In six aircraft flights of AGASP-II, 2-15 April 1986, from ca. 1300-8100 m altitude, the most abundant elements measured in size separated aerosol samples were silicon, chlorine, and sulfur. Concentrations were higher than at ground level (G), particularly at highest altitudes (HT, 5600-8100 m, upper troposphere to lower stratosphere) compared to mid troposphere (MT, 1300-4700m), especially for ultrafine particles <0.0625 mu m aerodynamic diameter. HT and MT median and G average concentrations, mu g m(-3) STP, respectively (1) Si = 3.64, 1.30, 0.092; (2) S = 1.44, 0.265, 0.087; (3) Cl=1.62, 0.36, 0.213. The weight ratio Al/Si was less than half that expected for Earth crust material (0.3), evidence against fine silicon originating mainly by dispersion of volcanic debris or other eolian dust particles. Instead, pollution from high rank (mainly bituminous) coal combustion, which can form SiO vapors from quartz in the ash and fine alkaline aerosol with low Al/Si ratio, is a more likely source of apparently widespread aerosol silicon contamination of the Arctic atmosphere. Chlorine and sulfur gases may be scavenged by coarse alkaline dust particles and acidic chlorine and sulfur may be derived from coal combustion processes, thus also accounting for their high concentrations.
<正> For solving the map-coloring problems,this paper presents an energy function,amore effective dynamic equation and a more simple convergence condition.For the first time westudy the map-coloring problems in the way of connecting discrete Hopfield neural network withthe orthogonal optimization,and as a practical example,a color map of China is given.
Surface ozone, particulate bromine and inorganic and organic gaseous bromine species were measured at Barrow, AK, during March and April 1989 to examine the causes of surface ozone destruction during the arctic spring. Satellite images of the Alaskan Arctic taken during the same period were also studied in conjunction with calculated air mass trajectories to Barrow to investigate the possible origins of the ozone-depleted air. It was found that during major ozone depletion events (O-3 < 25 ppbv) concentrations of particulate bromine and the organic brominated gases bromoform and dibromochloromethane were elevated. Air mass trajectories indicated that the air had crossed areas of the Arctic Ocean where leads had been observed by satellite. The transport time from the leads was typically a day or less, suggesting a fast loss mechanism for ozone. A similarly fast production of particulate bromine was shown by irradiating ambient nighttime air in a chamber with actinic radiation that approximated daylight conditions. Such rapid reactions are not in keeping with gas-phase photolysis of bromoform, but further studies showed evidence for a substantial fraction of organic bromine in the particulate phase; thus heterogeneous reactions may be important in ozone destruction.
Interpretation of simultaneous measurements at three stations in different parts of the Arctic suggests that during winter air masses are forced into the Arctic from Eurasia in a surge towards Alaska and further return over the North Pole towards the European Arctic. On some occasions direct flow of the Eurasian air masses was detected in the European Arctic. Simple statistical methods and dispersion modelling proved useful in studying source-receptor relationships in the Arctic.