Gustavo Riveros

Landfill leachate is a complex and variable wastewater rich in organic matter, ammonium, salts, and metals, with low biodegradability and highly fluctuating composition. Its management still largely relies on energy- and chemical-intensive treatment schemes, making the treatment of raw, undiluted landfill leachate particularly challenging. This study evaluates, at lab scale, the potential of aerobic granular sludge (AGS) for achieving simultaneous pollutant removal and metal recovery in a 2-L column sequencing batch reactor fed with raw, undiluted landfill leachate collected from an active municipal landfill site. The reactor was operated for 198 days without dilution or addition of co-substrates. This operation resulted in stable granulation and high removal efficiencies, 94% for chemical oxygen demand (COD) and 97% for total nitrogen. Cation analysis shows that assimilation reached 600.47 µmol g⁻¹ TS, with calcium and magnesium being the predominant cations. Quantitative analyses revealed near-equal contributions from biosorption (53%) and bioaccumulation (47%), with magnesium dominating biosorption and calcium prevailing in bioaccumulation. Then, a partial metal recovery was achieved by desorption with 0.1 M NaCl, without compromising the granule structure, as verified by FTIR and scanning electron microscopy (SEM). However, the desorption process reduced nitrification and denitrification activities by factors of 3.7 and 1.8, respectively, while heterotrophic activity increased by 2.4-fold. Metagenomic analysis revealed microbial shifts following desorption, favouring genera such as Paracoccus and Burkholderia, which are associated with heterotrophic metabolism. These results demonstrate the potential of AGS as a regenerative biosorbent for treating landfill leachate and recovering metals. This approach supports sustainable and circular strategies for managing landfill leachate and similar complex effluents.

Microplastics (MPs) alter soil properties and plant physiology and pose a significant risk to crop health and food quality. This study assessed the effects of MPs (polyamide‐PA, low‐density polyethylene‐LDPE, and polypropylene‐PP) on Andisol and Raphanus sativus L. as a model plant. Plant characteristics, including growth, chlorophyll content, oxidative stress, antioxidant capacity, and bioactive compound profiles, were evaluated. In addition, the effects on soil nutrients, microbiological properties, and bacterial nitrogen‐cycling gene abundance were studied, revealing alterations in both soil and plants. Soil pH increased up to 4.3%, whereas dissolved organic carbon and polyphenol levels decreased, particularly in the PA (26%) and PP (29%) treatments. LDPE and PP increased β‐glucosidase activity (14% and 23%, respectively) and basal soil respiration (25% and 26%, respectively). Nitrogen‐cycling genes nifH , amoA , and nirS were notably more abundant in PP‐treated soils, with increases of 79%, 76%, and 62%, respectively. In R. sativus , PA and LDPE increased SPAD values by 9.9% and increased biomass in rootlets (155% in PA, 60% in LDPE) and radishes (125% in PP). Oxidative stress levels in radishes increased by 63% and 73% after exposure to LDPE and PP, respectively. MPs altered glucosinolate profiles in leaves and rootlets. Furthermore, PA and LDPE modified anthocyanin profiles in leaves, whereas PP altered the profile in radishes. This study highlights the impact of MPs on soil and plant physiology, identifying polyphenols and microbial biomass carbon as key predictors of R. sativus response.

Lotmaria passim currently appears to be the predominant trypanosome in honey bees worldwide. Although, the specific effects of L. passim by single or mixed with other gut parasites such as Nosema ceranae on honey bees’ health is still unclear. We consequently measured bees’ survival, parasite loads, the expression of antimicrobial peptides (AMPs) and vitellogenin gene. Thus, (1) bees naturally infected with L. passim, (2) healthy bees inoculated with Nosema ceranae, (3) bees naturally infected with L. passim and inoculated with N. ceranae and (4) healthy bees (control) were maintained under controlled conditions. Honey bees infected with N. ceranae or with mixed infections of L. passim and N. ceranae had significantly lower survival rates than the control group at 20 days post-inoculation (dpi). A competitive suppression was also detected, provided that the L. passim load was significantly affected by the presence of N. ceranae at 15 dpi. Expressions of the AMPs defensin and hymenoptaecin rapidly (two hours post-inoculation) increased in bees infected with N. ceranae and mixed infections. However, this effect was not continuous. In fact, expressions of abaecin, defensin, hymenoptaecin and vitellogenin decreased drastically at 15 dpi in bees with both single and mixed infections. The decrease in the expression of AMPs and vitellogenin throughout this period was consistent with the reduced survivals observed in this study, indicating that mixed infections of L. passim and N. ceranae, and even into a scenario of competition between them, may have a synergic effect on the survival and immune-related gene expressions (biomarkers) of worker bees.

Deformed wing virus (DWV) is one of the most common viruses in apiaries worldwide, and its presence in Chilean apiaries is no exception. There are three well-defined master variants described as DWV-A, DWV-B (or VDV-1) and DWV-C. We studied the prevalence, load and recombinant genotypes among DWV variants in honey bees from Chilean apiaries. We also compared the viral load in each region in colonies that were treated or untreated against Varroa destructor. Using real-time PCR with specific primers enabled us to determine that DWV-A was the most prevalent (71%) throughout Chile, with a higher level than DWV-B (circa 3% prevalence), and almost 60-times more load, especially in northern Chile. The viral load was lower only in treated colonies located in the Metropolitana, Biobío/Ñuble and Los Ríos regions. The DWV-C genotype and recombinants were not detected. This suggests that viral recombinant events are limited since DWV-B is still uncommon in honey bee hives at present. This is the first study involving DWV-B in Chile.