Including mixtures in the determination of water quality criteria for herbicides in surface water

Swiss Federal Institute for Aquatic Science and Technology (Eawag), Duebendorf, Switzerland.
Environmental Science and Technology (Impact Factor: 5.48). 02/2006; 40(2):426-35. DOI: 10.1021/es050239l
Source: PubMed

ABSTRACT Monitoring programs throughout America and Europe have demonstrated the common occurrence of herbicides in surface water. Nevertheless, mixtures are rarely taken into account in water quality regulation. Taking mixtures into account is only feasible if the water quality criteria (WQC) of the single compounds are derived by a common and consistent methodology, which overcomes differences in data quality without settling on the lowest common denominator but making best use of all available data. In this paper, we present a method of defining a risk quotient for mixtures of herbicides with a similar mode of action (RQm). Consistent and comparable WQC are defined for single herbicides as a basis for the calculation of the RQm. Derived from the concentration addition model, the RQm can be expressed as the sum of the ratios of the measured environmental concentration and the WQC for each herbicide. The RQm should be less than one to ensure an acceptable risk to aquatic life. This approach has the advantage of being easy to calculate and communicate, and is proposed as a replacement for the current limit of 0.1 microg/L for herbicides in Switzerland. We illustrate the proposed approach on the example of five commonly applied herbicides (atrazine, simazine, terbuthylazine, isoproturon, and diuron). Their risk profile, i.e., the RQm as a function of time for one exemplary river, clearly shows that the single compounds rarely exceeded their individual WQC. However, the contribution of peaks of different seasonally applied herbicides, whose application periods partially overlap, together with the continuously emitted herbicides from nonagricultural use, results in the exceedance of the RQm threshold value of one upon several occasions.


Available from: Kathrin Fenner, May 09, 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Decisions in environmental management can be challenging, amongst other things, due to two major sources of uncertainty. Predictions of consequences of different management alternatives can be very uncertain. Furthermore, uncertainty exists regarding the subjective preferences of decision makers and stakeholders. For a transparent decision process it is important to disentangle these different elements and the related sources of uncertainty by separating the prediction of consequences from their valuation. Predictions of consequences should be estimated as objectively as possible based on the current state of knowledge; the Preference functions which are used to valuate these consequences must be elicited carefully to reflect the subjective preferences of each stakeholder. We incorporate uncertainty in decision support by applying the multi-attribute value and utility theory. We propagate uncertainty in the prediction of consequences to the valuation (numerically implemented by Monte Carlo simulation) and incorporate the risk attitude of the stakeholders to discriminate between uncertain alternatives. Furthermore, we address uncertainties inherent in the model of the subjective preference structure by sensitivity analysis to evaluate the robustness of model results against a variation in parameters of the preference model. We illustrate this procedure with a case study on the improvement of water quality in a river catchment of the Swiss Plateau. Different management options to reduce point and non-point sources will be evaluated in this study. For deriving predictions of outcomes, expert knowledge as well as mathematical models can be used. The case study is integrated in a framework for multi-criteria water management (MCWM), which allows us to use existing assessment procedures to evaluate the ecological status of aquatic ecosystems.
    International Congress on Environmental Modelling and Software. Managing Resources of a Limited Planet: Pathways and Visions under Uncertainty, Sixth Biennial Meeting, Leipzig, Germany; 07/2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: Although species sensitivity distribution (SSD) is a key concept for quantitative ecological risk assessment, its application is limited owing to a lack of sufficient data for the analysis, especially on the toxicity of herbicides for primary producers. The authors developed a method of herbicide SSD estimation using single-species toxicity data and information on the herbicide mode of action (MoA). The authors' method was based on the two assumptions: the slopes of SSD of the same MoA herbicides are the same and the relative sensitivities of standard algae in the SSD of the same MoA herbicides are the same. The two parameters of log-normal SSD, mean sensitivity and variation in sensitivity, for 92 herbicides were determined to establish the estimation model. Mean sensitivities were linearly correlated with logarithmic 50% effect concentrations (EC50) for standard algae. The average of variations in sensitivity significantly differed among MoAs, and variations in sensitivity were constant independently of EC50 values for standard algae for the same MoA herbicides. These results were all consistent with the assumptions of our SSD estimation method. The outcome of our SSD estimation method was validated by comparing the estimated SSDs using the proposed method with the generated SSDs using toxicity data which is independent of method development. These SSDs were well consistent, and considering MoA information improved the accuracy of estimating SSD markedly. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Environmental Toxicology and Chemistry 03/2015; 34(3). DOI:10.1002/etc.2828 · 2.83 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Globally coral reefs are at threat from land-sourced pollution. In Australia it is well established that the largest reef system in the world, the Great Barrier Reef, has been seriously damaged by land-sourced pollution primarily from agricultural activities. The Great Barrier Reef is Australia's best documented case of contamination of an ecosystem by pesticides. We describe Australia's current regulatory arrangements for managing pesticide risks to the environment at both national and state level and evaluate the regulatory response to pesticide pollution of the Great Barrier Reef (GBR) and its catchments as a case study. It is argued that the relatively advanced state of knowledge about the problem and the Great Barrier Reef's World Heritage status means that it presents the best case scenario for Australia's ability to respond to pesticide risks to the environment. Yet the only regulatory action taken to date – restricted conditions of use for particular chemical products introduced by the Queensland Government – has occurred outside of the dedicated regulatory regime for managing pesticide risks. Other lower profile and less-studied Australian water bodies are likely to be even less protected. The ad hoc, case-by-case and very slow chemical review process administered by Australia's national pesticide regulator has not effectively assessed or addressed chemical risks to the GBR. Some failures of the current system would be addressed by a systematic re-registration program of the kind in place in the European Union and United States. We conclude that to adequately protect the GBR, given its marine protected area and World Heritage status, both the special management provisions for the area already existing plus an effective national pesticide regulatory regime of the standard of the European Union are the minimum requirements.
    Agriculture Ecosystems & Environment 11/2013; 180:54-67. DOI:10.1016/j.agee.2012.07.001 · 3.20 Impact Factor