排序方式: 共有33条查询结果,搜索用时 15 毫秒
21.
Sri Lanka provides an ideal opportunity for the study of the effect of geology on human health. The vast majority of the people
of Sri Lanka still live in rural areas within areas termed geochemical provinces. Very broadly, one could say that a geochemical
province has characteristic chemical composition in soil, water stream sediments and rocks, enabling their delineation from
others. The chemical composition is presumed to be have an impact on the health of the inhabitants of the particular geochemical
province, particularly because of the fact that their food and water are obtained mostly from the terrain itself. This leads
to the concept of “diseases of geochemical origin”. Among these are dental fluorosis, iodine deficiency disorders (IDDs) and
selenium-based diseases. The Dry Zone of Sri Lanka has several areas rich in groundwater fluoride, the ingestion of which
leads to dental fluorosis. Iodine deficiency diseases are more common in the Wet Zone, though their aetiologies are more complicated.
Interestingly, it has also been observed that significant proportions of the female population of Sri Lanka are selenium-deficient,
which could well be related to the geological environment. Chronic renal failure (CRF) has been observed in some areas of
the Dry Zone of Sri Lanka, where there is a relationship of CRF with the mineral content of drinking water. This subject matter
falls under the auspices of Medical Geology, a scientific discipline still in its infancy, and much more concerted studies
are needed to attract the attention of medical research. 相似文献
22.
23.
Hansen V Roos P Aldahan A Hou X Possnert G 《Journal of environmental radioactivity》2011,102(12):1096-1104
Natural organic matter, such as humic and fulvic acids and humin, plays a key role in determining the fate and mobility of radioiodine in soil and sediments. The radioisotope 129I is continuously produced and released from nuclear fuel reprocessing plants, and as a biophilic element, its environmental mobility is strongly linked to organic matter.Due to its long half-life (15.7 million years), 129I builds up in the environment and can be traced since the beginning of the nuclear era in reservoirs such as soils and marine sediments. Nevertheless, partition of the isotope between the different types of organic matter in soil and sediment is rarely explored. Here we present a sequential extraction of 129I and 127I chemical forms encountered in a Danish soil, a soil reference material (IAEA-375), an anoxic marine sediment from Southern Norway and an oxic sediment from the Barents Sea. The different forms of iodine are related to water soluble, exchangeable, carbonates, oxides as well as iodine bound to humic acid, fulvic acid and to humin and minerals. This is the first study to identify 129I in humic and fulvic acid and humin. The results show that 30-56% of the total 127I and 42-60% of the total 129I are associated with organic matter in soil and sediment samples. At a soil/sediment pH below 5.0-5.5, 127I and 129I in the organic fraction associate primarily with the humic acid while at soil/sediment pH > 6 129I was mostly found to be bound to fulvic acid. Anoxic conditions seem to increase the mobility and availability of iodine compared to oxic, while subaerial conditions (soils) reduces the availability of water soluble fraction compared to subaqueous (marine) conditions. 相似文献
24.
25.
Preparation of iodine doped titanium dioxide to photodegrade aqueous bisphenol A under visible light
Highly photoactive iodine-doped titanium dioxide (I-doped TiO2) photocatalysts were synthesized to degrade aqueous bisphenol A (BPA) under irradiation by visible light and sunlight. The band gap energies of TiO2 and I-doped TiO2 (I/Ti mole ratio = 0.5%) were 3.01 and 3.04, and the BPA photodegradation rate constants were 1.61, and 5.11 h−1, respectively. The most probable reaction mechanism was proposed to involve IO4− and IO3− as electron acceptors that generate an inductive effect, increasing the photocatalytic efficiency of TiO2. Results indicated that I-doped TiO2 not only acted favorably as a photocatalyst, but also exhibited considerable mineralization effects. In addition, a recycling test after ten experiments demonstrated the stability and reusability of the photocatalyst. 相似文献
26.
Marine aerosols play an important role in the global aerosol system. In polluted coastal regions, ultra-fine particles have been recognized to be related to iodine-containing species and is more serious due to the impact of atmospheric pollutants. Many previous studies have identified iodine pentoxide (I2O5, IP) to be the key species in new particles formation (NPF) in marine regions, but the role of IP in the polluted coastal atmosphere is far to be fully understood. Considering the high humidity and concentrations of pollutants in the polluted coastal regions, the gas-phase hydration of IP catalyzed by sulfuric acid (SA), nitric acid (NA), dimethylamine (DMA), and ammonia (A) have been investigated at DLPNO-CCSD(T)//ωB97X-D/aug-cc-pVTZ + aug-cc-pVTZ-PP with ECP28MDF (for iodine) level of theory. The results show that the hydration of IP involves a significant energy barrier of 22.33 kcal/mol, while the pollutants SA, NA, DMA, and A all could catalyze the hydration of IP. Especially, with SA and DMA as catalysts, the hydration reactions of IP present extremely low barriers and high rate constants. It is suggested that IP is unstable under the catalysis of SA and DMA to generate iodic acid, which is the key component in NPF in marine regions. Thus, the catalytic hydration of IP is very likely to trigger the formation of iodine-containing particles. Our research provides a clear picture of the catalytic hydration of IP as well as theoretical guidance for NPF in the polluted coastal atmosphere. 相似文献
27.
在柠檬酸介质中,I-对KIO3氧化结晶紫的反应有催化效应,据此建立了测定微量I-新的催化动力学光度法.方法的检出限为0.185μg/ml,测定范围为5~70μg/25ml,用本法对环境水样进行了测定,结果满意。 相似文献
28.
本文研究结果表明,在自然环境缺碘地区持续投放含碘浓度25ppm 的“NaCLI—固”后出生的儿童身高体重发育水平接近对照地区的中等水平;缺碘地区儿童甲状腺激素 T_4、T_3、T_4/T_3比值均在正常范围,甲状腺功能状态基本正常,提示机体内环境缺碘程度已得到纠正;缺碘区儿童 IQ 低下检出率明显高于对照区,血清 Zn 水平则无显著性差异,表明这部分低智儿童与在胚胎期间碘元素相对缺乏有着密切关系. 相似文献
29.
利用碘消除碱性和中性溶液中硫化物及硫代硫酸盐对 Cr+ 6 测定的干扰 ,经实验找出了含硫化物和硫代硫酸盐工业废水中 Cr+ 6的测定方法 相似文献
30.
This paper deals with some endemic diseases related to selenium, iodine and fluoride in eco-environment. Keshan disease and Kaschin-Beck disease are associated with low selenium, they mainly occur in a belt zone across China ranging from North-East to South-West. Selenium contents in food grains and human hair from the disease affected areas are usually below 0.020ppm and 0.20ppm respectively. The endemic goitre caused by iodine deficiency distributes extensively in China, mainly in mountainous and hilly districts, swamp and peat areas, some sand soil and limestone areas. Also there is another kind of endemic goitre which caused by iodine excess in interior and coast areas. Endemic cretinism usually occurs in the endemic goitre seriously affected areas. Endemic fluorosis is also widely distributed in China, but mainly occurs in dry or semi-dry areas of north China. The fluoride sources for causing endemic fluorisis are drinking water and food grains polluted by coal smoke in the backing process of maize 相似文献