Andrejs Grīnbergs

The fate of biobased and biodegradable cellulose-derived plastics in landfills represents an important topic from economic and environmental points of view. Anaerobic digestion is a cost-effective waste-to-energy technology. The behaviour of six polymer types—that is, cellulose (C), cellulose acetate (CA), viscose (V), nanocellulose (NC), acetate textile (AT), and heteropolysaccharide pectin (P)—was studied under anaerobic batch mesophilic conditions in a landfill leachate for 147 days. The cumulative biogas production was as follows: C>V=CA>>AT>>NC=P. Metagenomic analysis revealed notable variations in the proportion of bacterial and archaeal domains with the highest archaeal abundance in the presence of CA (80.2%) and C (78.5%). At the end of digestion, cellulolytic, hydrolytic, and dehydrogenase activities were measured in the intact samples, as well as the liquid and solid fractions, under aerobic and anaerobic conditions. Cellulolytic activity in P was detected only in the pellet, while in NC, activity was mostly in the supernatant under both aerobic and anaerobic conditions. Scanning electron microscopy and confocal scanning laser microscopy showed a defragmentation and degradation of polymeric substrates as well as microbial colonisation. Based on the results, landfill leachate is appropriate for the anaerobic biodegradation of cellulose-derived polymers; however, the process is polymer specific.

Landfill leachate is regarded as a significant point source of pollutants that may pose a hazard to the environment, particularly to surface and ground waters. Leachates are highly variable and heterogeneous. Our study was focused on the characterization of landfill leachates derived from young (YDS) and matured (MDS) dumpsites in terms of the abundance of micropollutants, antimicrobial resistance genes (ARG), and microbial community structure. The concentrations of poly- and perfluoroalkyl substances (PFASs) were found to be higher in MDS compared to YDS, i.e., 13.19 and 7.16 μg/L, respectively. Among pharmaceutical compounds, ibuprofen was detected at the highest concentrations, i.e., 12.54, 12.81, and 13.13 μg/L, in the leachates derived from MDS, YDS, and ponds. The distribution of bacteria, archaea, eukaryotes, and viruses in the three leachate samples was as follows: 85.15 ÷ 88.04%, 9.13 ÷ 12.29%, 2.20 ÷ 2.68%, and 0.12 ÷ 0.15%, respectively. In total, 31 distinct families of ARGs were identified, comprising a total of 80 ARGs. Incubation of P. putida MSCL650 in sterile leachate from the pond resulted in decreasing the minimum inhibitory concentrations for six antibiotics as compared to cells incubated in nutrient broth. Hydrological processes, i.e., runoff and infiltration, can increase the dissemination of ARGs.

The potential of aquatic plants to accumulate Cs may be of notable importance in the environmental monitoring of radioactive wastes. This study aimed to evaluate the accumulation of Cs-133 by freshwater macrophytes Bacopa amplexicaulis, Elodea densa, Ceratophyllum submersum, and Limnobium laevigantum after a 10-day incubation period with CsCl (1–1000 μM). The partitioning of Cs and other elements, including 21 metals, such as P, B, and As, was analyzed using inductively coupled plasma mass spectrometry combined with principal component analysis (PCA). The enzymatic activity of plant crude extracts and aquatic microorganisms was characterized. The transfer factor (TF) reached the highest values of 0.13 and 0.10 for C. submersum and L. laevigantum, respectively, at 1000 μM Cs. The TFs in the other sets were below 0.1. In the presence of Cs-133, there was a significant increase in dehydrogenase activity (p < 0.05) and a decrease in the activity of the Folin–Ciocalteu assay. A three-fold decrease in culturable microorganisms was found in plants with 1000 μM Cs. PCA analysis revealed the species-specific elemental distribution in plant biomass and the aquatic phase. A negative correlation between Na, Ca (2.0–2.5, PC1) and Mg, K, and P (−2, PC1) was found. Certain enzyme groups can serve as bioindicators of Cs pollution in aquatic ecosystems.