A simulation procedure for groundwater quality assessments of pesticides

A procedure is described for making regional assessments of pesticide residue loadings and movement in groundwater underneath and downgradient from treated fields. A Monte-Carlo numerical simulation technique is used to generate model parameters for both the unsaturated and saturated zones. Simulations are performed using the Pesticide Root Zone Model linked to a simple groundwater solute transport model.The procedure is useful for evaluating the potential for producing pesticide residues in drinking water wells before actual field applications are made. Appropriate land management options, including restrictions on pesticide application, also can be developed using this procedure.The procedure was used to assess aldicarb levels in northeastern North Carolina groundwater resulting from application of the pesticide to peanuts. Probability density functions for selected soil characteristics were developed using a direct-access soils information data base. Probability density functions for selected groundwater characteristics were developed from available data for the study area. Simulation results indicated that mass fluxes to groundwater exceeded 0.01 and 0.1 kg ha⁻¹ approximately 6.9 and 1.0 percent of the time, respectively. No fluxes exceeded 0.1 kg ha⁻¹ at a distance of 60 m downgradient in any of the cases evaluated.     

Movement and degradation of aldicarb residues in the saturated zone under citrus groves on the Florida ridge

A 1.7-ha section of citrus grove near Lake Hamilton was the site of a three-year field study designed to monitor the movement and degradation of the nematicide and insecticide aldicarb in the central ridge area of Florida. Soil cores were used to monitor the fate of aldicarb residues in the unsaturated zone and over 2,000 groundwater samples were collected from 174 monitoring wells to measure horizontal and vertical transport of aldicarb residues in the saturated zone. A simple saturated zone model was used to estimate the degradation rate of aldicarb residues and extrapolate findings to other ridge areas.The results of the study suggest that in the saturated zone aldicarb residues degrade at a rate corresponding to a half-life of approximately eight months. The predominantly horizontal movement of groundwater at this site limits aldicarb residues to the upper three to five meters of the saturated zone. Field data from this site together with unsaturated and saturated zone simulations suggest that in this area of Florida current restrictions on aldicarb used near potable wells are adequate to protect drinking water supplies.     

Aldicarb and carbofuran transport in a Hapludalf influenced by differential antecedent soil water content and irrigation delay

Pesticide use in agroecosystems can adversely impact groundwater quality via chemical leaching through soils. Few studies have investigated the effects of antecedent soil water content (SWC) and timing of initial irrigation (TII) after chemical application on pesticide transport and degradation. The objectives of this study were to investigate the effects of antecedent soil water content (wet vs dry) and timing of initial irrigation (0h Delay vs 24h Delay) on aldicarb [(EZ)-2-methyl-2-(methylthio)propionaldehyde O-methylcarbamoyloxime] and carbofuran [2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate] transport and degradation parameters at a field site with Menfro silt loam (fine-silty, mixed, superactive, mesic Typic Hapludalf) soils. Aldicarb and carbofuran were applied to plots near field capacity (wet) or near permanent wilting point (dry). Half of the dry and wet plots received irrigation water immediately after chemical application and the remaining plots were irrigated after a 24h Delay. The transport and degradation parameters were estimated using the method of moments. Statistical significance determined for SWC included averages across TII levels, and significance determined for TII included averages across SWC levels. For the dry treatment, aldicarb was detected 0.10 m deeper (P<0.01) on two of the four sampling dates and carbofuran was detected at least 0.10 m deeper (P<0.05) on all of the sampling dates compared to the wet treatment. Pore water velocity was found to be higher (P<0.10) in the dry vs wet treatments on three of four dates for aldicarb and two of four dates for carbofuran. Retardation coefficients for both pesticides showed similar evidence of reduced values for the dry vs wet treatments. These results indicate deeper pesticide movement in the initially dry treatment. For aldicarb and carbofuran, estimated values of the degradation rate were approximately 40-49% lower in the initially dry plots compared to the initially wet plots, respectively. When the initial irrigation was delayed for 24h, irrespective of antecedent moisture conditions, a 30% reduction in aldicarb degradation occurred. This study illustrates the deeper transport of pesticides and their increased persistence when applied to initially dry soils.     

涕灭威对地下水污染敏感区的预测与区划试点

本文根据涕灭威在室内模拟试验与田间试验的结果，详细剖析了影响涕灭威农药在土壤中残留和移动的各种因子，建立了涕灭威农药对地下水污染的敏感性模型，并就涕灭威农药在江苏使用后对地下水可能造成污染的情况进行了预测与区划试点，结果与用美国环保局提供的ＰＲＺＭ模型计算结果和田间实测结果基本一致，本模型可用于预测涕灭威农药在其它地区使用后对地下水可能造成污染的情况。     

A sensitivity analysis of adsorption and degradation parameters in the modeling of pesticide transport in soils

The increasing use of deterministic models in predicting the movement of pesticides in soils, has focused attention on the evaluation of major parameters which represent attenuation factors of organics in the subsurface. These parameters are the degradation rate constant and the adsorption constant for the pesticide. In view of the large in situ variability of these parameters and of the difficulty in obtaining accurate field data, there is a high degree of uncertainty associated with the results obtained from deterministic models. A sensitivity analysis is performed here to quantify the impact of such variation in each of these input parameters on the output results of an unsaturated zone transport model (PRZM). Results show that variations in these parameters about their respective mean values greatly affect the predicted concentration distributions, obtained after three years, of the pesticide aldicarb in all the soil profile. A 15–22% variation in the degradation constant, or a 24% variation in the adsorption constant, lead to a 100% uncertainty in the various simulation results defined as the cumulative quantity of aldicarb or the dissolved aldicarb concentration leached below the root zone (or the unsaturated zone) of the soil. Such a deterministic model presents a high degree of sensitivity to these input parameters. Accurate field data are then needed to obtain reliable model results in predicting pesticide movement inthe unsaturated zone.     

Central California studies on the degradation and movement of aldicarb residues

Studies to measure the degradation and movement of aldicarb residues in the unsaturated and saturated zone were conducted during 1984 at three central California locations. These test sites, which consist of a tomato field near Manteca and vineyards near Livingston and Fresno are representative of conditions in central California under which aldicarb residues are most likely to reach drinking-water supplies.Results indicate that aldicarb residues degrade in the unsaturated zone with a half-life of 1.5–2.0 months. In areas with shallow water tables (less than three meters deep), traces of aldicarb residues may occasionally enter the upper one to five meters of the saturated zone where they degrade before reaching deeper, potable water supplies.     

Plant uptake of aldicarb from contaminated soil and its enhanced degradation in the rhizosphere

Experiments were conducted to investigate the degradation of aldicarb, an oxime carbamate insecticide, in sterile, non-sterile and plant-grown soils, and the capability of different plant species to accumulate the pesticide. The degradation of aldicarb in soil followed first-order kinetics. Half lives (t1/2) of aldicarb in sterile and non-sterile soil were 12.0 and 2.7 days, respectively, which indicated that microorganisms played an important part in the degradation of aldicarb in soil. Aldicarb disappeared more quickly (p< or =0.05) in the soil with the presence of plants, and t1/2 of the pesticide were 1.6, 1.4 and 1.7 days in the soil grown with corn, mung bean and cowpea, respectively. Comparison of plant-promoted degradation and plant uptake showed that the enhanced removal of aldicarb in plant-grown soil was mainly due to plant-promoted degradation in the rhizosphere.     

Environmental fate studies of aldicarb and aldoxycarb applications to Wisconsin potatoes

Aldicarb and aldoxycarb pesticides were applied to potato fields in central Wisconsin to study the degradation and movement of their carbamate residues within the soil profile. Aldicarb and aldoxycarb residues degraded at similar rates with half-lives ranging from 0.9 to 1.4 months. Although unsaturated-zone residue measurements indicated relatively minor differences among the three plots, residues were detected in shallow groundwater beneath plots treated with aldicarb or aldoxycarb at planting. Residues beneath the plot treated with aldicarb at emergence were much lower and the timing of these residues suggests they might have resulted from migration of residues from the plot treated with aldicarb at planting. This study confirms the results of previous and concurrent research programs which suggest that emergence applications of aldicarb reduce the potential for residues to enter shallow groundwater without reducing insect control or potato yields.     

Modelling the geochemical fate and transport of wastewater-derived phosphorus in contrasting groundwater systems

A 1D reactive transport model (RTM) is used to obtain a mechanistic understanding of the fate of phosphorus (P) in the saturated zone of two contrasting aquifer systems. We use the field data from two oxic, electron donor-poor, wastewater-impacted, sandy Canadian aquifers, (Cambridge and Muskoka sites) as an example of a calcareous and non-calcareous groundwater system, respectively, to validate our reaction network. After approximately 10 years of wastewater infiltration, P is effectively attenuated within the first 10 m down-gradient of the source mainly through fast sorption onto calcite and Fe oxides. Slow, kinetic sorption contributes further to P removal, while precipitation of phosphate minerals (strengite, hydroxyapatite) is quantitatively unimportant in the saturated zone. Nitrogen (N) dynamics are also considered, but nitrate behaves essentially as a conservative tracer in both systems. The model-predicted advancement of the P plume upon continued wastewater discharge at the calcareous site is in line with field observations. Model results suggest that, upon removal of the wastewater source, the P plume at both sites will persist for at least 20 years, owing to desorption of P from aquifer solids and the slow rate of P mineral precipitation. Sensitivity analyses for the non-calcareous scenario (Muskoka) illustrate the importance of the sorption capacity of the aquifer solids for P in modulating groundwater N:P ratios in oxic groundwater. The model simulations predict the breakthrough of groundwater with high P concentrations and low N:P ratios after 17 years at 20 m from the source for an aquifer with low sorption capacity (<0.02% w/w Fe(OH)(3)). In this type of system, denitrification plays a minor role in lowering the N:P ratios because it is limited by the availability of labile dissolved organic matter.     

The persistence of insecticidal chemicals in soils treated with granular formulations of aldicarb and their uptake by potato plants

Abstract

Potatoes were grown in Plainfield sand and muck treated, in furrow, with aldicarb (Temik 15G, 3.36 kg Al/ha). .Soils were contained in 2 m^z field plots and had not been treated previously with pesticides. Soil, seed pieces, foliage and tubers were analyzed for the insecticide and its sulfoxide and sulfone metabolites during the 12 wk following planting. The disappearance of aldicarb from the soil was accompanied by partial conversion to the sulfoxide and sulfone. After increasing rapidly during the first 2 wk, the aldicarb concentration in the seed piece declined and a similar concentration of aldicarb sulfoxide accumulated which subsequently slowly disappeared. Aldicarb sulfoxide was the major insecticidal material in the new foliage. High initial concentrations, observed at 3–4 wk, declined by about 90% after 6 wk. Aldicarb sulfoxide residues of 2–4 ppm in the first new tubers at 6 wk declined by 90% by 12 wk. Potatoes were also grown under greenhouse conditions in Plainfield sand treated with Temik 10G at rates equivalent to 1.68, 3.36 and 6.72 kg Al/ha. Maximum aldicarb sulfoxide concentrations in soil, seed piece and foliage increased with application rate. The sulfoxide was much more persistent in the soil and foliage than in the field experiment indicating the importance of environmental factors to its behaviour in both soil and potato plants.     

The Need for a More Robust Ozone Air Quality Standard

The present National Ambient Air Quality Standard for ozone has many statistical problems, including use of extreme values which have inherent large fluctuations, a compliance test that can gradually lower the target of the design value below the standard level, and inconsistencies between the number-of-exceedances criterion and the design value. The above problems can be avoided or minimized by using a more robust statistic, such as the 95th percentile, and applying a statistical compliance test, without sacrificing the stringency of the standard. Analysis of EPA’s ozone data shows that the annual 95th percentiles and their three-year means have less variability than the annual second highest values and the fourth highest values in three years, respectively. A t test for the mean of the annual 95th percentiles is proposed for compliance testing not only to preserve the averaging concept of the present standard, but also to take account of ozone concentration fluctuations in order to increase the stability of the compliance status of a site or a Metropolitan Statistical Area. A procedure is provided to adjust the level of the 95th-percentile standard so that the stringency of the present standard is preserved.     

Linking a one-dimensional pesticide fate model to a three-dimensional groundwater model to simulate pollution risks of shallow and deep groundwater underlying fractured till

The one-dimensional pesticide fate model MACRO was loose-linked to the three-dimensional discrete fracture/matrix diffusion model FRAC3DVS to describe transport of the pesticide mecoprop in a fractured moraine till and local sand aquifer (5-5.5 m depth) overlying a regional limestone aquifer (16 m depth) at Havdrup, Denmark. Alternative approaches to describe the upper boundary in the groundwater model were examined. Field-scale simulations were run to compare a uniform upper boundary condition with a spatially variable upper boundary derived from Monte-Carlo simulations with MACRO. Plot-scale simulations were run to investigate the influence of the temporal resolution of the upper boundary conditions for fluxes in the groundwater model and the effects of different assumptions concerning the macropore/fracture connectivity between the two models. The influence of within-field variability of leaching on simulated mecoprop concentrations in the local aquifer was relatively small. A fully transient simulation with FRAC3DVS gave 20 times larger leaching to the regional aquifer compared to the case with steady-state water flow, assuming full connectivity with respect to macropores/fractures across the boundary between the two models. For fully transient simulations 'disconnecting' the macropores/fractures at the interface between the two models reduced leaching by a factor 24. A fully connected, transient simulation with FRAC3DVS, with spatially uniform upper boundary fluxes derived from a MACRO simulation with 'effective' parameters is therefore recommended for assessing leaching risks to the regional aquifer, at this, and similar sites.     

Field evaluation of an acid rain-drought stress interaction

Various methods have been proposed to simulate natural field conditions for growing agricultural crops while controlling conditions to study specific environmental effects. This report briefly describes the use of moveable rain exclusion shelters (10.4 x 40.9 m) to study the results of the interaction of acid rain and drought stress on corn and soybean yields. The rain exclusion shelters are constructed of galvanized pipe framing and covered with polyethylene film. Movement is automated by a rain switch to protect crops from ambient rainfall and to treat them with simulated acid rain The facility simulates a real environment with respect to variables such as solar exposure, wind movement, dew formation, and insect exposure, while allowing careful control of moisture regimes. Soybeans and corn were treated with average rainfall amounts, and with one-half and one-quarter of these rainfall amounts (drought stress) at two levels of rainfall acidity, pH 5.6 and 3.0. While drought stress resulted in considerable yield reduction for Amsoy and Williams soybeans, no additional reduction in yield was observed with rainfall of pH 3.0, as compared to rainfall of approximately pH 5.6. Similar results were observed for one corn cultivar, Pioneer 3377. For one year of the study however, yield of B73 x Mo17 (corn) was reduced 3139 kg ha(-1) by the most severe drought, and an additional 1883 kg ha(-1) by acid rain of pH 3.0, as compared to the control (pH 5.6). Yield reduction from acidic rain was considerably less at full water rates, resulting in a significant pH by drought stress interaction. However, during the second year of the experiment, no pH effect or drought by pH interaction was observed for this cultivar. The reason for the difference in the two years was not identified.     

Pesticide transport in an aerobic aquifer with variable pH--modeling of a field scale injection experiment

Three-dimensional reactive transport simulations were undertaken to study the sorption and degradation dynamics of three herbicides in a shallow aerobic aquifer with spatially variable pH during a 216 days injection experiment. Sorption of two phenoxy acids [(+/-)-2-(4-chloro-2-methylphenoxy) propanoic acid] (MCPP) and [(+/-)-2-(2,4-dichlorophenoxy)propanoic acid] (dichlorprop) was found to be negligible. Degradation of the phenoxy acids was rapid after an initial lag phase. Degradation of the phenoxy acids could only be reproduced satisfactorily by growth-linked microbial degradation. The model fit to the field data was slightly improved if degradation was assumed to be influenced by the local pH that was observed to increase with depth ( approximately 4.5--5.7). In the observed pH-range the nitroaromatic herbicide [2-Methyl-4,6-dinitrophenol] (DNOC) was partly dissociated (pK(a)=4.31) and present in both the neutral and ionized form. The model simulations demonstrated that most of the observed spatial variation in sorption of DNOC could be explained by assuming that only the neutral form of DNOC was subject to sorption. A varying flow field was observed during the injection experiment and the model simulations documented that this most likely resulted in different migration paths for DNOC and the non-sorbing solutes. The model simulations indicated that degradation of DNOC was an important process. The degradation rate of DNOC remained constant over time and was simulated adequately by first-order kinetics. Again, the model fit to field observation was slightly improved if local pH was assumed to influence the degradation rate. Only the maximum utilization rate was estimated from the field data, while the remaining degradation parameters where successfully transferred from the laboratory study.     

Modeling of flow and contaminant transport in coupled stream-aquifer systems

This paper describes an integrated approach for modeling flow and contaminant transport in hydraulically connected stream-aquifer systems. The code, FTSTREAM, extended the capabilities of the ground-water model, FTWORK, to incorporate chemical fate and transport in streams. Flow in the stream network is modeled as an unsteady, spatially varying flow, while transport modeling is based on a one-dimensional advection-dispersion equation. In addition to sorption and decay during transport in ground water, the model incorporates volatilization, settling and decay during transport in surface water. The interaction between surface water and ground water is accommodated by a leakage term and is implemented in the model using an iterative Picard-type procedure to ensure mass conservation across the interface between the two systems. The modeling approach is used to simulate contaminant transport in the Mad River, Ohio, which is hydraulically connected to a buried valley aquifer of sand and gravel outwash. The river is a receiving stream in the upstream part of the modeled area. Downstream, heavy pumping from a municipal well field causes the river to become a loosing stream. Induced infiltration from the river is responsible for a considerable portion of the well yield. The flow and transport model, developed for this study, simulates coupling between flow in the aquifer and the river. Hypothetical sources of contamination are introduced at selected locations in the upstream portion of the aquifer. The model is then used to simulate the expected transport in both the aquifer and the stream. A series of simulations elucidates the role of the river in facilitating the transport of the hypothetical contaminants in ground water and surface water. Effect of sorption, retardation and volatilization on contaminant transport is also examined for the case of the volatile organic compounds.     

Degradation dynamics,residues and risk assessment of Dufulin enantiomers in corn plants and corn by LC/MS/MS

ABSTRACT

The degradation dynamics and terminal residues of dufulin enantiomers were investigated in two typical corn plants. A convenient and precise chiral method by high-performance liquid chromatography coupled with tandem triple quadrupole mass spectrometry (HPLC/MS/MS) using a Chiralpak IC column was developed and validated for measuring dufulin enantiomers in corn plants and corn. The two enantiomers of dufulin quickly dissipated in the corn plant, and no noticeable stereoselectivity was observed during degradation or in the final residues. After 30% rac-dufulin wettable powder with a 1- to 1.5-fold dose of the recommended value was sprayed two to three times on corn plants, the residue levels of S-(+)-dufulin and R-(-)-dufulin in corn from both sites were lower than or equal to 0.0520 mg kg^–1 on days 7, 14 and 21 after the last application. The dietary risk assessment indicated that dufulin did not exhibit obvious dietary health risks in corn samples when good agricultural practices were implemented. The findings from this study may be used to better understand the chiral profiles of dufulin in the environment and the effect of dufulin residues in corn on health.     

Migration of colloids in discretely fractured porous media: effect of colloidal matrix diffusion

Numerical simulations of colloid transport in discretely fractured porous media were performed to investigate the importance of matrix diffusion of colloids as well as the filtration and remobilization of colloidal particles in both the fractures and porous matrix. To achieve this objective a finite element numerical code entitled COLDIFF was developed. The processes that COLDIFF takes into account include advective-dispersive transport of colloids, filtration and remobilization of colloidal particles in both fractures and porous matrix, and diffusive interactions of colloids between the fractures and porous matrix. Three sets of simulations were conducted to examine the importance of parameters and processes controlling colloid migration. First, a sensitivity analysis was performed using a porous block containing a single fracture to determine the relative importance of various phenomenological coefficients on colloid transport. The primary result of the analysis showed that the porosity of the matrix and the process of colloid filtration in fractures play important roles in controlling colloid migration. Second, simulations were performed to replicate and examine the results of a laboratory column study using a fractured shale saprolite. Results of this analysis showed that the filtration of colloidal particles in the porous matrix can greatly affect the tailing of colloid concentrations after the colloid source was removed. Finally, field-scale simulations were performed to examine the effect of matrix porosity, fracture filtration and fracture remobilization on long-term colloid concentration and migration distance. The field scale simulations indicated that matrix diffusion and fracture filtration can significantly reduce colloid migration distance. Results of all three analyses indicated that in environments where porosity is relatively high and colloidal particles are small enough to diffuse out of fractures, the characteristics of the porous matrix that affect colloid transport become more important than those of the fracture network. Because the properties of the fracture network tend to have greater uncertainty due to difficulties in their measurement relative to those of the porous matrix, prediction uncertainties associated with colloid transport in discretely fractured porous media may be reduced.     

Analysis of pesticide runoff from mid-Texas estuaries and risk assessment implications for marine phytoplankton

During 1993, estuarine surface water samples were collected from the mid-Texas coast (Corpus Christi to Port Lavaca, TX). Agricultural watershed areas as well as tidal creeks immediately downstream were chosen as sampling sites along with adjoining bay sampling stations. Collections were made throughout the growing season (February to October 1993) before and after periods of significant (> 1.25 cm) rainfall. All samples were initially screened for the presence of pesticides using enzyme-linked immunosorbent assay (ELISA) test kits (EnviroGard) for triazine herbicides and carbamate insecticides. All samples were extracted and then analyzed using gas chromatography (GC) for quantification of atrazine. Only samples testing positive for carbamate insecticides via ELISA were further extracted for GC analysis to quantify aldicarb and carbofuran. Additionally, laboratory toxicity tests using phytoplankton were examined from published, peer-reviewed literature and compared with the atrazine field levels found in Texas. Results of ELISA screening indicated the presence of triazine herbicides in nearly all samples (>93%). GC analysis further confirmed the presence of atrazine concentrations ranging from <0.01-62.5 microg/L. Screening tests also found detectable levels of carbamate insecticides (aldicarb and carbofuran) that were also confirmed and quantified by GC. Comparison of measured concentrations of atrazine compared with published toxicity tests results indicated that there was a potential environmental risk for marine/estuarine phytoplankton in surface waters of Texas estuaries, particularly when the chronic nature of atrazine exposure is considered.     

Speciation of Arsenic in Ambient Aerosols Collected in Los Angeles

First-time measurements of the potentially toxic inorganic species of arsenic (arsenite arid arsenate) have been obtained in fine (<2.5 µm AD) and coarse (>2.5 µm AD) atmospheric particles in the Los Angeles area. A recently developed method that includes procedures for sample collection, preparation, and analysis was used in this study. Size-fractlonated aerosol samples were collected with a high-volume dichotomous virtual impactor that employed polytetrafluoroethylene filters. Results were obtained for the recovery of arsenic standards added to unexposed and collected filters. Data from this study, indicated that the recently developed speciation method can be used to determine concentrations of As(lll) and As(V) In atmospheric particulate matter samples.

Size-fractionated aerosol samples were collected in the city of Industry during January and February 1987. In most samples, As(lll) and As( V) were above the detection limit (approximately 1 ng m^-3 of either species) in both aerosol size fractions. A greater portion (about 75 percent) of the two species were observed in the fine particles. The As(lll)/As(V) ratio for both particle sizes was close to 1 (I.e., an equal mixture of both species). Comparison of total suspended particulate arsenic measured by the speciation method to that measured by a routine California Air Resources Board-approved procedure showed good agreement (r = 0.94), indicating both methods were approximately equivalent for the collection and analysis of aerosol arsenic.     

Kinetics of aqueous base and acid hydrolysis of aldicarb, aldicarb sulfoxide and aldicarb sulfone

The kinetics of degradation of aqueous solutions of aldicarb, aldicarb sulfoxide and aldicarb sul fone by base hydrolysis were investigated. Pseudo first order rate constants of 37 micrograms/l solutions were determined at different hydroxide concentrations by acid-base titration. Second order rate constants were calculated, and it was found that aldicarb sulfone is more sensitive to hydroxide ion concentration than aldicarb sulfoxide which is more sensitive than aldicarb. Temperature effects were determined by measuring the base hydrolysis rate constant for aldicarb sulfone at 5, 15, 20, 25, 30, and 35 degrees C. An activation energy of 15.2 +/- 0.1 kcal/mole was calculated. Addition of a neutral electrolyte decreased the rate constant for base hydrolysis. Acid catalyzed hydrolysis rate constants were also measured for aldicarb sulfone, and, as expected, the reaction was much slower. The second order (reaction) rate constant for base hydrolysis of aldicarb sulfone is 40.3 (+/- 0.5) liter mole-1min-1; for acid catalyzed hydrolysis it is 7.33 (+/- 0.06) X 10(-4) liter mole-1min-1.