Evolution over time of the agricultural pollution of waters in an area of Salamanca and Zamora (Spain)

A survey of the herbicides present in surface and groundwaters was conducted in 1999 in an area of the provinces of Salamanca and Zamora (Central-Western Spain) to assess the degree of pollution of the agricultural land and seasonal changes in the presence of herbicide residues. Ten sites were sampled and screened for 17 herbicides commonly used in the area; the compounds were ureas, triazines, amides, and others. A previously optimised method involving solid-phase extraction with polymeric cartridges, followed by HPLC with diode array detection, was used to monitor the herbicides. Of the 17 compounds examined, eight were found: chlorotoluron (41% of total detections), terbutryn (21%), atrazine (14%), linuron (7%), isoproturon and metolachlor (5.5% each), lenacil (4%) and metamitron (2%). Of the detections, 66% corresponded to river water samples (three sites). The herbicides found in groundwaters (seven sites) were: chlorotoluron, atrazine, terbutryn, linuron, and isoproturon, all of which are classified as probable or transient leachers in Europe. The temporal evolution of the herbicide content in river waters shows that the observed pollution is a function of time and is related to the application and use of the herbicides. By contrast, the pollution found in groundwaters was lower than that seen in surface waters, except that due to chlorotoluron, which, additionally, remained almost constant throughout the study period.     

Sorption of chlorinated C1- and C2-hydrocarbons and monocyclic aromatic hydrocarbons on sea sediment

The sorption of chlorinated C₁- and C₂-hydrocarbons and monocyclic aromatic hydrocarbons on sea sediment was studied with a miscible displacement technique. Detection was done either by on-line UV-detection or off-line GC-analysis. Equilibrium partitioning coefficients between the salt water phase and the marine sediment were determined for 11 compounds by fitting their breakthrough curves to a local sorption equilibrium model. Based on the obtained partitioning coefficients and on the measurement of the organic carbon content of the sediment, the sorption into the organic carbon fraction was considered. Log K_oc data (K_oc = organic carbon-water partitioning coefficient) were calculated. A linear relationship between the log K_oc values and the log K_ow data (K_ow = octanol-water partitioning coefficient) was found (r = 0.94, n = 11). However, the sorption was lower than expected from the log K_ow data. Finally, the implications of the experimental results for the sorption behaviour of the compounds in the marine environment were evaluated. It was concluded that the sea sediment does not act as an important sink for these anthropogenic compounds.     

Toxicology and fate of Pestanal and commercial propetamphos formulations in river and estuarine sediment

To quantify the impact of organophosphate pesticides on aquatic ecosystems requires a mechanistic understanding of their behaviour in a range of environmental matrices. The objective of this study was to compare the sorption/desorption, biodegradation and toxic effects of the Pestanal grade and commercial formulation (Ectomort Centenary) of the organophosphate insecticide propetamphos in river and estuarine sediments. For both formulations, the sorption of propetamphos onto sediment was initially very rapid followed by a slower sorption phase. Similarly, the initial rate of desorption was rapid, followed by a much slower rate. In both sorption and desorption experiments, the level of sorbed propetamphos was considerably higher for the commercial formulation of propetamphos (Kd=7-11) than for the Pestanal grade (Kd=4-10). The rate of propetamphos biodegradation was sediment dependent but was most rapid where microbial activity and nutrients were the highest and sorption was the lowest. Propetamphos was more rapidly degraded in sediments under aerobic (t(1/2)=15 d) compared to anaerobic conditions (t(1/2)=19 d). However, no significant difference in the biodegradation rates of the Pestanal grade and commercial formulations of propetamphos were observed. The toxic effect of propetamphos on sediment microbial communities was significantly greater for the commercial formulation than for the Pestanal grade of propetamphos based on EC50 (21 versus 236 microg g(-1)) and EC10 values (0.3 versus 54 microg g(-1)). In conclusion, our results highlight the importance of using commercial pesticide formulations when carrying out ecotoxicological testing.     

Exploratory Analysis of the Effects of Particulate Characteristics on the Variation in Partitioning of Nonpolar Organic Contaminants to Marine Sediments

The partitioning of nonpolar organic contaminants to marine sediments is considered to be controlled by the amount of organic carbon present. However, several studies propose that other characteristics of sediments may affect the partitioning of contaminants. For this exploratory analysis, we measured 19 sediment characteristics from five marine sediments and 11 characteristics of humic acids extracted from the sediments. These characteristics included elemental composition, grain size, soot carbon, polarity indices and molar ratios. Each individual characteristic and combinations of these characteristics were then used to normalize partition coefficients (K_p) generated for three organic contaminants: lindane, fluoranthene and a tetrachlorinated biphenyl (PCB). A coefficient of variation (CV) was then calculated for each contaminant to determine which normalization characteristic (individually or in combination) resulted in the lowest variability in partitioning between study sediments. For lindane and the PCB, normalization by the amount of sediment organic carbon resulted in the lowest variability in partition coefficients with CVs of 16.2% and 37.7%, respectively. However, normalization of fluoranthene by silt content resulted in lower CVs than those generated by organic carbon normalization: 31.0% vs. 37.6%. Normalization of contaminants K_p's by combined values of sediment characteristics resulted in lower CVs but only by a few percent. Using humic acid characteristics, humic organic carbon reduced variability between sediments most effectively. But only the normalized fluoranthene values had a CV (i.e., 25.4%) lower than the one based on normalization by sediment characteristics. When combined, humic acid characteristics resulted in lower CVs than normalization by individual or combinations of sediment characteristics for fluoranthene and the PCB with CVs of 19.3% and 28.7%, respectively. This analysis indicates variability associated with the partitioning of some organic contaminants to marine sediments can be further reduced when normalization by sediment characteristics other than organic carbon are utilized.     

Toxicity and bioavailability of atrazine and molinate to the freshwater fish (Melanotenia fluviatilis) under laboratory and simulated field conditions

Acute (96 h) semi-static toxicity tests were conducted by exposing the freshwater fish, Melanotenia fluviatilis, to atrazine and molinate in laboratory and river water both with and without sediment. The 96-h EC50 (imbalance) values of atrazine to M. fluviatilis ranged from 5.6 to 10.4 mg L(-1) while the corresponding values for molinate ranged from 7.9 to 14.8 mg L(-1), respectively. Atrazine was classed as having moderate toxicity while molinate had low to moderate toxicity to M. fluviatilis. Neither the presence of river water nor sediment significantly (P<0.05) reduced the bioavailability of either herbicide to M. fluviatilis. A series of other studies by the authors have found that sediment significantly (P<0.05) reduced the bioavailability of these two chemicals to a variety of organisms. Reasons for sediment having no effect for this species were examined. This lack of effect by sediment is most likely due to the relative rates of absorption into the fish and adsorption onto the sediment. However, contributions to this outcome by resuspended sediment, contaminated food and a combined effect of the herbicides and sediment could not be excluded.     

Assessment of olive cake as soil amendment for the controlled release of triazine herbicides

Organic matter-rich agricultural by-products are being produced in huge quantities and can be applied to soil as a disposal strategy. The application of two different rates (2 and 8% w/w) of olive cake to a Mediterranean calcareous soil resulted in an increased sorption of four triazine herbicides, which was higher for the more hydrophobic compounds (terbuthylazine and prometryn) and lower for the more polar ones (simazine and cyanazine). However, when the sorption coefficients were normalised to the total soil organic carbon (K(oc)), the results did not significantly differ between simazine and cyanazine which is an indication that the olive cake did not exert different sorption capacity for both compounds. On the contrary, K(oc) values for terbuthylazine and prometryn increased in the amended soils. Our results from experiments using mixtures of several pesticides suggest that competition for sorption sites resulted in a decrease of herbicide sorption. Desorption was hysteretical both for the amended and unamended soils, but the addition of olive cake at the highest dose diminished desorption of most of the herbicides. In conclusion, the addition of olive cake behaves as a promising method for reducing the risk of groundwater pollution by pesticides.     

Fate and enhancement of atrazine biotransformation in anaerobic wetland sediment

We examined fate and anaerobic microbial transformation/degradation characteristics of atrazine in wetland sediment receiving wastewater from a local sugar mill. Well-known metabolites/intermediates of atrazine were not detected except hydroxyatrazine. Atrazine adsorbed on the sediment linearly with a distribution coefficient of 9.979 ml/g. Although we did not obtain a direct proof of atrazine mineralization, the values of observed yield of total NH₃-N were comparable to the theoretical values suggesting the biodegradation of atrazine to its end products of NH₃ and CO₂. Only about 20% of atrazine was biotransformed to non-triazine species, possibly to the mineral end products, after 38 weeks of incubation in the sample reactors without organic amendments, with methanol and sodium acetate. Acetic acid appeared to enhance the biotransformation of atrazine (both in aqueous and sediment phases) if one only measured the parent atrazine compound alone. However, a comprehensive analysis of atrazine and its metabolites/intermediates showed that most of the disappeared atrazine existed as hydroxyatrazine. Glucose improved the wetland sediment's removal rate of the triazine species.     

Herbicides and herbicide degradates in shallow groundwater and the Cedar River near a municipal well field, Cedar Rapids, Iowa

Water samples were collected near a Cedar Rapids, Iowa municipal well field from June 1998 to August 1998 and analyzed for selected triazine and acetanilide herbicides and degradates. The purpose of the study was to evaluate the occurrence of herbicides and herbicide degradates in the well field during a period following springtime application of herbicides to upstream cropland. The well field is in an alluvial aquifer adjacent to the Cedar River. Parent herbicide concentrations generally were greatest in June, and decreased in July and August. Atrazine was most frequently detected and occurred at the greatest concentrations; acetochlor, cyanazine and metolachlor also were detected, but at lesser concentrations than atrazine. Triazine degradate concentrations were relatively small (< 0.50 microg/l) and generally decreased from June to August. Although the rate of groundwater movement is relatively fast (approx. 1 m per day) in the alluvial aquifer near the Cedar River, deethylatrazine (DEA) to atrazine ratios in groundwater samples collected near the Cedar River indicate that atrazine and DEA probably are gradually transported into the alluvial aquifer from the Cedar River. Deisopropylatrazine (DIA) to DEA ratios in water samples indicate most DIA in the Cedar River and alluvial aquifer is produced by atrazine degradation, although some could be from cyanazine degradation. Acetanilide degradates were detected more frequently and at greater concentrations than their corresponding parent herbicides. Ethanesulfonic-acid (ESA) degradates comprised at least 80% of the total acetanilide-degradate concentrations in samples collected from the Cedar River and alluvial aquifer in June, July and August; oxanilic acid degradates comprised less than 20% of the total concentrations. ESA-degradate concentrations generally were smallest in June and greater in July and August. Acetanilide degradate concentrations in groundwater adjacent to the Cedar River indicate acetanilide degradates are transported into the alluvial aquifer in a manner similar to that indicated for atrazine and DEA.     

Removal of PCNB from aqueous solution by a fungal adsorption process

Removal of PCNB from aqueous solutions by fungal mycelia was studied. Adsorption of the fungicide by dead biomass of M. racemosus, R. arrhizus and S. cyanescens was determined and compared with sorption on isolated cell walls of these three strains. Biosorptive uptake capacities are described by Freundlich equations of the form Qe=Kf·Cnfe. Measured values of Kf and nf indicate significant differences in the curve shapes and sorption capacities between the three species. Better performances were revealed by M. racemosus and R. arrhizus. Sorption of PCNB by cell walls alone was lower and statistically different from sorption by heat-killed mycelia thus corroborating that biosorption involved both uptake by the cell walls and by other cellular components.     

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.     

Removal of neutral chloroacetamide herbicide degradates during simulated unit processes for drinking water treatment

Four chloroacetamide herbicides and 20 neutral chloroacetamide derivatives (known to occur as their environmental degradates) were subjected to simulated drinking water treatment (coagulation, oxidation and adsorption). Coagulation with alum and ferric chloride, at doses for optimum turbidity removal, provided little to no (<10%) removal of parent herbicides or neutral degradates. Chlorination with 6 mg/L applied free chlorine for 6 h was able to achieve 100% removal of those degradates lacking an acetanilide substituent; compounds possessing this functional group exhibited low (0–16%) removal efficiencies. Products were generally not identified, except in the case of dimethenamid and its deschloro degradate, both of which formed a single ring-chlorination product on their ready reaction (84% and 96% removal, respectively) with aqueous chlorine species. Treatment with ozone at an applied dose of 3 mg/L for 30 min proved effective (60–100%) at transforming all of the compounds under investigation to unidentified products. The parent herbicides and neutral degradates underwent adsorption by powdered activated carbon (PAC). Adsorption capacities (Freundlich K constants) correlated with K_ow values.     

Adsorption and desorption of polydimethylsiloxane, PCBs, cadmium nitrate, copper sulfate, nickel sulfate and zinc nitrate by river surface sediments

An investigation into the adsorption and desorption of polydimethylsiloxane, PCBs, cadmium nitrate, copper sulfate, nickel nitrate and zinc nitrate by river sediments was carried out using either a flow-through system or a semi-static system. The material balance in the sediment compartment could be explained by the equation, dCs/dT= K1Cw-K2Cs. The adsorption rate constants (K1), desorption rate constants (K2) and concentration factors (K1/K2) were calculated. For hydrophobic chemicals, the K1's were independent of water solubility, but the K2's were relatively related to water solubility. For both hydrophobic chemicals and heavy metals, the concentration factors per fraction organic carbon were similar to the soil sorption coefficients (Koc), expressed on a organic carbon basis.     

Isotopic exchangeability as a measure of the available fraction of the human pharmaceutical carbamazepine in river sediment

Cabamazepine (CBZ), an antiepileptic pharmaceutical compound, is a pollutant of aquatic ecosystems entering via wastewater treatment plants that is considered to be persistent to degradation. An isotope exchange technique was employed using radiolabelled CBZ as a model compound, to determine the amount of isotopic exchangeability of CBZ in river sediment. The amount of isotopically exchangeable CBZ was used as an estimate of the extent of desorption hysteresis in solution from river sediment, including a treatment where the sediment was amended with black carbon. The isotopically exchangeable CBZ was measured by equilibrating ¹²C-CBZ with sediment for 0 to 28 days followed by a 24 hour equilibration with ¹⁴C-CBZ at the end of the incubation period. The isotopically exchangeable fraction of CBZ decreased over time in the sediment, particularly following amendment with black carbon. This has important implications for the fate of CBZ, which, apart from being resistant to degradation, is constantly released into aquatic ecosystems from wastewater treatment plants. This study demonstrates the availability of a relatively quick and simple alternative to batch desorption techniques for the assessment of the available fraction of organic compounds in sediments following their release into aquatic ecosystems.     

Pesticides in Portuguese surface and ground waters

Pesticides used in Portuguese agricultural areas have been found in surface and ground waters. In the surface water collected in three river basins from 1983 to 1999, insecticides and herbicides were detected from the monitored pesticides, particularly atrazine, chlorfenvinphos (Z+E), alpha- and beta-endosulfan, lindane, molinate and simazine, reaching the maximum values, respectively, of 0.63, 31.6, 0.18 microg/L (alpha-endosulfan), 0.18 microg/L (beta-endosulfan), 0.24, 48 and 0.3 microg/L. In the ground water collected from the wells of seven agricultural areas from 1991 to 1998, several monitored herbicides were detected: alachlor, atrazine, metolachlor, metribuzine and simazine, reaching the maximum concentration values of 13, 30, 56, 1.4 and 0.4 microg/L, respectively. The herbicides more frequently detected were atrazine (64%), simazine (45%) and alachlor (25%). Other than these, the monitored pesticides can be present in Portuguese surface and ground waters. Therefore, to improve the analytical conditions, the use of multiresidue methods and automated techniques are desirable in future work.     

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.     

A contribution to environmental risk assessment for transport of cadmium through groundwater layers. Case study of the Sava river (near Zagreb, Croatia) region

Adsorption capacities of cadmium on aquifer material of the Sava River alluvial sediment were determined as a function of flow rate, pH and presence of organic coating using laboratory column technique. In a permeameter with constant hydrostatic pressure, a laboratory coefficient of permeability, K_l, and a specific coefficient of permeability, K_s, have been determined. The value of 28.6 Darcy for specific permeability shows that the sediment belongs to a good aquifer (permeability >1 Darcy). The adsorption capacity of cadmium at the bottom of the breakthrough curve, C_sb, of a fresh sediment at pH 5.8 varied from 0.40 to 0.45 mg g⁻¹ at axial flow rate between 98 and 501 cm h⁻¹. Capacity values of maximum adsorption, C_s, were in the range from 0.67 to 0.72 mg g⁻¹. This implies a significance of C_sb values in risk assessment studies concerning a discharge of cadmium into rivers and lakes and its input to groundwater layers. Distribution coefficients, K_d, were between 26.3 and 28.2 ml g⁻¹. In order to create a more reproducible column, a fraction between 125 and 250 μm was used. In that case C_s values varied from 0.25 mg g⁻¹ at pH 2.5 (organic coating present) to 1.12 mg g⁻¹ at pH 5.8 (organic coating removed).     

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.     

Phosphorus release rates from sediments and pollutant characteristics in Han River, Seoul, Korea

The Han River is 469.7-km long and drains a 26219-km(2) watershed. The sediments in the river are highly polluted due to inputs from upstream tributaries as well as partially treated municipal wastewaters that are discharged to the river. The water quality and strategy for control are important because the river is the primary drinking water supply for the City of Seoul, as well as being a major source for irrigation and industrial water. The Jamsil submerged dam partitions the river to isolate an upstream area for drinking water, but also captures sediments. Samples from four sites were studied to determine sediment pollutant concentrations and phosphorus release rates. Phosphorus tends to desorb from sediments when the concentration of overlying water is less than 1.4 mg/l. Water column P concentrations range from 0.04 to 0.1 mg/l, which suggests that sediments will act as a P source. In a series of batch experiments, P was released at approximately 15-20 mg/m(2)week in the winter (1-5 degrees C) and as much as 90 mg/m(2)week in the summer (20-24 degrees C), and is also a function of pH and dissolved oxygen concentration. The sediment total phosphorus concentration, which averages 833 mg/kg, is evenly distributed among non-apatite-P (33%), apatite-P (32%) and residual-P (34%). An equilibrium model is proposed to describe release rate.     

Sorption and desorption behaviours of 2,4‐D and glyphosate in calcareous soil from Antalya,Turkey

2,4‐Dichlorophenoxyl acetic acid (2,4‐D) and glyphosate are used extensively as a herbicide in vicinity of Antalya, Turkey. Laboratory batch experiments were conducted to investigate the sorption isotherm and sorption‐desorption characteristics of 2,4‐D and glyphosate. Results indicated that degree of sorption of glyphosate was approximately 50 times higher than 2,4‐D (K_d= 34.43 vs. 0.66 L/Kg). The sorption of 2,4‐D and glyphosate was described by linear and rate‐limited processes for soil. Organic carbon content was most likely responsible for sorption behaviour of 2,4‐D and glyphosate. The rapid desorption can be attributed to soft carbon fraction (humic/fluvic acid and lipids) whereas slower desorption can be responsible by hard carbon fraction (black carbon, kerogen) of soils that led to chemically nonideal behaviour (hysteresis). Sorption of 2,4‐D was low due to most likely deactivation of organic carbon surfaces by excess carbonate fraction, whereas strong binding of glyphosate onto organic carbon causing high sorption behaviour.     

A multi-component statistic analysis for the influence of sediment/soil composition on the sorption of a nonionic surfactant (Triton X-100) onto natural sediments/soils

The contents of soil/sediment organic carbon and clay minerals (i.e. montmorillonite, kaolinite, illite, gibbsite and 1.4 nm minerals) for 21 natural soil/sediment samples and the sorption of Triton X-100 on these samples were determined. A multi-component statistic analysis was employed to investigate the importance of soil/sediment organic matters and clay minerals on their sorption of Triton X-100. The sorption power of soil/sediment composition for Triton X-100 conforms to an order of montmorillonite>organic carbon>illite>1.4 nm minerals (vermiculite+chlorite+1.4 nm intergrade mineral)>kaolinite. The sorption of Triton X-100 on a montmorillonite, a kaolinite and a humic acid were also investigated and consistent with the result of multi-component statistic analysis. It is clear that the sorption of Triton X-100 on soils or sediments is the combined contribution of soil/sediment organic matters and clay minerals, which depended on both the contents of soil/sediment organic matters and the types and contents of clay minerals. The important influence of illite on the sorption of nonionic surfactants onto soils/sediments is suggested and demonstrated in this paper. Surfactants for aquifer remediation application may be more efficient for the contaminated soils/sediments that contain little clay minerals with 2:1 structure because of the less sorption of nonionic surfactants on these soils/sediments.