Nitrogen is the main nutrient in soil. The long-term addition of N leads to changes in the soil dissolved organic matter (DOM) and other quality indicators, which affects the adsorption and accumulation of organic pollutants. The use of organic fertilizer is important for the development of green agriculture. However, organic fertilizers (especially sludge organic fertilizers (SOFs) contain phthalates (PAEs) that may accumulate in the soil and result in environmental contamination. How this accumulation response varies with the magnitude of long-term N addition, especially in different soil layer profiles, remains unclear. Here, changes in the content of PAEs in the soil–plant system without and after SOFs application were studied through field experiments in soils with different N addition backgrounds (CK, N1, N3 (0, 100, 300 kg N ha⁻¹ yr⁻¹ respectively)). Our results showed that the application of SOFs increase the accumulation of PAEs in soil profiles and plant systems, increasing human health risks. The content of Σ₅PAEs in the topsoil increased from 0.96 ± 0.10 to 1.86 ± 0.09 mg kg⁻¹. Moreover, under a high N addition background and SOFs application, the characteristics of soil DOM change, and the accumulation of PAEs in soil was nearly 30% higher compared with the low N group. Some suggestions such as removing PAEs from SOFs during preparation, conducting soil surveys before applying PAEs, and using soil amendments, which are provided for optimizing the trialability and environmental safety of SOFs application.

In the last decade, the study of the origin and fate of plastic debris received great attention, leading to a new and broad awareness of the hazard represented by these particles for the environment and the biota. At the same time, the scientific consideration on the leading role of the environment regarding the spread of antibiotic resistant bacteria (ARB) increased. Both, microplastic particles (MPs) and ARB share pollution sources and, in aquatic systems, MPs could act as a novel ecological niche, favouring the survival of pathogens and ARB. MPs can host a specific microbial biofilm, referred to as plastisphere, phylogenetically different from the surrounding planktonic microbial community and from the biofilm growing on other suspended particles. The plastisphere can influence the overall microbiome of a specific habitat, by introducing and supporting different species and by increasing horizontal gene transfer. In this review we collect and analyse the available studies coupling MPs and antibiotic resistance in water, highlighting knowledge gaps to be filled in order to understand if MPs could effectively act as a carrier of ARB and antibiotic resistance genes, and pose a real threat to human health.

Antibiotic resistance genes (ARGs) are emerging contaminants in the environment and have been highlighted as a worldwide environmental and health concern. As important participants in the biogeochemical cycles, mangrove ecosystems are subject to various anthropogenic disturbances, and its microbiota may be affected by various contaminants such as ARGs. This study selected 13 transects of mangrove-covered areas in Hainan, China for sediment sample collection. The abundance and diversity of ARGs and mobile genetic elements (MGEs) were investigated using high-throughput quantitative polymerase chain reaction (HT-qPCR), and high-throughput sequencing was used to study microbial structure and diversity. A total of 179 ARGs belonging to 9 ARG types were detected in the study area, and the detection rates of vanXD and vatE-01 were 100%. The abundance of ARGs was 8.30 × 10⁷–6.88 × 10⁸ copies per g sediment (1.27 × 10⁻²–3.39 × 10⁻² copies per 16S rRNA gene), which was higher than similar studies, and there were differences in the abundance of ARGs in these sampling transects. The multidrug resistance genes (MRGs) accounted for the highest proportion (69.0%), which indicates that the contamination of ARGs in the study area was very complicated. The ARGs significantly positively correlated with MGEs, which showed that the high level of ARGs was related to its self-enhancement. The dominant bacteria at the genus level were Desulfococcus, Clostridium, Rhodoplanes, Bacillus, Vibrio, Enterococcus, Sedimentibacter, Pseudoalteromonas, Paracoccus, Oscillospira, Mariprofundus, Sulfurimonas, Aminobacterium, and Novosphingobium. There was a significant positive correlation between 133 bacterial genera and some ARGs. Chthoniobacter, Flavisolibacter, Formivibrio, Kaistia, Moryella, MSBL3, Perlucidibaca, and Zhouia were the main potential hosts of ARGs in the sediments of Hainan mangrove area, and many of these bacteria are important participants in biogeochemical cycles. The results contribute to our understanding of the distribution and potential hosts of ARGs and provide a scientific basis for the protection and management of Hainan mangrove ecosystem.

Understanding wetland water quality dynamics and associated influencing factors is important to assess the numerous ecosystem services they provide. We present a combined self-organizing map (SOM) and linear mixed-effects model (LMEM) to relate water quality variation of multipond systems (MPSs, a common type of non-floodplain wetlands in agricultural regions of southern China) to their extrinsic and intrinsic influences for the first time. Across the 6 test MPSs with environmental gradients, ammonium nitrogen (NH₄⁺-N), total nitrogen (TN), and total phosphate (TP) almost always exceeded the surface water quality standard (2.0, 2.0, and 0.4 mg/L, respectively) in the up- and midstream ponds, while chlorophyll-a (Chl-a) exhibited hypertrophic state (≥28 μg/L) in the midstream ponds during the wet season. Synergistic influences explained 69±12% and 73±10% of the water quality variations in the wet and dry season, respectively. The adverse, extrinsic influences were generally 1.4, 6.9, 3.2, and 4.3 times of the beneficial, intrinsic influences for NH₄⁺-N, nitrate nitrogen (NO₃⁻-N), TP, and potassium permanganate index (CODMₙ), respectively, although the influencing direction and degree of forest and water area proportion were spatiotemporally unstable. While CODMₙ was primarily linked with rural residential areas in the midstream, higher TN and TP concentrations in the up- and midstream were associated with agricultural land, and NH₄⁺-N reflected a small but non-negligible source of free-range poultry feeding. Pond surface sediments exhibited consistent, adverse effects with amplifications during rainfall, while macrophyte biomass can reflect the biological uptake of CODMₙ and Chl-a, especially in the mid- and downstream during the wet season. Our study advances nonpoint source pollution (NPSP) research for small water bodies, explores nutrient “source-sink” dynamics, and provides a timely guide for rural planning and pond management. The modelling procedures and analytical results can inform refined assessment of similar NFWs elsewhere, where restoration efforts are required.

The aggregation kinetics of fragmental polyethylene glycol terephthalate (PET) nanoplastics under various chemistry conditions in aqueous environment were firstly investigated in this work. The aggregation of PET nanoplastics increased with increasing electrolyte concentrations and decreasing solution pH, which became stronger with the presence of divalent cations (e.g. Ca²⁺ and Mg²⁺) than that of monovalent cations (e.g. Na⁺ and K⁺). The effect of cations with the same valence on the aggregation of PET nanoplastics was similar. The measured critical coagulation concentrations (CCC) for PET nanoplastics at pH 6 were 55.0 mM KCl, 54.2 mM NaCl, 2.1 mM CaCl₂ and 2.0 mM MgCl₂, which increased to 110.4 mM NaCl and 5.6 mM CaCl₂ at pH 10. In addition, the aggregation of PET nanoplastics was significantly inhibited with the presence of humic acid (HA), and the CCC values increased to 558.8 mM NaCl and 12.3 mM CaCl₂ (1 mg L⁻¹ HA). Results from this study showed that the fragmental PET nanoplastics had the quite higher CCC values and stability in aqueous environment. In addition, the aggregation behaviors of PET nanoplastics can be successfully predicted by the Derjguin Landau Verwey Overbeek (DLVO) theory.

Passive biomonitoring was applied in four Atlantic forest plots in southeast Brazil, affected by different levels of trace metal pollution (OP site located in Minas Gerais State and PEFI, PP and STG located in São Paulo State). Native tree species were selected as biomonitors according to their abundance in each plot and successional classification. Current trace metal concentrations in total suspended particles, leaves of non-pioneer (NPi) and pioneer (Pi) species, topsoil (0–20 cm) and litter and concentration ratios at the plant/soil interface were analyzed to verify the atmosphere-plant-soil interactions, basal concentrations, spatial variations and metal accumulation at the ecosystem level. Redundant analysis helped to identify similar characteristics of metal concentrations in PP and PEFI, which can be influenced by the high concentrations of elements related to anthropogenic inputs. Analysis of variance and multivariate statistics indicated that the trees of OP presented higher concentrations of Cr, Fe, Mn and Ni than those in the other sites. High enrichment of Cd, Fe, Ni in non-pioneer plants indicated that the PP forest (initially considered as the least polluted) has still been affected by metal pollution. Soil collected in STG was enriched by all elements, however these elements were low available for plant uptake. Metal deposited in leaves and litter was an important sink for soil cycling, nevertheless, these metals are not bioavailable in most cases. Non-pioneer tree species revealed to be more appropriate than pioneer species to indicate the current panorama of the contamination and bioavailability levels of trace metals in the tree community-litter-soil interface of the Atlantic forest remnants included in this study.

Plastic pollution continues to seep into natural and pristine habitats. Emerging laboratory-based research has evoked concern regarding plastic’s impact on ecosystem structure and function, the essence of the ecosystem services that supports our life, wellbeing, and economy. These impacts have yet to be observed in nature where complex ecosystem interaction networks are enveloped in environmental physical and chemical dynamics. Specifically, there is concern that environmental impacts of plastics reach beyond toxicity and into ecosystem processes such as primary production, respiration, carbon and nutrient cycling, filtration, bioturbation, and bioirrigation. Plastics are popularly regarded as recalcitrant carbon molecules, although they have not been fully assessed as such. We hypothesize that plastics can take on similar roles as natural recalcitrant carbon (i.e., lignin and humic substances) in carbon cycling and associated biogeochemistry. In this paper, we review the current knowledge of the impacts of plastic pollution on marine, benthic ecosystem function. We argue for research advancement through (1) employing field experiments, (2) evaluating ecological network disturbances by plastic, and (3) assessing the role of plastics (i.e., a carbon-based molecule) in carbon cycling at local and global scales.

Forest soils are among the world’s largest repositories for long-term accumulation of atmospherically deposited mercury (Hg), and understanding the potential for remobilization through gaseous emissions, aqueous dissolution and runoff, or erosive particulate transport to down-gradient aquatic ecosystems is critically important for projecting ecosystem recovery. Forestry operations, especially clear-cut logging where most of the vegetaiton is removed, can influence Hg mobility/fluxes, foodweb dynamics, and bioaccumulation processes. This paper measured surface-air Hg fluxes from catchments in the Pacific Northwest, USA, to determine if there is a difference between forested and logged catchments. These measurements were conducted as part of a larger project on the impact of forestry operations on Hg cycling which include measurements of water fluxes as well as impacts on biota. Surface-air Hg fluxes were measured using a commonly applied dynamic flux chamber (DFC) method that incorporated diel and seasonal variability in elemental Hg (Hg⁰) fluxes at multiple forested and harvested catchments. The results showed that the forested ecosystem had depositional Hg⁰ fluxes throughout most of the year (annual mean: −0.26 ng/m²/h). In contrast, the harvested catchments showed mostly emission of Hg⁰ (annual mean: 0.63 ng/m²/h). Differences in solar radiation reaching the soil was the primary driver resulting in a shift from net deposition to emission in harvested catchments. The surface-air Hg fluxes were larger than the fluxes to water as runoff and accounted for 97% of the differences in Hg sequestered in forested versus harvested catchments.

Since the early 2000s, an increasing number of power plants in the U.S. have switched from burning coal to burning gas and thus have released less SO₂ emissions into the atmosphere. We investigated whether stream chemistry (i.e., SO₄²⁻) also benefits from this transition. Using publicly available data from Pennsylvania (PA), a U.S. state with heavy usage of coal as fuel, we found that the impact of SO₂ emissions on stream SO₄²⁻ can be observed as far as 63 km from power plants. We developed a novel model that incorporates an emission-control technology trend for coal-fired power plants to quantify potentially avoided SO₂ emissions and stream SO₄²⁻ as power plants switched from coal to gas. The results show that, if 30% of the electricity generated by coal in PA in 2017 had been replaced by that from natural gas, a total of 20.3 thousand tons of SO₂ emissions could have been avoided and stream SO₄²⁻ concentrations could have decreased as much as 10.4%. Extrapolating the model to other states in the U.S., we found that as much as 46.1 thousand tons of SO₂ emissions per state could have been avoided for a similar 30% coal-to-gas switch, with potential amelioration of water quality near power plants. The emission-control technology trend model provides a valuable tool for policy makers to assess the benefits of coal-to-gas shifts on water quality improvements as well as the effectiveness of emission control technologies.

Freshwater ecosystems are negatively impacted by various pollutants, from agricultural, urban and industrial wastewater, with metals being one of the largest concerns. Moreover, freshwater ecosystems are often affected by alien species introductions that can modify habitats and trophic relationships. Accordingly, the threat posed by metals interacts with those by alien species, since the latter can accumulate and transfer these substances across the food web to higher trophic levels. How metals transfer within such communities is little studied. We analysed the concentration of 14 metals/metalloids (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Se, Zn, hereafter ‘metal(s)’) of eight fish and three crustacean species co-existing in the Arno River (Central Italy), most of which were alien. To assess the pathway of contaminants within the community, we coupled metal analysis with carbon and nitrogen stable isotope analysis derived from the same specimens. Crustaceans showed higher metal concentration than fish, except for Cd, Hg and Se that were higher in fish. We found evidence of trophic transfer for six metals (Cd, Cr, Hg, Mg, Se, Zn). Additionally, ontogenetic differences and differences among various fish tissues (muscle, liver, and gills) were found in metals concentration. Considerable biomagnification along the trophic chain was found for Hg, while other metals were found to biodilute. Using stable isotopes and Hg as a third diet tracer, we refined the estimations of consumed preys in the diet previously reconstructed with stable isotope mixing models. Alien species reach high biomass and can both survive to and accumulate high pollutants concentrations, potentially posing a risk for their predators and humans. A combined effect of environmental filtering and increased competition may potentially contribute to the disappearance of native species with lower tolerances.