Revisamos las consecuencias ecológicas de la deposición de N en las cinco regiones mediterráneas del mundo. La estacionalidad de las precipitaciones y los incendios regulan el ciclo del N en estos ecosistemas con escasez de agua, donde domina la deposición seca de N. La acumulación de nitrógeno en los suelos y en las superficies de las plantas produce picos de disponibilidad con las primeras lluvias invernales. El desacoplamiento entre los flujos de N y la demanda de la planta promueve pérdidas por lixiviación y emisiones de gases. Las diferencias en la disponibilidad de P pueden controlar la respuesta a los aportes de N y la susceptibilidad a la invasión de plantas exóticas. Los pastos invasores se acumulan como combustible durante la estación seca, alterando los regímenes de incendios. California y la cuenca mediterránea son las más amenazadas por la deposición de N; sin embargo, existe evidencia limitada de los impactos de la deposición de N fuera de California. En consecuencia, se necesita más investigación para determinar las cargas críticas para cada región y tipo de vegetación en función de los elementos más sensibles, como los cambios en la composición de las especies de líquenes y el ciclo del N.

Sediment cores from the deep Balearic basin and the Cretan Sea provide evidence for the accumulation of Cd, Pd and Zn in the top few centimeters of the abyssal Mediterranean sea-bottom. In both cores, 206Pb/207Pb profiles confirm this anthropogenic impact with less radiogenic imprints toward surface sediments. The similarity between excess 210Pb accumulated in the top core and the 210Pb flux suggests that top core metal inventories reasonably reflect long-term atmospheric deposition to the open Mediterranean. Pb inventory in the western core for the past 100 years represents 20-30% of sediment coastal inventories, suggesting that long-term atmospheric deposition determined from coastal areas has to be used cautiously for mass balance calculations in the open Mediterranean. In the deeper section of both cores, Al normalized trace metal profiles suggest diagenetic remobilization of Fe, Mn, Cu and, to a lesser extent, Pb that likely corresponds to sapropel event Si

International audience | Phytoplankton diversity, primary and bacterial production, nutrients and metallic contaminants were measured during the wet season (July) and dry season (March) in the Bach Dang Estuary, a sub-estuary of the Red River system, Northern Vietnam. Using canonical correspondence analysis we show that phytoplankton community structure is potentially influenced by both organometallic species (Hg and Sn) and inorganic metal (Hg) concentrations. During March, dissolved methylmercury and inorganic mercury were important factors for determining phytoplankton community composition at most of the stations. In contrast, during July, low salinity phytoplankton community composition was associated with particulate methylmercury concentrations, whereas phytoplankton community composition in the higher salinity stations was more related to dissolved inorganic mercury and dissolved mono and tributyltin concentrations. These results highlight the importance of taking into account factors other than light and nutrients, such as eco-toxic heavy metals, in understanding phytoplankton diversity and activity in estuarine ecosystems.

International audience | Phytoplankton diversity, primary and bacterial production, nutrients and metallic contaminants were measured during the wet season (July) and dry season (March) in the Bach Dang Estuary, a sub-estuary of the Red River system, Northern Vietnam. Using canonical correspondence analysis we show that phytoplankton community structure is potentially influenced by both organometallic species (Hg and Sn) and inorganic metal (Hg) concentrations. During March, dissolved methylmercury and inorganic mercury were important factors for determining phytoplankton community composition at most of the stations. In contrast, during July, low salinity phytoplankton community composition was associated with particulate methylmercury concentrations, whereas phytoplankton community composition in the higher salinity stations was more related to dissolved inorganic mercury and dissolved mono and tributyltin concentrations. These results highlight the importance of taking into account factors other than light and nutrients, such as eco-toxic heavy metals, in understanding phytoplankton diversity and activity in estuarine ecosystems.

Thyroid hormone (TH) agonist and antagonist activities of water sources along the Yangtze River in China were surveyed by a green monkey kidney fibroblast (CV-1) cell-based TH reporter gene assay. Instrumental analysis was conducted to identify the responsible thyroid-active compounds. Instrumentally derived l-3,5,3′-triiodothyronine (T₃) equivalents (T₃-EQs) and thyroid receptor (TR) antagonist activity equivalents referring to dibutyl phthalate (DBP-EQs) were calculated from the concentrations of individual congeners. The reporter gene assay demonstrated that three out of eleven water sources contained TR agonist activity equivalents (TR-EQs), ranging from 286 to 293 ng T₃/L. Anti-thyroid hormone activities were found in all water sources with the TR antagonist activity equivalents referring to DBP (Ant-TR-EQs), ranging from 51.5 to 555.3 μg/L. Comparisons of the equivalents from instrumental and biological assays suggested that high concentrations of DBP and di-2-ethylhexyl phthalate (DEHP) were responsible for the observed TR antagonist activities at some locations along the Yangtze River.

We monitored curbside airborne particulate matter (PM) concentrations and its proinflammatory capacity during 3 weekends when vehicle traffic was excluded from Park. Ave., New York City. Fine PM concentration peaked in the morning regardless of traffic while ultrafine PM was 58% lower during mornings without traffic. Ultrafine PM concentration varied linearly with traffic flow, while fine PM spiked sharply in response to random traffic events that were weakly correlated with the traffic signal cycle. Ultrafine PM concentrations decayed exponentially with distance from a cross street with unrestricted traffic flow, reaching background levels within 100 m of the source. IL-6 induction was typically highest on Friday afternoons but showed no clear relationship to the presence of traffic. The coarse fraction (>2.5 μm) had the greatest intrinsic inflammatory capacity, suggesting that coarse PM still warrants attention even as the research focus is shifting to nano-particles.

The concentration of dissolved polycyclic aromatic hydrocarbons (PAH) in influent, effluent, and within a detention pond system was measured. The "soluble fraction" was operationally defined as the PAHs in solution that passed through a 1.2 μm filter. The results show that influent and effluent PAH concentrations were similar, indicating that dissolved PAH moved essentially unhindered through the detention pond system. In general, low molecular weight PAH were present at the highest concentrations and the highest PAH concentrations were measured in Summer. Also, year-to-year variations in PAH concentration were observed. At the end of sufficiently large storms, the pond was comparably unpolluted. During dry periods, the dissolved PAH concentration rose, possibly due to evapoconcentration and by partitioning of PAH from trapped contaminated sediment in the detention pond system. This study provides evidence that aqueous-phase PAH concentrations in runoff water were relatively unaffected by the passage through a conventional detention pond system.

Trace metal uptake was measured for tropical and temperate leafy vegetables grown on soil from an urban sewage disposal farm in the UK. Twenty-four leafy vegetables from East Africa and the UK were assessed and the five vegetable types that showed the greatest Cd concentrations were grown on eight soils differing in the severity of contamination, pH and other physico-chemical properties. The range of Cd concentrations in the edible shoots was greater for tropical vegetables than for temperate types. Metal uptake was modelled as a function of (i) total soil metal concentration, (ii) CaCl₂-soluble metal, (iii) soil solution concentration and (iv) the activity of metal ions in soil pore water. Tropical vegetables were not satisfactorily modelled as a single generic ‘green vegetable’, suggesting that more sophisticated approaches to risk assessment may be required to assess hazard from peri-urban agriculture in developing countries.

Ancient eggshells over the past 700 years were extracted from an ornithogenic sediment profile on Guangjin Island, South China Sea. Based on SEM and nitrogen isotope analyses, we determined that neither post-depositional processes nor seabirds’ dietary changes had a large influence on eggshell Hg levels. The historical change of Hg in these eggshells was reconstructed. Eggshell Hg was a marker for past Hg deposition in marine environment. The eggshell Hg showed three small peaks at around 1300AD, 1600 AD and 1700–1750AD and rapid increase since 1800 AD. Before 1970 AD the Hg deposition in the Xisha area had global distribution characteristics, with increased Hg emissions due to global anthropogenic activities in industrial times. However, after 1970 AD, a further sharp increase up to present day occurred, implying that the Hg production center had gradually shifted from Europe and America to Asia.