Interconnectivity between the Superficial Aquifer and the Deep Confined Aquifers of the Gnangara Mound, Western Australia

Perth groundwater resources are obtained from three major aquifers that occur beneath the Perth metropolitan area: the Superficial aquifer, Leederville aquifer and Yarragadee aquifer. Each aquifer has a unique seasonal water level pattern controlled by soils, geomorphology and geology. Landuse is mainly responsible for variations in recharge; however, the hydraulic properties control aquifer response and water level pattern to a greater degree. Groundwater in the three aquifers is generally of very good quality except in localised areas. Salinity increases with depth and in direction of groundwater flow in the three aquifers. The best water quality is in the Superficial aquifer in the Wanneroo well field area. The geochemistry and stable isotope signatures from the three major aquifers revealed distinct water types that suggest very little hydraulic connection or mixing of waters between these aquifers at the present abstraction and recharge regimes. The results also show that the Leederville and Yarragadee aquifers were recharged during earlier cooler times while the Superficial aquifer is being recharged at present.     

Integration of the Pesticide Impact Rating Index with a Geographic Information System for the Assessment of Pesticide Impact on Water Quality

The pesticide impact rating index (PIRI) has been integrated with a Geographic Information System (GIS) to enable regional assessment of pesticide impact on groundwater and surface water resources. The GIS version of PIRI (PIRI-GIS) was used to assess the impact of pre-planting atrazine use in the pine plantations on the Gnangara Mound, Western Australia. The impact on groundwater was found to be spatially variable, mainly dependent on soil type and depth to groundwater, because land use variables were spatially constant. Areas with the greatest impact on groundwater were those where the soil had a low sorption capacity for atrazine. Knowledge of the spatial distribution of the sorption coefficient based on organic carbon (K _oc) for atrazine was found to significantly improve the results from PIRI-GIS. Average values for K _oc (i.e. based on overseas data) were too low for most of the local soil types, resulting in a general overestimation of pesticide impact on groundwater resources, but an underestimation of impact in areas that should be of greatest concern (i.e. where the soil has a low sorption capacity for atrazine).     

Changes in soil characteristics during landfill leachate irrigation of Populus deltoides

The effects of wastewater application on electrical conductivity, water retention and water repellency of soils planted with Populus deltoides (eastern cottonwood) and irrigated with different concentrations of landfill leachate and compost wastewater, tap water and nutrient solution were evaluated. Substrate water content at field capacity (?0.033 MPa) and at permanent wilting point (?1.5 MPa) was determined with a pressure plate extractor to assess available water capacity of the substrate. A water drop penetration test was used to determine substrate water repellency. The biomass of nutrient and landfill leachate treatments was significantly (P < 0.05) greater compared to the tap water and compost wastewater treatments. All treatments increased substrate water content at field capacity and at permanent wilting point. Landfill leachate significantly increased available water capacity (up to 52%); treatment with compost wastewater significantly decreased it (25–47%). All substrates showed increased water repellency after the experiment at field capacity and permanent wilting point comparing to the original substrate. The strongest influence on water repellency at both field capacity and permanent wilting point showed irrigation with compost wastewater and tap water. Pronounced influence on substrate’s water repellency of compost wastewater could be contributed to a high content of dissolved organic carbon, whereas Mg and Ca cations caused flocculation and consequent water repellency of the substrate irrigated with tap water. The results indicate that soil physical characteristics must be closely monitored when landfill leachate and compost wastewater are used for irrigation to avoid long term detrimental effects on the soil, and consequently on the environment. Due to the complexity of the compost wastewater quality the latter should be applied on open fields only after prior pre-treatment to reduce dissolved organic carbons, or alternatively, compost wastewater should be added only intermittently and in diluted ratios.     

Preferential flow in municipal solid waste and implications for long-term leachate quality: valuation of laboratory-scale experiments.

In this paper, we study and quantify pollutant concentrations after long-term leaching at relatively low flow rates and residual concentrations after heavy flushing of a 0.14 m3 municipal solid waste sample. Moreover, water flow and solute transport through preferential flow paths are studied by model interpretation of experimental break-through curves (BTCs), generated by tracer tests. In the study it was found that high concentrations of chloride remain after several pore volumes of water have percolated through the waste sample. The residual concentration was found to be considerably higher than can be predicted by degradation models. For model interpretations of the experimental BTCs, two probabilistic model approaches were applied, the transfer function model and the Lagrangian transport formulation. The experimental BTCs indicated the presence of preferential flow through the waste mass and the model interpretation of the BTCs suggested that between 19 and 41% of the total water content participated in the transport of solute through preferential flow paths. In the study, the occurrence of preferential flow was found to be dependent on the flow rate in the sense that a high flow rate enhances the preferential flow. However, to fully quantify the possible dependence between flow rate and preferential flow, experiments on a broader range of experimental conditions are suggested. The chloride washout curve obtained over the 4-year study period shows that as a consequence of the water flow in favoured flow paths, bypassing other parts of the solid waste body, the leachate quality may reflect only the flow paths and their surroundings. The results in this study thus show that in order to improve long-term prediction of the leachate quality and quantity the magnitude of the preferential water flow through a landfill must be taken into account.     

Leachate migration from spent mushroom substrate through intact and repacked subsurface soil columns

Field weathering of spent mushroom substrate (SMS) produces soluble compost leachate that percolates into underlying soils and may adversely impact groundwater. Laboratory experiments were conducted to investigate movement and retention of SMS leachate solutes in subsurface soil columns. Spent mushroom substrate leachate with high concentrations of dissolved organic matter (DOM) and inorganic salts was passively loaded to intact and repacked columns of Bt1 soil (fine-loamy, mixed, semiactive, mesic Typic Hapludults) and effluents were monitored for changes in chemical composition. Transport of SMS leachate in undisturbed soil cores was mainly via preferential flow, whereas matrix flow was predominant in repacked soil columns. Leachate DOM and phosphate were sorbed by soil minerals while Cl-, SO4(2-), Na+ and NH4+ were eluted. Leachate K+ displaced exchangeable native cations and was retained. Biodegradation of leachate DOM resulted in reduction and elution of soil Mn and Fe, especially in repacked columns. Persistent anoxia also inhibited nitrification. Precipitation of gypsum and CaCO3 blocked preferential flow channels, and movement of SMS leachate was subsequently reduced. The results demonstrate that SMS leachate migrates via rapid preferential flow initially, followed by matrix flow at a lower rate. Leachate solutes may transport to depth in soil profiles through preferential channels. To protect water resources, weathering of deep SMS piles should be conducted on compact surfaces or in fields with a condensed soil layer (no structural cracks) above the groundwater table, and measures controlling leachate runoff be imposed.     

Hydrogeomorphological Controls on Groundwater Quality in the Rattaphum Catchment (Songkhla Lake Basin), Thailand

The Rattaphum Catchment comprises four major hydrogeomorphic units: mountains, footslopes, plains and inland swamps around a lake system. The area accommodates three main agro-ecosystems: vegetable, rubber and fruits. During the high-rainfall period, groundwater levels rise near to the soil surface in all agro-ecosystems. The high water levels remain for 3–4 months in the coastal plain, while in other areas the groundwater level fluctuates according to the intensity of rainfall events during the 2–3 months of the rainy season. Groundwater salinity is higher near Songkhla Lake and decreases rapidly inland. It is generally lower near streams. Salinity is also lower during periods of higher recharge, increasing slightly during the dry season due to leaching of chemicals from the agricultural areas. In the saturated sandy soils with high hydraulic conductivity and in the vegetable agro-ecosystem areas with high water levels, the NO₃ level in groundwater always exceeds the WHO standard. Variations in NO₃ levels are closely related to patterns of landuse, with higher nitrate levels commonly found in vegetable areas and lower levels associated with fruit and rubber tree plantations. Nearly all groundwater and surface water is contaminated by coliform bacteria, with the level of contamination controlled by groundwater levels, the amount of rainfall and farm activities. Vegetable agro-ecosystems, which have the most intensive cropping system, were found to be the most polluted. In all of the agro-ecosystems, the most polluted period coincided with the first series of rainfall events.     

In-situ bioremediation of an aquifer contaminated with 1,2-dichloroethane

This article describes the application of in-situ bioremediation for the treatment of an aquifer contaminated with 1,2-dichloroethane (DCA). The first step in the process was to properly delineate the contamination and to contain the contaminated groundwater using a pumping well. The second step was to isolate in the groundwater microorganisms able to degrade DCA and to demonstrate the possibility of increasing their efficiency by injecting in-situ nutrients and hydrogen peroxide (H₂O₂) solution. In the third step, after the characterization of the hydrogeology of the aquifer with tracing experiments, the in-situ bioremediation of the groundwater was conducted. The analyses show that 95 percent of DCA was destroyed by this treatment, leading to a DCA concentration around the pumping well of about 0.2 mg/l.     

Controls on leaching of N species in upland moorland catchments

Spatial and temporal changes in mobility of N species have been studied for three UK upland river networks, the Etherow in the South Pennines, the Nether Beck in the Lake District and the Dee in NE Scotland. The catchments are subject to N deposition at 35.1, 22.0 and 10.8–15.6 kg N ha^?1 yr^?1, respectively. The NH⁺ ₄ leaching appears to be predominantly regulated by flow path in more polluted upland catchments. It is greatest where water draining acidified peaty soils contributes more to total discharge. Soluble organic matter may provide the dominant counter anion. In the Etherow and Dee catchments, which are dominated by acid mineral and organic soils, at high discharge NO^? ₃ also appears to be associated with greater input of water from acidified soils. In contrast, for the Nether Beck, higher NO^? ₃ concentrations are associated with tributaries draining soils contributing water with higher alkalinity, suggesting nitrification is important. For the Etherow and Dee, dissolved organic N (DON) appears to originate predominantly from acidified, peaty soils. Spiking experiments with peat soil from the Etherow catchment confirmed the limited capacity of these soils to utilize inorganic N inputs, favouring equilibration with NH⁺ ₄ inputs and leaching losses of inorganic N throughout the year.     

Field Performance of Point Velocity Probes at a Tidally Influenced Site

Conventional methods to estimate groundwater velocity that rely on Darcy's Law and average hydrogeologic parameter values are insensitive to local‐scale heterogeneities and anisotropy that control advective flow velocity and direction. Furthermore, at sites that are tidally influenced or have extraction wells with variable pumping schedules, infrequent water‐level measurements may not adequately characterize the range and significance of transient hydraulic conditions. The point velocity probe (PVP) is a recently developed instrument capable of directly measuring local‐scale groundwater flow velocity and direction. In particular, PVPs may offer distinct advantages for sites with complex groundwater–surface water interactions and/or with spatially and temporally variable groundwater flow conditions. The PVP utilizes a small volume of saline tracer and inexpensive sensors to directly measure groundwater flow direction and velocity in situ at the centimeter‐scale and discrete times. The probes are installed in conventional direct‐push borings, rather than in wells, thus minimizing the changes and biases in the local flow field caused by well installation and construction. Six PVPs were installed at a tidally influenced site in North Carolina to evaluate their implementability, performance, and potential value as a new site characterization tool. For this study, a new PVP prototype was developed using a rapid prototyping machine (i.e., a “three‐dimensional printer'') and included both horizontally and vertically oriented tracer detectors. A site‐specific testing protocol was developed to account for the spatially and temporally variable hydraulic conditions and groundwater salinity. The PVPs were tested multiple times, and the results were compared to the results of several different groundwater flux and velocity estimation tools and methods, including a heat‐pulse flowmeter, passive flux meters, single‐well tracer tests, and high‐resolution hydraulic gradient analysis. Overall, the results confirmed that the PVP concept is valid and demonstrated that reliable estimates of groundwater velocity and direction can be obtained in simple settings. Also, PVPs can be successfully installed by conventional methods at sites where the formation consists primarily of noncohesive soils and the water table is relatively shallow. Although some PVP tests yielded consistent and reliable results, several tests did not. This is likely due to the highly transient flow conditions and limitations associated with the PVP design and testing procedures. PVPs offer particular advantages over, and can effectively complement, other groundwater flow characterization techniques for certain conditions, and objectives may be useful for characterizing complex flow patterns under steady conditions; however, this study suggests that PVPs are best suited for conditions where the flow hydraulics are not highly transient. For sites where the hydraulic conditions are highly transient, the most reliable approach for understanding groundwater flow behavior and groundwater–surface water interactions would generally involve both a high‐resolution hydraulic gradient analysis and another local‐scale method, such as tracer testing. This study also highlighted some aspects of the current PVP design and testing protocol that can be improved upon, including a more robust connection between the PVP and injection line and further assessment of tracer solution density effects on vertical flow. © 2013 Wiley Periodicals, Inc.     

The UN/ECE International Programme on Mapping Critical Loads and Levels

Critical Loads and levels have played a centralrole in the successful development of effect-based emissionreduction strategies for Europe in the fields of acidification,eutrophication and ground-level ozone. The aim of theInternational Programme on Mapping Critical Loads and Levelsled by Germany, with participation of 24 countries, is todetermine critical loads and levels for forest, crops, naturalvegetation, soils, water and materials. The exceedances ofcritical loads and critical levels are used to quantify the riskfor environmental damage by air pollution and tosupport the development of optimised abatement strategies.     

A Preliminary Laboratory Study of Initial Copper Release from Dredge Residuals

A preliminary laboratory study was conducted to investigate the impact of different residual types and sediment surface roughness on copper contaminant fluxes to the water column. Sediments from Torch Lake, Michigan served as the test samples. These sediments are mining by‐products with elevated Cu levels. Six experiments were run during which the sediments were conditioned to simulate different forms of residuals. During these experiments, the water column above the sediments was circulated via peristaltic pumping or orbital shaking and the total and dissolved Cu levels were monitored periodically for 15 days. Dissolved Cu levels indicated that during the first 48 hr the water column concentrations approached equilibrium for all six cases. Total Cu levels increased with time and did reach equilibrium but were more susceptible to fluctuations in water column suspended solids levels. Analysis of the resulting dissolved Cu data indicated that the resulting water column Cu concentrations differed with sediment surface and residual type. The highest dissolved Cu water column concentrations were observed for a roughened surface with a larger surface area. The lowest water column dissolved Cu levels were observed for the case with sediment slurry placed over clean sand. The dissolved Cu levels in the water column for all six simulated conditions were several orders higher than the USEPA ambient water quality criteria for protection of aquatic life. © 2014 Wiley Periodicals, Inc.*     

Mineralization and Transfer Processes of <Superscript>14</Superscript>C-labeled Pesticides in Outdoor Lysimeters

A recently designed two-chamber-lysimeter-test-system allows the detailed investigation of degradation, transport and transfer processes of ¹⁴C-labeled substances in soil–plant–atmosphere-systems under outdoor conditions. With this test system it is feasible to distinguish between ¹⁴C-emissions from soil surfaces and ¹⁴C-emissions from plant surfaces in soil monoliths under real environmental conditions. Special soil humidity sensors allow the measurement of soil water content near to the soil surface, in 1 and 5 cm depth. The behavior of organic chemicals can be followed for a whole vegetation period and a mass balance for the applied chemical can be established. Some selected results of the herbicides isoproturon and glyphosate – using the two-chamber-lysimeter-test-system – are presented to demonstrate its applicability for the identification and quantification of the processes that govern pesticide behavior in soil–plant-systems. Mineralization of ¹⁴C-isoproturon was very different in four different soils; the mineralization capacity of the soils ranged from 2 to 60%. Leaching of isoproturon in general was very low, but depending on the soil type and environmental conditions isoproturon and its metabolites could be leached via preferential flow, especially shortly after application. For the herbicide ¹⁴C-glyphosate no accumulation of residues in the soil and no leaching of the residues to deeper soil layers could be observed after three applications. Glyphosate was rapidly degraded to AMPA in the soil. Glyphosate and AMPA were accumulated in soy bean nodules.     

Two granular-activated carbons for adsorbing army explosives

Explosives-contaminated groundwater percolating from storage ponds at the Milan Army Ammunition Plant (MAAP) in Milan, Tennessee, into the Claiborne aquifer threatens to contaminate more groundwater—and possibly surface water—in the area. The research described in this article sought to determine whether granular-activated carbon (GAC) could help remove the explosives from the water and to identify which carbons can adsorb the most TNT, RDX, HMX, Tetryl, and others. Two carbons—Atochem, Inc. GAC 830 and Calgon Filtrasorb 300—were found to be promising candidates. As for what to do with the explosives that would be adsorbed, as well as the contaminated carbon, stay tuned.     

Integrated bioremediation of soil and groundwater at a superfund site

The soil and two aquifers under an active lumber mill in Libby, Montana, had been contaminated from 1946 to 1969 by uncontrolled releases of creosote and pentachlorophenol (PCP). In 1983, because the contaminated surface soil and the shallower aquifer posed immediate risks to human health and the natural environment, the U.S. Environmental Protection Agency placed the site on its National Priorities List. Feasibility studies in 1987 and 1988 determined that in situ bioremediation would help clean up this aquifer and that biological treatment would help clean up the contaminated soils. This article outlines the studies that led to a 1988 EPA record of decision and details the EPA-approved remedial plan implemented starting in 1989; EPA estimates a total cost of about $15 million (in 1988 dollars). The plan involves extensive excavation and biological treatment of shallow contaminated soils in two lined and bermed land treatment units, extraction of heavily contaminated groundwater, an aboveground bioreactor treatment system, and injection of oxygenated water to the contaminant source area, as well as to other on-site areas affected by the shallower aquifer's contaminant plume.     

Investigation of naphtalene sulfonate compounds sorption in a soil artificially contaminated using batch and column assays

In the present work desorption tests of an artificially contaminated soil by naphatelene sulphonated compounds have been carried out by soil washing realised by water at different pH: Naphtalene-1,5-disulfonic acid (1-5 NDS), 2-naphthol-6,8 disulphonic acid (G-acid) and sodium beta-naphtalene-sulphonate (beta-salt) have been selected as more representative organic compounds present in the ex industrial site of ACNA (Cengio, SV, Italy) in which very serious contamination levels of several pollutants are present both in the soils and surface waters. Equilibrium batch tests have been carried out in order to find the best operative condition in column washing tests. The obtained results can be considered very preliminary but useful to arrange a next experimental work that will be realised on real contaminated soils.     

Electroremediation: A study of the influence of buffering behavior in contaminated soils

This article presents the results of an experimental study conducted to evaluate the behavior of two types of andisol soils found in Tenerife, Canary Islands, Spain. The soils were evaluated in relation to their buffering capacity when confronted with acid and alkaline fronts generated during electroremediation treatment. The study was conducted using a cell, which established a continuous flow of distilled water through electrode chambers to remove H⁺ and OH^? generated during electrolysis. The results indicate that the soils had sufficient buffer capacity to support variations in pH independent of the maintenance of flow of solution in the electrode chambers. Although the mechanism of migration was not affected, the flow of water favored the movement of ions by diffusion monitoring of the electrolytic current allowed for a real‐time parameter to act as an indicator of the quantity of ions available in regions near the electrodes. © 2004 Wiley Periodicals, Inc.     

A steady-state approach for evaluating the impact of solute transport through composite liners on groundwater quality

New adaptations of analytical equations for predicting the impact of solute transport through composite landfill liners on groundwater quality for steady-state conditions are presented. Analytical equations are developed for evaluating average concentration and mass flow rate in an underlying aquifer resulting from diffusion of volatile organic compounds (VOCs) through intact composite liners and transport of inorganic constituents through defects in composite liners. The equations are applied to evaluate the effectiveness and equivalency of composite liners having either a 0.6 m-thick compacted soil liner or a 6.5 mm-thick geosynthetic clay liner (GCL) overlying an intermediate attenuation layer and an aquifer having horizontal flow. Example analyses for designing composite liners meeting particular performance criteria are also provided. The analytical equations are relatively simple to apply and can be used for preliminary design and analysis, to evaluate experimental results, and to possibly verify more complex numerical models for evaluating the impact of landfills on groundwater quality if consistency of the assumptions of the analytical equations and the more complex numerical models can be specified.     

The influence of soil composition on bioremediation of PAH-contaminated soils

As a result of former industrial activities, many properties across the United States contain various chemicals in their soils at concentrations above background levels. Polynuclear aromatic hydrocarbons (PAHs) are often encountered at sites of gas manufacture, wood treating, tar refining, coke making, and petroleum reflning. When the presence of PAHs in site soil is deemed to create a situation of unacceptable risk to public health or the environment, treatment or disposal is required to reduce concentrations to acceptable levels. The ideal remedial process for PAHs in soils would destroy them to an environmentally sound level at relatively low cost without producing adverse by-products. In many cases bioremediation can accomplish these goals. The degree to which bioremediation can destroy PAHs in a particular soil, however, is highly dependent on the characteristics of that soil, including the nature of the hydrocarbon that is the source of the PAHs. It is the objective of this article to describe efforts leading to this conclusion and to summarize how soil characteristics influence bioremediation of PAHs.     

An attempt to perform water balance in a Brazilian municipal solid waste landfill

This paper presents an attempt to model the water balance in the metropolitan center landfill (MCL) in Salvador, Brazil. Aspects such as the municipal solid waste (MSW) initial water content, mass loss due to decomposition, MSW liquid expelling due to compression and those related to weather conditions, such as the amount of rainfall and evaporation are considered. Superficial flow and infiltration were modeled considering the waste and the hydraulic characteristics (permeability and soil-water retention curves) of the cover layer and simplified uni-dimensional empirical models. In order to validate the modeling procedure, data from one cell at the landfill were used. Monthly waste entry, volume of collected leachate and leachate level inside the cell were monitored. Water balance equations and the compressibility of the MSW were used to calculate the amount of leachate stored in the cell and the corresponding leachate level. Measured and calculated values of the leachate level inside the cell were similar and the model was able to capture the main trends of the water balance behavior during the cell operational period.     

喀斯特山区燃煤电厂土壤重金属污染评价

选取地处贵州省喀斯特山区的金沙电厂为研究对象,对电厂周围的表层土壤、蔬菜(莲花白)试样的重金属含量进行了测定,采用模糊数学法对土壤重金属污染进行了评价,采用富集系数法分析了莲花白对重金属的富集能力。实验结果表明:电厂周围表层土壤中Hg,As,Cd,Pb,Cu的平均含量分别达0.70,26.40,0.61,44.83,35.51 mg/kg,其中,Hg和Cd的平均含量分别为GB 15618—1995《土壤环境质量标准》中二级标准的1.40和2.03倍;电厂周围土壤受到较为严重的Hg,As,Cd污染,各个方向的重金属污染程度大小顺序为西北西东南西南东北东,总体趋势为西向大于东向;莲花白对土壤中Cd的富集作用较强,对其他重金属的富集作用较弱。