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The Salada coastal lagoon is located in Veracruz (Mexico) near the Laguna Verde Nuclear Power Plant (LVNPP). Currently, the lagoon receives the cooling waters used in the LVNPP. To evaluate the fluxes and mobilization of trace elements due to human activities in the area, two sediment cores from the coastal flood plains of Salada Lagoon were analysed. Cores were collected using PVC tubes. Sediments cores were analysed every centimetre for dating ( 210 Pb by alpha detector) and trace metal analysis using ICP-Mass Spectrometry. The dating of both sediment cores covers the period from 1900 to 2013, which includes the construction of the LVNPP (1970's). The Normalized Enrichment Factor shows enrichment of Ag, As and Cr in both sediment cores. These enrichments correspond to the extent of mining activity (which reached a maximum in the 1900's) and to the geological setting of the coastal zone. The profiles of the element fluxes in both sediment cores reflected the construction and operation of the LVNPP; however, the elements content did not show evidence of pollution coming from the LVNPP. [ABSTRACT FROM AUTHOR]

Baselines for major and trace elements were determined from surface sediment samples from sites located along the Central Pacific Mexican Shelf (CPMS; 16.7–20.45° N). This study area is next to the biggest harbours in Mexico, for example touristic (Puerto Vallarta and Acapulco), touristic and industrial (Manzanillo), and industrial harbours (Lázaro Cárdenas). The industrial harbours have been expanding, transporting tonnes of materials to Asia and North and South America. Oceanographic campaigns were conducted to obtain sediment from depths ranging from 56 to 159 m. The grain size was predominately fine fraction (<63 μm; mean 56 μm ± 30%). More than 50 elements were analysed, and methods were validated with certified reference materials. The results extracted the iron ore signal; enrichment and the association between Fe and Co, Cr, Cu, Mg, Mn, Mo, Ni, V, and Zn were determined for the sediments. Arsenic is enriched in the CPMS; the Normalized Enrichment Factor average (NEF AV ) for As is NEF AV = 8 ± 7. However the ratio between As and Cs indicates a natural origin in the most of the sites. Cadmium, Mo, and Ag were significantly correlated with C org enhanced precipitation of sulfide-reactive metals. Moreover, an anthropogenic influence was detected for Hg (NEF AV = 4.3 ± 1.5) and Ag (NEF AV = 8.5 ± 2.6) in the shelf near the heavily industrialized harbour of Lázaro Cárdenas. [ABSTRACT FROM AUTHOR]

Abstract: Rare earth elements (REE from La to Lu), Al and Fe were analysed in 35 surface sediment samples from the Marabasco River-Estuary system, located in the active tectonic zone of Cocos Plate near the active Colima Volcano. The Peña Colorada iron mine is found in the Marabasco watershed and the river sediments are enriched by iron oxy-hydroxides. The average REE content is 86.9±26.8 mg·kg−1 and 95.5±50.3 mg·kg−1 for river and estuarine sediments respectively, which is low in comparison to other tropical coastal systems. The REE light/heavy content ratios (L/H) of Marabasco sediments are also low with averages of 5.2±0.8 (river) and 5.7±0.9 (estuary) due to the minor presence of LREE. The REE signature of the sediment by normalisation with chondrite indicated a slight negative anomaly of Europium and the absence of a Cerium anomaly. REE concentrations in the Marabasco sediments show a strong correlation with Al and Fe, with LREE having a greater affinity for Fe and HREE for Al. This antagonism is REE-ordered by their atomic number sequence in the river sediment case. This has not been previously observed in the environment and the presence of magnetite and the iron oxy-hydroxide enrichment may enhance it. This did not occur in the estuary of the Marabasco mine region where Al and Fe are both well correlated. [Copyright &y& Elsevier]

Coastal vegetated habitats can be important sinks of organic carbon (C org ) and mitigate global warming by sequestering significant quantities of atmospheric CO 2 and storing sedimentary C org for long periods, although their C org burial and storage capacity may be affected by on-going sea level rise and human intervention. Geochemical data from published 210 Pb-dated sediment cores, collected from low-energy microtidal coastal wetlands in El Salvador (Jiquilisco Bay) and in Mexico (Salada Lagoon; Estero de Urias Lagoon; Sian Ka'an Biosphere Reserve) were revisited to assess temporal changes (within the last 100 years) of C org concentrations, storage and burial rates in tropical salt marshes under the influence of sea level rise and contrasting anthropization degree. Grain size distribution was used to identify hydrodynamic changes, and δ 13 C to distinguish terrigenous sediments from those accumulated under the influence of marine transgression. Although the accretion rate ranges in all sediment records were comparable, C org concentrations (0.2–30%), stocks (30–465 Mg ha −1 , by extrapolation to 1 m depth), and burial rates (3–378 g m −2 year −1 ) varied widely within and among the study areas. However, in most sites sea level rise decreased C org concentrations and stocks in sediments, but increased C org burial rates. Lower C org concentrations were attributed to the input of reworked marine particles, which contribute with a lower amount of C org than terrigenous sediments; whereas higher C org burial rates were driven by higher mass accumulation rates, influenced by increased flooding and human interventions in the surroundings. C org accumulation and long-term preservation in tropical salt marshes can be as high as in mangrove or temperate salt marsh areas and, besides the reduction of C org stocks by ongoing sea level rise, the disturbance of the long-term buried C org inventories might cause high CO 2 releases, for which they must be protected as a part of climate change mitigation efforts. [ABSTRACT FROM AUTHOR]