Lysimeter Types Research Articles

Lysimeter Sampling System for Optimal Determination of Trace Elements in Soil Solutions

Understanding trace element (TE) composition and behavior in soil solution is extremely important for assessing ecological and human health impacts. Using lysimeters to collect soil solution with minimum alteration to the in situ phase distribution and concentration of TEs will facilitate a more accurate assessment. However, different lysimeter materials and sampling conditions may lead to vastly different results, demonstrating the need for the optimal choice of lysimeter depending upon environmental conditions. There is no general agreement or overview discussing the best lysimeter type and sampling system to use under various conditions. This review provides a critical summary of various lysimeters that can be used to collect soil solutions for the analysis of TEs and thereby provides key guidance for developing the best lysimeter sampling system for conditions and research questions of interest. This includes a range of aspects related to lysimeters, such as different types and materials, the basic principles of design and operation, advantages and disadvantages, challenges and limitations, techniques for cleaning and pretreatment, correct installation procedures, the influence of soil physical and chemical properties on sampling, and existing research gaps within this field.

Soil Solution Analysis With Untargeted GC–MS—A Case Study With Different Lysimeter Types

Surface-sourced organic compounds in infiltrating waters and percolates are transformed during their belowground passage. Biotic and abiotic processes thereby lead to continuously changing chemical environments in subsurface compartments. The investigation of such transformations of organic compounds aims for tracing subsurface fluxes as well as biotic and abiotic activity. To collect samples of soil solution, different kinds of lysimeters are available, spanning simple free-draining devices that sample water based on gravimetric flow and tension lysimeters allowing for approximating natural hydraulic conditions. Protocols for untargeted analytical profiling of organic soil solution constituents are scarce. We report here a solid phase extraction followed by GC–MS analysis, utilizing two long-term sampling devices in the Hainich Critical Zone Exploratory in Thuringia, Germany. In addition, we introduce a new lysimeter constructed exclusively from inert materials that allows for obtaining samples with little background signals in GC–MS. Polyvinylchloride (PVC)-based lysimeters introduce substantial background signals from plasticizers. We show how signals from these contaminants can be lowered during data analysis using chemometric background removal. Applying multivariate statistics for data analysis, we demonstrate the ability for monitoring of several sugars, fatty acids and phenolic acids at the topsoil-subsoil boundary and even beyond, via an untargeted analytical approach. Statistical tools facilitated the detection of differences in chemical signatures at three different land use sites. Data mining methods for metabolomics led to the identification of 3-carboxyphenylalanin as marker for a pasture site. The combined approach is suitable for the collection and extraction of topsoil and subsoil solution for untargeted metabolomics under near-natural flow conditions.

An overview of the experimental research use of lysimeters

Abstract The lysimeter is most often defined as a box filled with soil with an intact structure for measuring the amount of infiltration and evapotranspiration in natural conditions. At the bottom of the device there is an outflow for atmospheric precipitation water infiltrating to a measuring container. Lysimeter studies are included in the group of dynamic leaching tests in which the leaching solution is added in a specified volume over a specific period of time. Lysimeter studies find applications in, amongst others, agrotechnics, hydrogeology and geochemistry. Lysimeter tests may vary in terms of the type of soil used (anthropogenic soil, natural soil), sample size, leaching solution, duration of the research and the purpose for conducting it. Lysimeter experiments provide more accurate results for leaching tests compared with static leaching tests. Unlike several-day tests, they should last for at least a year. There are about 2,500 lysimeters installed in nearly 200 stations around Europe. The vast majority of these (84%) are non-weighing lysimeters. There are a few challenges for lysimeter research mostly connected with the construction of the lysimeter, estimating leaching results and calibrating numerical transport models with data obtained from lysimeters. This review is devoted to the analysis of the principal types of lysimeters described in the literature within the context of their application. The aim of this study is to highlight the role of lysimeters in leaching studies.

Predictive Evapotranspiration Equations in Rain Gardens

Current stormwater control measure (SCM) design often does not include the dynamic process of evapotranspiration (ET) for vegetated systems. This study compared two reference ET equations with a three-year data set from rain garden weighing lysimeters. The outcome was a tool to incorporate ET into SCM design. The weighing lysimeters at Villanova University, located in southeastern Pennsylvania, were used to measure water budget parameters for three scenarios: sandy loam with UO, sand with an unconstricted outflow (UO), and sand with internal water storage (IWS). The two ET models explored were the ASCE Penman-Monteith equation (a robust model) and the Hargreaves equation (a simple model). Estimated ET values from these two equations, both with and without modifications for water availability and crop presence, were compared and calibrated (if modified) with observed data. Comparisons and calibrations were performed on a daily and storm basis to explore the applicability of the two ET models for continuous and storm approaches. The observed ET was 28%–52% of inflow over the continuous three-year period and 16–30 mm on a storm scale, making ET a significant part of the lysimeters’ water budget. Due to the experimental nature of the lysimeters, 12 of the 36 study months had additional simulated runoff, such that a smaller ET as a percentage of inflow was expected in the rain garden SCM’s water balance. The Hargreaves and ASCE Penman-Monteith equations without modification provided an adequate estimate for rain garden ET for all systems at the storm scale. Modifications to ET estimations produced by both equations through crop coefficients and a soil moisture extraction function provided a good model for storm-scale ET by reducing errors and increasing efficiencies for all weighing lysimeter types. Evapotranspiration estimates from both unmodified equations provided, at best, a marginally better estimate than the average observed rate for continuous daily rain garden ET. The application of crop coefficients and a soil moisture extraction function to both equations reduced errors in ET estimates and increased the equations’ predictive power (Nash-Sutcliffe efficiency) for all weighing lysimeter types. Both equations with modifications on a daily scale produced good ET estimates for the IWS system. For both equations, crop coefficients were found in an expected range for UO systems (0.3–1.5) but were high in the IWS system (1.6–2.0). Soil moisture extraction functions were not needed to calibrate the IWS equations on the storm scale. Both the Hargreaves equation and the ASCE Penman-Monteith equation provided an adequate model (especially with modifications) to incorporate ET into a design-storm approach to SCM design. Use of both predictive models on a daily scale has potential use in continuous simulation, as in most cases the ET estimations predicted by the equations provided a better estimate than the average of the observed daily ET rates.

New Comparative Experiments of Different Soil Types for Farmland Water Conservation in Arid Regions

Irrigated farmland is the main food source of desert areas, and moisture is the main limiting factor of desert farmland crop productivity. Study on the influence of irrigation on desert farmland soil moisture can guide the agricultural water resource utilization and agricultural production in those regions. At present, the efficiency of irrigation water usage in Northwest China is as low as approximately 40% of the irrigated water. To understand the response of farmland soil moisture in different soil types on irrigation in the Ulan Buh Desert of Inner Mongolia of China, this experimental study takes advantage of different infiltration characteristics and hydraulic conductivities of sand, clay, and loam to determine an optimized soil combination scheme with the purpose of establishing a hydraulic barrier that reduces infiltration. This study includes three comparative experiments with each consisting of a 100 cm thick of filled sand, or clay, or loam soil underneath a 50 cm plough soil, with a total thickness of 150 cm soil profile. A new type of lysimeter is installed below the above-mentioned 150 cm soil profile to continuously measure deep soil recharge (DSR), and the ECH2O-5 soil moisture sensors are installed at different depths over the 150 cm soil profile to simultaneously monitor the soil moisture above the lysimeter. The study analyzes the characteristics of soil moisture dynamics, the irrigation-related recharge on soil moisture, and the DSR characteristics before and after irrigation, during the early sowing period from 2 April to 2 May 2017. Research results show that: (1) Irrigation significantly influences the soil moisture of 0–150 cm depths. The soil moisture increase after the irrigation follows the order from high to low when it is in the order of loam, sand, and clay. (2) Irrigation-induced soil moisture recharge occurs on all three soil combinations at 0–150 cm layers, and the order of soil moisture recharge from high to low is: clay (54.3 mm, 43.39% of the total irrigation), loam (39.83 mm, 31.83% of the total irrigation), and sand (33.47 mm, 26.75% of the total irrigation). (3) After the irrigation event, DSR below 150 cm occurs for all three soil combinations. This study reveals the characteristics of irrigation-induced soil moisture recharge and DSR, and it shows that farmland consisting of an upper 50 cm plough soil and a lower 100 cm filled clay soil can save more water resource at the study site, which is useful in agricultural control measure and water resource management in arid regions.

Study of deep percolation in paddy fields using drainage-type lysimeters under varying regimes of water application

Deep percolation in water-intensive paddy rice crop field is a major outflow and needs due attention. In this paper, field observation of deep percolation in paddy fields under varying regimes of water application has been presented. Large portion of input water is lost due to deep percolation as observed from drainage-type lysimeters and verified using physically based model. More than 80% of the input water was lost through deep percolation during continuous irrigation season, while approximately 75–80% of the input water was lost due to deep percolation during the intermittent application of irrigation season. This would be attributed to soil texture, experimental field condition and the mode of input water. The physically based model has been calibrated and validated using field-observed deep percolation. A good agreement between model simulations and field-observed deep percolation was obtained. Further, field-observed and model-simulated soil moisture content values at respective crop periods showed fairly good agreement. This shows the significance of locally constructed drainage-type lysimeters in capturing deep percolation below a crop root zone. These types of lysimeters are easy to construct, maintain, simple to operate and thus can play a significant role in agricultural water management.

A long-term lysimeter experiment to investigate the environmental dispersion of the herbicide chloridazon and its metabolites—comparison of lysimeter types

In order to investigate the long-term fate of the herbicide chloridazon and its polar metabolites desphenyl-chloridazon and methyl-desphenyl-chloridazon, a lysimeter experiment was conducted. The plant protection product Pyramin WG, which contains chloridazon, was applied to a weighable, monolithic lysimeter and a backfilled, gravitation lysimeter. Leachate, soil and maize samples were analyzed, and the data from the monolithic lysimeter was used to simulate the transport through the soil profile with the pesticide leaching model Pesticide Emission Assessment at Regional and Local scales (PEARL). Chloridazon rapidly degraded to desphenyl-chloridazon and methyl-desphenyl-chloridazon. In leachate, chloridazon was therefore detected at concentrations up to 3.5 μg L−1, whereas the metabolites desphenyl-chloridazon and methyl-desphenyl-chloridazon were present for more than 2 years at higher concentrations up to 24 and 6.1 μg L−1. The concentrations of chloridazon in soil decreased significantly with depth and time, whereas both metabolites increased up to 370 and 16 μg kg−1. The high concentrations, even 916 days after the application, clearly indicate a continuous downward migration and degradation in soil. In maize, chloridazon and purely the metabolite desphenyl-chloridazon were detected in leaves and stems. Desphenyl-chloridazon was additionally found in grains. It was noted that the design and setup of the two lysimeters lead to significant variations in terms of transformation rate, soil retention time and accumulation by plants. A comparison of the simulated results and the leaching rates measured from the monolithic lysimeter yielded adequate results for the metabolites, but rather poor correlation for chloridazon. The results obtained suggest persistence and high dispersion of chloridazon, and especially its metabolites, in leachate and soil. In maize, the migration in leaves and stems and the accumulation by grains might be relevant in terms of food security.

Behavior of water balance components at sites with shallow groundwater tables: Possibilities and limitations of their simulation using different ways to control weighable groundwater lysimeters

The water cycle of sites with shallow groundwater tables is characterized by complex interactions of hydrological and ecological processes. The water balance components, which are subject to diurnal fluctuations, are best measured with groundwater lysimeters. However, the lower boundary condition of such lysimeters affects most of the hydrological variables, particularly when considering short time scales, and has to be defined in such a way as to facilitate realistic simulations. In this paper, different means of controlling the lower boundary condition of groundwater lysimeters were compared with respect to their ability to simulate the behavior of the water balance components properly. Measurements of rain-free periods from a lysimeter station installed in the Spreewald wetland in north–east Germany were evaluated. The most common groundwater lysimeter type is controlled using a Mariotte bottle and sets the groundwater level in the soil monolith to a constant level, which here caused an alteration of the inflow to the lysimeter, with respect to both its value and diurnal behavior. Still, daily evapotranspiration values were realistic and this simple and robust approach may be used for time intervals not shorter than one day. High-resolution measurements can be gained from lysimeters that automatically adjust the groundwater level by a system of pumps and valves on an hourly basis. Still, reliable results were only obtained when the conditions in the lysimeter and the surrounding field, where the target groundwater level was measured, were in accordance. Otherwise (e.g., when the groundwater level differed) an unrealistic inflow behavior evolved. Reasonable results, even for slightly diverging conditions, were gained with a new approach that defined the lower boundary conditions by controlling the inflows and outflows of the lysimeter. This approach further enabled the groundwater level itself to be the study subject, thereby enlarging the field of possible applications of groundwater lysimeters.

Land use and hydrologic flowpaths interact to affect dissolved organic matter and nitrate dynamics

The transport and transformation of dissolved organic matter (DOM) and dissolved inorganic nitrogen (DIN) through the soil profile impact down-gradient ecosystems and are increasingly recognized as important factors affecting the balance between accumulation and mineralization of subsoil organic matter. Using zero tension and tension lysimeters at three soil depths (20, 40, 60 cm) in paired forest and maize/soybean land uses, we compared dissolved organic C (DOC), dissolved organic N (DON) and DIN concentrations as well as DOM properties including hydrophilic-C (HPI-C), UV absorption (SUVA254), humification index and C/N ratio. Soil moisture data collected at lysimeter locations suggest zero tension lysimeters sampled relatively rapid hydrologic flowpaths that included downward saturated flow through the soil matrix and/or rapid macropore flow that is not in equilibrium with bulk soil solution whereas tension lysimeters sampled relatively immobile soil matrix solution during unsaturated conditions. The effect of land use on DOC and DON concentrations was largely limited to the most shallow (20 cm) sampling depth where DOC concentrations were greater in the forest (only zero tension lysimeters) and DON concentrations were greater in the cropland (both lysimeter types). In contrast to DOC and DON concentrations, the effect of land use on DOM properties persisted to the deepest sampling depth (60 cm), suggesting that DOM in the cropland was more decomposed regardless of lysimeter type. DOC concentrations and DOM properties differed between lysimeter types only in the forest at 20 cm where soil solutions collected with zero tension lysimeters had greater DOC concentrations, greater SUVA254, greater humification index and lower HPI-C. Our data highlight the importance of considering DOM quality in addition to DOC quantity, and indicate long-term cultivation reduced the delivery of relatively less decomposed DOM to all soil depths.

A Comparison of Tension and Zero-Tension Lysimeter and PRS™ Probes for Measuring Soil Water Chemistry in Sandy Boreal Soils in the Athabasca Oil Sands Region, Canada

Because soil acidification models use soil solution chemistry as a critical endpoint for predicting adverse biological effects, it is essential that various options for measuring soil water chemistry are assessed. This is particularly true for the Athabasca oil sands region of Alberta, Canada, as widespread acidification impacts are predicted based on modelled soil solution chemistry, but no soil solution data are currently available to validate these estimates. In this study, tension and zero-tension lysimeters were compared over a 3-year period at a jack pine stand (Pinus banksiana Lamb.) established in an acidic, sandy brunisol adjacent (<2 km) to one of the largest mines in the region. During the final year, plant root simulator (PRS™) probes were also installed for comparative purposes as they are currently being used in the region to assess changes in soil chemistry. Despite the close proximity to the mine and high sulphur (S) and nitrogen (N) deposition, the annual average pH of the soil water collected by both lysimeter types was around 6.5 and NO3–N concentrations were negligible. Annual SO4 concentrations in tension lysimeters averaged 12–14 mg L−1 and were typically two to four times higher than in zero-tension lysimeters; similar differences between lysimeters were observed for divalent base cations (Ca and Mg). Values (ion supply rates) obtained by PRS™ were affected by both the position of the probes (horizontal vs. vertical) and the duration of probe insertion (1, 2 and 5 months), such that higher values for most nutrients were obtained using probes that were installed vertically and for shorter periods of time. The Ca/Mg ratio in lysimeters and PRS™ probes were comparable, but other elemental ratios such as Ca/S or Ca/Al were much higher in PRS™ probes than in lysimeter water. Similar to lysimeter data, NO3–N values obtained by PRS™ probes were very low. PRS™ probes may be useful for assessing differences in nutrient availability among sites, but they do not reflect soil water chemistry that is used in geochemical acidification models.

A comparison of water flux measurements: passive wick‐samplers versus drainage lysimeters

Quantification of soil water flow is a prerequisite to accurate prediction of solute transfer within the unsaturated zone. The monitoring of these fluxes is challenging because the results are required to answer both scientific and practical questions regarding protection of groundwater, sustainable management of agricultural, forestry, mining or set‐aside industrial areas, reducing leachate loss from landfills or explaining the fate of environmentally harmful substances. Both indirect and direct methods exist for estimating water‐flux rates and have been used with varying success. In Europe, the use of direct lysimetry methods for measuring water and solute fluxes in soils has increased in recent years. This technique ensures reliable drainage data, but requires relatively large investment and maintenance expenses. Other research groups, especially in the USA, have developed alternative techniques. In this paper we compare the functioning of a passive‐wick sampler, especially the deep‐drainage meter type (DDM), with two different types of drainage lysimeters (weighing and non‐weighing) under field conditions in Germany for the measurement period from May 2004 until April 2009. The study showed that under sandy soil conditions no significant differences occurred between the measurements from DDM and both drainage lysimeter types. Only in periods with increased precipitation was there a tendency of drainage over‐estimation by the DDM in comparison with the lysimeters tested. For longer periods, no significant differences in the amount of drainage or the pattern of drainage formation were found between weighing and non‐weighing gravitation lysimeters. The practical use of DDMs is restricted because the groundwater level must be &gt;2 m from the soil surface. Suggestions are made for the technical improvement of the DDM as well as the testing of the device with more cohesive soils.

Advances In Out Door Lysimeter Techniques

Different methods exist for measuring soil water and solute fluxes in and below the root zone and have been critically reviewed. Besides indirect methods (e.g. water balance, tensiometer, time domain reflectometry – TDR, frequency domain reflectometry – FDR, environmental tracer) direct methods (e.g. drainage-type lysimeter, water fluxmeter) have a long tradition and have been successfully used in seepage research. A large weighable out door lysimeter is the best method for obtaining reliable data about seepage water quantity and quality, but it involves significant investment and additional expenses for maintenance. To tackle this problem new methods for the vertical collection of large volume soil monoliths (up to 6 m3) as well as for the horizontal collection (up to 6 m3) have been developed. For the placement of the lysimeter a container lysimeter unit was constructed, which is cheaper than a conventional steel or concrete cellar. Furthermore, the technical design of the newly developed lysimeter types as a weighable gravitation lysimeter, a weighable groundwater lysimeter and a lateral flow lysimeter are presented.

Measurement of dew, fog, and rime with a high‐precision gravitation lysimeter

AbstractExact information about soil water flow is needed to quantify solute transfer within the unsaturated zone. Water flux densities are often measured indirectly, e.g., with water‐balance, water content–change, or tracer methods, and, therefore, often predicted with notable uncertainties. Over the last years, direct lysimetry methods have been increasingly used to study water and solute migration in soil profiles. A large weighable lysimeter is the best method to obtain reliable drainage data, but it requires relatively high investment and maintenance expenses. To reduce cost and improve comparability with undisturbed sites, a new technology to collect large monolithic soil columns with a surface area of 0.5–2 m2 and a depth of 1–3 m as well as a containerized polyethylene (PE‐HD) lysimeter station were developed. In addition, the station was fitted with a new high‐precision weighing technique. In this paper, the latter is demonstrated with data from a newly constructed gravitation lysimeter. Besides recording rainfall and seepage, its weighing precision makes it possible to register mass input by dew, fog, or rime. It also permits a very accurate calculation of actual evapotranspiration. Because this new type of lysimeter allows a very high temporal resolution, it is ideally suited to develop and test models for soil hydrologic processes.

The Role of Laboratory and Field Leaching Tests in Hazard Identification for Solid Materials

The use of various in vitro toxicity assays for testing environmental solid samples is dependent on the availability of reliable methods for the sampling and pretreatment of the material. This study focuses on the evaluation of leaching behaviour as a first step in the context of the toxicity testing of solid environmental matter. Spent shale, from oil shale retorting, was chosen as a suitable example of deposited solid waste material. For the generation of leachate in the laboratory setting, a standard two-stage batch-leaching test was applied to the samples of technogenic waste. In the field, a new type of lysimeter, which does not disturb the surface, was used for in situ leachate collection. The chemical composition of water extracts was found to be different under field conditions, as compared with the laboratory experiments. Thus, the hazard identification of a solid technogenic waste by in vitro toxicological tests applied to laboratory leachates would not be the best solution. The content of hazardous ingredients could be underestimated if only laboratory tests are used. For risk assessment concerned with solid waste materials, the generation of leachate by using field lysimeters is recommended.

Comparing Unsaturated Colloid Transport through Columns with Differing Sampling Systems

Methodological difficulties of colloid sampling in the vadose zone are limiting our knowledge regarding the relevance of colloid transport for groundwater contamination. We compared the colloid sampling efficiency of five different lysimeters in a column experiment (9 cm length, 8 cm diameter) using 59Fe‐labeled goethite: polyester membranes with a pore diameter of (i) 1.2 μm and (ii) 10 μm, (iii) porous glass plates with 16‐μm pore diameter, (iv) wick samplers, and (v) zero‐tension lysimeters. Four replications of each lysimeter type were tested with concentrations of 0.1 and 10 mg L−1 goethite. The irrigation rate was 58 mm h−1, which caused an average transport velocity of 240 mm h−1 Compared with NO3−, a tendency of accelerated transport of goethite in the sand columns was observed. The mean recovery of 59Fe for all lysimeters was 30.7 ± 6.7% for the small and 3.4 ± 3.5% for the large colloid input concentration. For the small goethite concentration, no differences between lysimeter systems were detected. In contrast, the lysimeters performed differently at large concentrations: zero‐tension and 10‐μm membrane lysimeters showed the largest (9.1 and 6.8%), wick lysimeters the smallest colloid recovery (0.7%), which was related to trapping of colloids in the wick. We conclude that membranes of 10‐μm pore size and zero‐tension lysimeters are superior for colloid sampling, but the results of the latter may be biased toward an overestimation of colloid transport because of water saturation at the lysimeter–soil interface.

Comparison of soil solution chemistry sampled by centrifugation, two types of suction lysimeters and zero-tension lysimeters

The choice of sampling method for soil solution is of great importance. In this paper soil solution chemistry sampled by centrifugation, two types of suction lysimeters and zero-tension lysimeters have been studied with the purpose of investigating systematic differences between them. The samples were taken at 4 depths from an acidified forest soil as well as from adjacent lime and ash treated soils. A centrifugation drainage method was compared with two types of suction lysimeters (‘Rhizon’ and ‘Prenart’) and zero-tension lysimeters. About half of the 27 variables measured showed a significant difference between the sampling methods used. Typically the centrifuged samples had lower pH (4.0 vs. 4.4), Ca (21 μM vs. 30 μM) and Mg (25 μM vs. 34 μM) concentrations and higher Cl (330 μM vs. 230 μM) and DOC (4.4 mM vs. 3.2 mM) concentrations than the Rhizon lysimeters. Also the other lysimeters showed significant differences compared to the centrifuged samples for about half the number of analytes. Centrifuged samples had higher concentrations of all analytes except NO 3 and PO 4 compared to zero-tension lysimeters and also for all analytes except NO 3 and Al compared to Prenart lysimeters. Among the environmental factors considered depth showed an influence to some extent, while sampling occasion had a great significant impact on the difference between the centrifugation method and the Rhizon lysimeters. Factors like individual pits or soil treatment did not show any influence on the difference between the methods.

Comparison of type and depth of lysimeter for measuring the leaching losses of nitrogen under urine patches

. A study of the leaching losses of nitrate under urine patches in irrigated and non-irrigated dairy pastures in the South East of South Australia was undertaken with repacked and monolith lysimeters 1 m deep, and with monolith lysimeters 150, 300 and 450 mm deep. The aim was to quantify differences in measurements of drainage and nitrogen fluxes for these different lysimeters. Drainage of water and N flux were found to vary significantly between types and depths of lysimeters. Drainage volumes in repacked lysimeters were 78% and 33% more than in monolith lysimeters in irrigated and non-irrigated paddocks, and N fluxes were 5 and 3 times higher in repacked lysimeters respectively. The results indicate that lysimeter estimates of recharge rates and N fluxes to water tables are best determined by leaching studies which are longer term, and use deep monolith lysimeters. Shorter term studies and the use of shallow or repacked lysimeters have potential to distort conclusions.

Release of Arsenic to the Environment from CCA-Treated Wood. 2. Leaching and Speciation during Disposal

Wood treated with chromated copper arsenate (CCA) is primarily disposed within construction and demolition (C&D) debris landfills, with wood monofills and municipal solid waste (MSW) landfills as alternative disposal options. This study evaluated the extent and speciation of arsenic leaching from landfills containing CCA-treated wood. In control lysimeters where untreated wood was used, dimethylarsinic acid (DMAA) represented the major arsenic species. The dominant arsenic species differed in the lysimeters containing CCA-treated wood, with As(V) greatest in the monofill and C&D lysimeters and As(III) greatest in the MSW lysimeters. In CCA-containing lysimeters, the organoarsenic species monomethylarsonic acid (MMAA) and DMAAwere virtually absent in the monofill lysimeter and observed in the C&D and MSW lysimeters. Overall arsenic leaching rate varied for the wood monofill (0.69% per meter of water added), C&D (0.36% per m), and MSW (0.84% per m) lysimeters. Utilizing these rates with annual disposal data, a mathematical model was developed to quantify arsenic leaching from CCA-treated wood disposed to Florida landfills. Model findings showed between 20 and 50 t of arsenic (depending on lysimeter type) had leached prior to 2000 with an expected increase between 350 and 830 t by 2040. Groundwater analysis from 21 Florida C&D landfills suspected of accepting CCA-treated wood showed that groundwater at 3 landfills was characterized by elevated arsenic concentrations with only 1 showing impacts from the C&D waste. The slow release of arsenic from disposed treated wood may account for the lack of significant impact to groundwater near most C&D facilities at this time. However, greater impacts are anticipated in the future given that the maximum releases of arsenic are expected by the year 2100.

Tillage Effects on Nitrate Leaching Measured by Pan and Wick Lysimeters

No‐till (NT) is a recommended best management practice for reducing erosion in agricultural production. Because of potential increases in infiltration with NT, a better understanding of tillage effects on NO−3–N leaching is required. An experiment was conducted in central Pennsylvania on a Hagerstown silt loam (fine, mixed, semiactive, mesic Typic Hapludalf) to study NO−3–N leaching under chisel‐till and NT and to compare results from zero‐tension pan and passive capillary fiberglass wick lysimeters from May 1995 to April 2001. Pan lysimeters collected greater leachate volumes from NT than from tilled treatments during the growing season, likely due to greater macropore flow in NT soil. When leachate collection efficiency corrected values were used, pan and wick lysimeters collected equivalent masses of NO−3–N. Flow weighted NO−3–N concentrations in leachate in both lysimeter types were also similar. Tillage had no effect on total leachate collected during the 6‐yr experiment by either pan (228 mm yr−1) or wick (558 mm yr−1) lysimeters. Flow‐weighted NO−3–N concentrations and NO−3–N masses in leachate were not significantly different between tilled and NT, but increased with increasing N‐rate (at 0, 100, and 200 kg N ha−1, flow‐weighted NO−3–N concentrations were 3.5, 8.2, and 23.9 mg L−1 and NO−3–N masses were 17, 39, and 112 kg ha−1 yr−1, respectively). The results demonstrate that under our condition NT will not result in more NO−3 leaching than chisel‐tillage over a multiyear period.

Evaluation of Suction Cup Lysimeters for Obtaining Substrate Solution from a Pine Bark Substrate

Abstract Protocols are needed for extracting the container substrate solution of plants in large containers [≥ 18.9 liter (#5)] since the container substrate solution is representative of the nutrients available to the plants. The objective of this study was to determine the effectiveness of suction cup lysimeters (SCLs) for this purpose. The lysimeter types tested were those with a 4.8 cm (1.9 in) diameter and a ½ bar or 1 bar air-entry value (AEV) and those with a 2.2 cm (0.87 in) diameter also with a ½ bar or 1 bar AEV. A sufficient volume of the substrate solution could be obtained after 5 min when a vacuum pressure of 30, 40 or 50 kPa was applied to 4.8 cm (1.9 in) ½ bar lysimeters. The 2.2 cm (0.87 in) lysimeters were suitable for extracting smaller sample volumes of solution or if installation space was limited. Electrical conductivity (EC) levels were unaffected by volume of substrate solution extracted by the SCL when volumes varied from 10 to 190 ml (0.34 to 6.4 oz). Overall, the 4.8 cm (1.9 in) diameter lysimeters are recommended for use with large nursery containers.