Mdzeke, Naomi Patience (2004-03)
Thesis (PhD) -- Stellenbosch University, 2004.
ENGLISH ABSTRACT:Heavy metals are persistent environmental contaminants whose sources of inputs into the environment are both natural and anthropogenic. The levels of heavy metals (cadmium, copper, nickel, lead and zinc) in the False Bay intertidal zone were measured in the water, sediments and invertebrate species between August 2000 and August 2001. The results of the water and sediment analyses revealed that most pollution was associated with the northern shore of the bay between Strand and Muizenberg, where the most populated and industrial catchments occur. Significant spatial variations occurred, indicating the presence of localised contamination, while seasonal variations may be related to changes in precipitation and runoff at different times of the year. The concentrations of cadmium, nickel and lead were occasionally higher than the levels recommended by the South African Water Quality Standards. The possible sources of pollution at the different sites are also discussed. The concentrations of the five metals in the different invertebrate species (Oxystele tigrina, 0. sinensis, Choromytilus meridionalis, Patella oculus, Patiriella exigua and Tetraclita serrata) also revealed significant seasonal and spatial variations, with both the soft tissues and shells accumulating heavy metals. The barnacle T serrata from Rooiels had the highest cadmium concentration (70.67 J.lg/g dry weight), which may be related to historic pollution inputs from the military activities which took place at a weapons testing site at this site between 1987 and 1994, although no evidence was found to confirm this. The periwinkle 0. tigrina from Strand had the highest copper concentration (70.25 J.lg/g) while the limpet P. oculus from the same site had the highest nickel concentration (35.75 J.lg/g). The shells of the mussel C. meridionalis from Muizenberg had the highest concentration of lead (25.75 J.lg/g). Since cadmium occurs as a constituent of phosphate fertilisers used widely in the False Bay catchments, the effects of cadmium exposure on the different species were investigated during 14-day laboratory exposures to 200 and 400 J.lg/LCdCh. The results revealed a general pattern of tissue metal increase in the exposed organisms, followed by slight reductions after decontamination in clean seawater. The viscera and kidneys of C. meridionalis accumulated most of the dissolved cadmium. The shells of the mussels also accumulated cadmium, indicating the possible use of shells as a detoxification matrix.
AFRIKAANSE OPSOMMING:Swaarmetale is persisterende omgewingskontaminante waarvan die insetbronne beide natuurlik of van menslike oorsprong kan wees. Die kontaminasievlakke van swaarmetale (kadmium, koper, nikkel, lood en sink) in die Valsbaai tussengetysone is in die water, sedimente en invertebraatspesies bepaal vanaf Augustus 2000 tot Augustus 2001. Voorlopige resultate van die water- en sedimentontledings het getoon dat die meeste besoedeling by die noordelikke oewer van die baai voorgekom het tussen Strand and Muizenberg, waar die mees digbewoonde en ge-industrialiseerde opvangsgebiede is. Betekenisvolle ruimtelike en seisoenale variasie het in die konsentrasies van swaarmetale voorgekom, met die ruimtelike variasie wat moontlik gelokaliseerde kontaminasie aandui terwyl die seisoenale variasies weer verband mag hou met veranderings in die neerslag en afloop gedurende verskillende tye van die jaar. Die konsentrasie van kadmium, nikkel en lood was somtyds hoer as die vlakke wat deur die Suid-Afrikaanse Waterkwaliteitsstandaarde voorgestel word. Die moontlike bronne van besoedeling in die verskillende areas is ook in bespreking genoem. Die konsentrasies van die vyf swaametale in die verskillende invertebraatspesies (Oxystele tigrina, 0. sinensis, Choromytilus meridionalis, Patella oculus, Patiriella exigua and Tetraclita serrata) het ook seisoenale en ruimtelike variasies vertoon, die swaarmetale het in die sagte weefsel en skulpe van die invertebrate geakkumuleer. Die hoogste gemiddelde konsentrasie van kadmium (70.67 ).lg/g droe massa) is in die heel-liggaam monsters van die eendemossel T serrata gemeet wat by Rooiels versamel is. Die vlakke mag verband hou met die oprigting en aktiwiteite van die wapentoetsingsaanleg in die opvanggebied van die Rooiels lokaliteit tussen 1987 en 1994, maar geen bewyse daarvan is gevind nie. Die tolletjie, 0. tigrina wat in die 10kaliteit by Strand versamel is het die hoogste gemiddelde konsentrasie koper gehad 70.25 pig droe massa), terwyl die klipmossel P. oculus by dieselfde versamelpunt die hoogste konsentrasie nikkel (35.75 ).lg/gdroe massa) gehad het. Eksperimentele studies is ook uitgevoer op vier invertebraat spesies wat vir 14 dae in akwaria blootgestel is aan see-water met 200 en 400 p,g/L CdCh, en daama gedekontamineer is in skoon seewater.
Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/53733
Doctoral Degrees (Botany and Zoology)96