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The population resident in areas around the East African Rift System (EARS) is facing serious problems associated with the availability and quality of drinking water. Groundwater wells, boreholes and springs are the main sources of drinking water in these areas. These sources are, however, characterised by elevated fluoride concentration (> 1.5 mg/L), resulting from the interactions with the surrounding volcanic rocks. The high fluoride levels found in the groundwater are often associated with the presence of other naturally occurring potentially toxic elements (PTEs), such as As, Mo, U and V, which are known to cause adverse effects on human health. The occurrence of such PTEs in the groundwater on the populated flanks of Mt. Meru, an active volcano situated in the EARS, has not been previously reported. The objective of this study is to determine the concentrations and distribution of PTEs in groundwater on the flanks of Mt. Meru to assess the potential health hazards that extend beyond the known fluoride issues in the study area. A large set of PTEs (Al, As, Ba, Cd, Cr, Cu, Fe, Mn, Mo, Ni, Se, Sr, Pb, U, V, W and Zn), physicochemical parameters and major elements were analysed in 48 groundwater samples sourced from wells, springs and tap water systems. To estimate the potential health risk associated with consumption of water with elevated concentrations of PTEs, chronic daily intake (CDI) and hazard quotient (HQ) were calculated. Preliminary results show that some of the water samples from the NE and SW flanks exceed the WHO tolerance limit for drinking water for some elements such as U (> 30 µg/L) and Mo (> 70 µg/L) as well as Na (> 200 mg/L) and K (> 50 mg/L). Estimated HQs indicate that such concentrations of Mo and U are not safe for consumption. Therefore, the continued drinking of water from these sources may result in serious health issues. Furthermore, the results show that some samples are characterised by total dissolved solids (TDS) values exceeding the permissible limits of WHO making the groundwater in the study area unsafe for drinking. The results presented in this paper are a part of a larger study on the groundwater quality in the Mt. Meru area and will serve to inform and direct exploitation of safe drinking water.

International audience

International audience

The international GEOVIDE expedition (GEOTRACES GA01, May-June 2014, spring period) had notably investigated the link between trace element cycling and the production, export and remineralization of particulate organic matter in the North Atlantic Ocean. Sampling was undertaken within different biogeochemical provinces including the Iberian Margin, the West European Basin, Reykjanes Ridge, Irminger Sea, Greenland Margin and the Labrador Sea showing contrasted physical, biological and chemical characteristics. Some of these areas are known to present an important spring phytoplankton bloom leading to the export of particles. Here, we report Particulate Organic Carbon (POC) export fluxes estimated using the 234Th-based approach at 12 stations as part of the GEOVIDE expedition. POC export fluxes were deduced by combining export fluxes of 234Thtotal with the POC/234Th ratio of sinking particles at the depth of export. Profiles of POC to 234Th ratio of particles were obtained for two size classes (>53µm and 1-53 µm) using in-situ pumps. Considering the large (>53 µm) particle fraction as representative of sinking material, POC export fluxes revealed latitudinal variations between provinces ranging from 25 mgC.m-2.d-1 in oligotrophic waters of the Iberian Plain to 62 mgC.m-2.d-1 in the Labrador Sea. Comparison between export and production, defined as ThE ratio, will be addressed in order to study POC export efficiencies. Preliminary data for ThE ratio show a range from 1% (Irminger Sea) to 12% (Labrador Sea) and suggest a relatively low-efficiency biological carbon pump in the North-Atlantic during late spring conditions.

Background and aims: One of the goals of human biomonitoring by the Flemish Centre of Environment and Health was to investigate exposure-response associations for various biomarkers of exposure and effect. The aim of this study is to describe the results of the exposure-effect associations involving exposure to metals and metalloids. Methods: Participants donated blood and/or urine for determination of concentrations of metals and metalloids (by ICP-MS) and biomarkers of effect (by various analytical methods). All subjects filled in a questionnaire to provide information on health, life-style and personal factors. The age groups sampled were mother-newborn pairs (maternal and cord blood), 14-15 year old adolescents (blood and urine) and 20-40 year old adults (urine). Regression models were fitted to determine associations between effect- and exposure markers, adjusted for relevant confounders and covariates (e.g. smoking, age, gender). Results: Many significant associations were in line with previously reported findings, while some were not published before. The size of newborns was negatively correlated with cord blood As, and positively with Cu. For adolescent girls, blood and urinary Tl were negatively correlated with development of pubic hair and breasts. In boys negative correlations were found between urinary Tl and pubic hair development, and between both urinary Tl and blood Pb and genital development. In adolescents, urinary Cd showed a negative correlation with the T4 thyroid hormone and a positive correlation with an indicator of DNA damage, while urinary Cd and urinary Cr showed positive correlation with indicators of kidney damage. Various correlations were found between metals and sex hormones (aromatase, SHBG, testosterone, estradiol) in boys. In adults, there was only a significant negative association between urinary As and blood platelet aggregation. Conclusions: Many exposure-effect associations were supported by the literature, some were reported earlier in a previous cycle of the Flemish human biomonitoring.

The techniques of diffusive equilibrium in thin films (DET) and diffusive gradients in thin films (DGT) were used for the first time in the Outer Section of Songkhla Lake in order to obtain high resolution profiles of total dissolved and labile trace metals in the sediment porewater. These tools provide useful information on sediment biogeochemistry and benthic fluxes. DGT measures labile metal species in situ by immobilizing them on a resin gel after diffusion through a diffusive gel whereas for DET equilibrium is established between the DET gel and the porewater. The expedition was carried in July, 2011 under the collaborative research program between the Laboratory of Analytical and Environmental Chemistry, Vrije Universiteit Brussel and the Marine and Coastal Resources Institute, Prince of Songkla University. Six DET probes and six DGT probes were deployed at the mouths of the Phawong, Samrong and U-Taphao canals.

International audience; PAHs, PCDD/Fs and non-ortho PCBs have been assessed in Yser and Upper-Scheldt river sediments. Higher contamination levels were observed in the Upper-Scheldt sediments: maximum concentrations for the 16 US-EPA PAHs, PCDD/Fs and non-ortho PCBs respectively amount to 8.9mgkg -1, 12ng TEQkg -1 and 5.1ng TEQkg -1. Diagnostic PAH ratios in sediments and atmospheric samples suggest that the PAH compounds are from pyrolytic origin, more specifically combustion processes. The huge consumption of coal in cokes-ovens and smelters and its use for house-heating in Northern France, although decreasing during the last decades, are in support of that suggestion. PCDD/F fingerprints in sediments and deposition material indicate that OCDD is the dominant congener. In addition use of pentachlorophenol (PCP) in the past led to a minor contribution of PCDD/Fs in our sediment samples. Non-ortho PCBs form a substantial fraction of the total TEQ concentrations observed in the sediments. Since the 1980s and 1990s a substantial reduction of the PCDD/F sediment concentrations is observed, but this is not the case for the PAHs.

The Southern Bight of the North Sea is strongly influenced by nutrients input giving rise to eutrophication effects. The river and atmosphere inputs are important sources of nutrients and organic matter for the coastal marine waters and directly influence the productivity/respiration of the system and the exchange of CO2 with the atmosphere. We studied the global cycling of inorganic nutrients (ammonium, nitrate, silicates, and phosphates) and dissolved inorganic carbon (DIC) using a budget approach. Nutrient, salinity and DIC distribution data were collected during 7 cruises in the framework of the Belgian funded project CANOPY. Budgets were computed for each of the nutrients and DIC and for different periods of the year by using the general Land-Ocean Interactions in the Coastal Zone (LOICZ) recommendations. Major inflows, outflows and transformations are identified and discussed to understand the interactions between nutrients cycling and DIC dynamics in a shallow coastal sea.

Dissolved and particulate mercury and methylmercury concentrations were determined in the Southern Bight of the North Sea and the Scheldt estuary in the period 1991–1999. Mercury and methylmercury concentrations are higher before 1995 than after 1995, especially in the fluvial part.The North Sea: In the offshore stations, dissolved Hg concentrations are generally higher in winter than in summer while the reverse is true for particulate Hg KD values (KD=the concentration of particulate Hg (HgP in pmol kg-1) divided by the concentration of dissolved Hg (HgD in pmol l-1)) range from 100,000 to 1000,000 l kg-1. Dissolved methylmercury concentrations vary from 0.05 to 0.25 pmol l-1 in summer and from d.l. to 0.23 pmol l-1 in winter and particulate methylmercury concentrations from 1.8 to 36 pmol g-1 in summer and from 0.9 to 21 pmol g-1 in winter. The KD ranges from 9,000 to 219,000 l kg-1.The Scheldt estuary: In winter, dissolved Hg concentrations are elevated in the upper estuary, decrease exponentially in the low salinity range followed by a very slow decrease towards the mouth. In summer, they are low in the fluvial part, increase in the low salinity range or in the mid-estuary and sometimes show an increase in the lower estuary. Particulate Hg concentrations do not show any seasonal trend.Dissolved MMHg concentrations are much lower in winter, when maximum concentrations are found in the upper estuary, than in summer. In summer, the MMHg concentrations are low at low salinity, they show a first increase in the salinity range from 3 to 12, a decrease in the mid-estuary and a second increase in the lower estuary.The highest particulate MMHg concentrations are found in the upper estuary, while in the lower estuary generally lower and more constant values are observed. The ratio of dissolved MMHg to dissolved Hg (cruise averages between 1.3% and 20%), is higher than the ratio of particulate MMHg to particulate Hg (cruise averages of 0.27–0.90%). The KD values for MMHg are lower in the summer (30,000–65,000) than in autumn and winter (77,000–114,000).The Scheldt river: In the fluvial part of the Scheldt, dissolved increases in the most upstream stations, while particulate Hg shows no particular pattern. Dissolved MMHg ranges from 0.1 to 0.39 pmol l-1 and particulate MMHg from 3.1 to 43.5 pmol g-1. The MMHg concentrations are comparable to those found in the estuary and no seasonal variations could be observed.