Environmental Assessment of Trace Metals in San Simon Bay Sediments (NW Iberian Peninsula)

Impact of sediment mobilization on trace elements release in Galician Rías (NW Iberian Peninsula): insights into aquaculture

In the latest years, the concentration levels of certain metals and metalloids in the sediments of the Galician Rías have shown an increasing trend (e.g., As, Zn, Cu, Pb, Hg). These areas are also characterized by their richness in nutrients and their great aquaculture or mariculture activity, with the presence of more than 3500 mussel rafts in the Rías Baixas. The inner areas of the Galician Rías are subjected to activities that resuspend the sediment such as high levels of maritime traffic and dredging or cleaning operations. It is likely that a transfer of these elements to the water column happens during the resuspension of sediments caused by natural events or anthropogenic activities. In this study, selected samples of surface sediments of the Ría de Pontevedra (NW Spain) were subjected to a procedure of aerobic oxidation to determine the concentration of some elements (Fe, Mn, Cu, Cr, Pb, Hg, and Zn) released from the sediment to the aqueous phase. The experiment was carried out within 5 days. Measurements of pH and total concentration were taken both in water and sediment samples. Furthermore, speciation of trace elements was carried out in the sediment samples. Trace element concentrations were lower in the sediments during aerobic oxidation, being released to the aqueous phase. From an environmental point of view, Cu was the only trace element released in quantities that may be toxic for the organisms in the area. This problem of sediment oxidation related to dredging activities or natural storm conditions should be considered in environmental impact studies and transferred to stakeholders.

Metal bioavailability, bioaccumulation, and toxicity assessment through sediment and edible biota from intertidal regions of the Aghanashini Estuary, India

The sediment cores and edible biota from the intertidal regions of the Aghanashini Estuary were studied for the assessment of metal toxicity. The estuarine sediments received natural input of metals through the weathering of Dharwar and peninsular gneisses, and laterites. The sediments were enriched in Fe, Mn, Zn, Cu, Co and Ni than the upper crustal value. Also, the concentration of Fe, Zn, Cu, Co and Ni was more in the Aghanashini Estuary than other estuaries around the world. The Enrichment Factor (EF) revealed enrichment of Zn, Cu, Co and Ni in sediments, while the Geo-accumulation Index (Igeo) exhibited unpolluted-moderately-strongly polluted class of Fe, Zn, Cu, Co and Ni. The enrichment and pollution of metals in sediments was due to anthropogenic sources (domestic sewage, aquaculture and agricultural discharge) in the estuary. The presence of metals at a high concentration in the residual fraction and at a significant proportion in the bioavailable fractions construed both natural and anthropogenic sources of metal, and their bioavailability in the estuary. The physico-chemical factors (ionic composition, H+ ions, redox potential, and microbial activity) regulated the adsorption and desorption of metals in sediments. The Screening Quick Reference Table (SQUIRT) revealed level of bioavailable Mn and Co higher than the Apparent Effects Threshold (AET) and thus, indicated adverse toxic effects on biota. The Risk Assessment Code (RAC) indicated medium-high-very high risk of Mn, Zn, Co, Cu and Ni to biota. Also, the concentration of Fe, Mn, Zn, Cu and Ni in biota was in excess of permissible limit which pointed to their toxicity to biota and their consumers. The Target Hazard Quotient (THQ) value > 1, and Hazard Index (HI) value > 10 revealed risk of metal toxicity to humans.

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.

Editorial for Special Issue “Elemental Concentration and Pollution in Soil, Water, and Sediment”

Certain elements are essential to the growth and health of living organisms with specific biochemical functions in their metabolic processes [...]

Spatial Variability of Metals in Coastal Sediments of Ełckie Lake (Poland)

This study aimed to determine the content and spatial distribution of metals (Ca, Mg, Fe, Na, K, Mn, Zn, Cr, Cu, Pb, Co) in sediments in the coastal zone of Ełckie Lake located in the area of "Green Lungs of Poland" in the north-eastern part of the country, depending on the land use (urban area, agricultural and forest area, and beaches). The concentration of metals was determined using atomic absorption spectrometry. The average contents of major elements in 28 sediment samples occurred in the following order: Ca > Mg > Fe > Na > K > Mn. The order of these elements in the coastal sediments located within the different parts of the catchment was identical. These elements may originate from natural sources such as the Earth’s crust, soil, and wind-blown dust from unpaved roads. The average contents of potentially toxic elements (PTEs) in the sediments were as follows: Cr > Zn > Pb > Cu > Co in agricultural and forest areas and beaches (the exception was Cu for beach B, which occurred at the end of the series). A different pattern occurred in urbanized areas: Zn > Cr > Cu > Pb > Co. The spatial distribution of heavy metals in the sediments indicated the highest contents in the shoreline adjacent to the urbanized part of the catchment. The primary sources of metals in sediment are transportation, coal burning, sanitary sewage from unsewered developments on the lakeshore, and storm runoff from roads. This was confirmed by positive correlations of Zn with Cu (r = 0.58), Pb (r = 0.90), Fe (r = 0.40). No correlations between the studied metals and organic matter were found, which may indicate its insignificant influence on metal content in the sediments. Pearson correlation coefficients also showed no relationship between sediment pH and the presence of metals. Factor analysis (FA) indicated that lithogenic (geogenic) and anthropogenic factors have almost equal shares in the distribution of most of the metals studied. The analysis of variance (ANOVA) showed that the average contents of Zn, Cu, Co, and Na in the sediments from urbanized areas are statistically significantly higher than the sediments from other areas (rural/forest, beaches).