Tracer and hydrometric study of preferential flow in large undisturbed soil cores from the Georgia Piedmont,USA

We studied the temporal patterns of tracer throughput in the outflow of large (30 cm diameter by 38 cm long) undisturbed cores from the Panola Mountain Research Watershed, Georgia. Tracer breakthrough was affected by soil structure and rainfall intensity. Two rainfall intensities (20 and 40 mm hr⁻¹) for separate Cl⁻ and Br⁻ amended solutions were applied to two cores (one extracted from a hillslope soil and one extracted from a residual clay soil on the ridge). For both low and high rainfall intensity experiments, preferential flow occurred in the clay core, but not in the hillslope core. The preferential flow is attributed to well‐developed interpedal macrochannels that are commonly found in structured clay soils, characteristic of the ridge site. However, each rainfall intensity exceeded the matrix infiltration capacity at the top of the hillslope core, but did not exceed the matrix infiltration capacity at the middle and bottom of the hillslope core and at all levels in the clay core. Localized zones of saturation created when rainfall intensity exceeds the matrix infiltration capacity may cause water and tracer to overflow from the matrix into macrochannels, where preferential flow occurs to depth in otherwise unsaturated soil. Copyright © 1999 John Wiley & Sons, Ltd.     

衍生化气相色谱-质谱法测定复垦土地样品中19种酚类污染物

近年来国家对自然环境的保护愈加重视,更多被破坏或污染的土地需要进行复垦整治.在评价效果时,需要检测酚类等多项污染物指标.采用气相色谱与气相色谱-质谱联用等方法对酚类化合物直接测定时,存在色谱响应值低、稳定性差、检出限高等问题.本文针对复垦土地样品基质复杂、干扰因素多、前处理困难等特点,对该类样品的提取与净化方法进行筛选...     

表面活性剂对钪－铜铁试剂络合吸附波的增敏效应

探讨了各种类型的表面活性剂对Ｓｃ－铜铁试剂体系的增敏效应；观察到在ｐＨ９．０的ＮＨ＿４ＯＨ－ＮＨ＿４Ｃｌ缓冲介质中，溴化十四烷基三甲铵使该体系催化波灵敏度提高了２５倍。峰电位在－１．５０Ｖ（ｕｓ．Ａｇ／ＡｇＣｌ），峰高与Ｓｃ浓度在２～４０ｎｇ／ｍｌ呈线性关系，检出限１ｎｇ／ｍｌ；用拟定的方法测定了岩石样品中的痕量Ｓｃ；并对其极谱性质和表面活性剂增敏机理进行了探讨。     

溴代十六烷基吡啶存在下金与硫代米蚩酮显色反应的研究及其应用

作者研究了在阳离子表面活性剂溴代十六烷基吡啶(CPB)存在下,金与硫代米蚩酮的显色反应。最佳显色酸度为pH3.0—4.3。表观摩尔吸光系数为1.32×10~5L·mol~(-1)·cm~(-1)。金的含量在0—17μg·(25ml)~(-1)范围内符合比尔定律。外来离子的干扰用活性炭吸附来消除。这个方法用于测定矿石中的微量金取得满意的效果。     

改性提高膨润土阳离子交换容量研究

研究了焙烧活化、酸活化、氯化钠活化、溴化十六烷基三甲铵活化等改性方法对膨润土阳离子交换容量的影响。结果表明,450℃焙烧2 h,膨润土阳离子交换容量可提高30%以上,0.01 mol.L-1氯化钠和0.3 mol.L-1溴化十六烷基三甲铵活化处理均可使膨润土阳离子交换容量提高10%以上,0.1 mol.L-1盐酸活化处理对提高膨润土的阳离子交换容量效果不明显,还深入讨论了改性提高澎润土阳离子交换容量的机理。     

Infiltration and solute transport under a seasonal wetland: bromide tracer experiments in Saskatoon,Canada

In the northern glaciated plain of North America, the duration of surface water in seasonal wetlands is strongly influenced by the rate of infiltration and evaporation. Infiltration also plays important roles in nutrient exchange at the sediment–water interface and groundwater recharge under wetlands. A whole‐wetland bromide tracer experiment was conducted in Saskatchewan, Canada to evaluate infiltration and solute transport processes. Bromide concentrations of surface water, groundwater, sediment pore water and plant tissues were monitored as the pond water‐level gradually dropped until there was no surface water. Hydraulic head gradients showed strong lateral flow from under the wetland to the treed riparian zone during the growing season. The bromide mass balance analysis showed that in early spring, almost 50% of water loss from the wetland was by infiltration, and it increased to about 70% in summer as plants in and around the wetland started to transpire more actively. The infiltration contributed to recharging the shallow, local groundwater under the wetland, but much of it was taken up by trees without recharging the deeper groundwater system. Emergent plants growing in the wetlands incorporated some bromide, but overall uptake of bromide by vegetation was less than 10% of the amount initially released. After one summer, most of the subsurface bromide was found within 40–80 cm of the soil surface. However, some bromide penetrated as deep as 2–3 m, presumably owing to preferential flow pathways provided by root holes or fractures. Copyright © 2004 Crown in the Right of Canada. Published by John Wiley & Sons, Ltd.     

In situ Study of Bromide Tracer and Oxygen Flux in Coastal Sediments

Laboratory and in situ experiments were performed to assess the use of bromide as a tracer forin situ studies of benthic solute exchange. Bromide was used in the benthic chamber lander ‘ Elinor ’ for flux measurements in coastal sediments of the German Bight, Kiel Bight and Skagerrak (28–700 m water depth). Tracer and total oxygen uptake were monitored simultaneously in the same chamber incubation. Concurrently, in situ oxygen micro-profiles were recorded at the same locations by the profiling lander ‘ Profilur ’. Deployment in an anoxic silt (Kiel Bight) confirmed that in the absence of bioturbation and advection, tracer transport into the sediment was driven solely by molecular diffusion. This flux could be well described by a simple box model accounting for molecular diffusion only. In oxic sediments (German Bight and Skagerrak) enhanced exchange of bromide tracer due to bioirrigation parallelled enhanced oxygen uptake equivalent to a 4-fold molecular diffusive flux. Our experiments showed that incubations can be short. Depending on irrigation activity of the fauna, however, incubation length should exceed 3 h in order to provide a useful data base for flux calculations. The method demonstrating caveats is discussed and indicate possible improvements. The results show how the bromide tracer addition can be used as a tool for determining solute fluxes exceeding diffusive flux in benthic chamber incubations.     

铌与溴邻苯三酚红和丁基罗丹明B协同显色及其应用

研究了在溴化十六烷基吡啶存在下,铌与溴邻苯三酚红及丁基罗明Ｂ的协同显色反应。在优化条件下,体系所形成的多元配合物最大吸收波长位于６３５ｎｍ处,表观摩尔吸光系数为１．４３＊１０＾５Ｌ．ｍｏｌ＾－１．ｃｍ＾－１,铌的质量浓度在０－１．００ｍｇ／Ｌ符合比尔定律。考察了３０多种共存离子的影响。结果表明干扰较少,钽的允许量可以达到铌的２０倍。方法用于水系沉积,煤渣,合金钢中铌的测定,结果与标准值相符。加标回     

Heterogeneous Chemistry of Nitryl Halides in Relation to Tropospheric Halogen Activation

The heterogeneous chemistry of nitryl chloride and nitryl bromide by salt containing solutions was studied as a function of temperature in the range from 275 to 293 K with the wetted-wall flowtube combined with FTIR and mass spectrometry detection. Uptake coefficients and values of the product Hk^1/2 on these saline solutions have been determined. For nitryl halides interacting with NaI and NaBr solutions, the values of the product Hk^1/2 are respectively 4384.7±326.7 and 103.1±18.7 M atm^-1 s^-1/2 for nitryl chloride at 275 K and 544.2±94.7 and 47.7±15.2 M atm^-1 s^-1/2 for nitryl bromide at 278 K. When reacting with NaI or NaBr solutions, these heterogeneous reactions release, as major products, the molecular forms of the halogen i.e., respectively I₂ and Br₂. A simplified reaction scheme explaining the formation of these products is presented and is inserted into a model simulating the chemistry in the marine boundary layer. The modelling effort showed Cl and BrO atoms concentrations up to 5×10⁴ and 1.8×10⁶ molecules cm^-3 respectively, which are comparable to values actually measured in field campaigns.     

The role of bromide and iodide ions in the salinization mapping of the aquifer of Glafkos River basin (northwest Achaia,Greece)

Seawater intrusion causes many problems for groundwater quality, whereas natural remediation is time consuming. However, in cases where groundwater replenishment is feasible, groundwater quality remediation is possible and rapid. The alluvial aquifer in the lowland of the Glafkos River basin, which extends south of Patras city, was for over 30 years the major water source supplying the broader area. Groundwater quality has been degraded due to seawater intrusion, caused by overpumping and generally by inappropriate groundwater management. During the last decade, groundwater quality has been remedied due to diminished groundwater abstractions. The remediation rate was further higher because of rapid discharge of the brackish groundwater, through wells with freely flowing water in the coastal area, where, however, groundwater quality remains low. This paper deals with the hydrogeochemical processes that take place in the area. It is ascertained that ion exchange and mineral dilution processes are dominant. The ion relations between chloride, bromide and iodide, as well as the distribution maps of their concentrations, were used to determine the spatial distribution of the seawater intrusion front. In the lower part of the area in a distance from 1000 and 1500 m from the coast, the rBr^?/rCl^? ratio showed low values (<2·5 × 10^?3) similar to those of seawater. The rI^?/rCl^? ratio also presented low values (<7 × 10^?5), with the lowest one (2·7 × 10^?5) detected along the coastline. In the upper part of the area, a gradual change of those ratios was observed upstream, until they receive values similar to those of the surface waters of Glafkos River. Copyright © 2007 John Wiley & Sons, Ltd.