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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
381

Estudo comparativo das perdas d’água em mesocosmos colonizados ou não por aguapé (Eichhornia azurea (Swartz) kunth)

Caldas, Rudgen Rodrigues [UNESP] 13 August 2014 (has links) (PDF)
Made available in DSpace on 2015-01-26T13:21:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-08-13Bitstream added on 2015-01-26T13:30:21Z : No. of bitstreams: 1 000801582.pdf: 1564080 bytes, checksum: 80dff8c01963bc1b46c867fc07a4c3a8 (MD5) / Com a poluição hídrica a importância do estudo dos efeitos das populações de plantas aquáticas sobre os corpos aqüíferos vem ganhando notoriedade no campo das pesquisas. Quantidades excessivas desse tipo de vegetação têm trazido vários prejuízos aos ecossistemas aquáticos, entre eles, perdas de água ocasionadas pelas intensas taxas de transpiração dessas plantas. Esse trabalho teve como objetivo estimar a quantidade de água perdida por evapotranspiração de plantas aquáticas flutuantes, utilizando a espécie Eichhornia azurea (Swartz) kunth (aguapé), em reservatórios controlados. O experimento foi conduzido durante o mês de novembro do ano de 2011, em ambiente aberto, no Campus II da Faculdade de Engenharia de Ilha Solteira – UNESP, na cidade de Ilha Solteira/SP. Os tratamentos constaram de duas caixas d’água com volumes idênticos de água de 150 L, sendo que uma delas recebeu posteriormente uma população de E. azurea. Para obtenção dos dados de perda de água, foi utilizado um sensor capaz de medir a altura de coluna de água, com precisão milimétrica, variando de 0 a menos 2000 mm. Para a aquisição e leitura dos dados, foi acoplado aos sensores um sistema de coleta de dados em tempo real, ligados a um módulo de aquisição e registro de dados do tipo “datta logger”. Os dados utilizados no presente trabalho correspondem aos valores obtidos entre 00 horas (zero horas) do dia 02/11/2011 até às 10 horas do dia 12/11/2011, que depois de dispostos na forma de tabelas e figuras comparativas, possibilitaram verificar que a diferença de perda absoluta de água entre as caixas é de pelo menos 179% no tratamento com plantas, o que equivale a uma relação de evapotranspiração/evaporação (ET/E) de 2,79, influenciado pelas variáveis climáticas, em especial, a temperatura / With water pollution is important to study the effects of populations of aquatic plants on the bodies aquifers has gained notoriety in the field of research. Excessive amounts of this type of vegetation have brought many damages to aquatic ecosystems, including, water losses caused by intense transpiration rates of these plants. This study aimed to estimate the amount of water lost by evapotranspiration floating aquatic plant, Eichhornia azurea (Swartz) Kunth water hyacinth species in controlled reservoirs. The experiment was conducted during the month of November of the year 2011, in an open environment, Campus II of the Faculty of Engineering of Ilha Solteira - UNESP, in the city of Ilha Solteira/SP. The treatments consisted of two water tanks with identical volumes of 150 L of water, one of whom subsequently received a population of E. azurea. To obtain the data from loss of water, a sensor capable of measuring the height of water column, with pinpoint accuracy, ranging from 0 to about 2000 mm was used. For the acquisition and reading of data, was coupled to a system of sensors collecting data in real time, connected to a data acquisition and data logging type datta logger. The data used in this paper correspond to the values obtained between 00 hours (zero hour) of the day 02/11/2011 until 10am on 12/11/2011, that after arranged in the form of comparative tables and figures, check enabled the absolute difference between the loss of water boxes is at least 179% in treatment plants, equivalent to a ratio of evapotranspiration/evaporation (ET/E) 2.79 influenced by climate variables, in particular temperature
382

Influência das substâncias húmicas aquáticas na determinação de atrazina por imunoensaio (Elisa) /

Toscano, Ilda Antonieta Salata January 1999 (has links)
Orientador: Julio César Rocha / Resumo: Substâncias húmicas aquáticas (SHA) foram obtidas por processo de adsorção em resinas macroporosas não-iônicas, XAD 7 e XAD 2, dispostas em série. Após eluição com solução de NaOH, o extrato alcalino de SHA foi acidificado a pH 1,0 para separação em ácidos húmico (AH) que precipita, e ácido fúlvico (AF) o qual permanece em solução. Para caracterização físicoquímica do material húmico (AH e AF), foram feitas análise elementar, determinação do teor de substâncias húmicas e acidez total. Os resultados obtidos por UV-VIS e FTIR indicaram que AH apresenta maior número de grupos aromáticos em relação a AF, que em geral possui mais cadeias alifáticas. A aplicação da técnica imunoquímica, enzyme-linked immunosorbent assay (ELISA), para a determinação do herbicida atrazina em águas foi avaliada em amostra de água contendo alto teor de matéria orgânica (~35 mg L-1) e baixo valor de pH (3,8). O efeito matriz devido a presença de SHA pode ser notado pela perda de sensibilidade da técnica, ou seja, os valores de IC50 variaram de 60 ng L-1, na ausência de SHA, para 112 ng L-1 em concentrações acima de 10,0 mg L-1 de material húmico e para 137 ng L-1 em pH < 5,0. Além disto, pode-se inferir que a luz solar aumentou a velocidade de degradação da atrazina na presença de SHA formando produtos, com partes de suas estruturas, semelhantes ao produto original levando a resultados falso-positivos. A quantidade de material húmico presente na amostra de água foi a principal fonte de erro na análise de atrazina, levando à interações não-específicas entre as SHA e os reagentes enzimáticos. O procedimento ELISA, aplicado neste estudo, pode ser utilizado para determinação de atrazina desde que se faça diluição da amostra até cerca de 2,5 mg L-1 de húmicos e em pH alcalino (7,0 - 9,0). / Abstract: Aquatic humic substances (AHS) were isolated from water samples using Amberlite XAD 7 and XAD 2. After elution with NaOH solution, the XAD concentrated AHS was fractioned at pH 1.0 resulting in fulvic acid (FA - supernatant) and humic acid (HA - slurry). All humic materials were characterized with respect to elemental analysis, amount of AHS and total acidity. UV and FTIR spectra showed HA aromatic character greater than FA. Enzyme-linked immunosorbent assay (ELISA) was evaluated by analyzing atrazine in rich-humic matter water sample (~35 mg L-1) and acid water (pH 3.8). From all the conditions studied the low pH (pH < 5.0) and high humic substances concentrations (>10 mg L-1) showed the greatest influence. The IC50 values to control sample (no humic) decreased from 60 ng L-1 to 112 ng L-1 to humic solution at >10 mg L-1 and to 137 ng L-1 at pH < 5.0. The presence of AHS alters the photochemical behaviour of atrazine by accelerating its degradation forming metabolites which can be recognized by the antibodies. The assay performance showed a strong dependence on the pH values and amount of humic matter. However, analysis could be carried out directly in samples containing HA or FA that had been adjusted the pH in the range between 7.0 and 9.0, and humic concentration at 2.5 mg L-1. / Doutor
383

Influência da temperatura e de cargas de nutrientes no crescimento da macrófita aquática flutuante Eichhornia crassipes (Mart.) solms cultivada em água enriquecida artificialmente

Silva, Renata de Souza [UNESP] 06 March 2008 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:23:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-03-06Bitstream added on 2014-06-13T20:49:52Z : No. of bitstreams: 1 silva_rs_me_rcla.pdf: 294151 bytes, checksum: f57b8ae02f720b25cb596e933caccae1 (MD5) / Universidade Estadual Paulista (UNESP) / O objetivo deste trabalho foi avaliar o ganho de biomassa de Eichhornia crassipes cultivada em microcosmo em diferentes épocas do ano. O experimento teve duração de 189 dias e ocorreu entre abril e outubro de 2006. Indivíduos de E. crassipes foram cultivados em um sistema de recirculação de água composto por 3 unidades experimentais. O fluxo de água foi contínuo (vazão de 0,25 L min-1) e nutrientes foram adicionados semanalmente. Valores de nitrito, nitrato, ortofosfato, oxigênio dissolvido, condutividade elétrica, turbidez, pH e temperatura da água foram obtidos semanalmente. Os valores médios semanais de temperatura mínima absoluta atmosférica foram calculados através dos dados obtidos pela Estação Meteorológica CEAPLA/UNESP, localizado a aproximadamente 500 metros do local do experimento. Semanalmente as plantas foram pesadas e posteriormente devolvidas as respectivas unidades experimentais. Variações de temperatura atmosférica foram verificadas. O período com os menores valores de temperatura mínima atmosférica (junho e julho) coincidem com o período de menores valores de ganho de biomassa do vegetal. Após este período, os valores de temperatura aumentaram favorecendo o crescimento do vegetal, ocorrendo os maiores valores de ganho de biomassa.
384

Inter-relações entre zooplâncton e fitoplâncton mediante herbivoria na Lagoa do Camargo (zona de desembocadura do Rio Paranapanema na Represa de Jurumirim) /

Alves, Rachel Cristina Prehl. January 2011 (has links)
Orientador: Raoul Henry / Banca: Claudia Fileto / Banca: Danielli Cristina Granado Romero / Banca: Maria Stela Maioli Castilho Noll / Banca: Silvia Maria Caglierani / Resumo: Os organismos planctônicos são a base das cadeias alimentares no ecossistema aquático e os herbívoros zooplanctônicos, em particular, são importantes para o fluxo de energia nos ecossistemas aquáticos, sendo um elo entre os produtores primários e níveis tróficos mais elevados. Este estudo se propôs a ampliar o conhecimento da herbivoria do zooplâncton sobre o fitoplâncton em uma lagoa marginal ao rio Paranapanema. Foi realizado um experimento in situ, com instalação de enclosures com paredes de polietileno fechados no fundo que permitiram a realização de quatro tratamentos: 0% da densidade natural de zooplâncton (apenas fitoplâncton), 50 % (metade da densidade natural), 100% (densidade natural) e 150% (densidade acima da natural). A variação da densidade do zooplâncton foi conseguida por meio de filtração da água por rede de abertura de malha de 50μm. Água da lagoa também foi coletada. Todos os tratamentos foram realizados em tréplica. O experimento durou 18 dias. As coletas foram realizadas a cada seis dias (quatro coletas). A temperatura foi obtida em campo e água foi coletada para análise de oxigênio dissolvido, saturação, pH, condutividade elétrica, concentrações de fósforo total, nitrogênio total, material em suspensão total, material em suspensão orgânico, material em suspensão inorgânico, clorofila-a e feofitina-a. Foram coletadas também amostras de zooplâncton e fitoplâncton que foram contadas e identificadas, normalmente, até ao nível de espécie. Rotifera teve sua abundância relativa alterada em todos os tratamentos, com o favorecimento de Keratella cochlearis e Polyarthra vulgaris provavelmente porque o enclosure as protegeu de predadores. Cladocera foi dominado em todos os tratamentos por Bosmina freyi e B. hagmanni, bioindicadores de eutrofização... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The planktonic organisms are the basis of food chains in the aquatic ecosystems, and the grazer zooplankton, specifically, are very important to energy flow in the aquatic ecosystems, being a link between primary producers and higher trophic levels. The aim of this study is enhance the knowledge of zooplankton grazing over phytoplankton in a lateral lake by Paranapanema River, Brazil. The experiment was conducted in situ, with installation of enclosures of polyetilene walls, closed at the bottom, which allowed the manipulation of four treatments: 0% of the natural density of zooplankton (phytoplankton only); 50% (half of natural density); 100% (natural density) and 150% (a higher density than the natural). The zooplankton density range was obtained by water filtration in zooplankton web with 50μm mesh. The water of the lake was collected either. All the treatments were made using three replications each one. The experiment was carried out for 18 days. The samplings were made each six days (four samplings). The water temperature was measured at field, and a water sample was collected for dissolved oxygen, saturation, pH, conductivity, and concentrations of total phosphorus, total nitrogen, total suspended matter, organic suspended matter, inorganic suspended matter, chlorophyll-a and pheophytin-a analyses. Samples of zooplankton and phytoplankton were also taken. They were counted and identified until specie level, mostly. Rotifera had its relative abundance changed in all treatments, showing the increasing of Keratella cochlearis and Polyarthra vulgaris, probably because the enclosures protected them from predators. Cladocera dominated all treatments by Bosmina freyi and B hagmanni, which are bioindicators of water euthophication. The absolute abundance of this group was the one that best responded... (Complete abstract click electronic access below) / Doutor
385

Utilizacao do Zn-65 como elemento tracador no estudo da bioacumulacao do zinco por organismos aquaticos

MALAGRINO, WALDIR 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:37:00Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:28Z (GMT). No. of bitstreams: 1 04493.pdf: 2790902 bytes, checksum: ccbb6f01f8446ab22fe94eafa59c73a6 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
386

The application of triploid grass carp, as biological control agent for the over-abundant growth of aquatic weeds in irrigation canal systems

Du Plessis, Barend Jakobus 11 September 2008 (has links)
The overabundant proliferation of aquatic weeds in South African water conveyance systems cause a series of operational problems. Filamentous algae, such as Cladophora glomerata and pondweeds impede flow and reduce the capacity of irrigation canals to a significant extent. In worst case scenarios, irrigation scheme managers are faced with situations where they are unable to deliver water at the downstream ends of canal systems. This situation also contributes to water losses, crop losses and structural damage to concrete-lined canals. This dissertation is the product of a research project funded by the Water Research Commission to investigate the possible application of sterile (triploid) grass carp (Ctenopharyngodon idella) as biological control agent on aquatic weeds in concrete-lined irrigation canals. The aims of the project were firstly to investigate the suitability of a concrete-lined irrigation canal as grass carp habitat; secondly to test the efficacy of sterile grass carp as bio-control agent on filamentous algae; thirdly to evaluate the economic feasibility of this biological approach against the current chemical, physical and mechanical control methods; and fourthly to propose a management plan for the operational application of triploid grass carp as bio-control agent in irrigation canals. To achieve the goals set for the project, the Ramah-3 Canal near the town of Orania, was selected to serve as experimental canal. This canal can be regarded as a typical South African concrete-lined canal, and is located in the Orange-Riet River Canal System, downstream of the Vanderkloof Dam. As the majority of local irrigation canals are concrete-lined, skepticism existed amongst local scientists if the fish will be able survive in canals with a presumed high constant flow and low diversity of hydraulic biotopes. It was therefore a priority to establish the suitability of concrete-lined canals as habitat for this herbivorous fish specie. The study found that flow velocities in the Ramah Canal System never exceeded 1 m/s, even under high flow conditions (full capacity and 110% plus conditions) of more than 5 m3/s. It was found that grass carp thrived at flow rates ranging from 0.48 to 0.80 m/s, moving with ease upstream and downstream in a 16 km long experimental section of the Ramah-3 Canal. The sterile grass carp controlled the algal biomass in the Ramah Canal to significant levels. Cladophora was efficiently controlled at stocking rates of 3 to 7 fish per km canal. Triploid grass carp retrieved from the canal system after a six-month experimental period were found to be in an excellent physiological condition and displayed a mean weight increase of more than 300%. An ideal stocking protocol will probably be 10 individuals of 20 – 30 cm in length per kilometer canal, with a 10-15% annual supplementation figure. Civil structures, such as culverts, super-elevated canals and bridges will provide the fish with sufficient protection against possible predators. A few possible adaptations to the existing canal operation regimes should ensure that triploid grass carp could be managed as an effective biological control agent. This should be determined on a site-specific basis and could include additional civil structures such as sanctuary dams and small in-line fishways to ensure free migration throughout the target system. An attempt was made to conduct a brief economic analysis, based on information on expenditures of local irrigation schemes on aquatic weed control in their canals. The outcome of this brief investigation was in line with overseas findings in that biological control with sterile grass carp will be more economical than the currently applied control methods of herbicidal and mechanical or physical control. It can be concluded that the fish adapted to the artificial conditions experienced in a concrete-lined canal and perform their task as bio-control agent with ease. The author is of the opinion that this bio-control technique will contribute to the current Integrated Aquatic Weed Management Programmes (IAWMPs) of the Department of Water Affairs and Forestry. Site-specific conditions for each irrigation scheme will however, dictate a different approach to the aquatic weed problem. It is therefore strongly recommended that suitable qualified specialists should develop all aquatic weed management programmes on a site-specific basis. / Prof. G.J. Steyn
387

Changes in soil invertebrate decomposer communities during regeneration of Scots pine within the Abernethy Forest Reserve, Scotland

Horwood, Jane January 2001 (has links)
Plans currently exist to extend the range of native woodland within the Scottish Highlands. The effects of such an expansion on birds, mammals and above ground invertebrates have been previously been investigated, but little consideration has been given to soil invertebrates. This research looks at effects of Scots pine (Pinus sylvestris) regeneration on the meso- and macro- soil invertebrate communities. Within the Abernethy Forest Reserve (the largest remaining tract of native Scots pine woodland within the UK) mature woodland (pine-dominated) and moorland (Calluna vulgaris-dominated) sites were chosen on the three soil types present; an iron podzol, humus-iron podzol and peat. Three intermediate regeneration sites, upon two of the soil types, were also selected based on tree density and diameter at breast height (dbh). Together these sites formed two transects representing succession from moorland to mature woodland on the two soil types. At each site soil invertebrates were collected to a depth of 0.1 in and pitfall traps set. Litter bags were placed at the woodland and moorland sites to examine invertebrate succession during Pinus and Calluna litter decomposition. All invertebrates were identified to order and oribatid mites identified further using the morphospecies technique. The influences of soil type, depth, season and tree age on invertebrate communities were analysed using TWINSPAN and CANOCO. Results suggested that differences were present in invertebrate abundance and community structure between the two soil types, with more variation occurring along the peat transect than podzol transect. A number of oribatid morphospecies showed differences in density between transect sites and indicator species were present which separated the younger regenerating sites form older woodland. CANOCO analysis demonstrated that this was primarily due to changes in soil pH and temperature. In litter bags, Calluna showed significantly greater colonisation compared with Pinus at all sites and woodland litter bags supported a greater diversity of invertebrates than comparable moorland bags. Calluna litter is more complex than Pinus and may therefore provide a greater number of niches for invertebrates and shelter from prey. Differences between sites may be due to the presence of species adapted to utilising both litter types at the woodland end of the transect. In general concentrations of N and P significantly influenced the community composition within litter bags (pc0.05), but there were no significant relationships with other macronutrients. This work has shown that there are differences in the invertebrate community composition during the regeneration of Scots pine and decomposition of litter, however it is currently unclear whether these changes are truly successional.
388

Farm waste management : the effects of fine bubble aeration on cattle slurry and the fate of ammonia during the treatment process

Woodcock, David January 2003 (has links)
The aim of this investigation was to study the effect of fine bubble aeration on the relative amounts of N species, specifically NH 3 and NI-I4 within cattle slurry. Research into farm waste treatment systems has mainly concentrated on pig waste, yet cattle slurry treatment presents a challenging and relatively neglected research area. Farrell (1996) developed a fine bubble aeration treatment system and studied the effects of aeration on physical, chemical and fertiliser quality of slurry. He noted substantial loses of total Kjeldahl N from aerated slurry. This is a major concern as stripped NH3 can present a significant atmospheric pollutant. Here aeration treatment was studied at laboratory-scale (1 litre) and pilot-scale (100 litres). Air was externally supplied to tubular fine bubble diffusers. Initially a settleable floculative microbial culture was developed using batch-to-batch aeration that was continuously aerated for a maximum of 5 days. Treatment conditions were varied to study effects of aeration rate, temperature, pH and the addition of an adapted microbial culture upon N species within the slurry. The exhaust gases from the aeration bioreactors passed through a chemical capture system. Slurry samples were obtained during treatment to establish the chemical and biological changes. Finally, the effect of aeration on the fertiliser value of the treated slurry was studied. Experiments at laboratory-scale showed that N was released as NH 3 within the exhaust gases and that there were major changes in the amount and type of N species within the slurry. Increasing the pH of the slurry increased the quantity of NH3 released. Similar increases in rates of NH 3 release were shown for aeration rates up to 0.2 vvm and temperature up to 60 °C. The optimum conditions for NH3 stripping were found to be alkaline pH, high aeration rate and high temperature. At low aeration rates and low temperatures, there was a 96.59 % conservation of NH3 . The addition of an adapted microbial culture minimises the loss of N from the system, through the conversion of volatile N into organic microbial N fraction. In conserving N it was found that problems with sedimentation occurred. To improve rates of pollutant reduction it was necessary to increase temperature and aeration rates. Increasing temperature from 50 °C to 60 °C was found to have a negligible additional effect upon the biological degradation of the organic material within the slurry. This treatment strategy requires a capture system to trap the released NH3 . The aerobic treatment of cattle slurry was not found to have a significant effect upon the growth of maize in comparison to that of unaerated cattle slurry. Recommendations are made for operating conditions of an aerobic treatment system that will enable N to be either stripped from, or conserved within the slurry.
389

Studies on the excretion of pesticides in human milk as a means of investigating exposure and assessing the risk to infants in Indonesia

Barnes, Emma January 2004 (has links)
Humans bioaccumulate organochlorine pesticides throughout their lifetime due to the global environmental presence and physiochemical properties of these compounds, however, monitoring the current and lifetime exposure of the population to these compounds is complex. The collection and analysis of questionnaire data from Indonesia, human milk samples from Indonesian and UK born mothers living in Indonesia and milk samples during a 9-month lactation period as described in this thesis significantly contributes to the knowledge of human exposure to organochlorine pesticides and residue levels in human milk. Residue levels in milk samples from Indonesian mothers were positively correlated with the mother's age and parity, were higher in samples from urban than rural areas and did not show consistent correlations with diet. Correlations between pesticide levels and duration of lactation were not identified in a series of samples from the same mother or in samples from Indonesia. On a global scale residue levels from Indonesian samples were low, but p,p'-DDT was detectable in all samples and levels of y-HCH and p,p'-DDD were amongst the highest reported. The results from Indonesia including UK born women living in Indonesia coupled with existing data confirmed that the environment of Indonesia is contaminated with organochlorine pesticides and individuals had higher exposures in Indonesia than the UK. However, residue levels in milk samples from Indonesian women did not reflect the very high levels previously reported in local foods. An investigation into trends of organochiorine residue levels in human milk, foods and diets revealed that the consumption of animal fat significantly influenced human exposure and corresponding levels in human milk. Due to the extremely low consumption of animal fats by Indonesian people, the organochlorine levels detected in human milk did not reflect the environmental levels of these compounds. An exposure assessment model for residential Propoxur use in Indonesia was developed. It revealed that despite daily exposures, only low levels of Propoxur were likely to be absorbed and Propoxur exposure was unlikely to have toxicological effects. Despite more than 50 years of research, the detrimental effects of organochiorine pesticides in human milk have not been identified. The results indicated that 28% of Indonesian infants exceeded the acceptable daily intake (ADI) for Dieldrin, 90% exceeded the acute reference dose for total DDT and 24% for Endosulfan.
390

Monitoring and measuring the impacts and environmental implications of flood events on contaminated sediment dispersal in the River Swale catchment, North Yorkshire

Young, Elizabeth Anne January 2006 (has links)
The extraction, processing and smelting of ores has long been responsible for the release of heavy metals into the fluvial environment. As a consequence numerous studies have reported enhanced metal concentrations found in association with the sediments of rivers and in their surrounding floodplains. This thesis investigates the mobilisation, transport and the overbank deposition of sediment-associated heavy metals during flood events on the River Swale, North Yorkshire. This catchment has a prolonged history of mining for lead and zinc which spans approximately 2,000 years. Contemporary overbank sediment deposits for the fbll length of the river system were examined following three flood events that occurred in 2002. The quantity of sediment deposited and concentrations of associated metals were determined as well as the metal deposition flux and speciation, by using various analytical procedures including a nitric acid digestion and the BCR sequential extraction method. Physical characteristics such as sediment grain size, pH, loss on ignition and carbonate content were also investigated. Floodplain sedimentation rates were relatively high during the floods and the patterns in metal concentrations were both spatially and temporally consistent. The locations of most concern were located within the headwaters of the catchment where lead concentrations exceeded 25,000 mg kg'. Investigations into the mobility of the sediment-associated metals revealed that up to 88% of cadmium was found within the exchangeable phase of the sediment, however the concentrations of exchangeable lead and zinc were much higher and surpassed UK Government guidelines for crop growth and grazing livestock. Concentrations of exchangeable lead and zinc reached 19,241 mg kg' and 1,457 mg kg' respectively. Locations of 'exchangeable metal hotspots' with high levels of bioavailable metals were repeatedly found within the upper 21 km of the catchnent, around the confluence of tributaries which drain once intensively mined areas. These very high concentrations potentially pose a risk to flora and fauna that grow or graze on the floodplain surrounding the River Swale if they are taken up or ingested. Remediation measures could be adopted to treat either the source of metals in order to prevent them entering the fluvial system, reduce the concentrations already in the contaminated floodplain, or minimise the area inundated by flood waters. Alternatively, land management strategies could be adopted in order to reduce the potential for metal uptake by plants and animals and subsequently entering into the foodchain.

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