Immobilization of rapeseed press-cake in an alginate matrix for the sorption of atrazine

Due to residual oil retained within it, rapeseed press-cake has been shown to be effective for the removal of atrazine from water through an absorption mechanism. However, it is difficult to put this into practice due to the hygroscopic nature of the press-cake resulting in considerable swelling, together with the formation of a thick paste which hinders phase separation. In order to overcome this, press-cake has been immobilized in an alginate matrix. The kinetics and sorption efficiency of this immobilized press-cake to absorb the model pesticide atrazine, has been studied. The results show that the rate of atrazine removal is slower than for free press-cake, although the total amount of atrazine removed is the same (K(pc/w)=0.25). Phase separation was greatly simplified. The alginate immobilized press-cake could be dried, in order to reduce volume and weight, with no adverse effect on atrazine removal kinetics or sorption properties.     

Evaluation of pesticide uptake by Lupinus seeds

Pesticide uptake by seeds depends on the properties of the chemical, such as structure, stability, log k(ow) and diffusion rate, type of water, pH, temperature, content of organic matter and composition, and on seed characteristics such as permeability of the seed coat. The efficiency with which Lupinus angustifolius seeds retain different herbicides (simazine, atrazine, isoproturon, linuron,) and insecticides (carbaryl, fenamiphos, permethrin) was evaluated using both a batch and a continuous system. Factors which affect pesticide uptake by seeds, such as flow rate, seed biomass, pesticide concentration, contact time, pH, seed saturation and also the speed of the retention process for 17 days, were tested. L. angustifolius showed a high retention capacity for the above mentioned pesticides. The extraction of pesticides from seeds using different organic solvents, such as methanol, acetonitrile, ethyl acetate and n-hexane was evaluated and no pesticide residues were detected in any of the solvents tested. This could be attributed to the capacity of the seed to degrade the pesticides. From the results obtained, L. angustifolius seems to be a promising seed to be applied for phytoremediation of industrial effluents or contaminated water.     

Pesticides in the atmosphere of the Mississippi River Valley, part II--air

Weekly composite air samples were collected from early April through to mid-September 1995 at three paired urban and agricultural sites along the Mississippi River region of the Midwestern United States. The paired sampling sites were located in Mississippi, Iowa, and Minnesota. A background site, removed from dense urban and agricultural areas, was located on the shore of Lake Superior in Michigan. Each sample was analyzed for 49 compounds; of these, 21 of 26 herbicides, 13 of 19 insecticides, and 4 of 4 related transformation products were detected during the study, with most pesticides detected in more than one sample. The maximum number of pesticides detected in an air sample was 18. Herbicides were the predominant type of pesticide detected at every site. Detection frequencies of most herbicides were similar at the urban and agricultural sites in Iowa and Minnesota. In Mississippi, herbicides generally were detected more frequently at the agricultural site. The insecticides chlorpyrifos, diazinon, and carbaryl, which are used in agricultural and non-agricultural settings, were detected more frequently in urban sites than agricultural sites in Mississippi and Iowa. Methyl parathion was detected in 70% of the samples from the Mississippi agricultural site and at the highest concentration (62 ng/m3 air) of any insecticide measured in the study. At the background site, dacthal (100%), atrazine (35%), cyanazine (22%), and the (primarily atrazine) triazine transformation products CIAT (35%) and CEAT (17%) were detected most frequently, suggesting their potential for long-range atmospheric transport.     

Effect of soil composition and dissolved organic matter on pesticide sorption

The effect of the solid and dissolved organic matter fractions, mineral composition and ionic strength of the soil solution on the sorption behaviour of pesticides were studied. A number of soils, chosen so as to have different clay mineral and organic carbon content, were used to study the sorption of the pesticides atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine), 2,4-D ((2,4-dichlorophenoxy)acetic acid), isoproturon (3-(4-isopropylphenyl)-1,1-dimethylurea) and paraquat (1,1'-dimethyl-4,4'-bipyridinium) in the presence of low and high levels of dissolved organic carbon and different background electrolytes. The sorption behaviour of atrazine, isoproturon and paraquat was dominated by the solid state soil components and the presence of dissolved organic matter had little effect. The sorption of 2,4-D was slightly affected by the soluble organic matter in the soil. However, this effect may be due to competition for adsorption sites between the pesticide and the soluble organic matter rather than due to a positive interaction between the pesticide and the soluble fraction of soil organic matter. It is concluded that the major factor governing the sorption of these pesticides is the solid state organic fraction with the clay mineral content also making a significant contribution. The dissolved organic carbon fraction of the total organic carbon in the soil and the ionic strength of the soil solution appear to have little or no effect on the sorption/transport characteristics of these pesticides over the range of concentrations studied.     

Sorbed atrazine shifts into non-desorbable sites of soil organic matter during aging

Soil-chemical contact time (aging) is an important determinant of the sorption and desorption characteristics of the organic contaminants and pesticides in the environment. The effects of aging on mechanism-specific sorption and desorption of atrazine were studied in soil and clay slurries. Sorption isotherm and desorption kinetic experiments were performed, and soil-water distribution coefficients and desorption rate parameters were evaluated using linear and non-linear sorption equations and a three-site desorption model, respectively. Aging time for sorption of atrazine in sterilized soil and clay slurries ranged from 2 days to 8 months. Atrazine sorption isotherms were nearly linear (r(2)>0.97) and sorption coefficients were strongly correlated to soil organic carbon content. Sorption distribution coefficients (K(d)) increased with increase in age in all five soils studied, but not for K-montmorillonite. Sorption non-linearity did not increase with increase in age except for the Houghton muck soil. Desorption profiles were well described by the three-site desorption model. The equilibrium site fraction (f(eq)) decreased and the non-desorbable site fraction (f(nd)) increased as a function of aging time in all soils. For K-montmorillonite, f(nd) approximately 0 regardless of aging, showing that aging phenomena are sorbent/mechanism specific. In all soils, it was found that when normalized to soil organic matter content, the concentration of atrazine in desorbable sites was relatively constant, whereas that in non-desorbable site increased. This, and the lack of aging effects on desorption from montmorillonite, suggests that sorption into non-desorbable sites of soil organic matter is primary source of increased atrazine sorption in soils during aging.     

Soil particle-size dependent partitioning behavior of pesticides within water-soil-cationic surfactant systems

Cationic surfactants have been proposed for enhanced sorption zones to contain hydrophobic organic compound (HOC) contamination. Benzalkonium chloride (BC), a cationic surfactant, was selected to study the particle-size dependent sorption behavior of the surfactant and its role in the immobilization of two hydrophobic pesticides (atrazine and diuron) within soil-water-surfactant systems for this application. Five different soils were considered in this study. Our results showed significant particle-size dependent behavior for surfactant sorption and pesticide immobilization in the presence of the sorbed cationic surfactant. The cation exchange capacity (CEC) of the bulk soils and their size fractions (clay, silt, and sand fractions) determined BC sorption capacity. In the absence of BC the sand fractions were the least effective sorbent for the pesticides compared with silts and clays. However, at relatively low BC mass sorbed (<10,000mg/kg) to any of the soil fractions, well below sorption saturation, the sand fractions became more effective sorbents for either pesticide than the clay and silt fractions. The pesticide partitioning coefficient onto sorbed BC (K(ss)) was not constant. Particle CEC, availability of CEC sites for sorption of the cationic surfactant, and the amount of the BC sorbed determined the phase of K(ss). The maximum K(ss) occurred before BC saturation sorption capacity was reached and at different % CEC occupancy for the different size fractions. For the clay fractions, the maximum K(ss) occurred at lower % CEC occupancy ( approximately 30-40%) than for the silt and sand fractions. The maximal K(ss) for the sand fractions occurred at the highest % CEC occupancy among all fractions ( approximately 50-60%). These findings suggest that for an in situ surfactant-enhanced sorption zone it may be better to operate well below the saturation sorption of the cationic surfactant. This would enhance sorption of the HOCs onto the immobile fractions (silt and sand fractions) rather than the potentially mobile clay fractions.     

Adsorption and movement of selected pesticides at high concentrations in soils

Adsorption of 2,4-d amine, atrazine, terbacil and methyl parathion pesticides on Webster, Cecil and Eustis soils was measured at pesticide solution concentrations ranging from zero to the aqueous solubility limit of each pesticide. Measured equilibrium adsorption isotherms for nearly all soil-pesticide combinations were of nonlinear Freundlich type. The Freundlich adsorption constant (K) based on soil organic carbon was much less variable for a given pesticide among the four soils than was the K based on total soil mass. The influence of the shape of the adsorption isotherm on the movement of 2,4-d amine and atrazine through water-saturated soil columns was also examined. Pesticide effluent concentrations from soil columns were measured at two input solution concentrations (50 and 5000 μg ml⁻¹ for 2,4-d amine; 5 and 50μg ml⁻¹ for atrazine). In all cases, pesticide mobility was significantly greater for the higher concentrations. Thus, serious errors may be introduced by assuming a linear adsorption isotherm (i.e. pesticide mobility is invariant with input concentration) when predicting pesticide transport from waste disposal sites where high concentrations exist.     

Comparison of atmospheric pesticide concentrations measured at three sampling sites: local, regional and long-range transport

We present the comparison of atmospheric concentrations of eleven currently used pesticides (HCB, alpha-HCH, gamma-HCH, trifluraline, mecoprop, phosalone, atrazine, carbofuran, carbaryl, diuron and isoproturon) measured in remote (Aubure), rural (Colmar) and urban (Strasbourg) areas of Alsace and Vosges regions (cast France). Pesticides samples were collected simultaneously on two of the three sites during the summer season of 1993 and 1994, using a Hi-Vol sampler with Whatman filter paper and XAD-2 resin. The particle and gas phases were collected separately during 24 h. The relative importance of local emissions and local, regional and long distance transport on the contamination of the atmosphere in the three environments (remote, rural and urban) were investigated. To facilitate the interpretation of the results, the alpha/gamma-HCH ratio was used as a tracer of pesticide emissions.     

Partitioning of hydrophobic organic compounds within soil-water-surfactant systems

Understanding the partitioning of hydrophobic organic compounds (HOCs) within soil-water-surfactant systems is key to improving the use of surfactants for remediation. The overall objective of this study was to investigate the soil properties that influence the effectiveness of surfactants used to remediate soil contaminated with hydrophobic pesticides, as an example of a more general application for removing strongly sorbing HOCs from contaminated soils via in-situ enhanced sorption, or ex-situ soil washing. In this study, the partitioning of two commonly used pesticides, atrazine and diuron, within soil-water-surfactant systems was investigated. Five natural soils, one nonionic surfactant (Triton-100 (TX)) and one cationic surfactant (benzalkonium chloride (BC)) were used. The results showed that the cation exchange capacity (CEC) is the soil property that controls surfactant sorption onto the soils. Diuron showed much higher solubility enhancement than atrazine with the micelles of either surfactant. Within an ex-situ soil washing system, TX is more effective for soils with lower CEC than those with higher CEC. Within an in-situ enhanced sorption zone, BC works significantly better with more hydrophobic HOCs. The HOC sorption capacity of the sorbed surfactant (K(ss)) was a non-linear function of the amount of surfactant sorbed. For the cationic surfactant (BC), the maximal K(ss) occurred when around 40% of the total CEC sites in the various soils were occupied by sorbed surfactant. Below a sub-saturation sorption range (~20 g/kg), under the same amount of BC sorbed, a soil with lower CEC tends to have higher K(ss) than the one with higher CEC.     

Sorption and desorption of atrazine and diuron onto water dispersible soil primary size fractions

In this study, a low energy separation method was employed to separate water dispersible clay-, silt-, and sand-sized fractions. The batch equilibrium method was used to conduct atrazine and diuron sorption/desorption experiments with the bulk soils and their size fractions separately. A Freundlich sorption model provided the best fit for all sorption and desorption data. A mass balance calculation, taking into account the pesticide concentration differences in the size fraction and bulk soil, showed that pesticide sorption onto the different size fractions reproduces well the total amount of the pesticide sorbed onto the bulk soils. Due to their higher soil organic carbon content, the clay fractions were much more effective sorbents for the pesticides than the bulk soils, silt, and sand fractions. For all soils, the amount of the pesticide sorbed onto the clay fractions was more than 20% of the total amount of the pesticide sorbed by the bulk soils even though the clay fractions in these soils were only 5.3-14.0% (by weight). The clay fractions had the highest desorption hysteresis among all size fractions and the bulk soils, followed by silt fractions, implying the clay fractions had the strongest bound and least desorbable pesticide molecules. Our results suggest that attention should be paid to the pesticide sorbed to the smallest colloids, the water dispersible fraction, which can be potentially mobilized under field conditions, leading to wide spreading of contamination.     

Degradation and byproduct formation of parathion in aqueous solutions by UV and UV/H(2)O(2) treatment

The photodegradation of parathion in aqueous solutions by UV and UV/H(2)O(2) processes was evaluated. Direct photolysis of parathion both by LP (low pressure) and MP (medium pressure) lamps at pH 7 was very slow with quantum yields of 6.67+/-0.33x10(-4) and 6.00+/-1.06x10(-4)molE(-1), respectively. Hydrogen peroxide enhanced the photodegradation of parathion through the reaction between UV generated hydroxyl radical and parathion with a second-order reaction rate constant of 9.70+/-0.45x10(9)M(-1)s(-1). An optimum molar ratio between hydrogen peroxide and parathion was determined to be between 300 and 400. Photodegradation of parathion yielded several organic byproducts, of which the paraoxon, 4-nitrophenol, O,O,O-triethyl thiophosphate and O,O-diethyl-methyl thiophosphate were quantified and their occurrence during UV/H(2)O(2) processes were discussed. NO(2)(-), PO(4)(3-), NO(3)(-) and SO(4)(2-) were the major anionic byproducts of parathion photodegradation and their recover ratios were also discussed. A photodegradation scheme suggesting three simultaneous pathways was proposed in the study.     

Oxidation of selected organophosphate pesticides during chlorination of simulated drinking water

Ten organophosphate (OP) pesticides: phorate, disulfoton, terbufos, methidathion, bensulide, chlorethoxyfos, phosmet, methyl parathion, phostebupirim, and temephos were evaluated for their potential to undergo oxidation to their respective oxons and/or other oxidation analogues in laboratory water. Samples were collected at time intervals up to 72 h of chlorination and analyzed by both gas chromatography-mass selective detection (GC-MSD) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results show that methidathion and methyl parathion were stable in unchlorinated water, while all other OP pesticides were not stable over the 72 h exposure period. In chlorinated water, phorate and disulfoton formed stable sulfone oxons. Temephos formed stable dioxon sulfoxide and dioxon sulfone. Methidathion, bensulide, chlorethyoxyfos, methyl parathion, and phostebupirim formed stable oxons over the 72 h exposure period. Terbufos, phorate, disulfoton and temephos oxon sulfoxides; temephos sulfoxide; and phosmet oxon were initially formed but were not detected after 24 h. The data illustrate that organothiophosphate pesticides may form oxons and/or other oxidation analogues during chlorination in water treatment plants, which are persistent for at least 72 h.     

Pesticides removal from waste water by activated carbon prepared from waste rubber tire

Waste rubber tire has been used for the removal of pesticides from waste water by adsorption phenomenon. By applying successive chemical and thermal treatment, a basically cabonaceous adsorbent is prepared which has not only a higher mesopore, macropore content but also has a favorable surface chemistry. Presence of oxygen functional groups as evidenced by FTIR spectra along with excellent porous and surface properties were the driving force for good adsorption efficiency observed for the studied pesticides: methoxychlor, methyl parathion and atrazine. Batch adsorption studies revealed maximum adsorption of 112.0 mg g⁻¹, 104.9 mg g⁻¹ and 88.9 mg g⁻¹ for methoxychlor, atrazine and methyl parathion respectively occurring at a contact time of 60 min at pH 2 from an initial pesticide concentration of 12 mg/L. These promising results were confirmed by column experiments; thereby establishing the practicality of the developed system. Effect of various operating parameters along with equilibrium, kinetic and thermodynamic studies reveal the efficacy of the adsorbent with a higher adsorption capacity than most other adsorbents. The adsorption equilibrium data obey Langmuir model and the kinetic data were well described by the pseudo-first-order model. Applicability of Bangham’s equation indicates that diffusion of pesticide molecules into pores of the adsorbent mainly controls the adsorption process. Spontaneous, exothermic and random characteristics of the process are confirmed by thermodynamic studies. The developed sorbent is inexpensive in comparison to commercial carbon and has a far better efficiency for pesticide removal than most other adsorbents reported in literature.     

Pesticide exposure of non-occupationally exposed subjects compared to some occupational exposure: a French pilot study

Data about non-dietary exposure to different chemical classes of pesticides are scarce, especially in France. Our objective was to assess residential pesticide exposure of non-occupationally exposed adults, and to compare it with occupational exposure of subjects working indoors. Twenty unexposed persons, five gardeners, seven florists and nine veterinary workers living in Paris area were recruited. Nineteen residences, two greenhouses, three florist shops and three veterinary departments were then sampled. Thirty-eight insecticides, herbicides and fungicides were measured in indoor air with an air sampler for 24 h, and on hands by wiping them with isopropanol-wetted swabs. After extraction, samples were analysed by gas and high-performance liquid chromatography. Seventeen different pesticides were detected at least once in indoor air and twenty-one on the hands. An average of 4.2+/-1.7 different pesticides was detected per indoor air sample. The organochlorines lindane, alpha-endosulfan and alpha-HCH were the most frequently detected compounds, in 97%, 69% and 38% of the samples, respectively. The organophosphates dichlorvos and fenthion, the carbamate propoxur and the herbicides atrazine and alachlor were detected in more than 20% of the air samples. Indoor air concentrations were often low, but could reach 200-300 ng/m(3) in residences for atrazine and propoxur. Propoxur levels significantly differed between the air of veterinary places and other places (Kruskal-Wallis test, p<0.05) and dieldrin levels between residences and workplaces (p<0.05). There was a greater number of pesticides on hands than in air, with an average of 6.3+/-3.3 different pesticides detected per sample, the most frequently detected being malathion, lindane and trifluralin, in more than 60% of the subjects. Maximal levels (up to 1000-3000 ng/hands) were observed either in the general population or in workers, depending on the pesticide. However, no significant difference was observed between workers and general population handwipe pesticide levels. As expected, gardeners were exposed to pesticides sprayed in greenhouses. Florists and veterinary workers, whose pesticide exposure had not been described until now, were also indirectly exposed to pesticides used for former pest control operations. Overall, general population was exposed to more various pesticides and at levels sometimes higher than in occupational places. The most frequent pesticides in residences were not the same as in US studies but levels were similar. These preliminary results need to be confirmed in a greater number of residences from different parts of the country, in order to better assess pesticide exposure of the general population and its influencing factors.     

Aqueous chemistry and interactive effects on non-ionic surfactant and pentachlorophenol sorption to soil

Non-ionic surfactant addition was investigated as a method to remediate pentachlorophenol (PCP) contaminated soil. The goal was to quantify surfactant (Tergitol NP-10 (TNP10)) and PCP sorption to soil and their interactive effects under varying pH, ionic strength, and soil conditions. Up to 16,700 mg/kg of TNP10 partitioned to soil, with increasing sorption far above the critical micelle concentration (CMC) and with greater amounts of PCP present. Approximately 40-45 times more TNP10 and 20-30 times more PCP sorbed to the finer soil with higher organic matter content. Aqueous TNP10 concentrations well above the CMC (>/=5500 mg/L) were required to enhance PCP desorption from the soil. As pH increased by 0.5-0.85 units, TNP10 sorption decreased by 14-25% and PCP sorption as measured by the log of the equilibrium partition coefficient decreased by 1-1.5. A lower ionic strength of 0.03 versus 0.112 M increased PCP desorption from contaminated soil by 5-17% in the presence of TNP10. This work is relevant to designing ex situ soil washing or surfactant-aided PCP remediation.     

Investigation of the estrogenic activities of pesticides from Pal-dang reservoir by in vitro assay

Endocrine disruptors, when absorbed into the body, interfere with the normal function by mimicking or blocking the hormone system. To investigate compounds mimicking estrogen in the drinking water source of the residence of Seoul, the Pal-dang reservoir was monitored over a period of 5 years, between 2000 and 2004. Nine kinds of pesticide (carbaryl, DBCP, diazinon, fenitrothion, fenobucarb, flutolanil, iprobenphos, isoprothiolane and parathion) were found to exist in the river water sample. These compounds were detected at low concentrations in the water samples. The total concentration and those of each of these pesticides were below the permissible limits of the National Institute of Environmental Research (NIER), Korea. The estrogenic potencies of the nine pesticides were examined using an E-screen assay with MCF-7 BUS estrogen receptor (ER)-positive human breast cancer cells, with ER-negative MDA MB 231 cell lines also used to compare the results. From this, flutolanil and isoprothiolane were confirmed to have estrogenic activities as shown by the increasing MCF-7 BUS cell growth on their addition. In addition, the estrogen receptor alpha (ERalpha) protein, estrogen receptor-regulated progesterone receptor (PR) and pS2 mRNA levels on the addition of flutolanil and isoprothiolane were measured with MCF-7 BUS cells. It was observed that the levels of ERalpha protein decreased and those of the PR and pS2 genes increased on the addition of either flutolanil or isoprothiolane at concentrations of 10(-4) M, in the same manner as with the addition of 17beta-estradiol, which was used as the positive control. From these results, it was confirmed that flutolanil and isoprothiolane exhibit estrogenic activities, suggesting they might act through estrogen receptors.     

Long-term sewage sludge application and wastewater irrigation on the mineralization and sorption of 17beta-estradiol and testosterone in soils

The disposal of animal manures, wastewater and sewage sludge to agricultural land can lead to the transfer of steroid hormones like 17beta-estradiol and testosterone into soils, surface and groundwaters. The objective of this study was to investigate the effects of different site histories like wastewater irrigation and sewage sludge application on hormone mineralization and sorption in soils. Two agricultural sites with different long-term treatment histories with wastewater and sewage sludge were sampled. The mineralization of (14)C-17beta-estradiol and (14)C-testosterone was studied during incubations at 20 degrees C over three weeks. Despite the structural resemblance of both hormones the mineralization rate of 17beta-estradiol was about an order of magnitude lower than that of testosterone in all four soils, reaching 5-7% vs. 50-59%, respectively. Estradiol mineralization was significantly lower in soils with long-term wastewater irrigation than in the corresponding soil with freshwater irrigation. Pre-incubation of the soils with unlabeled hormones or application of the hormones within a wastewater matrix had only minor effects on their mineralization. The results indicate that estradiol mineralization occurs co-metabolically and is limited by sorption, whereas testosterone appears to be utilized directly by soil microorganisms. Sorption of (14)C-17beta-estradiol and (14)C-testosterone to sterile and unsterile soils was determined in batch experiments with CaCl(2) or wastewater solution with hormone concentrations of 0.13-0.0013 mug mg(-1). FREUNDLICH sorption isotherms and parameters like K(F) and log K(oc) values were used to describe the results. The K(F) values for estradiol sorption were generally about 1.2 to 1.6-fold higher than for testosterone. The SOC-normalized partition coefficients K(oc) also differ accordingly and indicate quite large differences in soil organic matter qualities relating to hormone sorption between the soils and treatments. When the hormones were added to the soil within a wastewater matrix less estradiol was sorbed in the solid phase than in the controls with pure water, thus indicating that wastewater contains soluble sorbents.     

The Degradation of Atrazine and Other Pesticides by Photolysis

Groundwaters from chalk aquifers which are used as a supply for drinking water are often contaminated with pesticides - in particular, atrazine. This paper discusses the use of an industrial-scale ultraviolet chamber to reduce the concentration of atrazine in a chalk-derived water which is used for drinking water supply. The concentration of atrazine varied between 0.1 μg/l and 0.5 μg/l, and the raw water was spiked when necessary. Results for other pesticides contaminants are also presented.
The efficiency of atrazine removal is dependent only on the energy input and is constant, regardless of the initial concentration. Hydrogen peroxide improves the efficiency of ultraviolet irradiation but requires high doses.     

Treatment of atrazine in nursery irrigation runoff by a constructed wetland

To investigate the treatment capability of a surface flow wetland at a container nursery near Portland, Oregon, atrazine was introduced during simulated runoff events. Treatment efficiency was evaluated as the percent atrazine recovered (as percent of applied) in the water column at the wetland's outlet. Atrazine treatment efficiency at the outlet of the constructed wetland during a 7-d period ranged from 18-24% in 1998 (experiments 1-3) and 16-17% in 1999 (experiments 4 and 5). Changes in total flow, or frequency and intensity of runoff events did not affect treatment. For experiment 6 in 1999, where the amount, frequency, and duration of runoff events exceeded all other experiments, treatment was compromised. For all experiments, deethylatrazine (DEA) and deisopropylatrazine (DIA) accounted for 13-21% of the initial application. Hydroxyatrazine (HA) was rarely detected in the water. Organic carbon adsorption coefficients (Koc) were determined from batch equilibrium sorption isotherms with wetland sediment, and they decreased in the order of HA > DIA > atrazine > DEA. Static water-sediment column experiments indicated that sorption is an important mechanism for atrazine loss from water passing through the constructed wetland. The results of the MPN assay indicated the existence in the wetland of a low-density population of microorganisms with the potential to mineralize atrazine's ethyl side chain.     

Spatial and temporal distribution of pesticide residues in surface waters in northeastern Greece

A monitoring study of 147 compounds in surface river waters from northeastern Greece near Greek/Bulgarian/Turkish borders was carried out during 1999-2007. Based on agricultural use eight sampling points along the rivers Ardas, Evros and Erythropotamos were set up, covering the distance from the Greek/Bulgarian borders down to the river's discharge (river's delta) in the Greek territory. In total, 88 sampling events were carried out from 1999 to 2007. Pesticides were extracted by solid-phase extraction (SPE) and analyzed by gas chromatography-mass spectrometry (GC-EI-MS) using a multiresidue in-house analytical method including pesticides belonging to different chemical classes. Aquatic risk concerning the detected pesticides was assessed on the basis of the risk quotient (RQ = PEC/PNEC). From the 28 compounds (pesticides, metabolites and caffeine) that were detected in surface waters of northeastern Greece the soil applied pesticides were the most frequently detected. High pesticide concentrations were detected within 2 months of their application. Extreme pesticide concentrations were detected in the beginning of the irrigation season or just after high rainfall events. Generally, low levels of pesticide residues were found in the first sampling point (Greek/Bulgarian borders) of all rivers, however o′,p′ DDT, o′,p′ DDE and γ-HCH were mainly detected in this sampling point regarded as cross-boundary contamination. The most commonly encountered compounds in the river waters were atrazine, DEA, alachlor, trifluralin, prometryne, molinate, carbofuran, carbaryl and diazinon. Increased loading (primary as well as secondary peaks) seemed to be a consequence of application (timing, rate, frequency) and intense rainfall during the application period. Aquatic risk assessment revealed that from the 28 compounds that were constantly detected 12 showed non-acceptable risk when median concentrations were used as PEC and 18 when extreme concentrations were used as PEC values.