[Temporal and Spatial Distribution Characteristics of PM2.5 in Chongqing Urban Areas].

To explore the diurnal and seasonal characteristics of PM25, hourly PM25 concentration data ol It tixed monitoring sites in Chongqing urban area were collected continuously from June 2014 to May 2015. The result showed that: (1) the seasonal concentration of PM2.5 in different seasons decreased in the order of winter, autumn, spring and summer (P < 0.05), which were 100.2 microg x m(-3), 66.1 microg x m(-3), 45.9 microg x m(-3) and 33.4 microg x m(-3), respectively. (2) Monthly average concentrations of PM2.5 showed a single-peak curve, and the peaks of which occurred in January (P < 0.05, 120.8 microg x m(-3)). (3) For the whole year, daily variation of PM2.5 showed a jaggies curve. (4) Diurnal average concentrations of PM2.5 showed an obviously bimodal curve in winter, autumn and spring, hut it was less obvious in summer. (5) Daily PM25 concentration was significantly positively correlated with SO2, NO2 and CO (P < 0.01), indicating that the concentrations of SO2, NO2 and CO had a significant impact on the concentration of

[Determination of Total Selenium and Arsenic in Coal by Wet Digestion Hydride Generation Atomic Fluorescence Spectrometry (HG-AFS)].

In the present work we presented a new method for determination of total Se and As in coal by electric hot plate-mixed acids-hydride generation atomic fluorescence spectrometry (HG-AFS), the wet digestion method. The detailed operation procedures of the new method are as follows: About 0. 05~0. 10 g of powdered (200 mesh) coal sample was placed in a glass beaker, 10 mL of nitric acid (HNO3) and 2 mL of perchloric acid (HClO4) were added to the beaker in sequence, then the beaker was covered with a watching glass and placed in a fume cupboard standing overnight. The beaker was placed on an electric hot plate (180 °C) for sample decomposition the next day. The beaker was moved away from the electric hot plate when white smoke arose in the beaker, the sample color turned white or grey and the solution turned clear. Three milliliter of hydrochloric acid (HCl) solution (6 mol . L-1) was added to the beaker after the temperature of the beaker returned to room temperature. The beaker was heated on the electric hot plate again, and then moved away when white smoke started arising again. One milliliter of HCI was added in the beaker after the temperature of the beaker returned to room temperature. After that, the digested sample was transferred to a 25 mL test tube which was filled with ultrapure water to the tube's full volume. This solution was used for Se determination directly. Three milliliter of the Se test solution prepared above was transferred to a 15 mL glass test tube, 1 mL of thiourea/ascorbic acid solution (2. 5 g . mL-1) and 1 mL of the concentrated HCl was added to the 15 mL test tube. The test tube was then filled with ultrapure water to its full volume. The solution was used for As determination after shaking well and 40 min standing. Finally, Se and As concentrations in these prepared solutions were measured by using the AFS-9780 instrument (Beijing Haiguang Instrument Co. , LTD, Beijing, China). Two Chinese Coal Certified Reference Materials (GBW11115 and GBW11117) were tested using this method, and the recoveries of As were 99. 7%~100. 3% and the relative standard deviation (RSD) for As and Se were 5. 6%~6. 0% and 11. 1%~13. 5%, respectively. The limits of detection (LOD) of the method for Se and As determination were 0. 01 and 0. 05 µg . L-1, respectively. These results indicated that this new method was suitable for Se and As determination in coal, and it had the advantages of simple operation, high accuracy and reproducibility compared with the Chinese National Standard method.

The daily fluorine and arsenic intake for residents with different dietaries and fluorosis risk in coal-burning fluorosis area, Yunnan, Southwest China.

The daily fluorine (F)/arsenic (As) intake (DFI/DAsI) for residents at different ages with different dietaries and dietary changes was investigated to analyze the fluorosis risk in coal-burning fluorosis area in Yunnan, Southwest China. The DFI for residents with a dietary of roasted corn and roasted chili was 5.06, 9.60, and 14.38 mg for age groups 3-7, 8-15, and over 15 years, respectively. Over 90 % of DFI was from roasted foodstuffs. The DFI for residents of the same age group living on rice and roasted chili was 1.94, 3.50, and 4.95 mg, respectively, which were less than that for the former dietary type, and 65 % of DFI was from roasted chili. The main sources for their DFI are roasted foodstuffs. Both were higher than the dietaries with non-roasted foodstuffs and the recommended daily allowances (RDAs) for USA and China at different levels. The DAsI for all residents ranged from 25 to 135 µg, and at this level of DAsI, it would not influence human health. However, As pollution of roasted foodstuffs might have an important influence for the fluorosis. Residents are changing their staple food from roasted corn to rice, and especially, younger people are more focused on quality life. However, even if residents change their staple food, the habit of eating chili will not change, which also may cause them getting fluorosis. Developing economy, changing dietary types, and changing the habit of drying and keeping chili will help to reduce the fluorosis risk in coal-burning fluorosis area of Southwest China.

Regional distribution of longevity population and chemical characteristics of natural water in Xinjiang, China.

Xinjiang Province, China is recognized for the longevity of its inhabitants. To study the temporal and spatial variation of longevity region and chemical characteristics of natural water of longevity region in Xinjiang, three population censuses on county-level and 51 natural water samples from Hotan Prefecture, Xinjiang were collected and analyzed. 103 natural water samples were collected from the public papers. Population statistics on county-level showed that the number of centenarians per 100,000 inhabitants (OC) in Southern Xinjiang was 7.4(year 1990), 4.9(year 2000) and 2.1 times (year 2010) more than that of Northern Xinjiang, respectively. And distribution of the longevity index (LI%), centenarity index (CI%) and number of centenarians per 10,000 over 65 year-old subjects (UC) on county-level decreased from south to north. Natural water in Northern Xinjiang was mainly fresh soft water, and it was mainly fresh hard water and brackish hard water in Southern Xinjiang. Water quality of natural water in Northern Xinjiang was superior compare to that of Southern Xinjiang, while number of centenarians 65 year-old & over per 10,000 subjects in Northern Xinjiang were less than that of Southern Xinjiang before 2010. The research indicates that keeping on drinking water with high total hardness (TH) and Mg/Ca ratio might be good for the health.

The pollution control of fluorine and arsenic in roasted corn in "coal-burning" fluorosis area Yunnan, China.

Pilot experiments were carried out to reduce the fluorine (F) and arsenic (As) pollution of roasted corn dried by open ovens in "coal-burning" fluorosis area Yunnan, China. The results indicated that the average emission amount of F and As in briquettes in experimental group were 29.20mg/kg and 0.76 mg/kg in Xiaolongdong, and 46.8 mg/kg and 0.54 mg/kg in Mangbu respectively. The results also indicated that the fixing rate of F and As in briquettes in experimental group was more than 4 times and 1.2 times of that in control group respectively. The average concentration of F and As in roasted corn in experimental group were 3.86 mg/kg and 13.23 µg/kg in Xiaolongdong, and 4.77 mg/kg and 122.96 µg/kg in Mangbu respectively, which reduced by more than 65% and 75% respectively compared with that in control group. Adding local natural calcium-based materials in briquettes can reduce the emission of F and As and their pollution on roasted corn largely, and thus will reduce the risk of fluorosis for residents greatly in "coal-burning" fluorosis area of southwestern China.

[Determination of total selenium in water by hydride generation atomic fluorescence spectrometry].

In order to establish a rapid and accurate hydride generation-atomic fluorescence spectrometry method for the determination of selenium content in water samples, the influence factors on Se nitrolysis in the water such as nitrolysis temperature and the amount of hydrochloric acid were studied. The authors determined a simple and practical test method that is to add 3 mL hydrochloric acid at 3 degrees C. We measured the precision and accuracy of the method by the standard liquid of 3, 6 and 10 micro x L(-1), and the test results were 2.96, 5.43 and 9.66 mg x L(-1). The recovery varied from 90.50% to 98.67%. Meanwhile we tested 29 water samples by different methods. The error of standard sample was 8.95%-25.46% by hydride generation-atomic fluoresence spectrometry in the GB/T 5750. 6-2006, and the error of standard sample was 1.33%-3.40% by new method. Compared with the national standards of GB/T 5750.6-2006, the method has the advantages of operating simplicity and and easy control, and it is also reliable and economical.

Coal-burning roasted corn and chili as the cause of dental fluorosis for children in southwestern China.

To find the pathologic cause of the children's dental fluorosis in southwestern China, diet structure before the age of 6 and prevalence rate of dental fluorosis (DF) of 405 children were investigated, and the fluorine and arsenic content of several materials were determined. The prevalence rate of DF of children living on roasted corn before the age of 6 is 100% with nearly 95% having the mild to severe DF; while that of children living on non-roasted corn or rice is less than 5% with all having very mild DF. The average fluorine and arsenic concentration are 20.26 mg/kg and 0.249 mg/kg in roasted corn, which are about 16 times and 35 times more than in non-roasted corn, respectively. The average fluorine concentration is 78 mg/kg in coal, 1116 mg/kg in binder clay and 313 mg/kg in briquette (coal mixed with clay). The average arsenic concentration of coal is 5.83 mg/kg, the binder clay is 20.94 mg/kg, with 8.52 mg/kg in the briquette. Living on roasted corn and chili is the main pathologic cause of endemic fluorosis in southwestern China. The main source of fluorine and arsenic pollution of roasted corn and chill is the briquette of coal and binder clay.

[Sequential extraction experiments applied to study chemical mobility of fluorine in rocks].

Sequential extraction experiments were used to study the chemical mobility of fluorine in rocks. The results show that there are quite big differences in chemical mobility of fluorine in rocks of different types. Fluorine in carbonate rock is very active, in which the proportion of leachable fluorine is generally more than 75%. Fluorine in black rocks of Lower Cambrian is closely related to their different metamorphosed grades, in which fluorine in black carbonaceous slate with higher metamorphosed grade mostly has lower leachability than black shale and black siliceous rock. Generally speaking, the leachable percentage of fluorine is high in phosphorite rocks and low in phyllite. The leachable fluorine in diabase is in direct proportion to its fluorine concentration. There are some differences in chemical mobility of fluorine in stone coal of different ages. Fluorine in stone coal of Silurian has higher leachability than stone coal of Cambrian.

[Pilot experiment of fluorine fixing ratio of coated lump stone coal fuel].

The pilot experiment on coated lump stone coal fuel selected from 16 families in Haoping Shanxi were studied. 8 families burned coating high fluorine lump stone coal with lime, clay and low fluorine anthracite, 8 families burned untreated lump stone coal. The results show that the fluorine-fixing ratio at treated group was 75.0% when coal fluorine compared with coal cinder fluorine. In comparison with untreated group, the concentration of door air fluoride lowered 85.7%, SO2 lowered 75.0%, dust lowered 55.3%.

[Regularity of flourine release from fluorine-rich coal combustion in the fluorine poisoning area].

Laboratory experiments and in situ measurements inside farmer's houses indicate that the fluorine concentration of indoor air was positively related with the fluorine content in the consumed coal (R = 0.612, P<0.01), but fluorine content in the coal had no effect on the release rate of coal fluorine under the usual combustion temperature of about 1000 degrees C. The release rate of coal fluorine varied versus combustion temperature ranging from 200 to 1200 degrees C, following a "S" curve pattern, increasing slowly under 300 to 700 degrees C, but quickly under 700 to 1000 degrees C, and then slowly again before finally reaching 100% under 1100 to 1200 degrees C, this curve can be fit by Logistic equation. The release rate of coal fluorine usually depends upon the existence status of fluorine and the chemical and mineral components of the coal. The fluorine in soft coal or anthracite from Guizhou is released more quickly than in bone coal from Southern Shanxi, with the former almost completely released under 1100 degrees C but the later almost completely released under 1200 degrees C. The combustion temperature of civil stoves is at most 1000 degrees C, under which averagely 86.9% of the fluorine in coal from Guizhou and 80.6% of that in bone coal from Southern Shanxi is released.