Lysimeter Leachate Research Articles

Fertilizer placement and tillage effects on phosphorus concentration in leachate from fine-textured soils

Adoption of no-tillage in agricultural watersheds has resulted in substantial reductions in sediment and particulate phosphorus (P) transport in surface runoff. No-tillage, however, may result in increased losses of dissolved P in tile-drained landscapes due to the accumulation of P in surface soil layers and prevalence of preferential flow pathways. The objective of this study was to examine the effect of fertilizer placement and tillage on P leaching in fine-textured soils following fertilizer application. Rainfall simulations (90 min; 3.8 cm rainfall depth) immediately following application of monoammonium phosphate fertilizer (75 kg P ha−1) were conducted on 9 m2 plots with pan lysimeters (0.6 m depth) in four agricultural fields located in northwestern Ohio, USA. Three fertilizer placement treatments that covered a range of soil disturbance and soil-fertilizer mixing (broadcasted, injected, and tilled) were replicated on each field. Stable water isotopes were used to separate leachate into preferential and matrix flow components. Results showed that leachate dissolved P concentration was significantly greater when fertilizer was surface broadcast on no-tilled plots (43.7 mg L−1) compared to when the fertilizer was either injected (14.9 mg L−1) or tilled (11.0 mg L−1) into the soil. Event water comprised between 6 and 46% (mean = 22%) of lysimeter leachate and did not vary among treatments. Similar event water contributions among treatments suggest that the disruption of the macropore network was not likely the main mechanism responsible for decreased P concentration in leachate, but rather increased soil-fertilizer contact and decreased interaction between the highly soluble fertilizer and ponded surface water were likely responsible for decreased P concentrations observed for the injected and tilled treatments compared to the broadcasted treatment. Findings indicate that subsurface injection of fertilizer has the potential to limit dissolved P leaching compared to surface broadcast applications and also minimize soil disturbance relative to tillage; thus, it should be considered a promising conservation practice to help meet water quality goals in tile-drained landscapes.

Use of read-across to simplify the toxicological assessment of a complex mixture of lysimeter leachate metabolites on the basis of chemical similarity and ADME behavior

This paper describes the further development of a read-across approach applicable to the toxicological assessment of structurally-related xenobiotic metabolites. The approach, which can be applied in the absence of definitive identification of all the individual metabolites, draws on the use of chemical descriptors and multi-variate statistical analysis to define a composite “chemical space” and to classify and characterize closely-related subgroups within this. In this example, consideration of the descriptors driving grouping, combined with empirical evidence for lack of significant further biotransformation of metabolites, leads to the conclusion that, in the absence of any specific structural alerts, the relative toxicity of metabolites within a single grouping will be determined by their relative systemic exposure as described by their ADME characteristics. The in vivo testing of a smaller number of exemplars, selected to have representative ADME properties for each grouping, is sufficient, therefore, to evaluate the toxicity of the remainder. The approach is exemplified using the metabolites of the herbicide S-metolachlor, detected in the leachate of a soil lysimeter.

Enhanced performance of the aerobic landfill reactor by augmentation of manganese peroxidase

The aim of the work discussed in this article was to determine the ability of an MnP augmented aerobic waste cell to reach stable conditions rapidly in terms of gas production, nutrient content and cellulose and hemicellulose to lignin ratio (C+H/L). Two types of experiments were conducted; small batch and laboratory scale lysimeter experiments. Results from batch experiments showed that enzyme added treatments have the capability to reach a stable C+H/L and lower gas production rates, faster than the treatments without enzyme addition. Enzyme enhancement of the lysimeter increased the rate of biodegradability of the waste; gas production increased more than two times and there was clear evidence of increase in nutrients (nitrogen, dissolved carbon, biological oxygen demand) in the lysimeter ​leachate.

High‐resolution accurate mass spectrometry as a technique for characterization of complex lysimeter leachate samples

Lysimeter studies can be used to identify and quantify soil degradates of agrochemicals (metabolites) that have the potential to leach to groundwater. However, the apparent metabolic profile of such lysimeter leachate samples will often be significantly more complex than would be expected in true groundwater samples. This is particularly true for S-metolachlor, which has an extremely complex metabolic pathway. Consequently, it was not practically possible to apply a conventional analytical approach to identify all metabolites in an S-metolachlor lysimeter study, because there was insufficient mass to enable the use of techniques such as nuclear magnetic resonance. Recent advances in high-resolution accurate mass spectrometry, however, allow innovative screening approaches to characterize leachate samples to a greater extent than previously possible. Leachate from the S-metolachlor study was screened for accurate masses (±5 ppm of the nominal mass) corresponding to more than 400 hypothetical metabolite structures. A refined list of plausible metabolites was constructed from these data to provide a comprehensive description of the most likely metabolites present. The properties of these metabolites were then evaluated using a principal component analysis model, based on molecular descriptors, to visualize the entire chemical space and to cluster the metabolites into a number of subclasses. This characterization and principal component analysis evaluation enabled the selection of suitable representative metabolites that were subsequently used as exemplars to assess the toxicological relevance of the leachate as a whole. Environ Toxicol Chem 2016;35:1401-1412. © 2015 SETAC.

Assessment of Treatment Efficiency of Lysimeter Leachate using Leachate Pollution Index

This study illustrates the leachate treatment efficiency based on leachate pollution index (LPI) of pre- treatment leachate as well as post-treatment leachate with chemical coagulants. Leachate samples were collected at regular intervals of time from the leachate collection chamber of the landfill lysimeter at KUET campus, Bangladesh to compute its pollution potential. The landfill lysimeter consists of one open dump lysimeter-A with leachate detection (A1) and collection system (A2) as well as two sanitary landfill lysimeters B and C having two different types of cap liner. The relevant parameters of leachate sample were measured in the laboratory to evaluate sub-pollution (sub-LPIs) in terms of LPI in organic pollutant (LPIor), inorganic pollutant (LPIin) and heavy metal (LPIhm) as well as the overall LPI. Moreover, the values of LPI in pre-treatment leachate were to be found 19.53, 25.33, 23.48 and 23.74 for the A1 and A2 systems of open lysimeter-A, as well as the collection systems of sanitary lysimeters- B and C, respectively. It reveals significantly the higher values than that of LPI of 5.77, 7.38 and 7.38 for the maximum leachate discharge standards of Bangladesh, India and Hong Kong, respectively. The leachate was then treated with ferric chloride (FeCl3), poly alluminum chloride (PAC), ferrus sulphate (FeSO4) and aluminum sulphate (Al2(SO4)3) in various dosages and pH values. The concentrations in post-treatment leachate by using FeCl3 at optimum dosage were to be found below the limit of maximum leachate discharge standards. Study also reveals the values of LPI of 5.32, 5.69, 5.32 and 5.24 in post-treatment leachate for the A1 and A2 systems of open lysimeter-A, as well as the collection systems of sanitary lysimeters-B and C, respectively belowthe values of LPI in leachate of maximum discharge standards. Finally, it can be concluded that differences in the level of contaminants of pre- treatment and post-treatment leachate indicated the role of leachate treatment system in minimizing the level of contaminants and lowering the risk of leachate contamination based on LPI.

Leaching and ponding of viral contaminants following land application of biosolids on sandy-loam soil

Much of the land available for application of biosolids is cropland near urban areas. Biosolids are often applied on hay or grassland during the growing season or on corn ground before planting or after harvest in the fall. In this study, mesophilic anaerobic digested (MAD) biosolids were applied at 56,000 L/ha on a sandy-loam soil over large containment lysimeters seeded to perennial covers of orchardgrass (Dactylis glomerata L.), switchgrass (Panicum virgatum), or planted annually to maize (Zea mays L.). Portable rainfall simulators were to maintain the lysimeters under a nearly saturated (90%, volumetric basis) conditions. Lysimeter leachate and surface ponded water samples were collected and analyzed for somatic phage, adenoviruses, and anionic (chloride) and microbial (P-22 bacteriophage) tracers. Neither adenovirus nor somatic phage was recovered from the leachate samples. P-22 bacteriophage was found in the leachate of three lysimeters (removal rates ranged from 1.8 to 3.2 log10/m). Although the peak of the anionic tracer breakthrough occurred at a similar pore volume in each lysimeter (around 0.3 pore volume) the peak of P-22 breakthrough varied between lysimeters (<0.1, 0.3 and 0.7 pore volume). The early time to peak breakthrough of anionic and microbial tracers indicated preferential flow paths, presumably from soil cracks, root channels, worm holes or other natural phenomena. The concentration of viral contaminants collected in ponded surface water ranged from 1 to 10% of the initial concentration in the applied biosolids. The die off of somatic phage and P-22 in the surface water was fit to a first order decay model and somatic phage reached background level at about day ten. In conclusion, sandy-loam soils can effectively remove/adsorb the indigenous viruses leached from the land-applied biosolids, but there is a potential of viral pollution from runoff following significant rainfall events when biosolids remain on the soil surface.

Construction and evaluation of simulated pilot scale landfill lysimeter in Bangladesh

This research concentrates the design, construction and evaluation of simulated pilot scale landfill lysimeter at KUET campus, Khulna, Bangladesh. Both the aerobic and anaerobic conditions having a base liner and two different types of cap liner were simulated. After the design of a reference cell, the construction of landfill lysimeter was started in January 2008 and completed in July 2008. In all construction process locally available civil construction materials were used. The municipal solid waste (MSW) of 2800–2985kg having the total volume of 2.80m3 (height 1.6m) and moisture content of 65% was deposited in each lysimeter by applying required compaction energy. In contrast, both the composition in terms of methane (CH4), carbon dioxide (CO2) and oxygen (O2) as well as the flow rate of landfill gas (LFG) generated from MSW in landfill lysimeter were measured and varied significantly in relation to the variation of lysimeter operational condition. Moreover, anaerobic lysimeter-C shows the highest composition of LFG in compare to the anaerobic lysimeter-B due to the providing of lower compaction of cap liner in anaerobic lysimeter-C. Here, it is interesting to note that in absence of compacted clay liner (CCL) and hence percolation of rainwater that facilitates rapid degradation of MSW in aerobic lysimeter-A has resulted in the highest settlement than that of anaerobic landfill lysimeter-B and C. Moreover, in case of anaerobic lysimeter-B and C, the leachate generation was lower than that of aerobic lysimeter-A due to the providing of cap liner in anaerobic lysimeter-B and C, played an important role to reduce the percolation of rainwater. The study also reveals that the leachate pollution index (LPI) has decreased in relation to the increasing of elapsed period as well as the LPI for collection system of aerobic lysimeter-A was higher than that of the collection system of anaerobic lysimeter-B and C. Finally, it can be depicted that LPI for lysimeter was significantly high and proper treatment will be necessary before discharging the lysimeter leachate into the water bodies.

Phytotoxicity testing of lysimeter leachates from aided phytostabilized Cu-contaminated soils using duckweed ( Lemna minor L.)

Aided phytostabilization of a Cu-contaminated soil was conducted at a wood preservation site located in southwest France using outdoor lysimeters to study leaching from the root zone and leachate ecotoxicity. The effects of Cu-tolerant plants ( Agrostis gigantea L. and Populus trichocarpa x deltoides cv. Beaupré) and four amendments were investigated with seven treatments: untreated soil without plants (UNT) and with plants (PHYTO), and planted soils amended with compost (OM, 5% per air-dried soil weight), dolomitic limestone (DL, 0.2%), Linz–Donawitz slag (LDS, 1%), OM with DL (OMDL), and OM with 2% of zerovalent iron grit (OMZ). Total Cu concentrations (mg kg − 1 ) in lysimeter topsoil and subsoil were 1110 and 111–153, respectively. Lysimeter leachates collected in year 3 were characterized for Al, B, Ca, Cu, Fe, Mg, Mn, P, K and Zn concentrations, free Cu ions, and pH. Total Cu concentration in leachates (mg L − 1 ) ranged from 0.15 ± 0.08 (LDS) to 1.95 ± 0.47 (PHYTO). Plants grown without soil amendment did not reduce total Cu and free Cu ions in leachates. Lemna minor L. was used to assess the leachate phytotoxicity, and based on its growth, the DL, LDS, OM and OMDL leachates were less phytotoxic than the OMZ, PHYTO and UNT ones. The LDS leachates had the lowest Cu, Cu 2+, Fe, and Zn concentrations, but L. minor developed less in these leachates than in a mineral water and a river freshwater. Leachate Mg concentrations were in decreasing order OMDL > DL > PHYTO = OM = LDS > UNT = OMZ and influenced the duckweed growth.

Fate of Mycobacterium avium subsp. paratuberculosis after application of contaminated dairy cattle manure to agricultural soils.

Details regarding the fate of Mycobacterium avium subsp. paratuberculosis (basonym, Mycobacterium paratuberculosis) after manure application on grassland are unknown. To evaluate this, intact soil columns were collected in plastic pipes (lysimeters) and placed under controlled conditions to test the effect of a loamy or sandy soil composition and the amount of rainfall on the fate of M. paratuberculosis applied to the soil surface with manure slurry. The experiment was organized as a randomized design with two factors and three replicates. M. paratuberculosis-contaminated manure was spread on the top of the 90-cm soil columns. After weekly simulated rainfall applications, water drainage samples (leachates) were collected from the base of each lysimeter and cultured for M. paratuberculosis using Bactec MGIT ParaTB medium and supplements. Grass was harvested, quantified, and tested from each lysimeter soil surface. The identity of all probable M. paratuberculosis isolates was confirmed by PCR for IS900 and F57 genetic elements. There was a lag time of 2 months after each treatment before M. paratuberculosis was found in leachates. The greatest proportions of M. paratuberculosis-positive leachates were from sandy-soil lysimeters in the manure-treated group receiving the equivalent of 1,000 mm annual rainfall. Under the higher rainfall regimen (2,000 mm/year), M. paratuberculosis was detected more often from lysimeters with loamy soil than sandy soil. Among all lysimeters, M. paratuberculosis was detected more often in grass clippings than in lysimeter leachates. At the end of the trial, lysimeters were disassembled and soil cultured at different depths, and we found that M. paratuberculosis was recovered only from the uppermost levels of the soil columns in the treated group. Factors associated with M. paratuberculosis presence in leachates were soil type and soil pH (P < 0.05). For M. paratuberculosis presence in grass clippings, only manure application showed a significant association (P < 0.05). From these findings we conclude that this pathogen tends to move slowly through soils (faster through sandy soil) and tends to remain on grass and in the upper layers of pasture soil, representing a clear infection hazard for grazing livestock and a potential for the contamination of runoff after heavy rains.

Variation in toxicity response of Ceriodaphnia dubia to Athabasca oil sands coke leachates

Coke from the Athabasca (Alberta, Canada) oil sands operations may someday be integrated into reclamation landscapes. It is hypothesized that the metals associated with the solid coke may leach into the surrounding environment. Therefore, the main objectives of this study were to characterize the toxicity and chemistry of coke leachates collected from two field lysimeters (i.e. shallow lysimeter and deep lysimeter) over a period of 20 months, as well as from other oil sands coke storage sites. In addition, a batch renewal leaching of coke was conducted to examine the rate of metals release. Chronic toxicity of key metals (e.g. Al, Mn, Ni and V) found in lysimeter coke leachate was evaluated separately. Toxicity test results revealed that whole coke leachates (100% v/v) were acutely toxic to Ceriodaphnia dubia; the 7-day LC50 values were always <25% v/v coke leachate. The deep lysimeter leachate was generally more toxic than the shallow lysimeter leachate, likely because of significantly higher concentrations of vanadium (V) found in the deep lysimeter leachate at all sampling times. Vanadium concentrations were higher than all other metals found in the leachate from both lysimeters, and in the batch renewal leaching study. Furthermore, V found in leachates collected from other oil sands field sites showed a concentration–response relationship with C. dubia survival. Mass balance calculations indicated that 94–98% of potentially leachable V fraction was still present in the coke from two field lysimeters. Evidence gathered from these assessments, including toxic unit (TU) calculations for the elements of concern, suggests that V was the likely cause of toxicity of the deep lysimeter leachate, whereas in the shallow lysimeter leachate both Ni and V could be responsible for the observed toxicity.

Inverse Modeling of Pesticide Leaching in Lysimeters: Local versus Global and Sequential Single‐Objective versus Multiobjective Approaches

This study used field lysimeter leachate and pesticide concentration data within an inverse modeling framework to estimate pesticide degradation and sorption parameters. Experimental data comprising four pesticide applications during 3 yr were used to compare a local parameter estimation algorithm (Levenberg–Marquardt, LM) with a global algorithm (Shuffled Complex Evolution Metropolis, SCEM). Good model fits (only marginally better model fits using SCEM) with respect to both the observed leachate volumes and corresponding pesticide concentrations were obtained using both algorithms. Parameter optima found with LM and SCEM were very similar, thus suggesting that LM correctly located the global optimum for our experimental data. Equally as important as the optimal parameter values, however, are the estimated parameter uncertainties. This study revealed that LM (using a Jacobian‐based approach) provided too large parameter uncertainties. A logarithmic transformation of the parameter tended to decrease the uncertainty in most cases. The overestimation of parameter uncertainty by LM suggests that model sensitivity close to the optimal parameter set was relatively small and underestimated the sensitivity to large parameter changes. A multiobjective Pareto analysis was subsequently compared with a sequential single‐objective approach to reveal the capability of the multiobjective approach to verify model structure and model concept. Our results indicate that a multiobjective SCEM approach is recommended when the objective is to estimate pesticide degradation and sorption parameters and their uncertainty.

Long‐Term Observations of Vadose Zone and Groundwater Nitrate Concentrations under Irrigated Agriculture

Proper N management for agricultural production is critical to minimize groundwater contamination with NO3 For 18 yr, research was conducted to observe NO3–N concentrations in the vadose zone, groundwater, and subsurface drainage under sprinkler‐irrigated, primarily corn (Zea mays L.) production. Potato (Solanum tuberosum L.) and soybean [Glycine max (L.) Merr.] were also grown intermittently on the site. The lysimeter leachate NO3–N concentration increased to 156 mg L−1 under corn production within 1 yr after the initiation of irrigation (at the onset of the study), then decreased to &lt;10 mg L−1 during a 6‐yr period of best‐management N fertility management for corn. The average yearly lysimeter NO3–N concentration fluctuated between 8 and 117 mg L−1 during the study. Nitrate concentrations in the shallow groundwater followed a similar time series trend as leachate concentrations, but with lower concentrations and lagging about 1 yr. Subsurface drainage NO3–N concentrations were much lower but followed the same trend as the shallow groundwater. An N balance indicated higher net N mineralization after the initiation of irrigation and the years after potato production. Fertilizer N application rates and yearly weather conditions, which affected crop vigor and N uptake, combined to affect the fall residual soil NO3 Fall soil NO3 from 0‐ to 1.8‐m depth was the most significant factor influencing the leachate NO3–N concentration each year during the study (r2 = 0.76).

Soil nutrient evaluation from swine effluent application to five forage-system practices

Many contract swine producers are located in the southeastern U.S. In this region almost all of the swine effluent from swine production is applied to warm-season perennial species such as bermudagrass [Cynodon dactylon (L.) Pers.] which is widely grown for summer grazing and hay production. A 3-yr study was conducted to investigate the impact of forage double-cropping on nutrient accumulation and leaching in Mantachie fine loam soil fertilized with swine (Sus scrofa domesticus) lagoon effluent as the source of plant nutrients. Plots of previously established Tifton 44 bermudagrass were overseeded in the fall with one of four winter annuals: berseem clover (Trifolium alexandrinum L.); crimson clover (T. incarnatum L.); ryegrass (Lolium multiflorum L.); or wheat (Triticum aestivum L.). Four plots of bermudagrass were not overseeded and considered as control. Plots were harvested in spring for cool-season annual hay and in summer for bermudagrass hay. Swine effluent was applied during spring and summer on a need base. Suction lysimeters were installed in selected plots at two depths to monitor nutrient leaching. Surface soil samples were taken to determine baseline nutrient contents, followed by three other sampling dates during the study. Bermudagrass dry matter production (3-yr average = 9.8 Mg ha−1) was not adversely affected by the overseeding treatments. Greatest dry matter production was achieved with bermudagrass overseeded with ryegrass (3-yr average = 11.3 Mg ha−1). Soil pH decreased by almost one unit by the end of the study. While total P (TP) did not change much, Mehlich-3 P (M3-P), K, Cu, and Zn increased significantly, Mg and Mn concentrations decreased by 2002 compared to the baseline levels. Soil P, Mg, K, Fe, Mn, and Zn accumulation were greater under bermudagrass/wheat combination. In general, the influence of double cropping on soil nutrient accumulation was not conclusive, however, this practice provides the year-round green forage for grazing and haying. Nutrient concentrations in soil and lysimeter leachate were directly related to the quantity of effluent applied. Results also demonstrated that effluent application must be coordinated with the nutrient requirements of the growing forages in order to minimize accumulation and leaching.

Performance of a buried radioactive high level waste (HLW) glass after 24 years

A radioactive high level waste glass was made in 1980 with Savannah River Site (SRS) Tank 15 waste. This glass was buried in a lysimeter in the SRS burial ground for 24 years. Lysimeter leachate data was available for the first 8 years. The glass was exhumed in 2004. The glass was predicted to be very durable and laboratory tests confirmed this. Scanning electron microscopy of the glass burial surface showed no significant glass alteration consistent with results of other laboratory and field tests. Radionuclide profiling for alpha, beta, and 137Cs indicated that Pu was not enriched in the soil while 137Cs and 90Sr were enriched in the first few centimeters surrounding the glass. Lysimeter leachate data indicated that 90Sr and 137Cs leaching from the glass was diffusion controlled.

Simulation of Pesticide Leaching in the Field and in Zero‐Tension Lysimeters

Zero‐tension lysimeters play an important role in groundwater risk assessments for pesticides in the European Union. In these assessments, measured lysimeter leachate concentrations are usually used directly for decision making. When doing so, one assumes (i) that the lysimeter bottom boundary condition itself did not lead to underestimating field leaching concentrations, (ii) that the number of application years and the duration of the lysimeter study were adequate to measure the maximum concentration in time, and (iii) that the pesticide‐lysimeter system considered was sufficiently vulnerable with respect to leaching. These assumptions were tested using simulations with a Darcian water flow model combined with a chromatographic pesticide leaching model. The scenario consisted of a layered light‐textured soil cropped with cereals and of multiyear weather data. The groundwater level in the field usually fluctuated between 0.7 and 2.5 m depth. The lysimeter bottom boundary condition resulted in pesticide leaching concentrations lower than those calculated for the field system. Simulations showed that a lysimeter study of 2 yr was too short to measure the maximum leaching concentration for pesticides with organic‐matter/water distribution coefficient values exceeding 40 L kg−1 The probability that a lysimeter study results in a leaching concentration below 0.1 μg L−1 by a coincidental favorable combination of pesticide–soil parameters was assessed by Monte Carlo simulations. This probability exceeded 20% for pesticides that would give leaching concentrations of 1 μg L−1 under field conditions. Therefore, it is advisable that for each lysimeter study, modeling be used to assess the likelihood that the leaching concentration would be below 0.1 μg L−1, considering all relevant systematic and random factors.

Leaching of milled asphalt pavement amended with waste to energy ash

The environmental suitability of using Waste-to-Energy (WTE) ash as a partial substitute for aggregate in hot-mix asphalt concrete was investigated using a series of leaching lysimeters. Eight samples of processed asphalt concrete manufactured with 25% by weight WTE ash as aggregate were leached using stainless steel lysimeters. A ninth lysimeter contained asphalt without WTE ash. Simulated rainfall was passed through the processed asphalt concrete to simulate pollutant leaching that might occur from stockpiled or disposed milled asphalt. Leachate samples were collected every five days for 75 days and analysed for lead, Total Dissolved Solids (TDS), aluminium, and chloride. Polychlorinated dibenzo-p-dioxins polychlorinated dibenzofurans, and polycyclic aromatic hydrocarbons were analysed in the first flush leachates but were not detected. Although previous batch leaching studies found lead, chloride, TDS, and aluminium to present possible risk to groundwater, the lysimeter leachates found only aluminium concentrations to remain above water quality standards throughout the experiment. Lead was detected only sporadically, and TDS and chloride diminished to below water quality thresholds early in the experiment. The source of the aluminium was the WTE ash.

The effect of five forage species on transport and transformation of atrazine and isoxaflutole (balance) in lysimeter leachate.

A field lysimeter study with bare ground and five different ground covers was established to evaluate the effect of forage grasses on the fate and transport of two herbicides in leachate. The herbicides were atrazine (ATR; 2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) and isoxaflutole [IXF; 5-cyclopropyl-4-(2-methylsulfonyl-4-trifluormethyl-benzoyl)isoxazole], which has the commercial name Balance (Aventis Crop Science, Strasbourg, France). The ground covers included orchardgrass (Dactylis glomerata L.), smooth bromegrass (Bromus inermis Leyss.), tall fescue (Festuca arundinacea Schreb.), timothy (Phleum pratense L.), and switchgrass (Panicum virgatum L.). The results suggested that the total IXF (parent + metabolites) showed higher mobility than ATR and its metabolites. Differences in the timing of transport reflected the rapid degradation of IXF to the more soluble, stable, and biologically active diketonitrile (DKN) metabolite in the system. Although grass treatments did not promote the hydrolysis of DKN, they significantly reduced its transport in the leachate through enhanced evapotranspiration. Grass treatments significantly enhanced ATR degradation in the leachates and soils, especially through N dealkylation, but they did not reduce total ATR transported in the leachate. Leachate from the orchardgrass lysimeters contained the highest proportion of ATR metabolites (64.2%). Timothy and smooth bromegrass treatments also displayed a significant increase in ATR metabolites in leachate. Grass-treated lysimeters showed higher microbial biomass carbon than bare ground. For ATR treatments, the proportion of metabolites in the leachate strongly correlated with the elevated soil microbial biomass carbon in forage treatments. In contrast, DKN degradation was poorly correlated with soil microbial biomass carbon, suggesting that DKN degradation is an abiotic process.

What limits the distributions of coastally restricted terrestrial invertebrates? The case of coastal landhoppers (Crustacea: Amphipoda: Talitridae) in southern Tasmania

AbstractAim A number of terrestrial invertebrates are known to have distributions limited to the immediate coastal zone, but the factors controlling their distributions are not well understood. This study was planned to correlate the distribution of a coastal terrestrial amphipod, Austrotroides maritimus Friend 1987, which is only found within 100 m of the high tide mark, with soil characteristics and salt deposition.Location South Cape Rivulet Bay on the south coast of Tasmania (146°47′ E, 43°36′ S).Methods Abundance of the amphipods was examined at four sites c. 200 m apart that varied in their exposure to onshore westerly winds. At each site four replicate transect lines were established 3 m apart, with pitfall traps set at 2‐m intervals. The lines were at right angles to the high water mark and extended beyond the inland limit of A. maritimus. Amphipods were trapped at three times of the year, in winter, spring and summer (1993–94), and the sodium content, organic content and moisture content of the soil at each trap site were measured. The sodium content of rain falling on the transects, was also measured, and lysimeters were used to assess the concentration of sodium in water penetrating the soil profile.Results The inland penetration of A. maritimus varied between 18 and 44 m from the seaward edge of woody terrestrial vegetation (itself &lt;10 m horizontally from the high tide mark). Inland penetration increased from west to east around the bay, following an apparent gradient of increased exposure to onshore winds. At the most easterly and apparently most exposed site, however, the species penetrated only 18 m, but this site differed markedly from the others in its topography, caused by erosion of the dunes, with an 8‐m cliff at its seaward end. The soils at this site were also unusually clayey and waterlogged. Amphipod abundance did not correlate strongly with any of the soil parameters. The salt content of rainfall generally declined inland, as did the concentration of lysimeter leachate, but the inland declines were not all smooth, and both rainfall and lysimeter leachate concentration showed some tendency to increase inland at the most sheltered site.Main conclusions Austrotroides maritimus is strongly restricted to the immediate coastal zone. The extent of its inland penetration correlates with exposure to onshore winds, and circumstantial evidence supports the hypothesis that this may be due to differences in the amount of salts deposited.

Leachate Collection Efficiency of Zero‐tension Pan and Passive Capillary Fiberglass Wick Lysimeters

Lysimeter leachate collection efficiencies (LCEs), which are the measured leachate volume divided by estimated percolation water, are needed to convert measured leachate volumes to actual leachate fluxes. In this study, LCE of zero‐tension pan and passive capillary fiberglass wick lysimeters were evaluated and directly compared. A total of 18 pan and 18 wick lysimeters were installed 1.2 m below the soil surface in tilled and no‐till plots. From May 1995 to April 2000 the lysimeter LCEs were evaluated using a water‐balance method with evapotranspiration (ET) estimated by the Penman‐Monteith equation. On average, wick lysimeters collected 2.7 times more leachate than did pan lysimeters, and tillage had no effect on the 5‐yr total leachate volume at the 5% significance level. If the anomalous 1997 leaching year with an exceptionally warm and wet winter was excluded, wick and pan lysimeters collected about 50 and 20% of precipitation, respectively, from both tillage systems. The average 4‐yr LCE for wick lysimeters was 101% and that for the pan lysimeters was 40%. The much higher LCEs for both pan and wick lysimeters during the 1997 leaching year were thought to be the result of over‐sampling of leachate during the exceptionally wet and warm winter. Errors of ET estimates associated with estimating crop residue cover and water stress adjustment parameters were small. Errors in LCE estimates can be mathematically shown to be in the same range as those of ET estimates.

Chlorothalonil and chlorpyrifos degradation products in golf course leachate.

Chlorothalonil and chlorpyrifos are commonly used to control disease and insect pests on golf course greens. While they are relatively immobile in the soil profile, their respective soil degradation products, 4-hydroxy-2,5,6-trichloroisophthalonitrile and 3,5,6-trichloropyridin-2-ol are more polar and may be present in golf course green leachate. To investigate this possibility, six stainless steel lysimeters were constructed into two practice greens at a country club in a northern Atlanta, Georgia suburb. Over a period of 1 year after rainfall events, lysimeter leachate samples were collected into glass bottles, filtered and directly analyzed by HPLC with UV detection. Chlorpyrifos was not detected in any sample and chlorothalonil was detected only in one sample, at a concentration of 0.12 mg liter-1. With a limit of quantitation of 0.05 mg liter-1, hydroxychlorothalonil and trichloropyridinol were detected in 87% and 63% of the samples at maximum and median concentrations of 2.21 and 0.55 mg liter-1 for hydroxychlorothalonil and 1.77 and 0.15 mg liter-1 for trichloropyridinol. Golf course green leachate often mixes with surface water, thus more data may be warranted to determine the persistence and ecological significance of chronic exposure to these compounds of organisms in the aquatic environment.