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Amethodforcalculatingthetotalozoneamountintheclearskies¥BaiJianhui;WangGengchen(InstituteofAtmosphericPhysics,ChineseAcademyo... 相似文献
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为分析抚河南昌段流域水体中重金属空间分布特征及可能来源,2019年08月在抚河南昌段共采集了23个地表水样及8个地下水样,对水体中的重金属V、Mn、Ba、Fe、Sr、Zn及类金属元素As进行了测定.结果表明,水体中不同重金属空间分布特征总体趋势一致,即中下游地区高于上游地区,污染特征空间差异性为中等及以上.地表水中V、Fe、Mn的平均浓度超过《地表水环境质量标准》(GB3838-2002)集中式生活饮用水特定项目标准限值;地下水中类金属元素As平均浓度超过《地下水质量标准》(GBT14848-2017)Ⅲ类水质标准.多元统计分析表明Sr、Ba、Mn可能主要来源于人类生产、生活污染物的排放,Fe、V、Zn可能主要来源于农业渔业及交通污染,类金属元素As主要来源于沿岸及河流底部淤泥及岩石碎屑. 相似文献
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Molecular weight(Mw) is a fundamental property of humic acids(HAs), which considerably affect the mobility and speciation of heavy metals in the environment. In this study, soil humic acid(HA) extracted from Jinyun Mountain, Chongqing was ultra-filtered into four fractions according to the molecular weight, and their properties were characterized.Complexation of cadmium was investigated by titration experiments. For the first time,Langmuir and non-ideal competitive adsorption-Donna(NICA-Donnan) models combined with fluorescence excitation-emission matrix(EEM) quenching were employed to elucidate the binding characteristics of individual Mw fractions of HA. The results showed that the concentration of acidic functional groups decreased with increasing Mw, especially the phenolic groups. The humification degree and aliphaticity increased with increasing Mw as indicated by elemental composition analysis and FT-IR spectra. The binding capacity of Cd~(2+) to Mw fractions of HA followed the order UF1( 5 kDa) UF2(5–10 kDa) UF4( 30 kDa) UF3(10–30 kDa). Moreover, the distribution of cadmium speciation indicated that the phenolic groups were responsible for the variations in binding of Cd~(2+) among different Mw fractions. The results of fluorescence quenching illustrated that the binding capacity of Cd~(2+) to Mw fractions was controlled by the content of functional groups, while the binding affinity was largely influenced by structural factors. The results provide a better understanding of the roles that different HA Mw fractions play in heavy metal binding,which has important implications in the control of heavy metal migration and bio-toxicity. 相似文献
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核电厂厂址保护范围与要求探讨 总被引:1,自引:0,他引:1
核电厂厂址选择需要综合考虑各种自然和人为因素,一种宝贵的稀缺资源,考虑核电的长远规划,为防止由于人为因素使核电厂厂址及其周围环境条件遭到破坏,有必要采取有效的措施对核电厂厂址实施保护。核电厂厂址保护内容主要涉及核电厂安全、事故应急条件以及环境相容性等方面,保护范围可分为拟征地范围和非居住区、规划限制区、外围地带等,其中拟征地范围和非居住区是厂址保护中最为核心的区域,应当予以重点保护。通过对相关的保护范围和要求展开探讨,以期对今后核电厂厂址确定相关保护范围和要求具有一定的参考意义。 相似文献
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China's policy on structural adjustment of its agriculture is an effective instrument for increasing agricultural production and developing the rural economy. The policy interventions used included converting cultivated land from growing grain crops to cash crops and increasing the production of meat, eggs and milk. The impacts of these changes on grain supply between 1998 and 2004 are identified and quantified at national and regional levels. The data on cultivated land diverted to other purposes are presented for the benefit of the decision maker. The paper concludes that the policy had significant impacts on China's grain supply, which declined by 14.4% of the total grain output in 1998. However, nearly 40% of the cultivated land at national level could potentially be converted by 2010. Regional disparities in the extent of the reduction in grain supply and in land conversion are highlighted with reference to different economic conditions and policy directions. 相似文献
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Rural-urban land conversion is a universal phenomenon in the rapid process of economic development and urban growth. The welfare of farmers who lost their farmland attracted a widespread concern within the society and academia. However, further research about differentiated policies according to the characteristics of different farmer groups is still need to be conducted. This article divides the land-lost farmers into three age groups: younger than 45, 45–65, and more than 65. It proposes a welfare index system including eight functional areas based on different age groups of affected farmers, taking four districts of Wuhan City as case study area. Fuzzy mathematics method is used to derive the aggregated welfare effect index. Our analysis show that the overall welfare levels of land-lost farmers of all age groups declined, but with a varying degree, with the level of welfare in those farmers who are 45–65 years old, younger than 45 years old, and older than 65 years old decreased by 18.7%, 16.6%, and 12.7%, respectively. The direction and degree of effects on the functional activity index varies among different groups. Economic conditions, living environment, health, and social participation of all age groups decrease while social security and housing conditions increase. On the other hand, development opportunities, social communication, and leisure have different changing directions in different age stages. These results call for differentiated and tailor-made compensation policies for land-lost farmers, towards improving the welfare levels of all farmers and reduce the disparity among them. 相似文献