Glyphosate is currently one of the most important herbicides worldwide. Its unique properties provide for a wide range of uses in agriculture but also in non-agricultural areas. At the same time, its zwitterionic nature prevents the inclusion in multi-residue analytical methods for environmental monitoring. Consequently, despite its extensive use, data on occurrence of glyphosate in the aquatic environment is still scarce. Based on existing methods, we developed a simplified procedure for the determination of glyphosate and its main metabolite aminomethylphosphonic acid (AMPA) in water samples using derivatization with fluorenylmethyl chloroformate FMOC-Cl, combined with on-line solid phase extraction and liquid chromatography-tandem mass spectrometry (LC-MS/MS) detection. This method was extensively tested on over 1000 samples of surface water, groundwater, and treated wastewater and proved to be simple, sensitive, and reliable. Limits of quantification of 0.005 μg/L were routinely achieved. Glyphosate and AMPA were detected in the vast majority of stream water samples in the area of Zurich, Switzerland, with median concentrations of 0.11 and 0.20 μg/L and 95th percentile concentrations of 2.1 and 2.6 μg/L, respectively. Stream water data and data from treated wastewater indicated that non-agricultural uses may significantly contribute to the overall loads of glyphosate and AMPA in surface waters. In the investigated groundwater samples, selected specifically because they had shown presence of other herbicides in previous monitoring programs, glyphosate and AMPA were generally not detected, except for two monitoring sites in Karst aquifers, indicating that these compounds show much less tendency for leaching.

To assess sources and magnitude of possible groundwater contamination, chemical markers have proved to be useful. A chemical that is used in everyday life, the artificial sweetener acesulfame, may be ideally suited for detection of traces of domestic wastewater in natural waters. The compound was found ubiquitously in wastewater, surface waters, and groundwater from Switzerland. Acesulfame was not eliminated in wastewater treatment plants (WWTPs), and was quite persistent in lakes, where concentrations increased with population in the catchment area and decreased with water throughflow. Highest concentrations in groundwater were observed in areas with significant infiltration of river water, where the infiltrating water received considerable discharges from WWTPs. Given the currently achieved detection limit of approx. 0.01 mu g/L, the presence of >= 0.05% wastewater can be traced in groundwater.

Nicotine is extensively metabolized in the human body to a number of compounds, which may enter natural waters via discharge of domestic wastewater. However, little is known on exposure of and potential effects on the aquatic environment In this study, two major urinary metabolites, cotinine and 3'-hydroxycotinine, as well as a further tobacco alkaloid, N-formylnornicotine, were measured in wastewater and water from Swiss lakes using an analytical procedure based on SPE and LC-MS/MS SRM with cotinine-d(3) as internal standard (LOQs, 1.0-1.5 ng/L. Typical concentrations of cotinine and 3'-hydroxycotinine were similar to 1-1 mu g/L in untreated wastewater, but clearly less in treated wastewater (similar to 0.01-0.6 mu g/L), corresponding to elimination efficiencies of 90-99%. N-Formylnornicotine, however, was found at similar concentrations in untreated and treated wastewater (0.02-0.15 mu g/L). Its apparent persistence during wastewater treatment was further confirmed by incubation experiments with activated sludge. In lakes, cotinine, 3'-hydroxycotinine, and N-formylnornicotine were detected at concentrations up to 15, 80, and 6 ng/L, respectively. Concentrations in lakes correlated with the expected anthropogenic burden by domestic wastewater (ratio population per water throughflow), demonstrating the suitability of these nicotine derivatives as hydrophilic, anthropogenic markers. In small receiving waters with significant wastewater discharges, concentrations of a few hundred ng/L may be expected. Possible ecotoxicological risks associated with such environmental concentrations, can, however, not be assessed at present as data on effects on aquatic organisms are very limited, in particular on long-term effects.

Although the use of hexachlorocyclohexane (HCH), one of the most popular insecticides after the Second World War, has been discontinued in many countries, problems remain from former production and waste sites. Despite the widespread occurrence of HCHs, the environmental fate of these compounds is not fully understood. In particular, environmental metabolites of the more persistent beta-HCH and delta-HCH have not been fully identified. Such knowledge, however, is important to follow degradation and environmental fate of the HCHs. In the present study, several hydroxy metabolites that formed during incubation of beta- and delta-HCH with the common soil microorganism Sphingobium indicum B90A were isolated, characterized, and stereochemically identified by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy (NMR). The metabolites were identified as isomeric pentachlorocyclohexanols (B1, D1) and tetrachlorocyclohexane-1,4-diols (B2, D2); delta-HCH additionally formed a tetrachloro-2-cyclohexen-1-ol (D3) and a trichloro-2-cyclohexene-1,4-diol (D4), most likely by hydroxylation of delta-pentachlorocyclohexene (delta-PCCH), initially formed by dehydrochlorination. The dehydrochlorinase LinA was responsible for conversion of delta-HCH into delta-PCCH, and the haloalkane dehalogenase LinB was responsible for the transformation of beta-HCH and delta-HCH into B1 and D1, respectively, and subsequently into B2 and D2, respectively. LinB was also responsible for transforming delta-PCCH into D3 and subsequently into D4. These hydroxylations proceeded in accordance with SN2 type reactions with initial substitution of equatorial Cls and formation of axially hydroxylated stereoisomers. The apparently high reactivity of equatorial Cls in beta- and delta-HCH toward initial hydroxylation by LinB of Sphingobium indicum B90A is remarkable when considering the otherwise usually higher reactivity of axial Cls. Several of these metabolites were detected in groundwater from a former HCH production site in Switzerland. Their presence indicates that these reactions proceed under natural environmental conditions and that the metabolites are of environmental relevance.

Many pesticides are chiral and consist of two or more enantiomers/stereoisomers, which may differ in biological activity, toxicity, effects on nontarget organisms, and environmental fate. In the last few years, several racemic compounds have been substituted by enantiomer-enriched or single-isomer compounds ("chiral switch"). In this context, the stereoselective degradation in soils is an important part of a benefit-risk evaluation, but the understanding of the environmental factors affecting the chiral preferences is limited. In this study, the stereoselective degradation of the fungicides epoxiconazole and cyproconazole was investigated in different soils, selected to cover a wide range of soil properties. The fungicides were incubated under laboratory conditions and the degradation and configurational stability of the stereoisomers were followed over time using enantioselective GC-MS with a gamma-cyclodextrin derivative as chiral selector. In alkaline and slightly acidic soils, the degradation of epoxiconazole was clearly enantioselective, whereas in more acidic soils, both enantiomers were degraded at similar rates (overall half-lives 78-184 d). The enantioselectivity, expressed as ES = (k(i) - k(j))/ (k(i) + k(j)), ranged from -0.4 in alkaline soils (faster degradation of enantiomer j) to approximately 0 in acidic soils (non-enantioselective), and showed a reasonably linear correlation with the soil pH. The four stereoisomers of cyproconazole (overall half-lives 5-223 d) were also degraded at different rates in the various soils, but only the stereoselectivities between epimers showed some correlations with pH, whereas enantioselectivities did not. Both fungicides were configurationally stable in soils, i.e., no enantiomerization or epimerization was observed. Correlations between pH and ES have previously been reported for other pesticides (metalaxyl, dichlorprop, mecoprop), but the presence or absence of such correlations is not obviously linked to the pathways of degradation. It can be assumed that different microorganisms and enzymes are involved in the primary degradation of these compounds, but on which level soil pH has an influence on ES remains to be investigated.

ABSTRACT Sphingomonas paucimobilis B90A contains two variants, LinA1 and LinA2, of a dehydrochlorinase that catalyzes the first and second steps in the metabolism of hexachlorocyclohexanes (R. Kumari, S. Subudhi, M. Suar, G. Dhingra, V. Raina, C. Dogra, S. Lal, J. R. van der Meer, C. Holliger, and R. Lal, Appl. Environ. Microbiol. 68:6021-6028, 2002). On the amino acid level, LinA1 and LinA2 were 88% identical to each other, and LinA2 was 100% identical to LinA of S. paucimobilis UT26. Incubation of chiral α-hexachlorocyclohexane (α-HCH) with Escherichia coli BL21 expressing functional LinA1 and LinA2 S-glutathione transferase fusion proteins showed that LinA1 preferentially converted the (+) enantiomer, whereas LinA2 preferred the (−) enantiomer. Concurrent formation and subsequent dissipation of β-pentachlorocyclohexene enantiomers was also observed in these experiments, indicating that there was enantioselective formation and/or dissipation of these enantiomers. LinA1 preferentially formed (3S,4S,5R,6R)-1,3,4,5,6-pentachlorocyclohexene, and LinA2 preferentially formed (3R,4R,5S,6S)-1,3,4,5,6-pentachlorocyclohexene. Because enantioselectivity was not observed in incubations with whole cells of S. paucimobilis B90A, we concluded that LinA1 and LinA2 are equally active in this organism. The enantioselective transformation of chiral α-HCH by LinA1 and LinA2 provides the first evidence of the molecular basis for the changed enantiomer composition of α-HCH in many natural environments. Enantioselective degradation may be one of the key processes determining enantiomer composition, especially when strains that contain only one of the linA genes, such as S. paucimobilis UT26, prevail.

Organic UV filters are used in personal care products such as sunscreen products, and in cosmetics, beauty creams, skin lotions, lipsticks, hair sprays, hair dyes, shampoos, and so forth. The compounds enter the aquatic environmentfrom showering, wash-off, washing (laundering), and so forth via wastewater treatment plants (WWTPs) ("indirect inputs") and from recreational activities such as swimming and bathing in lakes and rivers ("direct inputs"). In this study, we investigated the occurrence of four important organic UV filter compounds (benzophenone-3, BP-3; 4-methylbenzylidene camphor, 4-MBC; ethylhexyl methoxy cinnamate, EHMC; octocrylene, OC) in wastewater, and in water and fish from various Swiss lakes, using gas chromatographic/mass spectrometric analyses. All four UV filters were present in untreated wastewater (WWTP influent) with a maximum concentration of 19 microg L(-1) for EHMC. The data indicate a seasonal variation with influent loads higher in the warmer season (June 2002) than in the colder one (April 2002). The influent loads were in the order EHMC > 4-MBC approximately BP-3 > OC. The concentrations in treated wastewater (WWTP effluent) were considerably lower, indicating substantial elimination in the plants. 4-MBC was usually the most prevalent compound (maximum concentration, 2.7 microg L(-1)), followed by BP-3, EHMC, and OC. UV filters were also detected in Swiss midland lakes and a river (Limmat) receiving inputs from WWTPs and recreational activities. However, all concentrations were low (<2-35 ng L(-1)); no UV filters (<2 ng L(-1)) were detected in a remote mountain lake. Data from passive sampling using semipermeable membrane devices (SPMDs) supported the presence of these UV filters in the lakes and the river and suggested some potential for accumulation of these compounds in biota. SPMD-derived water concentrations increased in the order Greifensee < Zürichsee < Hüttnersee. This order is reversed from that observed for methyl triclosan, used as a chemical marker for WWTP-derived lipophilic contaminants in the lakes. This indicated inputs of UV filters from sources other than WWTPs to the lakes during summer,for example,inputs from recreational activities. Fish (white fish, Coregonus sp.; roach, Rutilus rutilus; perch, Perca fluviatilis) from these lakes contained low but detectable concentrations of UV filters, in particular, 4-MBC (up to 166 ng g(-1) on a lipid basis). 4-MBC concentrations relative to methyl triclosan were lower in fish than in SPMDs exposed in the same lakes, suggesting that 4-MBC is less bioaccumulated than expected or metabolized in fish. The lipid-based bioconcentration factor (BCF(L)) estimated from the fish (roach) data and SPMD-derived water concentrations was about 1-2.3 x 10(4) and thus approximately 1 order of magnitude lower than expected from its Kow value.

4-Methylbenzylidene camphor (4-MBC) is an important organic UV filter used in many personal care products such as sunscreens and cosmetics. After use, 4-MBC may enter the aquatic environment due to its release from skin during recreational activities (swimming, bathing) and from personal hygiene measures (washing, laundering of cloths) via wastewater treatment plants (WWTPs). In fact, 4-MBC has been detected in wastewater, in surface waters, and even in fish. 4-MBC can exist as distinct cis-(Z)- and trans-(E)-isomers, both of which are chiral. Despite the fact that stereoisomers often show a different biological behavior, the stereochemistry of 4-MBC has hardly ever been considered in environmental or biological studies. In this study, enantioselective gas chromatography-mass spectrometry (GC-MS) was used to determine the stereoisomer composition of 4-MBC. For stereoisomer assignment, the pure enantiomers of (E)-4-MBC were synthesized from (+)- and (-)-camphor. The photochemical isomerization (sunlight) of these (E)-isomers to the corresponding (Z)-isomers eventually allowed the configurational assignment of all four stereoisomers of 4-MBC. In a technical material and in a major brand sun lotion, 4-MBC was shown to consist entirely (>99%) of (E)-isomers and to be racemic (R/S, 1.00 +/- 0.02). Wastewater showed the presence of both (E)- and (Z)-4-MBC with a clear excess of (E)-isomers (E > Z). Untreated wastewater showed a nearly racemic composition (R/S= 0.95-1.09), suggesting that most if not all commercial 4-MBC is racemic. Treated wastewater indicated some excess of (R)- or (S)-stereoisomers (R/S, 0.89-1.17), likely as a result of some enantioselective (bio)degradation in WWTPs. Residues of 4-MBC in lakes and in a river with inputs from WWTPs and/or recreational activities consisted mainly of (E)-4-MBC and, with exception of one lake (Greifensee), showed a small enantiomer excess (R/S, 1.04-1.16). In Greifensee, 4-MBC showed a higher enantiomer excess (R/S, 1.70-1.83), probably as a result of more extensive biotic degradation in this lake. The analysis of 4-MBC in a small number of fish from these lakes indicated residues with nearly racemic compositions or a moderate enantiomer excess (R/S, approximately 1.0-1.2) in roach (Rutilus rutilus), whereas in perch (Perca fluviatilis) a much higher enantiomer excess (R/S, approximately 5) was observed. The data indicate that the stereoisomer composition of 4-MBC in environmental samples is not only a function of initial product composition but is also modified by enantioselective processes in lakes and biota (fish).

Consumer care products often contain UV filters, organic compounds which absorb ultraviolet light. These compounds may enter surface waters directly (when released from the skin during swimming and bathing) or indirectly via wastewater treatment plants (when released during showering or washed from textiles). Predicted and measured UV filter concentrations were compared in a regional mass balance study for two Swiss lakes: Lake Zurich, a typical midland lake which is also an important drinking water resource, and Hüttnersee, a small bathing lake. Both lakes are extensively used for recreational activities and considerable direct input of UV filters is thus expected. This input was estimated from the number of visitors at swimming areas around the lakes and a survey of the usage of sunscreen products among these visitors. Possible additional indirect input via wastewater treatment plants was not considered in this study. The quantitatively most important UV filters, as indicated by the survey data, ethylhexyl methoxycinnamate, octocrylene, 4-methylbenzylidene camphor, butyl methoxydibenzoylmethane, and benzophenone-3, all lipophilic compounds, were selected for analysis by gas chromatography–mass spectrometry. Concentrations of individual UV filters in water from Lake Zurich were low, ranging from <2 ngl−1 (detection limit) to 29 ngl−1, and somewhat higher at Hüttnersee, ranging from <2 to 125 ngl−1, with the highest concentrations found in summer, consistent with direct inputs to the lakes during this time. The concentrations were clearly lower than predicted from input estimates based on the surveys. This may be in part due to (i) an overestimation of these inputs (e.g. less than the 50% wash-off of UV filters assumed to occur during swimming), and (ii) some removal of these compounds from the lakes by degradation and/or sorption/sedimentation. UV filters were also detected in semipermeable membrane devices (SPMDs) deployed at Lake Zurich and Greifensee, another midland lake, at concentrations of 80–950 ngSPMD−1, confirming the presence of the compounds in surface waters and indicating a certain potential for bioaccumulation. SPMD-derived water concentrations were in the range of 1–10 ngl−1 and thus corresponded well with those determined in water directly. No UV filters were detected above blank levels in SPMDs deployed at a remote mountain lake used for background measurements.

The Locking Compression Plate (LCP) system offers a number of advantages in fracture fixation combining angular stability through the use of locking screws with traditional fixation techniques. This makes the implant particularly suitable for use in poor bone stock and complex joint fractures, especially in the epimetaphyseal area. However, the system is complex, requiring careful attention to biomechanical principles, and a number of potential pitfalls need to be considered. These pitfalls are illustrated in the 4 cases described herein, in which treatment was unsuccessful due to implant breakage or loosening. In each case, treatment failure could be attributed to the choice of an inappropriate plate and/or fixation technique, rather than to the features of the Locking Compression Plate system itself. Such experiences highlight the importance of detailed understanding of the biomechanical principles of plate fixation as well as careful preoperative planning for the successful use of the Locking Compression Plate system.

Many organic compounds (natural and synthetic) possess at least one element of asymmetry, leading to the presence of stereoisomers. Whereas synthetic compounds are most often produced as mixtures of stereoisomers, natural compounds typically are single isomer compounds. Stereoisomers have similar (diastereomers) or identical (enantiomers) physical-chemical properties, but often differ significantly with respect to biological properties such as toxicity and environmental behavior. However, the differences in biological properties of individual stereoisomers; of synthetic organic compounds are often not well understood. This is, in part, due to lack of awareness of these differences, lack of legal requirements (e.g., in pesticide registration) and limited availability of appropriate analytical methods. Studies on individual stereoisomers of chiral compounds require special (enantioselective) analytical methods. Separation of enantiomers by HPLC, GC, and CE is achieved by addition of so-called "chiral selectors" such as cyclodextrins to the stationary or mobile phase. Separation of chiral compounds into two or more peaks increases the need for very selective detection, particularly in complex matrices. Therefore, enantioselective separation is often coupled to mass spectrometric detection. Because interactions between target compound and chiral selector cannot be predicted, the choice of a suitable selector often is not an easy task and must be done on a case-by-case basis. Single isomer or isomer enriched reference compounds, which are often not commercially available, can either be prepared by stereoselective synthesis or by semipreparative enantioselective (liquid) chromatography. In both cases, the absolute configuration must then be determined by X-ray diffraction or by chiroptical measurements in reference to compounds with known configuration. Several examples from the areas of pesticides and pharmaceuticals research illustrate the general approach for studying the behavior of chiral compounds with isolation and characterization of single isomer compounds, investigation of enantioselective degradation processes using racemic as well as enantiopure compounds, and enantioselective residue analysis in wastewater and surface waters. In this article particular emphasis is put on source apportioning of chiral compounds. Examples include apportioning of use of old (racemic) versus new (enantio-enriched) form of a pesticide, agricultural versus nonagricultural use of pesticides, and discharge of pharmaceuticals via urine (after consumption and metabolization in the body) versus disposal of unused drugs. In these cases, the stereoisomer composition of residues serves as a "built-in" marker for the source of the compound or the processes that affected the compound between its source and its point of occurrence.

The bactericide triclosan and methyl triclosan, an environmental transformation product thereof, have been previously detected in lakes and a river in Switzerland. Both compounds are emitted via wastewater treatment plants (WWTPs), with methyl triclosan probably being formed by biological methylation. Passive sampling with semi-permeable membrane devices (SPMDs) showed the presence of methyl triclosan in some lakes, suggesting some potential for bioaccumulation of the compound. In this study, we report the presence of methyl triclosan in fish (white fish, Coregonus sp.; roach, Rutilus rutilus) from various lakes in Switzerland receiving inputs from WWTPs. Identification of the compound was based on mass spectral (MS) evidence including MS/MS data. The concentrations of methyl triclosan in the fish were up to 35 ng g(-1) on a wet weight basis and up to 365 ng g(-1) on a lipid basis with concentrations in a relatively narrow range for fish from the same lake (Thunersee, 4-6 ng g(-1); Zürichsee, 32-62 ng g(-1); Pfäffikersee, 43-56 ng g(-1); Greifensee, 165-365 ng g(-1), lipid basis). No methyl triclosan (<1 ng g(-1), lipid basis) was detected in fish (lake trout, Salmo trutta) from a remote lake in Sweden (Häbberstjärnen) and in fish (roach) from a small lake in Switzerland with no input from WWTPs (Hüttnersee, <2-<5 ng g(-1), lipid basis). The concentrations of methyl triclosan in fish correlated (r2 = 0.85) with the ratio of population in the watershed to water throughflow of the lakes (P/Q ratio), which is considered to be a measure for the domestic burden from WWTPs to a lake. Passive sampling with SPMDs confirmed the presence of methyltriclosan in lakes and a river (Zürichsee and Greifensee; Limmat) but not in a remote mountain lake (Jörisee) and in Hüttnersee. The bioconcentration factor (BCF) of methyl triclosan estimated from the fish data and SPMD-derived water concentrations was in the order of 1-2.6 x 10(5) (lipid basis) and thus in the range of other persistent organic pollutants. SPMDs were found to be reliable for monitoring low concentrations of methyl triclosan in surface water. Methyl triclosan appears to be a suitable marker for WWTP-derived lipophilic contaminants in the aquatic environment and fish.

The synthetic polycyclic musks HHCB and AHTN are potential chemical markers for domestic wastewater contamination of surface waters. Understanding their environmental behavior is important to evaluate their suitability as markers. This study focuses on the quantification of the processes that lead to an elimination in lakes. Rate constants for all relevant processes were estimated based on laboratory studies and models previously described. In lake Zurich, during winter time, both compounds are eliminated primarily by outflowing water and due to losses to the atmosphere. In summer, direct photolysis represents the predominant elimination process for AHTN in the epilimnion of lake Zurich (quantum yield, 0.12), whereas for HHCB, photochemical degradation is still negligible. HHCB and AHTN were then measured in effluents of Swiss wastewater treatment plants (WWTPs), in remote and anthropogenically influenced Swiss surface waters, and in Mediterranean seawater using an analytical procedure based on SPE and GC-MS-SIM with D-6-HHCB as internal standard (LODs for natural waters, 2 and 1 ng/L, respectively). In winter, concentrations of HHCB and AHTN in lakes (<2-47 and <1-18 ng/L, respectively) correlated with the anthropogenic burden by domestic wastewater (ratio population per water throughflow), demonstrating the suitability of these compounds as quantitative, source-specific markers. In summer, however, no such correlations were observed. Vertical concentration profiles in lake Zurich indicated significant losses in the epilimnion during summer, mainly for AHTN, and could be rationalized with a lake modeling program (MASASlight), considering measured, average loads from WWTP effluents (0.80 +/- 0.22 and 0.32 +/- 0.11 mg person(-1) d(-1) for HHCB and AHTN, respectively) and the estimated rate constants for elimination processes.

Research activities at the plant protection chemistry group of the Federal Research Station in Wadenswil, Switzerland, are primarily focused on the environmental behavior of pesticides and, in some cases, other organic micropollutants. Many old and modern pesticides are chiral and there is growing interest from registration authorities and companies in the different biological activity and environmental behavior and impact of individual stereoisomers. The environmental behavior of chiral pesticides is thus one of our main areas of research. We use monitoring data (e.g. surface waters, wastewater) to establish regional mass balances of a chemical (e.g. in the catchment area of a lake). Mass balances often indicate possible sources and presence of elimination processes such as (bio)degradation, sorption/sedimentation, and volatilization. Elimination processes are further investigated in model systems in the laboratory, including batch incubations in soil and water under different regimes (light/dark, sterile/non-sterile), to distinguish between biotic and abiotic (photolysis, hydrolysis) processes. Environmental models are then used to rationalize the chemodynamics of micropollutants in natural systems, integrating data from monitoring and model systems. In some cases, it is possible to use the data for source apportioning of pollutants in the environment, and for monitoring (or prediction) of the effectiveness of pollution prevention measures. In the following report, three examples will be presented which illustrate the general approach outlined above to study the environmental occurrence and behavior of organic micropollutants. These examples include the chiral herbicide mecoprop and the chiral pharmaceutical drug ibuprofen, as well as the ubiquitous natural compound caffeine.

Chiral pesticides are often degraded enantio-/stereoselectively in soils. Degradation is typically studied with one or a small number of soils so that it is not possible to extrapolate the findings on chiral preference to other soils. For this study, the fungicide metalaxyl was chosen as a "chiral probe" to investigate its enantioselective degradation in 20 different soils, selected primarily to cover a wide range of soil properties (e.g., acidic/alkaline, aerobic/ anaerobic) rather than to consider soils of agricultural importance. Racemic metalaxyl was incubated in these soils under laboratory conditions, and the degradation of the enantiomers as well as the enantioselective formation/ degradation of the primary major metabolite, metalaxyl acid, was followed over time, using enantioselective GC-MS after ethylation with diazoethane. In aerobic soils with pH > 5, the fungicidally active R-enantiomer was degraded faster than the S-enantiomer (k(R) > k(S)), leading to residues with a composition [S] > [R]. However, in aerobic soils with pH 4-5, both enantiomers were degraded at similar rates (k(R) approximately k(S)), and in aerobic soils with pH < 4 and in most anaerobic soils, the enantioselectivity was reversed (k(R) < k(S)). These considerable soil-to-soil variations were observed with soils from locations close to each other, in one case even within a single soil profile. Liming and acidification of a "nonenantioselective" soil prior to incubation resulted in enantioselective degradation with k(R)> k(S) and k(R) < k(S), respectively. While the enantioselectivity (expressed as ES = (k(R) - k(S))/(k(R) + k(S))) of metalaxyl degradation in aerobic soils apparently correlated with soil pH, no such correlation was found for metalaxyl acid. Reevaluation of published kinetic data for the herbicides dichlorprop and mecoprop indicated similar correlations between soil pH and ES as for metalaxyl.

The bactericide triclosan and methyl triclosan, an environmental transformation product thereof, were detected in lakes and in a river in Switzerland at concentrations of up to 74 and 2 ng L(-1), respectively. Both compounds were emitted via wastewater treatment plants (WWTPs), with methyl triclosan probably being formed by biological methylation. A regional mass balance for a lake (Greifensee) indicated significant removal of triclosan by processes other than flushing. Laboratory experiments showed that triclosan in the dissociated form was rapidly decomposed in lake water when exposed to sunlight (half-life less than 1 h in August at 47 degrees latitude). Methyl triclosan and nondissociated triclosan, however, were relatively stable toward photodegradation. Modeling these experimental data for the situation of lake Greifensee indicated that photodegradation can account for the elimination of triclosan from the lake and suggested a seasonal dependence of the concentrations (lower in summer, higher in winter), consistent with observed concentrations. Although emissions of methyl triclosan from WWTPs were only approximately 2% relative to those of triclosan, its predicted concentration relative to triclosan in the epilimnion of the lake increases to 30% in summer. Passive sampling with semipermeable membrane devices (SPMDs) indicated the presence of methyl triclosan in lakes with inputs from anthropogenic sources but not in a remote mountain lake. Surprisingly, no parent triclosan was observed in the SPMDs from these lakes. Methyl triclosan appears to be preferentially accumulated in SPMDs under the conditions in these lakes, leading to concentrations comparable to those of persistent chlorinated organic pollutants.

The suitability of caffeine as a chemical marker for surface water pollution by domestic wastewaters was assessed in this study. Caffeine concentrations in influents and effluents of Swiss wastewater treatment plants (WWTPs, 7-73 and 0.03-9.5 microg/L, respectively) indicated an efficient elimination of 81-99.9%. Corresponding loads in untreated wastewater showed small variations when normalized forthe population discharging to the WWTPs (15.8 +/- 3.8 mg person(-1) d(-1)), reflecting a rather constant consumption. WWTP effluent loads were considerably lower (0.06 +/- 0.03 mg person(-1) d(-1)), apart from installations with low sludge age (< or = 5 d, loads up to 4.4 mg person(-1) d(-1)). Despite the efficient removal in most WWTPs, caffeine was ubiquitously found in Swiss lakes and rivers (6-250 ng/ L), except for remote mountain lakes (<2 ng/L; analytical procedure for wastewater and natural waters: SPE, GC-MS-SIM or GC-MS-MS-MRM, internal standard 13C3-labeled caffeine). Caffeine concentrations in lakes correlated with the anthropogenic burden by domestic wastewaters, demonstrating the suitability of caffeine as a marker. A mass balance for Greifensee revealed that approximately 1-4% of the wastewaters had been discharged without treatment, presumably on rainy days when the capacity of WWTPs had been exceeded. For Zürichsee, it could be shown that the monthly inputs of caffeine correlated with precipitation data. The depth- and seasonal-dependent concentrations in this lake were adequately rationalized by a numerical model considering flushing, biodegradation, and indirect photodegradation via HO. radicals as elimination processes and caffeine inputs as fitting variables.

Racemic metalaxyl is currently being replaced in many countries by metalaxyl-M, the fungicide enantiomerically enriched with the biologically active R-enantiomer. This "chiral switch" is expected to reduce the amount of pesticide released into the environment as well as potential side-effects on nontarget organisms. Detailed knowledge of the environmental behavior of such chiral compounds should include information on the chiral stability (interconversion of enantiomers). In the present study, the degradation/ dissipation of metalaxyl and its primary carboxylic acid metabolite (MX-acid) in soil was investigated under laboratory conditions using enantioselective gas chromatography mass spectrometry (GC-MS). Racemic and the enantiopure R- and S-compounds were incubated in separate experiments. The degradation of metalaxyl was shown to be enantioselective with the fungicidally active R-enantiomer being faster degraded than the inactive S-enantiomer, resulting in residues enriched with S-metalaxyl when the racemic compound was incubated. The relatively high enantioselectivity suggests that degradation/dissipation was largely biological. The data indicated a conversion of 40-50% of metalaxyl to MX-acid, and the remaining metalaxyl being degraded via other pathways. The degradation of MX-acid was also enantioselective. Metalaxyl and MX-acid were both configurationally stable in soil, showing no interconversion of R- to S-enantiomers, and vice-versa. Furthermore, the conversion of metalaxyl to MX-acid proceeded with retention of configuration. Degradation followed approximate first-order kinetics but showed significant lag phases.

Racemic metolachlor is currently being replaced by S-metolachlor, the herbicide enantiomerically enriched with the biologically active (S)-isomers. This 'chiral switch' is expected to reduce the amount of pesticide released into the environment as well as potential side-effects on non-target organisms. The switch is also expected to result in lower environmental concentrations and in a changed enantiomer/stereoisomer composition of the residues. To verify this switch, the enantiomer composition of metolachlor residues from a lake (Baldeggersee, Switzerland) receiving inputs from agricultural activities was measured from 1997 through 2001. Enantioselective GC-MS analyses indicated that pre-1998 inputs into the lake were from the racemic compound. In contrast, more recent inputs showed a clear excess of (S)-isomers, and eventually (2000/2001) consisted almost entirely of the new S-metolachlor. The data document the application of enantioselective analysis in environmental studies to apportion the relative contributions of old (racemic) and new (enantioenriched) herbicide on the basis of the enantiomer/stereoisomer composition, The data also show a rapid environmental response to the changed composition of a herbicide. In terms of absolute concentrations no direct evidence could be obtained for the replacement because of year-to-year variations in the inputs likely as a result of intensive rainfall during the application periods.