Selectivity of sodium pyrophosphate and unbuffered chlorides (CuCl2 and LaCl3) as extractants of aluminum bound to soil organic matter in soils of the sandy coastal plain in São Paulo state

O Al em complexos com matéria orgânica do solo é comumente determinado por técnicas de dissolução seletiva. Um extrator comum para essa forma do elemento é o pirofosfato de sódio. Devido à sua falta de seletividade para algumas amostras de solos, extratores não tamponados de Al, como CuCl2 e LaCl3, têm sido recomendados. A seletividade do pirofosfato de sódio (Al p) e dos cloretos não tamponados de cobre (AlCu) e de lantânio (AlLa) como extratores de Al ligado à matéria orgânica foi avaliada em 31 perfis de solos (Espodossolos e Neossolos Quartzarênicos), representativos das áreas sob vegetação de restinga do litoral paulista. Os resultados foram comparados aos obtidos com oxalato de amônio e KCl, seguindo-se as interpretações comumente observadas na literatura quanto à capacidade extratora e seletividade dos reagentes utilizados. Pirofosfato careceu de total seletividade para amostras que apresentaram formas inorgânicas de Al. Os reagentes CuCl2 e LaCl3, por sua vez, foram mais seletivos para as formas de Al orgânico nas mesmas amostras, cuja ordem de extractabilidade foi: Al p>AlCu>AlLa . As diferentes habilidades extratoras e as relações entre os reagentes utilizados possibilitaram convergir evidências analíticas a fim de analisar e interpretar algumas determinações, como saturação por Al no húmus e estabilidade das interações Corg-metal. Horizontes espódicos Bs, Bhs e Bsm detiveram a maior estabilidade da interação Corg-metal e saturação por Al no húmus entre todos os horizontes estudados. Dos resultados encontrados, conclui-se que todos os reagentes analisados podem ser utilizados como extratores de Al associado à matéria orgânica dos solos, uma vez que permitiram estabelecer relações e interpretações contundentes quanto ao entendimento da química dos complexos Al-húmus dos solos de restinga estudados. Esses extratores, portanto, são adequados e têm potencial para os estudos e entendimento dos processos envolvidos na gênese dos Espodossolos tropicais derivados de sedimentos quartzosos costeiros.Aluminum in complexes with soil organic matter is usually determined by selective extraction techniques. A common extractant for this Al form is sodium pyrophosphate. Due to its lack of selectivity for some soil samples, unbuffered Al extractants, such as CuCl2 and LaCl3, have been recommended. The selectivity of sodium pyrophosphate (Al p) and of unbuffered Cu (AlCu) and La (AlLa) chlorides to extract aluminum bound to soil organic matter (Al-humus) was evaluated in soil samples from 31 pedons (Spodosols and Quartzipsamments) representative of the sandy coastal plains of the state of São Paulo. The results were compared with those obtained by ammonium oxalate and KCl and the extraction capacity and selectivity of the reagents interpreted as commonly used in the literature. Pyrophosphate was not totally selective for some samples containing inorganic aluminum. CuCl2 and LaCl3, in turn, were more selective for Al-humus in the same samples and their order of extractability was: Al p>AlCu>AlLa . Based on the different extraction capacities and the relations between the reagents used the analytic evidences were converged in order to analyze and interpret parameters such as Al saturation in the soil organic matter and stability of C-metal interactions. The stability of the interaction C-metal and humus Al saturation of all horizons studied was greater in the Bs, Bhs and Bsm spodic horizons. Based on the results it was concluded that all reagents studied can be used as Al extractants since they allow establishing relations and interpretations that may help understanding the complex chemistry of Al-humus on the studied Restinga soil. These extractors are therefore adequate and promising to study and understand processes involved in the genesis of tropical Spodosols derived from sandy coastal plain sediments.Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)FAPES

Analysis of total arsenic content in purchased rice from Ecuador

Natural and anthropogenic sources contribute to arsenic contamination in water and human food chain in Andean countries. Human exposure to arsenic via rice consumption is of great concern in countries where this crop is the dominant staple food, and limited information is available on the arsenic contamination on rice in Ecuador. This work was to contribute to the lack of knowledge analysing total arsenic by hydride generation-atomic absorption spectrometry in the samples of white, brown and parboiled rice purchased in Ecuadorian markets and produced in the two main rice wetlands in Ecuador, Guayas and Los Ríos, were carried out. For the samples from Guayas, arsenic concentration in white, brown and parboiled rice were 0.174 ± 0.014, 0.232 ± 0.021, and 0.186 ± 0.017 mg/kg respectively, whereas samples of white rice from Los Ríos showed a total arsenic level of 0.258 ± 0.037 mg/kg. This last arsenic concentration exceeds recommended maximum permissible limit by the FAO/WHO. Obtained data have available to estimate the Ecuadorian dietary exposure revealing serious health risk for population.S

Evaluation of Soil Organic Carbon Storage of Atillo in the Ecuadorian Andean Wetlands

Identifying the SOC levels and revealing the potential of SOC storage of ecosystems difficult to sample and study are necessary contributions to the understanding of the global reserves of SOC. Wetlands store large amounts of SOC within their soils. They have an important role in water regulation and have great biological and floristic diversity. Therefore, this study aimed to assess the SOC stock in Atillo micro-watershed in the Ecuadorian Andean wetlands at two soil depths (0¿30 cm and 30¿60 cm below ground) and to assess the importance of the ecosystem and its conservation in favor of reducing emissions due to degradation processes. For that, we sampled the study zone with 101 composite samples of soil to obtain the SOC storage for each sample point in Mg/ha. A SOC estimation to evaluate its spatial distribution was performed using the geostatistical method Kriging. The results show a high storage capacity of the study zone with SOC values of 126 to 454 Mg/ha in the 0¿30 cm soil profile and 148 to 350 Mg/ha in the 30¿60 cm soil profile. The preservation and protection mechanisms of high SOC reserves should be taken into account to prevent the emission of CO2

Caracterización de la vegetación de los acantilados del Parque Natural de las Islas Cíes y su relación con la colonia de gaviota patiamarilla (Larus cachinnans)

La vegetación característica de los pastos aerohalófilos de Galicia, adscrita a la comunidad Dauco-Festucetum pruinosae, no se encuentra representada en los acantilados estudiados de las islas Cíes. La singularidad en cuanto a la composición florística de estos acantilados, donde son comunes especies pioneras o de marcado carácter nitrófilo (p. ej. Holcus lanatus, Urtica membranacea), está relacionada con la influencia que ejerce la colonia de gaviota patiamarilla (Larus cachinnans) que se estima en unas 20.000 parejas reproductoras. Por otra parte, también se han encontrado importantes cambios en la frecuencia de aparición de ciertas especies tanto a nivel estacional como interanual

Nitrógeno (NH4+, NO3-), fósforo asimilable y metales traza (Hg, Cd, Pb, Zn, Ni y Cu) en suelos de la colonia de la gaviota patiamarilla (Larus cachinnans) en el Parque Natural de las Islas Cíes

La gaviota patiamarilla (Larus cachinnans) presenta en el Parque Natural de las Islas Cíes su mayor colonia de cría con una población aproximada de 20.000 parejas reproductoras. En el presente trabajo se pretende evaluar el efecto que sobre el contenido en nutrientes y metales traza en el suelo puede tener esta colonia. Para ello se seleccionaron tres acantilados en las islas Cíes y una zona control en cabo Home (sin presencia de gaviotas). Los resultados obtenidos han puesto de manifiesto que los suelos de los acantilados de la Percha, zona donde la gaviota patiamarilla lleva criando con densidades elevadas por lo menos desde los años 70, presenta para el nitrógeno, fósforo asimilable y metales traza concentraciones significativamente más elevados que la zona control. Los otros dos acantilados de las islas Cíes (Campana y Figueiras) presentaron, en general, concentraciones intermedias entre las zona control y los suelos de los acantilados de la Percha

Seabird colonies as important global drivers in the nitrogen and phosphorus cycles

The global impact of seabird populations on nutrient cycles is poorly understood. Here, the authors use a bioenergetic model and a global seabird population inventory to estimate the amounts of nitrogen and phosphorus excreted by seabirds and estimate them to be 591 Gg N y−1 and 99 Gg P y−1 respectively

Evaluation of Soil Organic Carbon Storage of Atillo in the Ecuadorian Andean Wetlands

Identifying the SOC levels and revealing the potential of SOC storage of ecosystems difficult to sample and study are necessary contributions to the understanding of the global reserves of SOC. Wetlands store large amounts of SOC within their soils. They have an important role in water regulation and have great biological and floristic diversity. Therefore, this study aimed to assess the SOC stock in Atillo micro-watershed in the Ecuadorian Andean wetlands at two soil depths (0–30 cm and 30–60 cm below ground) and to assess the importance of the ecosystem and its conservation in favor of reducing emissions due to degradation processes. For that, we sampled the study zone with 101 composite samples of soil to obtain the SOC storage for each sample point in Mg/ha. A SOC estimation to evaluate its spatial distribution was performed using the geostatistical method Kriging. The results show a high storage capacity of the study zone with SOC values of 126 to 454 Mg/ha in the 0–30 cm soil profile and 148 to 350 Mg/ha in the 30–60 cm soil profile. The preservation and protection mechanisms of high SOC reserves should be taken into account to prevent the emission of CO2