Evaluating sources and environmental risk of pesticide pollution in Western Cape rivers

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dc.contributor.advisorChow, Reynolden_ZA
dc.contributor.advisorStamm, Christianen_ZA
dc.contributor.authorDavies, Emma Janeen_ZA
dc.contributor.otherStellenbosch University. Faculty of Science. Dept. of Earth Sciences.en_ZA
dc.date.accessioned2023-11-24T13:54:06Z
dc.date.accessioned2024-01-08T18:28:30Z
dc.date.available2023-11-24T13:54:06Z
dc.date.available2024-01-08T18:28:30Z
dc.date.issued2023-12
dc.descriptionThesis (MSc)--Stellenbosch University, 2023. en_ZA
dc.description.abstractENGLISH ABSTRACT: Agriculture is key to South Africa’s economy which has led to the country becoming a leading pesticide user in Sub-Saharan Africa. The Western Cape is a dominant agricultural region in South Africa, making it particularly vulnerable to pesticide pollution. After application, pesticides can be transported away from the designated site, potentially causing adverse health effects to non-target organisms. Therefore, the risk of pesticide pollution must be better understood. This research deployed passive samplers in rivers for two-week intervals every month from February 2022 - March 2023 in the agricultural catchments Grabouw, Hex River Valley, and Piketberg. This expands on a previous campaign from 2017-2019. 44 pesticides were measured using Liquid Chromatography Mass Spectrometry. The original aspects of this study include the expansion of the sampling list to include the fungicide dimethomorph and a suite of drugs. 22 (out of 44) pesticides and seven (out of 20) drugs were detected above the limit of quantification. Piketberg had high drug concentrations and detection frequencies which correlated with pesticide concentrations, whereas Grabouw and Hex River Valley did not. This suggests that pesticide pollution in Piketberg is likely sourced from both wastewater treatment plants and agriculture, whereas the absence of drugs in Grabouw and Hex River Valley suggests that pesticide contamination is more likely sourced from agriculture. This is particularly true for terbuthylazine and carbendazim because their concentrations correlated with cumulative drug concentrations (R²=0.47 and 0.77, respectively). Five pesticides were detected in control samples deployed in Jonkershoek Nature Reserve. While detections could be from neighbouring agricultural catchments via atmospheric transport, they also indicate non-agricultural sources of herbicides (e.g., atrazine and terbuthylazine from trail maintenance or invasive plant control). A few compounds typically contributed to majority of the detected concentrations, specifically, imidacloprid (54%) and dimethomorph (22%) in Hex River Valley, imidacloprid (46%) and chlorantraniliprole (38%) in Grabouw and imidacloprid (22%) and terbuthylazine (27%) in Piketberg. The newly measured fungicide, dimethomorph, had high concentrations up to 80 ng/L and detection frequencies in Hex River Valley (96%) and Piketberg (25%). Pesticides with high detection frequencies were not applied year-round but have high Groundwater Ubiquity Scores (GUS), suggesting a high leaching potential into groundwater. Environmental risk was evaluated by comparing concentrations to European Environmental Quality Standards (EQS). Four compounds exceeded EQS values, namely the insecticides imidacloprid and chlorpyrifos, the herbicide terbuthylazine, and the fungicide spiroxamine. Exceedances for chlorpyrifos, spiroxamine, and terbuthylazine coincide with application events and rainfall. All compounds that exceeded in 2022/2023 (except for spiroxamine) also exceeded during the 2017-2019 campaign, indicating high persistence and continual exposure risk to aquatic life. Assessment of pesticide mixtures suggests that certain combinations (e.g., imidacloprid and chlorantraniliprole) can have increased toxicity effects on organisms, and almost occur year-round. Hydrological and concentration patterns suggest that increased detections are mainly driven by rainfall in winter, pesticide application in summer and constant input from wastewater treatment plants or groundwater transport. Future research should prioritize sampling of groundwater, wastewater influent and effluent and soils to improve our understanding of pesticide transport pathways.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Landbou is die sleutel tot die Suid-Afrikaanse ekonomie, wat daartoe gelei het dat die land een van die voorste plaagdoder-gebruikers in Sub-Sahara-Afrika geword het. Die Wes-Kaap is 'n dominante landbougebied in Suid-Afrika, wat dit besonders vatbaar maak vir plaagdoderbesoedeling. Na toediening kan plaagdoders van die aangewese terrein af vervoer word en moontlik nadelige gesondheidseffekte op nie-teikenorganismes veroorsaak. Daarom moet die risiko van plaagdoderbesoedeling beter verstaan word. Hierdie navorsing het passive monsternemers in riviere ingespan vir twee weke elke maand vanaf Februarie 2022 tot Maart 2023 in die landbou- opvangsgebiede Grabouw, Hex Rivier Vallei en Piketberg en bou voort op 'n vorige veldtog van 2017-2019. Vier-en-veertig plaagdoders is gemeet met vloeistofchromatografie massa-spektrometrie. Die oorspronklike aspekte van hierdie studie sluit die uitbreiding van die monsterlys in om die swamdoder dimetomorf en 'n reeks dwelms in te sluit. Twee-en-twintig plaagdoders en sewe dwelms is bo die kwantifiseringsgrens opgespoor. Piketberg het hoë dwelm-konsentrasies en deteksie- frekwensies gehad wat met plaagdoder-konsentrasies gekorreleer het, terwyl Grabouw en Hex Rivier Vallei nie dit gehad het nie. Dit stel voor dat plaagdoderbesoedeling in Piketberg waarskynlik afkomstig is van afvalwaterbehandelingsaanlegte asook landbou, terwyl die afwesigheid van dwelms in Grabouw en Hex Rivier Vallei voorstel dat plaagdoderbesoedeling meer waarskynlik afkomstig is van landbou. Dit is veral waar vir terbutilasiene en karbendasim omdat hul konsentrasies gekorreleer het met gekumuleerde dwelms-konsentrasies (R2=0.47 en 0.77, onderskeidelik). Vyf plaagdoders is opgetel in kontrolemonsters wat in die Jonkershoek Natuurreservaat ingespan is. Hoewel deteksies vanaf nabye landbou-opvanggebiede deur atmosferiese vervoer kon plaasvind, dui hulle ook nie- landboubronne van onkruiddoders aan (bv. atrasiene en terbutilasiene vanaf padonderhoud of die beheer van indringerplante). 'n Paar chemise verbindings het tot die meerderheid van die aangetrefte konsentrasies bygedra, spesifiek, imidakloprid (54%) en dimetomorf (22%) in Hex Rivier Vallei, imidakloprid (46%) en chlorentraniliprol (38%) in Grabouw en imidakloprid (22%) en terbutilasiene (27%) in Piketberg. Die swamdoder wat onlangs gemeet was, dimetomorf, het hoë konsentrasies, tot en met 80 ng/L, en deteksie-frekwensies in Hex River Valley (96%) en Piketberg (25%) gehad. Plaagdoders met hoë deteksie-frekwensies is nie regdeur die jaar teogepas nie, maar het hoë Grondwater Alomteenwoordigheidspunte, wat 'n hoë dreineringspotensiaal in grondwater voorstel. Die omgewingsrisiko is geëvalueer deur konsentrasies met Europese Omgewingsgehaltestandaarde (EQS) te vergelyk. Vier verbindings het EQS-waardes oorskry, naamlik die insekdoders Imidakloprid en chlorpirifos, die onkruiddoder terbutilasiene en die swamdoder spiroksamien. Die oorskrydings vir chlorpirifos, spiroksamien en terbutilasiene val saam met toedieninggebeure en reënval. Alle plaagdoders wat in 2022/2023 die EQS oorskry het (behalwe vir spiroksamien) het ook tydens die veldtog van 2017-2019 oorskry, wat op 'n hoë volharding en voortdurende blootstellingsrisiko vir waterlewe aandui. Die assessering van plaagdodermengsels dui daarop aan dat sekere kombinasies (bv. imidakloprid en chlorentraniliprol) verhoogde toksisiteitseffekte op organismes kan hê, en dit kom amper regdeur die jaar voor. Hidrologiese en konsentrasiepatrone dui daarop aan dat verhoogde deteksies hoofsaaklik deur reënval in die winter, plaagdodersgebruik in die somer en konstante invoer vanaf afvalwaterbehandelingsaanlegte of grondwatervervoer gedryf word. Toekomstige navorsing moet prioriteit gee aan monsterneming van grondwater, afvalwater in en-uitvloei sowel as die grond om ons begrip van plaagdodervervoerroetes te verbeter.af_ZA
dc.description.versionMastersen_ZA
dc.format.extentxviii, 223 pages : illustrations (some color), mapsen_ZA
dc.identifier.urihttps://scholar.sun.ac.za/handle/10019.1/128992
dc.language.isoen_ZAen_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshPesticides -- Environmental aspects -- South Africa -- Western Capeen_ZA
dc.subject.lcshGroundwater -- Pollution -- South Africa -- Western Capeen_ZA
dc.subject.lcshLiquid chromatographyen_ZA
dc.subject.lcshLiquid chromatography mass spectrometryen_ZA
dc.subject.lcshWater quality -- South Africa -- Western Capeen_ZA
dc.subject.lcshPesticides -- Risk assessmenten_ZA
dc.subject.lcshDrugsen_ZA
dc.subject.nameUCTDen_ZA
dc.titleEvaluating sources and environmental risk of pesticide pollution in Western Cape riversen_ZA
dc.typeThesisen_ZA
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