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High amounts of mercury (Hg) can be released into the atmosphere from soil surfaces of legacy contaminated areas as gaseous elemental mercury (Hg0). The alluvial plain of the Isonzo River (NE Italy) suffered widespread Hg contamination due to the re-distribution of Hg-enriched material discharged by historical cinnabar mining at the Idrija mine (Slovenia), but an assessment of Hg0 releases from the soils of this area is still lacking. In this work, Hg0 fluxes at the soil-air interface were evaluated using a non-steady state flux chamber coupled with a real-time Hg0 analyser at 6 sites within the Isonzo River plain. Measurements were performed in summer, autumn, and winter both on bare and grass-covered soil plots at regular intervals during the diurnal period. Moreover, topsoils were analysed for organic matter content and Hg total concentration and speciation. Overall, Hg0 fluxes tracked the incident UV radiation during the sampling periods with daily averages significantly higher in summer (62.4 ± 14.5-800.2 ± 178.8 ng m-2 h-1) than autumn (15.2 ± 4.7-280.8 ± 75.6 ng m-2 h-1) and winter (16.9 ± 7.9-187.8 ± 62.7 ng m-2 h-1) due to higher irradiation and temperature, which favoured Hg reduction reactions. In summer and autumn significant correlations were observed between Hg0 fluxes and soil Hg content in soils (78-95% cinnabar), whereas this relationship was not observed in winter likely due to relatively low emissions found in morning measurements coupled with low temperatures. Finally, vegetation cover effectively reduced Hg0 releases in summer (∼9-68%) and autumn (∼41-78%), whereas the difference between fluxes from vegetated and bare soils was not evident during winter dormancy due to scarce soil shading. These results suggest the opportunity of more extended spatial monitoring of Hg0 fluxes particularly in the croplands covering most of the Isonzo River alluvial plain and where bare soils are frequently disturbed by agricultural practices and directly exposed to radiation.

Since arsenic (As) exposure is largely due to geochemical contamination, this study focused on the remediated area of Santana do Morro, a district of Santa Barbara, Minas Gerais, Brazil, which was previously contaminated with As due to gold mining. Total As concentrations in sediment, soil and plants were determined, next to As species, anionic arsenic compounds As(III), As(V), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), in plants samples. Total As concentrations in soil and sediments were slightly elevated (16-18 µg g -1 ) and most of the plants contained low levels of As (< 1 µg g -1 ). The exception was a native plant Eleocharis geniculata (L.) which contained elevated levels of As (4 µg g -1 ). The exposure of this plant to As under controlled conditions (hydroponics) indicated its possible tolerance to elevated As levels and suggesting its potential use in phytomonitoring of As-contaminated sites. This plant is able to metabolize arsenate to arsenite and contained MMA and DMA, both in its natural habitat and under controlled conditions.

For reason beyond the control of the authors or the editors, the article titled “Colloidal Organic Matter and Metal(loid)s in Coastal Waters (Gulf of Trieste, Northern Adriatic Sea)” by Katja Klun1 · Ingrid Falnoga2 · Darja Mazej2 · Primož Sket3 · Jadran Faganeli1 ( https://doi.org/10.1007/s10498-019-09359-6 ) was published in the regular issue Vol. 25 issue 5-6 instead of this special section, where it was originally scheduled to appear. Therefore, the full article is reprinted here.

Gaseous exchanges of mercury (Hg) at the water–air interface in contaminated sites strongly influence its fate in the environment. In this study, diurnal gaseous Hg exchanges were seasonally evaluated by means of a floating flux chamber in two freshwater environments impacted by anthropogenic sources of Hg, specifically historical mining activity (Solkan Reservoir, Slovenia) and the chlor-alkali industry (Torviscosa dockyard, Italy), and in a pristine site, Cavazzo Lake (Italy). The highest fluxes (21.88 ± 11.55 ng m−2 h−1) were observed at Solkan, coupled with high dissolved gaseous mercury (DGM) and dissolved Hg (THgD) concentrations. Conversely, low vertical mixing and saltwater intrusion at Torviscosa limited Hg mobility through the water column, with higher Hg concentrations in the deep layer near the contaminated sediments. Consequently, both DGM and THgD in surface water were generally lower at Torviscosa than at Solkan, resulting in lower fluxes (19.01 ± 12.65 ng m−2 h−1). However, at this site, evasion may also be limited by high atmospheric Hg levels related to dispersion of emissions from the nearby chlor-alkali plant. Surprisingly, comparable fluxes (15.56 ± 12.78 ng m−2 h−1) and Hg levels in water were observed at Cavazzo, suggesting a previously unidentified Hg input (atmospheric depositions or local geology). Overall, at all sites the fluxes were higher in the summer and correlated to incident UV radiation and water temperature due to enhanced photo production and diffusivity of DGM, the concentrations of which roughly followed the same seasonal trend.

Estuaries can be thought as a sedimentary trap leading to the accumulation of potentially toxic trace elements (PTEs) in sediments. However, biogeochemical processes at the sediment-water interface (SWI) may also be responsible for the release of dissolved PTEs and nutrients in the overlying water column affecting the water quality. The estuarine system of the Timavo River (Gulf of Trieste, northern Adriatic Sea) is a semi-closed aquatic environment where a long-lasting oxic-hypoxic interface along the water column occurred due to the scarce water circulation in the innermost sector. To prevent bloom-forming and potential production of toxins and off-flavours, artificial mixing has been provided with a bubble plume installation connected to pressurised air and built on the sediment surface aiming at reoxygenating the water column. The aim of this research was to evaluate the behaviour of PTEs (As, Cr, Hg, Fe, Mn, Ni, Pb, V) and nutrients (NO3, NO2, NH4 and SRP) along the water column and at the SWI before (June) and during (September) the activation of the forced aeration system. Water samples were collected at different depths along the water column, in situ benthic chamber experiments were performed at the SWI and short sediment cores were sampled to investigate both the sediment and porewater. Dissolved oxygen decreased along the water column, especially in June when hypoxia (2.29 mg/L) and reductive conditions (58 mV) were observed at the bottom resulting in increasing dissolved PTE and nutrient concentrations. Accordingly, a gradual oxygen depletion was observed in the benthic chamber testifying to intense organic matter remineralisation processes. Moreover, the highest concentrations of dissolved PTEs in porewater were restricted to the top of the sedimentary sequence, especially in June when hypoxic conditions may promote PTE and nutrient effluxes from the sediment to the water column.

The colloidal organic matter (COM) was isolated from the exudates of three cultured phytoplonkters, namely the chlophyte nanoflagellate Tetraselmis sp., the diatom Chaetoceros socialis and the dinoflagellate Prorocentrum minimum, from the Gulf of Trieste (northern Adriatic Sea). The isolation of COM was performed by ultrafiltration with molecular weight cut-off membranes of 5 kDa and final desalinisation by dialysis. The composition of the COM was characterised using C elemental analysis and 1H NMR spectroscopy and compared with COM isolated from a marine sample from the same area (Gulf of Trieste). By using 1H NMR spectroscopy, it was possible to semi-quantitatively determine the concentrations of the main biochemical constituents present in the COM samples. The results showed that the phytoplankton COM was predominantly composed of polysaccharides, with minor contributions from proteins and especially lipids. Therefore, the phytoplankton COM mainly contributes to the marine COM pool in the polysaccharide fraction and less in the protein and lipid fractions.

Large volumes of seawater were sampled in the Gulf of Trieste (northern Adriatic Sea) in order to study the interactions between colloidal organic matter (COM) and metal(loid)s (Me) in coastal waters. COM (> 5 kDa) was isolated by ultrafiltration and characterized using 1H NMR spectroscopy and elemental Corg. and Ntot. analyses. COM in the gulf represents about one quarter of the dissolved organic carbon (DOC), and according to 1H NMR analysis, it is composed of polysaccharides (30–45%), lipids (30–55%), proteins and carboxyl-rich alicyclic molecules (CRAM) (15–20%), and humics (

A new book explores how two river-dominated coastal estuaries are responding to the pressures of human expansion and climate change.

Since arsenic (As) exposure is largely due to geochemical contamination, this study focused on the remediated area of Santana do Morro, a district of Santa Bárbara, Minas Gerais, Brazil, which was previously contaminated with As due to gold mining. Total As concentrations in sediment, soil and plants were determined, next to As species, anionic arsenic compounds As(III), As(V), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), in plants samples. Total As concentrations in soil and sediments were slightly elevated (16-18 µg g-1) and most of the plants contained low levels of As (1 µg g-1). The exception was a native plant Eleocharis geniculata (L.) which contained elevated levels of As (4 µg g-1). The exposure of this plant to As under controlled conditions (hydroponics) indicated its possible tolerance to elevated As levels and suggesting its potential use in phytomonitoring of As-contaminated sites. This plant is able to metabolize arsenate to arsenite and contained MMA and DMA, both in its natural habitat and under controlled conditions.

We synthesized our present understanding of pelagic–benthic (P–B) interactions in the northern Adriatic Sea (NAS) and Chesapeake Bay (CB) in a comparative analysis that builds on a prior comparison. We focus on primary production (PP) in the water column and benthos, the sedimentation and horizontal transport of particlulate organic matter (POM), and biogeochemical responses of the benthic community to sedimentation. Phytoplankton net PP (NPP) remains higher in CB (five times that in NAS) and rates of benthic respiration appear greater in CB (three times that in NAS). A lower fraction of phytoplankton NPP plus riverine inputs of POM is deposited to sediments in the NAS (23%) compared to CB (83%). A high percentage of organic matter inputs are respired by plankton and exported in the NAS and CB, and benthic communities respired a similar percentage of POM (86% in the NAS, 92% in CB). Net release of regenerated N from the benthos (0.2–0.3 mol N m−2 year−1) is also similar in both systems. At 0.53 mol N m−2 year−1, rates of benthic denitrification are higher in CB than in the NAS (0.3 mol N m−2 year−1), and the NAS appears to bury similar fractions of deposited N and P (N: 23% in NAS, 19% in CB; P: 50% in NAS, 45% in CB). To address the impacts of future climate‐driven warming and acceleration of the water cycle, we recommend a return to sustained monitoring combined with numerical simulations to allow improved understanding and predictions of changes in P–B interactions.

The accumulation of contaminants and their potential mobility represent two of the main environmental issues facing coastal environments. Sediments often act as “reservoirs” of contaminants, including potentially toxic trace elements, but they can also be considered a secondary source of contamination due to remobilisation processes at the sediment-water interface which may affect the quality of the coastal water and aquatic biota. This research aims to provide a geochemical characterisation of the estuarine system of the Timavo/Reka River, focusing on the occurrence of trace elements in different environmental matrices with the purpose of highlighting potential critical conditions in terms of environmental quality. The surface sediments were found to be enriched in several trace elements especially in the innermost sector of the area. There, sulphate-reductive conditions in the bottom saltwater testify to potential anoxia at the sediment-water interface, driving trace element accumulation in the residual fraction of the sediments. However, Fe and Mn redox behaviour appears to play a crucial role in the recycling of dissolved trace elements in the water column. With the lone exception of the saltwater in the innermost sector, trace elements were found to be mainly associated with suspended particles due to oxidation and precipitation processes, whereas a common lithogenic origin was identified for Cr, Ni, and Co, which are significantly correlated both in the surface sediments and in the suspended particles.

Although the marginal seas represent only 7% of the total ocean area, the CO2 fluxes are intensive and important for the carbon budget, exposing to an intense process of anthropogenic ocean acidification (OA). A decline in pH, especially in the estuarine waters, results also from the eutrophication-induced acidification. The Adriatic Sea is currently a CO2 sink with an annual flux of approximately -1.2 to -3 mol C m-2 yr-1 which is twice as low compared to the net sink rates in the NW Mediterranean (-4 to -5 mol C m-2 yr-1). Based on the comparison of two winter cruises carried out in in the 25-year interval between 1983 and 2008, acidification rate of 0.003 pHT units yr−1 was estimated in the northern Adriatic which is similar to the Mediterranean open waters (with recent estimations of −0.0028 ± 0.0003 units pHT yr−1) and the surface coastal waters (-0.003 ± 0.001 and -0.0044 ± 0.00006 pHT units yr−1). The computed Revelle factor for the Adriatic Sea, with the value of about 10, indicates that the buffer capacity is rather high and that the waters should not be particularly exposed to acidification. Total alkalinity (TA) in the Adriatic (2.6-2.7 mM) is in the upper range of TA measured in the Mediterranean Sea because riverine inputs transport carbonates dissolved from the Alpine dolomites and karstic watersheds. The Adriatic Sea is the second sub-basin (319 Gmol yr-1), following the Aegean Sea (which receives the TA contribution from the Black Sea), that contribute to the riverine TA discharges into the Mediterranean Sea. About 60% of the TA inflow into the Adriatic Sea is attributed to the Po river discharge with TA of ~3 mM and TA decreases with increasing salinity. Saturation state indicates that the waters of the Adriatic are supersaturated with respect to calcite (ΩCa) and aragonite (ΩAr) throughout the year. However, saturation states are considerably lower in the bottom water layers, due to the prevalence of benthic remineralization processes in the stratification period. The seasonal changes of the chemical and environmental conditions and relatively small size of the Adriatic Sea area the microbial community composition, function (growth, enzymatic activity) and carbon and nitrogen biogeochemical cycles. Significant effects on calcifying organisms and phytoplankton are expected while the effects of possible OA on microbially-driven processes are not known yet.

Butyltin compound (BTC) contamination was evaluated in two north Adriatic marinas, San Rocco (Italy) and Lucija (Slovenia). BTC sedimentary concentrations (121 ± 46 and 352 ± 30 ng Sn g-1 in San Rocco and Lucija, respectively) evidenced the past use of antifouling paints, confirmed by the reduced tributyltin content (~ 46%) with respect to the sum of BTC. Elemental and organic carbon isotopic (δ13C) analyses of bulk sediments and its lipid and humic substances were performed in order to evaluate their role in BTC partitioning and preservation. The δ13C of sedimentary bulk and refractory organic matter suggested that diagenetic processes could play a role in the preservation or release of pollutants. No contamination was found in water collected from the benthic chamber and thus, fluxes at the sediment-water interface were not assessed, except for MBT efflux at Lucija (28.9 ng Sn m-2 day-1). Nevertheless, BTC concentrations in porewaters (up to 75 ng Sn l-1) and rather low sediment-porewater partitioning coefficients (Kd) with respect to the data reported in the literature would suggest a potential risk of the reintroduction of BTC into the water column at both sites: at Lucija, sedimentary contamination is high despite the greater Log Kd, whilst at San Rocco, the low BTC concentration is associated with a reduced sediment affinity.

The total activity of 210 Po was determined by alpha-spectrometry in various samples (matrices) collected in the Gulf of Trieste (northern Adriatic Sea) where fresh water inflows, especially from the Isonzo River in the northern part, affect water quality. Observed 210 Po levels were: 1) 0.56–3.75 mBq/L in the dissolved phase ( S transect in the gulf and sectioned to the depth of 20 cm) and 4) 239 (autumn) – 415 to 1800 (spring) Bq/kg (dw) in meso(zoo)plankton (>200 μm). In seawater and tributaries, up to 80% (mean 49%) of total 210 Po was found in particulate form. In sediments, slightly higher levels were encountered in the Isonzo prodelta and in the central (depocenter) part of the gulf. K D (L/kg) calculated between seawater and SPM, and seawater and sediment amounted to about 5 × 10 6 and 6 × 10 4 , respectively. Lower autumn 210 Po levels can be a consequence of biological dilution by higher mesozooplankton biomass in the autumn compared to spring. Plankton fractionation revealed in general the highest levels in the >200 μm mesoplankton fraction (239–1800 Bq/kg) followed by 50–200 μm (388–996 Bq/kg) and 20–50 μm (318–810 Bq/kg) microplankton fractions. Obtained data show higher 210 Po levels in all matrices analyzed in the Gulf of Trieste compared to other Adriatic (central Adriatic) and western Mediterranean areas. The 210 Po/ 210 Pb ratios in water, plankton and sediments were mostly below or around 1, while this ratio was much higher at higher trophic levels (up to about 50), reflecting a preferential bioaccumulation of 210 Po over 210 Pb. 210 Po accumulation between seawater and SPM and seawater and mesozooplankton amounted to 3.7 × 10 4 and 1.1 × 10 4 , respectively, similar to other Adriatic areas. Comparison of the relative importance of pelagic and benthic bioaccumulation pathways, excluding the filter feeder bivalves, suggests greater accumulation in pelagic-feeding species.

Estuaries are unique water systems and represent a vital link between land and sea. River transported contaminants, among which trace elements are of major concern, are subjected to a variety of physical, chemical and biogeochemical processes in the estuarine mixing zone. The Isonzo/Soča River is the main source of freshwater into the Gulf of Trieste (northern Adriatic Sea) and is known as the primary source of Hg due to long-term cinnabar (HgS) extraction from the Idrija mining district (Slovenia). Mercury distribution, cycling and speciation have been intensively studied at the Isonzo/Soča River mouth. Still, little information is currently available regarding other trace elements (As, Co, Cu, Cs, Cr, Fe, Ni, Mn, Pb and Zn). Indeed, this research aims to evaluate trace element occurrence and partitioning behaviour among suspended particulate matter (> 0.45 μm), colloidal material (0.45 μm – 10 kDa) and the truly dissolved fraction (< 10 kDa) at the mouth of the Isonzo/Soča River. Generally, trace elements are mainly associated with suspended particulate matter, which represents their main effective vehicle to coastal environments. In addition, dilution effects between riverine and marine particles are responsible for the decrease in particulate trace element concentrations along the water column. Mercury was notably present in winter in the freshwater, as expected under conditions of high river discharge. As opposed to other trace elements, particulate Mn was found to be high in the marine water, particularly in summer when high water temperatures could promote oxidation and precipitation processes. The Isonzo/Soča River mouth is characterised by a strong salinity gradient and geochemical processes appear to affect trace element partitioning behaviour. In this context, Fe, Mn and Cu were found to be mainly associated with the suspended particles and displayed the highest concentration in the colloidal material. Conversely, the truly dissolved fraction prevailed for As and Cs, which are often present in ionic dissolved forms in natural water systems.

Estuaries are transitional water systems where the hydrodynamic processes governing water circulation actively influence suspended particle transport and deposition. In the estuarine mixing zone, the strong physico-chemical gradients resulting from the interaction between river freshwater and seawater may affect the distribution, mobility and fate of several potentially toxic compounds, among which trace elements are of major concern. Knowledge regarding the partitioning behaviour of trace elements would provide essential scientific support for the environmental management of estuaries. In this study, trace element occurrence and phase partitioning among suspended particulate matter, colloidal material and the truly dissolved fraction were investigated in the main Italian and Slovenian estuarine environments of the Gulf of Trieste (northern Adriatic Sea). Further information about the water quality at the river mouths was provided and, in addition to the traditional evaluation of single chemical parameters, a multi-way principal component analysis was employed in order to depict disparities among sampling sites, water layers and seasonal conditions with the final aim of evaluating trace element phase partitioning. Results indicated that the suspended particulate matter acts as the main effective vehicle for Cu, Cr, Fe, Ni and Pb, and enhanced adsorption processes resulted in elevated partitioning coefficients, especially for Fe and Pb. Although disparities occurred between sampling sites and seasons, trace elements showing affinity for the solid phase appeared to be partially bound to the colloidal material. Conversely, As and Cs prevailed in the truly dissolved fraction, especially in seawater and showed scarce affinity for both the suspended particles and colloids.

The Gulf of Trieste (northern Adriatic Sea) is considered as an important “natural bioreactor” that can be stimulated to increase sedimentary methylmercury (MeHg) production by mobilizing its extensive mercury (Hg) pool. Sediment samples, collected in the southern pristine, less contaminated, part of the gulf, were amended with radioactive 197Hg in incubation experiments to determine the seasonal variation of Hg methylation potential at two depth layers (surface 0–2 cm and subsurface 2–4 cm). In parallel, Hg and MeHg were determined in the sediment solid phase and pore water. Total Hg and MeHg in the sediment solid phase ranged between 151 and 223 ng g −1 and between 0.17 and 0.68 ng g −1, and in pore water between 3.1 and 25.6 ng L −1 and between 0.03 and 6.16 ng L −1. Distribution coefficients (K d) suggested that Hg species are strongly bound to the sediment (log K d 3.86–4.87 and 1.67–3.39 for Hg and MeHg, respectively). Hg methylation potentials showed that MeHg is continuously produced, albeit not at a constant rate. The methylation potential in the sediment surface layer was higher and more variable in autumn, in parallel to higher bottom water temperature and O 2 content and sediment sulfate reduction, than in late spring and summer except in July in the presence of higher labile sedimentary organic matter (OM) level. Surface sediment showed rapid methylation of added traced Hg (0–0.66% day −1 Hg methylated). However, a significant fraction of the radiolabeled Hg remained available. In the subsurface sediment, methylation was lower (0–0.22% day −1 Hg methylated). Hg methylation potentials suggest that MeHg is continuously produced, albeit not at a constant rate, in the studied sediment of the Gulf of Trieste.

The Gulf of Trieste and adjacent Grado and Marano Lagoon (northern Adriatic Sea) are considered as an important “natural bioreactor” that can increase sedimentary methylmercury (MeHg) production by mobilizing the extensive mercury (Hg) pool as a result of historical (500 years) Hg mining and smelting activities in Idrija (NW Slovenia), the world’s second largest Hg mine. Even though the mine was definitely closed in 1995 the Soča/Isonzo River system still delivers about 1.5 t of Hg to the gulf annually and the MeHg is elevated in this marine environment. Research conducted by late M.E. Hines showed that Hg is readily methylated and demethylated in marine, lagoonary and freshwater sediments but the relative activities varied greatly with locality. Methylation activity increased from freshwater to the marine sites, conversely the highest demethylation was found in estuarine and lagoon sites. The methylation/demethylation ratios were consequently low in coastal sites but increased ib the gulf. Subsequent investigations in the southern, less contaminated (“pristine”) sediments of the gulf revealed that MeHg is also continuously produced especially in autumn in parallel with higher bottom water temperature and lower oxygen content. Sulphate reduction was found to control both processes. Hg methylation in sediments of coastal lagoon was controlled by rapid demethylation and the Hg bioavailability was affected by Hg adsorption and precipitation, In offshore marine sites, the sulphide produced by sulphate reduction lowers Hg methylation. Methylation of dissolved Hg, nearly 100% colloidally bonded, in the seawater column of the gulf was not detected (showing a pronounced Hg reduction potential) suggesting that sediments are the principal methylation site and the source of MeHg to the water column. It is likely that demethylation and reduction prevent the excessive accumulation of MeHg in the food webs of the Gulf of Trieste.

Estuaries represent a crucial link between land and sea where river fluxes of trace elements are subjected to a variety of physical and biogeochemical processes. The boundary conditions are extremely variable in the estuarine mixing zone affecting trace element speciation and their partitioning among different phases. The Isonzo/Soča River represents the main source of Hg in the Gulf of Trieste due to past mining activity at the Idrija mercury mine (Slovenia). The aim of this work is to evaluate trace element occurrence, size partitioning and mixing behaviour at the mouth of the Isonzo/Soča River. For this purpose, large volume water samples were collected from surface, mixing and bottom layers under various seasonal conditions. Size fractionation was performed using vacuum filtration and cross-flow ultrafiltration to isolate the suspended particulate matter (SPM) and the colloidal retentate solution, respectively, from the truly dissolved. Trace elements appear to be mainly associated with the SPM and dilution effects between riverine and marine particles are responsible for the decrease in their concentration along the water column. As expected, Hg was notably present during winter in the surface freshwater, in particular under conditions of elevated river discharge. On the contrary, Mn was found to be higher at the bottom, particularly during summer, as a consequence of oxidation processes followed by the precipitation of Mn oxy-hydroxides promoted by high water temperature. The strong physico-chemical gradients, especially in terms of salinity, are often responsible for the non-conservative behaviour of several trace elements. Iron, Mn and Cu displayed a non-conservative behaviour during mixing and simultaneously showed the highest content of colloidal material. On the contrary, conservative behaviour was found for As and Cs which are often present under ionic dissolved forms in natural water systems

Large volumes of seawater were sampled monthly from December 2011 to October 2012 in the southeastern part of the Gulf of Trieste (northern Adriatic Sea) in order to study the seasonal changes of colloidal organic matter (COM) concentrations, its origin and composition. Isolation of COM was performed by ultrafiltration with molecular weight cut-off membranes of 5 kDa and final desalinization by dialysis. COM was characterized using 1H NMR and FT-IR spectroscopy, elemental C and N and 13C and 15N isotope analyses and high-pressure size exclusion chromatography. COM represents about 1/4 of dissolved organic carbon (DOC) and appears to be mainly of marine origin. COM is mainly composed of polysaccharides, lipids, proteins and humics. FT-IR analysis indicated the presence of OH (carbohydrates and lipids), COOH (proteins and lipids) and NH (proteins) containing functional groups. Using the NMR technique, it was possible to semiquantitatively determine variations of four main biochemical constituents present in...

Deposition of riverine suspended solids affects operations in ports located in the proximity of river mouths. The Rižana River is the main source of riverine solids in the shallow Bay of Koper (Gulf of Trieste, northern Adriatic Sea). The mean discharge increases rapidly in relation to high precipitation, typical of spring and autumn. During such events, the runoff leads to torrential river flow with high concentration of suspended solids which are consequently deposited in the port zone. Turbidity (NTU) measurements were performed during 2011–2013 in the Rižana and Badasevica Rivers and in the inner part of the bay influenced by fresh water inflow. In parallel, the concentrations of total suspended solids (TSS) and suspended organic matter (SOM) were measured gravimetrically, the latter after combustion, and their grain size distributions were determined using a laser granulometer. The maximum turbidity values in the bay were found in the sea surface layer during the river flood. The linear regression model between TSS and turbidity (NTU) TSS = 1.01 × NTU + 0.91 showed strong positive correlation. The regression analysis between turbidity and SOM also showed strong correlation with a regression equation SOM = 0.12 × NTU + 0.85. The impact of SOM on measurements was hypothesized by the rather poor model fit of the regression analysis between TSS and river discharge, which is mainly related to high SOM variations. The grain size spectra of riverine and nearshore surface TSS in the proximity of the river mouth were skewed and sorted with the mode size mostly around 10 μm. Considering the TSS mass in the sea surface layer, the yearly TSS input into the bay is estimated to be ~18 × 103 t. Using the average TSS concentration in the Rižana River and the average Rižana River discharge, the yearly input would be ~2 × 103 t. The discrepancy between both calculated inputs is probably related to the TSS input during high river discharge which occurs in short periods. A maximum deposition rate of 80 g m2 day−1 is mostly restricted to the second port basin. Less than 50 % of the introduced TSS settles within the second port basin during mean river flow conditions. The regression model was found to be a useful tool to estimate TSS and SOM concentrations from turbidity data in rivers and the coastal sea, thus providing an evaluation of riverine TSS and SOM input and deposition into the small bay, which in turn affects local port activities.

Since the environmental levels of selenium (Se) can moderate the bioaccumulation and toxicity of mercury (Hg) in marine organisms, their interactions were studied in seawater, sediments, plankton and the benthic (Bull ray Pteromylaeus bovinus, Eagle ray Myliobatis aquila) and the pelagic (Pelagic stingray Dasyiatis violacea) rays, as apex predators in the Gulf of Trieste (Northern Adriatic Sea). Male and female rays showed no difference in the Se contents in muscle tissue. Pelagic species contained higher Se levels in muscle but slightly lower levels in the livers of both genders. The Hg/Se ratios in seawater dissolved and colloidal fractions, plankton and sediment were

Metabolism and carbon, oxygen, and nutrient fluxes (DIC, DOC, DO2, NO2−, NO3−, NH4+, PO43− and SiO44−) were studied during three surveys at two sites (VN1 and VN3) located at a fish farm at the Marano and Grado Lagoon (northern Adriatic Sea), using an in situ benthic chamber. Field experiments were conducted in July and October 2015 and March 2016 at a depth of approximately 2 m along the main channels of the fish farm. Water samples were collected by a scuba diver every 2 h in order to investigate daily fluxes of solutes across the sediment-water interface (SWI). Regarding the solid phase, Corg/Ntot and Corg/Porg molar ratios suggested an autochthonous marine origin of the organic matter and a minor preservation of P in the sediments, respectively; high values of sulphur (Stot) were also encountered (0.8–2%). The conditions at VN3 were mostly anoxic with high NH4+ levels (30–1027 μM) and the absence of NO3−. Substantial daily patterns of all solutes occurred especially in autumn and winter. On the contrary, fluxes at VN1 were less pronounced. Usually, inverse correlations appeared between dissolved O2 and DIC trends, but in our system this was observed only at VN3 in autumn and accomplished by a parallel increase in NH4+, PO43− and SiO44− during intense nutrient regeneration. These results are significantly different than those reported for open lagoon environments, where nutrient regeneration at the SWI and in surface sediments is the primary source of nutrients available for assimilation processes, especially during the warmer period of the year when the natural nutrient input by fresh water inflows is limited. Due to the importance of this site for aquaculture, biodiversity and ecosystem services, useful suggestions have been provided from this study in order to improve the quality of this unique aquatic system.

Partitioning of potentially harmful elements (PHEs) and their speciation in estuarine environments strongly depends on the physico-chemical boundary conditions, especially in terms of salinity gradient. Due to their high abundance in aquatic environments, colloidal fraction is known to play a central role in the regulation of PHEs occurrence, mobility and speciation. Aquatic colloids represent important intermediaries in the removal processes, such as coagulation, of PHEs and, consequently, they are one of the most important factors able to regulate the fate of PHEs in the environment. The present work aims to report the results of PHEs partitioning between particulate (> 0.45 µm), colloidal (10 kDa - 0.45 µm) and dissolved (< 10 kDa) fractions in different estuarine waters of the Gulf of Trieste (Northern Adriatic Sea). In order to achieve these objectives, water samples from surficial and bottom layers of the water column were collected along Italian and Slovenian river mouths. Several CTD (Hydrolab H2O Multiprobe with a 0.10 dbar pressure step) vertical profiles of salinity, temperature and turbidity were performed in order to identify the water masses before sampling. Generally, the surficial water samples were collected at variable depths, according to the salinity trend and along the salinity gradient, whereas the bottom water samples were representative of the marine water intrusion. In addition, the main physico-chemical parameters (temperature, pH, redox potential (Eh), dissolved oxygen and electrical conductivity (EC)) were measured in situ through portable probes (pH-meter PH25 and Conductivity-meter CM35+ by Crison Instruments) submersed in a bucket. Samples for PHEs detection were filtered through 0.45 µm filters (Millipore HA, Ø 47 mm) in order to isolate the particulate fraction which was acid-digested through a total dissolution in a closed microwave system (Multiwave PRO, Anton Paar). Subsequently, the filtrate samples were ultrafiltered through 10 kDa membranes (Vivaflow 200, Sartorius). The ultrafiltration was performed in recirculation mode using a concentration factor equal to about 60 in order to collect large amounts of colloids. All sample aliquots were analysed for PHEs determination by means of Inductively Coupled Plasma Mass Spectrometry (ICP-MS, Nexion 350x Perkin Elmer), with the only exception of Hg analyses which was also performed through Cold Vapor Atomic Fluorescence Spectrometry (CV-AFS, Mercur Analytic Jena).

One of the main environmental issues affecting coastal marine environments is the accumulation of contaminants in sediments and their potential mobility. In situ benthic chamber experiments were conducted at two tourist ports (marinas) located in the Gulf of Trieste, one in Slovenia and one in Italy. The aim was to understand if and where recycling at the sediment-water interface (SWI) may affect metal(loid)s. Short sediment cores were also collected near the chamber to investigate the solid (sediments) and dissolved phases (porewaters). Both diffusive and benthic fluxes were estimated to elucidate the release of metal(loid)s at the SWI. Total element concentrations and their labile fractions were determined in sediments to quantify their potential mobility. The total element contents were found to be two orders of magnitude higher in the Italian marina than in the Slovenian one, especially for Hg (up to 1000 mg kg−1), whereas the labile fraction was scarce or null. The opposite occurred in the Slovenian marina. Metal(loid)s in porewaters showed a clear diagenetic sequence and a close dependence upon the suboxic/anoxic conditions of sediments. The results suggest that although the sediments of the Italian marina exhibit the highest total metal(loid) concentration, these elements are scarcely remobilisable. Conversely, in the Slovenian marina, sediments seem to be comparatively more prone to release metal(loid)s at the SWI.

The Marano and Grado Lagoon is well known for being contaminated by mercury (Hg) from the Idrija mine (Slovenia) and the decommissioned chlor-alkali plant of Torviscosa (Italy). Experimental activities were conducted in a local fish farm to understand Hg cycling at the sediment–water interface. Both diffusive and benthic fluxes were estimated in terms of chemical and physical features. Mercury concentration in sediments (up to 6.81 μg/g) showed a slight variability with depth, whereas the highest methylmercury (MeHg) values (up to 10 ng/g) were detected in the first centimetres. MeHg seems to be produced and stored in the 2–3 cm below the sediment–water interface, where sulphate reducing bacteria activity occurs and hypoxic–anoxic conditions become persistent for days. DMeHg in porewaters varied seasonally (from 0.1 and 17% of dissolved Hg (DHg)) with the highest concentrations in summer. DHg diffusive effluxes higher (up to 444 ng/m 2 /day) than those reported in the open lagoon (~ 95 ng/m 2 /day), whereas DMeHg showed influxes in the fish farm (up to − 156 ng/m 2 /day). The diurnal DHg and DMeHg benthic fluxes were found to be higher than the highest summer values previously reported for the natural lagoon environment. Bottom sediments, especially in anoxic conditions, seem to be a significant source of MeHg in the water column where it eventually accumulates. However, net fluxes considering the daily trend of DHg and DMeHg, indicated possible DMeHg degradation processes. Enhancing water dynamics in the fish farm could mitigate environmental conditions suitable for Hg methylation.

The origin of organic matter in recent anoxic sediments of the alpine Lake Bled (NW Slovenia) was determined by analyzing the carbon isotope composition of lipid biomarkers, i.e. alkanes, alcohols, sterols and fatty acids, busing compound specific, carbon isotope analysis. The results indicate that, although biomarker analysis indicated mostly plankton and terrestrial sources for lipids, an important part of sedimentary lipids, especially sterols, are autochthonous, of anaerobic microbial (methanotrophic) origin. Marked differences were observed in δ13C values of lipid biomarkers in settling particles collected 2 m above the bottom, and in δ13C values determined in surface sediment. These results indicate that even some compounds found in both particulate organic matter and sediments are the same in terms of chemical structures, their sources can be different and thus, isotopic composition should be used as a complementary tool for source identification.