Nitrates present one of the main groundwater contaminants in the world and in the Zagreb aquifer. In order to reduce nitrate concentrations in groundwater, it is necessary to spatially define main nitrogen sources and areas which have the highest risk of nitrate contamination. This paper presents a map of nitrate contamination risk in the area of the Zagreb aquifer. It was constructed based on nine different layers that include natural characteristics and anthropogenic pressures. For the construction of the Main map, which has been defined as the most representative one, 15 different variations have been tested. The Main map has shown that the urban part of the City of Zagreb, especially central and eastern parts, together with the area of Jakuševec landfill and marshalling station, present areas with the highest risk of nitrate contamination, which is consistent with the results of previous research. ARTICLE HISTORY

The former manganese ferroalloy plant and the remaining tailings are affecting the quality of the environment in Šibenik Bay, Croatia, even though industrial activities ceased more than 25 years ago. This study has revealed that the main manganese mineral phases present in the recently collected tailings, as well as in the dust collected on the roof of the plant during the production period, are bustamite and Mn-oxides. The same type of Mn mineral phases was also found in recently collected sediments from Šibenik Bay. Detailed chemical and phase analyses (XRD, BCR sequential analysis, aqua regia and lithium borate fusion) of the dust sample revealed high manganese values (24.1%), while granulometric analysis showed that 50% of the particles are smaller than PM2.5. The influence of the tailings is visible in the sediment, but the concentrations of the potentially toxic elements determined by the sequential BCR analysis are within the legal limits. Some higher values (20.3 g/kg Mn, 595 mg/kg Pb and 494 mg/kg Zn) are detected in the tailings, which are still exposed to weathering and as such should be additionally monitored. On the other hand, this material contains a considerable number of elements that could be considered lucrative (∑ REE up to 700 mg/kg, Mn up to 23 g/kg, Fe up to 37 g/kg and Al up to 25 g/kg), opening the possibility of reuse and recovery.

<p>The aim of the study was to determine the correlation of metals on floating marine litter and weathered microplastic samples from the pristine area. Sampled were collected from the accumulated material on the natural beach in Mala Stupica Cove (Žirje Island, Croatia) in June 2020. In addition to weathered microplastic, the concentrations of dissolved metals in the seawater, at the same location were determined. According to these measurements, the sampling site can be considered pristine, with Cd and Pb concentrations as background values and Zn and Cu as elements that have no toxic effect, based on the classification proposed by Bakke et al., (2010). The metals of interest due to their high toxicity were Zn, Cd, Pb, and Cu.</p><p>After sampling, the collected material was sieved through a metal sieve with a 4 mesh size, resulting in 4 subsamples (>4 mm; 4-2 mm; 2-1 mm; 1-0.250 mm). The type of plastic particles from subsample >4 mm was determined by FTIR spectroscopy performed on Bruker Tensor 27 in the region from 400-4000 cm<sup>-1</sup>. On such defined particles and in the seawater sample, trace metal concentrations were determined by the electrochemical method differential pulse anodic stripping voltammetry (DPASV) with standard addition method by Metrohm Autolab modular potentiostat/galvanostat Autolab PGSTAT204. A static mercury drop electrode (SMDE) was used as the working electrode.</p><p>Plastic particles were isolated from additional two fractions (2-1 mm and 1-0.250 mm) as bulk samples, but without polystyrene, and the metal concentration was also determined using the same method. Due to the particle size, the type of plastic was not determined. Additional analyzes of metal concentrations on a defined and isolated polystyrene particles (PS) from a subsample (4-2 mm) and (2-1 mm) were also performed.</p><p>By analogy with sediment particles, one would expect smaller microplastic particles to have higher metal concentrations due to their larger specific surface area, but this was not observed in this study. The metal concentration varied with the type of plastic, and from the observed results, plastics could be ranked according to their affinity for the analyzed metals, as follows: polystyrene (PS)>Polypropylene (PP)>Low-density polyethylene (LDPE). According to an average concentration of all analyzed samples defined as LDPE, Zn could be single out as an element with around 7-time higher affinity for LDPE than other elements (Cd, Pb, and Cu). For samples defined as PP, the highest affinity is observed for Pb, even 30 times higher than in LDPE, followed by Zn and Cu, while Cd has similar values as in LDPE.  For PS samples affinity of all elements is higher in comparison with the LDPE and PP, as follows: Pb>Cu> Zn>Cd, with a concentration of Pb 2.5 times higher than in PP and even 88 times higher than in LDPE.</p><p> A general conclusion could be drawn, but the observed wide ranges indicate the need for additional research to determine the relationship between the degree and type of weathering with the associated metals.</p><p>This work has been fully supported by Croatian Science Foundation under the project lP-2019-04-5832.</p>

No abstract

<p>To determine the influence of the historic factory of electrodes and ferroalloys on the Šibenik bay sediments, XRPD analysis were carried out. The factory was established in the city of Šibenik, on the coast of the Krka River estuary, and produced calcium carbide, and later electrodes and ferroalloys. It was active from 1900 until 1995 [1]. During that time, a large amount of produced tailings were stored nearby and on the shore of the estuary. Due to the presence of the strong winds (bora and sirocco), which can reach up to 130 km/h, the tailings material could be transported to long distances [2].</p><p>Samples of tailing were collected at the location of the former factory, which is a tailing hill today, samples of dust were collected from the rooftop of the factory in the 1980s. Other samples were taken on a 1 km distant beach in the Šibenik bay  (Beach A) and a 19 km distant beach on the island in the outer Šibenik archipelago (Beach B). Both beaches are located south-west of the factory. The samples from the beaches were taken with a corer at different depths: 0 – 3 cm, 3 – 5 cm, around 5 cm. The sample from 3 – 5 cm depth was not analysed.</p><p>Bulk sample and a fraction <63 µm were analysed on X-Ray Diffractometer. The XRPD analysis of the sediments from Beach B in the outer Šibenik archipelago shows that calcite and quartz are the most abundant phases. This mineral composition shows that distant islands were not affected by aeolian transportation of the factory dust and tailing. In the bulk samples from Beach A, in the uppermost part (0 – 3 cm depth) mineral components are calcite, aragonite, calcium manganite, bustamite ferroan and carbon, while calcite, quartz, aragonite, calcium manganite and manganosite are present in the fraction <63 µm. The sample from the depth of 5 cm at the same beach, shows calcite, aragonite and Mn-oxide, while fraction <63 µm lacks in Mn-oxide.</p><p>A bulk sample of tailings shows mineral components: calcite, quartz, calcium manganite, bustamite ferroan and gypsum which corresponds to the previous research [3], and there is also manganese silicon, manganese silicide, carbon and amorphous phase [4]. A fraction <63 µm of the tailing, shows the following mineral phases: calcite, quartz, calcium manganite and bustamite ferroan, as presented in previous research [3]. Analysis of the rooftop dust shows three phases: carbon, bustamite ferroan and manganosite, which does not correspond to the data given from the factory [3].</p><p>From the presented results, it could be concluded that the historic factory influenced sediments in the Šibenik bay, however, its influence was not detected on the Beach B 19 km to the SW, which opens the question of reach and distance to which tailings can be transported by sea and/or wind.</p><p>This work has been supported in part (samples collection) by Croatian Science Foundation under the project lP-2019-04-5832.</p>