Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Agricultural environments are usually contaminated with mixtures of antropogenically
introduced chemicals as a result of pesticide spraying, which can affect beneficial, nontarget
soil invertebrates, such as earthworms negatively. Most studies on mixture toxicity
have focused on interactions of chemicals with similar structures and mechanisms.
However, chemical mixtures may occur as conglomerates of diverse structures and
toxicological mechanisms in the environment.
This study was aimed at assessing the effects of pesticides singly, and in a mixture, on
earthworms, using lifecycle parameters (growth and reproduction) and biomarkers
(neutral red retention (NRR) assay and acetylcholinesterase (AChE) inhibition) as
endpoints. Thus, to determine whether any interactions occurred between the pesticides
as shown by the measured endpoints. Another aim was to validate the use of the chosen
biomarkers for assessing mixture toxicity.
The pesticides used were from three groups: organophosphates, heavy metal-containing
pesticides and pyrethroids. From these three groups, four of the most commonly used
pesticides in the orchards and vineyards of the Western Cape, South Africa, were chosen,
namely chlorpyrifos (organophosphate), azinphos-methyl (organophosphate), copper
oxychloride (heavy metal-containing fungicide) and cypermethrin (pyrethroid).
Earthworms were exposed in the laboratory to a range of concentrations of chlorpyrifos
and copper oxychloride singly, and in 1:1 mixtures of these pesticides in artificial soil, for
four weeks. After the exposure period, the biomass change was determined as measure
of growth, and cocoon production, hatching success and number of hatchlings per cocoon
were determined as measures of reproduction.
Growth (biomass change) and reproduction (cocoon production) were affected by the
highest concentration treatment (20mg/kg) of chlorpyrifos, but copper oxychloride and
the mixture of the two pesticides showed no observable effects on lifecycle parameters.
Dose related effects on NRR times were however determined for both pesticides and the
mixture. Dose related effects on AChE activity were found for chlopyrifos and the
mixture of the two pesticides, but not for copper oxychloride. Short-term exposures (48
hours) of earthworms to the following pesticides in artificial groundwater: chlorpyrifos, copper oxychloride, azinphos-methyl, cypermethrin, chlorpyrifos-copper oxychloride,
chlorpyrifos -azinphos-methyl and chlorpyrifos-cypermethrin, were done followed by the
determination of AChE inhibition. Dose related effects were exhibited on the AChE
activity of earthworms exposed to chlorpyrifos, a mixture of chlorpyrifos and copper
oxychloride, azinphos-methyl, and a mixture of azinphos-methyl and chlorpyrifos.
Copper oxychloride, cypermethrin and the mixture of chlorpyrifos and cypermethrin had
no effect on AChE activity. Earthworms died at the highest exposure concentration of
the mixture of chlopyrifos and cypermethrin.
Results have shown that although the pesticides did not cause observable effects on
lifecycle parameters, there were effects at subcellular and biochemical level, as shown by
the biomarkers. Mixtures of pesticides, in some instances, affected earthworms
differently from their single components, indicating interactions between the pesticides in
mixtures, as shown by the measured endpoints. The NRR assay proved to be a good
general biomarker of soil contamination, and the AChE activity could also be a valuable
tool in assessing the effects of organophosphate mixtures and mixtures of
organophosphates and pesticides from other groups. / AFRIKAANSE OPSOMMING: Nie-teiken organismes, soos erdwurms, word negatief beïnvloed deur mengsels van
antropogeniese chemikalieë in landbou-omgewings. Die meeste studies wat handel oor
die toksisiteit van chemiese mengsels het tot dusver gefokus op chemikalieë van dieselfde
aard en met dieselfde meganismes van werking. Mengsels van chemiese stowwe kan
egter as konglomerate van 'n verskeidenheid strukturele eienskappe en met verskillende
toksiese meganismes in die omgewing aangetref word.
Tydens die studie is gepoog om die effekte van enkel pestisiede sowel as mengsels
daarvan op erdwurms te bestudeer, deur van lewensloop kenmerke (groei en
voortplanting) en biomerkers (neutraalrooi retensietyd - NNR en inhibisie van
asetielcholienesterase -AChE) as eindpunte gebruik te maak. 'n Verdere doel van die
studie was om vas te stel of daar enige wisselwerkings tussen die verskillende pestisiede
plaasvind, soos aangetoon deur die gemete eindpunte, en verder ook om die gebruik van
die gekose biomerkers as maatstawwe van mengseltoksisiteit te evalueer.
Die pestisiede wat gebruik is, is van drie verskillende groepe afkomstig: organofosfate,
swaarmetale en piretroiede. Van hierdie drie groepe is vier van die pestisiede wat vry
algemeen in boorde en wingerde in die Weskaap, Suid-Afrika, gebruik word,
geïdentifiseer. Hierdie stowwe is chlorpyrifos (organofosfaat), azinphos-metiel
(organofosfaat), koperoksichloried (swaarmetaalbevattende fungisied) en sipermetrien
(piretroied).
Erdwurms is in die laboratorium aan 'n reeks konsentrasies van chlorpyrifos en
koperoksichloried as enkel toksikante en as 1:1 mengsels in kunsmatige grond, vir vier
weke blootgestel. Voor en na die blootstellingsperiode is die biomassa van die wurms, as
maatstaf van groei, bepaal en kokonproduksie, uitbroeisukses en getal nakomelinge per
kokon bepaal as maatstawwe van voortplantingsvaardigheid. Groei
(biomassaverandering) en voortplanting (kokonproduksie) is beinvloed deur behandeling
met die hoogste konsentrasie (20 mg/kg) chlorpyrifos, terwyl geen effek van
koperoksichloried of die mengsel van hierdie twee pestisiede gevind is nie. Daar is gevind dat beide die pestisiede, enkel en in die mengsel, die NRR tye beinvloed het. Die
AChE aktiwiteit is beinvloed deur chlorpyrifos en die mengsel, maar nie deur die
koperoksichloried nie.
Korttermyn blootstellings van erdwurms (48 uur), in kunsmatige grondwater, van
erdwurms aan chlorpyrifos, koperoksichloried, azinphos-metiel en sipermetrien as enkel
toksikante en mengsels van chlorpyrifos-koperoksichloried, chlorpyrifos-azinphos-metiel
en chlorpyrifos-sipermetrien, is gedoen en gevolg deur die bepaling van AChE inhibisie.
Koperoksichloried, cypermetrien en die chlorpyrifos-sipermetrien mengsel het geen
waarneembare effek op die AChE aktiwiteit gehad nie ?????. Die erdwurms wat
blootgestel is aan die hoogste konsentrasie in die mengsel van chlorpyrifos-sipermetrien
het doodgegaan.
Die resultate het getoon dat die pestisiede nie in die korttermyn die lewensloopkenmerke
in enige waarneembare mate geaffekteer het nie maar daar was effekte op sellulêre en
biochemiese vlakke soos aangetoon deur die biomerkers. Sommige mengsels van die
pestisiede het die erdwurms verskillend van die enkelstowwe geaffekteer. Daar het dus
wisselwerking tussen sommige van die pestisiede wat in mengsels aangewend is,
plaasgevind, soos aangetoon deur die gemete eindpunte. Die NRR toets, as breë-spektrum
biomerker was 'n goeie maatstaf van kontaminasie in grond en daar is aanduidings dat
die AChE aktiwiteit, as 'n spesifieke biomerker, 'n nuttige maatstaf kan wees om die
effekte van organofosfaatmengsels en mengsels van hierdie chemiese groep en die van
ander chemikalieë aan te toon.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/16327 |
| Date | 12 1900 |
| Creators | Gola, Nontuthuzelo Pearl |
| Contributors | Reinecke, S.A., Reinecke, A.J., University of Stellenbosch. Faculty of Science. Dept. of Botany and Zoology. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xii, 93 leaves : ill. |
| Rights | University of Stellenbosch |
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