Science of the Total Environment 598 (2017) 1106–1115

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Potential of vegetated ditches tomanage organic pollutants derived fromagricultural runoff and domestic sewage: A case study inSinaloa (Mexico)

Monika Moeder a,⁎,1, Otoniel Carranza-Diaz b, Gabriela López-Angulo c, Rito Vega-Aviña d,Francisco Armando Chávez-Durán e, Seifeddine Jomaa f, Ursula Winkler a, Steffi Schrader a,Thorsten Reemtsma a, Francisco Delgado-Vargas c,1

a UFZ-Helmholtz Center for Environmental Research, Department of Analytical Chemistry, Permoserstrasse 15, 04318 Leipzig, Germanyb Marine Sciences Faculty, Autonomous University of Sinaloa, Paseo Claussen S/N, Col. Centro, CP 82000 Mazatlán, Sinaloa, Mexicoc Facultad de Ciencias Químico Biológicas, Universidad Autónoma de Sinaloa, Ciudad Universitaria s/n, CP 80010 Culiacán, Sinaloa, Mexicod Facultad de Agronomía, UAS, Carretera Culiacán-El Dorado km 17.5, CP 80000 Culiacán, Sinaloa, Mexicoe Comisión Nacional del Agua, Organismo de Cuenca Pacífico Norte, Dirección de Infraestructura Hidroagrícola, Ingeniería de Riego y Drenaje Distrito de Riego 010 Culiacán-Humaya, Mexicof UFZ-Helmholtz Center for Environmental Research, Department of Aquatic Ecosystem Analysis and Management, Brueckstrasse 3a, 39114 Magdeburg, Germany

H I G H L I G H T S G R A P H I C A L A B S T R A C T

• Vegetated ditch with high capability tomanage organic pollutants received fromagricultural runoff and urban sewage.

• Pollution sources and seasonality ofpollutants` pattern identified by multi-site sampling along the ditch over 2013.

• Spatio-temporal distribution of pollutantsderived from consumer behavior, agricul-tural activities and climate conditions.

• Low accumulation of pollutants in sedi-ments; Typha domingensis plants absorbed10 of 38 organic pollutants monitored.

• Endosulfan lacton, a less considered me-tabolite of endosulfan appeared in ditchwater at almost all sites during 2013.

• The concentrations of all target pollut-ants decreased during their transportthrough the ditch.

Abbreviations: AHTN, 6-acetyl-1,1,2,4,4,7-hexamethylsulfate, endosulfan lactone and -sulfate; HHCB, 1,3,4,6,7,8-h⁎ Corresponding author.

E-mail address: monika.moeder@ufz.de (M. Moeder).1 Equal contribution.

Photo: Francisco Delgado-Vargas (Facultad de Ciencias Químico Biológicas, Universidad Autónoma de Sinaloa,Ciudad Universitaria s/n, CP 80010 Culiacán, Sinaloa, México).

a b s t r a c t

a r t i c l e i n f o

Article history:Received 28 February 2017Received in revised form 16 April 2017Accepted 19 April 2017Available online xxxx

This case study presents the fate of selected organic, priority and emerging pollutants along a 3.6 km sector of avegetated, agricultural ditch situated in Sinaloa (Mexico). The ditch receives runoff of agriculture and domesticwastewater from an adjacent community. During 2013, the occurrence of 38 organic pollutants (pesticides, poly-cyclic aromatic hydrocarbons (PAHs), artificial sweeteners and pharmaceutical residues) wasmonitoredmonth-ly at five selected points in the ditch water. Additionally, sediment and Typha domingensis (cattail) plants were

tetraline; BPA, bisphenol A; CBZ, carbamazepine; DO, dissolved oxygen; DT, disappearance time; d.w., dry weight; ES lactone/ESexahydro-4,6,6,7,8,8-hexamethylcyclopenta-γ-2-benzopyran; ORP, oxidation-reduction potential; t-NP, technical nonylphenol.

1107M. Moeder et al. / Science of the Total Environment 598 (2017) 1106–1115

Editor: Jay Gan

collected inMarch, June, and September 2013 and investigated concerning their ability to absorb and accumulatepollutants. The concentrations of the selected pollutants in the ditchwater ranged from sub ng L−1 (metolachlor,atrazine) to μg L−1 (metalaxyl, acesulfame). Themetabolites endosulfan sulfate and endosulfan lactone exceededmostly the concentration of the precursor insecticide endosulfan. Sorption on sediments was of minor relevancefor accumulation of pollutants in the ditch system. Concentrations in the sediments varied seasonally and rangedfrom 0.2 to 12,432 μg kg−1 dry weight (d.w.). T. domingensis accumulated ten of the studied pollutants mainly inroots (5–1065 μg kg−1 d.w.). Overall, the monitoring results of the ditch compartments indicated that down-stream the concentrations of the target pollutants decreased. Under no-flow conditions in the hot season, theditch revealed a noticeable potential to mitigate pollutants. Among the high microbial activity in the water andthe subtropical climate conditions, the ditch vegetation contributed to natural attenuation of the selectedpollutants.

© 2017 Elsevier B.V. All rights reserved.

Keywords:Vegetated ditchPriority and emerging pollutantsWater qualityPlant uptakeEndosulfan lactone

1. Introduction

The use of vegetated ditches to drain agricultural fields has long tra-dition. Their ability to reduce nutrients such as nitrate and phosphate, tocapture eroded particulate matter and to mitigate pesticides receivedfrom runoff has been proved inmany investigations usingmodel exper-iments and field trials (Iseyemi et al., 2016; Needelman et al., 2007;Montakhab et al., 2012; Faust et al., 2016; Stehle et al., 2011). Werneret al. (2010) documented that a decrease of selected pesticides inditchwater and sedimentwas not strictly accompanied by reduced tox-icity towards the aquatic ecosystem. Particularly, permethrin relatedtoxicity to amphipods Hyalella aztecawas hardly reduced after passagethrough a 400 m long ditch sector. Reasons for the still present toxic ef-fects were not discussed but could be caused by chemicals with syner-gistic effects like transformation products of pesticides or substancesincluded in pesticide formulations or other pollutants acting finallytoxic as multicomponent mixture. Previous investigations concerningorganic pollutants in vegetated drainage ditches were focused on thefate of pesticides and derived consequences for ditch water qualityand deleterious effects on downstream ecosystems. Technically moresophisticated and controlled are wetland technologies that have beenapplied to mitigate a broader range of contaminants arising from agri-cultural as well as urban/industrial sources (Vymazal and Březinová,2015; Seeger et al., 2011; Li et al., 2014). The construction of agriculturaldrainage ditches includes mostly defined buffer zones and special re-gions sown with selected plant species. Uncontrolled and self-regulat-ing colonization by typical local perennial plants complies also withthe issue to protect riparian strips from erosion and helps to maintainthe drainage system. Furthermore, vegetated agricultural ditches pro-vide long-term benefits for biodiversity and ecosystem services in thesurrounding area because they create new habitats for many organisms(Herzon and Helenius, 2008). Although the collection of wastewater inopen ditches is forbidden in most countries, in regions with less devel-oped infrastructure for wastewater treatment, agricultural ditchesoften receive untreated domestic sewage containing a cocktail of sub-stances such as household chemicals, personal care products and phar-maceutical residues. Also irrigation of crops with wastewater - acommon practice inwater scarce regions, can introduce sewage-relatedpollutants into ditchwater (Carillo et al., 2016). Furthermore, biosludgeapplied as fertilizer on fields can release veterinary drugs inclusive anti-biotics into draining ditches enhancing the risk to spread antibacterialresistance. Many studies were focused on individual farming practicesand their influence on the local water quality and water resources.The amount of runoff, loss of soil and mitigation of nutrients and pesti-cides along vegetated ditches were evaluated in fortification experi-ments as well as field studies. For instance, Otto et al. (2016)investigated the transport of mesotrione, S-metolachlor andterbuthylazine into a vegetated ditch by simulating extreme runoffevents. Moore et al. (2011) could demonstrate that within vegetatedditches draining alfalfa and tomato fields, chlorpyrifos and permethrinwere decreased by 20% and by 67%, respectively. Sorption of pesticides

to soil, sediment, and submerged plants can noticeably contribute totheir mitigation in the complex ditch habitats (Rogers andStringfellow, 2009; Bennett et al., 2005). Designed field trials or labora-tory batch experiments were carried out to model the fate of selectedpesticides under defined conditions (Elsayed et al., 2014). The behaviorof emerging pollutants discharged with urban sewage into agriculturalditches has not been investigated yet, probably due to more prominentimpacts expected from pesticides, nutrients and pathogenic germs.Until 2012, for instance inMexico, only 50% of the totalwastewater pro-duced was treated (Mora-Ravelo et al., 2017) and if wastewater wasintended for reuse, the removal of pathogens had priority (Jiménez,2005). However, previous research indicated ecotoxic effects of emerg-ing pollutants occurring commonly at ppb or ppt concentrations.Reprotoxicity, formation of antibacterial resistance and combinationtoxicity in complexmixtureswere identified as lasting effects on aquaticecosystems (La Farré et al., 2008; Cleuvers, 2004). For our study, a sectorof an agricultural vegetated ditch in Sinaloa (Mexico) was selectedwhich is part of a spacious ditch network draining the fields and sup-plies water for irrigation (USDA, 2013). The ditches are often routedinto estuarine zones where aquaculture is established thus, ditchwater pollution represents a potential risk for local environment, foodproduction, and water resources of this region. The district of Sinaloais known for intensive agriculture with several crop rotations over theyear. During the studied period, tomatoes, corn, cucumber and bell pep-perwere cultivatedwhereby the application of different pesticides suchas lambda-cyhalothrin, metolachlor, chlorpyrifos, endosulfan, dimetho-ate and metalaxyl were very probable (PAN, 2012). Additional to agri-cultural runoff, the studied drainage ditch received domestic sewagedischarged by an adjacent community with little companies. Thus, theditch water collects pollutants of both agricultural and urban activities(e.g., pesticides, household chemicals, pharmaceutical residues, indus-trial chemicals). Till now, only little information on the occurrence of or-ganic pollutants in Mexican drainage systems is available. The sorptionof alkylbenzene sulfonates and antibiotics (sulfamethoxazole, ciproflox-acin) on soils irrigated with wastewater was investigated in a study byCarillo et al. (2016) and persistent organic pollutants like DDT, DDE,and polychlorinated biphenyls were monitored in municipal wastewa-ter which was intended for irrigation in agriculture (Beraud-Lozano etal., 2008; García-Hernández et al., 2013). Thus, an issue of our studywas to acquire data on the occurrence and distribution of 38 organicpollutants in water, sediment and plants in a vegetated ditch. The cen-tral point of our field study inMexicowas the question, how do agricul-tural vegetated ditches manage the great variety of substancesdischarged from several sources. The spatio-temporal profile of pollu-tion was determined to assess the potential of the ditch sector to miti-gate pollution and to evaluate the risks for accumulation ofcontaminants in ditch compartments. Following the literature reviewperformed, our study is the first quantitative monitoring of emergingpollution in a 3.6 km long vegetated ditch receiving agricultural drain-age and sewage continuously along its longitudinal section and operat-ing under subtropical climate in Sinaloa (Mexico).

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2. Materials and methods

2.1. Sampling sites

The part of the vegetated draining ditch called “LaMichoacana” is lo-cated in the region of Sinaloa (Mexico) with intensive agriculture (GPScoordinates see Table S1 in the electronic Supplementarymaterial). The3.6 km long ditch sector studied was part of a draining ditch of about30 km length. The ditch with a semicircular profile was in mean 4.5 mwide and 2m deep. The vegetated ditchwas embedded in a plane land-scape characterized bymany small fields cultivated with different cropsover the year (Fig. 1). Typical period for pesticide application rangedfromNovember to February and followed crop rotations. Detailed infor-mation on applied pesticides (time and amounts) was not available.

Five sampling sites were selected as representative hotspots consid-ering different permanent and sporadic input of runoff and untreatedwastewater released from the small rural neighborhood “LaMichoacana” (about 1200 inhabitants) and trade companies along thedrainage systems. At some places, solid waste was deposited illegallyin the ditch, too.

The highest density of population is around sites 2 and 3, followed bysites 4 and 1 (“inlet” to the ditch sector studied). Close to site 1, apacking company handled fresh fruits and vegetables and at site 5,the “outlet” of the studied ditch part, a companymanufactured fertil-izers. Upstream the ditch, the landscape was characterized by furthercrop fields and little communities with streets running parallel to theditch.

The permanent vegetation within the ditch consists of numerousspecies (Table S2), whereas Typha domingensis, Amaranthus palmeriand Urochloa muticawere dominant along the ditch. In 2013, the mete-orological conditions in the studied regionwere characterized by an an-nual mean air temperature of 25 °C (Fig. S1). Main precipitation periodwas from June to December withminimum 10mmm−2 in October anda peak in September 18th provoked by the tropical storm “Manuel”with300mmm−2 rainwhich caused flash floods in the studied region inclu-sive flooded draining ditches (Fig. S2).

2.2. Sample characteristics: water, sediment, and plants

Water temperature, pH-value, oxidation-reduction potential (ORP),dissolved oxygen (DO), conductivity and total dissolved solids (TDS)were measured in each water sample. Hydraulic conditions includingwater level and flow rates were determined on-site by Chávez-DuránF.A. of CONAGUA (Comision Nacional del Agua,Mexico).Water temper-atures varied from 12 °C (February) to 28 °C (June) giving an annualmean of 22 °C. Over the year, mostly anoxic, reductive conditionsprevailed in the ditch water and pH values ranged from 7 to 8.8. Moredetailed data are shown in Table S1 and Fig. S3 in the Supplementarymaterial.

Water levels changed seasonally from partially dryness to floodedconditions. Due to the input of untreated domestic sewage near sites2, 3, and 4, the ditch was fed with water over the whole year (TableS1). At sites 1 and 5, the ditch was almost dry from June to August andwater sampling was difficult or even impossible. During the hurricane“Manuel”, the ditch and adjoining areas were flooded for days. As con-sequence, flow rates of the drain water varied from 0 to 150 L s−1

(Table S1). The sanitation status of the water in the vegetated ditch sec-tor was described previously (Ahumada-Santos et al., 2014).

Sediment samples were characterized as sandy-silt with Total Or-ganic Carbon contents (TOC) ranged from 1.1% (site 3) to 4.7% (site 1)and Total Nitrogen (TN) contents between 0.1% and 0.3%.

Typha domingensis (cattail) plants of about 2 m high growing in thewater were harvestedwith roots for analysis of the absorbed pollutants.A more detailed overview on the identified plant species in the ditch isprovided in Table S2.

2.3. Target substances

Since the ditch was fed by domestic sewage and runoff from agricul-turalfields, the substances selected formonitoringwere typical pollutantsrepresenting both influences. Information on the use of pesticides inMex-ico (Pèrez-Olvera et al., 2011) aswell as data on theworldwide increasingproduction and discharge of pharmaceutical residues and householdchemicals served as pivotal arguments for selecting the target substances(WHO, 2012). The properties of the 38 selected target pollutants cover abroad range of polarity andpersistency as shown in Table S3. 15 represen-tatives of polycyclic aromatic hydrocarbons (PAHs) were included in themeasurements (EPA-PAH, 2008) while naphthalene was excluded frommonitoring due to analytical problems. Acesulfame a typical sewage-related contaminant (Gan et al., 2013) was selected as representative ofthe group of artificial sweeteners of which the distribution profile wasdetermined in preliminary analyses in January 2013 (Fig. S5).

2.4. Sampling, sample preparation and analysis

Samples were taken from the ditch water at five selected sites in themiddle of each month from February to December 2013. Additionally,sediments and cattail plants (T. domingensis) were taken at each sitein March, June, and September 2013. Water samples (250 mL) were fil-tered and extractedwith solid phase extraction (SPE) using “Oasis HLB”sorbent (Waters Corp., Eschborn, Germany). Sediment sampleswere airdried, homogenized, sieved, and extracted by accelerated solvent ex-traction with in-cell cleanup (ASE, Dionex/Thermo Fisher Scientific,Germering, Germany). T. domingensis plants were separated into root,stem, and leaves which were dried, grinded, and homogenized priorto dispersive solid phase extraction (QuEChERS). For analysis of the tar-get analytes, liquid chromatography coupled to tandemmass spectrom-etry and gas chromatography–mass spectrometry were used. Methodlimit of quantification (LOQ) ranged from 0.2 ng L−1 (thiacloprid) to30 ng L−1 (endosulfan) for water samples. The method for sedimentanalysis was characterized by LOQs between 0.05 ng g−1 d.w.(acesulfame) and 50 ng g−1 d.w. (endosulfan lactone). For plant analy-sis, LOQs between 0.05 ng g−1 d.w. (thiacloprid) and 40 ng g−1 d.w.(endosulfan lactone) were obtained. Precision as mean relative stan-dard deviations (%RSD) for water analyses was 15%, 11% for the sedi-ment, and 12% for plant analyses. The respective protocols aredescribed in detail in the Supplementary material. The performance ofthe analytical methods applied is provided in Table S8.

3. Results and discussion

3.1. Occurrence of organic pollutants in ditch water

The target substances selected for monitoring belong to the groupsof priority pollutants (US EPA, 2012; ECWFD, 2008) and non-regulatedpesticides and emerging pollutants associated with urban discharges.The monitoring program comprised pesticides like endosulfan and p,p′-DDT, which are partially regulated but not restricted fromuse byMex-ican legislation in contrast to US EPA and European rules (UNEP, 2011;Pèrez-Olvera et al., 2011).

In the ditch water the pollutants occurred with significant spatialand temporal variations whereat most of them were not found perma-nently at all sites (Table 1).

3.1.1. Pollutants from agricultural activitiesThe pesticides chlorpyrifos, dimethoate, bentazone, metalaxyl, and

endosulfan occurred at concentrations below 50 ng L−1 but at differenttimes and sites, high concentrations appeared due to a short pulsedinput (Figs. S4, S5).

InOctober, thepeak concentrations of bentazone anddimethoatewereprobably caused by the intensive runoff associated to the hurricane“Manuel” in September 2013. Highest concentrations of both pesticides

Fig. 1. Sampling sites 1–5 at the sector of the vegetated draining ditch studied in Sinaloa (Mexico)with the small community “LaMichoacana” and the “FERPAC”-company for agriculturalgoods near site 5.

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were observed at site 1 followed by a plume-like decrease downstream tosite 5. If these pesticides were released from fields nearby site 1 ortransported from upstream was not further investigated. Still before thehurricane in September, metalaxyl appeared with maximum concentra-tions at site 1 and decreased with spatial trend to site 4 (Fig. S4). A slightincrease at site 5 let assume an additional input from fields nearby site 5.After thehurricane inOctober,metalaxylwasdetected at only lowconcen-trations at all sites until the end of themonitoring period. Chlorpyrifoswasdetectedwithhighest concentrations in February. Its distribution along theditch suggested an input at site 3 and further sources upstream(Fig. S4). Ingeneral, within the following three months after the peak pollution, theconcentrations of the pesticides ebbed away so that they were hardlytraceable in the ditchwater. Amongdilution and transport, biotransforma-tion processes can reduce these pesticideswith half-life times between 15and 36 days (Table S3). The water soluble and quite persistent bentazone(t1/2 (water) = 716 days) decreased gradually along the flow path. Sorp-tion to sediment and uptake by plantswas not observed thus, dilutionwasassumed as main factor decreasing bentazone. Since bentazone has beenreported less stable in soil (t1/2 = 14 days, Table S3), its amount leachedfrom fields decreased with time and contributed to a lesser extendto water load. Also the rapid subside of metalaxyl was surely affected bydilution (Fig. S4). Still before the hurricane, a water flow rate of540,000 L h−1 was estimated at site 5 where thewater left the investigat-ed ditch sector. Under these conditions, 3.3 mg metalaxyl, 7.7 mgbentazone, 3.8 mg chlorpyrifos and 3.5 mg dimethoate were transportedper hour out of the ditch (Table S4). At moderate flow in May(6120 L h−1 at site 5), only 13 μgmetalaxyl, 176 μg bentazone, 49 μg chlor-pyrifos were transported per hour. Dimethoate was not detected in May.The peak concentrations observed for the pesticideswere at levels causingbiological effects considering for instance, regulations of the United States.In February, the concentrations of chlorpyrifos ranged from 185 ng L−1

(site 5) to 771 ng L−1 (site 3) which exceeded the acute aquatic toxicitybenchmark value for invertebrates (40 ng L−1) as well as the criterionfor maximum concentration in fresh water (83 ng L−1) developed byU.S. EPA (US EPA, 2012). As reported previously, applications of chlorpyr-ifos to grapes, soybeans, corn, cotton or alfalfa in California (USA) werereflected by concentrations in surface water ranged from 100 ng L−1 to400 ng L−1 (Zhang et al., 2012; WHO, 2004; CDPR, 2014).

In October only at site 1, the concentration of dimethoate(3563 ng L−1) exceeded the aquatic life benchmark value set by USEPA for invertebrates (0.0215 μg L−1, EPA, 2008). Bentazone possessinglow toxicity to most target organisms reached concentrations up to432 ng L−1, which were still within the established secure levels.

Although the drainage systems in Sinaloa are not subjected to re-strictions concerning ecologically compatibility or human health care,

the ecosystem established on the ditch may suffer from the amount ofcontaminants exceeded sometimes trigger values verified to cause ad-verse biological effects.

The insecticide endosulfan is considered as priority pollutant andhas been banned or restricted for use in many countries but it is autho-rized for use in Mexico (UNEP, 2011; Pèrez-Olvera et al., 2011). Endo-sulfan was detected only temporarily with a peak concentration inJune at 8656 ng L−1 on site 1 probably caused by intensified runofffrom June to October (Fig. S2). As in cases of the other pesticides, endo-sulfan concentrations decreased in flowdirection to site 5where amax-imum of 350 ng L−1 were detected. Literature data, for instance from anAustralian study, documented up to 10,000 ng L−1 endosulfan in runoffwater from cotton fields after seven days of aerial application and inriver water between 20 and 200 ng L−1 (Kennedy et al., 2001). Consid-ering for instance the trigger value of 30 ng L−1 set for protecting freshwater in Australia (ANZ, 2000), the endosulfan concentrationmeasuredin the ditch water exceeded this level but only within a short period.High endosulfan concentrations as reported for ditch water in BritishColumbia (Canada) at 1530 μg L−1 were never reached in our monitor-ing study (Schulz, 2004). Although endosulfan was not permanentlypresent above LOD, its metabolites endosulfan sulfate and particularlyendosulfan lactone were found in June at site 1 and from Septemberto December at all sites (Fig. S5). Endosulfan sulfate was detected onlysporadically at concentrations between 4 and 197 ng L−1 but endosul-fan lactone reached concentrations up to 2000 ng L−1 (Fig. S5). Thepresence of both ES lactone and ES sulfate already before the peak con-centration of endosulfan appeared let assume former applications onfields upstream in 2012. The occurrence of endosulfan lactone (ES-lac-tone) in environment is less documented than that of endosulfan sulfatewhich was reported for surface water at concentrations between2 ng L−1 and 628 ng L−1 by Starner (2007). The ES-lactone is knownas product of aerobic degradation of endosulfan (Kafilzadeh et al.,2015; Tiwari and Guha, 2013) thus, its formation in anoxic ditchwater was hardly conceivable but in field soil, endosulfan is degradedwith t1/2 (soil) of 86 days (Table S3). While endosulfan sulfate hasbeen proved as more persistent and equally toxic than endosulfan, thetoxicity of endosulfan lactone is still unknown (EPA, 2002).

Pesticides classified as priority pollutants (EC WFD, 2008) were de-tected only at trace concentration and not at all sites. Atrazine was de-tected at maximum concentration of 7 ng L−1 that is much belowconcentrations found in watersheds or even drinking waters in USA(Dalton et al., 2014; Wu et al., 2010). Concentrations of p,p′-DDT(DDT) occurred at maximum 504 ng L−1 and p,p′-DDE (DDE) up to447 ng L−1. A seasonal and local dependent distribution was not ob-served. p,p′-DDD was never detected. The DDT/DDE-ratio, often used

Table 1Annual minimum, maximum and mean concentrations (ng L−1) of pollutants in the ditch water at sampling sites 1–5. Standard deviations given in ±ng L−1, * included in the list of priority pollutants (US EPA and ECWater Directive), means werecalculated from (n) samples above the LOQ, bold marked: annual maximum values.

Site 1 Site 2 Site 3 Site 4 Site 5

Min Max Mean (n) Min Max Mean (n) Min Max Mean (n) Min Max Mean (n) Min Max Mean (n)

Pharmaceutical residuesKetoprofen bLOQ 223 ± 7 21(3) bLOQ 130 ± 4 30(4) bLOQ 232 ± 7 57(5) bLOQ 73 ± 2 18(11) bLOQ 20 ± 1 3(2)Naproxen 22 ± 1 934 ± 65 390(11) 17 ± 1 768 ± 54 219(11) 67 ± 5 2438 ± 171 436(11) bLOQ 649 ± 45 210(10) 8 ± 1 109 ± 8 42(4)Propranolol bLOQ bLOQ bLOQ bLOQ 26 ± 15 5(4) bLOQ 235 ± 1 45(3) bLOQ 8 ± 0.4 2(4) bLOQ 7 ± 0.3 17(2)Ibuprofen bLOQ 285 ± 11 56(9) bLOQ 4986 ± 199 520(9) bLOQ 516 ± 21 150(9) bLOQ 1062 ± 42 298(9) bLOQ 88 ± 3 20(9)Diclofenac bLOQ 377 ± 56 142(9) bLOQ 580 ± 87 162(9) bLOQ 185 ± 28 79(9) bLOQ 275 ± 41 91(9) bLOQ 55 ± 8 19(9)Carbamazepine bLOQ 68 ± 2 10(8) 2 ± 0.1 70 ± 2 18(11) 7 ± 0.2 101 ± 3 34(11) 8 ± 0 83 ± 2 35(11) 5 ± 0.1 26 ± 1 11(10)

Food related compoundsAcesulfame 364 ± 15 4072 ± 163 2127(10) 490 ± 20 9683 ± 387 3023(11) 487 ± 19 8396 ± 336 2350(10) 375 ± 15 6826 ± 273 2539(11) 97 ± 4 406 ± 16 261(11)Caffeine 23 ± 1 1555 ± 47 634(10) 21 ± 1 1393 ± 42 413(11) 35 ± 1 1242 ± 37 366(11) 193 ± 6 946 ± 28 440(11) 19 ± 1 617 ± 2 317(10)

HerbicidesAtrazine* bLOQ 2 ± 0.1 1(4) bLOQ 2 ± 0.1 1(3) bLOQ 6 ± 0.2 1(3) bLOQ 6 ± 0.3 1(3) 2 ± 0.1 7.0 ± 0.3 3(11)Metolachlor bLOQ 3 ± 0.1 1(5) bLOQ 31 ± 0.1 1(3) bLOQ 3 ± 0.1 1(3) bLOQ bLOQ bLOQ bLOQ 3 ± 0.1 n = 1Bentazone bLOQ 386 ± 12 57(9) bLOQ 213 ± 6 34(9) bLOQ 176 ± 5 38(9) bLOQ 134 ± 4 34(9) bLOQ 94 ± 3 19(9)

InsecticidesChlorpyrifos* bLOQ 392 ± 23 53(10) bLOQ 475 ± 28 64(9) bLOQ 771 ± 46 82(8) bLOQ 632 ± 38 68(10) bLOQ 195 ± 12 37(7)Carbofurane bLOQ 38 ± 0.4 7(7) bLOQ 9 ± 0.1 3(7) bLOQ 7 ± 0.1 3(7) bLOQ 133 ± 0.1 43(8) bLOQ 11 ± 0.1 5(10)Dimethoate bLOQ 3831 ± 268 413(7) bLOQ 315 ± 22 44(6) bLOQ 46 ± 3 13(7) bLOQ 47 ± 3 11(7) bLOQ 11 ± 1 3(5)Thiacloprid bLOQ bLOQ bLOQ bLOQ 15 ± 1 1(2) bLOQ bLOQ bLOQ bLOQ bLOQ bLOQ bLOQ bLOQ bLOQp,p′-DDE* bLOQ 332 ± 46 163(2) bLOQ 447 ± 62 265(3) bLOQ 390 ± 55 240(3) bLOQ 332 ± 46 229(3) bLOQ 341 ± 48 171(2)p,p′-DDT* bLOQ 319 ± 96 80(2) bLOQ 350 ± 105 158(2) bLOQ 453 ± 136 170(3) bLOQ 504 ± 151 191(2) bLOQ 278 ± 83 139(2)λ-Cyhalothrin bLOQ bLOQ bLOQ bLOQ 322 ± 93 129(3) bLOQ 287 ± 83 n = 1 bLOQ 185 ± 53 46(2) bLOQ 140 ± 41 70(2)Endosulfan* bLOQ 8656 ± 1558 2164(2) bLOQ 2959 ± 532 1212(2) bLOQ 1252 ± 225 n = 1 bLOQ 1268 ± 228 n = 1 bLOQ 350 ± 63 n = 1

FungicideMetalaxyl bLOQ 8429 ± 253 790(9) bLOQ 4684 ± 140 444(8) bLOQ 4040 ± 121 383(8) 3 ± 0.1 4129 ± 124 392(11) 1.0 ± 0.0 6163 ± 185 807(11)

Fuel relatedSum PAH* 141 ± 21 646 ± 97 430(4) bLOQ 820 ± 123 363(3) bLOQ 462 ± 69 171(2) bLOQ 482 ± 72 178(2) bLOQ 162 ± 24 n = 1

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as indicator for acute application of DDT, ranged from 1.1 at site 5 tomaximum 2.2 at site 4 in June. In countries where DDT is still used, con-centrations of DDT in riverwater ranged from 2.4 ng L−1 to 6121 ng L−1

and the respective ratios of DDT/DDE + DDD from 4 to 61 indicatingrather fresh application of DDT (Yadav et al., 2015).

Although in Mexico production and use of DDT has been regulatedfollowing the North American Regional Action Plan (CEC, 2003), theconcentrations of DDT and its metabolite DDE found in the ditchwater pointed to a former DDT application or an input via aerial, parti-cle-bonded transport. Such diffuse input of DDT can led to concentra-tions in surface water of 1–3 ng L−1 as reported from regions inTurkey (Karadeniz and Yenisoy-Karakaş, 2015).

Due to their low water solubility (Table S3), the insecticide lambdacyhalothrin and the selected PAHswere detectedwithmaximumvaluesof 322 ng L−1 and 820 ng L−1, respectively (Table 1).While cyhalothrinwas found only occasionally, PAHs were observed during the wholemonitoring with decreasing tendency from site 1 to site 5. Mostly ace-naphthylene, phenanthrene, and anthracenewere detected butwithoutany seasonally dependent variations.

3.1.2. Pollutants from untreated domestic sewageIn contrast to pesticides received temporarily with runoff or irriga-

tion water, substances typically associated with domestic sewage suchas pharmaceuticals, household chemicals and food additives enter theditch with an urban rhythm of communities and companies. Themajor sources of sewage input were clearly identified at sites 2–4. Theconcentrations of the sewage related pollutants found in the ditchwater followed seasonal trends.

Caffeine and the artificial sweetener acesulfame (ACS) were detect-ed at all sites and sampling dates, indicating a fairly constant input. Dueto their good water solubility, both substances can wide spread inaquatic environment (Lange et al., 2012). Both compounds can serveas indicators implying the impact of aquatic systems by municipalwastewater (Jekel et al., 2015; Buerge et al., 2003, Buerge et al., 2009).

Concentrations of ACS in the ditch water ranged from 97 ng L−1

(Nov./site 5) to 9683 ng L−1 (June/site 2) (Table 1). Its spatial distribu-tion revealed sites 2, 3, and4 asmain input of domestic sewage,which isin accordance with the highest population density around these sites(Figs. 1 and 2). The seasonal variations of ACS reflected finally the in-creased consumption of low-calorie beverages in summer time (Fig. 2).

Over the whole monitoring period, mean concentrations of ACS werelowest at site 5A decrease by factor of about 10 was observed over thedistance of 1.3 km from site 4 to site 5 (Table 1). Among reduced inputsof domestic sewage and dilution, transformation of ACS along the flowpath was found to be most likely. Although ACS is known as persistentfrom studies of wastewater treatment (Jekel et al., 2015), it can be de-graded in environment (t1/2 = 9 days) especially when photolysis ac-companies biodegradation (Gan et al., 2014; Castronovo et al., 2017).

At no-flow conditions as prevailed from June to August (Table S1),the ditch turned into an “isolated batch system” where the permanentinput of wastewater was balanced with the evaporation of water.Under these “no-flow” conditions, long hydraulic retention probablypromoted the transformation of ACS.

In September at high water flow conditions, about 107 mg h−1 ofACS left the ditch sector at site 5 with the potential to be well spreadin aquatic systems (Table S5).

Since ACS accounts for only a third of artificial sweeteners deter-mined in the water, then higher concentrations have to be consideredfor this group of pollutants (screening results see Fig. S6). Toxic effectsof sweeteners are still under discussion and respective effect levels arenot available yet (Sang et al., 2014).

The concentrations of ACS in the ditch water were comparable withthose detected for instance in river Rhine (700ng L−1–1900ng L−1) butthey were much lower than found in effluents of wastewater treatmentplants measured between 10,000–40,000 ng L−1 (Lange et al., 2012).

The concentrations of caffeine followed a seasonal trend but less sig-nificantly than ACS although both substances are often combined inbeverages (Fig. 2). The drain water contained between 19 ng L−1 and1555 ng L−1caffeine. These values were higher than those found in Eu-ropean rivers (80 ng L−1–250 ng L−1) and were in the range of influentconcentrations found in wastewater treatment plants (12 ng L−1–73,000 ng L−1) (Musolff et al., 2009; Buerge et al., 2003). In the ditch atsite 5, caffeinewas hardly detected over LOD. The natural potential to bio-degrade caffeine quite fast in aqueous environment (half-life 5–23 h,Bradley et al., 2007) caused its fast disappearance along the ditch section.

The non-steroidal analgesic and anti-inflammatory drugs ibuprofen,diclofenac, naproxen, and the neuroleptic drug carbamazepine enteredthe ditch via domestic sewage preferably at sites 2–4 (Fig. 3). Their oc-currence varied seasonally with maximum concentrations of the anal-gesics from April to June, the time with elevated infection rates in thisregion. Diclofenac, included in the “watch list” of emerging aquatic pol-lutants by the European Water Framework Directive (CID, 2015) wasdetected with maximum concentrations of 580 ng L−1. The analgesicsibuprofen and naproxen were found maximum at 4986 ng L−1 and2438 ng L−1, respectively (Table 1). Under high flow conditions in Sep-tember, these analgesics were transported from the input sources withloads of 31.1 mg h−1 (ibuprofen), 128.7 mg h−1 (naproxen) and16.2 mg h−1 (diclofenac) but they left the ditch sector at site 5 withonly 5.6 mg h−1, 29.7 mg h−1 and 8.1 mg h−1, respectively (TableS4). This decrease over rather short distancesmight result from dilutiondownstream and degradation considering the respective half-life timesbetween 1.4 h and 18 d for naproxen, ibuprofen, and diclofenac in lakewater (Lin and Reinhard, 2005; Araujo et al., 2014). Along the ditch,diclofenac decreased by 90% (from maximum mean concentration tothat at site 5) and ibuprofen by 98% which is comparable with the re-moval performance of constructed wetlands. Hijosa-Valsero et al.(2010) described a hybrid pond-wetland system treating urban waste-water that removed diclofenac by 65% and ibuprofen completely.

Due to their common mode of action concerning the blockage of in-flammatory and pain mediators in the organism, these analgesics mayaccount together for biological effects and potential environmental im-pact. Although investigations on the toxicity of these three drugs onalgae and daphnia indicate an increased toxicity when they are mixed(EC50=17mg L−1–156mg L−1) (Cleuvers, 2004), their concentrationssummed up in the ditch water did never reach these levels (Fig. 3).

Concentrations of the neuroleptic carbamazepine (CBZ) reached101 ng L−1 at sites 3 and 4 the major input sources with seasonalpeaks between June and August. During these hotmonths, the evapora-tion of ditch water increased and especially persistent substances likeCBZ were enriched. Due to its moderate adsorption affinity to sediment(Kd (sandy sediment) 0.21–5.32; Scheytt et al., 2005), CBZ can betransported over longer distances. At high flow rate in September, thetransport rate of CBZ at site 5 was estimated as 3.2 mg h−1. The levelof CBZ in the ditch water was in the range of river water (80 ng L−1–230 ng L−1, Reinstdorf et al., 2009).

Furthermore, other anthropogenic substances such as the polycyclicmusk fragrances, HHCB (CAS 1222-05-5), AHTN (CAS 1506-02-1), tech-nical nonylphenol and bisphenol A were found in the ditch water be-tween 5–217 ng L−1, 0.5–25 ng L−1, 15–300 ng L−1, and about5 ng L−1, respectively (Fig. S7).

3.2. Pollutants on sediments

Sediment sampleswere collected at the five sites inMarch, June, andSeptember in order to evaluate the sorption of the target substances.Preferably, lipophilic substances are expected to adsorb on sedimentsbut DDT and lambda-cyhalothrin were detected in the ditch sedimentsonly in March. Although classified as highly persistent in soil, DDT canbe reduced by volatilization and intensive sun light to about 50%within5 months especially in soils with low TOC (Jorgensen et al., 1991). Thepresence of DDE in the sediments at almost all sampling sites and

Fig. 2. Concentrations of acesulfame and caffeine in the ditch water over the monitoring period in 2013.

1112 M. Moeder et al. / Science of the Total Environment 598 (2017) 1106–1115

sampling dates pointed to a degradation of DDTwhichwas applied pre-viously. DDE decreased from 2.7mg kg−1 at site 1inMarch tominimum14 μg kg−1 in September (Fig. 4).

The lambda-cyhalothrin found in March (202–319 ng kg−1 d.w.)was dissipated till September. Due to its reported half-life in soil of57 days (Table S3), a comparable disappearance time was assumed forthe degradation in sediment.

Concentrations of the selected PAHs in sediment samples rangedfrom 174 to 2882 μg kg−1 d.w. and were slightly lower than concentra-tions (308–5020 μg kg−1 d.w) described for sewage sludge of wastewa-ter treatment plants, for instance in Spain (Sánchez-Brunete et al.,2007). Fig. 4 exhibits slightly decreasing concentrations of PAHs in sed-iments in direction to site 5. Acenaphthylene, phenanthrene, anthra-cene, fluoranthene and pyrene dominated the distribution pattern ofPAHs which was comparable to those reported for suspended solids re-lated from sewage sludge (Busetti et al., 2006). The more polar pollut-ants were detected only partially and mostly at low concentrations(Table S5). Calculated Koc values of the pollutants were in good agree-ment with literature data (Table S6).

Fig. 3. Presence of pharmaceutical residues in the ditch water, above: merged concentrationeuroleptic carbamazepine.

Correlations between water and sediment concentrations of the pol-lutants could not be observed. Only the amounts of caffeine and DDE,which occurred steadily in the ditch water, correlated with those in thesediments. Due to their good water solubility, the pesticides bentazone,dimethoate, and metalaxyl as well as the sweetener acesulfame or thepolar pharmaceuticals were scarcely adsorbed to sediment. For instance,in February, chlorpyrifos was detected at high concentrations in ditchwater at all sites but in sediments only marginally. The semi polar natureof chlorpyrifos (log Kow 4.7 and log Koc 3.9) implies certain affinity foradsorption on sediment surfaces but its half-life of 36 days in water/sediment systems (Table S3) seems to oppose its accumulation.

3.3. Plant uptake of pollutants

The ability of wetland plants like Phragmites australis to absorbveterinary drugs (Carvalho et al., 2012) and to mitigate pesticides hasbeen reported previously (Moore et al., 2008). The availability of sub-stances for plant uptake is predetermined by the chemical propertiesof the pollutants and the features of environmental compartments

ns of the analgesics naproxen, ibuprofen and diclofenac; below: concentrations of the

Fig. 5. Above: amounts of pharmaceutical compounds and caffeine and (below) ofselected pesticides estimated for roots plus above ground parts of T. domingensisharvested at sites 1–5 in March (III), June (VI) and September (IX) 2013.

1113M. Moeder et al. / Science of the Total Environment 598 (2017) 1106–1115

(Trapp, 2004; Hwang et al., 2017). Among the removal of pollutants byabsorption from the water/sediment system, particularly the rhizo-sphere of plants contributes beneficially to biodegradation of organicpollutants (Sauvêtre and Schröder, 2015). In the rhizosphere, oxygenand carbohydrates released by plant roots create microaerophilic andnutrient rich conditions supporting the growth of useful bacteriabeing able to degrade also anthropogenic substances such as carcino-genic azo-dyes in wastewater (Kumar et al., 2015).

For our study, T. domingensis plants were analyzed to investigate theuptake of the selected pollutants and their distribution in root, stem,and leaves (Table S7, Fig. 5).

For the fungicide metalaxyl, the concentrations detected in theplants of September ranged from 927 ng g−1 d.w. to 2194 ng g−1 d.w.At sites 1–3, the upper plant parts contained 2–3 times higher amountsof metalaxyl than roots. Among translocation to shoots, a foliar uptakeof metalaxyl could be possible due to contemporary spray application.Downstream at sites 4 and 5, the concentrations of metalaxyl in rootswere found similar or even higher than those in leaves implying an up-take mainly via roots from the ditch water. The water monitoring data,which showed highest metalaxyl concentrations in September, are ingood agreement with the plant uptake observations.

Thiacloprid, chlorpyrifos, and carbofuranewere detected in plants atlow concentrations (2–28 ng g−1 d.w.) and distributed almost equallyto roots and shoots (Table S7). Furthermore, all plants contained caf-feine (9–519 ng g−1 d.w.) and carbamazepine (4–69 ng g−1 d.w.)with increasing tendency from March to September (Fig. 5). CBZ in-creased in above ground plant parts by factor 3–8 and in the roots by10, which correlated with the enrichment of CBZ in water during sum-mer. Particularly neutral and recalcitrant compounds such as CBZ havebeen found readily incorporated in plants (Malchi et al., 2014).Wetlandexperiments revealed that T. domingensis can absorb up to 82% of CBZoccurring in wastewater. Its translocation into leaves and formation ofCBZmetabolites such as epoxycarbamazepinehas been described previ-ously (Dordio et al., 2011). Although pharmaceuticals such as ibuprofen,diclofenac and naproxen occurred seasonally dependent in the ditchwater (Fig. 3), a correlation with their plant uptake was not evident

Fig. 4. Above: concentrations of p,p′-DDT, -DDE and lambda-cyhalothrin and below thesum of PAHs in sediments at the different sampling sites and months.

(Fig. 5, Table S7). The uptake of substanceswith ionic functional groups,as these analgesics, is subjected to diverse influences such as pH condi-tions (Trapp, 2004). The pH of the ditch water varied between 7 and 8which was suboptimal for the uptake of the acidic drugs ibuprofen,diclofenac and naproxen with pKa values range between 4.2 and 4.8(ACD, 2014). In opposite, the beta-blocker propranolol (pKa 13.8) wasfound in plants although its concentration in water was quite low overthe year (Fig. 5, Table 1).

The content of PAHs in total plants varied from bLOD to about920 ng g−1 d.w. In most cases, the concentrations of PAHs in rootsexceeded those in the over ground parts suggesting both uptake viaroots from water and foliar uptake from air (Fig. 6). Translocation of thelipophilic PAHs from roots into shoots is less probable as their absorptionfrom contaminated sediment (Gao and Ling, 2006). The highest PAH con-centrations in ditchwaterwere detected at site 2 in June (820ng L−1) andin the plant roots at site 2 in September (175–839 ng g−1 d.w.). Fig. 6 ex-hibits that PAH concentrations particularly in roots increased fromMarchto September while their amounts in the upper plant parts remained al-most unchanged over the year (Fig. 6). Thus, the PAH concentrations inplant roots seem to reflect the water pollution with a certain delay. In aformer study where ryegrass was exposed to phenanthrene and pyrene,a stable partition of both substances between water and roots wereestablished after about 100 h (Kang et al., 2010).

Prominent PAHs found in the ditch plants were in decreasing order:anthracene (mean 92 ng g−1 d.w.), fluoranthene (46 ng g−1 d.w.),pyrene (36 ng g−1 d.w.) and phenanthrene (20 ng g−1 d.w.). Althoughinwater phenanthrene often exceeded the concentration of anthracene,it is less present in the plants, probably due to different uptake rates andmetabolic transformation. Less water soluble PAHs such as chryseneand benz[a]anthracene were detected sporadically in plants at verylow concentration (1–3 ng g−1 d.w.) but never in filtered water.

The pattern of PAHs detected in the upper plant parts were compa-rable with those reported from grasses (Poa trivialis) growing close tobusy highways (Bryselbout et al., 2000). However in these cases, higher

Fig. 6.Distribution of PAHs in cattail plants growing in the ditchwater. Concentrations arevalues obtained from pooled and homogenized plant parts.

1114 M. Moeder et al. / Science of the Total Environment 598 (2017) 1106–1115

PAH concentrations (e.g., 598 ng g−1 d.w. naphthalene and 158 ng g−1

d.w. chrysene) were observed than in the ditch plants.Estimating the total amount of target pollutants in one plant then

between 100 ng ± 20 ng and 2194 ng ± 121 ng were incorporated.For 20 plants growing on average per meter on both bank sites alongthe ditch over 3.6 km, the upper plant parts contained between55.3 mg and 825.6 mg of overall organic pollutants studied. However,this amount of pollutants absorbed by plants is small compared to thetotal amount transported through the ditch. Nevertheless, plant growthwith transpiration and metabolism led to permanent slight removal ofpollutants from water. Maintaining the ditch vegetation like removalof dead plants and harvesting of plants can contribute to mitigation oforganic pollutants in the ditch particularly, when thewaste is not storedat or nearby the ditch. Otherwise, pollutants released during rottingwillreach the ditch again via runoff. With probability, the list of contami-nants absorbed by the plants is much larger than our selected set oftarget substances. That T. domingensis is able to accumulate both organicand inorganic pollutants (e.g., mercury and lead) has already been dem-onstrated for constructed wetland systems treating different kinds ofwastewater (Lominchar et al., 2015; Shehzadi et al., 2014).

4. Conclusions

The occurrence of the selected organic pollutants in the ditch waterwas dependent on the sampling site and followed seasonal trends. Sites2–4were identified asmain inputs of substances associatedwithdomesticsewagewhichwas discharged untreated and almost continuously into theditch. Among consumer behavior, climatic conditions controlled the sea-sonal variations of pharmaceutical residues and the sweetener acesulfameinwater. The input of pesticides occurredmainly via runoff at quite differ-ent points of time and sites,which caused temporarilyhigh concentrationsin the ditchwater. Nevertheless during thewhole year, thewater escapedthe ditch sectorwith attenuated amounts of pollutants. For instance,meanconcentrations of DDE were reduced by 35% from the site with highestconcentrations to site 5, 91% for acesulfame, 90% for naproxen, 96% for ibu-profen, 90% for diclofenac and 81% for PAHs. Accumulation of the selectedpollutants in ditch environment was found of little concern.

Since the processes in the vegetated ditchwere subjected to remark-able variations in water flow and pollutant input, mass balance or miti-gation rates could not be estimated.

The one-year monitoring indicated that the daily input of domesticsewage impacted the chemical quality of the ditch water clearly butthe risks for the ditch ecosystem have to be examined further. Selectedpesticideswere observed in ditchwater at concentrations that exceededtemporarily toxic effect levels but within one month, all concentrationssubsided below no-effect levels. Among dilution and fast transport,pollutant transformations were accounted as important processes

mitigating the load of pollutants. The cattail plants assimilated ten ofthe selected target pollutants and contributed slightly to the removalof pollutants from water/sediment system.

In sum, the capability to decline organic anthropogenic pollutants(pesticides, pharmaceuticals, sweetener) seems to be another valuableecological service of vegetated ditches besides their main functions todrain agricultural fields, retain particulate matter, and create new habi-tats for organisms. Despite, the clear decrease of pollutants observedalong theditch, additional treatment of the domestic sewage dischargedinto the ditch is recommended to reduce the risk of spreading organicpollutants and pathogenic germs particularly, when water is reusedfor crop irrigation or received by aquaculture farms.

Acknowledgments

This work was supported by the National Council for Science andTechnology, Mexico (CONACYT I010/214/2012), and the German Aca-demic Exchange Service (DAAD U455D813 KTR).

Furthermore, the authors are grateful to Dr. Elke Schulz of the Depart-ment of Soil Economy (UFZ, Halle/Saale) for the TOC measurements.

Appendix A. Supplementary data

Supplementary data to this article can be found online at http://dx.doi.org/10.1016/j.scitotenv.2017.04.149.

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