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Benthic bacterial communities play a critical role in nutrient cycling and are highly sensitive to environmental pollution. This study aimed to investigate the physiological, compositional and functional responses of bacterial communities across a range of carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) gradients in sediments from Lake Villarrica, Chile. Sediment samples were collected from 5 sites representing a gradient of nutrient pressure from the lake basin (NL < PuB < PoP < SL < VB). Nutrient forms (TC, TN, TP, TS, and OM) were chemically quantified. Community function was assessed via community-level physiological profiles (CLPPs) using Biolog^® EcoPlates (C substrates), PM3B (N substrates), and PM4A (P and S substrates). Function and composition were assessed based on total bacterial and functional nutrient-cycling gene abundances (16Sr RNA, chiA, mcrA, nifH, amoA, nosZ, phoD, pqqC, soxB, dsrA) using qPCR and 16S rRNA metabarcoding, respectively. In general, the CLPPs were higher for C substrates, followed by P, S, and N substrates, with metabolism of organic forms of these nutrients preferential, and P-cycling genes were the most abundant in the lake. Spatially, the most nutrient-enriched site (VB) showed a significantly (p ≤ 0.05) higher nutrient content (e.g., 5.4% TC, 0.54% TN, 1302.8 mg kg⁻¹ TP and 854.1 mg kg⁻¹ TS) and total bacterial abundance (2.9 × 10¹¹ gene copy g⁻¹ dw sediment) but displayed lower CLPPs (from 0.63 to 1.02 AWCD) and nutrient-cycling gene abundances (e.g., 9.1 × 10¹, 2.7 × 10³, 3.6 × 10³ and 4.7 × 10³ gene copy g⁻¹ dw sediment for chiaA, nifH, phoD and dsrA, respectively) compared to the less nutrient-enriched sites (e.g., NL). The bacterial community composition shifted accordingly, with Bacillota enriched in VB and Planctomycetota occurring more frequently in less nutrient-exposed sites. Functional prediction analysis revealed enhanced methanotrophy and sulfate respiration in nutrient-rich sediments, whereas nitrification and organic P (P_o) mineralization dominated in less impacted areas. The results demonstrate that nutrient enrichment constrains bacterial functional diversity in Lake Villarrica and, so, may be useful indicators of environmental stress to be considered in pollution monitoring programmes. Full article

The aim of this study was to perform a morphometric analysis of Prussian carp individuals collected from the Moara Domnească pond in Ilfov County, Romania. This was accompanied by a physico-chemical characterization of the water, which was sampled from the same location. Consequently, we analyzed a total of 60 Prussian carp individuals that were caught in April (N = 32) and May 2023 (N = 28). For the Carassius gibelio in the study site, we provided, for the first time, data on the weight–length relationships (WLRs), the Fulton K condition factor and the biometric features, including the total length (TL), standard length (SL), head length (HL), snout length (SNL), body depth (BD), girth and ratios for the TL/HL, as well for the TL/BD and TL/SL. A negative growth type was estimated for both the samples of C. gibelio. Based on other studies and fishing reports, besides C. gibelio, there are another 11 species that belong to the Cypriniformes order, and there are two teleost members of the Perciformes order (Lepomis gibbosus and Perca fluviatilis)—these were also associated with this habitat. Water samples were collected from 12 sampling points (SP), which were subjected to physico-chemical characterizations that consisted of an assessment of the turbidity (T), pH, electrical conductivity (EC), chloride (Cl⁻), total hardness (TH), oxygen regime parameters, phosphate phosphorus (P-PO₄³⁻), nitrate nitrogen (N-NO₃⁻), nitrite nitrogen (N-NO₂⁻) and ammonium nitrogen (N-NH₄⁺) levels. In addition, considering their characteristics (high toxicity, non-biodegradability, long-range atmospheric transport and bioaccumulation potential), a number of organochlorine pollutants (OCPs) were identified. The total hardness values presented a very significant correlation with conductivity (r = 0.5974 ***) and with pH (r = 0.5854 ***). The results allowed for the water samples to be placed into the quality classes established by legislation, and they were also discussed in relation to the fishes’ requirements. Full article

Nitrate-nitrogen (NO₃⁻–N) removal and garden waste disposal are critical concerns in urban environmental protection. In this study, biochars were produced by pyrolyzing various garden waste materials, including grass clippings (GC), Rosa chinensis Jacq. branches (RC), Prunus persica branches (PP), Armeniaca vulgaris Lam. branches (AV), Morus alba Linn. sp. branches (MA), Platycladus orientalis (L.) Franco branches (PO), Pinus tabuliformis Carrière branches (PT), and Sophorajaponica Linn. branches (SL) at three different temperatures (300 °C, 500 °C, and 700 °C). These biochars, labeled as GC300, GC500, GC700, and so on., were then used to adsorb NO₃⁻–N under various conditions, such as initial pH value, contact time, initial NO₃⁻–N concentration, and biochar dosage. Kinetic data were analyzed by pseudo-first-order and pseudo-second-order kinetic models. The equilibrium adsorption data were evaluated by Langmuir, Freundlich, Temkin and Dubinin–Radushkevich models. The results revealed that the biochar yields varied between 14.43% (PT700) and 47.09% (AV300) and were significantly influenced by the type of garden waste and decreased with increasing pyrolysis temperature, while the pH and ash content showed an opposite trend (p < 0.05). The efficiency of NO₃⁻–N removal was significantly influenced by the type of feedstock, preparation process, and adsorption conditions. Higher pH values had a negative influence on NO₃⁻–N adsorption, while longer contact time, higher initial concentration of NO₃⁻–N, and increased biochar dosage positively affected NO₃⁻–N adsorption. Most of the kinetic data were better fitted to the pseudo-second-order kinetic model (0.998 > R² > 0.927). Positive b values obtained from the Temkin model indicated an exothermic process of NO₃⁻–N adsorption. The Langmuir model provided better fits for more equilibrium adsorption data than the Freundlich model, with the maximum NO₃⁻–N removal efficiency (62.11%) and adsorption capacity (1.339 mg·g⁻¹) in PO700 under the conditions of pH = 2, biochar dosage = 50 mg·L⁻¹, and a reaction time of 24 h. The outcomes of this study contribute valuable insights into garden waste disposal and NO₃⁻–N removal from wastewater, providing a theoretical basis for sustainable environmental management practices. Full article

The former St. Antony’s Lead Works site, now the central part of an urban recreational park (Walker Riverside Park) in the east end of Newcastle upon Tyne (England, UK), has been assessed based on the Pb concentration in topsoil according to recently derived Category 4 Screening Level (C4SL) for public open space–park (POS_park, 1300 mg/kg). The site was divided into eight sampling areas following its physical layout. In total 79 soil samples were collected, characterised for acidity and organic matter content, and analysed by energy dispersive X-ray fluorescence (ED-XRF). The Pb levels in most of the samples, particularly those from the fringes of the site, are below the generic guideline value (down to 70 mg/kg). More than 16% of the samples from nearly all sampling areas, especially those sampling points around the former horizontal condenser flue and main chimney, contain levels of Pb significantly exceeding the limit (up to 206,000 mg/kg). No correlation is found between the Pb concentration in soil samples and their acidity (mostly neutral, pH 7.0 ± 0.5) or organic matter content (15.5 ± 4.1%). Using the Contaminated Land Exposure Assessment (CLEA) model (version 1.071), the site-specific risk assessment criteria (SSAC) for Lead (C4SL child), 2862 mg/kg, is obtained based on adjusted exposure frequency and occupancy period. Nearly 9% of the individual sample Pb concentrations (n = 79) across sample locations B, C, D and H are still above the specific value. Further statistical evaluation based on 95% upper confidence limit confirms that the site still represents a potential human health risk. This is because Pb concentrations, from two areas in the centre of the site (sample locations B and C), are greatly over the SSAC specific threshold (sample mean at location B is 12,350 mg/kg and at location C is 11,745 mg/kg). Full article