Department Environmental Chemistry

During rain events, biocides and plant protection products are transported from agricultural fields but also from urban sources to surface waters. Originally designed to be biologically active, these compounds may harm organisms in aquatic ecosystems. Although several models allow either urban or agricultural storm events to be predicted, only few combine these two sources, and none of them include biocide losses from building envelopes. This study therefore aims to develop a model designed to predict water and substance flows from urban and agricultural sources to surface waters. We developed a model based on physical principles for water percolation and substance flow including micro- (also called matrix-) and macropore-flows for the agricultural areas together with a model representing sources, sewer systems and a wastewater treatment plant for urban areas. In a second step, the combined model was applied to a catchment where an extensive field study had been conducted. The modelled and measured discharge and compound results corresponded reasonably well in terms of quantity and dynamics. The total cumulative discharge was only slightly lower than the total measured discharge (factor 0.94). The total modelled losses of the agriculturally used herbicide atrazine were slightly lower (∼25%) than the measured losses when the soil pore water distribution coefficient (describing the partition between soil particles and pore water) (K_d) was kept constant and slightly higher if it was increased with time. The modelled urban losses of diuron from facades were within a factor of three with respect to the measured values. The results highlighted the change in importance of the flow components during a rain event from urban sources during the most intensive rain period towards agricultural ones over a prolonged time period. Applications to two other catchments, one neighbouring and one on another continent showed that the model can be applied using site specific data for land use, pesticide application, weather and literature data for soil related parameters such as saturated water content, hydraulic conductivity or lateral distances of the drainage pipes without any further calibration of parameters. This is a promising basis for using the model in a wide range of catchments.

Biocides leach from facades during rain events and subsequently enter the aquatic environment with storm water. Little is known about the losses of an entire settlement, since most studies referred to wash-off experiments conducted under laboratory conditions. Their results show a fast decrease of concentrations in the beginning, which subsequently slows down. The aim of this study is to develop a simple model to understand the mechanisms leading to these losses as well as to simulate losses under various rainfall and application conditions.
We developed a four-box model based on the knowledge gained from fits of an exponential function to an existing experimental data set of a wash-off experiment. The model consists of two mobile stocks from which biocides are washed off during a rain event. These mobile stocks are supplied with biocides from storage stocks by diffusion-type processes. The model accurately reproduced the measured data of wash-off during single cycles as well as peak wash-offs over all cycles.
Our model results for diuron losses showed that a large proportion (~70%) of the applied biocides are still in the stocks even after a rain volume corresponding to several years (1100 mm y⁻¹, Swiss Plateau). Applications to realistic outdoor conditions showed that losses can not be neglected for urban environments and that knowledge about the amount of rainfall turned into runoff and the decay constants of the biocides in the facades are crucial. The model increased our understanding of the processes leading to the observed dynamic in laboratory experiments and was used to simulate losses for various rainfall and application conditions.

Todays surface waters are exposed to many anthropogenically used compounds (e.g., nutrients, antibiotics, biocides, etc.). Biocides and pesticides belong to some of the most harmful ones, as they are originally designed and used to kill organisms or to render them harmless. Biocides and pesticides are used in urban as well as in agricultural environments. Agricultural pesticide use has so far received much more attention than that of urban biocides. Only recently several studies on the consumption amounts and on surface water exposures indicated that urban sources may be important.
The aim of this thesis is to assess simultaneously the importance of urban and agricultural biocide and pesticide use on the compound dynamics in surface waters. Most biocides and pesticides are transported during rain events to surface waters. Hence, this work focuses on the dynamic during rain events throughout the year in a catchment (25 km²) with mixed urban and agricultural land use in the Swiss plateau. [...]

Die heutigen Oberflächengewässer sind verschiedenartigsten Belastungen durch anthropogen verwendete Substanzen ausgesetzt (z.B. Nährstoffe, Antibotika, Biozide etc.). Biozide und Pestizide gehören dabei zu den kritischsten Substanzen, da sie zur Schädlingsbekämpfung entwickelt und verwendet werden. Biozide und Pestizide werden sowohl im Siedlungsbereich (urban), als auch in der Landwirtschaft verwendet, wobei bis heute die landwirtschaftlichen Pestizidverluste viel stärker untersucht wurden als diejenigen aus der Siedlung. Erst in den letzten Jahren haben erste Studien gezeigt, dass sich einerseits der Verbrauch in einem ähnlichen Rahmen bewegt, dass aber auch der Biozideintrag in die Gewässer nicht zu vernachlässigen ist.
Das Ziel der hier präsentierten Studie ist es, besser zu verstehen, wie die urbanen und landwirtschaftlichen Quellen die Belastung der Oberflächengewässer mit Bio- und Pestiziden beeinflussen. Die meisten Bio- und Pestizide werden während Regenereignissen in die Gewässer transportiert. Deshalb fokkusierte diese Arbeit auf die Schadstoffdynamik während verschiedener Regenereignisse verteilt über ein ganzes Jahr. Das betrachtete Einzugsgebiet (25 km²) hat eine für das Schweizer Mitteland typische, gemischt landwirtschaftlich-urbane Landnutzung. [...]

Relative contributions of agricultural and urban uses to the glyphosate contamination of surface waters were studied in a small catchment (25 km²) in Switzerland. Monitoring in four sub-catchments with differing land use allowed comparing load and input dynamics from different sources. Agricultural as well as urban use was surveyed in all sub-catchments allowing for a detailed interpretation of the monitoring results. Water samples from the river system and from the urban drainage system (combined sewer overflow, storm sewer and outflow of wastewater treatment plant) were investigated. The concentrations at peak discharge during storm events were elevated throughout the year with maximum concentrations of 4.15 μg L⁻¹. Glyphosate concentrations mostly exceeded those of other commonly used herbicides such as atrazine or mecoprop. Fast runoff from hard surfaces led to a fast increase of the glyphosate concentration shortly after the beginning of rainfall not coinciding with the concentration peak normally observed from agricultural fields. The comparison of the agricultural application and the seasonal concentration and load pattern in the main creek from March to November revealed that the occurrence of glyphosate cannot be explained by agricultural use only. Extrapolations from agricultural loss rates and from concentrations found in the urban drainage system showed that more than half of the load during selected rain events originates from urban areas. The inputs from the effluent of the wastewater treatment plant, the overflow of the combined sewer system and of the separate sewer system summed up to 60% of the total load.

Biocides and pesticides are designed to control the occurrence of unwanted organisms. From their point of application, these substances can be mobilized and transported to surface waters posing a threat to the aquatic environment. Historically, agricultural pesticides have received substantially more attention than biocidal compounds from urban use, despite being used in similar quantities.
This study aims at improving our understanding of the influence of mixed urban and agricultural land use on the overall concentration dynamics of biocides and pesticides during rain events throughout the year. A comprehensive field study was conducted in a catchment within the Swiss plateau (25 km²). Four surface water sampling sites represented varying combinations of urban and agricultural sources. Additionally, the urban drainage system was studied by sampling the only wastewater treatment plant (WWTP) in the catchment, a combined sewer overflow (CSO), and a storm sewer (SS). High temporal resolution sampling was carried out during rain events from March to November 2007.
The results, based on more than 600 samples analyzed for 23 substances, revealed distinct and complex concentration patterns for different compounds and sources. Five types of concentration patterns can be distinguished: a) compounds that showed elevated background concentrations throughout the year (e.g. diazinon >50 ng L⁻¹), indicating a constant household source; b) compounds that showed elevated concentrations driven by rain events throughout the year (e.g. diuron 100–300 ng L⁻¹), indicating a constant urban outdoor source such as facades; c) compounds with seasonal peak concentrations driven by rain events from urban and agricultural areas (e.g. mecoprop 1600 ng L⁻¹ and atrazine 2500 ng L⁻¹ respectively); d) compounds that showed unpredictably sharp peaks (e.g. atrazine 10,000 ng L⁻¹, diazinon 2500 ng L⁻¹), which were most probably due to improper handling or even disposal of products; and finally, e) compounds that were used in high amounts but were not detected in surface waters (e.g. isothiazolinones).
It can be safely concluded that in catchments of mixed land use, the contributions of biocide and pesticide inputs into surface waters from urban areas are at least as important as those from agricultural areas.

Biocides and pesticides are used to control unwanted organisms in urban and agricultural areas. After application, they can be lost to surface waters and impair water quality. Several national consumption studies have shown that urban and agricultural use may be in the same range. It is difficult to judge whether this results in similar loadings of surface waters because there is a lack of sound, comparative studies addressing urban and agricultural losses simultaneously.
The aim of this study is thus to relate the biocide and pesticide loads found in surface waters to their respective urban and agricultural usage (loss rates). To simultaneously assess the loss rates, we conducted a comprehensive field study in a catchment of mixed land use on the Swiss Plateau. The study area was divided into four sub-catchments with different degrees of urban and agricultural land use. In addition, we studied the only wastewater treatment plant, a combined sewer overflow and a storm sewer within the area. Rain events were sampled at high temporal resolution from March to November, 2007. Information on agricultural applications was gained from local farmers. For urban uses, consumption estimations were conducted based on statistical and product information.
Despite substantially lower amounts used, the measured loads of urban biocides were in the same range as the most widely-used agricultural pesticides. The lower usage was compensated by urban loss rates that were up to ten times higher than agricultural ones (0.6 to 15% for urban, 0.4 to 0.9% for agricultural compounds). For most biocides and pesticides, the loads were controlled by rain events. Besides the rain-controlled losses, some urban-used biocides (e.g. diazinon) showed a continuous load independent of rain events and season. This study demonstrates that in catchments with mixed land use, mitigation strategies have to pay sufficient attention to the urban sources.

Biozide und Pestizide werden in der Landwirtschaft und im Siedlungsraum eingesetzt, um Schädlinge zu bekämpfen. Doch welche Wege nehmen diese Stoffe vom Einsatzort bis ins Gewässer? Und ist die Landwirtschaft tatsächlich die Hauptverursacherin der Gewässerbelastung? Fragen, die die Eawag in verschiedenen Projekten erforscht.

This study focused on the input of hydrophilic biocides into the aquatic environment and on the efficiency of their removal in conventional wastewater treatment by a mass flux analysis. A fully automated method consisting of on-line solid phase extraction coupled to LC-ESI-MS/MS was developed and validated for the simultaneous trace determination of different biocidal compounds (1,2-benzisothiazoline-3-one (BIT), 3-Iodo-2-propynylbutyl-carbamate (IPBC), irgarol 1051 and 2-N-octyl-4-isothiazolinone (octhilinone, OIT), carbendazim, diazinon, diuron, isoproturon, mecoprop, terbutryn and terbutylazine) and pharmaceuticals (diclofenac and sulfamethoxazole) in wastewater and surface water. In the tertiary effluent, the highest average concentrations were determined for mecoprop (1010 ng/L) which was at comparable levels as the pharmaceuticals diclofenac (690 ng/L) and sulfamethoxazole (140 ng/L) but 1–2 orders of magnitude higher than the other biocidal compounds. Average eliminations for all compounds were usually below 50%. During rain events, increased residual amounts of biocidal contaminants are discharged to receiving surface waters.

Temporally resolved environmental risk assessment of fluctuating concentrations of micropollutants is presented. We separated the prediction of toxicity over time from the extrapolation from one to many species and from acute to sublethal effects. A toxicokinetic–toxicodynamic (TKTD) model predicted toxicity caused by fluctuating concentrations of diazinon, measured by time-resolved sampling over 108 days from three locations in a stream network, representing urban, agricultural and mixed land use. We calculated extrapolation factors to quantify variation in toxicity among species and effect types based on available toxicity data, while correcting for different test durations with the TKTD model. Sampling from the distribution of extrapolation factors and prediction of time-resolved toxicity with the TKTD model facilitated subsequent calculation of the risk of undesired toxic events. Approximately one-fifth of aquatic organisms were at risk and fluctuating concentrations were more toxic than their averages. Contribution of urban and agricultural sources of diazinon to the overall risk varied. Thus using fixed concentrations as water quality criteria appears overly simplistic because it ignores the temporal dimension of toxicity. However, the improved prediction of toxicity for fluctuating concentrations may be small compared to uncertainty due to limited diversity of toxicity data to base the extrapolation factors on.