Factors driving sediment compositional change in the distal area of the Ria de Vigo (NW Spain): oceanographic processes vs. paleopollution.

We analyze potential Late Holocene metal contamination along a sediment core collected in the distal zone of Ria de Vigo (North Spain). Statistical treatment of the dataset based on a multiproxy approach enabled us to identify and disentangle factors influencing the depositional processes and the preservation of the records of this activity in the area over the last ≈3000 years BP. Some layers of the analyzed core have significant enrichment in Cu and a moderate enrichment in Ag, Mo, As, Sb, S, Zn, Ni, Sn, Cd, Cr, Co, Pb, and Li. The enrichment of these elements in some layers of this core may be related to mining activities that have taken place since classical times in the region. Successive phases of pollution were identified along the core KSGX24 related to the Late Bronze Age (≈3000-2450 years BP), Iron Age (≈2450-1850 years BP), Roman times (≈1850-1550 years BP), Middle Ages (≈1250-500 years BP), and industrial and modern (≈250-0 years BP) anthropic activities. The protection of the Cies Islands, the erosive and transport capacity of the rivers in the region, oscillations of the oceanographic and climatic regime, atmospheric contamination, and diagenetic sedimentary processes might have contributed to the accumulation and preservation of this record in the distal region of the Ria de Vigo. The studied core shows that the industrial and preindustrial anthropic impacts caused an environmental liability and contributed to the presence of moderate to heavy pollution of various metals in surface and subsurface sediment layers in the distal sector of the Ria de Vigo, which could be a hazard to biota.

Disentangling natural vs. anthropogenic induced environmental variability during the Holocene: Marambaia Cove, SW sector of the Sepetiba Bay (SE Brazil).

Multiproxy approach based on textural, mineralogical, geochemical, and microfaunal analyses on a 176-cm-long core (SP8) has been applied to reconstruct the Holocene paleoenvironmental changes and disentangling natural vs. anthropogenic variability in Marambaia Cove of the Sepetiba Bay (SE Brazil). Sepetiba Bay became a lagoonal system due to the evolution and development of the Marambaia barrier island during the Holocene and the presence of an extensive river basin. Elemental concentrations from pre-anthropogenic layers from the nearby SP7 core have been used to estimate the baseline elemental concentrations for this region and to determine metals enrichment factors (EF), pollution load index (PLI), and sediment pollution index (SPI). Record of the core SP8 provides compelling evidence of the lagoon evolution differentiating the effects of potentially toxic elements (PTEs) under natural vs. anthropic forcing in the last ~ 9.5 ka BP. The study area was probably part of coastal sand ridges between ≈ 9.5 and 7.8 ka BP (radiocarbon date). Events of wash over deposited allochthonous material and organic matter between ≈ 8.6 and 7.8 ka. Climatic event 8.2 ka BP, in which the South American Summer Monsoon was intensified in Brazil causing higher rainfall and moisture was scored by an anoxic event. Accumulation of organic matter resulted in oxygen depletion and even anoxia in the sediment activating biogeochemical processes that resulted in the retention of potentially toxic elements (PTEs). After ≈ 7.8 ka BP at the onset of the Holocene sea-level rise, a marine incursion flooded the Marambaia Cove area (previously exposed to subaerial conditions). Environmental conditions became favorable for the colonization of benthic foraminifera. The Foram Stress Index (FSI) and Exp(H'bc) indicate that the environmental conditions turned from bad to more favorable since ≈ 7.8 ka BP, with maximum health reached at ≈ 5 ka BP, during the mid-Holocene relative sea-level highstand. Since then, the sedimentological and ecological proxies suggest that the system evolved to an increasing degree of confinement. Since ≈ 1975 AD, a sharp increase of silting, Cd, Zn, and organic matter also induced by anthropic activities caused major changes in foraminiferal assemblages with a significant increase of Ammonia/Elphidium Index (AEI), EF, and SPI values and decreasing of FSI and Exp(H'bc) (ecological indicators) demonstrating an evolution from "moderately polluted" to "heavily polluted" environment (bad ecological conditions), under variable suboxic conditions. Thus, core SP8 illustrates the most remarkable event of anthropogenic forcing on the geochemistry of the sediments and associated pollution loads and its negative effect on benthic organisms.

Ecological quality status of the NE sector of the Guanabara Bay (Brazil): A case of living benthic foraminiferal resilience.

The ecological quality status of the NE region of the Guanabara Bay (SE Brazil), one of the most important Brazilian embayments, is evaluated. For this purpose, sediment samples from in the inner of the Guanabara Bay (GB) were collected and analyzed (grain-size, mineralogy, geochemistry and living foraminifera). In this study, it is hypothesized that the potentially toxic elements (PTEs) concentrations, in solution and associated with organic matter (OMPTEs, potential nutrient source), may represent two potential pathways to impact benthic foraminifers. A multiproxy approach applied to complex statistical analyses and ecological indexes shows that the study area is, in general, eutrophic (with high organic matter and low oxygen content), polluted by PTEs and oil. As a consequence, foraminifera are not abundant and their assemblages are poorly diversified and dominated by some stress-tolerant species (i.e., Ammonia tepida, Quinqueloculina seminula, Cribroelphidium excavatum). The results allow us to identify a set of species sensitive to eutrophication and OMPTEs. Factors such as the increase of organic matter contents and OMPTEs and, in particular of Zn, Cd and Pb, the oxygen depletion and the presence of oil, altogether contribute to a marked reduction in the abundance and diversity of foraminifera. Ammonia-Elphidium Index and the Foram Stress Index confirm that the NE zone of GB is, in general, "heavily polluted", with "poor ecological quality status" and experiences suboxic to anoxic conditions. In light of it, special attention from public authorities and policymakers is required in order to take immediate actions to enable its environmental recovery.

Historical sediment record and levels of PCBs in sediments and mangroves of Jobos Bay, Puerto Rico.

Polychlorinated biphenyls (PCBs) were quantified in 18 surface sediment samples, 1 sediment core, and several mangrove tissue samples collected in Jobos Bay, Puerto Rico in September 2013. Total PCBs in surface sediments ranged from 0.42 to 1232ngg-1 dw. Generally, higher levels were observed near-shore close to urban and industrial areas. The levels suggest significant pollution in Jobos Bay with respect to PCBs. Two-thirds of the sites were dominated by lighter PCB congeners (tri- to penta-chlorinated PCBs) while one-third had heavy PCB congeners (hexa- to octa-chlorinated PCBs) dominant. Total PCBs in a sediment core indicated levels fluctuating according to historical usage patterns. Total PCBs were measured in mangal leaves (14-747ngg-1 dw), roots (0.26-120ngg-1 dw), and seeds (16-93ngg-1 dw), suggesting bioaccumulation from sediments. This is the first report of a historical profile of PCBs in the study area and of PCB bioaccumulation in mangroves. This article provides new and useful information on PCBs in the Caribbean area of the GRULAC region.