Sampling and analytical methods were developed to examine the input of various pesticides on noncultivated areas of the FAM (Research Network on Agroecosystems) Research Station Scheyern. Off-target drift from pesticide application on nearby cultivated land, as well as input due to long-range atmospheric transport, were measured. The wet deposition was determined by a cooled wet-only sampler. Bulk samplers and specially designed samplers with glass-fiber surface were used for total deposition measurements. Analysis of pesticides was carried out using liquid/liquid or solid-phase extraction and high performance liquid chromatography-UV (HPLC-UV) or gas chromatography-nitrogen/phosphorus-sensitive detector/MS (GC-NPD/MS) detection. Obtained results demonstrated that for several compounds, total deposition, i.e. the sum of wet and dry deposition, was marginally higher than wet deposition alone. In contrast, total deposition data of pesticides having been applied near the sampling site exceeded wet deposition values by orders of magnitude. In addition to direct drift, determined as droplets depositing near pesticide application areas, an indirect drift represented by particle-associated or gaseous transport was observed, both of which contributed considerably to total deposition. Therefore, to determine the input of pesticides to nontarget areas in the close vicinity of pesticide application, direct and indirect drift, and background deposition must be considered.

The adsorption–desorption behaviour of seven pesticides and metabolites with different physiochemical properties in sediments of the Teufelsweiher pond (area: 3155m2, depth: 0.3–1.3m) in Southern Germany has been studied employing a batch technique. Atrazine and bifenox, which have been detected in the pond sediments, showed different competitive effects: the adsorption of the relatively weak sorbing atrazine was slightly reduced in the presence of the stronger adsorbing bifenox, whereas the sorption of bifenox was less affected by competition of atrazine at a concentration range of 1–5mgl−1. The desorbed amounts of aged atrazine and bifenox residues were two or three orders of magnitude smaller than in other experiments with the same sediment recently incubated with these pesticides. In addition, the apparent desorption coefficients (Kfapp) of the aged residues were approximately 3 and 16 times higher than those of recent incubations with atrazine and bifenox, respectively. This time-dependent desorption strongly suggests that the concentrations of atrazine and bifenox in natural waters are likely to be substantially lower than those predicted from laboratory-determined desorption coefficients. The dissolved organic carbon (DOC) also exhibited a significant effect on pesticide adsorption–desorption behaviour. The pesticides can be bound to DOC resulting in higher total concentrations of pesticides in the pore-water and a decreased Kd. This “solubilization effect” may be important for enhancing the desorption and facilitating the transport of contaminants in the aquatic environment.

The concentrations of polycyclic aromatic hydrocarbons (PAHs) were measured both in pore water and solid sediment isolated from the Teufelsweiher pond, a small aquatic ecosystem in Upper Bavaria (Germany) from 1992 to 1994. All 16 EPA priority compounds were present with mean total concentrations from 501 to 663 ng/l in the pore water and 976-1600 mu g/kg (dry weight) in the solid sediment. Fluoranthene and pyrene were the dominant compounds and accounted for 21-28% of the total PAHs, the ratios of fluoranthene/pyrene and phenanthrene/anthracene ranging from 1.61-2.86 and 0.86-1.57, respectively. These results suggest that the main sources of PAHs are incomplete combustion processes of fossil fuel; the compounds are then transported into the Teufelsweiher by deposition and runoff. The distribution of PAH concentrations exhibit a pronounced dependence on both particle size and organic matter content of the sediment: two fractions (<6.3 mu m and 63-200 mu m), containing higher contents of organic matter, trapped more PAHs compared with other fractions. The dissolved organic carbon (DOC) in the pore water is mostly responsible for lower K-OC' in situ measured compared with the estimated K-OC. The spatial and temporal variations of PAH concentrations are also discussed.

Sediment adsorption–desorption batch technique studies of seven pesticides and metabolites with different physiochemical properties, that have been recently applied in agriculture in Germany were performed with sediment samples from the Teufelsweiher pond (area: 3155m2, depth: 0.3–1.3m) in Southern Germany. Sorption kinetics exhibited two phenomena: an immediate rapid sorption (<4h) followed by a slow sorption process over a long period of time (two to four days). Sorption isotherms could be well described by the Freundlich equation in a nonlinear form (1/n<1) for all seven compounds. The Freundlich coefficient (Kf) and Freundlich constant (1/n) appeared to be closely related to the physiochemical properties of the compounds. With increasing pesticide hydrophobicity (higher Kow, lower solubility) their adsorption was stronger and faster, their desorption much less effective and incomplete even after a long equilibration time. This hysteresis phenomenon was attributed to both sediment–particle size and organic matter content, which also controlled the pesticide distribution to the particle-size fractions. This distribution exhibited a bimodal behavior: both, the smaller particles (clay, fine silt, <6.3μm) as well as the larger particles (fine sand, 63–200μm) showed the most effective sorption of pesticides. In addition, the pH also exhibited a considerable effect on the sorption behavior of the pesticides.

Within the scope of the joint research project “Research Network on Agroecosystems Munich (FAM)” in Scheyern, Upper Bavaria, Germany, the concentration and distribution of pesticides were studied in sediment samples in order to elucidate their fate in the aquatic environment. Of seven recently applied pesticides, only atrazine, bifenox and their metabolites were measured both in the solid sediment and the proewater isolated from the Teufelsweiher pond (area 3155 m2, depth 0.3–1.3 m) near Scheyern from 1992 to 1994. The mean total concentrations ranged from 33–76 ng litre−1 in the porewater and 1.3–4.9 μg kg−1 in the solid sediment for atrazine and 9.5–23 ng litre−1 and 4.1–18.3 μg kg−1 for bifenox, respectively. They exhibited a small spatial but obviously no temporal variation. This variation depends on the sediment particle-size distribution, because the highest pesticide concentrations were found in both the smallest ( < 6.3 μm) and the largest fraction (63–200 μm). The organic matter content of the sediment contributes mainly to this concentration distribution. In addition, comparing the in situ measured Koc with the Koc determined in the laboratory, the generally lower Koc values indicate that dissolved organic carbon (DOC) adsorbs pesticides, resulting in a higher total concentration in the porewater than in the absence of DOC. This “solubilization effect” may increase pesticide remobilization and availability in the aquatic environment. Atrazine and bifenox were mainly transported by runoff from the inclined areas nearby into the Teufelsweiher, but their transport pattern and metabolism schemes show some differences according to the different physiochemical properties.

In this paper the degradation of atrazine, deethylatrazine and isoproturon by UV and UV-activated hydrogen peroxide is described. Photolysis with an ozone-generating low pressure mercury lamp (emissions at 254 nm and 185 nm) provides the fastest degradation in all cases (initial concentration of all pesticides: 0,046 μmol/L). Degradation depends on hydroxyl radicals formed by photolysis of water. Hydrogen peroxide, however, acts as a scavenger for hydroxyl radicals and thus decreases degradation by ozone-generating UV sources. If an ozone-free radiation source (monochromatic emission at 254 nm) is used degradation rates of photolysis are much lower than by using an ozone-generating radiation source. Although this effect was observed for all three compounds it appears to be most significant in the case of isoproturon. Addition of hydrogen peroxide enhances the degradation rate which is caused by formation of hydroxyl radicals during photolysis of H 2 O 2 . Finally a degradation pathway of isoproturon is postulated based on investigations of metabolites by HPLC.

The concentration and distribution of PAHs were determined in soil, surface water, sediments, and groundwater of the experimental farm of the research network “Forschungsverbund Agrarökosysteme München” (FAM), part of a rural region in Bavaria, Germany. Analytical procedures include ultrasonication, solid phase extraction, liquid-liquid extraction, HPLC and fluorescence detection. Fifteen common PAHs were usually found in low concentrations in the examined compartments. The distribution of total PAHs in surface soils of 15 sampling sites in the area was not uniform. It could be demonstrated that there were high concentrations in valleys and low concentrations on top of the hills, due to long-term transport of PAHs to the valleys by surface run-off. Subsurface soil was found to contain lower amounts. Tetra- to hexacyclic PAHs showed similar profiles in the subsurface soil and in the top soil, while profiles of bi- and tricyclic PAHs deviated significantly. Additionally, tetra- to hexacyclic PAHs were enriched in distinct zones in the subsurface soil and exhibited similar patterns in groundwater and aquifer material. These results indicate a transport of bi- and tricyclic PAHs mainly in the dissolved or gaseous state and a predominant particle-associated transport of tetra- to hexacyclic PAHs. This particle-bound transport increases the migration velocity of hydrophobic pollutants through the vadose zone and enhances the mobility in groundwater.

Solid phase extraction materials and techniques (C-18 EMPORE® disks, polystyrenedivinylbenzene (SDB) EMPORE® disks, C-18 BondElut cartridges and ENVI-Carb cartridges) are compared for the preconcentration of 33 basic/neutral and 10 acidic/phenolic pesticides and three metabolites in water. The efficiency of the different extraction procedures was investigated by application of appropriate multiresidue separation methods by reversed phase-high performance liquid chromatography with UV-diode-array detection. Calibrations were performed with multicomponent standard mixtures and recoveries, relative standard deviations and determination limits were calculated for comparing the described enrichment methods. Experiences made in practical application of the different techniques and materials were also considered for the final evaluation.

Organic water pollutants are decomposed by UV-activated hydrogen peroxide. Using ion chromatography, inorganic and organic anions formed by the oxidative treatment can simultaneously be determined at trace levels without any sample preparation. For identification of anionic metabolites of 2,4-dichlorophenoxyacetic acid (2,4-D), 2-nitrobenzoic acid and nitrobenzene, an ion chromatographic system with a combination of two detectors based on physically different principles, conductivity and UV absorption, is used. Hence the anionic water components can reliably be identified by two parameters: retention time and the concentration-independent specific ratio of conductivity and UV absorption response.

Dieser Beitrag geht der Frage nach, inwieweit die gegenwärtig erhebbaren Daten die Kontamination eines definierten Bodenareals hinreichend zu bewerten gestalten. Die für diese Fragestellung benötigten und erhebbaren Daten wurden tabellarisch zusammengestellt. Daraus wurde abgeleitet, welche Aussagen für die Risiko-Bewertung einer konkreten Kontaminationssituation auf einem definierten Bodenstandort getroffen werden können.