Christian Stamm

Significance of urban and agricultural land use for biocide and pesticide dynamics in surface waters

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 km(2)). 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.

Reducing the Discharge of Micropollutants in the Aquatic Environment: The Benefits of Upgrading Wastewater Treatment Plants

Micropollutants (MPs) as individual compounds or in complex mixtures are relevant for water quality and may trigger unwanted ecological effects. MPs originate from different point and diffuse sources and enter water bodies via different flow paths. Effluents from conventional wastewater treatment plants (WWTPs), in which various MPs are not or not completely removed, is one major source. To improve the water quality and avoid potential negative ecological effects by micropollutants, various measures to reduce the discharge should be taken. In this feature we discuss one of these measures; the benefits of upgrading WWTPs toward reduced MP loads and toxicities from wastewater effluents, using the recently decided Swiss strategy as an example. Based on (i) full-scale case studies using ozonation or powder activated carbon treatment, showing substantial reduction of MP discharges and concomitant reduced toxicities, (ii) social and political acceptance, (iii) technical feasibility and sufficient cost-effectiveness, the Swiss authorities recently decided to implement additional wastewater treatment steps as mitigation strategy to improve water quality. Since MPs are of growing global concern, the concepts and considerations behind the Swiss strategy are explained in this feature, which could be of use for other countries as well. It should be realized that upgrading WWTPs is not the only solution to reduce the discharge of MPs entering the environment, but is part of a broader, multipronged mitigation strategy.

How a Complete Pesticide Screening Changes the Assessment of Surface Water Quality

A comprehensive assessment of pesticides in surface waters is challenging due to the large number of potential contaminants. Most scientific studies and routine monitoring programs include only 15-40 pesticides, which leads to error-prone interpretations. In the present study, an extensive analytical screening was carried out using liquid chromatography-high-resolution mass spectrometry, covering 86% of all polar organic pesticides sold in Switzerland and applied to agricultural or urban land (in total 249 compounds), plus 134 transformation products; each of which could be quantified in the low ng/L range. Five medium-sized rivers, containing large areas of diverse crops and urban settlements within the respective catchments, were sampled between March and July 2012. More than 100 parent compounds and 40 transformation products were detected in total, between 30 and 50 parent compounds in each two-week composite sample in concentrations up to 1500 ng/L. The sum of pesticide concentrations was above 1000 ng/L in 78% of samples. The chronic environmental quality standard was exceeded for 19 single substances; using a mixture toxicity approach, exceedances occurred over the whole measurement period in all rivers. With scenario calculations including only 30-40 frequently measured pesticides, the number of detected substances and the mixture toxicity would be underestimated on average by a factor of 2. Thus, selecting a subset of substances to assess the surface water quality may be sufficient, but a comprehensive screening yields substantially more confidence.

Multiple tracing of fast solute transport in a drained grassland soil

Fast transport of fertilizers and other agrochemicals into subsurface drainage systems has been recognized as a serious threat to surface waters. We report on a tracer experiment carried out on a 7.3×20 m2 plot on a loamy grassland soil to determine the flow paths to a tile drain at 1 m depth. The experiment consisted of a series of consecutive tracer applications including seven solutes and liquid manure that were applied either on the entire plot or on limited bands. Based on the discharge behavior under natural conditions, we estimated the effective hydraulic conductivity of the subsoil to be in the order of 8–29 cm day−1. Under experimental conditions, the soil transmitted 120 mm day−1 into the subsurface drain and two vertical profiles without producing surface runoff. Only part of the soil water, corresponding to 6–27 mm of the soil depth, contributed to the fast hydrological response. The transport of the tracers was very fast. Within 7–16 h after application of the conservative Br−, Cl− and HDO and the slightly sorbing substances brilliant blue (BB) and amino-G-acid (AG), these tracers reached relative concentrations in the outflow between 19% and 35% of the input concentrations. From the mass balance for water and solutes, it follows that the tracers were quickly transported over lateral distances of several meters. The manure constituents dissolved reactive P (DRP), NH4+ and Cl−, applied as liquid manure on the surface on a 1 m wide band above the tile drain, reached the drain within 5 min after application. After the early peak of DRP and NH4+, their concentration in the drain decreased quickly to background levels, whereas Cl− exhibited a second peak. Despite the fast transport and the small soil volume conducting water and solutes, the interaction between irrigation water and soil matrix was intimate enough to retain the two sorbing tracers. From the stained flow paths, the hydrologic behavior of the field under natural conditions and the hydrometric data during the experiment, it follows that the fast lateral tracer transport occurred mainly close to soil surface and not through the subsoil. Only in the immediate vicinity of the tile drain and of two lateral pits at the edge of the experimental plot water was redirected downwards and discharged from the tile drain and the bottom parts of the profiles, respectively. Hence, effluent from tile drains may not be representative for water reaching the subsoil or shallow ground water in undisturbed soils.

Future agriculture with minimized phosphorus losses to waters: Research needs and direction

Abstract The series of papers in this issue of AMBIO represent technical presentations made at the 7th International Phosphorus Workshop (IPW7), held in September, 2013 in Uppsala, Sweden. At that meeting, the 150 delegates were involved in round table discussions on major, predetermined themes facing the management of agricultural phosphorus (P) for optimum production goals with minimal water quality impairment. The six themes were (1) P management in a changing world; (2) transport pathways of P from soil to water; (3) monitoring, modeling, and communication; (4) importance of manure and agricultural production systems for P management; (5) identification of appropriate mitigation measures for reduction of P loss; and (6) implementation of mitigation strategies to reduce P loss. This paper details the major challenges and research needs that were identified for each theme and identifies a future roadmap for catchment management that cost-effectively minimizes P loss from agricultural activities.

Hot-Electron-Driven Enhancement of Spin-Lattice Coupling in Gd and Tb 4 f Ferromagnets Observed by Femtosecond X-Ray Magnetic Circular Dichroism

Femtosecond x-ray magnetic circular dichroism was used to study the time-dependent magnetic moment of 4f electrons in the ferromagnets Gd and Tb, which are known for their different spin-lattice coupling. We observe a two-step demagnetization with an ultrafast demagnetization time of 750 fs identical for both systems and slower times which differ sizeably with 40 ps for Gd and 8 ps for Tb. We conclude that spin-lattice coupling in the electronically excited state is enhanced up to 50 times compared to equilibrium.

Relevance of urban glyphosate use for surface water quality.

Relative contributions of agricultural and urban uses to the glyphosate contamination of surface waters were studied in a small catchment (25 km(2)) 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.

Loss rates of urban biocides can exceed those of agricultural pesticides.

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.

Targeting aquatic microcontaminants for monitoring: exposure categorization and application to the Swiss situation

Background, aim, and scopeAquatic microcontaminants (MCs) comprise diverse chemical classes, such as pesticides, biocides, pharmaceuticals, consumer products, and industrial chemicals. For water pollution control and the evaluation of water protection measures, it is crucial to screen for MCs. However, the selection and prioritization of which MCs to screen for is rather difficult and complex. Existing methods usually are strongly limited because of a lack of screening regulations or unavailability of required data.Method and modelsHere, we present a simple exposure-based methodology that provides a systematic overview of a broad range of MCs according to their potential to occur in the water phase of surface waters. The method requires input of publicly available data only. Missing data are estimated with quantitative structure–property relationships. The presented substance categorization methodology is based on the chemicals’ distribution behavior between different environmental media, degradation data, and input dynamics.ResultsSeven different exposure categories are distinguished based on different compound properties and input dynamics. Ranking the defined exposure categories based on a chemical’s potential to occur in the water phase of surface waters, exposure categories I and II contain chemicals with a very high potential, categories III and IV contain chemicals with a high potential, and categories V and VI contain chemicals with a moderate to low potential. Chemicals in category VII are not evaluated because of a lack of data. We illustrate and evaluate the methodology on the example of MCs in Swiss surface waters. Furthermore, a categorized list containing potentially water-relevant chemicals is provided.DiscussionChemicals of categories I and III continuously enter surface waters and are thus likely to show relatively steady concentrations. Therefore, they are best suited for water monitoring programs requiring a relatively low sampling effort. Chemicals in categories II and IV have complex input dynamics. They are consequently more difficult to monitor. However, they should be considered if an overall picture is needed that includes contaminants from diffuse sources.ConclusionsThe presented methodology supports compound selection for (a) water quality guidance, (b) monitoring programs, and (c) further research on the chemical’s ecotoxicology. The results from the developed categorization procedure are supported by data on consumption and observed concentrations in Swiss surface waters. The presented methodology is a tool to preselect potential hazardous substances based on exposure-based criteria for policy guidance and monitoring programs and a first important step for a detailed risk assessment for potential microcontaminants.

Integrating chemical analysis and bioanalysis to evaluate the contribution of wastewater effluent on the micropollutant burden in small streams

Surface waters can contain a range of micropollutants from point sources, such as wastewater effluent, and diffuse sources, such as agriculture. Characterizing the source of micropollutants is important for reducing their burden and thus mitigating adverse effects on aquatic ecosystems. In this study, chemical analysis and bioanalysis were applied to assess the micropollutant burden during low flow conditions upstream and downstream of three wastewater treatment plants (WWTPs) discharging into small streams in the Swiss Plateau. The upstream sites had no input of wastewater effluent, allowing a direct comparison of the observed effects with and without the contribution of wastewater. Four hundred and five chemicals were analyzed, while the applied bioassays included activation of the aryl hydrocarbon receptor, activation of the androgen receptor, activation of the estrogen receptor, photosystem II inhibition, acetylcholinesterase inhibition and adaptive stress responses for oxidative stress, genotoxicity and inflammation, as well as assays indicative of estrogenic activity and developmental toxicity in zebrafish embryos. Chemical analysis and bioanalysis showed higher chemical concentrations and effects for the effluent samples, with the lowest chemical concentrations and effects in most assays for the upstream sites. Mixture toxicity modeling was applied to assess the contribution of detected chemicals to the observed effect. For most bioassays, very little of the observed effects could be explained by the detected chemicals, with the exception of photosystem II inhibition, where herbicides explained the majority of the effect. This emphasizes the importance of combining bioanalysis with chemical analysis to provide a more complete picture of the micropollutant burden. While the wastewater effluents had a significant contribution to micropollutant burden downstream, both chemical analysis and bioanalysis showed a relevant contribution of diffuse sources from upstream during low flow conditions, suggesting that upgrading WWTPs will not completely reduce the micropollutant burden, but further source control measures will be required.