Nitrate reduction during ground-water recharge, Southern High Plains, Texas

In arid and semi-arid environments, artificial recharge or reuse of wastewater may be desirable for water conservation, but NO₃⁻ contamination of underlying aquifers can result. On the semi-arid Southern High Plains (USA), industrial wastewater, sewage, and feedlot runoff have been retained in dozens of playas, depressions that focus recharge to the regionally important High Plains (Ogallala) aquifer. Analyses of ground water, playa-basin core extracts, and soil gas in an 860-km² area of Texas suggest that reduction during recharge limits NO₃⁻ loading to ground water. Tritium and Cl⁻ concentrations in ground water corroborate prior findings of focused recharge through playas and ditches. Typical δ¹⁵N values in ground water (>12.5‰) and correlations between δ¹⁵N and ln C_NO⁻3–N suggest denitrification, but O₂ concentrations ≥3.24 mg l⁻¹ indicate that NO₃⁻ reduction in ground water is unlikely. The presence of denitrifying and NO₃⁻-respiring bacteria in cores, typical soil–gas δ¹⁵N values <0‰, and decreases in NO₃⁻–N/Cl⁻ and SO₄²⁻/Cl⁻ ratios with depth in cores suggest that reduction occurs in the upper vadose zone beneath playas. Reduction may occur beneath flooded playas or within anaerobic microsites beneath dry playas. However, NO₃⁻–N concentrations in ground water can still exceed drinking-water standards, as observed in the vicinity of one playa that received wastewater. Therefore, continued ground-water monitoring in the vicinity of other such basins is warranted.     

Applying DPSIR to sustainable development

The DPSIR framework was devised in the late 1990s as a tool for the reporting and analysis of environmental problems, ranging in scale from global systems to localized watersheds. Since then, international organizations have begun to apply this framework to the evaluation of sustainable development initiatives, to better understand and overcome barriers to sustainability. While this may seem a logical application for an integrated environmental assessment tool, the use of DPSIR in sustainable development will likely perpetuate the least satisfactory outcomes of development. DPSIR cannot address the impact of aggregated, informal responses on the drivers and pressures related to environmental problems and sustainability challenges. This problem is not merely an oversight of the framework, but an issue that emerges within the structure of DPSIR itself through the unexamined, unacknowledged hierarchy of actors that this framework implicitly creates with its typology. Therefore, a DPSIR-centered approach is not a new direction for development within international organizations, but instead, a reproduction of existing inequalities between actors and stakeholders within current approaches.     

Habitat preferences of coral-associated fishes are altered by short-term exposure to elevated CO2

Rising atmospheric carbon dioxide (CO₂) concentrations are causing additional CO₂ to be absorbed by the oceans. Recent studies show that exposure to elevated CO₂ causes olfactory impairment in reef fishes; however, the ecological consequences of this impairment are largely unknown. This study examined the effects of short-term exposure to elevated CO₂ on habitat preferences of coral-dwelling gobies. Adult gobies collected from the reef at Lizard Island (Great Barrier Reef, Australia) were exposed for 4 days to ambient CO₂ (440 μatm) or elevated CO₂ (880 μatm). Habitat preferences were then tested in laboratory and field experiments at ambient conditions. In olfactory preference tests, Paragobiodon xanthosomus displayed a strong preference for odour cues of their sole host coral Seriatopora hystrix; however, this preference was absent in gobies exposed to elevated CO₂. Habitat choice experiments conducted in the field showed that Gobiodon histrio placed on dead coral colonies located preferred live habitat within 24 h; however, gobies exposed to elevated CO₂ associated with both preferred and non-preferred habitats in approximately equal frequency. Preferred habitats are known to confer fitness advantages to coral-dwelling gobies. Consequently, these results suggest that future elevated CO₂ levels might affect the ability of habitat specialist fishes to select favourable habitats.     

Towards improved socio-economic assessments of ocean acidification’s impacts

Ocean acidification is increasingly recognized as a component of global change that could have a wide range of impacts on marine organisms, the ecosystems they live in, and the goods and services they provide humankind. Assessment of these potential socio-economic impacts requires integrated efforts between biologists, chemists, oceanographers, economists and social scientists. But because ocean acidification is a new research area, significant knowledge gaps are preventing economists from estimating its welfare impacts. For instance, economic data on the impact of ocean acidification on significant markets such as fisheries, aquaculture and tourism are very limited (if not non-existent), and non-market valuation studies on this topic are not yet available. Our paper summarizes the current understanding of future OA impacts and sets out what further information is required for economists to assess socio-economic impacts of ocean acidification. Our aim is to provide clear directions for multidisciplinary collaborative research.     

某滑坡坝坝后稳定性分析

某滑坡坝位于某拟建水电站的上游,在国家级自然保护区内,是著名的旅游景点,其安全性对旅游开发、工程建设和下游居民生命财产安全影响很大,为了评价该滑坡坝的稳定性,需要对其发生洪水漫坝和渍坝的可能性进行研究,论证其安全性。通过计算的各种工况表明,滑坡坝坝后(坝体靠下游部分)是稳定的,对电站建设和下游居民不会产生威胁,滑坡坝是稳定的,可以进行综合开发。本文研究思路对类似工程有一定的借鉴意义。     

Comparison of white-footed mice and rice rats as biomonitors of polychlorinated biphenyl and metal contamination

A study was conducted to assess differences in contaminant assimilation among co-occurring white-footed mice (Peromyscus leucopus) and rice rats (Oryomys palustris) captured at a contaminated site. Rodents were collected from five areas at the Paducah Gaseous Diffusion Plant (PGDP), a uranium enrichment facility. Relatively few white-footed mice (8.7%) had quantifiable concentrations of PCBs compared to 42% of rice rats (chi2 = 6.49, d.f. = 1, P < 0.025), and seven of the 11 rice rats (64%) over 50 g body mass had quantifiable concentrations of PCBs in their livers. White-footed mice had higher mean concentrations of barium (P < 0.0001), chromium (P = 0.0010), copper (P = 0.0011), lead (P = 0.0335), and aluminum (P = 0.0006) than rice rats at all five sampling areas. Species-specific differences in accumulation of PCBs and metals were observed and attributed to differences in habitat use and foraging strategies.     

Kenneth Mellanby Review Award. Trace metal concentrations in aquatic invertebrates: why and so what?

All aquatic invertebrates take up and accumulate trace metals whether essential or not, and subsequent body concentrations of trace metals show enormous variability across metals and invertebrate taxa. Accumulated metal concentrations are interpreted in terms of different trace metal accumulation patterns, dividing accumulated metals into two components--metabolically available metal and stored detoxified metal. Crustaceans are used as examples of different accumulation patterns that will have a general applicability to all aquatic invertebrates. Toxicity is related to a threshold concentration of metabolically available metal and not to total accumulated metal concentration. The significance of accumulated metal concentrations is discussed in terms of the biological significance, including the attempted recognition of a high or low concentration, and of the applied use of aquatic invertebrates in biomonitoring programmes assessing geographical and temporal variation in trace metal bioavailabilities in aquatic systems.     

Development and laboratory performance evaluation of a personal cascade impactor

This paper presents the design and laboratory evaluation of a personal cascade impactor. The system is compact, lightweight, and uses a single battery-operated sampling pump. It operates at a flow rate of 5 L/min and consists of four impaction stages, each equipped with slit-shaped acceleration nozzles, and a backup filter. The impactor was calibrated using polydisperse particles. The 50% cut points of the four stages were 9.6, 2.6, 1.0, and 0.5 microm, respectively. The backup filter is placed downstream of the fourth stage and is used to collect the particles with an aerodynamic diameter smaller than 0.5 microm (dp < 0.5 microm). The major feature of this novel sampler is its ability not only to fractionate the particles with an aerodynamic diameter smaller than 10 microm to the various size fractions, but also to collect them onto relatively small polyurethane foam substrates without using adhesives. Although the impaction substrates are not coated with adhesives such as grease or mineral oil, particle bounce and re-entrainment losses were found to be insignificant. Interstage losses of particles smaller than 0.5 microm were less than 10%; for fine particles, less than 5%; and for coarse particles, less than 12%. The pressure drop across the four stages and the backup filter were 0.015 kPa (0.153 cm H2O),0.025 kPa (0.255 cm H2O), 0.274 kPa (2.794 cm H2O), 0.323 kPa (3.294 cm H2O), and 0.370 kPa (3.773 cm H2O), respectively. Particles can be easily recovered from the foam substrates using aqueous extraction.     

Identification of sources contributing to Mid-Atlantic regional aerosol

Source types or source regions contributing to the concentration of atmospheric fine particles measured at Brigantine National Wildlife Refuge, NJ, were identified using a factor analysis model called Positive Matrix Factorization (PMF). Cluster analysis of backward air trajectories on days of high- and low-factor concentrations was used to link factors to potential source regions. Brigantine is a Class I visibility area with few local sources in the center of the eastern urban corridor and is therefore a good location to study Mid-Atlantic regional aerosol. Sulfate (expressed as ammonium sulfate) was the most abundant species, accounting for 49% of annual average fine mass. Organic compounds (22%; expressed as 1.4 x organic carbon) and ammonium nitrate (10%) were the next abundant species. Some evidence herein suggests that secondary organic aerosol formation is an important contributor to summertime regional aerosol. Nine factors were identified that contributed to PM2.5 mass concentrations: coal combustion factors (66%, summer and winter), sea salt factors (9%, fresh and aged), motor vehicle/mixed combustion (8%), diesel/Zn-Pb (6%), incinerator/industrial (5%), oil combustion (4%), and soil (2%). The aged sea salt concentrations were highest in springtime, when the land breeze-sea breeze cycle is strongest. Comparison of backward air trajectories of high- and low-concentration days suggests that Brigantine is surrounded by sources of oil combustion, motor vehicle/mixed combustion, and waste incinerator/industrial emissions that together account for 17% of PM2.5 mass. The diesel/Zn-Pb factor was associated with sources north and west of Brigantine. Coal combustion factors were associated with coal-fired power plants west and southwest of the site. Particulate carbon was associated not only with oil combustion, motor vehicle/mixed combustion, waste incinerator/industrial, and diesel/Pb-Zn, but also with the coal combustion factors, perhaps through common transport.     

Portable X-ray fluorescence in the characterisation of arsenic contamination associated with industrial buildings at a heritage arsenic works site near Redruth,Cornwall, UK

An investigation using in situ analysis by portable X-ray fluorescence (PXRF) has shown that contamination present on industrial buildings at a heritage arsenic works site near Redruth, Cornwall, UK results from the absorption of arsenic by porous and semi-porous building materials that were in contact with arsenic-rich flue gases. Results from a preliminary survey indicate that arsenic remains locked in these materials and is being gradually leached out by weathering processes. This weathering causes general contamination of the adjacent building surfaces averaging 1845 microg g(-1) arsenic, presumably caused by evaporation of leach solutions in contact with air at the surface of the building materials. More extensive crystalline deposits were found under arches protected from dissolution and further dispersion by rain water. These deposits appeared to comprise calcium sulfate (gypsum), associated with on average between 1.2 and 6.8% m/m As. In situ PXRF proved to be highly effective in locating sources of contamination at the site and in providing data that allowed a hypotheses for the origin of this contamination to be formulated and tested in the field.