Emerging pollutants reach the environment from various anthropogenic sources and are distributed throughout environmental matrices. Although great advances have been made in the detection and analysis of trace pollutants during recent decades, due to the continued development and refinement of specific techniques, a wide array of undetected contaminants of emerging environmental concern need to be identified and quantified in various environmental components and biological tissues. These pollutants may be mobile and persistent in air, water, soil, sediments and ecological receptors even at low concentrations. Robust data on their fate and behaviour in the environment, as well as on threats to ecological and human health, are still lacking. Moreover, the ecotoxicological significance of some emerging micropollutants remains largely unknown, because satisfactory data to determine their risk often do not exist. This paper discusses the fate, behaviour, (bio)monitoring, environmental and health risks associated with emerging chemical (pharmaceuticals, endocrine disruptors, hormones, toxins, among others) and biological (bacteria, viruses) micropollutants in soils, sediments, groundwater, industrial and municipal wastewaters, aquaculture effluents, and freshwater and marine ecosystems, and highlights new horizons for their (bio)removal. Our study aims to demonstrate the imperative need to boost research and innovation for new and cost-effective treatment technologies, in line with the uptake, mode of action and consequences of each emerging contaminant. We also address the topic of innovative tools for the evaluation of the effects of toxicity on human health and for the prediction of microbial availability and degradation in the environment. Additionally, we consider the development of (bio)sensors to perform environmental monitoring in real-time mode. This needs to address multiple species, along with a more effective exploitation of specialised microbes or enzymes capable of degrading endocrine disruptors and other micropollutants. In practical terms, the outcomes of these activities will build up the knowledge base and develop solutions to fill the significant innovation gap faced worldwide.

No abstract

Biodegradation is one of the most favored and sustainable means of removing organic pollutants from contaminated aquifers but the major steering factors are still surprisingly poorly understood. Growing evidence questions some of the established concepts for control of biodegradation. Here, we critically discuss classical concepts such as the thermodynamic redox zonation, or the use of steady state transport scenarios for assessing biodegradation rates. Furthermore, we discuss if the absence of specific degrader populations can explain poor biodegradation. We propose updated perspectives on the controls of biodegradation in contaminant plumes. These include the plume fringe concept, transport limitations, and transient conditions as currently underestimated processes affecting biodegradation.

The phenylurea herbicides are an important group of pesticides used extensively for pre- or post-emergence weed control in cotton, fruit and cereal crops worldwide. The detection of phenylurea herbicides and their metabolites in surface and ground waters has raised the awareness of the important role played by agricultural soils in determining water quality. The degradation of phenylurea herbicides following application to agricultural fields is predominantly microbial. However, evidence suggests a slow degradation of the phenyl ring, and substantial spatial heterogeneity in the distribution of active degradative populations, which is a key factor determining patterns of leaching losses from agricultural fields. This review summarises current knowledge on the microbial metabolism of isoproturon and related phenylurea herbicides in and below agricultural soils. It addresses topics such as microbial degradation of phenylurea herbicides in soil and subsurface environments, characteristics of known phenylurea-degrading soil micro-organisms, and similarities between metabolic pathways for different phenylurea herbicides. Finally, recent studies in which molecular and microbiological techniques have been used to provide insight into the in situ microbial metabolism of isoproturon within an agricultural field will be discussed.

A soil bacterium (designated strain SRS2) able to metabolize the phenylurea herbicide isoproturon, 3-(4-isopropylphenyl)-1,1-dimethylurea (IPU), was isolated from a previously IPU-treated agricultural soil. Based on a partial analysis of the 16S rRNA gene and the cellular fatty acids, the strain was identified as a Sphingomonas sp. within the ␣-subdivision of the proteobacteria. Strain SRS2 was able to mineralize IPU when provided as a source of carbon, nitrogen, and energy. Supplementing the medium with a mixture of amino acids considerably enhanced IPU mineralization. Mineralization of IPU was accompanied by transient accumulation of the metabolites 3-(4-isopropylphenyl)-1-methylurea, 3-(4-isopropylphenyl)-urea, and 4-isopropyl-aniline identified by high-performance liquid chromatography analysis, thus indicating a metabolic pathway initiated by two successive N-demethylations, followed by cleavage of the urea side chain and finally by mineralization of the phenyl structure. Strain SRS2 also transformed the dimethylurea-substituted herbicides diuron and chlorotoluron, giving rise to as-yet-unidentified products. In addition, no degradation of the methoxy-methylurea-substituted herbicide linuron was observed. This report is the first characterization of a pure bacterial culture able to mineralize IPU.The phenylurea herbicide isoproturon, 3-(4-isopropylphenyl)-1,1-dimethylurea (IPU), which is used for pre-and postemergence control of annual grasses and broad-leaved weeds in wheat, rye, and barley crops, is among the most extensively used pesticides in conventional agriculture in Europe (34). Ecotoxicological data suggest that IPU and some of its metabolites are harmful to aquatic invertebrates (20), freshwater algae (25), and microbial activity (28). IPU is also suspected of being carcinogenic (2, 14). As a result of its widespread and repeated use, IPU is frequently detected in groundwater and surface waters in Europe in levels exceeding the European Commission drinking water limit of 0.1 g l Ϫ1 (23,33,34). Degradation of IPU in agricultural soils occurs predominantly by microbiological processes (6,22). Several studies have demonstrated a slow natural attenuation rate in various soils and subsurface environments with respect to mineralization of the phenyl structure (4,15,17,18,26,35). The detection of IPU as an environmental pollutant and its apparently low mineralization potential has stimulated research aimed at isolating and characterizing microbial cultures able to mineralize IPU. Enrichment culture techniques have been used with varied success in attempts to isolate IPU-degrading microorganisms. In previous studies, slurries of mineral media and soils from different agricultural fields failed to degrade IPU (4,19,35). Enrichment on the IPU metabolite 3-(4-isopropylphenyl)-1-methylurea (MDIPU) as the sole source of carbon and energy recently yielded a mixed bacterial culture able to perform growth-linked mineralization of MDIPU and 4-isopropylaniline (4IA) but with no degradation activity toward IPU (35)....

No abstract

No abstract

Substantial spatial variability in the degradation rate of the phenyl-urea herbicide isoproturon (IPU) [3-(4-isopropylphenyl)-1,1-dimethylurea] has been shown to occur within agricultural fields, with implications for the longevity of the compound in the soil, and its movement to ground-and surface water. The microbial mechanisms underlying such spatial variability in degradation rate were investigated at Deep Slade field in Warwickshire, United Kingdom. Most-probable-number analysis showed that rapid degradation of IPU was associated with proliferation of IPU-degrading organisms. Slow degradation of IPU was linked to either a delay in the proliferation of IPU-degrading organisms or apparent cometabolic degradation. Using enrichment techniques, an IPU-degrading bacterial culture (designated strain F35) was isolated from fast-degrading soil, and partial 16S rRNA sequencing placed it within the Sphingomonas group. Denaturing gradient gel electrophoresis (DGGE) of PCR-amplified bacterial community 16S rRNA revealed two bands that increased in intensity in soil during growth-linked metabolism of IPU, and sequencing of the excised bands showed high sequence homology to the Sphingomonas group. However, while F35 was not closely related to either DGGE band, one of the DGGE bands showed 100% partial 16S rRNA sequence homology to an IPU-degrading Sphingomonas sp. (strain SRS2) isolated from Deep Slade field in an earlier study. Experiments with strains SRS2 and F35 in soil and liquid culture showed that the isolates had a narrow pH optimum (7 to 7.5) for metabolism of IPU. The pH requirements of IPU-degrading strains of Sphingomonas spp. could largely account for the spatial variation of IPU degradation rates across the field.Concern about the environmental impact of pesticides most frequently arises from their ability to leach from soil and contaminate water resources. The phenyl-urea herbicides are of particular significance in this respect, since several members of the group, including isoproturon (IPU) [3-(4-isopropylphenyl)-1,1-dimethylurea] and diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] are degraded slowly in soil and are susceptible to leaching. As a result, IPU and diuron are frequently detected as contaminants of agricultural catchments in Europe (23).Studies of the fate of IPU in agricultural fields on contrasting soil types have revealed considerable spatial variability in degradation rates across fields (2,26,27). At two such sites in the United Kingdom, Deep Slade field in Warwickshire and Brimstone farm in Oxfordshire, IPU half-life in soil was found to vary between 6 and 30 days, with degradation rate linked to soil pH. Further studies by Bending et al. (3) demonstrated that soil pH controlled the ease of induction of growth-linked metabolism, with slow degradation rates at lower soil pH linked to apparent cometabolic degradation of the compound. At the Deep Slade site, various bacteria capable of degrading IPU have been isolated (8,19,21). However, the relative importance of each in the degradation...