Fluoride removal and its impact on oral health in Sri Lanka's dry zone: Discussion and recommendation

Fifty percent of the dry zone areas in Sri Lanka have fluoride levels above 1 ppm. This paper discusses the ground conditions and recommends an appropriate range of fluoride in drinking water which can support preventive practices for improving the oral health of children 8-years old and younger. In efforts to address the Chronic Kidney Disease of Unknown etiology (CKDU), water treatment to reduce contaminant level in potable water has been implemented. Such treatment would also remove fluoride and has resulted in potable water with various fluoride levels, depending on concentrations in the raw water. While it is important to reduce fluoride levels, it is important to have appropriate residual levels for prevention of dental caries. It needs, however, to be noted fluoride in excess can cause dental fluorosis. In Sri Lanka's dry zone areas increasing prevalence of dental fluorosis with decreasing prevalence of dental caries has been noted. Consumption of tea and powdered milk could increase total intake of fluoride. Fluoridated toothpaste, when used properly, may, however, result in negligible intake of fluoride. Sri Lanka's hot tropical climate which results in substantial intake of fluids reinforces the need to consider reduction in water fluoride. Consideration of local studies and international standards indicate fluoride levels should be in the range of 0.225–0.500 ppm. In the range of 0.225–0.500 ppm, the prevalence of dental fluorosis and caries was only 14% and 8%, respectively, in an endemic district. When fluoride levels are above 0.500 ppm, the issue of dental fluorosis shall need to be addressed. When levels are below 0.225 ppm, oral health care services shall need to be directed at preventing dental caries.     

长江河口近岸水体自然净化作用及其初步评价

按照水体的净化机理，结合长江口和上海滨岸带近岸水体的物理、化学和生物等因素的实际特征，对近岸水体的自然净化作用进行了阐述和分析。并在历史资料和实测资料基础上，就近岸水体的自然净化作用进行了评价。评价结果表明，因长江河口近岸水体存在较强的自然净化作用机制，近岸水体体的自然净化能力较强，环境容量较大，但由于污染物输入量的不断增加，部分岸段近岸水体的环境质量有逐渐下降的趋势；近岸水体的自然净化作用具有明显的季节性变化，长江口南岸水域洪水季节水体的自然净化作用比估水季节强，而杭州湾北岸水域的自然净化作用表现为相反的变化趋势，因此建议在近岸污水排放过程中应考虑近岸水体的净化能力，遵循水体的自然净化作用规律。     

钯离子液相催化氧化低浓度磷化氢

采用Pd^2＋液相催化氧化低浓度PH3，考察了Pd^2＋浓度、O2体积分数、PH3质量浓度、混合气流量、反应温度等因素对Pd^2＋吸收液去除低浓度PH3效果的影响。实验结果表明，采用10mL Pd^2＋浓度为0．112mol／L的水溶液作为吸收液净化含低浓度PH3的混合气，在反应温度22℃、O2体积分数5％、PH3质量浓度850mg／m^3、混合气流量190mL／min的条件下，印min之内PH3去除率保持在90％以上。Pd^2＋浓度越高、O2体积分数越大、反应温度越高，PH3去除率越高；混合气流量越大，PH3去除率越低；反应温度越低、O2体积分数越大，PH3去除率的下降速率越小。     

电絮凝净化含聚污水影响因素研究

目的为保障油田正常安全生产,促进油田含聚污水的循环利用。方法采用电絮凝技术单因素研究方法开展净化含聚污水的静态实验研究,探讨外加电流密度、极板间距、初始pH及聚合物浓度等因素对净化效果的影响规律。结果当初始pH为7.0,电流密度为4.0 m A/m2,极板间距为1.0 cm,电解16 min时,综合处理效果最佳。此时,含油量与浊度去除率分别为98.85%,99.93%,处理每克油平均消耗为0.0494 g的Al,处理每立方米含聚污水的能耗为0.2895 k Wh。污水中的聚合物浓度越小,净化效果越好。结论中性处理,极板间距为1.0 cm,外加电流密度为4.0 m A/m2,通电16 min是最佳处理条件。     

太湖水质氮素质量浓度时空差异特征及影响因素分析

通过对2014—2016年湖体水质中氮素质量浓度分析,结合出入湖总氮浓度、水量、湖体水生生态等影响因素,发现太湖水体中总氮浓度呈现逐年下降的趋势,各监测点位总氮为0.530 mg/L～5.51 mg/L,时空分布不均,差异明显。时间上,总氮浓度表现为春季最高,夏季和秋季最低,且月均值变化曲线呈现出规律的正弦函数波形。空间上,总氮浓度大致表现出由西部湖区向东部湖区递减的趋势,呈现西部湖区﹥北部湖区﹥南部湖区﹥湖心区﹥东部湖区。要改善湖体水质,不仅要切断污染源,而且要加强水生生态功能修复。     

标准BOD5测定法的"空气净化--稀释水曝气"装置研究

"稀释与接种法"是BOD5的标准测定方法,制备溶解氧接近饱和且不含能干扰生化耗氧过程的物质的稀释水,是该法重要的工作之一.由真空泵带动的"空气净化--稀释水曝气"装置,流程合理、装配容易、调控灵活,可连贯进行空气净化与稀释水曝气,而制取符合质量要求的稀释水.     

汽车尾气污染及其净化处理技术

本文详细阐述了汽车尾气的有害成份及其对人类健康的危害。为此 ,应该采取净化处理措施 ,减少或者消除有害气体的产生 ,为大气环境洁净而创造条件。     

Heavy metals in water bodies purified by suspended substrate of rivers

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硫代磷酸二乙酯加热水解的研究

在二升高压釜中,氮气氛条件下研究了有机磷农药废水的主要污染物质——硫代磷酸二乙酯(浓度为100ppm)的水解动力学.运用气相色谱法,在pH2—4,温度140—190℃范围,得到不同条件下的一级反应速率常数k,获得pH、温度与反应速率常数的关系,并对硫化磷酸二乙酯的水解条件进行了讨论.     

煤矿含悬浮物矿井水净化处理技术探讨

论述了含悬浮物矿井水净化处理利用的必要性，矿井水水质，水量和处理要求，现有的处理工艺，混凝剂及混合方式，主要处理构筑物和消毒方式等。指出了在确定处理规模，处理工艺，设计参数，药剂选择和投加过程中存在的问题，并给出了解决上述问题的方法。