Sediment resuspension during vessel manoeuvres in port areas: evidence from field observations

Purpose: The increase in maritime traffic in the Bay of Koper (Gulf of Trieste, northern Adriatic Sea) has been made possible given the increase in the local port capacity and logistics, which, in turn, means an increase in the number of arrivals of larger vessels (which were the original motive for port expansion); this poses a potential risk for coastal environments due to the impact of the resuspension of bottom sediment which affects the physical and chemical characteristics of the water column. The aim of this work was to assess the magnitude of these perturbative events.Materials and methodsTurbidity (NTU) measurements were made using a CTD multiprobe during a vessel manoeuvre in the port navigational canal and in the entire Bay of Koper. In the highest turbidity zone, samples were collected from the surface water layer (0.5 m), at a depth of 6.0 m and 12.0 m. Total suspended solids (TSS) and suspended organic matter (SOM) were measured gravimetrically. TSS grain-size distribution was determined using a laser granulometer.Results and discussionThe effect of the vessel manoeuvre was evident on turbidity with a maximum value of 137 NTU (TSS = similar to 139 mg l(-1)) and a sampled concentration of TSS of 37 mg l(-1) (bottom layer) in the water column immediately after the ship manoeuvre. Grain-size analysis shows a spectrum of particles with a mode size between 22 and 88 mu m (medium silt and very fine sand, respectively). The estimated resuspension mass of total suspended solids (TSS) was similar to 109 t in the restricted manoeuvre area extending about similar to 736 x 493 m and with an average depth of 15 m.ConclusionsThe results demonstrated the significant impact of vessel manoeuvres on the measured parameters, the impact of which cannot be underestimated in terms of marine environmental protection and maritime traffic safety. Moreover, this impact is expected to increase in the near future

Ensemble weather forecast post-processing with a flexible probabilistic neural network approach

Ensemble forecast post-processing is a necessary step in producing accurate probabilistic forecasts. Conventional post-processing methods operate by estimating the parameters of a parametric distribution, frequently on a per-location or per-lead-time basis. We propose a novel, neural network-based method, which produces forecasts for all locations and lead times, jointly. To relax the distributional assumption of many post-processing methods, our approach incorporates normalizing flows as flexible parametric distribution estimators. This enables us to model varying forecast distributions in a mathematically exact way. We demonstrate the effectiveness of our method in the context of the EUPPBench benchmark, where we conduct temperature forecast post-processing for stations in a sub-region of western Europe. We show that our novel method exhibits state-of-the-art performance on the benchmark, outclassing our previous, well-performing entry. Additionally, by providing a detailed comparison of three variants of our novel post-processing method, we elucidate the reasons why our method outperforms per-lead-time-based approaches and approaches with distributional assumptions

Semi-annual carbon and nitrogen isotope variations in the water column of Lake Bled, NW Slovenia

The variability in the stable isotope signature of carbon and nitrogen in particulate organic matter and dissolved species in the water column of the mesotrophic subalpine Lake Bled in NW Slovenia has been determined. After the algae bloom from August to December in 2008, samples were taken from the deepest part of the lake which develops an anoxic hypolimnion for most of the year. C/N molar ratios and δ¹³C_POC and δ¹⁵N_PN values suggest an autochthonous source for particulate organic matter (POM). According to the isotope model, autochthonous carbon accounted for a major part of the particulate organic carbon (POC), ranging from 86% to 96% in September and October, while in December the proportion of allochthonous carbon was more pronounced, ranging from 57% to 59%. Low δ¹³C_POC and δ¹⁵N_PN values (from −36 to −33‰ and from 0.8 to 1.8‰), observed below 24 m in August and September, indicate the bacterial origin of POM, mainly from methanotrophic bacteria. δ¹⁵N_NO₃ and δ¹⁵N_PN values decreased with depth. The relations between δ¹⁵N_PN and NO₃^- and NH₄⁺ concentrations suggest that NH₄⁺ is the main assimilation species for nitrogen in POM. Nitrification was active between 12 and 18 m deep in September and October, indicated by increased NO₃^- concentrations and decreased δ¹⁵N_NO₃ values. The correlation between nitrate concentrations and δ¹⁵N_NO₃ values suggests active water column denitrification in October 2008. The decrease in δ¹⁵N_NO₃ values observed in December could be explained by degradation of organic matter, followed by nitrification of the degradation products. During our sampling period, there was no evident influence of sewage, agriculture, or atmospheric deposition on the nitrogen balance in the lake

Riječni upliv na termohalina svojstva, zamućenost i suspendirane tvari u plitkom zaljevu (Koparski zaljev, sjeverni Jadran)

The influence of river discharge on the spatial and temporal variability of thermohaline and turbidity conditions at the sea surface (0.5 m) was studied in the shallow Bay of Koper (Gulf of Trieste, northern Adriatic Sea) which is influenced mainly by the polluted Rižana River. Conductivity, temperature and turbidity were measured monthly at 36 sampling sites between June 2011 and June 2013. Empirical orthogonal function analysis (EOF) was applied to investigate the data and to study the spatial distribution of variability and their temporal variations of temperature, salinity, density and turbidity. The EOF results showed an area of high variance in the proximity of the Rižana River mouth for all variables. The high variations in the time series for all variables were shown to be related mainly to high variations in the time series of the river discharges. Coupled field analysis showed the area of low salinity and high turbidity. A strong relationship was found between turbidity and suspended solid (TSS) concentration data collected in the local rivers and near shore zone suggesting that turbidity can be used as a satisfactory surrogate of TSS estimation.Utjecaj riječnog upliva na prostorne i vremenske varijabilnosti, termohalina svojstva i mutnoće na morskoj površini (0,5 m) je istraživano u plitkom Koparskom zaljevu (Tršćanski zaljev, sjeverni Jadran), koji je pod utjecajem uglavnom zagađene rijeke Rižana. Vodljivost, temperatura i mutnoća su mjereni mjesečno na 36 postaja između lipnja 2011. i lipnja 2013. Primijenjena je analiza empirijske ortogonalne funkcije (EOF) kako bi se istražili podaci i utvrdio prostorni raspored varijabilnosti, te vremenske promjene temperature, slanosti, gustoće i zamućenosti. Rezultati dobiveni EOF metodom su pokazali visoka odstupanja za sve varijable u području blizu ušća rijeke Rižana. Visoke varijacije u vremenskoj seriji za sve varijable su pokazala da se uglavnom odnose na visoke varijacije u vremenskom nizu riječnog dotoka. Združena analiza terenskih istraživanja pokazala je da se radi o području niske slanosti i visoke zamućenosti. Jaka veza je pronađena između zamućenosti i koncentracije suspendiranih krutih tvari (TSS), dok podaci prikupljeni u lokalnim rijekama i u neposrednoj blizini obale upućuju na to da se zamućenost može koristiti kao zadovoljavajući surogat za TSS procjene

Pyridazines. LXXVIII. Use of N,N-Dimethylaminomethylene Derivatives of Some Amino and Hydrazino Heterocycles in Organic Synthesis

The formation of N,N-dimethylaminomethylenehydrazino derivatives of pyridazine and azolopyridaz~nes is described and th.e synthetic utility of these compounds is explored. An unusual transformation could be observed with a aminomethyleinehydrazino derivative where upon .nitrosation the side chain is trainsformed into an azido group. From the corresponding N,N-dimethylaminomethyleneamino derivatives two new tricyclic azolotriazolopyridazmes could be prepared

SMIXS: Novel efficient algorithm for non-parametric mixture regression-based clustering

We investigate a novel non-parametric regression-based clustering algorithm for longitudinal data analysis. Combining natural cubic splines with Gaussian mixture models (GMM), the algorithm can produce smooth cluster means that describe the underlying data well. However, there are some shortcomings in the algorithm: high computational complexity in the parameter estimation procedure and a numerically unstable variance estimator. Therefore, to further increase the usability of the method, we incorporated approaches to reduce its computational complexity, we developed a new, more stable variance estimator, and we developed a new smoothing parameter estimation procedure. We show that the developed algorithm, SMIXS, performs better than GMM on a synthetic dataset in terms of clustering and regression performance. We demonstrate the impact of the computational speed-ups, which we formally prove in the new framework. Finally, we perform a case study by using SMIXS to cluster vertical atmospheric measurements to determine different weather regimes

Behaviour of Metal(loid)s at the Sediment-Water Interface in an Aquaculture Lagoon Environment (Grado Lagoon, Northern Adriatic Sea, Italy)

The cycling of metal(loid)s at the sediment\u2013water interface (SWI) was evaluated at two selected sites (VN1 and VN3) in an active fish farm in the Grado Lagoon (Northern Adriatic, Italy). In situ experiments using a transparent benthic chamber and the collection of short sediment cores were performed, to investigate the behavior of metal(loid)s in the solid (sediments) and dissolved (porewaters) phases. Total and labile concentration of metal(loid)s were also determined in sediments, to quantify their potential mobility. Comparable total concentrations were found at both sites, excluding As, Mn, Pb and V, which were higher at VN3. Metal(loid) porewater profiles showed a diagenetic sequence and a close dependence with redox (suboxic/anoxic) conditions in the surface sediments. Positive diffusive fluxes along with benthic fluxes, particularly at the more oxic site, VN1, were found for almost all metal(loid)s, indicating their tendency to migrate towards the overlying water column. Despite sediments at two sites exhibiting high total metal(loid) concentrations and moderate effluxes at the SWI, the results suggest that they are hardly remobilized from the sediments. Recycling of metal(loid)s from the SWI would not constitute a threat for the aquatic trophic chain in the fish farm

Dissolved gaseous mercury production and sea-air gaseous exchange in impacted coastal environments of the northern Adriatic Sea

The northern Adriatic Sea is well known for mercury (Hg) contamination mainly due to historical Hg mining which took place in Idrija (Slovenia). The formation of dissolved gaseous mercury (DGM) and its subsequent volatilisation can reduce the amount of Hg available in the water column. In this work, the diurnal patterns of both DGM production and gaseous elemental Hg (Hg0) fluxes at the water-air interface were seasonally evaluated in two selected environments within this area, a highly Hg-impacted, confined fish farm (VN: Val Noghera, Italy) and an open coastal zone less impacted by Hg inputs (PR: Bay of Piran, Slovenia). A floating flux chamber coupled with a real-time Hg0 analyser was used for flux estimation in parallel with DGM concentrations determination through in-field incubations. Substantial DGM production was observed at VN (range = 126.0–711.3 pg L−1) driven by both strong photoreduction and possibly dark biotic reduction, resulting in higher values in spring and summer and comparable concentrations throughout both day and night. Significantly lower DGM was observed at PR (range = 21.8–183.4 pg L−1). Surprisingly, comparable Hg0 fluxes were found at the two sites (range VN = 7.43–41.17 ng m−2 h−1, PR = 0–81.49 ng m−2 h−1), likely due to enhanced gaseous exchanges at PR thanks to high water turbulence and to the strong limitation of evasion at VN by water stagnation and expected high DGM oxidation in saltwater. Slight differences between the temporal variation of DGM and fluxes indicate that Hg evasion is more controlled by factors such as water temperature and mixing conditions than DGM concentrations alone. The relative low Hg losses through volatilisation at VN (2.4–4.6% of total Hg) further confirm that static conditions in saltwater environments negatively affect the ability of this process in reducing the amount of Hg retained in the water column, therefore potentially leading to a greater availability for methylation and trophic transfer

Elemental composition of plankton exometabolites (mucous macroaggregates): Control by biogenic and lithogenic components

Among the various exometabolitic effects of marine microorganisms, massive mucilage events in the coastal zones of temperate and tropical seas are the most spectacular and environmentally important. Abundant mucilage material in the form of aggregates appears in late spring/early summer in the water column of the Adriatic Sea. These macroaggregate biopolymers originate mainly from plankton exometabolites, with both autochthonous and allochthonous components, and strongly impact the tourism, fisheries, and economy of coastal countries. In contrast to extensive studies on the structural and chemical nature of macroaggregates performed over past decades, the full elemental composition of these substances remains poorly known, which does not allow for a complete understanding of their origin, evolution, and necessary remediation measures. Here, we report the results of comprehensive analyses of 55 major and trace elements in the composition of macro aggregates collected at the surface and in the water column during massive mucilage events. Through normalization of the elemental chemical composition of the upper earth crust (UCC), river suspended material (RSM), mean oceanic plankton, and mean oceanic particulate suspended material, we demonstrate that the water column macroaggregates reflect a superposition of the signal from plankton and marine particulate matter. The surface macroaggregates were preferentially enriched in lithogenic component, and carried the signature of planktonic material. The rare earth element (REE) signal was strongly dominated by plankton and, to a lesser degree, by oceanic particulate matter, while at the same time being strongly (>80 times) impoverished compared with UCC and RSM. Taken together, the elemental composition of macroaggregates allows for distinguishing the lithogenic and biogenic impacts on the occurrence of these unique large-scale mucilage events, linked to the exometabolism of marine plankton combined with the input of allochthonous inorganic material