust samples, while in the fine mode （〈 10μm） there were floccules formed by fine particles flocking together and containing crustal elements. Compared with the non-dust particles, the dust particles were more homogeneous in terms of morphology, particle size and composition. Particles with irregular shapes and well-distributed sizes dominated in the dust samples, containing crustal elements such as Mg, A1, Si, Ca, Fe, etc. The high sulfur content indicated that homogeneous and heterogeneous reactions took place on the surfaces of the dust particles in the specific environment of Qingdao.展开更多
Contamination of the environment by pesticides is the inevitable aftermath of plant protection, and a substantial portion of pesticide pollutants exists in the form of aerosol particles levitated in the air and deposi...Contamination of the environment by pesticides is the inevitable aftermath of plant protection, and a substantial portion of pesticide pollutants exists in the form of aerosol particles levitated in the air and deposited on plants, and as the pesticide residues （thin films） on the surface of plant leaves. The sunlight photolysis could be the resource for the accelerated photochemical decomposition of pesticide compounds to minimize the long-term environmental contamination. The rates of photochemical decomposition of pesticide chemicals propiconazole （commercial formulation Tilt） and haloxyfop-ethoxyethyl （Zellek） were measured in particles of 0.12-1.3 μm in diameter and in films 0.04-0.2 μm thick. A specific polyaromatic sensitizer Shirvanol was used to induce accelerated decomposition of the above pesticide particulates under both the solar radiation and the artificial UV light. It was established that propiconazole decomposes by the sensitized photo-oxidation only, but haloxyfop-ethoxyethyl reacts in both the oxygen （air） and oxygen-free mediums via both the direct and sensitized reactions. The photochemical mechanisms are hypothesized and argued for the oxidative and non-oxidative decompositions. The haloxyfop-ethoxyethyl （Zellek） residues lbrmed on foliage upon pesticide treatments of agricultural fields would essentially decompose under sunlight via a direct photoreaction in 4-6 weeks, but the propiconazole （Tilt） contaminants probably need more time.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.49976020).
文摘Total suspended particulate （TSP） samples were collected at three sites along the coast of Qingdao, China, before and during a major dust storm in March, 2002. For comparison, PM10（particulate matter with aerodynamic diameters less than 10μm） samples were collected at one of the three sites. The morphological observation and compositional analysis of bulk and individual particles were performed by using scanning electron microscopy equipped with an energy dispersive X-ray system （SEM/EDX） for the TSP and PM10 samples. The results showed that the particles of different kinds of morphology had different elemental compositions, but the particles of similar morphology did not always have the same elemental composition for non-dust samples. The morphology and composition of non-dust particles were different at different sites. The fractal and spherical particles existed mainly in the coarse fraction for non-dust samples, while in the fine mode （〈 10μm） there were floccules formed by fine particles flocking together and containing crustal elements. Compared with the non-dust particles, the dust particles were more homogeneous in terms of morphology, particle size and composition. Particles with irregular shapes and well-distributed sizes dominated in the dust samples, containing crustal elements such as Mg, A1, Si, Ca, Fe, etc. The high sulfur content indicated that homogeneous and heterogeneous reactions took place on the surfaces of the dust particles in the specific environment of Qingdao.
文摘Contamination of the environment by pesticides is the inevitable aftermath of plant protection, and a substantial portion of pesticide pollutants exists in the form of aerosol particles levitated in the air and deposited on plants, and as the pesticide residues （thin films） on the surface of plant leaves. The sunlight photolysis could be the resource for the accelerated photochemical decomposition of pesticide compounds to minimize the long-term environmental contamination. The rates of photochemical decomposition of pesticide chemicals propiconazole （commercial formulation Tilt） and haloxyfop-ethoxyethyl （Zellek） were measured in particles of 0.12-1.3 μm in diameter and in films 0.04-0.2 μm thick. A specific polyaromatic sensitizer Shirvanol was used to induce accelerated decomposition of the above pesticide particulates under both the solar radiation and the artificial UV light. It was established that propiconazole decomposes by the sensitized photo-oxidation only, but haloxyfop-ethoxyethyl reacts in both the oxygen （air） and oxygen-free mediums via both the direct and sensitized reactions. The photochemical mechanisms are hypothesized and argued for the oxidative and non-oxidative decompositions. The haloxyfop-ethoxyethyl （Zellek） residues lbrmed on foliage upon pesticide treatments of agricultural fields would essentially decompose under sunlight via a direct photoreaction in 4-6 weeks, but the propiconazole （Tilt） contaminants probably need more time.
