Large-scale evaluation of deposition, bioavailability and ecological risks of the potentially toxic metals in the sediment cores of the hotspot coral reef ecosystems (Persian Gulf, Iran)

Coral reefs of the Persian Gulf are vulnerable to the potentially toxic metals (PTMs) accumulated in the ambient sediments. Nonetheless, few studies have investigated the PTMs pollution and risk in the hotspot coral ecosystems of the Persian Gulf at a large-scale. Hereupon, this study focused on the PTMs contamination, their potential ecological risks, historical depositions, geochemical controls and the plausible pollution sources in the core sediments (0-40 cm) collected from the ten coral ecosystems of the Persian Gulf, Iran. Both total and fraction analysis indicated considerable metal pollution levels. Contamination was steadily decreasing towards the bottom of the sediment core, revealing the impact of a recent anthropogenic input. High metal association with the exchangeable and other mobile fractions was observed, indicating their high bioavailability. Of all the elements analyzed, toxic metals Cd, Hg and As exhibited the highest potential ecological risk (RI). Site rank index (SRI), modified degree of contamination (_mCd), and contamination severity index (CSI) based approaches identified stations ST5, ST9 and ST10 as the most contaminated sites of the study area. The same stations were also found to possess considerable ecological risk. Principal component analysis (PCA) revealed that the stations located in the zone of the highest anthropogenic impact contain pollution sources for all the metals analyzed, whereas areas with low anthropogenic activity are mainly affected by the river runoff and urban emissions.

Winter arsenic pollution in 10 forest ecosystems in the mountainous border regions of the Czech Republic

Arsenic (As) concentrations and deposition fluxes were measured in snow and rime at 10 mountain-top sites near the borders between the Czech Republic and Austria, Germany, Poland, and Slovakia during three consecutive winter seasons (2009-2011). Our study was performed at a time following several decades of sharply decreasing regional atmospheric pollution and following the 2006 implementation of stricter air quality standards across Europe. Our objective was to compare vertical and horizontal depositions of soluble and insoluble As forms throughout the Czech Republic and define a recent Central European As pollution gradient. Arsenic soluble in weak nitric acid contributed 83 to 85% to the total As deposition, with the remaining 17-15% bound to stable particulate forms. The highest As deposition rates were recorded in the eastern Czech Republic near the borders with Poland and Slovakia. Complementary hydrochemical monitoring in four mountain-slope catchments situated near selected main study sites revealed a further decrease in open-area As deposition by the end of 2018 in the east of the country. In contrast, spruce canopy throughfall flux did not change significantly between 2009-2011 and 2016-2018. The site-specific relative roles of coal-burning-derived and ore-smelting-derived atmospheric As are discussed.