Geochemistry of recent aragonite-rich sediments in Mediterranean karstic marine lakes: Trace elements as pollution and palaeoredox proxies and indicators of authigenic mineral formation

Decoupling Sources of Anthropogenic Influences on Sediments of the Visovac Lake (Krka National Park, Croatia) Using Multiparametric Approach

Historical changes of sediment characteristics and levels of inorganic and organic contaminants were studied in dated sediment cores from the Visovac Lake, situated in the Krka National Park, Croatia, to identify the main sources of anthropogenic pressures on this highly protected system. Depth distributions of lithogenic elements showed a steady decrease of terrigenous inputs due to the reduction in agricultural activities in the area, which was particularly pronounced during the 1991-1995 war in Croatia. Vertical and longitudinal distributions of Cd and Zn indicated that they are predominately of anthropogenic origin. The historical profiles of these toxic metals coincide well with the recorded production of metal industry in the upper reach of the Krka River with a sharp decrease reflecting the interruption by the war and slow recovery afterwards. By contrast, the recovery of the tourist industry in Krka NP after the war was accompanied by increasing contamination by elements characteristic of boat and car traffic (Sn, Cu, Pb) as well as oil pollution. The contamination with polycyclic aromatic hydrocarbons and polychlorinated biphenyls was only moderate. Although levels of metallic and organic contamination can be considered relatively low, the observed shift from industrial to tourism-related sources indicated that touristic activities should also be regarded as a possible threat for this vulnerable karst aquatic ecosystem.

Evaluation of the Adriatic Sea pollution using mesozooplankton as an environmental indicator

The Adriatic Sea is an enclosed basin threatened by marine pollution due to its hydrographic features and anthropogenic pressure. Although zooplankton has been worldwide regarded as an immediate warning signal of contamination, limited information is available on the contamination of these organisms at the Adriatic level. Hence, this study provides comprehensive data on the presence and levels of multiple pollutants in zooplankton collected from 46 locations. With regards to legacy contaminants, both PCB and DDT levels have declined since the 1980s. Specifically, most samples were characterized by low DDT contamination (average of 3 ± 2.7 ng g- 1 dry weight) and only few of these accumulated levels of concern for what concerns PCB, pointing out possible hotspots of contamination in the central-eastern Adriatic Sea. As regards metal(loid)s, the Metal Pollution Index identified areas of concern in the north Adriatic Sea (Gulf of Venice) with high levels of Co, Cu, Hg, Cr and Pb; in the Central Adriatic Sea (Tremiti islands) with high levels of Co, Ni, Hg, Cr and Pb; in the Southern Adriatic Sea (Taranto and offshore Corfu), with high levels of most metal(loid)s, especially Cr, Ni and Zn. Certain metal(loid)s (e.g. Cd, Pb and Hg) have declined over time and most of them are lower than well-known contaminated worldwide marine ecosystems. Only Cu appears to be particularly high in the Mediterranean zooplankton. Overall, this work suggests a general improvement of the status of contamination of the Adriatic Sea.

Size-dependent distribution of metal(loid)s in recent marine sediments of the Adriatic sea

This paper investigates occurrence of metal(loid)s, and size-dependent changes in their concentration in recent marine sediments from coastal and open-sea environments in the eastern Adriatic. Size fractionation of sediments was performed after removal of organic matter (OM), and the individual fractions, comprising particles below 8 μm, 4 μm, 2 μm, 1 μm and 0.45 μm, were analysed using HR ICP-MS. The concentrations of most elements increased with decreasing particle size, as a result of accumulation of clay minerals and Fe and Mn (oxyhydr)oxides. A decrease in concentrations was observed for Ba, Sr, Ti and U, due to lowering of the carbonate content and presence in the coarse-grained and heavy mineral fraction. The highest element concentrations were determined in the fraction comprising particles below 1 μm. Occasionally, depending on the sedimentological environment and/or the element in question, the peak concentrations occurred in the <2 μm or <0.45 μm fraction. The lowest size-dependent enrichment was observed for elements associated with aluminosilicates (Al, Be, Cs, Co, Fe, K, Li, Rb). A different size-dependent behaviour of the elements was observed between deep-sea areas and shallow environments under greater coastal influence, mainly due to differences in sediment sorting, and between the northern and central vs. southern Adriatic due to the different catchment geologies. The Fe and Mn (oxyhydr)oxides, abundant in the deep-sea sediments, played an important role in the geochemical cycle of As, Cd, Co, Mo, Sb and V.

Origin and history of trace elements accumulation in recent Mediterranean sediments under heavy human impact. A case study of the Boka Kotorska Bay (Southeast Adriatic Sea)

The history of metal pollution in the semi-enclosed and human-influenced marine system of the Boka Kotorska Bay (Southern Adriatic) was studied considering geological composition of the surrounding catchment, the sedimentation rate and the mineralogical and early diagenetic processes in the recent sediments. The determination of background concentrations of metals, undertaken for the first time in this environment, proved to be particularly important for Ni and Cr, which are naturally enriched in the sediments of the southern Adriatic. The results showed widespread moderate contamination with Pb and Sn since the 1970s, while the upper layers of sediments near shipyards, marinas and urban areas were more contaminated with Sn, Cu, Pb, Zn, Cd, As, Sb and Mo. The transport of material through the narrow straits separating different parts of Boka Kotorska Bay resulted in a different geochemical composition of the smaller bays and a limited distribution of contaminated sediments from local sources.

Occurrence and Distribution of Technology-Critical Elements in Recent Freshwater and Marine Pristine Lake Sediments in Croatia: A Case Study

The occurrence and vertical distribution of ten technology critical elements (TCEs) (Li, Nb, Sc, Ga, Y, La, Sb, Ge, Te, and W) were studied in sediment cores collected from remote freshwater and marine lakes (Plitvice, Visovac and Mir Lakes) in three protected areas of Croatia. These environmental archives were used to assess natural TCE levels in lake sediments and temporal trends in historical anthropogenic atmospheric deposition. TCE was determined after complete sediment digestion using high-resolution inductively coupled plasma mass spectrometry (HR ICP-MS). The measured TCE concentrations spanned a wide range, which can be attributed to the varying input of terrigenous material into the studied lake systems. All obtained TCE concentrations were close to natural conditions and therefore could be used as a reference for other equivalent sediment systems in the coming years. The evaluation of anthropogenic influence on TCE concentrations showed a slight anthropogenic enrichment with Sb and Te in the upper sediment layers of some lakes (Plitvice and Mir Lakes), indicating a widespread atmospheric deposition, which, however, cannot be related to the recent increase in the use of TCE in modern technology.

Spatial distribution of pesticides, organochlorine compounds, PBDEs, and metals in surface marine sediments from Cartagena Bay, Colombia

Cartagena Bay is an estuarine system located in the Caribbean Sea (Colombia, South America), that receives fresh water from Canal del Dique, which is connected to the Magdalena River, the most important river of Colombia, with some of the most prominent Colombian cities located in its watershed, which has a high sediment yield. An analysis of persistent organic pollutants and heavy metals was carried out on marine sediments from Cartagena Bay. Cartagena Bay sediments deployed the occurrence of total levels of pesticides (thiocarbamates, bromacil, triazines, organochlorines, and organophosphorus), polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs), in sediments ranging from 0.83-33.67 ng/g dry-weight, 0.05-0.34 ng/g dry-weight, and 0.06-19.58 ng/g dry-weight, respectively. Their concentrations were lower than those reported in NOAA Screening Quick Reference Tables. DDTs and PCBs are banned organochlorine compounds, since, even at low levels, their presence in sediments represents a threat to aquatic organisms and, therefore, to human health through the trophic chain. Sediments showed high concentrations of strontium (50-959.6 mg/kg). All metals evaluated in the marine sediments were found in the S6 sampling point; this was near tannery and hydrocarbon industries (Pb 37.1 mg/kg, Cr 137.2 mg/kg, Cd 1.7 mg/kg, Cu 64.4 mg/kg, As 13.1 mg/kg, Sr 318.9 mg/kg); these results exceeded the accepted values of threshold effect levels (TEL) used as an indicator of their potential risk on marine life.

Simultaneous analysis of butyltins and total tin in sediments as a tool for the assessment of tributyltin behaviour, long-term persistence and historical contamination in the coastal environment

This study presents a new approach for the investigation of tributyltin (TBT) behaviour and fate in the marine environment. The approach is based on a simultaneous analysis of butyltins (BuTs) and total Sn in sediments, thus enabling an assessment of long-term persistence and historical input of TBT. The study also presents first evaluation of the extent to which the TBT-antifouling paints contribute to the contamination of coastal environments with inorganic Sn; it was demonstrated that the inorganic Sn in the investigated areas primarily originates from TBT degradation. The study was conducted by analyzing BuTs and total Sn in sediments from 34 locations along the Croatian Adriatic coast. The results revealed that 85% of the locations were contaminated with both BuTs and inorganic Sn. The share of ƩBuTs/total Sn was low (<10%) even in sediments with low TBT degradation efficiency (TBT/ƩBuTs >40%), demonstrating that only small portion of TBT introduced into the water column reached the sediment before being degraded. This means that recent TBT input into the marine environment may be at least 10 times higher than the amount estimated if only BuTs levels in sediments are considered. It was also demonstrated that TBT concentration in sediments with TOC <1% is not a good indicator of the overall pollution level, even if TBT/TOC approach is used in pollution assessment. Finally, in situ investigation showed that resuspension of contaminated sediments leads to significant release of MBT and DBT into the water column, whereas TBT mainly remains in sediment.

Size-related mineralogical and surface physicochemical properties of the mineral particles from the recent sediments of the Eastern Adriatic Sea

The mineral composition and surface physico-chemical properties, i.e., specific surface area (SSA), cation exchange capacity (CEC), and surface charge of recent sediments and their submicron mineral fractions from different sedimentological environments of the Eastern Adriatic were investigated. The influence of organic matter on these properties was also investigated. It was shown that illite and mixed-layered clay minerals (MLCM) were ubiquitous and showed no size-related preferences while the occurrence of smectites, chlorites, and kaolinites varied. The smectites content increased and the chlorites decreased slightly with decreasing particle size. The sediments from the carbonate-rich environment contained no smectites or chlorites and had the highest kaolinite content. For the first time, in the recent sediments of the Adriatic Sea the poorly- and the well-crystallised kaolinite (Kl and Kl_D) were distinguished. While Kl predominates in the submicron-sized fraction, Kl_D occurred only in micron-sized fractions. Authigenic aragonite of submicron-sized was determined in a distinct environment of the semi-enclosed marine lake. The differences in mineral composition and particle size of sediments and their separated fractions were reflected in a wide range of the SSA and CEC values obtained. The highest values of SSA and CEC were determined in the phyllosilicates-rich submicron-sized fractions range, 109 m²g^-1 and 87.4 cmol₊kg^-1, respectively. The submicron-sized fraction from aragonite-rich marine lake showed the lowest values of SSA (56.4 m²g^-1) and CEC (38.8 cmol₊kg^-1), which are still unexpectedly high for carbonate-rich environments. The removal of organic matter resulted in a significant increase in SSA and CEC, up to 150% and 76%, respectively.