Monitoring of Triazine and Phenylurea Herbicides in the Surface Waters of Greece

A large-scale study was implemented to monitor triazine and phenylurea herbicides in the main surface water bodies of continental Greece from October 1998 to September 1999. Samples from 10 rivers and 7 lakes were analyzed for the presence of five triazine (atrazine, cyanazine, prometryne, simazine, terbuthylazine) and five phenylurea (chlorotoluron, diuron, linuron, metobromuron, monolinuron) herbicides. The samples were extracted with C18 cartridges and analyzed by high-performance liquid chromatography–diode array detection (HPLC-DAD). The most frequently detected herbicides were atrazine, followed by prometryne, cyanazine, and simazine. The concentrations of the compounds were generally low (< 0.78 μ g/L) and are not considered harmful for the freshwater ecosystem. Most of the positive samples were taken from the water bodies of northern Greece where agricultural activity is more intense.     

Persistence of seven pesticides as influenced by soil moisture1

Abstract

Pesticides are often applied in combination, but less‐often is soil persistence measured this way. The present field and laboratory study determined relative persistence of five herbicides and two insecticides, co‐applied, as a function of three soil water contents. Losses were modeled adequately by first‐order dissipation, with no significant improvement by using a two‐compartment model. The order of persistence in a silt loam, at 25% moisture, was carbofuran < cyanazine < metribuzin = alachlor < atrazine < ethoprop < metolachlor (t_½ ranged from 7–91 days). Carbofuran degradation increased greatly from 12–25% soil moisture; atrazine was unaffected by 12–35%, whereas the remaining compounds showed limited increasing loss in wetter soil. Field‐based persistence was more variable, but generally similar to lab rankings.     

Degradation of Soil Environment in the Post‐Flooding Area: Content of Polycyclic Aromatic Hydrocarbons (PAHs) and S‐Triazine Herbicides

Impacts of flooding on the soil environment with regard to soil pollution with polycyclic aromatic hydrocarbons and s‐triazine (cyanazine, simazine, atriazine, propazine, prometryn) herbicides have been evaluated. No clear differences in the sum of the PAHs content were observed in the present studies. Only changes in the levels of individual PAHs were noted. In soils covered with flooding both at a depth of 0–20 and 20–40 high molecular weight PAHs were predominant (especially mutagenic and carcinogenic 5‐rings PAHs) whereas in non‐flooded areas, 2‐ and 3‐rings PAHs constituted over 80%. In the case of s‐triazine herbicides, no influence of flooding on the changes in their content in agriculturally used soils was noted. On the other hand, clearly lower levels of cyanazine, simazine and atriazine were not in the flooded forest soil as compared to the non‐flooded forest soil.     

Monitoring of triazine and phenylurea herbicides in the surface waters of Greece

A large-scale study was implemented to monitor triazine and phenylurea herbicides in the main surface water bodies of continental Greece from October 1998 to September 1999. Samples from 10 rivers and 7 lakes were analyzed for the presence of five triazine (atrazine, cyanazine, prometryne, simazine, terbuthylazine) and five phenylurea (chlorotoluron, diuron, linuron, metobromuron, monolinuron) herbicides. The samples were extracted with C18 cartridges and analyzed by high-performance liquid chromatography-diode array detection (HPLC-DAD). The most frequently detected herbicides were atrazine, followed by prometryne, cyanazine, and simazine. The concentrations of the compounds were generally low (< 0.78 micro g/L) and are not considered harmful for the freshwater ecosystem. Most of the positive samples were taken from the water bodies of northern Greece where agricultural activity is more intense.     

Herbicide Leaching on a Recharge Area of the Guarany Aquifer in Brazil

Abstract

The region of Ribeirão Preto City, located in Southeast of Brazil, São Paulo State, is an important sugarcane, soybean, and corn producing area with a high level of pesticides utilization. This region is also an important recharge area for groundwater supply of the Guarany aquifer. Since the past ten years atrazine, simazine, ametryn, tebuthiuron, diuron, 2,4-D, picloram, and hexazinone are the main herbicides used in this area. In order to study a possible leaching of some of these herbicides into the aquifer, surface, and groundwater samples were collected in a watershed during the years of 1996 to 2003, from different locations. To detect and quantify the herbicides a GC-MS (gas chromatograph/mass spectrometry) method was used. The response of the herbicides analyzed was linear over the concentration range of 0.02 to 2.0 μg/L. Analysis of groundwater revealed that the herbicides tebuthiuron, diuron, atrazine, simazine, and ametryn were not present in the samples. In the surface water collected in 1997, ametryn was present in two out of nine locations with concentrations ranging from 0.17 and 0.23 μg/L, which is above the allowable 0.1 μg/L according to the European safety level. The leaching potential of tebuthiuron, diuron, atrazine, simazine, 2,4-D, picloram, and hexazinone has been evaluated using CMLS-94, “Chemical Movement in Layered Soil,” as simulation model. No leaching into the depth of the water table at 40 m was found.     

Analytical methods for the determination of alachlor,metolachlor, simazine and atrazine mobility in soils

Abstract

A method for the determination of the mobility of the herbicides, alachlor, metolachlor, simazine and atrazine in soil is described . The method is based on the use of soil thin‐layer chromatography (TLC) and does not require the use of radiolabelled compounds. Soil on the TLC plate after development was separated into various bands, the material in each band was extracted with solvents and analyzed by gas chromatography.     

Degradation of soil environment in the post-flooding area: content of polycyclic aromatic hydrocarbons (PAHs) and s-triazine herbicides

Impacts of flooding on the soil environment with regard to soil pollution with polycyclic aromatic hydrocarbons and s-triazine (cyanazine, simazine, atriazine, propazine, prometryn) herbicides have been evaluated. No clear differences in the sum of the PAHs content were observed in the present studies. Only changes in the levels of individual PAHs were noted. In soils covered with flooding both at a depth of 0-20 and 20-40 high molecular weight PAHs were predominant (especially mutagenic and carcinogenic 5-rings PAHs) whereas in non-flooded areas, 2- and 3-rings PAHs constituted over 80%. In the case of s-triazine herbicides, no influence of flooding on the changes in their content in agriculturally used soils was noted. On the other hand, clearly lower levels of cyanazine, simazine and atriazine were not in the flooded forest soil as compared to the non-flooded forest soil.     

Release behavior of triazine residues in stabilised contaminated soils

This paper reports the release behavior of two triazines (atrazine and simazine) in stabilised soils from a pesticide-contaminated site in South Australia. The soils were contaminated with a range of pesticides, especially with triazine herbicides. With multiple extractions of each soil sample with deionised water (eight in total), 15% of atrazine and 4% of simazine residues were recovered, resulting in very high concentrations of the two herbicides in leachate. The presence of small fractions of surfactants was found to further enhance the release of the residues. Methanol content up to 10% did not substantially influence the concentration of simazine and atrazine released. The study demonstrated that while the stabilisation of contaminated soil with particulate activated carbon (5%) and cement mix (15%) was effective in locking the residues of some pesticides, it failed to immobilise triazine herbicides residues completely. Given the higher water solubility of these herbicides than other compounds more effective strategies to immobilise their residues is needed.     

Gas chromatography/mass spectrometry applied for the analysis of triazine herbicides in environmental waters

The excess use of triazine herbicides in agriculture causes severe contamination to the environment especially for ground water. Gas chromatography coupled with mass spectrometry (GC/MS) was used to analyze simazine, atrazine (ATR), cyanazine, as well as the degradation products of ATR such as deethylatrazine and deisopropylatrazine in environmental water samples. These compounds were baseline separated by the established GC method. The water samples were pre-concentrated by solid-phase-extraction (SPE) and analyzed by ion trap MS at sub- to low-ppt levels. Recovery of ATR by the SPE pre-concentration using a C18 cartridge was determined as 90.5 +/- 3.5%. Detection limit of the method using selected ion monitoring technique for ATR was 1.7 ppt when one liter water was analyzed. The relative analytical error for ATR fortified water samples at 200 ppt was -12.5% (n=12) with triple analysis and the relative standard deviation was 3.2%. Trace levels of ATR at 3.9 and 9.7 ppt were determined in water samples collected from a reservoir and a river in Hong Kong.     

Triazine and Metolachlor Herbicide Residues in Farm Areas of the Lower Fraser Valley,British Columbia,Canada

Crop soils, ditch sediments and water flowing from several Lower Fraser River (LFR) farm areas of British Columbia, Canada, to salmon tributary streams of that river were sampled in 2004–2005 to quantify for residues of triazine [atrazine, desethylatrazine (a transformation product of atrazine), propazine, and simazine] and metolachlor (a chloroacetamide) herbicides. Average concentrations [μg kg^?1 dry weight (d.w.)] of triazine (10,110) and metolachlor (8,910) herbicides detected in crop soils at the start (May 2004, 2005) of the growing season were about 17 and 6 times, respectively, higher than those found for both herbicide groups during (June–Sept, 2004, 2005) the growing season. In contrast, mean concentrations (μg L^?1) of triazines (0.092) and metolachlor (0.014) in permanent ditches adjacent to farms were about 7 and 28 times, respectively, lower at the start than during the growing season. Both herbicide groups in ditch sediments were detected only during the growing season at concentrations averaging about 315 μg kg^?1 d.w. The risk potential of these herbicides for non-target aquatic organisms inhabiting permanent farm ditches contiguous to tributary streams of the LFR during the growing season is evaluated and discussed.     

Pesticide contamination of ground water in the United States--a review

Over 70 pesticides have been detected in ground water. Aldicarb and atrazine along with the soil fumigants EDB and DCP and DBCP have been the pesticides most frequently detected in ground water. Atrazine concentrations have been correlated with high nitrate concentrations. The triazine herbicides, simazine and cyanazine, have also been detected in ground water. The annual amount of recharge, soil type, depth of aquifer from the surface, nitrate contamination and soil pH are important field parameters in determining ground-water contamination potential by pesticides. Pesticide leaching is reduced by proper choice of crop rotation, increasing pesticide application efficiency, and integrated pest management.     

Runoff and leaching of atrazine and alachlor on a sandy soil as affected by application in sprinkler irrigation

Abstract

Rainfall simulation was used with small packed boxes of soil to compare runoff of herbicides applied by conventional spray and injection into sprinkler‐irrigation (chemigation), under severe rainfall conditions. It was hypothesized that the larger water volumes used in chemigation would leach some of the chemicals out of the soil surface rainfall interaction zone, and thus reduce the amounts of herbicides available for runoff. A 47‐mm rain falling in a 2‐hour event 24 hours after application of alachlor (2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)‐acetamide) and atrazine (6‐chloro‐N‐ethyl‐N‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine) was simulated. The design of the boxes allowed a measurement of pesticide concentrations in splash water throughout the rainfall event. Initial atrazine concentrations exceeding its’ solubility were observed. When the herbicides were applied in 64000 L/ha of water (simulating chemigation in 6.4 mm irrigation water) to the surface of a Tifton loamy sand, subsequent herbicide losses in runoff water were decreased by 90% for atrazine and 91% for alachlor, as compared to losses from applications in typical carrier water volumes of 187 L/ha. However, this difference was not due to an herbicide leaching effect but to a 96% decrease in the amount of runoff from the chemigated plots. Only 0.3 mm of runoff occurred from the chemigated boxes while 7.4 mm runoff occurred from the conventionally‐treated boxes, even though antecedent moisture was higher in the former. Two possible explanations for this unexpected result are (a) increased aggregate stability in the more moist condition, leading to less surface sealing during subsequent rainfall, or (b) a hydrophobic effect in the drier boxes. In the majority of these pans herbicide loss was much less in runoff than in leachate water. Thus, in this soil, application of these herbicides by chemigation would decrease their potential for pollution only in situations where runoff is a greater potential threat than leaching.     

Strategies to evaluate biodegradability: application to chlorinated herbicides

The biodegradability of nitrochlorinated (diuron and atrazine) and chlorophenoxy herbicides (2,4-D and MCPA) has been studied through several bioassays using different testing times and biomass/substrate ratios. A fast biodegradability test using unacclimated activated sludge yielded no biodegradation of the herbicides in 24 h. The inherent biodegradability test gave degradation percentages of around 20–30 % for the nitrochlorinated herbicides and almost complete removal of the chlorophenoxy compounds. Long-term biodegradability assays were performed using sequencing batch reactor (SBR) and sequencing batch membrane bioreactor (SB-MBR). Fixed concentrations of each herbicide below the corresponding EC₅₀ value for activated sludge were used (30 mg L^?1 for diuron and atrazine and 50 mg L^?1 for 2,4-D and MCPA). No signs of herbicide degradation appeared before 35 days in the case of diuron and atrazine and 21 days for 2,4-D, whereas MCPA was partially degraded since the early stages. Around 25–36 % degradation of the nitrochlorinated herbicides and 53–77 % of the chlorophenoxy ones was achieved after 180 and 135 days, respectively, in SBR, whereas complete disappearance of 2,4-D was reached after 80 days in SB-MBR.     

Sorption and predicted mobility of herbicides in Baltic soils

This study was undertaken to determine sorption coefficients of eight herbicides (alachlor, amitrole, atrazine, simazine, dicamba, imazamox, imazethapyr, and pendimethalin) to seven agricultural soils from sites throughout Lithuania. The measured sorption coefficients were used to predict the susceptibility of these herbicides to leach to groundwater. Soil-water partitioning coefficients were measured in batch equilibrium studies using radiolabeled herbicides. In most soils, sorption followed the general trend pendimethalin > alachlor > atrazine～ amitrole～ simazine > imazethapyr > imazamox > dicamba, consistent with the trends in hydrophobicity (log K_ow) except in the case of amitrole. For several herbicides, sorption coefficients and calculated retardation factors were lowest (predicted to be most susceptible to leaching) in a soil of intermediate organic carbon content and sand content. Calculated herbicide retardation factors were high for soils with high organic carbon contents. Estimated leaching times under saturated conditions, assuming no herbicide degradation and no preferential water flow, were more strongly affected by soil textural effects on predicted water flow than by herbicide sorption effects. All herbicides were predicted to be slowest to leach in soils with high clay and low sand contents, and fastest to leach in soils with high sand content and low organic matter content. Herbicide management is important to the continued increase in agricultural production and profitability in the Baltic region, and these results will be useful in identifying critical areas requiring improved management practices to reduce water contamination by pesticides.     

Ultrasonic decomposition of atrazine and alachlor in water.

Abstract

The collapse of ultrasonically‐generated cavitation bubbles can result in sonochemical reactions. The kinetics of sonochemical decomposition of alachlor and atrazine in water were determined using a sonicator operating in the continuous mode at maximum output. Alachlor and atrazine solutions, 3.1 nmol L^‐1, were kept at constant temperature during the sonication. Decomposition at 30°C followed first‐order kinetics: k = 8.01 × 10^‐3 min^‐1 and 2.10 × 10^‐3 min^‐1 for alachlor and atrazine, respectively. It is not clear from the product analysis whether the decomposition was due to a thermal or free radical reaction. However, regardless of the decomposition mechanisms, the extrapolated half‐lives (86 and 330 min for alachlor and atrazine, respectively) support the potential development of ultrasonic waves to decompose herbicides in contaminated water.     

Laboratory study on leachability of five herbicides in South Australian soils

Abstract

Norflurazon, oxadiazon, oxyfluorfen, trifluralin and simazine are herbicides widely used in the vineyards of the Barossa Valley, South Australia. The leaching behaviour of norflurazon, oxadiazon, oxyfluorfen and trifluralin was investigated on four key soils in the Barossa Valley. Leaching potential on packed soil columns and actual mobility using intact soil columns were investigated. On the packed soil columns, norflurazon was the most leachable herbicide. More of the herbicides were detected in the leachates from the sandy soils (Mountadam and Nuriootpa) than from the clayey soils (Lyndoch and Tanunda). Organic matter is generally low in soils in the Barossa region. Porosity and saturated conductivity significantly affect herbicide movement and in the sandy Mountadam and Nuriootpa soils, the water flux is greater than for the higher clay content Lyndoch and Tanunda soils. Increasing the time interval between herbicide application and the incidence of “rainfall”; reduced the amounts of herbicides found in the leachates. The use of intact soil columns and including simazine for comparison showed that both norflurazon and simazine were present in the leachates. Simazine was the first herbicide to appear in leachates. Sectioning of the intact soil columns after leaching clearly demonstrated that norflurazon and simazine reached the bottom of the soil columns for all soils studied. Greater amounts of norflurazon were retained in the soil columns compared with simazine. The other herbicides were mostly retained in the initial sections of the soil columns.     

Simultaneous voltammetric determination of four triazine herbicides in water samples with the aid of chemometrics

A novel differential pulse voltammetry (DPV) method was developed for the simultaneous analysis of herbicides in water. A mixture of four herbicides, atrazine, simazine, propazine and terbuthylazine was analyzed simultaneously and the complex, overlapping DPV voltammograms were resolved by several chemometrics methods such as partial least squares (PLS), principal component regression (PCR) and principal component–artificial networks (PC–ANN). The complex profiles of the voltammograms collected from a synthetic set of samples were best resolved with the use of the PC–ANN method, and the best predictions of the concentrations of the analytes were obtained with the PC-ANN model (%RPE_T = 6.1 and average %Recovery = 99.0). The new method was also used for analysis of real samples, and the obtained results were compared well with those from the GC-MS technique. Such conclusions suggest that the novel method is a viable alternative to the other commonly used methods such as GC, HPLC and GC-MS.     

Sorption and predicted mobility of herbicides in Baltic soils

This study was undertaken to determine sorption coefficients of eight herbicides (alachlor, amitrole, atrazine, simazine, dicamba, imazamox, imazethapyr, and pendimethalin) to seven agricultural soils from sites throughout Lithuania. The measured sorption coefficients were used to predict the susceptibility of these herbicides to leach to groundwater. Soil-water partitioning coefficients were measured in batch equilibrium studies using radiolabeled herbicides. In most soils, sorption followed the general trend pendimethalin > alachlor > atrazine approximately amitrole approximately simazine > imazethapyr > imazamox > dicamba, consistent with the trends in hydrophobicity (log K(ow)) except in the case of amitrole. For several herbicides, sorption coefficients and calculated retardation factors were lowest (predicted to be most susceptible to leaching) in a soil of intermediate organic carbon content and sand content. Calculated herbicide retardation factors were high for soils with high organic carbon contents. Estimated leaching times under saturated conditions, assuming no herbicide degradation and no preferential water flow, were more strongly affected by soil textural effects on predicted water flow than by herbicide sorption effects. All herbicides were predicted to be slowest to leach in soils with high clay and low sand contents, and fastest to leach in soils with high sand content and low organic matter content. Herbicide management is important to the continued increase in agricultural production and profitability in the Baltic region, and these results will be useful in identifying critical areas requiring improved management practices to reduce water contamination by pesticides.     

Sorption-Desorption of Atrazine and Diuron in Soils from Southern Brazil

The objective of this study was to investigate the behavior of sorption and desorption of the herbicides atrazine (6-chloro-N ²-ethyl-N ⁴-isopropyl-1,3,5-triazine-2,4-diamine) and diuron [3-(3,4-dichlorophenyl)-1,1-dimethyleurea] in soil samples from a typical lithosequence located in the municipality of Mamborê (PR), southern Brazil. Five concentrations of ¹⁴C-atrazine and ¹⁴C-diuron were used for both herbicides (0.48, 0.96, 1.92, 3.84, and 7.69 mg L^?1). Sorption of both herbicides correlated positively with the organic carbon and clay content of the soil samples. Sorption isotherms were well described by the Freundlich model. The slope values of the isotherm (N) ranged from 0.84 to 0.90 (atrazine) and from 0.75 to 0.79 (diuron) for the lithosequence samples. Sorption of diuron was high regardless of the soil texture or the concentration added. The desorption isotherms for atrazine and diuron showed good fit to the Freundlich equation (R ² ≥ 0,87). Atrazine slope values for the desorption isotherms were similar for the different concentrations and were much lower than those observed for the sorption isotherms. Significant hysteresis was observed in the herbicide desorption. When the two herbicides were compared, it was found that diuron (N = 0.06–0.22) presented more pronounced hysteresis than atrazine. The results showed that, quantitatively, a greater atrazine fraction applied to these soils remains available to be leached in the soil profile, as compared to diuron.     

Herbicide leaching on a recharge area of the Guarany aquifer in Brazil

The region of Ribeir?o Preto City, located in Southeast of Brazil, S?o Paulo State, is an important sugarcane, soybean, and corn producing area with a high level of pesticides utilization. This region is also an important recharge area for groundwater supply of the Guarany aquifer. Since the past ten years atrazine, simazine, ametryn, tebuthiuron, diuron, 2,4-D, picloram, and hexazinone are the main herbicides used in this area. In order to study a possible leaching of some of these herbicides into the aquifer, surface, and groundwater samples were collected in a watershed during the years of 1996 to 2003, from different locations. To detect and quantify the herbicides a GC-MS (gas chromatograph/mass spectrometry) method was used. The response of the herbicides analyzed was linear over the concentration range of 0.02 to 2.0 microg/L. Analysis of groundwater revealed that the herbicides tebuthiuron, diuron, atrazine, simazine, and ametryn were not present in the samples. In the surface water collected in 1997, ametryn was present in two out of nine locations with concentrations ranging from 0.17 and 0.23 microg/L, which is above the allowable 0.1 microg/L according to the European safety level. The leaching potential of tebuthiuron, diuron, atrazine, simazine, 2,4-D, picloram, and hexazinone has been evaluated using CMLS-94, "Chemical Movement in Layered Soil," as simulation model. No leaching into the depth of the water table at 40 m was found.