Kepone®, the registered trade name for decachlorooctahydro-1,3, 4-metheno-2H-cyclobuta cd pentalen-2-one, inhibited growth and reduced rates of photosynthesis and respiration of Chlorella sorokiniana Shihira and Kraus and Chlorocbccum hypnosporum Starr. The insecticide reduced rates of respiration more than photosynthesis. Uptake of ¹⁴C-Kepone by the algae was proportional to cellular concentration. A net efflux of Kepone was exhibited by Chlorella cells after 30 minutes of incubation, whereas, equilibrium occurred within 15 minutes of incubation for Chlorococcum. Desorption of Kepone was evident when both algal species were removed from Kepone treated solutions and incubated in untreated nutrient solutions. / Master of Science

A watershed scale water quality evaluation system was developed for assessing spatial variation of subsurface pesticide movement. The system consists of a linked-transport model component for performing simulation and a GIS component for processing spatially-related data. The surface heterogeneity caused by agricultural activities, topographic, hydrologic, and soil type variations in a watershed was handled by partitioning the watershed into homogeneous subfields. The subsurface soil profile and aquifer heterogeneities were considered by dividing the subsurface domain into root zone, intermediate vadose zone, and saturated zone, respectively. On each of the homogeneous subfields, the physically-based models, PRZM and VADOFT, were linked to simulate pesticide transport in the root and intermediated vadose zones. Pesticide movement in groundwater underneath the watershed was simulated by linking the other two models with SUTRA. An irregular shape finite element mesh generator was developed for fitting the irregular shape watershed boundary and reducing the number of nodes of the finite element mesh. Either transient or steady state flow and transport simulation could be performed with the system. The system is able quantitatively to produce detailed spatial variation maps of pesticide concentrations at any desired depth in the unsaturated zone and in groundwater. The system requires spatially-distributed information as inputs. Management of large volumes of spatially-referenced data which represent the heterogeneous properties of the watershed were facilitated by a developed GIS component. The GIS data processing component was composed of spatial data manipulation and display, attribute database management, and model input information extraction subcomponents. The spatial data processing component consists of data format conversion, map registering, map editing, new information generation, and map display subcomponents. / Ph. D.

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.

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

Large burrowing owl (Aihene cunicularia) populations exist in areas of intensive agriculture in California, and pesticide exposure has been identified as a potential threat to population persistence. I evaluated breeding season use of agricultural fields by adult male owls using radio telemetry, and examined egg contaminant residues to estimate population-level effects on reproduction and survival. Reproduction and survival were estimated annually, and an index of diet was inferred from pellet samples. A total of 11 adult males in 1998 and 22 in 1999 were successfully radio-tracked. Mean fixed kernel home range sizes were 172 ha (SE=68) in 1998 and 98 ha (SE=16) in 1999. Pellet analyses indicated a substantial increase in the numbers of rodents consumed in 1999, associated with an observed population explosion of California voles (Microtus calfornicus). Distance to the nest was the most important factor in differentiating between foraging and random locations, and there was no tendency to select or avoid any cover type. Owls did forage in agricultural fields, but I failed to find evidence of selection or avoidance of fields recently treated with pesticides. A total of 92 eggs were collected over 5 years. Egg contaminants were generally limited to the presence of p,p'DDE, which fluctuated by 4 orders of magnitude among years, from 0.05 ug/g to 33 ug/g fresh weight p,p'DDE. There was a general pattern of decline in egg residues over time for individual birds. The levels of p,p'DDE I documented did not appear to have any effect on either productivity or survival of adult females, nor were they clearly related to diet. I modeled the effects of various pesticide exposure impacts on demographic rates and determined that exposure rates based on field data would lead to relatively minor declines in population growth rate. An elasticity analysis of burrowing owl demographic parameters revealed a variable pattern, but generally indicated that factors influencing anyone of the demographic parameters of burrowing owls can have a substantial impact on population growth rate. / Graduation date: 2002

No description available.

Two different modeling approaches to simulate pesticide fate and transport in soil were investigated in this study. First, a process-based mathematical model, DRAINMOD-P, was developed by combining the attractive features of DRAINMOD and PESTFADE. While DRAINMOD formed the main component to perform hydrological predictions, PESTFADE's pesticide sub-model was used to simulate pesticide fate. The new model was validated against three years of independently collected field data from southern Ontario. Several statistical parameters were calculated to evaluate model performance. / Second, an implicit model, Multivariate Adaptive Regression Splines, MARS, which is also a novel data mining tool, was used to assess pesticide transport. MARS was first validated against the field data on three herbicides, namely, atrazine, metribuzin and metolachlor. DRAINMOD-P and MARS simulations, though impressive, need further validations before they can be recommended for actual real-world use.* / *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Microsoft Office; Adobe Acrobat.

A one-dimensional transient mathematical model which can predict simultaneous movement of water and reactive solutes through homogeneous soil systems under saturated/unsaturated conditions is developed. The physically-based numerical model, called PESTFADE, considers the interactive processes/mechanisms such as mass flow, plant uptake, adsorption/desorption, dispersion, volatilization, chemical/microbial degradation and runoff in the simulation. / The PESTFADE model employs SWACROP, a model developed in the Netherlands, to simulate transient water flow in the unsaturated zone; evaluates non-equilibrium sorption in macropores, analyzes soil heat flow to to model microbial degradation, calculates pesticide partitioning in runoff/sediment as affected by agricultural management practices, and describes first order degradation and sorption kinetics. The governing partial differential equation describing the various processes is solved numerically via the Numerical Method of Lines (NMOL) technique, and the computer programs are written in FORTRAN 77. The resulting computer code (PESTFADE), is run on a microcomputer and has been implemented for interactive simulation on IBM PC or compatible microcomputers. / The model was tested and validated using actual data measured from field plot experiments involving herbicide atrazine which was post-emergently applied in a corn field on a loam soil. Various analytical solutions were used to check the accuracy of the different components of PESTFADE, and parametric sensitivity analyses were performed to determine how the model output reacts to changes in some selected input parameters. / Results indicate that model predictions generally agreed with measured concentrations of atrazine and compared closely with the analytical solutions. Moreover, model performance tests showed that predicted values are within acceptable ranges of model accuracy and bound of experimental uncertainties. It was also found that the model is very sensitive to degradation rate constant (k), sorption coefficient (K$ sb{ rm d})$ and soil temperature and slightly sensitive to management practice (CN) and sorption site fraction (F). Finally, the various field scenarios and pathways for non-point source contamination evaluated in the study have demonstrated the wide applicability and flexibility of PESTFADE.

The work presented in this thesis represents a contribution to the area of modeling of the transport and fate of herbicides applied to cropped fields, and was part of a larger research effort geared towards better management of herbicides. The main objective of this thesis was to develop a graphical user interface (GUI) for PESTFADE, a process-based mathematical model of pesticide transport and degradation, and to provide documentation for the execution of PESTFADE. The model simulates changes in pesticide concentration at different depths in the soil, based on relevant physical, chemical, biological and meteorological factors. PESTFADE is considered to be one of the most comprehensive models of its kind. However, it was, until now, difficult to implement due to absence of a user manual and graphical interface suitable for exploitation in a Windows environment. The author developed the GUI in Visual Basic, created macros to facilitate certain calculations, rewrote the original FORTRAN 77 code and then validated the updated version against field data obtained from an experimental site (Eugene Whelan Farm, Woodslea, Ontario). A preliminary development of an artificial neural network (ANN) to perform the same simulation implicitly, with fewer input parameters and less computational time, was also done. / The thesis describes PESTFADE and the GUI, gives guidelines for implementing the package, and presents the results of the field validation of the revised version. During this work, the author discovered that there were problems in the parts of the code dealing with sorption phenomena. This can be solved by conventional kinetics or by Gamble kinetics.

[Truncated abstract] Pesticides are often transported to streams and/or groundwater as a result of the occurrence of rainfall events which trigger surface runoff or rapid preferential flow through the unsaturated zone. Much of the theory of solute transport has been derived assuming steady state or slowly varying upper boundary conditions and continuous, averaged process descriptions. However, a review of pesticide dynamics reveals that pesticides are episodically transported, predominantly through discrete flow pathways and this transport is often initiated as a near surface process, driven by naturally variable and intermittent rainfall intensities. The objective of the thesis is to better understand how the structure of natural variability of rainfall intensities impacts upon pesticide transport by these fast flow processes. We first conducted an analysis of a lysimeter leaching experiment that was aimed at identifying the rainfall controls on herbicide transport. Multivariate analyses revealed that average water balance behaviour at low temporal resolution controlled water and bromide transport while extreme rainfall events and rainfall event frequency controlled herbicide transport. A minimalist event based modelling approach was able to simulate the observed herbicide transport without or with only minor calibration. ... Finally we conduct a climate based regional risk assessment of pesticide leaching for the Wheatbelt region of the south-west of Western Australia. This is done for a suite of pesticides on a single soil to evaluate the impact of rainfall variability alone. Moderately sorbing, slowly degrading solutes have a greater regional potential for rapid leaching than both strongly and weakly sorbing solutes. High leaching potentials are found along the western and southern coast and in the far-east, with a band of low leaching potential through the central Wheatbelt. This is despite higher annual rainfall in the central areas compared to the east, and it is found that this occurs because of a change in the dominant fast flow triggers from frequent low intensity rainfall on the coasts to high intensity infrequent storms in the east. The coefficient of variation of annual leaching loads is similarly distributed. Spatial patterns of leaching potential depend upon chemical properties and application time. Peak loads of chemicals to fast flow pathways are found to converge to mid-winter, indicating periods of high loads of multiple pesticides may be an unavoidable consequence of the seasonality of storm properties.