Dissertations / Theses on the topic 'Remedies of land pollution'

The investigation and remediation of land contaminated with metals (copper, nickel, lead and zinc) was investigated. Calcium, iron and manganesele vels within the soils studied were also investigated. Several soils were used to assessth e three-stageB CR sequential extraction procedure and recent recommended modifications to this procedure. In general the modifications to the procedure were found to increase levels of copper, lead and iron extracted by the reductant used in the procedure. The modified BCR sequential extraction procedure was then used to assess the success of remediation strategies. Column leaching experiments, with EDTA, were set up to simulate soil-flushing technologies. Soil was extracted using the BCR procedure both before and after treatment. The experiments highlighted the need to consider the soil characteristics when determining a remediation strategy. The technique was shown to be successful for the leaching of the more mobile forms of copper, lead and zinc from the soils studied. Phytoremediation and chelate assisted phytoremediation were also investigated using the BCR sequential extraction procedure. Taraxacum officianale (dandelion) was grown in soil contaminated with zinc. The experiment was designed to study the ability of the plant to accumulate metals and also to study the effect of the addition of the chelator EDTA and the effect of the addition of a fertiliser. These methods were shown to remove significant proportions of zinc, copper and lead from the soil studied, however the time frame for remediation based on such techniques may be considerably longer than that for conventional methods.

It is widely claimed that at least 80% of the plastic litter entering marine environments comes from land-based sources, yet there is little empirical evidence to support this. Most studies to date predict the flux of litter from land to sea using global models based on a handful of field studies conducted mostly in developed, Northern Hemisphere countries; others use proxies such as per capita waste generation and proportion of mismanaged waste to predict litter loads entering the sea. It thus remains unclear how accurate these predictions are, particularly for African countries where few field studies have been conducted. Due to its rapidly growing human population, Africa is expected to become a much more significant source of litter into the sea. It is therefore important to identify major land-based sources of litter from the continent so as to implement effective mitigation strategies aimed at stopping this leakage of waste plastics into the marine environment. In this thesis I investigate two possible land-based sources of plastic pollution in South Africa. In Chapter 2 I show that stormwater run-off from Cape Town, a large coastal city, is a significant land-based source of litter into Table Bay. By placing nets over three stormwater outlets, each draining a different land-use type in the city, I estimate that some 70-630 tonnes of plastic litter are released as part of urban runoff from Cape Town each year which is a similar order of magnitude as estimates based on run-off litter collected in the 1990s and stranded beach litter. Overall, 40- 78% of litter items by count and 52-64% by mass was plastic, of which most was single-use packaging. Compared to a similar survey of the same three stormwater outlets conducted in 1996, litter densities by count decreased by 50% in two of the three catchments but increased threefold in the commercial/residential area. It is clear that urban run-off is a significant source of litter into Table Bay, but the total amount is considerably less than model predictions that identified South Africa as the 11th worst source of marine plastics from land-based sources globally. While several of South Africa's large cities are on the coast, the largest industrial centre and most densely populated part of the country is inland in the Gauteng Province. Much of this province lies within the catchment of the Orange-Vaal River system, which flows west across the country to eventually drain into the Atlantic Ocean. In Chapter 3 I present the results of two extensive field surveys to assess the amounts of plastic debris transported by the Orange-Vaal River system into the sea. By sampling for micro- and macro-plastics at 33 bridges spanning the lengths of both the Orange and Vaal rivers I show that densities of larger plastic items were highest at sites in the densely populated and highly urbanised upper reaches of the Vaal River, while microfibres were particularly abundant in the arid, sparsely populated lower reaches of the Orange River at the end of the wet season. It therefore appears that the Orange-Vaal River system may be a source of microfibres to the Atlantic Ocean, but most larger plastic items are retained near point sources in the upper reaches of the Vaal River. The Orange-Vaal River system thus does not appear to be a major source of plastics into the Atlantic Ocean and there is considerably less than the 0.095 tonnes·yr-1 predicted to be washed out of the Orange River by global models. I also investigated whether dams retain microplastics and microfibres within their reservoirs by collecting bulk water and neuston net samples from above and below the walls of the five major dams in the Orange-Vaal River system. I present these results in Chapter 4 and show that microplastic and microfibre concentrations were highest in dams on the densely populated Vaal River during dry conditions, whereas the opposite pattern occurred at dams farther downstream or on the sparsely populated Orange River during wet conditions. Overall, microplastic and microfibre densities were similar at sites collected above versus below dam walls and there was no significant correlation between microplastic and microfibre densities at a site and the distance from the site to the dam wall. Dams therefore do not appear to trap floating microplastics and microfibres, although the data were noisy (average CV = 184%) and so provide only a rough estimate of differences in plastic densities among sites. Lastly, in Chapter 5 I summarise the main results from the previous chapters and present recommendations for future research. Combining the findings from Chapters 2 and 3 I make a first, very crude estimate of the amount of plastic entering the sea from land-based sources in South Africa and compare this to the 0.09-0.25 million tonnes predicted by Jambeck et al. (2015) based on national estimates of waste production and management. I conclude that actual plastic emissions are some 1-2 orders of magnitude less than the global model estimate, which concurs with estimates based on beach litter data.

<p><span lang="EN-GB" style="font-size: 12.0pt<br>line-height:150%<br>font-family:&quot<br>Times New Roman&quot<br>,&quot<br>serif&quot<br>">The most significant human impacts on the hydrological system are due to land-use change. The conversion of land to agricultural, mining, industrial, or residential uses significantly alters the hydrological characteristics of the land surface and modifies pathways and rates of water flow. If this occurs over large or critical areas of a catchment, it can have significant short and long-term impacts, on the quality of water. While there are methods available to quantify the pollutants in surface water, methods of linking non-point source pollution to water quality at catchment scale are lacking. Therefore, the research presented in this thesis investigated modelling techniques to estimate the effect of land-cover type on water quality. The main goal of the study was to contribute towards improving the understanding of how different land-covers in an urbanizing catchment affect surface water quality. The aim of the research presented in this thesis was to explain how the quality of surface runoff varies on different land-cover types and to provide guidelines for minimizing water pollution that may be occurring in the Kuils-Eerste River catchment. The research objectives were<br>(1) to establish types and spatial distribution of land-cover types within the Kuils-Eerste River catchment, (2) to establish water quality characteristics of surface runoff from specific land-cover types at the experimental plot level, (3) to establish the contribution of each land-cover type to pollutant loads at the catchment scale.<span style="mso-spacerun:yes"> </span><span lang="EN-GB" style="font-size: 12.0pt<br>line-height:150%<br>font-family:&quot<br>Times New Roman&quot<br>,&quot<br>serif&quot<br>">Land-cover characteristics and water quality were investigated using GIS and Remote Sensing tools. The application of these tools resulted in the development of a land-cover map with 36 land classifications covering the whole catchment. Land-cover in the catchment is predominantly agricultural with vineyards and grassland covering the northern section of the catchment. Vineyards occupy over 35% of the total area followed by fynbos (indigenous vegetation) (12.5 %), open hard rock area (5.8 %), riparian forest (5.2 %), mountain forest<span style="mso-spacerun:yes">&nbsp<br>&nbsp<br></span>(5 %), dense scrub (4.4 %), and improved grassland (3.6 %). The residential area covers about 14 %. Roads cover 3.4 % of the total area. </span><span lang="EN-GB" style="font-size: 12.0pt<br>line-height:150%<br>font-family:&quot<br>Times New Roman&quot<br>,&quot<br>serif&quot<br>">Surface runoff is responsible for the transportation of large quantities of pollutants that affect the quality of water in the Kuils-Eerste River catchment. The different land-cover types and the distribution and concentration levels of the pollutants are not uniform. Experimental work was conducted at plot scale to understand whether land-cover types differed in their contributions to the concentration of water quality attributes emerging from them.<span style="color:black"> Four plots each with a length of 10 m to 12 m and 5 m width were set up. Plot I was set up on open grassland, Plot II represented the vineyards, Plot III covered the mountain forests, and Plot IV represented the fynbos land-cover.</span> Soil samples analyzed from the experimental plots fell in the category of sandy soil (Sa) with the top layer of Plot IV (fynbos) having loamy sand (LmSa). The soil particle sizes range between fine sand (59.1 % and 78.9 %) to coarse sand (between 7 % and 22 %). The content of clay and silt was between 0.2 % and 2.4 %. Medium sand was between 10.7 % and 17.6 %. In terms of vertical distribution of the particle sizes, a general decrease with respect to the size of particles was noted from the top layer (15 cm) to the bottom layer (30 cm) for all categories of the particle sizes. There was variation in particle size with depth and location within the experimental plots.</span><span lang="EN-GB" style="font-size: 12.0pt<br>line-height:150%<br>font-family:&quot<br>Times New Roman&quot<br>,&quot<br>serif&quot<br>">Two primary methods of collecting water samples were used<br>grab sampling and composite sampling. The quality of water as represented by the samples collected during storm events during the rainfall season of 2006 and 2007 was<span style="mso-spacerun:yes">&nbsp<br></span>used to establish <span style="mso-spacerun:yes">&nbsp<br></span>water quality characteristics for the different land-cover types. The concentration of total average suspended solids was highest in the following land-cover types, cemeteries (5.06 mg L^-1), arterial roads/main roads (3.94 mg L^-1), low density residential informal squatter camps (3.21 mg L^-1) and medium density residential informal townships (3.21 mg L^-1). Chloride concentrations were high on the following land-cover types, recreation grass/ golf course (2.61 mg L^-1), open area/barren land (1.59 mg L^-1), and improved grassland/vegetation crop (1.57 mg L^-1). The event mean concentration (EMC) values for NO₃-N were high on commercial mercantile (6 mg L^-1) and water channel (5 mg L^-1). The total phosphorus concentration mean values recorded high values on improved grassland/vegetation crop (3.78 mg L^-1), medium density residential informal townships (3mgL^-1) and low density residential informal squatter camps (3 mg L^-1). Surface runoff may also contribute soil particles into rivers during rainfall events, particularly from areas of disturbed soil, for example areas where market gardening is taking place. The study found that different land cover types contributed differently to nonpoint source pollution. </span><span lang="EN-GB" style="font-size: 12.0pt<br>line-height:150%<br>font-family:&quot<br>Times New Roman&quot<br>,&quot<br>serif&quot<br>">A GIS model was used to estimate the diffuse pollution of five pollutants (chloride, phosphorus, TSS, nitrogen and NO₃-N) in response to land cover variation using water quality data. The GIS model linked land cover information to diffuse nutrient signatures in response to surface runoff using the Curve Number method and EMC data were developed. Two models (RINSPE and N-SPECT) were used to estimate nonpoint source pollution using various GIS databases. The outputs from the GIS-based model were compared with recommended water quality standards. It was found that the RINSPE model gave accurate results in cases where NPS pollution dominate the total pollutant inputs over a given land cover type. However, the N-SPECT model simulations were too uncertain in cases where there were large numbers of land cover types with diverse NPS pollution load. All land-cover types with concentration values above the recommended national water quality standard were considered as areas that needed measures to mitigate the adverse effects of nonpoint pollution. </span><span lang="EN-GB" style="font-size: 12.0pt<br>line-height:150%<br>font-family:&quot<br>Times New Roman&quot<br>,&quot<br>serif&quot<br>">The expansion of urban areas and agricultural land has a direct effect on land cover types within the catchment. 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The chromatographic behaviour of four organophosphorus pesticides has been investigated, using capillary gas liquid chromatography-mass spectrometry (GC-MS), and packed and wide bore capillary gas liquid chromatography with electron capture detection (GC-ECD). The first part of this thesis (Chapter 3) embodies the application of high performance capillary gas liquid chromatography-mass spectrometry and the development of the methodology for analysis of pesticides in fruit and vegetable substrates. Manipulation of GC-MS data during the sample analysis is necessary in order to eliminate the problems arising from the complexity of the samples. The application of selected ion monitoring (SIM) in GC-MS is to a large extent limited by selection of the ion for monitoring, selection of internal standard, optimisation of electrometer zero, the electron multiplier voltage, the selected mass interval, column selection for GC-MS analysis and tuning of the quadrupole GC-MS. A major concern was with the determination of the optimum conditions for the analysis of substrates containing organophosphorus pesticides by GC-MS following solvent extraction (without clean up steps). The analysis of organophosphorus samples using GC-MS-SIM provides detection limits lower than Pg pesticide injected and very good recovery data. The second part (Chapter 4) deals with the application of GC-ECD. Here the role of packed column support, packed and wide bore capillary column temperature and detector temperature was investigated. Comparisons of the relative responses of the pesticides analysed (i) on packed columns and (ii) on wide bore capillary column under different column and detector cell temperatures were undertaken and the optimal condition for each of the organophosphorus pesticides was determined, under the optimal conditions the detection limits and recovery for fruit and vegetable samples were examined. The results from this method were correlated with the data obtained by GC-MS and found to be in very good agreement. The data obtained from analysis using GC-ECD was found to have a higher precision than that obtained by GC-MS, however GC-MS exhibited a higher selectivity for the determination of these pesticides.

The adsorption of sulphate has been studied using alpine and sub-alpine podzolic soils from the Allt a'Mharcaidh catchment, Cairngorms, Scotland, U.K. A detailed investigation of sulphur pools and mechanisms of sulphur retention has revealed that incoming sulphate ion, both marine and anthropogenic, is being retained by a range of adsorption mechanisms. Analysis of the soils has indicated that the sulphur content of the soils is dominated by organic forms of sulphur. Selective chemical fractionation techniques have identified an accumulation of sesquioxides, dominated by amorphous aluminium, in the basal horizons of all the soil profiles. Adsorption of sulphate has been shown to be mainly governed by the quantity and variable charge character of this sesquioxide phase. Fractionation has also suggested that the sesquioxides in the basal horizons of the soils are dominated by a combination of gibbsitic and imogolitic materials, the latter being present as a result of podzolization processes. The generation of sulphate adsorption isotherms has revealed that the organic horizons of the catchment soils show little or no sulphate adsorption capacity, due to a small sesquioxide content. In contrast, the mineral horizons are all capable of adsorbing sulphate, and in most cases this adsorption can be modelled to the Langmuir adsorption equation. The adsorption capacity of particle size fractions of the soils has revealed that even soil particles > 1 mm show an ability to retain sulphate, possibly by physical entrapment of soil solution in mineral pores or amorphous silica gel coatings. The accompanying hydroxyl release that is generally assumed to accompany adsorption of sulphate in the mineral soils was not evident, and unless a ligand exchange reaction was masked by other chemical reactions involving total proton balance, sulphate adsorption in the catchment soils is not due to a specific or 'low affinity' specific mechanism.

It was illustrated that Zn and Cu at or above 1000 and 800 mg kg^-1 respectively were highly toxic to the earthworm studied. Cu was found to be more toxic to the earthworm than Zn in respect to mortality, growth and reproduction parameters in all three different types of soils. The body burdens of earthworms exposed to metal amended soils increased corresponding to the increased concentrations of amended metals irrespective of soils used. It was found that the BCFs in earthworms decreased with the increased concentrations of metals in soils. The higher BCFs is the indication of uptake of higher proportion metals from soil by earthworms. The highest BCFs was found for Ni followed by Zn and Cu indicated their bioavailability to earthworms. The growth (weight) of the earthworms was most affected by Cu. The combined toxicity of Zn:Ni, Zn:Cu and Cu:Ni to reproduction (cocoon production) of earthworms was mainly antagonistic and to some extent additive in both the Insch and Boyndie soils. Zn was more toxic than Cu to the nematodes as the number of nematodes decreased with the increase of metal amendments to soil. It was also found that the number of nematodes increased at the exposure to some lower doses of Cu and Ni. The joint toxicity of Zn:Ni, Zn:Cu and Cu:Ni on the number of nematodes was mainly antagonistic in both the Insch and Boyndie soils. In some cases the combined toxicity of metals to nematodes was not possible to assess because the threshold level was not reached and also due to irregular and inconsistent data. Cruden Bay soil was more vulnerable than Insch and Boyndie soils in evaluating the toxicity of metals to nematodes. Zn was found to be toxic for the <i>lux</i>-marked bacterial biosensor <i>Escherichia coil</i> HB101 pUCD607 and <i>Pseudomonas fluorescens </i>10586r pUCD607 in different soils.