pesticides in esteros del ibera (ar): evaluation of impacts … · · 2011-10-16proposal of...

Ecological Modelling 186 (2005) 85–97

Pesticides in Esteros del Ibera (AR): evaluation of impacts andproposal of guidelines for water quality protection

Carla Silva, Cristina Boia, Joana Valente, Carlos Borrego∗

Department of Environment and Planning, University of Aveiro, PT-3810-193-Aveiro, Portugal

Available online 3 March 2005

Abstract

This work is within the framework of a project where the overall objective is to create the methodology for a sustainablemanagement of an important wetland in Argentina, “Esteros del Ibera”. Rice culture has been identified as the main anthropogenicactivity, being necessary to evaluate the impacts of pesticides used in rice culture on the aquatic ecosystem. The purpose of thispaper is to evaluate the impacts of pesticides used in rice culture through the use of a Mackay’s model, to identify the potentiallymore contaminated environmental compartments, and identify their toxicological and physicochemical properties. Based onthe results of the model, water samples were collected and two insecticides (endosulfan and carbofuran) were analysed usingthe solid-phase microextraction (SPME) extraction technique with detection by gas chromatography with mass spectrometry(GC–MS). To create a decision tool based on monitorization results, pesticide guidelines for water quality (drinking and foraquatic life protection) were calculated and compared with the available international regulations for pesticides; conservativeguidelines are recommended. The results of pesticides analysis were compared with these guidelines; some results exceededt se to thed es on mostw , speciallyi©

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aterstrials ofde-foodhell-malsiallyrna-

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he international guidelines (mainly the values for protection of aquatic life) in particular those from samples taken cloischarge points and due to the presence of the more toxic insecticide endosulfan; however, the impact of pesticidaters of the lagoon Ibera seems not yet to be very significant, but monitoring of impacts and careful use of pesticides

nsecticides, should be observed in the future.2005 Elsevier B.V. All rights reserved.

eywords:Pesticides; Modelling; Analysis; Water quality; Guidelines

. Introduction

Wetlands are areas where water covers the soil, ors present inside or near the surface of the soil duringll year or for significant periods of the year (US-

∗ Corresponding author. Tel.: +351 234 400800;ax: +351 234 382876.E-mail address:[email protected] (C. Borrego).

EPA, 2000a). The almost continuous presence of wcreates conditions to support aquatic and terreliving species. The combination of water, high levelnutrients, and primary productivity is ideal for thevelopment of organisms that form the base of theweb and feed many species of fish, amphibians, sfish, and insects. Many species of birds and mamrely on wetlands for food, water and shelter, especduring migration and breeding. Indeed, an inte

304-3800/$ – see front matter © 2005 Elsevier B.V. All rights reserved.doi:10.1016/j.ecolmodel.2005.01.018

86 C. Silva et al. / Ecological Modelling 186 (2005) 85–97

tional agreement to protect wetlands of internationalimportance (the Ramsar Convention on Wetlands) wasdeveloped because some species of migratory birds arecompletely dependent on certain wetlands and wouldbecome extinct if those wetlands were destroyed(Barbier et al., 1997). Besides providing biologicalhabitat, wetlands play a vital role in water qualitymanagement because they have important filtering ca-pabilities to retain excess nutrients and some pollutants.

Losing or degrading wetlands can lead to seriousconsequences, such as increased flooding, extinctionof species, and decline in water quality.

Some wetlands are situated near agriculture lands.These activities take advantage of wetland rich re-sources, like irrigation water but, on the other hand,they can be affected by the over use of chemical prod-ucts, such as fertilizers and/or pesticides, necessary forthe success of intensive agriculture.

The need to avoid the risk to the environmental dueto the use of such chemicals has been the base of theregulations to control their use, such as of pesticidesin developed countries. There has been an increasedawareness and concern from the public and regulatoryauthorities regarding the potential of pesticides to con-taminate air, soil and water sources. This pressure hasresulted in the evolution of different assessment meth-ods in order to quantify the fate and effects of suchproducts in environment and human health (Eadsforthand Woodbridge, 1995).

In this study the assessment of the impact of agricul-t atice ling,

field and laboratory work. The results obtained withthis type of approach are normally used to introducechanges in the traditional agricultural practices in orderto achieve a better quality of the aquatic environment,required in a sustainable agriculture.

2. Pesticides and rice production in the Esterosdel Ibera region

The studied site is a large wetland area (13,000 km2)in north eastern Argentina (Fig. 1), the “Esteros delIbera”, a complex ecosystem which includes manylagoons (Ibera, Galarza, Luna, etc.) inhabited by wildanimals such as alligators, monkeys, swamp deers,etc., Rice, usually considered as one of the main cropsin terms of pesticide consumption, occupies the morerelevant position in agriculture activity of “Esteros”. Inrecent years the need to increase crop yields has led tothe adoption of more intensive production systems witha consequent raise in pesticides use. Therefore, riceproduction can affect the quality of aquatic communi-ties of Ibera lagoons, since water containing pesticidesfrom these crops are discharged, through drainagechannels or directly, into water bodies. The fate andimpact of these products into the surrounding ecosys-tems are, in most cases, unknown. In this case, thecontamination can affect not only the water ecosystembut also the drinking water, since the local populationuses water from the lagoons in the public supplys cider

dy site

ural rice practices, particularly pesticides, on aqunvironment has been made integrating model

Fig. 1. Stu

ystem, after a treatment not suitable for pestiemoval.

localisation.

C. Silva et al. / Ecological Modelling 186 (2005) 85–97 87

3. Methodology

3.1. General

The proposed objectives of this work were per-formed through five main phases.

The use of pesticides in the intensive rice productionin the Esteros region was exhaustively studied, throughenquiries made directly among producers (speciallythose with larger productions) and visits to the field;information such as growing season, irrigation system,soil preparation, types and quantity of agrochemicalsused was collected.

The physicochemical, toxicological and persistencecharacteristics of the pesticides used were gatheredfrom scientific literature and international organiza-tions for environmental and health protection. Usingthis information as input data, Mackay multimediamodel (level I) was then used to evaluate the main envi-ronmental compartments affected by each of the pesti-cides applied. Based on the results of the model, a sam-pling and analytical plan for the determination of themore hazardous pesticides in the water was elaborated.

A selection of methods for pesticide analysis, basedon a literature review and on the experience of anotherresearch team was carefully made.

Water samples were then collected and some of thepesticides (endosulfan and carbofuran), with predictedmore significant impacts in water, were analysed.Three water sampling campaigns have been performed,i Thea e mi-c gasc ).

forp ewo , asw riska vativec e ast ablev terosd

3

en-v the

fugacity approach proposed byMackay et al. (1997). Inthis model, a standard “unit of world” is proposed, rep-resenting a surface of 100,000 km2 with six differentenvironmental compartments: air, water, soil, bottom-sediment, suspended sediment and fish. This model,based on the equilibrium criteria (EQC) approachdescribed byMackay et al. (1996a)deduces the fate ofa specified chemical in three levels of complexity I, IIand III, which have increasing data requirements, intro-duce greater complexity, and reveal progressively moreabout the nature of the chemical (Mackay et al., 1996a).A level I simulation includes the equilibrium distribu-tion of a fixed quantity of conserved (i.e. non-reacting)chemical, in a closed environment at equilibrium, withno degrading reactions, no advective processes, and nointermediate transport processes. The compartment re-ceiving the emission is unimportant because the chem-ical is assumed to become instantaneously distributedbetween all the environmental compartments, to anequilibrium condition (Mackay et al., 1996a, 1997). Alevel I calculation is very useful to describe how a givenamount of chemical is distributed between six mediaand gives an indication of relative concentrations ineach medium, requiring few input data, which includesphysicochemical characteristics of the chemical and itspartition coefficients among the various environmen-tal compartments. The physicochemical propertiesrequired for application of the multimedia equilibriumcriterion model are: molecular mass, solubility inwater, vapour pressure, octanol–water partition coeffi-ce p-e als,w theirp .( ami

3

s ind ies)i Thec pec-t thea delyae ow

n June 2000, November 2000 and March 2001.nalysis has been performed using the solid-phasroextraction (SPME) technique with detection byhromatography with mass spectrometry (GC–MS

The final step was the compilation of guidelinesrotection of aquatic life and drinking water. A revif guidelines from different countries was madeell as estimates based on toxicological data andssessment calculation methods. Then, a conseromparison between both sets of data was madhe base to the proposal of maximum recommendalues for several of the pesticides used in the Esel Ibera region.

.2. Mackay’s model

The mathematical model applied to estimate theironmental distribution of pesticides, is based on

ient and organic-carbon partition coefficient (Mackayt al., 1997). The relative significance of these prorties varies according to the nature of chemichich can be classified into five types based onartitioning characteristics as shown inMackay et al1996b). A detailed description of the specific progrs given inMackay et al. (1996a).

.3. Pesticide analysis

The identification and determination of pesticideifferent water matrices (water with specific propert

s an analytical problem of increasing importance.ombination of gas chromatography with mass srometry (GC–MS) is the most specific method fornalysis of complex matrices and it has been wipplied for the determination of pesticides (Crespot al., 1994). On the other hand, GC–MS shows l


sensitivity even with selected-ion monitoring (SIM)and the use of a pre-concentration system is alwaysrequired. Various pre-concentration methods based ondifferent physicochemical principles are commonlyused such as liquid–liquid extraction (LLE) or solid-phase extraction (SPE). LLE is a very useful techniquethat is used in several accepted methods, but it hassome disadvantages: it is very time consuming andrequires large amounts of solvents, which are oftentoxic and flammable. SPE is less time consuming thanLLE, however it still requires toxic organic solvents forthe elution step. Recently, a new extraction technique,solid-phase microextraction (SPME) has been intro-duced with some advantages over the other techniques:it is a solvent-free sample preparation technique, so itminimises the cost and hazardousness of high-puritysolvents, it is easy to use, fast, and requires very smallsample volumes (Aguilar et al., 1998).

The SPME process has two steps: the partitioning ofthe analytes between the sample matrix and a stationaryphase which is coated on a fibre (there are differentfibres for each group of compounds); the desorption ofthe trapped analytes into the analytical instrument.

In order to determine pesticide concentrations inthe water samples, the SPME extraction technique wasused in this work with detection by GC–MS. The fibresused were polydimethylsiloxane (PDMS), polyacrylate(PA), carboxen/PDMS (CAR/PDMS) and carbowax di-vinil benzene (CW/DVB).

The definition of the sampling plan was based on them en-t 000( ber2 st ofr edi tiont bud-g en-d cidesa sedo pes-t osea

3

thed ter.

An RfD is defined as an estimate of the intake of a sub-stance over a lifetime that is considered to be withoutappreciable health risk (WHO, 1994). A review of theexistent data about the chemical whose RfD is to be de-termined should be undertaken to evaluate the criticaleffects. These effects are of two types: those which havea threshold value and those which represent some riskat any level—non-threshold. In this work, all the chem-icals studied were considered to have a threshold value.In this case, the RfD is determined dividing a NOAEL(non-observed adverse effect level) obtained from oneor various toxicological studies by uncertainty factors(UF).

A NOAEL from a long-term toxicity study shouldbe chosen. The review of the data may reveal two ormore significant NOAELs with different orders of mag-nitude. Under these circumstances, it should be chosenthe NOAEL that results in the lower RfD. The RfDdepends not only on the NOAEL but also on the UF.It may happen that a higher NOAEL results in a lowerRfD if the suitable UF is bigger (WHO, 1994). The cho-sen study may be a study with humans or with otheranimals. When the study has been made with animalsit is necessary to take in account the interindividualand interspecific variability of the results. If the studyhas been made with humans only the interindividualvariability has to be considered (WHO, 1994). A 10-fold factor is usually applied to allow for differencesin sensitivity between the population mean and highsensitive subjects. A 10-fold factor is also commonlyu

thed asm

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w odywaD(

re-s aren saysc -t nedp the

ain steps of rice production in the region already idified. Three sampling periods were defined: June 2for the calibration of analytical methods), Novem000 (culture of rice seeds) and March 2001 (harveice). The collection of water samples was performn two rice fields and in Laguna Ibera. The extracechnique and the pesticide analysis were, due toet limitations, optimised only for the insecticidesosulfan and carbofuran. The choice of these pestimong all those used in the region was mainly ban the previous studies that allowed to predict the

icides with more significant impacts in water, so thnalysis should have a higher priority.

.4. Calculation of guidelines

Establishing a reference dose (RfD) is central toetermination of guidance values for drinking wa

sed to extrapolate different species sensitivities.After the determination of the reference dose

erivation of the guideline value for drinking water wade applying the following calculation:

V = RfD × BW × %

DWC

here GV is the guideline value, BW the mean beight—65 kg (US-EPA, 1997), % the fraction of RfDllocated to drinking water—10% (WHO, 1994) andWC the daily drinking water consumption—2 L d−1

US-EPA, 1997).To derive guidelines for aquatic life protection,

ults from short-term ecotoxicological bioassaysormally used, but results of more sensitive bioasan also be used. The lowest LC50 (lethal concentraion for half the population exposed in a determieriod of time) from an acute exposure study or


Table 1Application factors to calculate concentrations without effects on aquatic biota (Zandt and Leeuwen, 1992)

CEE/CSTE EPA-USA OCDE IPS

Factor 1000 Various acute bioassayslowest valueof—L(E)C50,few data

Lowest acute L(E)C50 orQSAR estimate for acutetoxicity

=EPA/USA (one or two species) =EPA/USAa

Factor 100 Lowest value of acutebioassays—L(E)C50,many dataor lowest valueof chronicle L(E)C50 orNOEC of few data

Lowest acute L(E)C50 orQSAR estimate for acutetoxicity—at least bioassayswith organisms from threelevels of organization—algae,crustacean and fishes

=EPA/USA =EPA/USAa

Factor 10 Lowest chronicle NOECs Lowest NOEC or QSARestimate for chronicletoxicity—at least algae,crustacean and fishes

=EPA/USA =EPA/USAa

a Amendment in ISPRA Meeting (December 1993): 100× if NOECs for 1 species; 5000× if L(E)C50 for <2 species; 50× if NOECs for2 species; 1000× if L(E)C50 for >3 species; 10× if NOECs for 3 species where L(E)C50 is the lethal or effect concentration on 50% of theorganisms, QSAR the quantitative structure–activity relationship and NOEC the non-observable effect concentration.

results of a more sensitive bioassays, multiplied by anacute/chronic ratio or the appropriate application fac-tor, can be used to derive the final guideline concen-tration for protection of aquatic life.Table 1shows theapplication factor to be used, according to the nature ofavailable information and various international organ-isms. In this work LC50 results were used from manyor few tests, depending on the pesticide, factors of 100or 1000 were used:

GVPAL = 0.001× LC50 or GVPAL = 0.01× LC50

4. Results and discussion

Agriculture practices for rice production in the Es-teros del Ibera region start normally by July and endby December. These practices include soil prepara-tion (levelling of the field, fertilisation and applicationof pre-planting insecticides and herbicides), seedtime,flooding of rice field during 48 h (if necessary a secondapplication of insecticides and herbicides is made inthis phase) and permanent irrigation until harvest.

4.1. Mackay’s model results and pesticidescharacterization

Figs. 2 and 3show the distribution of the pesti-cides (herbicides and insecticides) used in the region,among the various environmental compartments, cal-

culated using the first level of the MacKay Model; al-most all the analysed herbicides have preferential dis-tribution for water and half of the studied insecticidesshow preference for solid matrices.

The selection of pesticides for a particular studymust consider not only the results obtained with theMackay model, but also the amount of each pesticideused in crops treatment, the availability of information,and the ecotoxicological and persistence properties ofthe pesticides. The main toxicological, physicochemi-cal and persistence characteristics of these pesticides,relevant to help selecting those who should be studiedmore carefully, are presented inTable 2.

The application rate, also indicated inTable 2, rep-resents the quantity of substance introduced in the ricegrowing system. A fraction of these substances is trans-ported to the Ibera Lagoon and may represent an im-portant source of contamination. Among the evaluatedpesticides only three herbicides (glyphosate, molinateand propanil) and one insecticide (carbofuran), are in-troduced in large amounts.

The persistence is defined according to thesubstance’s half-life (t1/2) in the environmentalcompartments. The half-life is the time required toreduce to one-half the substance’s concentration. Allinsecticides except methamidophos are potentiallypersistent in soil. The herbicides that can remainlonger periods in this environmental compartment areclomazone, dicamba, metsulfuron-methyl, glyphosateand molinate. The potentially more persistent


herbicides in water are the metsulfuron-methyland glyphosate and, for insecticides, carbofuran,endosulfan, methamidophos and monocrotophos.

The octanol–water partition coefficient provides adirect estimate of the hydrophobicity, or of the pesti-cide partitioning tendency from water to organic me-dia such as lipids, waxes and natural organic mattersuch as humic acids (Mackay et al., 1997). It is also anestimate of the capacity of a given chemical to bioac-cumulate in living organisms. The most biocumulativepesticides are the insecticides deltamethrin, endosulfan

and lambda-cyhalothrin and the herbicide fenoxaprop-ethyl.

The toxicity class is defined by the U.S. Environ-mental Protection Agency and the World Health Or-ganisation. This classification varies between I and IV(I for the most toxic substances and IV for the lesstoxic substances). All the insecticides are consideredvery toxic. In what concerns herbicides, only cloma-zone and molinate present critical values.

Considering all these criteria, as well as the avail-able budget and time limitations, the insecticides car-

Fig. 2. Distribution of the insecticides used in the reg
ion among the various environmental compartments.


Fig. 3. Distribution of the herbicides used in the region among the various environmental compartments.

bofuran and endosulfan were chosen to be analysed inwater samples. In fact, these pesticides are simultane-ously very toxic and very persistent in water and soilcompartments.

4.2. Guidelines results

The definition of the maximum allowable concen-tration of a chemical in water is a process that involvesvarious stages with different perspectives, since this de-cision must be based in socio-economic, political andtechnical reasons. In this paper, only the technical per-spective is addressed.

Table 3shows the results of guidelines calculationsfor pesticides in drinking water (GVDW) and for aquaticlife protection (GVPAL), based on published effects andsecurity factors. There is a certain relationship betweenvalues obtained for drinking water and for protectionof aquatic life, as can be seen inFig. 4; in general, con-centrations able to protect aquatic life, estimated usingthe described methods, are lower than those necessaryto a safe drinking water!

Table 4shows values of international guidelines, inmost cases only for drinking water safety. The interna-tional guidelines for drinking water present a large vari-ability according to the source of information. Guide-lines for aquatic life protection were scarce, but their


Table 2Main toxicological, physicochemical and persistence characteristics of used pesticidesa

Pesticide Application ratet1/2 in soil t1/2 in water t1/2 in air logKOW Toxicity class

Bentazon 1.2–2 L/ha 14 days 0.6–5 days 0.6–5 days Low affinity to biota EPA III, WHO IIIClomazone 1 L/ha 10–137 days 1.5–7 days – Low affinity to biota EPA III, WHO IIDicamba + metsulfuran-

methyl0.1 L/ha 25–555 + 7–150 days <7 days + >84 days 2 days + Low affinity to biota EPA III, WHO

III + EPA IV,WHO III

Fenoxaprop-ethyl 0.8 L/ha 1–10 days 0.2–11 days – Medium affinity tobiota

EPA III

Glyphosate 4 L/ha 3–174 days 12–70 days – Low affinity to biota EPA III, WHO IIIMolinate 5 L/ha 1–160 days 5–10 days 0.5 –2 days Low affinity to biota EPA IV, WHO IIPyrazosulfuran-ethyl 0.08 L/ha <15 days 28 days – Low affinity to biota WHO IIIPropanil 3–4 L/ha 5–15 days 2 days 1 day Low affinity to biota EPA III, WHO IIIQuinclorac 1.3–1.5 L/ha <14 days – – Low affinity to biota EPA III, WHO IIICarbofuran 7–8 kg/ha 30–120 days 7 days–13 years 0.3–26 days Low affinity to biota EPA I, WHO IbDeltamethrin 0.06–0.08 L/ha 11–72 days 1 day – High affinity to biota EPA II, WHO IIEndosulfan 0.5 L/ha 30–240 days 1–98 days – Medium affinity to

biotaEPA II, WHO I

Lambda-cyhalothrin 0.06–0.08 L/ha 6–84 days 20 days 0.2 days High affinity to biota EPA II, WHO IIMethamidophos 0.6 L/ha 2–12 days 3–309 days 0.6 days Low affinity to biota EPA I, WHO IbMonocrotophos 0.6 L/ha 1–180 days 17–134 days – Low affinity to biota EPA I, WHO Ib

a On grey, dominant criteria to support the decision of sampling for pesticides analysis.

values are in accordance with calculated values, espe-cially for herbicides.

The maximum pesticide value of 0.1�g L−1 estab-lished by the Directive 80/778/EEC for drinking wateris set for no particular pesticide but for all in general.

This value is low enough to be applied to any singlepesticide, and it seems to be more adequate for mostinsecticides, except maybe for deltamethrin. However,it seems to be too much conservative for all the herbi-cides.

Table 3Results of calculation of guidelines

Active substance Most relevant NOAEL(mg kg−1 d−1)

UF RfD GVDW Most relevant LC50 UF GVPAL

Bentazon 10 100 0.1 mg kg−1 d−1 325�g L−1 100 mg L−1 1000 0.1 mg L−1

Clomazone 4.3 100 0.043 mg kg−1 d−1 140�g L−1 5.2 mg L−1 100 0.052 mg L−1

Dicamba 0.13 100 0.0013 mg kg−1 d−1 4.2�g L−1 20 mg L−1 1000 0.02 mg L−1

Fenoxaprop-ethyl 0.75 100 0.0075 mg kg−1 d−1 24.4�g L−1 0.46 mg L−1 100 4.6�g L−1

Glyphosate 10 100 0.1 mg kg−1 d−1 325�g L−1 86 mg L−1 1000 0.086 mg L−1

Metsulfuron-methyl 25 100 0.25 mg kg−1 d−1 0.8 mg L−1 12.5 mg L−1 100 0.125 mg L−1

Molinate 0.2 100 0.002 mg kg−1 d−1 6.5�g L−1 0.18 mg L−1 100 1.8�g L−1

Pyrazosulfuran-ethyl 4.3 100 0.043 mg kg−1 d−1 140�g L−1 30 mg L−1 1000 0.03 mg L−1

Propanil 5 100 0.05 mg kg−1 d−1 163�g L−1 0.14 mg L−1 100 1.4�g L−1

Quinclorac 53 100 5.3 mg kg−1 d−1 17 mg L−1 100 mg L−1 1000 0.1 mg L−1

Carbofuran 0.5 100 0.005 mg kg−1 d−1 16.3�g L−1 0.088 mg L−1 100 0.88�g L−1

Deltamethrin 1 100 0.01 mg kg−1 d−1 32.5�g L−1 0.39�g L−1 100 3.9 ng L−1

Endosulfan 0.57 100 0.0057 mg kg−1 d−1 18.5�g L−1 0.3�g L−1 100 3 ng L−1

Lambda-cyhalothrin 0.5 100 5�g kg−1 d−1 16.3�g L−1 0.21�g L−1 100 2.1 ng L−1

Methamidophosa 0.03 300 0.3�g kg−1 d−1 0.98�g L−1 0.27 mg L−1 1000 0.27�g L−1

Monocrotophosb 0.013 10 0.13�g kg−1 d−1 0.42�g L−1 0.24�g L−1 100 2.4 ng L−1

a For methamidophos, besides the conventional uncertainty factor (100×) it is recommended the use of an additional factor (3×). The use ofthis factor is justified by the evidence of retarded peripheral neuropathologies in humans.

b Study made in humans. Only the interindividual variability was taken in account (10×).


Table 4Compilation of existent guideline values

Pesticide GVDW GVPAL (�g L−1) Reference

Bentazon 0.1�g L−1* Directive no. 80/778/EEC300�g L−1** Tomlin (2000)

Clomazone 0.1�g L−1* Directive no. 80/778/EEC

Dicamba 0.1�g L−1* Directive no. 80/778/EECGVDW = 0.44�g L−1� Caux et al. (1993)GVDW = 120�g L−1� Caux et al. (1993)

10� CCME (2001)

Fenoxaprop-ethyl 0.1�g L−1* Directive no. 80/778/EEC

Glyphosate 0.1�g L−1* Directive no. 80/778/EEC0.2 mg L−1� DOSES (1997)0.7 mg L−1� Nowell and Resek (1994)

65� CCME (2001)

Metsulfuran-methyl 0.1�g L−1* Directive no. 80/778/EEC

Molinate 0.1�g L−1* Directive no. 80/778/EEC6�g L−1** WHO (1993), Tomlin (2000)20�g L−1 US-EPA, 19931�g L−1 Ekstrom andAkerblom (1990)

Pirazosulfuran-ethyl 0.1�g L−1 Directive no. 80/778/EEC

Propanil 0.1�g L−1* Directive no. 80/778/EEC20�g L−1** Tomlin (2000)40�g L−1� US-EPA (1993)1000�g L−1� Ekstrom andAkerblom (1990)

Quinclorac 40�g L−1� US-EPA (2000b)0.1�g L−1* Directive no. 80/778/EEC

Carbofuran 0.1�g L−1* Directive no. 80/778/EEC90�g L−1� Ekstrom andAkerblom (1990)40�g L−1� US-EPA (2000b)30�g L−1� Ekstrom andAkerblom (1990)7�g L−1** Tomlin (2000)5�g L−1** WHO (1998)

1.8� CCME (2001)

Deltamethrin 0.0004�g L−1� Pawlisz et al. (1998)0.1�g L−1* Directive no. 80/778/EEC

0.0004� CCME (2001)

Endosulfan 0.01�g L−1♥ Resolution CONAMA N. 020/860.1�g L−1* Directive no. 80/778/EEC0.35�g L−1� US-EPA (1993)40�g L−1� Ekstrom andAkerblom (1990)74�g L−1� US-EPA (1993)

0.02� CCME (2001)

Lambda-cyhalothrin 0.1�g L−1* Directive no. 80/778/EEC

Methamidophos 0.1�g L−1* Directive no. 80/778/EEC6�g L−1 DOSES (1997)

Monocrotophos 0.1�g L−1* Directive no. 80/778/EEC

Countries in which the legislation is valid: (*) European Union Countries; (**) World Health Organisation; (�) State of New York (USA); (�)Canada; (�) United Kingdom; (�) USA; (�) Australia; (♥ ) Brazil.


Fig. 4. Relationship between calculated guidelines for aquatic lifeprotection (PAL) and drinking water (DW), both in�g L−1.

Comparing the values in these tables, and using aconservative criterion, the lower value for each pesti-cide was used to buildTable 5, which shows the rec-ommended guidelines for water quality protection ofEsteros; in what concerns insecticides in DW, Euro-pean directive value was adopted.Fig. 5shows all theproposed values, for drinking water and for aquatic lifeprotection. Values for deltamethrin are marked with aquestion mark, because some international organismsconsider this insecticide much more dangerous than theothers, requiring lower guideline values.

4.3. Pesticides results

The results of the analysis performed are repre-sented inFigs. 6 (endosulfan) and 7 (carbofuran).

Table 5Recommended guidelines (conservative approach)

Active substance Most relevant guideline value

DW (�g L−1) PAL (�g L−1)

Bentazon 300 100Clomazone 140 50Dicamba 0.4 10Fenoxaprop-ethyl 24 5Glyphosate 200 65Metsulfuron-methyl 800 125Molinate 6 2Pyrazosulfuran-ethyl 124 30Propanil 20 1.4Quinclorac 17 100Carbofuran 5 1Deltamethrin 0.1? 0.004?Endosulfan 0.1 0.003Lambda-cyhalothrin 0.1 0.002Methamidophos 0.1 0.25Monocrotophos 0.1 0.002

Carbofuran was not detected in the sampling pointsin the middle of the Laguna Ibera, in the Bridge and in apoint in the center of the lagoon closer to the rice fields.Mirinay river presented the smallest values among sam-pling points where carbofuran could be detected, andwater from one of the rice fields had the largest con-centrations of carbofuran. According to the value of theCanadian guideline of 1.8�g L−1, the values found donot represent a risk to the aquatic life. However, these

uidelines (conservative approach).
Fig. 5. Recommended g


Fig. 6. Sampling places and results for the pesticide endosulfan in the three campaigns (1, June 2000; 2, November 2000; 3, March 2001).DL—detection limit = 0.025�g L−1; recommended guideline = 0.003�g L−1.

values are less than one order of magnitude under thisguideline, and, specially in the rice field, the values areclose to the calculated guideline of 1�g L−1.

Endosulfan could not be quantified in all the samplescollected in the middle of laguna Ibera, in “Island”, andin the two first samples collected in the “Bridge” and in

the center of the lagoon, because the values were alsounder the detection limit of 0.025�g L−1. However, inthe case of endosulfan, this does not mean that thereis no risk: Canadian guideline is 0.02�g L−1, and thevalue calculated for this insecticide was 0.003�g L−1.In fact, the method of analysis should be more sensi-

Fig. 7. Sampling places and results (�g L−1) for the pesticide carbofuran in the three campaigns (1, June 2000; 2, November 2000; 3, March2001). DL—detection limit = 0.025�g L−1; recommended guideline = 1�g L−1.


tive. On the other hand, all other samples had highervalues, from 0.2 to 1.1�g L−1 in the canals, and from0.4 to 13.5�g L−1 in the water samples collected in ricefields. In all the cases, there is a risk due to the presenceof endosulfan for aquatic biota! In soils the risk maybe higher because endosulfan has more affinity to soilthan to water.

If European law is considered, the use of this waterfor human consumption represents a risk due to thepresence of both pesticides. If all the other guidelines,including those calculated, are considered, then risksare only due to endosulfan. A specific water treatmentshould therefore be implemented. While this solution isnot implemented, water for human consumption shouldbe taken from the middle of the lagoon, farther awayfrom rice fields’ discharges.

In fact, the results show that the concentration ofboth pesticides diminishes from the point were theyare directly applied to the point of discharge, and itseems to disappear at longer distances, maybe due todilution; being persistent pesticides, its transformationis unlikely. Considering these results and the amount ofpesticides applied in these rice fields, it is also probablethat methamidophos and monocrotophos are presentin water in concentrations that represent risk. In whatconcerns the other insecticides, also very toxic, they arenot very persistent and are used in smaller quantities;concentrations below detection limits are expected.Herbicides, some of them used at higher quantities andpersistent, can also be present but in concentrationsu hani

d int auset nceo m-p orko theE ringp

bda-c e re-s e tot andb

sen-s esti-c ls.

5. Conclusions

As a main conclusion, it can be assumed that someof the present agricultural practices seem to have al-ready some impacts in the ecosystem. It is especiallyimportant to take into account the future agriculturaldevelopment of this region in order to allow the evalu-ation of the evolution of impacts and to identify the mo-ment where preventive or remediation measures needto be implemented to guarantee the sustainability of theecosystem. At present, water quality of the Esteros, inwhat concerns pesticide contamination, seems to rep-resent risk only close to the points of discharge, due tothe more toxic insecticides, as endosulfan, methami-dophos and monocrotophos. Some more data shouldbe obtained in order to better quantify the impact ofpesticides emissions on the water quality of the lagoonsand a monitoring program should be implemented. In afuture monitoring plan of the region, the herbicides clo-mazone, dicamba, glyphosate, metsulfuron-methyl andmolinate and the insecticides carbofuran, deltamethrin,endosulfan, lambda-cyhalothrin, methamidophos andmonocrotophos should be analysed.

Acknowledgements

We gratefully acknowledge the European Commis-sion for financial support through the project: “Thesustainable management of wetland resources in Mer-c 2).W ject,C

R

Awith

cides

B tionsar

ol-

B ationy of

C ana-ife.

nder the risk level, since they are less toxic tnsecticides.

More pesticide analysis should also be performehe future, specially in water and soil samples, beche results of Mackay’s model shows the preferef pesticides for distribution in water and soil coartments. The pesticides not analysed in this wr new pesticides introduced in the fields aroundsteros should be analysed in the future monitolan.

Some of these pesticides (carbofuran, lamyhalothrin, monocrotophos, methamidophos) havtricted uses in other countries (USA and EU) duhe danger that their formulations pose to mammalsirds (EXTOXNET, 1995; Brown, 2000).

Rice producers should be formed, informed anditised to search for alternatives to the most toxic pides and to follow the information given in the labe

osur” (EC contract number ERB IC18-CT98-026e also acknowledge the Coordinators of this prolaudio Rossi and Steven Loiselle.

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