Hg bioavailability and impact on bacterial communities in a long-term polluted soil

Different soil samples characterised by a long-term Hg-pollution were studied for Hg total content, fractionation, phytotoxicity and influence on the bacterial community. Hg pollution ranged from 1 to 50 mg kg(-1) and most of it was speciated in scarcely soluble forms. In agreement with this, the biochemical quality indexes were investigated (biomass, enzyme activities) and the bacterial community (viable heterotrophic (VH) bacteria, functional diversity) apparently was not influenced by the degree of Hg pollution. In particular, the investigated soils exhibited a low percentage of Hg-resistant (Hg(R)) bacteria ranging from less than 0.001% to 0.25% of the VH and the addition of available Hg in the form of HgCl(2) induced an enrichment of resistant Hg(R) populations. The general biodiversity of the bacterial community was evaluated by denaturing gradient gel electrophoresis of DNA of Hg spiked soil microcosms and of control soils. Hg(R) bacteria capable to grow in a minimal medium containing HgCl(2) were also isolated and identified. MerA and merB gene PCR fragments were obtained from different Hg(R) strains and the range of similarities at the DNA level and at the deduced amino acid level showed that they carried mercuric reductase and lyase. Differently from bacteria, some influence of soil Hg content on seeds' germination and root elongation was observed for Lepidium sativum L. and Solanum lycopersicum L. In conclusion, most of the Hg in these long-term polluted soils was scarcely mobile and available and did not significantly influence the soil bacterial community. The risk of potential Hg remobilization over time, that could be naturally favoured by the activity of plant roots or other inorganic processes occurring in soil, can be extenuated since bacterial community was resistant and resilient to subsequent Hg stress.     

Presence and partitioning properties of the flame retardants pentabromotoluene, pentabromoethylbenzene and hexabromobenzene near suspected source zones in Norway

The brominated flame retardants (BFRs), pentabromotoluene (PBT), pentabromoethylbenzene (PBEB) and hexabromobenzene (HBB), exhibit physical-chemical properties similar to other persistent organic pollutants, and have been in use as flame retardants for several decades. Data on these BFRs in diverse environmental samples can be found in studies from the 1970s and 1980s, as well as in recent years, though very little in the years in between. Due to a lack of data, the cause for the apparent re-emergence of these BFRs in recent studies is unclear, and could reflect changes in production volumes, accumulation of transformation products from BFR precursors, improved analytical techniques or simply a re-emergence in concern. Very little data are available on their environmentally relevant partitioning properties, which could help to explain the occurrence and fate of these BFRs. In this study we analysed for the presence of HBB, PBT, and PBEB in diverse environmental samples from potential Norwegian BFR source zones. Additionally, environmental partitioning properties of these BFRs as well as brominated benzenes were estimated and validated using experimental data for brominated benzenes. Of the three BFRs, HBB was identified in detectable quantities at most source zones, PBEB only near a metal recycling factory, and PBT only in a few additional locations from where PBEB was detected. Data from this study show that HBB is likely widely distributed, as verified both by chemical analysis and estimated properties. Measured HBB levels in wastewater treatment plants indicate that the treatment practices used in the study locations are not effective at lowering HBB levels, perhaps due to association with low density suspended solids (e.g. microplastics).     

Characterization of PM10-bound polycyclic aromatic hydrocarbons in the ambient air of Spanish urban and rural areas

Urban areas constitute major pollution sources due to anthropogenic activities located in these areas. Among the legislated air pollutants, the particulate matter with an aerodynamic diameter less than or equal to 10 microns (PM10) and polycyclic aromatic hydrocarbons (PAH) are controlled under Directive 2008/50/EC and Directive 2004/107/EC, respectively due to their adverse health effects. A study was carried out at four urban and rural Spanish areas during the warm and cold seasons in 2008-2009 to quantify 19 PAH associated with the atmospheric PM10 by gas chromatography-mass spectrometry-mass spectrometry detection (GC-MS-MS) with the internal standard method. The particle-bound composition of the analysed PAH was 5 and 10 times greater in industrial and urban areas, respectively when compared to those measured in rural areas. The highest PAH concentrations during the cold period were possibly due to the additional contribution of domestic heating sources and meteorological conditions such as low temperature and solar irradiation. The use of molecular diagnostic ratios indicated that the possible, major PAH pollution sources in the most polluted areas were pyrogenic sources, mainly attributed to petroleum combustion sources (motor vehicle emissions and crude oil combustion). Petrogenic sources related to evaporative emissions also seemed to contribute in the most polluted area during the warm period. Those dates with high carcinogenic character according to the benzo(a)pyrene equivalent (BaP-eq) were also possibly attributed to petroleum combustion sources.     

Optical fiber based methodology for assessment of thiocyanate in seawater

A new methodology for the assessment of thiocyanate (SCN(-)) is proposed based on optical fiber (OF) detection coupled to a liquid chromatography system (LC). The developed methodology showed an adequate performance for the analysis of SCN(-) comparable to a high performance liquid chromatography with UV detector (HPLC-UV) methodology: a detection limit of 3 μg L(-1), a linear range from 4 to 400 μg L(-1), and an analytical time of less than 6 min. The OF based methodology was of compact design and easy operation. This simple system has the potential to be used as a sensing approach for SCN(-) in seawater.     

Spatial distributions and eco-partitioning of soil biogeochemical properties in the Everglades National Park

Large-scale ecosystem restoration efforts, such as those in the Florida Everglades, can be long-term and resource intensive. To gauge success, restoration efforts must have a means to evaluate positive or negative results of instituted activities. Edaphic properties across the Everglades landscape have been determined to be a valuable metric for such evaluation, and as such, a baseline condition from which to make future comparisons and track ecosystem response is necessary. The objectives of this work were to document this baseline condition in the southern most hydrologic unit of the Everglades, Everglades National Park (ENP), and to determine if significant eco-partitioning of soil attributes exists that would suggest the need to focus monitoring efforts in particular eco-types within the ENP landscape. A total of 342 sites were sampled via soil coring and parameters such as total phosphorus (TP), total nitrogen (TN), total carbon (TC), total calcium, total magnesium, and bulk density were measured at three depth increments in the soil profile (floc, 0-10 cm, and 10-20 cm). Geostatistical analysis and GIS applications were employed to interpolate site-specific biogeochemical properties of soils across the entire extent of the ENP. Spatial patterns and eco-type comparisons suggest TC and TN to be highest in Shark River Slough (SRS) and the mangrove interface (MI), following trends of greatest organic soil accumulation. However, TP patterns suggest greatest storages in MI, SRS, and western marl and wet prairies. Eco-partitioning of soil constituents suggest local drivers of geology and hydrology are significant in determining potential areas to focus monitoring for future change detection.     

Dietary exposure of three passerine species to PCDD/DFs from the Chippewa, Tittabawassee, and Saginaw River floodplains, Midland, Michigan, USA

Dietary exposure of house wrens (Troglodytes aedon), tree swallows (Tachycineta bicolor), and eastern bluebirds (Sialia sialis) to polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs) near Midland, Michigan (USA) was evaluated based on site-specific data, including concentrations of residues in bolus samples and individual invertebrate orders and dietary compositions by study species. Site-specific dietary compositions for the three species were similar to those reported in the literature, but differed in their relative proportions of some dietary items. Oligocheata (non-depurated) and Brachycera (Diptera) contained the greatest average concentrations of ??PCDD/DFs of the major site-specific dietary items collected via food web-based sampling. Average ingestion values of ??PCDD/DFs from site-specific bolus-based and food web-based dietary concentrations for nestlings at study areas (SAs) were 6- to 20-fold and 2- to 9-fold greater than at proximally located reference areas (RAs), respectively. Average ingestion values of total 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQ_WHO???Avian) from site-specific bolus-based and food web-based dietary concentrations for nestlings at SAs were 31- to 121-fold and 9- to 64-fold greater than at proximally located RAs, respectively. Estimates of ??PCDD/DFs and TEQ_WHO???Avian tissue concentrations based on nestling dietary exposures were greater than those measured. Plausible explanations include nestling metabolism of 2,3,7,8-tetrachlorodibenzofuran and assimilation rates of less than the 70% assumed to occur over the nestling growth period. Profiles of the relative concentrations of individual PCDD/DF congeners in samples of invertebrates and bolus at SAs on the Tittabawassee River downstream of the source of contamination were dominated by 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin (22% to 44%) and 2,3,7,8-tetrachlorodibenzofuran (18% to 50%).     

Hydrologic disturbance reduces biological integrity in urban streams

The impact of urbanization on stream ecosystems is linked by land cover changes to the alteration of the natural hydrology and subsequent physical disruption of stream biota and habitat. Seasonal floods are part of the natural disturbance regime of many streams, but urbanization increases their frequency and magnitude. This study evaluated the impact of hydrologic disturbance on fish and aquatic macroinvertebrates in 81 (56 urban/25 reference) Ohio streams. Hydrologic variables included annual and monthly 24-h rainfall maxima and computed annual peak discharge, with computation supported by GIS-based drainage area delineation and land cover characterization. Ohio biological criteria for fish and macroinvertebrates measured during the late spring and summer were negatively impacted by annual peak discharge in urban streams as compared to reference streams. Results support the application of stormwater best management practices as part of stream restoration efforts to mitigate urbanization impacts to fish and macroinvertebrates.     

The fate of steroid estrogens: partitioning during wastewater treatment and onto river sediments

The partitioning of steroid estrogens in wastewater treatment and receiving waters is likely to influence their discharge to, and persistence in, the environment. This study investigated the partitioning behaviour of steroid estrogens in both laboratory and field studies. Partitioning onto activated sludge from laboratory-scale Husmann units was rapid with equilibrium achieved after 1 h. Sorption isotherms and Kd values decreased in the order 17??-ethinyl estradiol > 17??-estradiol > estrone > estriol without a sorption limit being achieved (1/n?>1). Samples from a wastewater treatment works indicated no accumulation of steroid estrogens in solids from primary or secondary biological treatment, however, a range of steroid estrogens were identified in sediment samples from the River Thames. This would indicate that partitioning in the environment may play a role in the long-term fate of estrogens, with an indication that they will be recalcitrant in anaerobic conditions.     

Spatial and seasonal distribution of nitrate-N in groundwater beneath the rice�Cwheat cropping system of India: a geospatial analysis

Increased use of nitrogenous fertilizers in the intensively cultivated rice (Oryza sativa)?Cwheat (Triticum aestivum) cropping system (covers a 13.5-ha m area in South Asia) has led to the concentration of nitrates (NO₃-N) in the groundwater (GW) in Haryana State of India. Six districts from the freshwater zone were selected to identify factors affecting NO₃-N enrichment in GW. Water and soil samples were collected from 1,580 locations and analyzed for their chemical properties. About 3% (26,796, and 10,588 ha) of the area was estimated to be under moderately high (7.5?C10 mg l^???1) and high (>10 mg l^???1) risk categories, respectively. The results revealed that NO₃-N was 10?C50% higher during the pre-monsoon season than in the monsoon season. Nitrate-N decreased with the increase in aquifer depth (r ²?=?0.99). Spatial and proximity analyses using ArcGIS (9.2) revealed that (1) clay material in surface and sub-surface texture restricts N leaching, (2) piedmont and rolling plains act as an N sink, and (3) perennial rivers bring a dilution effect whereas seasonal rivers provide favorable conditions for NO₃ ^? enrichment. The study concludes that chemical N fertilizers applied in agro-ecosystems are not the sole factor determining the NO₃ in groundwater; rather, it is an integrated process governed by several other factors including physical and chemical properties of soils, proximity and type of river, and geomorphologic and geographical aspects. Therefore, future studies should adopt larger area (at least watershed scale) to understand the mechanistic pathways of NO₃ enrichment in groundwater and interactive role of the natural drainage system and surrounding physical features. In addition, the study also presents a conceptual framework to describe the process of nitrate formation and leaching in piedmont plains and its transportation to the mid-plain zone.     

First observation of different diffusion coefficients for two conformers in a neat liquid

 Self-diffusion coefficients were studied for the highly polar liquid N-methylformamide at pressures up to 200 MPa between the melting pressure curves and 420 K by the spin-echo method. N-Methylformamide exists as a mixture of two conformers in the neat liquid. These conformers have large differences at lower temperatures in their dynamic and structural properties. The self-diffusion coefficient of the cis-conformer being 17% lower than that of the trans-conformer at the same T and p. This is the first observation of such an effect. The experimental study is supported by Monte Carlo (MC) calculations which show that the first neighbors around a cis conformer are arranged differently than in an all trans liquid. The difference leads in the simulations to a much lower dielectric constant for the trans-cis mixture and might also explain the retardation of diffusion for the cis conformer. Received: 15 November 1999 / Accepted in revised form: 28 February 2000