The current study was conducted to assess the level and spatial distribution of metal pollution in surface water, soil, and sediment samples from the Arieș River basin, located in central Romania, an area impacted by various mining and industrial operations. Several pollution indices, spatial distributions, cluster analyses, principal component analyses, and heat maps were applied for evaluating the contamination level with Ni, Cu, Zn, Cd, Pb, Mn, As, and Hg in the area. Based on the results of the Heavy-Metal Pollution Index and of the Heavy-Metal Evaluation Index of the surface-water samples, the middle part of the Arieș River basin, near and downstream of the gold mine impoundment, was characterized by high pollution levels. The metal concentration was higher near the tailing impoundment, with increased levels of Cu, Ni, Zn, and Pb in the soil samples and As, Cd, Pb, Na, K, Ca, Mn, and Al in the sediment samples. Ca (23.7–219 mg/L), Mg (2.55–18.30 mg/L), K (0.64–14.70 mg/L), Al (0.06–22.80 mg/L), and Mn (0.03–22.40 mg/L) had the most remarkable spatial variation among the surface-water samples, while various metal contents fluctuated strongly among the sampling locations. Al varied from 743 to 19.8 mg/kg, Fe from 529 to 11.4 mg/kg, Ca from 2316 to 11.8 mg/kg, and Mg from 967 to 2547 mg/kg in the soil samples, and Al varied from 3106 to 8022 mg/kg, Fe from 314 to 5982 mg/kg, Ca from 1367 to 8308 mg/kg, and Mg from 412 to 1913 mg/kg in the sediment samples. The Potential Ecological Risk Index values for soil and sediments were in the orders Cu > Ni > Pb > Hg > Cr > As > Mn > Zn > Cd and As > Cu > Cr > Cd > Pb > Ni > Hg > Mn > Zn, respectively, and the highest values were found around the gold mine impoundment.

The aim of this study was to investigate the use of natural zeolite as support for microbial community formation during wastewater treatment. Scanning electron microscopy (SEM), thermal decomposition and differential thermogravimetric curves (TGA/DGT) techniques were used for the physicochemical and structural characterization of zeolites. The chemical characterization of wastewater was performed before and after treatment, after 30 days of using stationary zeolite as support. The chemical composition of wastewater was evaluated in terms of the products of nitrification/denitrification processes. The greatest ammonium (NH₄⁺) adsorption was obtained for wastewater contaminated with different concentrations of ammonium, nitrate and nitrite. The wastewater quality index (WWQI) was determined to assess the effluent quality and the efficiency of the treatment plant used, showing a maximum of 71% quality improvement, thus suggesting that the treated wastewater could be discharged into aquatic environments. After 30 days, NH₄⁺ demonstrated a high removal efficiency (higher than 98%), while NO₃⁺ and NO₂⁺ had a removal efficiency of 70% and 54%, respectively. The removal efficiency for metals was observed as follows (%): Mn > Cd > Cr > Zn > Fe > Ni > Co > Cu > Ba > Pb > Sr. Analysis of the microbial diversity in the zeolite samples indicated that the bacteria are formed due to the existence of nutrients in wastewater which favor their formation. In addition, the zeolite was characterized by SEM and the results indicated that the zeolite acts as an adsorbent for the pollutants and, moreover, as a support material for microbial community formation under optimal conditions. Comparing the two studied zeolites, NZ1 (particle size 1–3 mm) was found to be more suitable for wastewater treatment. Overall, the natural zeolite demonstrated high potential for pollutant removal and biomass support for bacteria community growth in wastewater treatment.

In the present study, the sorption behavior of iron (Fe) and manganese (Mn) from a binary metal solution system onto thermally activated natural zeolite was studied. Batch adsorption experiments were carried out to investigate the effects of zeolite quantity, particle size, and activation temperature. Equilibrium studies were carried out to evaluate the adsorption capacity of the thermally activated natural zeolite. The obtained results showed that the thermally activated natural zeolite favored the removal of Fe over Mn, due to competition between them. Elemental analysis of the activated zeolite samples obtained by energy-dispersive X-ray analysis (EDX) indicated a Si/Al ratio >4, which is specific for clinoptilolite-type zeolite. The removal of Fe and Mn was best described by the Langmuir model, indicating the formation of a monolayer on the surface of the activated natural zeolite. The kinetic results revealed that the experimental data were best fitted by the pseudo-second-order model for both metals. The results suggest that a new natural zeolite from Rupea quarry, Brașov County, Romania could be used as a potential adsorbent for removal of Fe and Mn from binary metal solution systems, addressing the lack of information about this material from this region.

Brewers’ spent grain (BSG), the main by-product of the brewing industry, is a rich source of minerals and water-soluble vitamins such as thiamine, pyridoxine, niacin, and cobalamin. Bioaccessibility through in vitro digestion is an important step toward the complete absorption of minerals and B group vitamins in the gastrointestinal system. Inductively coupled plasma optical emission spectrometry (ICP-OES) together with inductively coupled plasma quadrupole mass spectrometry (ICP-MS) was used for the quantification of the macro- and micro-minerals. An ultra-high performance liquid chromatography (UHPLC) system coupled with a diode array detector (DAD) was used for B group vitamin identification. Four different industrial BSG samples were used in the present study, with different percentages of malted cereals such as barley, wheat, and degermed corn. Calcium’s bioaccessibility was higher in the BSG4 sample composed of 50% malted barley and 50% malted wheat (16.03%), while iron presented the highest bioaccessibility value in the BSG2 sample (30.03%) composed of 65% Pale Ale malt and 35% Vienna malt. On the other hand, vitamin B1 had the highest bioaccessibility value (72.45%) in the BSG3 sample, whilst B6 registered the lowest bioaccessibility value (16.47%) in the BSG2 sample. Therefore, measuring the bioaccessibilty of bioactive BSG compounds before their further use is crucial in assessing their bioavailability.

Lithium is a critical element for the modern society due to its uses in various industrial sectors. Despite its unequal distribution in the environment, Li occurrence in Romania was scarcely studied. In this study a versatile measurement method using ICP-MS technique was optimized for the determination of Li from various matrixes. Water, soil, and plant samples were collected from two important karst areas in the Dobrogea and Banat regions, Romania. The Li content was analyzed together with other macro- and microelement contents to find the relationship between the concentration of elements and their effect on the plants’ Li uptake. In Dobrogea region, half of the studied waters had high Li concentration, ranging between 3.00 and 12.2 μg/L in the case of water and between 0.88 and 11.1 mg/kg DW in the case of plants, while the Li content in the soil samples were slightly comparable (from 9.85 to 11.3 mg/kg DW). In the Banat region, the concentration of Li was lower than in Dobrogea (1.40–1.46 μg/L in water, 6.50–9.12 mg/kg DW in soil, and 0.19–0.45 mg/kg DW in plants). Despite the high Li contents in soil, the Li was mostly unavailable for plants uptake and bioaccumulation.

Trees are considered to be an effective tool for metal pollution biomonitoring. In the present study, the concentration of metals (Cu, Pb, Zn, Cd, Co, Ni, Fe, Mn, and Al) in black poplar leaves (Populus nigra L.), together with the concentration of PM₁₀, PM_2.5, PM₁, and total suspended particles (TSP), was used for the air pollution biomonitoring in 12 sites from various areas of Cluj-Napoca city, Romania. The concentration of PM₁₀ in the air was high, but their metal content was low. However, Cu, Pb, and Zn were moderately enriched, while Cd was highly enriched in PM₁₀ due to anthropogenic sources. The average metal concentration in leaves decreased in the order Zn>>Fe>Mn>Al>Pb>Ni>Cu>Co>Cd and increased with the increase of PM₁₀ concentration, indicating that poplar leaves are sensitive to air pollution. The principal component analysis indicated that traffic, waste burning, road dust resuspension, and soil contamination are the main anthropogenic sources of metals in poplar leaves. The results indicated that black poplar leaves are a suitable biomonitoring tool for metal pollution, in urban environments.