Contaminant bioavailability in soils, sediments, and aquatic environments

The aqueous concentrations of heavy metals in soils, sediments, and aquatic environments frequently are controlled by the dissolution and precipitation of discrete mineral phases. Contaminant uptake by organisms as well as contaminant transport in natural systems typically occurs through the solution phase. Thus, the thermodynamic solubility of contaminant-containing minerals in these environments can directly influence the chemical reactivity, transport, and ecotoxicity of their constituent ions. In many cases, Pb-contaminated soils and sediments contain the minerals anglesite (PbSO4), cerussite (PbCO3), and various lead oxides (e.g., litharge, PbO) as well as Pb2+ adsorbed to Fe and Mn (hydr)oxides. Whereas adsorbed Pb can be comparatively inert, the lead oxides, sulfates, and carbonates are all highly soluble in acidic to circumneutral environments, and soil Pb in these forms can pose a significant environmental risk. In contrast, the lead phosphates [e.g., pyromorphite, Pb5(PO4)3Cl] are much less soluble and geochemically stable over a wide pH range. Application of soluble or solid-phase phosphates (i.e., apatites) to contaminated soils and sediments induces the dissolution of the “native” Pb minerals, the desorption of Pb adsorbed by hydrous metal oxides, and the subsequent formation of pyromorphites in situ. This process results in decreases in the chemical lability and bioavailability of the Pb without its removal from the contaminated media. This and analogous approaches may be useful strategies for remediating contaminated soils and sediments.

Mercuric ion reduction and resistance in transgenic Arabidopsis thaliana plants expressing a modified bacterial merA gene.

With global heavy metal contamination increasing, plants that can process heavy metals might provide efficient and ecologically sound approaches to sequestration and removal. Mercuric ion reductase, MerA, converts toxic Hg2+ to the less toxic, relatively inert metallic mercury (Hg0) The bacterial merA sequence is rich in CpG dinucleotides and has a highly skewed codon usage, both of which are particularly unfavorable to efficient expression in plants. We constructed a mutagenized merA sequence, merApe9, modifying the flanking region and 9% of the coding region and placing this sequence under control of plant regulatory elements. Transgenic Arabidopsis thaliana seeds expressing merApe9 germinated, and these seedlings grew, flowered, and set seed on medium containing HgCl2 concentrations of 25-100 microM (5-20 ppm), levels toxic to several controls. Transgenic merApe9 seedlings evolved considerable amounts of Hg0 relative to control plants. The rate of mercury evolution and the level of resistance were proportional to the steady-state mRNA level, confirming that resistance was due to expression of the MerApe9 enzyme. Plants and bacteria expressing merApe9 were also resistant to toxic levels of Au3+. These and other data suggest that there are potentially viable molecular genetic approaches to the phytoremediation of metal ion pollution.

The octadecanoic pathway: signal molecules for the regulation of secondary pathways.

Plant defense against microbial pathogens and herbivores relies heavily on the induction of defense proteins and low molecular weight antibiotics. The signals between perception of the aggression, gene activation, and the subsequent biosynthesis of secondary compounds are assumed to be pentacylic oxylipin derivatives. The rapid, but transient, synthesis of cis-jasmonic acid was demonstrated after insect attack on a food plant and by microbial elicitor addition to plant suspension cultures. This effect is highly specific and not caused by a number of environmental stresses such as light, heavy metals, or cold or heat shock. Elicitation of Eschscholtzia cell cultures also led to a rapid alkalinization of the growth medium prior to jasmonate formation. Inhibition of this alkalinization process by the protein kinase inhibitor staurosporine also inhibited jasmonate formation. The induction of specific enzymes in the benzo[c]phenanthridine alkaloid pathway leading to the antimicrobial sanguinarine was induced to a qualitatively and quantitatively similar extent by fungal elicitor, methyl jasmonate, and its linolenic acid-derived precursor 12-oxophytodienoic acid. It is herein proposed that a second oxylipid cascade may exist in plants starting from linoleic acid via 15,16-dihydro-12-oxophytodienoic acid to 9,10-dihydrojasmonate. Experiments with synthetic trihomojasmonate demonstrated that beta-oxidation is not a prerequisite for biological activity and that 12-oxophytodienoic acid and derivatives are most likely fully active as signal transducers. Octadecanoic acid-derived compounds are essential elements in modulating the synthesis of antibiotic compounds and are thus integral to plant defense.

Aspectos técnicos e ambientais da incineração de resíduos sólidos urbanos: considerações sobre a proposta para São Paulo

A tecnologia de incineração no gerenciamento de resíduos sólidos urbanos é empregada de maneira intensa em diversos países do mundo. No Brasil, além da sua utilização eventual em resíduos de serviços de saúde, há uma proposta para implantação de duas usinas de grande porte visando ao tratamento térmico de resíduos sólidos domiciliares na cidade de São Paulo. Através de uma revisão bibliográfica sobre o tema, são apresentados os principais parâmetros técnicos e ambientais desta tecnologia, entre eles os mecanismos de combustão e de formação de poluentes, os tipos de equipamentos empregados, as formas de manejo e disposição de cinzas e escórias e os métodos de controle e redução de emissões atmosféricas como gases ácidos, material particulado e metais pesados. Também é feita uma revisão do atual conhecimento técnico-científico sobre dioxinas e furanos relativamente à incineração de resíduos sólidos urbanos. A partir desta base teórica pesquisada e da análise dos Estudos de Impacto Ambiental e dos Relatórios de Impacto Ambiental das usinas de incineração de Santo Amaro e Sapopemba, conclui-se que tais incineradores, na forma como são propostos, não apresentam o nível tecnológico necessário para atender às normas de operação e emissão de poluentes vigentes em países onde há legislação regulando esta atividade.

Estudo de equilíbrio e cinética da biossorção de cobre (II) por Rhizopus Microsporus.

A poluição relacionada a metais pesados tem recebido uma atenção especial devido a sua alta toxicidade, não biodegradabilidade e tendência de acumular-se na cadeia alimentar. Apesar disso, metais pesados também são considerados recursos valiosos, portanto a sua remoção em conjunto com a sua recuperação torna-se ainda mais importante. Este caso aplica-se aos rejeitos de mineração de cobre, os quais oferecem a possibilidade de recuperação do metal e de sua contenção de maneira segura do meio ambiente. Tais rejeitos se caracterizam por ocuparem enormes áreas inundadas e abrigarem soluções diluídas de cobre (II), porém, muitas vezes, acima dos limites seguros. Diversos processos tradicionais de tratamento mostram-se disponíveis para remover o cobre de tais soluções, no entanto, em certas aplicações eles podem ser ineficientes ou muito onerosos. Nesse contexto, a biossorção é uma alternativa interessante. Nesse processo, certos microrganismos, como fungos, bactérias e algas, ligam-se passivamente ao cobre na forma íons ou outras moléculas em soluções. No presente trabalho foi avaliado o potencial de biossorção de íons cobre (II) pela biomassa do fungo Rhizopus microsporus, coletado e isolado da área de rejeitos da Mina do Sossego, na região norte do Brasil. Isotermas de biossorção foram determinadas experimentalmente em bateladas sob temperatura de 25°C, agitação de 150 rpm, concentração de biomassa de 2,0 a 2,5 g/L e tempo de contato mínimo de 4 horas. O pH mostrou ser um fator importante no equilíbrio da biossorção, sendo o valor máximo da capacidade de biossorção de 33,12 mg de cobre / g biomassa encontrado em pH 6. Valores sucessivamente menores são encontrados pela acidificação da solução, sendo o pH 1 considerado adequado para o processo de dessorção, correspondendo a uma capacidade de biossorção de 1,95 mg/g. Modelos de adsorção de Langmuir e de Freundlich ajustaram-se adequadamente às isotermas tanto com pH controlado quanto não controlado. Foi constatado que a troca iônica é um dos mecanismos envolvidos na biossorção do cobre com Rhizopus microsporus. Tanto o modelo de pseudo-primeira ordem quanto o de pseudo-segunda ordem ajustaram-se aos dados cinéticos da biossorção, sendo que o equilíbrio ocorre em aproximadamente 4 horas. A biomassa conservou a capacidade de biossorção ao operar repetidamente em três ciclos de sorção-dessorção. A biomassa viável e a morta não apresentaram diferença estatisticamente significativa na capacidade de biossorção.

Intoxicación por munición de plomo en aves silvestres en España y medidas para reducir el riesgo

La intoxicación por ingestión de munición de plomo en aves silvestres es conocida en España desde finales del siglo pasado. Elevadas densidades de perdigones de plomo en diversos humedales de importancia internacional producen tasas de ingestión de perdigones cercanas al 70% en especies como el ánade rabudo (Anas acuta) y el plumbismo llega a ser una de las principales causas de mortalidad de la amenazada malvasía cabeciblanca (Oxyura leucocephala). El plumbismo también ha sido descrito en diversas especies de aves rapaces y se ha comprobado que la exposición al plomo es elevada en las especies más carroñeras y oportunistas. La contaminación de la carne de caza también ha sido objeto de estudio, debido a que en España se da la particularidad de cocinarla en escabeche, lo que incrementa la transferencia de plomo de la munición a la carne. Por el momento, la única acción llevada a cabo para reducir el riesgo de exposición al plomo de la munición en aves y humanos ha sido la prohibición desde 2001 del uso de perdigones de plomo en humedales protegidos. En esta revisión se hace un repaso a los estudios llevados a cabo en España sobre la contaminación por el plomo de la munición y el efecto que están teniendo las medidas hasta el momento adoptadas para reducir este riesgo.

Estudio de la concentración de elementos traza tóxicos de los depósitos de lodos, los suelos y las plantas en Mina La Solana, Almería (España)

En ese trabajo se estudia la concentración de elementos traza tóxicos en los depósitos de lodos (relaves) abandonados por la industria minera en Almería (España), los suelos del entorno próximo y las plantas que los colonizan y representan una vía de incorporación de dichos elementos en la cadena trófica. La industria minera antigua dejó toda una serie de instalaciones abandonadas en diferentes zonas de Andalucía, entre las que destacan por presentar altos contenidos en metales, los depósitos de residuos en forma de lodos generados en el proceso de flotación. En este estudio se trata el caso concreto de los depósitos de lodos de Mina La Solana (Almócita, Almería), donde se ha realizado una caracterización geoquímica de los depósitos y de los suelos de su entorno, en función al contenido en algunos elementos traza. Se han caracterizado muestras de las plantas que enraízan en dichos residuos para determinar la concentración que presentan en los mismos elementos traza. Los resultados muestran que los lodos presentan altos contenidos en Pb (concentración media 6800 ppm) y Zn (concentración media 22 000 ppm). Estos elementos no aparecen en forma soluble en agua, los test de lixiviación dan valores de concentración muy bajos (≤10 ppm de Pb y ≤ 2 ppm de Zn). De la misma forma se ha determinado una concentración alta de los mismos elementos en los restos vegetales, con un valor del Pb hasta los 210 ppm y 1300 ppm de Zn. Este hecho pone de manifiesto la capacidad de las plantas para alterar la movilidad de los elementos presentes en el sustrato donde enraízan estableciéndose una transferencia hacia la cadena trófica.

Conformational changes of dissolved humic and fulvic superstructures with progressive iron complexation

Conformational changes of a humic acid (HA) and a fulvic acid (FA) induced by iron complexation were followed by high-performance size exclusion chromatography (HPSEC) with both UV–vis and refractive index (RI) detectors. Molecular size distribution was reduced for HA and increased for FA with progressive iron complexation. Since interactions of Fe with humic components are electrostatic, it is likely that the triple-charged Fe ions formed stronger complexes with the more acidic hydrophilic and hydrated FA than with the less acidic and more hydrophobic HA. The large content of ionized carboxyl groups in FA, thus favored the formation of intra- or intermolecular bridges between the negatively charged fulvic acid molecules, and led to more compact and larger size network than for HA. Conversely, iron complexation with HA disrupted the humic conformational arrangements stabilized by only weak hydrophobic bonds into smaller-size aggregates of greater conformational stability due to formation of strong metal complexes. These results confirmed that humic molecules in solution were organized in supramolecular associations of relatively small molecules loosely bound together by dispersive interactions and hydrogen bonds, and they specifically responded to chemical changes brought about by metal additions. The present study revealed the molecular changes occurring in superstructures of natural organic matter when in metal complexes and contributed to understand and predict the environmental behavior in waters and soil of metal complexes with natural organic matter.

Electroadsorption of arsenic from natural water in granular activated carbon

The adsorption and electroadsorption of arsenic from a natural water has been studied in a filter-press electrochemical cell using a commercial granular activated carbon as adsorbent and Pt/Ti and graphite as electrodes. A significant reduction of the arsenic concentration is achieved when current is imposed between the electrodes, especially when the activated carbon was located in the vicinity of the anode. This enhancement can be explained in terms of the presence of electrostatic interactions between the polarized carbon surface and the arsenic ions, and changes in the distribution of most stable species of arsenic in solution due to As(III) to As(V) oxidation. In summary, electrochemical adsorption on a filter-press cell can be used for enhancement the arsenic remediation with activated carbon in the treatment of a real groundwater.

Brackish groundwater desalination by reverse osmosis in southeastern Spain. Presence of emerging contaminants and potential impacts on soil-aquifer media

Desalinated brackish groundwater is becoming a new source of water supply to comply with growing water demands, especially in (semi-) arid countries. Recent publications show that some chemical compounds may persist in an unaltered form after the desalination processes and that there is an associated risk of mixing waters with different salinity for irrigation. At the university of Alicante campus (Spain), a mix of desalinated brackish groundwater and water from the existing aquifer is currently applied for landscape irrigation. The presence of 209 emerging compounds, surfactants, priority substances according to the 2008/105/EC Directive, 11 heavy metals and microbiological organisms in blended water and aquifer samples was investigated. Thirty-five compounds were detected (pesticides, pharmaceuticals and surfactants) among them two priority substances α-endosulfan and Ni were found above the permitted maximum concentration. Blended water used for landscape irrigation during the summer period is supersaturated with respect to carbonates, which may ultimately lead to mineral precipitation in the soil-aquifer media and changes in hydraulic parameters.

Pencil it in: pencil drawn electrochemical sensing platforms

Inspired by recent reports concerning the utilisation of hand drawn pencil macroelectrodes (PDEs), we report the fabrication, characterisation (physicochemical and electrochemical) and implementation (electrochemical sensing) of various PDEs drawn upon a flexible polyester substrate. Electrochemical characterisation reveals that there are no quantifiable electrochemical responses upon utilising these PDEs with an electroactive analyte that requires an electrochemical oxidation step first, therefore the PDEs have been examined towards the electroactive redox probes hexaammineruthenium(III) chloride, potassium ferricyanide and ammonium iron(II) sulfate. For the first time, characterisation of the number of drawn pencil layers and the grade of pencil are examined; these parameters are commonly overlooked when utilising PDEs. It is demonstrated that a PDE drawn ten times with a 6B pencil presented the most advantageous electrochemical platform, in terms of electrochemical reversibility and peak height/analytical signal. In consideration of the aforementioned limitation, analytes requiring an electrochemical reduction as the first process were solely analysed. We demonstrate the beneficial electroanalytical capabilities of these PDEs towards p-benzoquinone and the simultaneous detection of heavy metals, namely lead(II) and cadmium(II), all of which are explored for the first time utilising PDEs. Initially, the detection limits of this system were higher than desired for electroanalytical platforms, however upon implementation of the PDEs in a back-to-back configuration (in which two PDEs are placed back-to-back sharing a single connection to the potentiostat), the detection limits for lead(II) and cadmium(II) correspond to 10 μg L−1 and 98 μg L−1 respectively within model aqueous (0.1 M HCl) solutions.

Quantificação do teor em metais em azeites e azeitonas da cv Cobrançosa

A olivicultura possui uma grande importância no cenário económico mundial, devido ao facto de a azeitona e o azeite fazerem parte da dieta alimentar de muitos países, especificamente os da região Mediterrânea. A “Cobrançosa” é uma cultivar Portuguesa com muita importância na região de Trás-os-Montes encontrando-se atualmente disseminada por seis regiões de Denominação de Origem Protegida. Os contaminantes emitidos para a atmosfera atingem as oliveiras e as azeitonas através da água, do ar, das plantas e do solo. Embora a ingestão de metais pesados através da azeitona e do azeite seja reduzida, a sua bioacumulação no organismo pode resultar em toxicidade e pôr em causa a saúde pública. É deste ponto de vista, que se centra o objetivo geral deste trabalho. Assim sendo, tentou-se quantificar o conteúdo de metais (de segurança e de qualidade), tais como o alumínio, arsénio, cádmio, chumbo, cálcio, cobalto, cobre, ferro, magnésio, manganês, sódio, níquel, e zinco nas azeitonas e azeites da cv “Cobrançosa” de seis clones em dois estados de maturação, com diferentes rendimentos de produção e diferentes atividades antioxidantes. Verificou-se que todos os metais analisados se encontram de acordo com o legislado e publicado por outros autores, verificando-se neste estudo particular que a componente genética que diferencia as amostras em estudo, não está significativamente relacionada com o conteúdo em metais.

Sedimentological, mineralogical, biogeochemical and micropaleontological parameters on sediment core PS69/849-2, Burton Basin, MacRobertson Shelf, East Antarctica

A multi-proxy study including sedimentological, mineralogical, biogeochemical and micropaleontological methods was conducted on sediment core PS69/849-2 retrieved from Burton Basin, MacRobertson Shelf, East Antarctica. The goal of this study was to depict the deglacial and Holocene environmental history of the MacRobertson Land-Prydz Bay region. A special focus was put on the timing of ice-sheet retreat and the variability of bottom-water formation due to sea ice formation through the Holocene. Results from site PS69/849-2 provide the first paleo-environmental record of Holocene variations in bottom-water production probably associated to the Cape Darnley polynya, which is the second largest polynya in the Antarctic. Methods included end-member modeling of laser-derived high-resolution grain size data to reconstruct the depositional regimes and bottom-water activity. The provenance of current-derived and ice-transported material was reconstructed using clay-mineral and heavy-mineral analysis. Conclusions on biogenic production were drawn by determination of biogenic opal and total organic carbon. It was found that the ice shelf front started to retreat from the site around 12.8 ka BP. This coincides with results from other records in Prydz Bay and suggests warming during the early Holocene optimum next to global sea level rise as the main trigger. Ice-rafted debris was then supplied to the site until 5.5 cal. ka BP, when Holocene global sea level rise stabilized and glacial isostatic rebound on MacRobertson Land commenced. Throughout the Holocene, three episodes of enhanced bottom-water activity probably due to elevated brine rejection in Cape Darnley polynya occured between 11.5 and 9 cal. ka BP, 5.6 and 4.5 cal. ka BP and since 1.5 cal. ka BP. These periods are related to shifts from warmer to cooler conditions at the end of Holocene warm periods, in particular the early Holocene optimum, the mid-Holocene warm period and at the beginning of the neoglacial. In contrast, between 7.7 and 6.7 cal. ka BP, brine rejection shut down, maybe owed to warm conditions and pronounced open-water intervals.

(Table 1, pages 283), Elemental concentrations of ferromanganese crusts from Lake Biwa, Japan

Ferromanganese crusts were sampled from the surface of a stone collected at a depth of 20 m in the northern part of Lake Biwa, Japan. These samples were analysed for 37 elements by neutron activation, X-ray fluorescence, and ICP-AE. The crusts were found to be enriched with Ba, P, B, As, and sometimes with Co, Ni, Cu and Sb. The elements were classified into 4 groups based on the varieties of host minerals (Fe-oxides, Mn-oxides or allochthonous materials) in which they were incorporated : elements mainly associated with 1) Mn-oxides : Ba, Ni, Cs, Sr and Co ; 2) Fe-oxides : P, B and As; 3) allochthonous materials : Na, K, Rb, Al, Ti, Sc, Hf and Th ; and 4) Mn-oxides plus allochthonous materials : rare earth elements and major heavy metals. The elemental compositions in the Lake Biwa concretions, including the crusts and Mn-deposits studied previously by these authors, were compared with those in other freshwater and oceanic concretions. As a result, the concentrations of rare earth elements and major heavy metals were found to be much lower, whereas those of B, P and As were higher in the Lake Biwa than in the oceanic concretions. These differences could be well explained in terms of the effects of sea salt, growth rates of the concretions, and pH of the formation environment.