Comparison of Nitrate Levels in Raw Water and Finished Water from Historical Monitoring Data on Iowa Municipal Drinking Water Supplies

Nitrate contamination of water sources is a concern where large amounts of nitrogen fertilizers are regularly applied to soils. Ingested nitrate from dietary sources and drinking water can be converted to nitrite and ultimately to N-nitroso compounds, many of which are known carcinogens. Epidemiologic studies of drinking water nitrate and cancer report mixed findings; a criticism is the use of nitrate concentrations from retrospective drinking water data to assign exposure levels. Residential point-of-use nitrate data are scarce; gaps in historical data for municipal supply finished water hamper exposure classification efforts. We used generalized linear regression models to estimate and compare historical raw water and finished water nitrate levels (1960s--1990s) in single source Iowa municipal supplies to determine whether raw water monitoring data could supplement finished water data to improve exposure assessment. Comparison of raw water and finished water samples (same sampling date) showed a significant difference in nitrate levels in municipalities using rivers; municipalities using other surface water or alluvial groundwater had no difference in nitrate levels. A regional aggregation of alluvial groundwater municipalities was constructed based on results from a previous study showing regional differences in nitrate contamination of private wells; results from this analysis were mixed, dependent upon region and decade. These analyses demonstrate using historical raw water nitrate monitoring data to supplement finished water data for exposure assessment is appropriate for individual Iowa municipal supplies using alluvial groundwater, lakes or reservoirs. Using alluvial raw water data on a regional basis is dependent on region and decade.     

Measurement of gross alpha and gross beta activity concentrations in human tooth

The gross alpha and gross beta activity concentrations were measured in human tooth taken from 3 to 6 age-groups to 40 and over ones. Accumulated teeth samples are investigated in two groups as under and above 18 years. The gross alpha and beta radioactivity of human tooth samples was measured by using a gas-flow proportional counter (PIC-MPC 9604-α/β counter). In tooth samples, for female age-groups, the obtained results show that the mean gross alpha and gross beta activity concentrations varied between 0.534-0.203 and 0.010-0.453 Bq g⁻¹ and the same concentrations for male age-groups varied between 0.009-1.168 and 0.071-0.204 Bq g⁻¹, respectively.     

Effects of Groundwater-Flow Paths On Nitrate Concentrations Across Two Riparian Forest Corridors1

Speiran, Gary K., 2010. Effects of Groundwater-Flow Paths on Nitrate Concentrations Across Two Riparian Forest Corridors. Journal of the American Water Resources Association (JAWRA) 46(2):246-260. DOI: 10.1111/j.1752-1688.2010.00427.x Abstract: Groundwater levels, apparent age, and chemistry from field sites and groundwater-flow modeling of hypothetical aquifers collectively indicate that groundwater-flow paths contribute to differences in nitrate concentrations across riparian corridors. At sites in Virginia (one coastal and one Piedmont), lowland forested wetlands separate upland fields from nearby surface waters (an estuary and a stream). At the coastal site, nitrate concentrations near the water table decreased from more than 10 mg/l beneath fields to 2 mg/l beneath a riparian forest buffer because recharge through the buffer forced water with concentrations greater than 5 mg/l to flow deeper beneath the buffer. Diurnal changes in groundwater levels up to 0.25 meters at the coastal site reflect flow from the water table into unsaturated soil where roots remove water and nitrate dissolved in it. Decreases in aquifer thickness caused by declines in the water table and decreases in horizontal hydraulic gradients from the uplands to the wetlands indicate that more than 95% of the groundwater discharged to the wetlands. Such discharge through organic soil can reduce nitrate concentrations by denitrification. Model simulations are consistent with field results, showing downward flow approaching toe slopes and surface waters to which groundwater discharges. These effects show the importance of buffer placement over use of fixed-width, streamside buffers to control nitrate concentrations.     

CaH2对Cu-Ce-La-ZSM-5催化分解NO性能的影响

实验采用一步离子交换法制备Cu-Ce-La-ZSM-5催化剂,然后采用共混法制得Cu-Ce-La-ZSM-5/CaH2催化剂。采用扫描电镜（SEM）,电感耦合等离子体发射光谱（ICP-AES）,X射线衍射（XRD）,红外（FTIR）以及NO吸脱附（NO-TPD）对催化剂进行表征。结果显示CaH2的加入使得催化剂中铜离子存在形式发生变化,催化剂表面变光滑洁净,并且吸附NO能力增强。NO催化分解实验的结果表明CaH2提高了催化剂活性和抗氧性。CaH2助催性是由于其受热分解过程中产生的H2能将Cu^2＋还原为具有催化活性的Cu^＋,同时使催化剂表面洁净光滑更容易吸附NO。     

钙基固定剂对制氢和污染性气体减排的影响

在未来相当长的一段时间内,煤气化仍是大规模制取氢气的主要途径。目前,常规煤气化过程得到的是H2、CO和CO2为主的混合气,需要通过净化、变换和分离工艺才能得到洁净的氢气,工艺过程复杂。采用连续式超临界水反应装置,以质量分数为20%的水煤浆为反应原料,考察了Ca/C摩尔比和温度对褐煤制氢系统的影响。试验结果表明：Ca（OH）2不仅可以很好地固定气相中的CO2和硫化物,而且对煤气化过程也表现出较好的催化作用。反应温度600℃,压力为25MPa的条件下,与未加Ca（OH）2相比,Ca/C摩尔比为0.45时,气体中CO2的体积分数由50.7%降至1.0%,趋于完全固定;硫化物浓度由10 878mg/m3降至807mg/m3;H2的体积分数由32.4%增至73.3%。Ca（OH）2对煤气化的催化作用在高温下更加明显。     

钙基脱硫剂孔隙中SO2气体非线性扩散的研究

以动态生成的CaO孔隙网络为骨架,按照不退行随机行走模型（NRRW）,模拟气体分子在CaO孔隙中的扩散过程,计算了SO2分子的扩散系数和行走维数,并在SO2非线性扩散反应方程基础上,分析了CaO颗粒孔隙中SO2浓度的分布特性。     

基于白碳黑的水化硅酸钙制备及其磷回收特性简

以白碳黑、硅灰、硅藻土和硅胶筛选硅质原料,并与钙质原料电石渣制备了水化硅酸钙。借助XRF、BET、FTIR等表征手段,通过多次重复除磷实验,研究了硅质原料特性对水化硅酸钙回收磷性能的影响。结果表明,白碳黑具有极高的反应活性,因此可作为制备具有磷回收特性的水化硅酸钙的硅质原料。结合XRD等表征发现,白碳黑的有效利用率是影响水化硅酸钙回收磷性能的关键,该利用率取决于白碳黑与电石渣的摩尔配比以及水热反应温度。当电石渣与白碳黑的摩尔比为1.6：1,反应温度为170℃时,白碳黑具有最佳的利用效率。该条件制备的水化硅酸钙可作为晶种,在其表面结晶形成羟基磷灰石,从而达到磷回收的目的,磷回收后固体物质中的磷含量为19.05%。     

磷石膏水热法合成硫酸钙晶须

以磷石膏为原料,二水合硫酸钙、硫酸镁、甘油为添加剂,采用水热法合成硫酸钙晶须,考察了料浆含量、反应温度、反应时间、体系pH等因素对晶须的直径和长径比的影响;并采用SEM技术观察硫酸钙晶须的形貌。实验结果表明,当磷石膏含量2.5%（w）、反应温度130 ℃、反应时间4 h、体系pH 4时,制备得到的硫酸钙晶须长径比为56.24,平均直径为0.17 μm。SEM表征结果显示,硫酸钙晶须形貌规整、分散均匀、直径较小,达百纳米级。     

阿什河水系枯水期氮污染特征与同位素源解析

在阿什河水系设置20个采样点,采用水质监测技术和稳定氮同位素示踪技术,研究了枯水期阿什河氮污染特征和硝酸盐氮污染来源。结果表明:(1)阿什河枯水期大部分采样点氨氮浓度较低,大部分区域达到或优于《地表水环境质量标准》(GB3838—2002)中Ⅲ类。上游河段硝酸盐氮浓度较低,中游河段较高,到下游河段略有降低。总氮浓度较高,最高达19.4mg/L。(2)阿什河水系采样点15 N的丰度(δ15 N)主要处于0.11%~0.21%、0.42%~0.78%、0.83%~0.88%和1.09%~1.26%。稳定15 N同位素示踪解析阿什河硝酸盐氮污染来源表明,阿什河上游污染源主要为大气沉降、土壤有机氮和人工化肥;中游主要受畜禽养殖污水和生活污水污染;下游主要受城镇生活污水和工业废水影响。     

餐厨垃圾厌氧消化中硬脂酸钙的形成及作用

在稳定运行的餐厨垃圾单相厌氧消化体系中,出现白色颗粒状物质,且随着负荷的提高,其数量和粒径不断增加。利用能谱技术分析白色颗粒的元素组成,结合傅里叶红外光谱和13C核磁共振技术分析白色颗粒中的官能基团。经过研究分析认为,该白色颗粒的主要成分为长链羧酸钙盐,具体为硬脂酸钙。同时,对其形成过程进行了分析。该物质的形成对餐厨垃圾中油脂的去除提供了新的思路和途径。