The occurrence of As in groundwater in Argentina was known since 1917; however, the occurrence, distribution and mobilization of As and other trace elements (TEs) in groundwater in the Bolivian Altiplano are still quite unknown. An investigation applying a geochemical approach was conducted in the Poopó Basin and Lake Titicaca to understand processes of TEs in different systems such as water, soils, crops and sediments in mining areas. In Poopó Basin,As, Cd and Mn concentrations exceed World Health Organization (WHO) guidelines and Bolivian regulations for drinking water in different places around the basin, but Cu, Ni, Pb and Zn do not. In soils, the sequential extraction methods extracted up to 12% (fractions 1 and 2), which represent &lt; 3.1 mg/kg of the total As content, as potentially mobilized fractions, that could be transferred to crops and/or dissolved in hydrologic system. The large pool of As can be attached due to amorphous and crystalline Fe oxide surfaces (fractions 3, 4, and 5) present in the soils. Furthermore, the concentrations of As, Cd and Pb in the edible part of the crops revealed that the concentrations of As and Cd do not exceed the international regulation (FAO, WHO, EC, Chilean) (0.50 mg/kgfw for As and 0.10 mg/kgfw for Cd), while Pb exceeds the international regulations for beans and potatoes (for beans 0.20 mg/kgfw and for potato 0.10 mg/kgfw). In the Lake Titicaca, principal component analysis (PCA) of TEs in sediments suggests that the Co-Ni-Cd association can be attributed to natural sources such as rock mineralization, while Cu-Fe-Mn come from effluents and mining activities, whereas Pb-Zn are mainly related to mining activities. The Risk Assessment Code (RAC) indicate “moderately to high risk” for mobilization of Cd, Co, Mn, Ni, Pb and Zn, while Cu and Fe indicate “low to moderate risk” for remobilization in the water column. / <p>QC 20140604</p> / Hydrochemistry: Arsenic and heavy metals in the Lake Poopó Basin (Sida contribution: 7500707606) / Catchment Management and Mining Impacts in Arid and semi-arid South America (CAMINAR) (INCO-CT-2006-032539)

This study gives insight to the origin of pollution in the water resources of the Limpopo province of South Africa. The Limpopo province is the largest rural province in South Africa. Up to 40% of the total population does not have access to sufficient water supply, resulting in adverse health effects. The purpose of this study is to determine (1) the degree of inorganic pollution of borehole water; (2) to identify the pollution sources, and (3) to determine whether the pollution is inherited from the surface water that recharges the groundwater or is caused on site near the bore holes. In order to achieve these objectives, surface water quality data (14 675 samples) and borehole water data (340 samples) at health facilities were analysed. A pollution index, defined by the following ratio: Pollution index (%) = 100 x ([Cl–] + 2[SO4^-2] + [NO3-] + 3[PO4^-3]) ÷ ([Cl-] + 2SO4^-2 + [NO3-] + [PO4^-3] + [HCO3-]) was used to determine the percentage of contribution of each chemical species towards pollution. This ratio is based on the fact that bicarbonate is released during chemical weathering of rocks whereas sulphate, nitrate, chloride, and phosphate are anthropogenic in origin. The pollution index shows that 6% of the surface waters and 21% of the borehole water is severely polluted. The pollution of the surface water is characterized by high concentrations of sulphate whereas the pollution of the borehole water is characterized by high concentrations of chloride. This indicates that the pollution of the borehole water is not so much the result of the infiltration of polluted surface water, but rather the result of on–site pollution on the surface near the bore holes. / Thesis (M.Sc. (Geography and Environmental Studies))--North-West University, Potchefstroom Campus, 2011.

This study gives insight to the origin of pollution in the water resources of the Limpopo province of South Africa. The Limpopo province is the largest rural province in South Africa. Up to 40% of the total population does not have access to sufficient water supply, resulting in adverse health effects. The purpose of this study is to determine (1) the degree of inorganic pollution of borehole water; (2) to identify the pollution sources, and (3) to determine whether the pollution is inherited from the surface water that recharges the groundwater or is caused on site near the bore holes. In order to achieve these objectives, surface water quality data (14 675 samples) and borehole water data (340 samples) at health facilities were analysed. A pollution index, defined by the following ratio: Pollution index (%) = 100 x ([Cl–] + 2[SO4^-2] + [NO3-] + 3[PO4^-3]) ÷ ([Cl-] + 2SO4^-2 + [NO3-] + [PO4^-3] + [HCO3-]) was used to determine the percentage of contribution of each chemical species towards pollution. This ratio is based on the fact that bicarbonate is released during chemical weathering of rocks whereas sulphate, nitrate, chloride, and phosphate are anthropogenic in origin. The pollution index shows that 6% of the surface waters and 21% of the borehole water is severely polluted. The pollution of the surface water is characterized by high concentrations of sulphate whereas the pollution of the borehole water is characterized by high concentrations of chloride. This indicates that the pollution of the borehole water is not so much the result of the infiltration of polluted surface water, but rather the result of on–site pollution on the surface near the bore holes. / Thesis (M.Sc. (Geography and Environmental Studies))--North-West University, Potchefstroom Campus, 2011.

Water quality is of great importance for ecosystems and society. This thesis characterized and modeled the variation in several key constituents of Swedish surface waters, with particular consideration given to intra-annual variability and sensitivity to climate change. Cyanobacterial data from 29 lakes and basins as well as total organic carbon (TOC) from 215 watercourses were used. Extensive data on catchment characteristics, morphometry, discharge, temperature and other water chemistry data were also analyzed. Models characterizing the seasonality in cyanobacterial concentration and relative cyanobacterial abundance were developed with common lake variables. Concentrations of TOC, iron and absorbance were simulated using discharge, seasonality and long-term trend terms in the Fluxmaster modeling system. Spatial patterns in these model terms were investigated, and the sensitivity of cyanobacteria and TOC to future climate was explored. Nutrients were the major control on cyanobacterial concentration seasonality, while temperature was more important for relative cyanobacterial abundance. No cyanobacterial blooms occurred below a total phosphorus threshold of 20 µg l-1. Discharge and seasonality explained much of the intra-annual variability in TOC, but catchment characteristics could only explain a limited amount of the spatial patterns in the sensitivity to these influences. North of Limes Norrlandicus the discharge term had a larger impact on the TOC concentration in large catchments than in small catchments, while south of Limes Norrlandicus the seasonality had a larger impact in small catchments than in larger catchments. According to the climate change scenarios, both TOC and cyanobacterial concentrations will be higher in the future. The cyanobacterial dominance will start earlier and persist longer. The spring TOC concentration peak will come earlier. The changes in TOC loads are more uncertain due to predicted declines in discharge. Parsimonious statistical regression models could explain observed variability in cyanobacteria and TOC. For predictions, these models assume that future aquatic ecosystems will exhibit the same sensitivity to major drivers as in the past. If this proves not to be the case, the modeling can serve as a sentinel for changing catchment function as indicated by degradation in model performance when calibrations on older data are used to model later observations.

Landfills are a major potential source of groundwater and surface-water contamination. The compounds that can leach from landfilled materials include dissolved organic matter, inorganic macrocomponents, heavy metals, and xebobiotic organic compounds. Landfill surface-water runoff poses a threat to the environment due to high mobility, but has not been rigorously characterized with regards to common pollutants found in landfills. It is well documented that constructed wetlands can serve as an effective treatment option for many pollutants found in landfills. The Napanee Landfill has constructed a wetland in order to treat surface-water runoff coming off the landfill. The objectives of this study were to: 1) characterize the water chemistry of surface-water runoff for an inactive landfill; 2) evaluate the treatment potential for the constructed wetland system at the Napanee Landfill; and, 3) recommend design, maintenance, and operative improvements to enhance effluent water quality. The analysis of the landfill surface-water runoff entering the Napanee Landfill constructed wetland included the pollutants nitrate, ammonia, sulphate, phosphorus, and chloride. The median inflow and outflow concentrations for all of the observed pollutants did not exceed Canadian federal or provincial water quality guidelines. There were sampling days where ammonia, phosphorus, and chloride exceeded guidelines at the inflow and days where ammonia and chloride exceeded guidelines at the outflow. The only pollutant that saw a statistically significant decrease in concentrations was sulphate, with a change of 38% from the inflow to the outflow. Other changes of note were nitrate and phosphorus concentrations increasing by 50% and 23% respectively from the inflow to the outflow. There are a variety of improvements that can be made to the Napanee Landfill constructed wetland that would increase the treatment efficiency of ammonia. Incorporating a vertical-flow wetland would increase available surface area for nitrifying bacteria growth and would provide more oxygen for nitrification processes; both would increase the potential for significant ammonia treatment. Overall, the concentrations of the pollutants found in the surface-water runoff coming off of the Napanee Landfill constructed wetland did not pose a significant threat to the environment at the time of sampling and treatment processes were only successful in reducing sulphate pollutant concentrations.

Hydration is known to be crucial in biomolecular interactions including ligand binding and self-assembly. In our earlier studies we have shown the key role of water in stabilizing the specific parts of the collagen triple helix depending on the imino acid content. We further showed that the primary hydration shell around collagen could act as a lubricating layer aiding in collagen assembly. But key details on the structure and dynamics of water near protein surfaces and its role in protein-protein interactions remain unclear. In the current study we have developed a novel method to analyze hydration maps around peptides at 1-A resolution around three self-assembling lament systems with known structures, that respectively have hydrated (collagen), dry non-polar and dry polar (amyloid) interfaces. Using computer simulations, we calculate local hydration maps and hydration forces. We find that the primary hydration shells are formed all over the surface, regardless of the types of the underlying amino acids. The weakly oscillating hydration force arises from coalescence and depletion of hydration shells as two laments approach, whereas local water diffusion, orientation, or hydrogen bonding events have no direct effect. Hydration forces between hydrated, polar, and non-polar interfaces differ in the amplitude and phase of the oscillation relative to the equilibrium surface separation. Therefore, water-mediated interactions between these protein surfaces ranging in character from ‘hydrophobic’ to ‘hydrophilic,’ have a common molecular origin based on the robustly formed hydration shells, which is likely applicable to a broad range of biomolecular assemblies whose interfacial geometry is similar in length scale to those of the present study. In a related study through simulations we show that the rate of tissue optical clearing by chemical agents correlated with the preferential formation of hydrogen bond bridges between agent and collagen. Hydrogen bond bridge formation disrupts the collagen hydration layer and facilitates replacement by a chemical agent to destabilize the tertiary structure of collagens thereby reducing light scattering. This study suggests that the clearing ability of an alcohol not only depends on its molecular size, but also on the position of hydroxyl groups on its backbone.

Both rice production and fish culture in the Mekong Delta, Vietnam have a close mutual relationship with the use of water and land resources. First, they are competitive in the use of land and water. Second, rice production discharges pesticides into water bodies causing an external cost to fish culture, which, in turn, leads to an increase in fish cost and price. A dynamic model for maximizing the social surplus is developed for optimal management of resources as well as production. Its first-order conditions provide some important quantitative as well as qualitative interpretation that explains the dynamic relationships among prices, water quality, and shadow price. The time paths and phase diagrams of the model show the variations and the changes in prices, outputs, and water quality over time, and the initial position in regions leading to divergence or convergence. As a result, effective policies are set up to maximize social welfare. Data are collected and used in estimations of demand functions of rice and fish, the function of assimilative capacity, the fish cost function, and the parameter of pesticide discharge. The total loss of fish culture (total external cost in the year 2001) due to pesticide use is about 9 billion $US. Two cases of linear and nonlinear forms are simulated with scenarios of initial values for the year 2001. The simulation shows optimistic results with prices going down and water quality going up over time, meaning the social surplus will rise. The phase diagram shows that the social manager should look for policies to raise the initial value of water quality to get an optimal solution. A comparative analysis of the model simulation shows the directions of change in parameters leading to a change in the steady state values. How to change the parameter values is analyzed and the analysis suggests different policies.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2005. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2006. / Härtill 4 uppsatser.

Thesis (MSc Food Sc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Surface water used for irrigation is often highly contaminated on a microbial level. Using contaminated surface water for the irrigation of fresh produce can lead to foodborne disease outbreaks and Escherichia coli has been a major cause of foodborne outbreaks associated with fresh produce over the past few years. There are many possible on-farm treatment options available to decrease the high microbial loads present in surface water, one of these is H2O2 and various factors can influence its use. The aim of this study was to determine the efficacy of H2O2 on different E. coli strains. Water from the Plankenburg River was sampled and treated with (250, 300 and 350 mg.L-1) H2O2 and the impact at 0, 30, 60, 90 and 120 min was then evaluated. It was found that the log reductions differed between samples. Log reductions ranged between 1.60 – 2.63 for Aerobic colony counts (ACC), total coliforms and Escherichia coli. The water was not considered safe for irrigation use although it had been treated with H2O2. Reference (ATCC) and environmental E. coli strains were individually treated with H2O2 (250, 300 and 350 mg.L-1) at 0, 30, 60, 90 and 120 min. Log reductions for the ATCC strains ranged between 2.13 – 5.48. This indicated a variation in H2O2 resistance between the different reference strains tested. Log reductions for the environmental E. coli strains ranged between 2.17 – 3.93. Escherichia coli M53 and MJ56 were the most resistant and most sensitive environmental strains to the H2O2 treatment, respectively. Once again it was observed that variations existed between the log reductions achieved for different strains. Overall, it was observed that the ATCC E. coli strains were more sensitive to the H2O2 treatments when compared the environmental strains. This indicates that ATCC strains should not be used for H2O2 treatment optimisation. Certain factors can influence the efficacy of H2O2 such as concentration and organic matter (chemical oxygen demand) present in the water. Different H2O2 concentrations were evaluated (50, 350, 700 and 1 000 mg.L-1) on two E. coli strains (M53 and W1371). Results indicated that 50 mg.L-1 was not effective as less than 1 log reduction was achieved after 120 min. When 350 and 700 mg.L-1 were used similar log reductions were achieved (1.78 – 2.27), which was not expected. Using 1 000 mg.L-1 was considered an effective concentration that resulted in no growth present after 120 min. Escherichia coli strain W1371 carried EPEC virulence factors (potential pathogen). This was included in the study in order to determine how a strain carrying virulence factors would react to H2O2. Escherichia coli W1371 was considered resistant to the H2O2 treatment and log reductions were similar to that achieved for M53. The catalase activity of the E. coli strains was studied to determine if a link existed between catalase activity and H2O2 resistance. Although a trend was observed between heat-stable catalase activity and H2O2 resistance, there were exceptions. It was concluded that high catalase activity does not always coincide with H2O2 resistance and that other mechanisms might also contribute to E. coli survival. Overall, it was observed that there are certain factors that influence the efficacy of H2O2 as a treatment option. It can be concluded that environmental E. coli strains are generally more resistant to the H2O2 treatment compared to ATCC E. coli strains, this needs to be considered when using H2O2 or other chemical disinfectants as a treatment option. / AFRIKAANSE OPSOMMING: Oppervlakwater wat gebruik word vir besproeiing is dikwels op ‘n mikrobiese vlak hoogs gekontamineer. Die gebruik van oppervlakwater vir die besproeiing van vars produkte kan tot die uitbraak van voedselgedraagde siektes lei. Escherichia coli was een van die hoofoorsake van voedselgedraagde uitbrake geassosieerd met vars produkte gedurende die laaste paar jaar. Daar is verskeie moontlike behandelingsmetodes op plaasvlak beskikbaar om die hoë mikrobiese las in oppervlakwater te verlaag. Een hiervan is waterstofperoksied (H2O2) en verskeie faktore kan die gebruik hiervan beïnvloed. Die doel van hierdie studie was om die doeltreffendheid van H2O2 op verskillende E. coli isolate te bepaal. Watermonsters uit die Plankenburg Rivier is behandel met drie konsentrasies H2O2 (250, 300 en 350 mg.L-1) en die impak is na 0, 30, 60, 90 en 120 minute geëvalueer. Daar is gevind dat die log reduksies tussen monsters verskil het. Log reduksies het gewissel tussen 1.60 en 2.63 vir aerobiese kolonietellings (AKT), totale kolivorme en E. coli. Selfs na H2O2 behandeling, is die water nie as veilig vir besproeiing beskou nie. Verwysingsisolate (ATCC) en omgewingsisolate van E. coli is afsonderlik met H2O2 behandel (250, 300 en 350 mg.L-1) vir 0, 30, 60, 90 en 120 minute. Log reduksies vir die ATCC isolate het gewissel tussen 2.13 en 5.48. Hierdie verskille dui op die variasies wat tussen die getoetste verwysingsisolate voorkom. Log reduksies vir die omgewingsisolate het gewissel tussen 2.17 en 3.93. Escherichia coli M53 en MJ56 was onderskeidelik die mees weerstandbiedende en mees sensitiewe verwysingsisolate wat getoets is. Verskille in log reduksies het daarop gedui dat isolaat variasies voorkom. In geheel is dit gevind dat die ATCC E. coli isolate meer sensitief was vir die H2O2 behandelings vergeleke met die omgewingsisolate. Dit toon dat die ATCC isolate nie gebruik moet word vir H2O2 behandeling optimering nie. Sekere faktore, soos die konsentrasie en organiese materiaal (chemiese suurstof vereiste) in die water, kan die doeltreffendheid van H2O2 behandeling beïnvloed. Verskillende H2O2 konsentrasies is geëvalueer (50, 350, 700 en 1000 mg.L-1) op twee E. coli isolate (M53 en W1371). Resultate dui daarop dat 50 mg.L-1 nie effektief was nie omdat minder as 1 log reduksie behaal is na 120 minute. Toe 350 en 700 mg.L-1 gebruik is, is soortgelyke log reduksies (1.78 – 2.27) teen verwagting in behaal. Die gebruik van 1000 mg.L-1 is as ‘n effektiewe behandeling beskou aangesien daar geen groei na 120 minute teenwoordig was nie. Escherichia coli isolaat W1371 besit EPEC virulensie faktore (potensiële patogeen). Dit is in die studie ingesluit ten einde te bepaal hoe ‘n isolaat met virulensie faktore sou reageer op H2O2. Escherichia coli W1371 is as weerstandbiedend teen die H2O2 behandeling beskou en log reduksies was soortgelyk aan die van M53 . Die katalase aktiwiteit van die E. coli isolate is bestudeer om te bepaal of ʼn skakel bestaan tussen katalase aktiwiteit en H2O2 weerstandbiedendheid. Alhoewel ‘n tendens waargeneem is tussen hitte-stabiele katalase aktiwiteit en H2O2 weerstandbiedendheid, was daar uitsonderings. Die gevolgtrekking was dat hoë katalase aktiwiteit nie altyd saamval met H2O2 weerstandbiedendheid nie en dat ander meganismes ook mag bydra tot E. coli oorlewing. In geheel is dit waargeneem dat daar sekere faktore is wat die doeltreffendheid van H2O2 as ‘n behandelingsmetode beïnvloed. Daar is gevind dat omgewingsisolate van E. coli in die algemeen meer weerstandbiedend is teenoor H2O2 behandeling in vergelyking met ATCC E. coli isolate. Dit moet in ag geneem word wanneer H2O2 of ander chemiese ontsmettingsmiddels oorweeg word as ʼn behandelingsopsie.