Spelling suggestions: "subject:"agricultural pollution -- south africa"" "subject:"agricultural pollution -- south affrica""
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Prediction and ecotoxicological effects of runoff induced pesticide contamination in agricultural surface waters : a risk assessment using GIS and microcosmsDabrowski, James Michael 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: Runoff is generally regarded as one of the most important routes of nonpoint source
pesticide pollution in agricultural surface waters. Of major concern is the fact that
low, sub-lethal levels of pesticide exposure are responsible for negative
ecotoxicological effects, stressing the need for methods capable of identifying
problem areas where populations could be at risk. Predicted average losses of three
pesticides in tributaries of nine sub-catchments of the Lourens River were calculated
through use of a GIS-based runoff model. There was a significant (p < 0.005) positive
correlation between the predicted average loss and mean measured concentrations of
the insecticides both in water and suspended sediments (R2 between 0.75 and 0.9),
indicating that the model could serve as a powerful tool for the risk assessment and
management of surface waters in South African orchard areas. Based on field relevant
exposure scenanos, the potential effects of azinphos-methyl on macroinvertebrate
communities were evaluated in a combined microcosm and field approach.
Microcosms were contaminated for 1 h with AZP (control, 0.2; 1,5and 20 ug/L;
three replicates each) and acute effects on survival were evaluated 6 days after
exposure. The sensitivity or tolerance of 12 core taxa was determined based on their
response to the exposure scenarios and compared to field tolerance/sensitivity as was
established by a field investigation at a control and contaminated site of the Lourens
River. The sensitivity/tolerance of ten of the 12 taxa corresponded to that which was
found in the field. Thus microcosm studies employing a field relevant design can be
successfully linked to field studies and indicate that transient pesticide contamination
affects the aquatic communities of the Lourens River. / AFRIKAANSE OPSOMMING
Afloop word oor die algemeen beskou as een van die belangrikste roetes van niepuntbron
pestisiedbesoedeling in landbou oppervlakwaters. Die feit dat lae, sub-letale
vlakke van pestisiedblootstelling negatiewe ektoksikologiese gevolge kan hê, is van
groot belang. Dit beklemtoon die behoefte aan metodes om probleemgebiede te kan
identifiseer waar bevolkings aan risiko onderhewig is. 'n GIS-gebaseerde
afloopmodel is gebruik om die gemidddelde verlies van drie pestisiede in die sytakke
van nege sub-opvangsgebiede van die Lourensrivier te voorspel. Daar was 'n
beduidende (p < 0.005) positiewe korrelasie tussen die voorspelde gemiddelde verlies
en gemete konsentrasies van insektisiede in beide die water en sediment (R2 between
0.75 and 0.9) fases, wat aandui dat die model as 'n kragtige hulpmiddel vir
risikobestuur van oppervlakwaters in Suid Afrikaanse boord-gebiede kan dien. Die
potensiële gevolge van azinfos-rnetiel (AZP) op makroinvertebraat gemeenskappe is
deur middel van 'n gekombineerde mikrokosmos (wat op veldrelevante blootstellings
gebaseer is) en veldbenadering bepaal. Mikrokosmosse is vir 1 h met AZP
gekontamineer (kontrole; 1; 0.2; 1; 5 en 20 ~g1L; drie replikate elk), en die akute
gevolge op oorlewing is ge-evalueer na ses dae van blootstelling. Die sensitiwiteit of
toleransie van 12 sleutel taksa is deur middel van hulle respons op die
blootstellingsreeks bepaal, en met hulle veldtoleransie/sensitiwiteit vergelyk wat in 'n
veldstudie by 'n kontrole- en gekontamineerde gebied in die Lourensrivier bepaal is.
Die sensitiwiteit/toleransie van 10 van die 12 taksa in die mikrokosmos eksperimente
het ooreengestem met die wat in die veld gevind is. Mikrokosmosstudies wat op 'n
veldrelevante ontwerp gebaseer is, kan dus suksesvol aan veldstudies gekoppel word,
en dui aan dat oorgedraagde pestisiedkontaminasie die akwatiese gemeenskap van die
Lourensrivier beinvloed.
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An assessment of the contribution of agricultural non-point source pollution on the water quality of the Vaal River within the Grootdraai Dam catchmentNcube, Scott 26 January 2015 (has links)
This study assesses the contribution of agricultural non-point source pollution, to poor water
quality of the Vaal River within the Grootdraai dam catchment area. The study evaluates
agricultural pollutants affecting the quality of water within the study area. The impact of
agricultural non-point source pollution on the water quality of the Vaal River was evaluated
by establishing a correlation between the quantity of polluted runoff reaching the River and
the quantity of measured nitrates and phosphates in its waters. A questionnaire using random
sampling was used to capture data from 15 commercial farmers 35 local residents and the
Department of Water Affairs management. The results of the study show that agricultural
nutrients are heavily impacting and compromising the water quality of the Grootdraai Dam.
The mean concentrations of Nitrogen and Phosphorus were found to be well above the water
quality guidelines there by promoting eutrophication. / Environmental Sciences / M. Sc. (Environmental Management)
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An assessment of the contribution of agricultural non-point source pollution on the water quality of the Vaal River within the Grootdraai Dam catchmentNcube, Scott 26 January 2015 (has links)
This study assesses the contribution of agricultural non-point source pollution, to poor water
quality of the Vaal River within the Grootdraai dam catchment area. The study evaluates
agricultural pollutants affecting the quality of water within the study area. The impact of
agricultural non-point source pollution on the water quality of the Vaal River was evaluated
by establishing a correlation between the quantity of polluted runoff reaching the River and
the quantity of measured nitrates and phosphates in its waters. A questionnaire using random
sampling was used to capture data from 15 commercial farmers 35 local residents and the
Department of Water Affairs management. The results of the study show that agricultural
nutrients are heavily impacting and compromising the water quality of the Grootdraai Dam.
The mean concentrations of Nitrogen and Phosphorus were found to be well above the water
quality guidelines there by promoting eutrophication. / Environmental Sciences / M. Sc. (Environmental Management)
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The role of salinity as an abiotic driver of ecological condition in a rural agricultural catchmentLerotholi, Sekhonyana January 2006 (has links)
The Kat River is an agricultural catchment that drains salt rich geology. Potential salinity impacts on ecological condition of the river were investigated. Monthly salt concentrations and flow discharges were monitored at ten sites along the Kat River below the Kat Dam. Monthly salt loads were computed to relate salinity to land use and ionic data used to assess the toxicity of major salts using the TIMS model. Concentration duration curves for sodium chloride were derived from flow concentration relationships, representing sodium chloride concentrations to which the aquatic ecosystem had been exposed. The ecological condition was assessed at nineteen sites using SASS5 biotic index over four seasons. Finally, the modelled instream salt concentrations and bioasessments were evaluated in terms of the modelled level of species protection afforded at different salt concentrations. Species Sensitivity Distributions (SSDs) were used for this exercise. There was a general downstream increase in salinity with the minimum concentrations recorded at the Fairbain tributary (84 mg/L) and maximum levels at the sewage outfall in Fort Beaufort (1222 mg/L). There was evidence that citrus irrigation upstream of Fort Beaufort increased salinisation. Sodium chloride, and to a lesser extent magnesium sulphate, were the dominant salts in the Kat River catchment, with the latter being more toxic. However these had little or no impact on the aquatic ecosystem. Flow-derived sodium chloride concentrations showed that both the Balfour and Blinkwater tributaries were in a fair/ poor condition. However with regard to ecological condition, it was demonstrated that the river is generally in a good state except for the Blinkwater River and the lower catchment. Degraded habitat condition at the Blinkwater was responsible for poor ecological condition. Integrating SSD derived classes, sodium chloride classes and ecological condition indicated that sodium chloride is a driver of ecological condition at the sewage treatment works and the subsequent site (only two of nineteen biomonitoring sites).
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