Quantifying groundwater–surface water interactions in a proglacial valley,Cordillera Blanca,Peru

A myriad of downstream communities and industries rely on streams fed by both groundwater discharge and glacier meltwater draining the Cordillera Blanca, Northern Peruvian Andes, which contains the highest density of glaciers in the tropics. During the dry season, approximately half the discharge in the region's proglacial streams comes from groundwater. However, because of the remote and difficult access to the region, there are few field methods that are effective at the reach scale to identify the spatial distribution of groundwater discharge. An energy balance model, Rhodamine WT dye tracing, and high‐definition kite‐borne imagery were used to determine gross and net groundwater inputs to a 4‐km reach of the Quilcay River in Huascaran National Park, Peru. The HFLUX computer programme ( http://hydrology.syr.edu/hflux.html ) was used to simulate the Quilcay River's energy balance using stream temperature observations, meteorological measurements, and kite‐borne areal photography. Inference from the model indicates 29% of stream discharge at the reach outlet was contributed by groundwater discharge over the study section. Rhodamine WT dye tracing results, coupled with the energy balance, show that approximately 49% of stream water is exchanged (no net gain) with the subsurface as gross gains and losses. The results suggest that gross gains from groundwater are largest in a moraine subreach but because of large gross losses, net gains are larger in the meadow subreaches. These insights into pathways of groundwater–surface water interaction can be applied to improve hydrological modelling in proglacial catchments throughout South America. Copyright © 2016 John Wiley & Sons, Ltd.     

Peat depth as a control on Sphagnum moisture stress during seasonal drought

Peatlands are globally important long-term sinks of carbon, however there is concern that enhanced peat decomposition and moss moisture stress due to climate change mediated drought will reduce moss productivity making these ecosystems vulnerable to carbon loss and associated long-term degradation. Peatlands are resilient to summer drought moss stress because of negative ecohydrological feedbacks that generally maintain a wet peat surface, but where feedbacks may be contingent on peat depth. We tested this ‘survival of the deepest’ hypothesis by examining water table (WT) position, near-surface moisture content, and soil water tension in peatlands that differ in size, peat depth, and catchment area during a summer drought. All shallow sites (<40 cm depth) lost their WT (i.e., the groundwater well was dry) for considerable time during the drought period. Near-surface soil water tension increased dramatically at shallow sites following WT loss, increasing ~5–7.5× greater at shallow sites compared to deep sites (≥40 cm depth). During a mid-summer drought intensive field survey, we found that 60–67% of plots at shallow sites exceeded a 100 mb tension threshold used to infer moss water stress. Unlike the shallow sites, tension typically did not exceed this 100 mb threshold at the deep sites. Using species dependent water content – chlorophyll fluorescence thresholds and relations between volumetric water content and WT depth, Monte Carlo simulations suggest that moss had nearly twice the likelihood of being stressed at shallow sites (0.38 ± 0.24) compared to deep sites (0.22 ± 0.18). This study provides evidence that mosses in shallow peatland may be particularly vulnerable to warmer and drier climates in the future, but where species composition may play an important role. We argue that a critical ‘threshold’ peat depth specific for different hydrogeological and hydroclimatic regions can be used to assess what peatlands are especially vulnerable to climate change mediated drought.     

Impact of soil compaction and irrigation practices on salt dynamics in the presence of a saline shallow groundwater: An experimental and modelling study

Soil salt accumulation is a widespread problem leading to diminished crop yield and threatening food security in many regions of the world. The soil salinization problem is particularly acute in areas that lack adequate soil water drainage and where a saline shallow water table (WT) is present. In this study, we present laboratory-scale column experiments, extending over a period of more than 400 days that focus on the processes contributing to soil salinization. We specifically examine the combined impact of soil compaction, surface water application model and water quality on salt dynamics in the presence of a saline shallow WT. The soil columns (60 cm height and 16 cm diameter) were packed with an agricultural soil with bulk densities of 1.15 and 1.34 g/cm⁻³ for uncompacted and compacted layers, respectively, and automatically monitored for water content, salinity and pressure. Two surface water compositions are considered: fresh (deionized, DI) and saline water (~3.4 mS/cm). To assess the sensitivity of compaction on salt dynamics, the experiments were numerically modelled with the HYDRUS-1D computer program. The results show that the saline WT led to rapid salinization of the soil column due to capillarity, with the salinity reaching levels much higher than that at the WT. However, compaction layer provided a barrier that limited the downwards moisture percolation and solute transport. Furthermore, the numerical simulations showed that the application of freshwater can temporarily reverse the accumulation of salts in agricultural soils. This irrigation strategy can help, in the short-term, alleviate soil salinization problem. The soil hydraulic properties, WT depth, water quality, evaporation demand and the availability of freshwater all play a role in the practicability of such short-term solutions. The presence of a saline shallow WT would, however, rapidly reverse these temporary measures, leading to the recurrence of topsoil salinization.     

Soil water residence times and solute uptake on a dolomite bedrock—preliminary results

Calcium and magnesium levels have been monitored in slope foot drainage waters on a dolomite bedrock. Both calcium and magnesium rich pulses occur. Short term dissolution experiments demonstrate high calcium levels in solution while other authors have suggested that long residence time groundwater has relatively high levels of magnesium due to calcite precipitation. Patterns of field fluctuations in Ca: Mg ratios can thus be tentatively interpreted in terms of short residence time water of high calcium content mixing with long residence time water of high magnesium content. Fluorometric dye tracing has been used to indicate the orders of magnitude of soil water residence times, suggesting that quickflow components are resident in the system for a few hours to a few days. Further work is in progress.     

Measurement of radon potential from soil using a special method of sampling

Soil radon gas and/or its exhalation rate are used as indicators for some applications, such as uranium exploration, indoor radon concentration, seismic activity, location of subsurface faults, etc., and also in the studies where the main interest is the field verification of radon transport models. This work proposes a versatile method for the soil radon sampling using a special manner of pumping. The soil gas is passed through a column of charcoal by using passive pumping. A plastic bottle filled with water is coupled to an activated charcoal column and the flow of water through an adjustable hole made at the bottom of bottle assures a controlled gas flow from the soil. The results obtained for the activity of activated charcoal are in the range of 20–40 kBq/m³, for a depth of approximately 0.8 m. The results obtained by this method were confirmed by simultaneous measurements using LUK 3C device for soil radon measurements. Possible applications for the estimation of radon soil potential are discussed.     

Study of hydrological processes by the combination of environmental tracing and hill slope measurements: application on the Haute‐Mentue catchment

The objective of this research is to improve the comprehension of the hydrological behaviour of natural catchments. The main originality of this work is to associate different types of measurement in order to obtain a better vision of hydrological processes responsible for streamflow generation. First, the hydrological behaviour is studied at the catchment scale by the application of environmental tracing. A three‐component mixing model based on the silica and calcium concentrations of water allows one to distinguish the contributions of direct precipitation, soil water and groundwater during flood generation. Despite the different hydrological responses observed between the four subcatchments studied, a common behaviour is apparent. Soil contribution increases with a rise in the basin humidity. The subsurface water dominates the generation of major floods, which occur in wet conditions. In order to discover the processes responsible for the important soil water contributions, a large‐scale time‐domain reflectometry experiment (64 probes) was conducted. On the whole, this experiment indicates that the water flow in soil is spatially quite heterogeneous and depends on local properties. Macropore flows were clearly identified during a rainfall simulator experiment. Preferential flows may be responsible for the important contribution of soil water and the heterogeneity of the soil moisture. In order to test this hypothesis, a dye‐tracing experiment was done. This new investigation confirms that an important part of soil water reaches the stream by preferential flows. So as to synthesize all these observations, a conceptual model is proposed. This model respects both the hydrochemical responses highlighted by the environmental tracing experiment and the observations done at the local scale. This conceptual model suggests that the important contribution of soil water is due to the extent of the hydrographic network and the role of preferential flows. Copyright © 2005 John Wiley & Sons, Ltd.     

Influence of selected fluorescent dyes on small aquatic organisms

Rhodamine B and Rhodamine WT are fluorescent dyes commonly used as tracers in hydrological investigations. Since introducing intensely red substances into rivers raises understandable doubts of ecological nature, the authors aimed at examining the influence of these dyes on small water fauna using bioindication methods. Quantitative results, calculated with the use of Bliss-Weber probit statistical method, were achieved by means of standardized ecotoxicological tests containing ready-to-hatch resting forms of fairy shrimp (Thamnocephalus platyurus). Qualitative studies included observation of water flea crustacean (Daphnia magna) and horned planorbis snail (Planorbis corneus), both typically present in rivers and representative for temperate climate, as well as guppy fish (Poecilla reticulata), paramecium protozoan (Paramaecium caudatum) and the above-mentioned fairy shrimp. The investigation revealed that both dyes in concentrations used for hydrological purposes are low enough to exert almost no toxic impact on water fauna considered.     

A simple expression for the bulk field capacity of a sloping soil horizon

Field capacity is a commonly used soil parameter in surface water hydrological models, loosely defined as the moisture content of a soil after drainage. The most commonly applied expression for field capacity is defined as the remaining water in a vertical soil column subject to 1/3 atm. of pressure head. While this quantification is sufficient in some cases, the definition is not consistent with the use of bulk field capacity in calculations of lateral drainage from hillslopes, as required by some surface soil parameterizations, nor does it address additional complications arising from differences in soil texture or sample size. Here, a simple alternative expression for bulk field capacity in a sloping or vertical soil is derived directly from Richards equation with the use of the Brooks‐Corey characteristics. It is demonstrated that this expression is consistent with data acquired from vertical soil columns, but may be extended to additional situations commonly found in surface water models and land surface schemes. The calculation of bulk field capacity requires only the Brooks‐Corey pore size distribution index, soil air‐entry pressure, and hillslope length and slope, and may be considered a physically based alternative to pedotransfer function or lookup table approaches. Copyright © 2010 John Wiley & Sons Ltd and Crown in the right of Canada.     

Fluorescence as a Tool for Tracing the Organic Contamination from Pulp Mill Effluents in Surface Waters

Three‐dimensional fluorescence spectra of water samples from an eucalyptus bleached kraft pulp mill and from a river, upstream and downstream of the discharge of the effluent, revealed the existence of a peak at δ_exc = 280 nm and δ_em = 340 nm Δδ = 60 nm), characteristic of effluentπs organic matter. Humic substances were isolated from the effluent by sequential adsorption onto resins XAD‐8 and XAD‐4 in series. Their synchronous fluorescence spectra with Δδ = 60 nm do also exhibit an intense signal at δ_exc = 280 nm (≈ 300 nm in the humic acid fraction). The peak is absent in the spectra of humic substances isolated from a non‐polluted site of the river, but it is clearly seen in the spectra of the humic substances from a site downstream of the discharge of the effluent. Synchronous fluorescence spectra (Δδ = 60 nm) of water samples from the river and its lagoon were recorded and revealed to be an easy and fast way of tracing the organic contamination from the effluent.     

粒子测速技术和透明土在土与结构动力相互作用研究中的应用

为了观测和研究土体内部的变形,人工合成透明土和图像光学技术作为新兴的试验技术成为岩土力学研究的有力手段。根据一系列共振柱/扭剪仪试验测得的人工合成透明土的基本动力特性在某种程度上表现出了与天然土类似的变化规律,可以在动力试验中用来作为天然土的代替品。并介绍了用于土体变形测量的粒子图像测速技术的工作原理和基于神经元网络的像机校正方法。利用两个小型振动台试验,采用透明土和粒子测速技术研究了刚性块体和透明土的动力相互作用。试验表明粒子测速技术和透明土在土与结构动力相互作用中是一个有力的研究工具。     

Use of biliary PAH metabolites as a biomarker of pollution in fish from the Baltic Sea

During field campaigns of the BEEP project (Biological Effects of Environmental Pollution in Marine Coastal Ecosystems) in 2001-2002, metabolites of polycyclic aromatic hydrocarbons (PAHs) were determined in bile samples from three fish species, flounder (Platichthys flesus), perch (Perca fluviatilis) and eelpout (Zoarces viviparus), from four separate areas in the Baltic Sea. Two determination methods were applied: fixed wavelength fluorescence (FF) for pyrene-type metabolites and high-performance liquid chromatography with fluorescence detection (HPLC). There was a good correlation between the FF method and 1-OH pyrene determined by HPLC. Normalisation of the FF data for absorbance at 380 nm or bile protein concentrations greatly increased variance in one third and decreased it in two thirds of the cases and resulted in a loss of significant differences (protein normalisation) between the sampling stations, but normalisation of the HPLC data had little effect on the results. The biliary PAH metabolite content was usually higher in males than in females. In perch and eelpout the biliary PAH contents were at similar levels, whereas in flounder the levels were lower. The sampling areas arranged in decreasing order of biliary PAH contents were: Wismar Bay > Gulf of Gdansk > Lithuanian coast > Kvadofj?rden (reference area). It is concluded that FF with un-normalised data is a reliable and simple method for monitoring purposes and only one sex of a selected species should be used.     

Assessment of evaporation and water fluxes in a column of dry saline soil subject to different water table levels

Dry saline soils are common in the arid and hyper‐arid basins located in the Chilean Altiplano, where evaporation from shallow groundwater is typically the major component of the water balance. Thus, a good understanding of evaporation processes is necessary for improving water resource planning and management in these regions. In this study, we conducted laboratory experiments with a natural saline soil column to estimate evaporation rates and assess the liquid and water vapor fluxes under different water table levels. Water content, electrical conductivity and temperature at different depths were utilized to assess the liquid and water vapor fluxes in the soil column. We observed movement of water that dissolves salts from the soil and transports them to areas in the column where they accumulate. Isothermal liquid flux was predominant, while thermal and isothermal liquid and thermal water vapor fluxes were negligible, except for deep water table levels where isothermal and thermal water vapor fluxes had similar magnitude but opposite directions. Differences observed in total fluxes for all water table levels were due to different upward and downward fluxes, which depend on changes in water content and temperature within the soil profile. Both the vapor flux magnitude and direction were found to be very sensitive to the choice of empirical parameters used in flux quantification, such as tortuosity and the enhancement factor for local temperature gradients in the air phase within the column. Copyright © 2013 John Wiley & Sons, Ltd.     

From soil aggregates to riverine flocs: a laboratory experiment assessing the respective effects of soil type and flow shear stress on particles characteristics

Particles eroded from hillslopes and exported to rivers are recognized to be composite particles of high internal complexity. Their architecture and composition are known to influence their transport behaviour within the water column relative to discrete particles. To‐date, hillslope erosion studies consider aggregates to be stable once they are detached from the soil matrix. However, lowland rivers and estuaries studies often suggest that particle structure and dynamics are controlled by flocculation within the water column. In order to improve the understanding of particle dynamics along the continuum from hillslopes to the lowland river environment, soil particle behaviour was tested under controlled laboratory conditions. Seven flume erosion and deposition experiments, designed to simulate a natural erosive event, and five shear cell experiments were performed using three contrasting materials: two of them were poorly developed and as such can not be considered as soils, whilst the third one was a calcareous brown soil. These experiments revealed that soil aggregates were prone to disaggregation within the water column and that flocculation may affect their size distribution during transport. Large differences in effective particle size were found between soil types during the rising limb of the bed shear stress sequence. Indeed, at the maximum applied bed shear stress, the aggregated particles median diameter was found to be three times larger for the well‐developed soil than for the two others. Differences were smaller in the falling limb, suggesting that soil aggregates underwent structural changes. However, characterization of particles strength parameters showed that these changes did not fully turn soil aggregates into flocs, but rather into hybrid soil aggregate–floc particles. Copyright © 2013 John Wiley & Sons, Ltd.     

Following tracer through the unsaturated zone using a multiple interacting pathways model: Implications from laboratory experiments

Models must effectively represent velocities and celerities if they are to address the old water paradox. Celerity information is recorded indirectly in hydrograph observations, whereas velocity information is more difficult to measure and simulate effectively, requiring additional assumptions and parameters. Velocity information can be obtained from tracer experiments, but we often lack information on the influence of soil properties on tracer mobility. This study features a combined experimental and modelling approach geared towards the evaluation of different structures in the multiple interacting pathways (MIPs) model and validates the representation of velocities with laboratory tracer experiments using an undisturbed soil column. Results indicate that the soil microstructure was modified during the experiment. Soil water velocities were represented using MIPs, testing how the (a) shape of the velocity distribution, (b) transition probability matrices (TPMs), (c) presence of immobile storage, and (d) nonstationary field capacity influence the model's performance. In MIPs, the TPM controls exhanges of water between pathways. In our experiment, MIPs were able to provide a good representation of the pattern of outflow. The results show that the connectedness of the faster pathways is important for controlling the percolation of water and tracer through the soil. The best model performance was obtained with the inclusion of immobile storage, but simulations were poor under the assumption of stationary parameters. The entire experiment was adequately simulated once a time‐variable field capacity parameter was introduced, supporting the need for including the effects of soil microstructure changes observed during the experiment.     

Soil erosion and sediment transport in Tanzania: Part I – sediment source tracing in three neighbouring river catchments

Water bodies in Tanzania are experiencing increased siltation, which is threatening water quality, ecosystem health, and livelihood security in the region. This phenomenon is caused by increasing rates of upstream soil erosion and downstream sediment transport. However, a lack of knowledge on the contributions from different catchment zones, land-use types, and dominant erosion processes, to the transported sediment is undermining the mitigation of soil degradation at the source of the problem. In this context, complementary sediment source tracing techniques were applied in three Tanzanian river systems to further the understanding of the complex dynamics of soil erosion and sediment transport in the region. Analysis of the geochemical and biochemical fingerprints revealed a highly complex and variable soil system that could be grouped in distinct classes. These soil classes were unmixed against riverine sediment fingerprints using the Bayesian MixSIAR model, yielding proportionate source contributions for each catchment. This sediment source tracing indicated that hillslope erosion on the open rangelands and maize croplands in the mid-zone contributed over 75% of the transported sediment load in all three river systems during the sampling time-period. By integrating geochemical and biochemical fingerprints in sediment source tracing techniques, this study demonstrated links between land use, soil erosion and downstream sediment transport in Tanzania. This evidence can guide land managers in designing targeted interventions that safeguard both soil health and water quality.     

Transport of pharmaceutically active compounds in saturated laboratory columns

Occurrences of pharmaceutically active compounds in surface water and sewage water have been widely reported. Investigations show the presence of several classes of pharmaceuticals such as antirheumatics (e.g., diclofenac), analgesics (e.g., propyphenazone), and blood lipid regulators (clofibric acid), even in ground water. Compared to their occurrences in surface water, however, the reported incidences of drugs in ground water are much rarer. This may be due to the input, but also to transport processes and degradation in the aquifer. In field studies investigating ground water sampled at a bank infiltration site at Lake Tegel, Berlin, Germany, clofibric acid was found at concentrations up to 290 ng/L, and propyphenazone up to 250 ng/L, whereas concentrations of diclofenac were around the detection limit. The aim of this study was to investigate the ground water transport behavior of the pharmaceuticals clofibric acid, propyphenazone, and diclofenac with a laboratory soil column experiment. Results show that clofibric acid exhibits no degradation and almost no retardation (Rf = 1.1). Diclofenac (Rf = 2.0) and propyphenazone (Rf = 1.6) are retarded, whereas significant degradation was not observed for both pharmaceuticals under the prevailing conditions in the soil column. We conclude that the concentration distribution of the pharmaceuticals at the bank filtration site at Lake Tegel is controlled by sorption, desorption, and input variation, rather than by degradation.     

High precision tracing of soil and sediment movement using fluorescent tracers at hillslope scale

Generating high resolution spatial information on the movement of sediment in response to soil erosion remains a major research challenge. In this paper we present a new tracing method that utilises LED (light emitting diode) light to induce fluorescence in a sand-sized tracer, which is then detected, using a complementary metal oxide semiconductor (CMOS) sensor in a commercial digital camera, at mm-resolution without the need for removal of soil material. First, we detail two complementary, but independent, methods for quantifying the concentration of tracer from images: particle counting and an intensity based method. We show that both methods can produce highly resolved estimates of particle concentrations under laboratory conditions. Secondly, we demonstrate the power of the method for collecting spatial information on soil redistribution by tillage, with mm precision, over an approximately 50 m hillslope and vertically down the soil profile. Our work demonstrates the potential to collect quantitative time-resolved data about soil movement without disturbing the soil surface which is being studied, and with it the possibility to parameterise or evaluate dynamic distributed soil erosion models or to undertake fundamental research focused on particle movement that has been impossible to conduct previously. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

Solid‐Phase Removal of Dissolved Organic Species from Water and Identification by GC–MS

A method is described for the detection and identification of dissolved organic compounds (DOCs) in various water samples. Acid treated active silica gel sorbent (pH 3) was packed into a micro‐column and used as a solid‐phase extraction medium for adsorption of DOCs. Silica particles‐adsorbed‐organic species were then divided into equal portions followed by suspension into various organic solvents of different polarities such as methanol, acetone, ethyl acetate, and toluene. Suspended silica‐adsorbed‐organic species were shaken for 1 h at room temperature and the organic extracts were subjected to GC–MS analysis under temperature programming conditions for qualitative detection and identification of these species. Blank solvents and silica samples were also subjected to the same extraction procedures and GC–MS analysis for comparison. The mass spectrum of each eluted chromatographic peak was library searched or manually interpreted to identify the compound.     

Removal of Copper,Nickel, and Zinc Ions from Electroplating Rinse Water

Removal of copper, nickel, and zinc ions from synthetic electroplating rinse water was investigated using cationic exchange resin (Ceralite IR 120). Batch ion exchange studies were carried out to optimize the various experimental parameters (such as contact time, pH, and dosage). Influence of co‐existing cations, chelating agent EDTA on the removal of metal ion of interest was also studied. Sorption isotherm data obtained at different experimental conditions were fitted with Langmuir, Freundlich, Redlich–Peterson, and Toth models. A maximum adsorption capacity of 164 mg g^?1 for Cu(II), 109 mg g^?1 for Ni(II), and 105 mg g^?1 for Zn(II) was observed at optimum experimental conditions according to Langmuir model. The kinetic data for metal ions adsorption process follows pseudo second‐order. Presence of EDTA and co‐ions markedly alters the metal ion removal. Continuous column ion exchange experiments were also conducted. The breakeven point of the column was obtained after recovering effectively several liters of rinse water. The treated rinse water could be recycled in rinsing operations. The Thomas and Adams–Bohart models were applied to column studies and the constants were evaluated. Desorption of the adsorbed metal ions from the resin column was studied by conducting a model experiments with Cu(II) ions loaded ion exchange resin column using sulfuric acid as eluant. A novel lead oxide coated Ti substrate dimensionally stable (DSA) anode was prepared for recovery of copper ions as metal foil from regenerated liquor by electro winning at different current densities (50–300 A cm^?2).     

基于声波方程的井间地震数据快速WTW反演方法

WTW(Wave equation traveltime+Waveform inversion)反演是基于波动方程的走时反演（WT反演）和波形反演的联合反演方法.WT反演利用波动方程计算走时和走时关于速度的导数，和传统以射线为基础的走时反演相比，具有不必射线追踪、不必拾取初至、不必高频假设以及初始模型和实际模型差别较大时也能较好收敛等优点，但WT反演与波形反演相比其结果分辨率低.与之互补的是，波形反演的反演结果分辨率高，但是当所给初始模型和实际模型相差太大时，波形反演迭代算法容易陷入局部极小点.可见结合两种方法的WTW反演是一种比较好的联合反演方法.常规WTW迭代算法是首先以WT反演为主反演得到地质模型的整体特征，然后再以波形反演为主反演模型细节，该算法耗时和占用计算机存储空间接近WT反演或波形反演的两倍.为了节省运算耗时和计算机存储空间，往往采取首先单独利用WT反演然后再单独利用波形反演的算法.这样做的缺点是不能紧密结合两种反演方法，使得它们的优缺点在每一次迭代中无法得到互补，从而影响了最终的反演结果.针对以上事实，本文提出一种新的方法实现WTW，使得WTW运算速度和存储空间在任何情况下等同于WT反演或波形反演.模型计算表明新的算法具有更好的收敛性.