A novel indicator system for catalytic spectrophotometric determination and speciation of inorganic selenium species （Se（Ⅳ）, Se（Ⅵ）） at trace levels in natural lake and river water samples

A novel catalytic kinetic method is proposed for the determination of Se(IV), Se(VI), and total inorganic selenium in water based on the catalytic effect of Se(IV) on the reduction of Celestine blue by sodium sulfide at pH 7.0 phosphate buffer. The fixed-time method was adopted for the determination and speciation of inorganic selenium. Under the optimum conditions, the two calibration graphs are linear with a good correlation coefficient in the range 2–20 and 20–200 μg·L⁻¹ of Se(IV) for the fixed-time method at 30°C. The experimental and theoretical detection limits of the developed kinetic method were found to be 0.21 and 2.50 μg·L⁻¹ for the fixed-time method (3 min). All of the variables that affect the sensitivity at 645 nm were investigated, and the optimum conditions were established. The interference effect of various cations and anions on the Se(IV) determination was also studied. The selectivity of the selenium determination was greatly improved with the use of the strongly cation exchange resin such as Amberlite IR120 plus as long as chelating agents of thiourea and thiosulphate. The proposed kinetic method was validated statistically and through recovery studies in natural water samples. The relative standard deviations (RSDs) for ten replicate measurements of 2, 10, and 20 μg·L⁻¹ of Se(IV) change between 0.35% and 5.58%, while the RSDs for ten replicate measurements of 3, 6, and 12 μg·L⁻¹ of Se(VI) change between 0.49% and 1.61%. Analyses of a certified standard reference material (NIST SRM 1643e) for selenium using the fixed-time method showed that the proposed kinetic method has good accuracy. The Se(IV), Se(VI), and total inorganic selenium in lake and river water samples have been successfully determined by this method after selective reduction of Se(VI) to Se(IV).     

茈碧花

清代《云南通志》中有：“茈碧花产浪穹县（今洱源县）宁湖中，似莲而小，叶如荷钱，茎长六七丈，气清芬，采而烹之，味美于尊菜（莼莱）。八月花开满湖，湖名茈碧以此。”据此段文字记载我国云南省洱源城边有个天然湖泊，湖内特生一种珍贵水生植物茈碧花.     

安普布线为苏州金鸡湖大酒店构建现代化通讯布线系统

1项目背景苏州工业园区金鸡湖大酒店位于苏州工业园区金鸡湖和独墅湖这两大天然湖泊之间,占地面积约35公顷。金鸡湖大酒店按中国国家旅游局最新颁布的白金五星级标准设计,一期金鸡湖大酒店63套客房,     

数字

中国平均每年消失20个天然湖泊，全国2320个土地开发整理项目效益显现，三江集团投资13．5亿元在汉参与新农村建设，湖北公布首批污染企业名单年内关闭200家，海口将投资6500万治理181条小街巷。[编者按]     

全球变暖七大惊人后果

我国最近50年减少约1000个内陆湖泊，每年平均有20个天然湖泊消亡。 我国湖泊面临四大严峻挑战：湖区防洪能力依然偏低；湖泊萎缩退化形势严峻；湖泊水质恶化趋势尚未遏制；湖泊生态功能严重退化。     

汾源胜景

<正>汾源景区位于管涔山东麓,为国家水利风景区,是三晋母亲河——汾河的发源地。景区内原始森林苍翠欲滴,珍禽异兽穿梭林间;万年冰洞蔚为奇观,悬崖栈道惊险绝伦:恍若明镜的天然湖泊镶嵌于高山之巅,广袤无垠的马仑草原上牛羊奔放;     

尕海

正洮河上游支流周科河源头处的一天然湖泊,是黄河流域少有而宝贵的天然湖泊之一。尕海位于甘肃省碌曲县西南部,被誉为"高原明珠",湖泊高程3 479.7 m,北距碌曲县城56 km,国道G213线从旁通过。尕海水源由西倾山东端和郭尔莽梁北侧的众多细小支流从东、南、西三面汇集而成,包括周科河、噶尔且科合、多木     

安普布线为金鸡湖大酒店 构建现代化通讯布线系统

项目背景 苏州工业园区金鸡湖大酒店位于苏州工业园区金鸡湖和独墅湖这两大天然湖泊之间,占地面积约35公顷。金鸡湖大酒店按中国国家旅游局最新颁布的白金五星级标准设计,一期金鸡湖大酒店63套客房，二期金鸡湖凯宾斯基大酒店456间客房，将建设成为国际一流的森林花园式酒店。酒店总体包括一个超五星级商务酒店和数栋国宾级接待别墅，     

茈碧花

清代《云南通志》中有：“茈碧花产浪穹县（今洱源县）宁湖中，似莲而小，叶如荷钱，茎长六七丈，气清芬，采而烹之，味美于尊菜（莼莱）。八月花开满湖，湖名茈碧以此。”据此段文字记载我国云南省洱源城边有个天然湖泊，湖内特生一种珍贵水生植物茈碧花.     

广州增城荔城湖

项目背景 广州作为广东省省会,其城市的发展正迅速扩展至增城等周边地区。荔城湖项目位于增城,地块被天然湖泊、山谷和茂密的绿色植物所环绕。因地制宜地创造居住区的关键在于实现自然环境和建筑物之间的平衡．为了降低建筑物体量对自然环境的影响．设计师构思了一个与自然随意结合的雕塑般的建筑群落,灵活处理建筑物和人们活动场所的结合,同时提升现有风景的内在品质。该项目由6座坐落于湖畔的独立小商店、2座6层高的住宅楼房以及100幢个性别墅组成。