Traceability statement for the determination of total chromium fraction in serpentine soils by atomic absorption spectrometry

The purpose of this work is to contribute for the metrological traceability statement of chemical measurements. Traceability statement for total chromium mass fraction in serpentine soils was developed. Accordingly, the quantity values requiring a high degree of control are calibration and quality control standard solutions, matrix certified reference material and the calibration curve model fit

Monitoring Hg and Cd contamination using red swamp crayfish (Procambarus clarkii): implications for wetland food chain contamination

Environmental pollution is one of the most serious causes of degradation of Mediterranean wetlands. Mercury (Hg) and cadmium (Cd) are of particular concern due to biomagnification. Here, we used red swamp crayfish (Procambarus clarkii) to monitor the spatial and temporal patterns of these two metals in a Portuguese rice field system. We sampled the crayfish in three different sites and three different time periods in the Sado River Basin (Portugal). We measured temperature, pH, total dissolved solids and conductivity in the water. Hg and Cd were measured in the crayfish abdominal muscle tissue and exoskeleton. In muscle, a spatial pattern was found for the accumulation of Cd while for Hg, only a temporal pattern emerged. The spatial pattern for Cd seemed to reflect the mining history of the sites, whereas the temporal pattern for Hg seemed related to the flooding of rice fields. We suggest that this flooding process increases Hg bioavailability

Influence of diagenetic processes and terrestrial/anthropogenic sources in the REE contents of the Cascais submarine canyon (Iberian western coast)

ABSTRACT: Temporal variations of rare earth elements (REE) and their fractionation patterns, major elements, Pb and Hg were determined in two multicores collected at 445 and 2100 m water depth (mwd) in the Cascais submarine canyon (CSC). The PAAS-normalized REE patterns suggest mixing of Tagus estuarine and marine sediments, marked by MREE (Nd‐Dy series) enrichment and by positive Eu-anomaly, with marine sediments. The positive Eu/Eu* implies incorporation of detrital feldspar minerals derived from the estuary. Ce/Ce*, (La/Yb)PAAS and (Nd/Yb)PAAS show differences between the two cores. Core 252-35 from the shallower site is enriched in HREE (Ho‐Lu series) over LREE (La‐Pr series), a pattern also found in the Tagus estuary in the vicinity of an abandoned chemical complex, where the environment is affected by the legacy of massive-sulfide ores processing. There seems to be only limited down-canyon sediment transport to the deeper reaches where core 252-32 was collected. This deeper site shows Ce/Ce* peaks coinciding with low (La/Yb)PAAS values suggesting preferential diagenetic remobilization of LREE relative to HREE. Upcore Pb/Al and Hg/Corg trends observed in both cores indicate dispersion of the anthropogenic component from the estuary through the CSC, which is less obvious from the ∑REE/Al trends particularly in the deeper site. This may suggest the influence of diagenetic processes in the REE signal, associated with relatively low sediment accumulation rates.info:eu-repo/semantics/publishedVersio

Contamination by heavy metals in aquatic trophic webs: the case of otter and red-swamp crayfish

In a detailed scanning electron microscope study of the recrystallisation of an IF steel it was observed that the new grains went through an equiaxed stage which became elongated along the rolling direction and then became equiaxed again when recrystallisation was complete. A theory of how the final crystal structure arises from the deformed matrix is proposed in which grain impingement during growth, when it involves orientation pinning, is followed by crystal aggregate spheroidisation to give the final polycrystalline structure. This means that a proportion of grains in a recrystallised aggregate have arisen from several separate nucleation events. The model, which is general, has implications for texture formation and can apply to both primary and secondary recrystallisation. It can also explain why the grain growth exponent is usually measured to be between 2 and 3. © 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.link_to_subscribed_fulltex

13 anos de monitorização da descarga do emissário submarino da Guia: integração na DQA

O Programa das Nações Unidas para o Ambiente define monitorização como “o processo de observação repetitivo com fins definidos, de um ou mais elementos do ambiente, de acordo com um planeamento prévio no espaço e no tempo, utilizando metodologias comparáveis para caracterização ambiental e colheita de dados”. A Directiva Quadro da Água (DQA), o instrumento orientador na União Europeia para gestão das águas superficiais interiores, águas de transição, águas costeiras e águas subterrâneas, suporta este conceito propondo, no entanto, três níveis para os programas de monitorização: (1) monitorização de vigilância orientada para a evolução a longo prazo; (2) operacional, orientada para zonas em risco de não atingir os objectivos de qualidade requeridos pela DQA; (3) de investigação orientada para a compreensão e quantificação dos processos responsáveis por excessos que levam ao incumprimento da DQA. Embora sejam os Estados-Membros quem devam adoptar estas medidas e cumprir os seus objectivos, o comportamento pró-activo de algumas empresas contribui significativamente para o cumprimento das exigências da DQA. A SANEST, Saneamento da Costa do Estoril, empresa gestora do Sistema de Saneamento da Costa do Estoril implementou um programa de monitorização da descarga do emissário submarino da Guia. Este programa deu continuidade ao iniciado em 1993, antes da entrada em funcionamento do sistema, e é o maior programa de monitorização a nível nacional em zonas costeiras, que inclui investigação detalhada a vários níveis. O progressivo aumento do número de parâmetros e a adaptação de metodologias, quer na ETAR quer no meio receptor, demonstra também a preocupação desta empresa pela salvaguarda e gestão sustentável dos recursos. Neste trabalho são apresentados os principais resultados do programa de monitorização referido, levado a cabo por Laboratórios de Estado e Universidades portugueses, que em conjunto cobrem os requisitos normativos nacionais e internacionais, em termos analíticos, e detêm o conhecimento necessário à componente de monitorização operacional, preconizada na DQA

Submarine Cascais Canyon as a sediment conduit to the deep sea : comparison with adjacent slopes

Submarine canyons are known to be important conduits that trap, accumulate and deliver both natural and anthropogenic sediments from the shelf to the deep sea. Ten multi-cores from the Cascais Canyon and from the neighbour slopes (off Estremadura and Sines) were dated by 21Opb methodologies and analyzed for texture, major and trace metals to evaluate the role of submarine canyons in the transport of anthropogenic metals to the abyssal plains. Higher accumulation mass rates were determined in the upper Cascais Canyon than in the lower canyon and slopes. Enrichment factors (EF) were used to evaluate the level of metal enrichment in the studied areas. EF values exceeding natural background concentrations were obtained for Pb suggesting an anthropogenic and/or diagenetic source for Pb enrichment in the Cascais Canyon, but also, to a lesser extent, in the Estremadura and Sines slopes. Studies of provenance based on the ratio of different stable Pb isotopes can help to determinethe origin of such metal in the sediments

Alterações recentes nas razões isotópicas de Pb em sedimentos do Canhão Submarino de Cascais, Portugal

Temporal variations in lead concentrations and stable lead isotopic ratios in two sediment cores from the Cascais Canyon shows changes in sources of Pb during the last two centuries. The increase of total Pb contents wIth the evolution of Pb ratio recorded in both cores reveals the Increase of Pb from industrial sources. Nevertheless, this increase is lower in deeper core location (252-32) due to dilution and mixing with uncontaminated marine materials. An isotopic shift towards lower Pb/Pb in the shallower core (252-35) during the 1970s may reflect the increasing number of vehicles in the Lisboa area during that time

Cluster temporal de metales en un testigo corto de sedimento del Cañón Submarino de Cascais (Margen de Portugal)

The Cascais Canyon delivers contaminated sediments from the shelf to the deep marine environment. Multi-core PE252-32, located at 2100 m water depth in the canyon, records the latest 300 years of sedimentation. It was dated by 210Pb and analyzed texturally and geochemically for major elements and selected trace metals (Cu, Cr, Hg, Li, Ni, Pb and Zn). Cluster analysis performed on the down-core geochemical data identified four groups of variables related by grain-size, geochemical source and composition. Mercury, Pb and Zn were grouped in a cluster representing the anthropogenic component. Cluster analysis was applied again particularly to the latter cluster relatively to depth, in order to constrain the onset and temporal evolution of anthropogenic contamination. A second clustering, made on the basis of Hg, Pb and Zn, grouped samples by age and degree of anthropogenic contamination. One cluster contained relatively uncontaminated samples older than 1900 AD, and another cluster samples younger than 1900 AD with distinct metal enrichment. Maximum enrichments occurred during the early 1980s, followed by a slight recovery from the mid-1980s to the present. Mercury was the element with the highest enrichment factor (EFHg=5). Despite relatively low accumulation rates at this core location, our results show the importance of the Cascais Canyon as a transport route for contaminated sediments from the Tagus prodelta into the deep regions of the Portuguese Margin.El Cañón submarino de Cascais distribuye sedimentos contaminados de la plataforma continental al medio marino profundo. El testigo PE252-32, situado a 2100 metros de profundidad dentro del cañón, registra los últimos 300 años de su sedimentación. Se ha datado con 210Pb y ha sido analizada su granulometría, elementos mayoritarios y traza (cobre, cromo, mercurio, litio, níquel, plomo y zinc). Se ha llevado a cabo un análisis estadístico clúster, inicialmente aplicado a las series de datos geoquímicos en función de la profundidad, identificándose 4 grupos de variables, relacionados por la granulometría, procedencia y composición geoquímica. Los metales mercurio, plomo y zinc aparecen agrupados en un clúster que representa la componente antropogénica. A continuación el mismo análisis estadístico se aplicó específicamente a este grupo, en función de la profundidad, organizando las muestras según la edad de contaminación antropogénica. Como resultado las muestras quedan agrupadas en dos clústers principales, el de las muestras no contaminadas y más antiguas de 1900 AC, y el de las muestras más recientes de 1900 AC, marcando esta fecha el inicio de la contaminación por impacto de la actividad humana. Los máximos enriquecimientos ocurren durante el inicio de la década de los años ochenta, seguidos de un ligero descenso a partir de mediados de la misma década hasta la actualidad. De entre los demás, el mercurio es el elemento con el mayor grado de enriquecimiento (EFHg=5). Aunque la tasa de acumulación de sedimentos en este lugar es relativamente baja, los resultados obtenidos ponen en evidencia la importancia del Cañón submarino de Cascais como vía de transporte de sedimentos contaminados depositados en el pro-delta del Tajo a las regiones profundas del margen de Portugal