Distribution of rare earth elements and assessment of anthropogenic gadolinium in estuarine habitats: The case of Loire and Seine estuaries in France

Rare earth elements (REEs), attractive to society because of their applications in industry, agriculture and medicine, are increasingly released into the environment especially in industrialized estuaries. This study compared the REE distribution in the abiotic compartments: water (dissolved phase (<0.45 μm), suspended particulate matter (SPM)) and sediment of the Loire and Seine estuaries (France). A total of 8 and 6 sites were investigated in the Loire and Seine, respectively, as well as 5 additional offshore sites for the Loire. Total REE concentrations were higher in the Loire for the dissolved phase (93.5 ± 63.3 vs 87.7 ± 16.2 ng/L), SPM (173.9 ± 18.3 vs 114.0 ± 17.8 mg/kg dw) and sediments (198.2 ± 27.9 vs 73.2 ± 27.4 mg/kg dw), explained by higher geogenic inputs. Individual REE contributions along with normalization highlighted heavy REE enrichments and Gd positive anomalies in the dissolved phase of the two estuaries, whereas REE distributions in SPM and sediments followed the natural abundance of the REE classes. The calculated Gd anomalies in the dissolved phase were higher in the Seine (9.7 ± 3.4) than in the Loire (3.0 ± 0.8), corresponding to 88.3 ± 5.1 % and 64.4 ± 11.1 % of anthropogenic Gd. This demonstrates a higher contamination of the Seine estuary, certainly due to the difference in the number of inhabitants between both areas involving different amounts of Gd used in medicine. The offshore sites of Loire showed lower total REE concentrations (55.8 ± 5.8 ng/L, 26.7 ± 38.2 mg/kg dw and 100.1 ± 11.7 mg/kg dw for the dissolved phase, SPM and sediments, respectively) and lower Gd anomalies (1.2 ± 0.2) corresponding to only 13.3 ± 3.9 % of anthropogenic Gd, confirming a contamination from the watershed. This study comparing two major French estuaries provides new data on the REE distribution in natural aquatic systems.

Barrage fishponds, a funnel effect for metal contaminants on headwater streams

Fishponds are man-made shallow water bodies that are still little studied because of their small size. They represent high value ecosystems, both environmentally (biodiversity hotspot) and economically (fish production). They can have a high place on the hydrographic network, so their influence on water quality is of first importance for rivers and water bodies located downstream and monitored under the Water Framework Directive. These small water bodies can be a source of contaminants during draining period or an efficient buffer for pesticides. We wanted to evaluate whether these ponds could also be a remediation tool against metals by following the annual evolution of upstream/downstream flows. Cadmium, copper, lead and zinc concentrations were quantified in the dissolved phase upstream and downstream of three ponds, each one having a specific agricultural environment (traditional or organic). Metal concentration was quantified in sediments and water. For the dissolved phase, the predictive non-effect concentration was often exceeded, suggesting an environmental risk. Results highlighted also greater quantity of metals at the downstream of the pond compared to the upstream, suggesting remobilization into the ponds or direct cross-sectional contributions from the watershed (e.g. runoff from crops) or even remobilization. Regarding sediments, minimal contamination was shown but a high mineralogical variability. No buffer effect of ponds, which could reduce the risk of acute or chronic toxicity, was detected.

The contribution of 137Cs export flux from the Tone River Japan to the marine environment

The contribution of ¹³⁷Cs transport to the marine environment via the Tone River, Japan was investigated. This river has the largest discharge among rivers on the North Pacific side of eastern Japan. The sampling site was located upstream near the river mouth and dissolved and particulate ¹³⁷Cs in the river water was measured during 2014-2015, three years after the Tokyo Electric Power Corporation Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. Annual fluxes of total (dissolved and particulate) ¹³⁷Cs with considering desorption of ¹³⁷Cs from riverine particles by change of salinity from the Tone River were similar in both years (78-107 × 10⁹ Bq/y), indicating that about 0.03-0.06% of the estimated total amount of ¹³⁷Cs deposited in the catchment (1.9-2.8 × 10¹⁴ Bq) was transported to the marine environment each year. Although the annual flux was about one order of magnitude lower than the daily direct discharge into the ocean from the FDNPP (800 × 10⁹ Bq/y) during the corresponding period, continuous monitoring of rivers in the southern coastal area of east Japan on the North Pacific side are needed for the effect of ¹³⁷Cs release via the rivers in the Kanto area over the long-term.

Residues of pesticides and some metabolites in dissolved and particulate phase in surface stream water of Cachapoal River basin, central Chile

In the last twenty years, pesticide use in Chile has increased more than 160%, generating a greater risk of water resources pollution. The objective of this study was to assess the presence of 22 pesticides and 12 degradation products in surface water samples from the Cachapoal River basin, Central Chile, an area characterized by intense agricultural activity. Pesticide concentrations in the dissolved phase (DP) and particulate phase (PP) in samples collected in the dry season and after precipitation events was assessed. The solid-phase extraction technique was used to preconcentrate the samples and GC/MS and LC/MS were used to detect pesticides. The results present spatio-temporal variations in the proportion and concentration of pesticides and their degradation products in both the DP and PP for each site and sampling period. The most ubiquitous compounds in the dissolved phase were atrazine, atrazine-2-hydroxy (HA), cyprodinil, pyrimethanil, and tebuconazole, while in the particulate phase HA, imidacloprid, diazinon and pyrimidinol were detected. The results presented in this study make up the first record of pesticides in the dissolved and particulate phases in surface water in Chile. They show that the problem of pesticide contamination undoubtedly affects the quality of bodies of water in agricultural areas in Chile and support the need for a proper assessment of the water quality of the Cachapoal River in the future.

Macondo oil in northern Gulf of Mexico waters - Part 1: Assessments and forensic methods for Deepwater Horizon offshore water samples

Forensic chemistry assessments documented the presence of Macondo (MC252) oil from the Deepwater Horizon (DWH) spill in offshore water samples collected under Natural Resource Damage Assessment (NRDA) protocols. In ocean depths, oiled water was sampled, observed, photographed, and tracked in dissolved oxygen (DO) and fluorometry profiles. Chemical analyses, sensor records, and observations confirmed the shifting, rising oil plume above the wellhead while smaller, less buoyant droplets were entrapped in a layer at ~1000-1400 m and advected up to 412 km southwest. Near-surface oil samples showed substantial dissolution weathering from oil droplets rising through the water column, as well as enhanced evaporative losses of lighter n-alkanes and aromatic hydrocarbons. Dispersant effects from surface applications and injected at the wellhead were seen in oil profiles as enhanced weathering patterns (increased dissolution), thus implying dispersants were a functionally effective mediation treatment. Forensic assessment methods are detailed in the Supplemental information (SI).