A stream tracer technique employing ionic tracers and specific conductance data applied to the Maimai catchment,New Zealand

The stream tracer technique and transient storage models (TSMs) have become common tools in stream solute and hyporheic exchange studies. The expense and logistics associated with water sample collection and analysis often results in limited temporal resolution of stream tracer breakthrough curves (BTCs). Samples are often collected without a priori or real‐time knowledge of BTC information, which can result in poor sample coverage of the critical shoulder (initial rise) and tail (post‐steady state fall) of the BTC. We illustrate the use of specific conductance (SC) measurements as a surrogate for conservative dissolved tracer (Br⁻) samples. The advantages of collecting SC data for use in the TSM are (1) cost, (2) ease of data collection, and (3) well‐defined breakthrough curves, which strengthen TSM parameter optimization. This method is based on developing an ion concentration (IC)–SC relationship from limited discrete tracer solute samples. SC data can be collected on a more frequent basis at no additional analysis cost. TSM simulations can then be run for the conservative tracer data derived from SC breakthrough curves and the IC–SC relationship. This technique was tested in a 120 m reach of stream (2–60 m subreaches) in the Maimai M15 catchment, New Zealand during baseflow recession. Dissolved LiBr was injected for 12·92 h, with Br⁻ as the conservative ion of interest. Four TSM simulations using the OTIS model are optimized using UCODE to fit (1) Br⁻ data derived from the Br⁻–SC relationship (n = 1307 observations at each of two stream sampling sites), (2) all stream Br⁻ data collected (n = 58 in upper reach, n = 60 in lower reach), (3) half of the stream Br⁻ data collected, and (4) 20 stream Br⁻ samples from each site. No two simulations resulted in the same optimal parameter values. Results suggest that the greater the frequency of observations, the greater the confidence in estimated parameter values. Br⁻–SC simulations resulted in the best overall model fits to the data, with the lowest calculated error variance of 6·37, narrowest 95% parameter estimate confidence intervals, and the highest correlation coefficient of 0·99 942, among the four simulations. This is largely due to the improved representation of the shoulder and tail of the BTC with this method. The IC–SC correlation method is robust in situations in which (1) changes in background SC data can be accounted for, and (2) the data used to define the IC–SC relationship are representative of the range of data collected. This method provides more efficient sample analysis, improved data resolution, and improved model results compared to the alternative stream tracer data gathering methods presented. Additionally, we describe a new parameterization of the cross‐sectional area of the stream during flow recession, as a function of discharge, based on a stream hydraulic geometry relationship. This variant of the OTIS model provides a more realistic representation of stream dynamics during unsteady discharge. Copyright © 2005 John Wiley & Sons, Ltd.     

Methyl halide hydrolysis rates in natural waters

International regulations are under consideration for methyl bromide because of its high time dependent ozone depletion potential. Geocycling of the species is not well understood, and removal may occur in several types of natural water incuding the oceanic and those in soils. The hydrolysis reaction is a dominant loss pathway in environmental aqueous systems, but rate constants have generally been reported only in distilled water and at greater than room temperature. Here we present measurements in sodium chloride solutions and in seawater in addition to pure water, and at temperatures across the oceanographic range. The reaction could be followed even in solutions near the freezing point because product methanol was monitored in the method of initial rates. Time constants for methyl bromide hydrolysis fall between 10 and 1000 days over the temperatures of the sea, and are always within an order of magnitude of the fastest abiotic destruction mode, chlorination. Activation energies for the two processes are similar so that the ratio of their time scales does not vary with oceanic location. Hydrolysis rate constants are also listed for the closely related compounds methyls iodide and chloride. Solvolysis of the methyl halides in natural waters acts as a source of methanol to the ocean and atmosphere.     

Bromide removal and recovery with layered double hydroxides as an adsorbent

Grignard regents have been applied extensively in chemical industry, especially in pharmacy. A mass of bromide-containing wastewater was produced after reaction, and ozonation of these organic contaminants can produce bromate and other brominated pollutants. The US Environmental Protection Agency （EPA） has established a maximum contaminant level of 10 μg/L for bromate in finished water. Therefore, it is necessary and significant to remove the DBP （disinfection by-products） precursor - bromide. On the other hand, since the bromine is a valuable element, recovery of it from wastewater is significant. Bromide removal is important to control DBP （disinfection by-products） contaminant and an ion exchange process is one of several treatment processes for this purpose. Layered double hydroxides （LDHs） are useful as adsorbents for bromide removal because of theft ion exchange properties. In this study, the adsorption properties of LDHs for bromide and the method of regeneration of this material were examined. It has been found that the LDHs with Mg/Al molar ratio of 2 represented the highest capacity to remove bromide ion from aqueous solution at pH 6.0. The equilibrium isotherms of uptake of bromide by CLDH were well fitted by the Langmuir equation. Bromide adsorbed on the LDHs was effectively desorbed at 30% Na2CO3 solution and the LDHs were regenerated at the same time. The regenerated LDHs could be reused repeatedly for the bromide removal. Bromide in the exhausted desorption solution was recovered as bromine by oxidation using Cl2.     

Global Modelling of the Atmospheric Methyl Bromide Budget

A global three-dimensional chemical transport model has been used to identify and evaluate possible candidates for the `missing' surface source required to balance the atmospheric budget of methyl bromide. Both natural and anthropogenic emissions of methyl bromide are `coloured' in the model, thus allowing the global CH₃Br distribution to be broken-down into its source components. These coloured CH₃Br tracers are then combined in various ways to create one base-line emission scenario and five further plausible scenarios. The additional emission scenarios are specifically designed to test whether the geographical distribution and seasonal cycles of additional vegetation and/or increased biomass burning emissions are consistent with atmospheric observations of methyl bromide mixing ratios. Due to an imbalance in our current understanding of the methyl bromide budget, simulated CH₃Br mixing ratios from the base-line emission scenario are significantly lower than atmospheric measurements. Both the inclusion of a vegetation source in the tropics and a double strength biomass burning source substantially improve the agreement between model simulations and atmospheric measurements compared with the base-line emission scenario. While measurement data provides useful information on global fluxes and regional CH₃Br seasonal cycles, small differences between the simulated seasonal cycles of different emission scenarios makes it difficult to distinguish between the relative likelihoods of model scenarios containing a tropical vegetation source or an increased biomass burning source. Further measurements performed in continental mid-to-high northern latitudes, central-southern Africa and South America would be of particular benefit in future attempts to constrain the location and magnitude of the natural terrestrial sources of methyl bromide.     

氯化钠存在下氯化亚锡-十六烷基三甲基氯化铵体系浮选分离复杂金属基体中锇

研究了氯化钠存在下氯化亚锡-十六烷基三甲基氯化铵体系对Os（Ⅳ）-三氯锡酸络阴离子的浮选行为。实验表明，在盐酸介质中，体系可以浮选分离Os（Ⅳ），其浮选率为95．2％。98.0％。方法加标回收率为94．0％-98．5％，精密度为2．1％-7．7％（RSD，n=5）。方法可用于从大量基体金属中分离Os（Ⅳ），对实际样品分离的分析结果与其他方法推荐值相符。     

混合表面活性剂存在下锰的高灵敏显色反应研究

研究了碱性介质中,Ｍｎ（Ⅱ）被空气氧化生成Ｈ２ＭｎＯ３,然后在Ｈ３ＰＯ４介质中,Ｃｕ（Ⅱ）和阳离子型有机相／水相微乳液（ＣＴＭＡＢ／戊醇／正庚烷／水）的存在下,Ｍｎ（Ⅳ）与二安替比林对乙氧基苯基甲烷（ＤＡｐＥＭ）生成橙色产物,λｍａｘ为４５０ｎｍ,ε＝１．９５×１０５Ｌ·ｍｏｌ－１·ｃｍ－１。Ｍｎ（Ⅱ）的质量浓度在０～３２０μｇ／Ｌ内符合比尔定律。方法用于合金中锰的测定,结果与标准值符合,５次测定结果的ＲＳＤ＜３％。     

离子色谱法测定土壤中氯、溴

采用扩散技术处理土壤样品,同时用离子色谱测定样品中氯和溴,该方法检出限分别达到4×10-6和0.3×10-6,精密度分别达到9.38%和7.20%。测定快速、操作简单,适合大批量样品分析。     

Variability of unsaturated Bromide fluxes as measured through a layered volcanic vadose zone in New Zealand

The measured drainage fluxes through a layered volcanic vadose zone exhibited high spatial variability as a consequence of heterogeneous flow conditions. The drainage flux variability was quantified using automated equilibrium tension lysimeters, installed in close‐proximity and resulted in high variability in the Br masses recovered from a conservative tracer experiment. The primary cause of the heterogeneous flow was attributed to textural changes occurring at the interface between volcanic layers, resulting in development of funnel‐flow patterns, and further enhanced by the existence of hydrophobic conditions. The Br recoveries in individual automated equilibrium tension lysimeters were used to determine the corresponding variable sizes of the surface areas contributing drainage to the lysimeters. The tracer experiment confirmed the existence of unsaturated lateral transport occurring at the sloping interface of the coarse Taupo Ignimbrite material with the silty Palaeosol layer at approximately 4.2 m depth. This study demonstrates that measurements of both flux and solute concentrations at multiple locations are essential when heterogeneous flow is suspected to be present, to be able to determine reliable estimates of contaminant leaching through the vadose zone at the plot scale. Copyright © 2013 John Wiley & Sons, Ltd.     

Distribution,Origin and Development Status of Underground Brine Resource along the Coast of Laizhou Bay,Shandong Province

正The underground brine resource along the coast of Laizhou Bay is the world’s rare shallow underground brine resource,which occurs in the Laizhou city in the east,and extends to the coastal area of the Binzhou city in     

华北平原地下水补给量计算分析

采用溴示踪法研究华北平原山前冲积平原和中部平原有灌溉和无灌溉区域的地下水补给,得到研究区平均地下水补给量为126.10 mm,平均补给系数为0.185 2,有灌溉实验点的补给量和补给系数大于无灌溉实验点。同时对示踪剂运移深度和含水量分布、降雨灌溉量和地下水埋深等影响因素进行分析。将各实验点计算结果与国内有关学者采用示踪剂法所得到的补给系数进行对比分析,论证了研究结果的可靠性,此研究成果可为华北平原地下水资源分析提供重要参考。