Plutonium partitioning in three-phase systems with water,granite grains,and different colloids

Low-solubility contaminants with high affinity for colloid surfaces may form colloid-associated species. The mobile characteristics of this species are, however, ignored by the traditional sorption/distribution experiments in which colloidal species contributed to the immobile fraction of the contaminants retained on the solids as a result of centrifugation or ultrafiltration procedures. The mobility of the contaminants in subsurface environments might be underestimated accordingly. Our results show that colloidal species of ²³⁹Pu in three-phase systems remained the highest percentages in comparison to both the dissolved species and the immobile species retained on the granite grains (solid phase), although the relative fraction of these three species depended on the colloid types. The real solid/liquid distribution coefficients (K _s/d) experimentally determined were generally smaller than the traditional K _s/d (i.e., the K _s+c/d in this study) by ~1,000 mL/g for the three-phase systems with the mineral colloids (granite particle, soil colloid, or kaolinite colloid). For the humic acid system, the traditional K _s/d was 140 mL/g, whereas the real K _s/d was approximately zero. The deviations from the real solid/liquid K _s/d were caused by the artificially increased immobile fraction of Pu. One has to be cautious in using K _s/d-based transport models to predict the fate and transport of Pu in the environment.     

Sorption characteristics of cyromazine and its metabolite melamine in typical agricultural soils of China

A myriad of physical, chemical, and biological processes controls the fate of organic contaminants in soils. The knowledge of bioavailability of a contaminant in soil can be useful to conduct environmental risk assessment. We conducted batch equilibrium experiments to investigate the sorption of cyromazine (CA) and its metabolite melamine (MA) onto five typical soils of China belonging to suborders Ali-Perudic Ferrosols, Udic Argosols, Gleyic-Stagnic Anthrosols, Ustic Cambosols, and Udic Isohumosols. Results showed that sorption of CA and MA onto soils was linear, as indicated by the Freundlich and Langmuir models. Different sorption behaviors of CA and MA were observed on the five agricultural soils, with lgK _f values (Freundlich model) of 1.6505–2.6557 and 1.632–2.549, respectively. Moreover, the K _f values for CA and MA were positively correlated with soil organic matter (r?=?0.989, r?=?0.976) and significantly negatively correlated with pH (r?=??0.938, r?=??0.964). The free energy of sorption of CA and MA ranged from ?20.8 to ?23.0 kJ mol^?1 and ?20.8 to ?22.8 kJ mol^?1, respectively, suggesting that the sorption of CA and MA onto the soils is primarily a physical process.     

Inferences About Radionuclide Mobility in Soils Based on the Solid/Liquid Partition Coefficients and Soil Properties

To assist transport modeling in assessments of the radiological impact of a geological repository for radioactive wastes, the mobility of various elements was studied in arable and wetland soils in the Forsmark region, Sweden. Pore water and total element contents were determined for five types of unconsolidated deposits (regolith), spanning a wide range of soil properties with respect to pH and organic matter content. Two soil depths were sampled to capture element mobility in regolith layers affected and unaffected by soil-forming processes. The solid/liquid partition coefficients (K _d values) for most elements varied significantly among regolith types. For most elements, the observed variations in K _d values could be explained by variations in soil properties. For many elements, mobility increased with decreasing soil pH. The results provide a significant addition of data on radionuclide retention in soils, taking account of soil properties and processes.     

Surfactant solubilization of hydrophobic compounds in soil and water

The soil/water partition coefficient (K_d) of hexachlorobenzene (HCB) ranged from 220 1/kg to 1800 1/kg for eight soils having a wide range of physico-chemical properties. K_d normalised to soil organic carbon (K_oc) was found to be 28000 ± 4800 1/kg. Anionic surfactant dodecylsulphate (DS) present at concentrations above the critical micellar concentration (CMC) caused reductions in the apparent soil/water partition coefficient (K_d ^*) in the range of 3–26 times for most soils and up to 36–91 times for sandy soils. Below CMC, at environmentally relevant surfactant concentrations, K_d ^* was reduced by a factor of 1–13. For clay and calcareous soils significant adsorption/complexation/precipitation of DS occurred. At the lowest DS concentration this produced a two-fold increase in K_d ^*. At increasing DS concentrations this effect was shielded by the solubihzing effect from DS. Monomer (K_mn) and micellar (K_mc) surfactant/water partition coefficients for HCB were determined to be, 980 ± 190 1/kg and 21000 ± 1600 1/kg, respectively.     

Sorption comparison between phenanthrene and its degradation intermediates, 9,10-phenanthrenequinone and 9-phenanthrol in soils/sediments

The degradation intermediates of phenanthrene (PHE) may have increased health risks to organisms than PHE. Therefore, environmental fate and risk assessment studies should take into considerations of PHE degradation products. This study compared the sorption properties of PHE and its degradation intermediates, 9,10-phenanthrenequinone (PQN) and 9-phenanthrol (PTR) in soils, sediments and soil components. A relationship between organic carbon content (f_OC) and single-point sorption coefficient (log K_d) was observed for all three chemicals in 10 soils/sediments. The large intercept in the log f_OC − log K_d regression for PTR indicated that inorganic fractions control PTR sorption in soils/sediments. No relationship between specific surface area and K_d was observed. This result indicated that determination of surface area based on gas sorption could not identify surface properties for PHE, PQN, and PTR sorption and thus provide limit information on sorption mechanisms. The high sorption and strong nonlinearity (low n values) of PTR in comparison to PHE suggested that the mobility of PTR could be lower than PHE. Increased mobility of PQN compared with PHE may be expected in soils/sediments because of PQN lower sorption. The varied sorption properties of the three chemicals suggested that their environmental risks should be assessed differently.     

Sorption of Isoxaflutole Diketonitrile Degradate (DKN) and Dicamba in Unsaturated Soil

When analyzing the sorption characteristics of weakly sorbing or labile pesticides, batch methods tend to yield a high margin of error attributable to errors in concentration measurement and to degradation, respectively. This study employs a recently developed unsaturated transient flow method to determine the sorption of isoxaflutole's herbicidally active diketonitrile degradate (DKN) and dicamba. A 20-cm acrylic column was packed with soils with varied texture that had been uniformly treated with ¹⁴C-labeled chemical.

The antecedent solution herbicide in equilibrium with sorbed phase herbicide was displaced by herbicide-free water, which was infiltrated into the column. Sorption coefficients, K_d, were obtained from a plot of total herbicide concentration in the soil versus water content in the region where the antecedent solution accumulated. DKN K_d values were ～2–3 times (average K_d = 0.71 L kg^?1) greater using the unsaturated transient flow method as compared to the batch equilibration method in clay loam (K_d = 0.33 L kg^?1), but similar for the two methods in sand (0.12 vs 0.09 L kg^?1) soils. Dicamba K_d values were 3 times greater using the unsaturated transient flow method as compared to the batch equilibration method in the clay loam soil (0.38 vs 0.13 L kg^?1), however, the K_d values were the same for the two methods in the sand (～0.06 L kg^?1). This demonstrates that to determine sorption coefficients for labile hydrophilic pesticides, an unsaturated transient flow method may be a suitable alternative to the batch method. In fact, it may be better in cases where transport models have overpredicted herbicide leaching when batch sorption coefficients have been used.     

Effect of soil and sediment composition on acetochlor sorption and desorption

Background, aim, and scope  Herbicide fate and its transport in soils and sediments greatly depend upon sorption–desorption processes. Quantitative determination of herbicide sorption–desorption is therefore essential for both the understanding of transport and the sorption equilibrium in the soil/sediment–water system; and it is also an important parameter for predicting herbicide fate using mathematical simulation models. The total soil/sediment organic carbon content and its qualitative characteristics are the most important factors affecting sorption–desorption of herbicides in soil or sediment. Since the acetochlor is one of the most frequently used herbicides in Slovakia to control annual grasses and certain annual broad-leaved weeds in maize and potatoes, and posses various negative health effects on human beings, our aim in this study was to investigate acetochlor sorption and desorption in various soil/sediment samples from Slovakia. The main soil/sediment characteristics governing acetochlor sorption–desorption were also identified. Materials and methods  The sorption–desorption of acetochlor, using the batch equilibration method, was studied on eight surface soils, one subsurface soil and five sediments collected from the Laborec River and three water reservoirs. Soils and sediments were characterized by commonly used methods for their total organic carbon content, distribution of humus components, pH, grain-size distribution, and smectite content, and for calcium carbonate content. The effect of soil/sediment characteristics on acetochlor sorption–desorption was examined by simple correlation analysis. Results  Sorption of acetochlor was expressed as the distribution coefficient (K _d). K _d values slightly decreased as the initial acetochlor concentration increased. These values indicated that acetochlor was moderately sorbed by soils and sediments. Highly significant correlations between the K _d values and the organic carbon content were observed at both initial concentrations. However, sorption of acetochlor was most closely correlated to the humic acid carbon, and less to the fulvic acid carbon. The total organic carbon content was found to also significantly influence acetochlor desorption. Discussion  Since the strong linear relationship between the K _d values of acetochlor and the organic carbon content was already released, the corresponding K _oc values were calculated. Considerable variation in the K _oc values suggested that other soil/sediment parameters besides the total soil organic carbon content could be involved in acetochlor sorption. This was revealed by a significant correlation between the K _oc values and the ratio of humic acid carbon to fulvic acid carbon (C_HA/C_FA). Conclusions  When comparing acetochlor sorption in a range of soils and sediments, different K _d values which are strongly correlated to the total organic carbon content were found. Concerning the humus fractions, the humic acid carbon content was strongly correlated to the K _d values, and it is therefore a better predictor of the acetochlor sorption than the total organic carbon content. Variation in the K _oc values was attributed to the differences in distribution of humus components between soils and sediments. Desorption of acetochlor was significantly influenced by total organic carbon content, with a greater organic carbon content reducing desorption. Recommendations and perspectives  This study examined the sorption–desorption processes of acetochlor in soils and sediments. The obtained sorption data are important for qualitative assessment of acetochlor mobility in natural solids, but further studies must be carried out to understand its environmental fate and transport more thoroughly. Although, the total organic carbon content, the humus fractions of the organic matter and the C_HA/C_FA ratio were sufficient predictors of the acetochlor sorption–desorption. Further investigations of the structural and chemical characteristics of humic substances derived from different origins are necessary to more preciously explain differences in acetochlor sorption in the soils and sediments observed in this study.     

Differences in herbicide adsorption on soil using several soil ph modification techniques

Abstract

Effects of soil pH on weak acid and weak base herbicide adsorption by soil are often determined by modifying soil pH in the laboratory. Modification of soil pH with acidic or basic amendments such as HCl or NaOH can cause changes in the soil‐solution system that may affect pesticide adsorption. The partition coefficients (K_d) for atrazine and dicamba by Waukegan, Piano, and Walla Walla silt loam soils stabilized in the field at different pH levels were compared to the K_d obtained when the soil pH was adjusted with acidic or basic amendments before herbicide addition. NaOH addition to raise soil pH generally increased the soluble soil organic carbon (SSOC) concentration in solution compared to field soils at the same pH and to soil treated with Ca(OH)₂. NaOH decreased the soil solution ionic strength slightly. Acidifying soils increased the soil solution ionic strength, when compared to field soils at the same pH and had no effect on SSOC concentration. Dicamba adsorption to soil was minimal (K_d < 0.22) and not influenced by soil pH in the range of 4.1 to 6.0; adsorption by laboratory amended soils in some cases underestimated adsorption compared to nonamended soils. Atrazine adsorption increased with decreased pH in all soils, and was overestimated slightly by several laboratory treatments to reduce pH compared to adsorption by field soils. Treatments to raise the pH did not affect atrazine adsorption. Overall, herbicide adsorption differences due to pH modification were small (<30%), and were not affected by soil solution ionic strength, saturating cation, or SSOC concentration in solution.     

Sorption of chlorpyrifos and fonofos on four soils and turfgrass thatch using membrane filters

Abstract

Chemical transport in soil is a major factor influencing soil and water contamination. Four soils and turfgrass thatch, representing a wide range of organic carbon OC content were studied to determine sorption K_d and K_f parameters for the insecticides chlorpyrifos and fonofos. The batch equilibrium method was used. The concentration of insecticide was measured in the solution as well as in the solid phase to determine the most accurate sorption data. Four soils and thatch were equilibrated for 24 h at 22 ± 1^OC with aqueous insecticide solutions. Four concentrations of the insecticides, each <50% of their respective water solubilities, were selected for the experiments. After extraction with an organic solvent, the concentration of insecticides in the aqueous solution was determined by gas liquid chromatography using electron capture detection for chlorpyrifos, and nitrogen/phosphorus detection for fonofos. Data obtained were fitted to the log and simple linear form of the Freundlich equation. Mass balance Freundlich isotherm exponents n ranged between 0.82 and 0.93 for chlorpyrifos. 0.82 and 1.21 for fonofos, with r² ≥ 0.97. K_oc (percent of organic carbon %OC normalized Sorption coefficient) values were calculated by using experimentally developed K_d and K_f coefficients in relation to OC levels from 0.29 to 34.85%. K_d and K_f coefficients of both insecticides were positively correlated with OC (r² ≥ 0.96). organic matter OM (r² ≥ 0.96), and cation exchange capacity CEC (r² ≥ 0.90).     

Long-term pollution by chlordecone of tropical volcanic soils in the French West Indies: A simple leaching model accounts for current residue

Chlordecone was applied between 1972 and 1993 in banana fields of the French West Indies. This resulted in long-term pollution of soils and contamination of waters, aquatic biota, and crops. To assess pollution level and duration according to soil type, WISORCH, a leaching model based on first-order desorption kinetics, was developed and run. Its input parameters are soil organic carbon content (SOC) and SOC/water partitioning coefficient (K_oc). It accounts for current chlordecone soil contents and drainage water concentrations. The model was valid for andosol, which indicates that neither physico-chemical nor microbial degradation occurred. Dilution by previous deep tillages makes soil scrapping unrealistic. Lixiviation appeared the main way to reduce pollution. Besides the SOC and rainfall increases, K_oc increased from nitisol to ferralsol and then andosol while lixiviation efficiency decreased. Consequently, pollution is bound to last for several decades for nitisol, centuries for ferralsol, and half a millennium for andosol.     

Adsorption-desorption and leaching of pyraclostrobin in Indian soils

Pyraclostrobin is a new broad-spectrum foliar applied and seed protectant fungicide of the strobilurin group. In this paper, adsorption-desorption of pyraclostrobin has been investigated in three different soils viz. Inceptisol (sandy loam, Delhi), Vertisol (sandy clay, Hyderabad) and Ultisol (sandy clay loam, Thrissur). Effect of organic matter and clay content on sorption was also studied in Inceptisol of Delhi. Leaching potential of pyraclostrobin as influenced by rainfall was studied in intact soil columns to confirm the results of adsorption-desorption studies. The adsorption studies were carried out at initial concentrations of 0.05, 0.1, 0.5, 1 and 1.5 μg mL^?1. The distribution coefficient (K_d) values in three test soils ranged from 4.91 to 18.26 indicating moderate to high adsorption. Among the three test soils, adsorption was the highest in Ultisol (K_d 18.26), followed by Vertisol (K_d 9.87) and Inceptisol (K_d 4.91). K_F value was also highest for Ultisol soil (66.21), followed by Vertisol (40.88) and Inceptisol (8.59). S-type adsorption isotherms were observed in all the three test soils. K_d values in organic carbon-removed soil and clay-removed soil were 3.57 and 2.83 respectively, indicating lower adsorption than normal Inceptisol. Desorption studies were carried out at initial concentrations of 0.5, 1 and 1.5 μg mL^?1. Desorption was the greatest in Inceptisol, followed by Vertisol and Ultisol. Amounts of pyraclostrobin desorbed in three desorption cycles for different concentrations were 23.1–25.3%, 9.4–20.7% and 8.1–13.6% in Inceptisol, Vertisol and Ultisol respectively. Desorption was higher in clay fraction-removed and organic carbonremoved soils than normal Inceptisol. Desorption was slower than adsorption in all the test soils, indicating hysteresis effect (with hysteresis coefficient values varying from 0.05 to 0.20). Low values of hysteresis coefficient suggest high hysteresis effect indicating easy and strong adsorption, and slow desorption, of pyraclostrobin in soils. Higher hysteresis coefficient values in organic carbon removed soil (0.25–0.30) and clay fraction removed soil (0.28–0.36) as compared to normal Inceptisol soil suggest relatively weak adsorption and easy desorption of pyraclostrobin. Results of regression analysis suggest that the organic matter and pH of the soil play a major role in adsorption of pyraclostrobin. Leaching studies were carried out in intact soil columns in Inceptisol. The columns were leached with different amounts of water simulating different amounts of rainfall. The results suggest that most of the pyraclostrobin residues will remain present in the top soil layers even under high rainfall conditions and chances of pyraclostrobin moving to lower soil depth are almost negligible.     

Sulfadimethoxine and sulfaguanidine: their sorption potential on natural soils

Sulfonamides (SAs) are one of the oldest groups of veterinary chemotherapeutic agents. As these compounds are not completely metabolized in animals, a high proportion of the native form is excreted in feces and urine. They are therefore released either directly to the environment in aquacultures and by grazing animals, or indirectly during the application of manure or slurry. Once released into the environment, SAs become distributed among various environmental compartments and may be transported to surface or ground waters. The physicochemical properties of SAs, dosage and nature of the matrix are the factors mainly responsible for their distribution in the natural environment. Although these rather polar compounds have been in use for over half a century, knowledge of their fate and behavior in soil ecosystems is still limited. Therefore, in this work we have determined the sorption potential of sulfadimethoxine and sulfaguanidine on various natural soils. The influence on sorption of external factors, such as ionic strength and pH, were also determined. The sorption coefficients (K_d) obtained for the sulfonamides investigated were quite low (from 0.20 to 381.17 mL g⁻¹ for sulfadimethoxine and from 0.39 to 35.09 mL g⁻¹ for sulfaguanidine), which indicated that these substances are highly mobile and have the potential to run off into surface waters and/or infiltrate ground water. Moreover, the sorption of these pharmaceuticals was found to be influenced by OC, soil solution pH and ionic strength, with higher K_d values for soils of higher OC and lower K_d values with increasing pH and ionic strength.     

Tylosin Sorption to Silty Clay Loam Soils,Swine Manure,and Sand

The objectives of this study were to assess sorption and desorption of tylosin, a macrolide antimicrobial chemical used in swine, cattle, and poultry production, in three silty clay loam soils of South Dakota and compare soil sorption to sand and manure sorption. The silty clay loam soils, from a toposequence in eastern South Dakota, standardized sand samples, and swine manure were used in 24-h batch sorption studies with tylosin concentrations ranging from 25 to 232 μ mole/L. Desorption from soil was conducted over a four-day period. Partition coefficients, based on the Freundlich isotherm (K _f ) or K _d values, were calculated. K _f values for the silty clay loams were similar, not influenced by landscape position, and averaged 1350 with isotherm slopes ranging from 0.85 to 0.93. K _f values for sand were dependent on solution/sand ratios and pH, ranging from 1.4 to 25.1. K _d values of manure were dependent on the solution type and ranged from 840 L/kg with urine to about 175 L/kg when sorbed from water. Desorption of tylosin from each soil over the four-day period was < 0.2% of the amount added. The soils' high K _f values and low desorption amounts suggest that once tylosin is in these soils, leaching to lower depths may not occur. However, this does not preclude runoff with soil eroded particles. If tylosin reaches a sand aquifer, through bypass flow or other mechanism(s), movement in the aquifer most likely would occur.     

Mobility of radionuclides in soil/groundwater system: Comparing the influence of EDTA and four of its degradation products

The adsorption behavior of ²⁴¹Am, ⁶⁰Co, ¹³⁷Cs and ⁸⁵Sr in the presence and absence of chelating ligands (ethylenediaminetetraacetic acid, ethylenediaminediacetic acid, hydroxyethyliminodiacetic acid, iminodiaceiticacid and methyliminodiacetic acid) was investigated. Sorption affinity in the absence of chelating ligands followed: Am(III) > Co(II) > Cs(I) > Sr(II). The presence of chelating ligands generally had little effect on sorption of ⁸⁵Sr and ¹³⁷Cs with K_d values 110 and 690 mL g⁻¹, respectively. But at 0.02 M of ethylenediaminetetraacetic or hydroxyethyliminodiacetic, the K_d decreased to 5 or 63 mL g⁻¹, respectively, where thermochemical modeling indicated almost all ⁸⁵Sr is complexed with these ligands. The K_d values for ²⁴¹Am and ⁶⁰Co generally decreased with increasing chelating agent concentrations. In notable cases, the K_d values for Am increased at specific concentrations of 10⁻³ M for IDA, MIDA and 10⁻⁴ M for EDDA. This is proposed to be due to formation of a ternary surface complex.     

Acetamiprid,carbendazim, diuron and thiamethoxam sorption in two Brazilian tropical soils

Sorption of acetamiprid ((E)-N1-[(6-chloro-3-pyridyl)methyl]-N2-cyano-N1-methylacetamidine), carbendazim (methyl benzimidazol-2-ylcarbamate), diuron (N-(3,4-dichlorophenyl)-N, N-dimethyl urea) and thiamethoxam (3-(2-chloro-thiazol-5-ylmethyl)-5-methyl-[1,3,5]oxadiazinan-4-ylidene-N-nitroamine) was evaluated in two Brazilian tropical soils, Oxisol and Entisol, from Primavera do Leste region, Mato Grosso State, Brazil. To describe the sorption process, batch experiments were carried out. Linear and Freundlich isotherm models were used to calculate the K _d and K _f coefficients from experimental data. The K _d values were utilized to calculate the partition coefficient normalized to soil organic carbon (K _oc ). For the pesticides acetamiprid, carbendazim, diuron and thiamenthoxan the K _oc (mL g^{? 1}) values ranged in both soils from 98 – 3235, 1024 – 2644, 145 – 2631 and 104 – 2877, respectively. From the studied pesticides, only carbendazim presented correlation (r² = 0.82 and p < 0.01) with soil organic carbon (OC) content. Acetamiprid and thiamethoxam showed low sorption coefficients, representing a high risk of surface and ground water contamination.     

2,4-二氯苯酚在土壤中的吸附及其批实验与柱实验的分配系数比较

为了研究2,4-二氯苯酚在土壤中的吸附及比较其批实验与柱实验的分配系数Kd,开展了2,4-二氯苯酚的批实验（不同液固比条件下）和柱实验。通过分析结果可知,在批实验中,不同液固比条件下2,4-二氯苯酚达到平衡的时间类似,都在60～70 h,吸附动力学曲线符合伪二级动力学方程,吸附规律是：液固比越大,平衡吸附量增大,反应速率常数K2减小,初始吸附速率常数减小;Kd随液固比增大而降低,范围在2.91～2.12 L/kg。柱实验结果表明,2,4-二氯苯酚的贯穿曲线可以很好地用化学非平衡模型来拟合,通过模型拟合得到的Kd值要低于批实验的结果。该研究对表征2,4-二氯苯酚在环境中的行为、预测其对土壤和地下水的污染及其治理提供了依据。     

Effects of black carbon on bioturbation-induced benthic fluxes of polychlorinated biphenyls

It is unknown whether carbonaceous geosorbents, such as black carbon (BC) affect bioturbation by benthic invertebrates, thereby possibly affecting sediment-water exchange of sediment-bound contaminants. Here, we assess the effects of oil soot on polychlorinated biphenyl (PCB) mass transfer from sediment to overlying water, for sediments with and without tubificid oligochaeta as bioturbators. PCB levels were so low that toxicity to the oligochaeta played no role, whereas soot levels and binding affinity of PCBs to soot were so low that pore water PCB concentrations were not significantly affected by binding of PCBs to soot. This setup left direct effects of BC on bioturbation activity as the only explanation for any observed effects on mass transfer. Mass transfer coefficients (K_L) for benthic boundary layer transport were measured by a novel flux method using Empore™ disks as a sink for PCBs in the overlying water. For the PCBs studied (logK_ow 5.2-8.2), K_L values ranged from 0.2 to 2 cm × d⁻¹ in systems without tubificids. Systems with tubificids showed K_L values that were a factor of 10-25 higher. However, in the presence of oil soot, tubificids did not cause an increase in mass transfer coefficients. This suggests that at BC levels as encountered under field conditions, the mechanism for reduction of sediment-water transfer of contaminants may be twofold: (a) reduced mass transfer due to strong binding of the contaminants to BC, and (b) reduced mass transfer of contaminants due to a decrease in bioturbation activity.     

Leaching potential of phenylurea herbicides in a calcareous soil: comparison of column elution and batch studies

The transfer of eleven phenylurea herbicides through soil columns was investigated in laboratory conditions in order to determine leaching properties in a calcareous soil. Elution curves with distilled water were plotted after herbicide application on the soil column. Phenylurea retention by the soil indicating interactions with soil can be classified as follows: fenuron < fluometron ≤ isoproturon = monuron < metoxuron < monolinuron < metobromuron < chlorotoluron < linuron = diuron < chlorbromuron. The number and nature of halogen atoms on the phenyl ring had an important influence on leaching. Retention was higher for molecules with higher number of halogen, and it was also higher for bromine than chlorine. Column elution experiments were compared to batch experiments from which the distribution coefficients K _d were determined. According to Kendall correlation coefficients, parameter m/m _0max from column experiments was relatively well linked to K _d. In case of phenylurea, a linear relationship between K _d and m/m _0max was established.