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The global consumption and production of pharmaceuticals is increasing concomitantly with concern regarding their environmental fate and effects. Active pharmaceutical ingredients are mainly released into the aquatic environment through wastewater effluent discharge. Once in the environment, pharmaceuticals can undergo processes of natural attenuation, i.e. dilution, sorption, transformation, depending on physico-chemical properties of the compound, such as water solubility, lipophilicity, vapour pressure, and environmental conditions, such as pH, temperature and ionic strength. A major natural attenuation process is the sorption on dissolved organic matter, colloids, suspended solids and sediments, which in turn control pharmaceuticals distribution, residence time and persistence in aquatic systems. Here we review studies of sorption capacity of natural sorbents to pharmaceuticals. These report on the importance of several environmental and sorbent-specific properties, such as the composition, quality, and amount of the sorbent, and the environmental pH, which determines the speciation of both the sorbent and compound. The importance of accounting for distribution processes on freshwater sorbents for any determination of environmental concentrations of pharmaceuticals is apparent, while the reliability of surrogate standards for measuring dissolved organic matter (DOM) distribution is evaluated in the context of the need for robust environmental risk assessment protocols.

Measurements of pre-industrial conditions are of paramount importance for understanding historical climate change. The Southern Ocean and Antarctic continent are some of the least polluted environments on planet Earth. Alkylamines can rapidly partition into aerosols, increasing their mass, as well as form new particles altogether. We demonstrate the importance of pelagic “open ocean” (OO) and sympagic “sea ice” (SI) regions in supplying distinct organic nitrogen aerosol components. In the aerosol phase, dimethylamine (DMA) and trimethylamine (TMA) are both secondary, though DMA likely originates mainly from pelagic regions, while TMA is associated mainly with sympagic regions. Parallel measurements in ice and surface waters reveal that melting sea ice contains a factor of four more TMA than coastal Antarctic Peninsula waters; and seventeen times more TMA than OO regions - suggesting additional coastal Antarctic sources. To better interpret future climate change, we recommend employing regional atmospheric chemistry models to understand these diverse aerosol sources.

This review provides a critical assessment of knowledge regarding the occurrence and behaviour of volatile, low molecular weight amines, particularly methylamines and quaternary amines, in marine aquatic systems. It provides an up-to-date evaluation of their presence within marine ecosystems, the processes likely to control their flux across the sea-air interface, and analytical techniques associated with their measurement. Interest in the occurrence and cycling of these groups of compounds in seawater has increased within the last 10–15 years, due to their potential role in climate regulation. As such, the need for wider measurements and mechanistic studies to elucidate their role within biological communities and, more widely, the nitrogen cycle and marine ecosystem models, is apparent. Finally, we make recommendations on what research questions are most suitable for future studies in this area.

Alkylamines, volatile organic nitrogen compounds with low molecular weight, are present in the surface ocean and participate in the marine biogeochemical nitrogen cycle, atmospheric chemistry and cloud formation. Alkylamines have been detected in polar regions, suggesting that these areas constitute emission hotspots of these compounds. However, knowledge of the sea surface distribution patterns and factors modulating alkylamines remain limited due to their high reactivity and low concentrations, which hamper accurate measurements. We investigated the presence and distribution of alkylamines in seawaters around the Antarctic Peninsula and the northern Weddell Sea during the late austral summer and explored their potential links to marine microbiota. Alkylamines were ubiquitous in all analysed samples, accounting for ∼ 2 % of the dissolved and particulate organic nitrogen pool. The only particulate form found was trimethylamine (TMA), detected for the first time in Antarctic waters at concentrations of 9.7 ± 4.6 nM. We efficiently measured dissolved trimethylamine (TMA, 20.9 ± 15.2 nM), dimethylamine (DMA, 32.3 ± 32.7 nM) and diethylamine (DEA, 7.2 ± 1.7 nM) across the surveyed area, while dissolved monomethylamine (MMA, 12.7 ± 0.1 nM) remained below the detection limit in most samples. Variations in alkylamine concentrations did not align with the overall phytoplankton biomass but with specific biological components. TMA was predominantly associated with, and released from, nanophytoplankton. DMA was likely produced by the degradation of TMA or trimethylamine oxide by nanophytoplankton cells or associated heterotrophic bacteria. The sources of DEA remain unclear but were suggestive of a distinct biogeochemical pathway from those of TMA and DMA. MMA is thought to primarily originate from bacterial degradation of nitrogen-based osmolytes or amino acids, but detection in too few samples precluded any robust association with microbiota. This study reveals that volatile alkylamines are widespread in Antarctic surface waters, where they are primarily sourced from nanophytoplankton cells and associated heterotrophic bacteria and protists.

Climate warming affects the development and distribution of sea ice, but at present the evidence of polar ecosystem feedbacks on climate through changes in the atmosphere is sparse. By means of synergistic atmospheric and oceanic measurements in the Southern Ocean near Antarctica, we present evidence that the microbiota of sea ice and sea ice-influenced ocean are a previously unknown significant source of atmospheric organic nitrogen, including low molecular weight alkyl-amines. Given the keystone role of nitrogen compounds in aerosol formation, growth and neutralization, our findings call for greater chemical and source diversity in the modelling efforts linking the marine ecosystem to aerosol-mediated climate effects in the Southern Ocean.

Artificial soils made from waste materials offer an alternative to imported natural topsoils, notably in large-scale groundwork and reclamation projects. Benefits include diversion of waste from landfill and recycling. Nonetheless, there is limited information on the characteristics needed to support plant growth in the long term, particularly the existence of a sustainable nitrogen reservoir. Therefore, we assessed the efficacy of nitrogen cycling and retention within an artificial soil composed of 25% sand, 10% clay, 32.5% composted bark and 32.5% composted green waste over 52 weeks. Leachate was analysed for nitrogen species and nitrogen concentrations, and two of the soil columns had fertiliser added after 26 and 48 weeks. Results show that nitrate concentrations decreased from 6.73 to 0.36 mg N L−1 after 2 weeks, due to poor retention of this anion in soil, and remained low for 6 months, before increasing up to 5.87 mg N L−1 after week 26. This sharp increase in dissolved nitrate was preceded by a decrease in the ratio of dissolved organic carbon to dissolved organic nitrogen in the soil leachate. This finding indicates that the soil had become carbon-limited, leading to mineralisation of organic nitrogen by soil organisms and excretion of nitrogen. We also found that fertilisation of the soil did not alleviate carbon limitation and nitrogen loss was greater in fertilised soils, indicating nitrogen saturation. After the onset of carbon limitation, the dissolved nitrate concentrations in both the fertilised and unfertilised soils were close to exceeding the European Union threshold of concern for nitrate groundwater and river pollution. Thus, while the deployment of artificial soils is a viable option for landscaping projects, loss of nitrogen may be environmentally significant and soil management protocols must take account of both the carbon and nitrogen status of the substrate.

Contamination of surface waters by pharmaceuticals is now widespread. There are few data on their environmental behaviour, particularly for those which are cationic at typical surface water pH. As the external surfaces of bacterio-plankton cells are hydrophilic with a net negative charge, it was anticipated that bacterio-plankton in surface-waters would preferentially remove the most extensively-ionised cation at a given pH. To test this hypothesis, the persistence of four, widely-used, cationic pharmaceuticals, chloroquine, quinine, fluphenazine and levamisole, was assessed in batch microcosms, comprising water and bacterio-plankton, to which pharmaceuticals were added and incubated for 21 days. Results show that levamisole concentrations decreased by 19 % in microcosms containing bacterio-plankton, and by 13 % in a parallel microcosm containing tripeptide as a priming agent. In contrast to levamisole, concentrations of quinine, chloroquine and fluphenazine were unchanged over 21 days in microcosms containing bacterio-plankton. At the river-water pH, levamisole is 28 % cationic, while quinine is 91–98 % cationic, chloroquine 99 % cationic and fluphenazine 72–86 % cationic. Thus, the most neutral compound, levamisole, showed greatest removal, contradicting the expected bacterio-plankton preference for ionised molecules. However, levamisole was the most hydrophilic molecule, based on its octanol–water solubility coefficient ( K ow ). Overall, the pattern of pharmaceutical behaviour within the incubations did not reflect the relative hydrophilicity of the pharmaceuticals predicted by the octanol–water distribution coefficient, D ow , suggesting that improved predictive power, with respect to modelling bioaccumulation, may be needed to develop robust environmental risk assessments for cationic pharmaceuticals.

We report the first data for atrazine removal in low-turbidity freshwaters. Atrazine is a globally applied herbicide, contamination by which may lead to direct and indirect ecotoxicological impacts. Although a common contaminant of surface waters, microbial biodegradation of atrazine in this environment has been little studied, with most work focused on soils by means of selected, atrazine-degrading bacteria-enriched cultures. Here, we measured atrazine removal from river water using a batch incubation system designed to represent environmental conditions, with water from two contrasting UK rivers, the Tamar and Mersey. Atrazine and bacterial inocula prepared from the source water were added to cleaned river water for 21-day incubations that were analysed directly by electrospray ionisation-mass spectrometry. The experimental approach was validated using peptides of different molecular mass. Results show that atrazine concentrations decreased by 11% over 21 days in Tamar samples, a rural catchment with low population density, when atrazine was the only substrate added. In contrast no removal was evident in Mersey samples, an urban catchment with high population density. When a tripeptide was added as a co-substrate, atrazine removal in the Tamar water remained at 11% while that for the Mersey water increased from 0 to 37%. Although degradation of atrazine in aerobic freshwaters is predicted according to its chemical structure, our data suggest that the composition of the bacterial population determines whether removal occurs under these conditions and at these environmentally realistic concentrations.

Previous measurements of the benthic nitrogen (N) flux from resuspended estuarine particles in the Thames Estuary appeared to underestimate benthic inputs. This study attempted to address experimental limitations by using a mini-annular flume. The flume has a 45 l capacity and was prepared in order to facilitate trace chemical analysis of N. Sediment (S1) and suspended particulate material (SPM; S2) were collected from the Tamar Estuary, UK, and added to prepared, low-N, freshwater and seawater solutions to give a final particle concentration of 500 mg l −1 . Two tidal cycles were simulated and SPM and total dissolved N (TDN) were measured at a range of turbulent shear stresses (0.06–0.9 Pa) representative of the sampling sites. A large increase in TDN concentration was measured after particle addition and initial mixing, due to release of loosely bound particulate N (PN). The TDN concentration increased as the experiment progressed (up to 12 μM), but did not appear to be systematically linked to either salinity or SPM concentration. The flume system and experimental protocol provided reproducible physical data and low detection limits for TDN, which demonstrates its potential for studying relationships between estuarine particle transport and macronutrient cycles.

Suspended particulate matter (SPM) is a key component regulating the biogeochemistry of natural and contaminant moieties in estuaries. Individual particle analyses can complement conventional bulk analyses of SPM, but are rarely undertaken. This study used scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS) of particles to quantify a range of elements in the reference estuarine sediment PACS-2. This approach was compared with a bulk SPM analysis based on inductively coupled plasma-atomic emission spectrometry (ICP-AES). The median concentrations of Al, Fe, Mg, and Ca for the two approaches were similar, and accuracy for both methods was good. SEM-EDS analysis was also satisfactory for K. Agreement was poorer for Mn and Ti, which were present at trace concentrations. Increasing the number of particles examined by SEM-EDS should improve the analysis. SEM-EDS analysis of SPM from the Tamar Estuary, UK, revealed marked geochemical differences between particle sub-populations.