The effects of salt exclusion during ice formation on circulation in lakes

Laboratory experiments have been performed to investigate the effects of salt exclusion on the behaviour of lakes with salinities up to 8 g L^?1. At these salinities the freezing temperature is less than the temperature of maximum density and, unlike sea-ice, a reverse temperature stratification forms beneath the ice that can support at least some of the excluded salt. Temperature time series at four depths showed that salt exclusion drives cascades of localised overturning, while the persistence of reverse temperature stratification indicated that mixing was not complete. While our array of temperature sensors had insufficient spatial resolution to provide full details of the flow, we hypothesize that: at salinities of 1 and 2 g L^?1  salt is released relatively uniformly and forms a layer of elevated salinity immediately below the ice, which supports double-diffusive salt-fingering; and at salinities of 4 and 8 g L^?1, salt plumes penetrate the reverse stratification. After the ice melted, a relatively fresh surface layer formed above a more saline layer, sufficient to suppress spring turnover. Our measurements compare favourably with field observations from lakes, and highlight the importance of salt exclusion on biogeochemical processes in lakes.     

多种聚氧乙烯牛脂胺混合物MON 0818的水生环境危害评估：脉冲暴露后沉积物、温度和恢复能力的影响

我们对一种商业表面活性剂混合物(多种聚氧乙烯牛脂胺)MON 0818进行了一系列毒性测试：1. 测定底栖无脊椎动物和鱼类在沉积物存在的情况下受到的毒性;2.测定大型蚤(Daphnia magna)和4种初级生产者经过24 h的脉冲暴露之后的恢复能力;3.鉴定水体温度上升对于2种冷水鱼类所受到MON 0818毒性的潜在影响。在沉积物存在的情况下,5种生物中有3种在最高10 mg/L的浓度下短期(24 h)死亡率为零。其余2种物种的中位有效浓度则显著高于仅对水体进行测试的结果。15 ℃下北极红点鲑(Salvelinus alpinus)的半数有效浓度统计上低于10 ℃下。绿藻(Rhabdocelis subcapitata)和普通小球藻(Chlorella vulgaris)在经过24 h 1 mg/L的暴露后的恢复期中显示出生长延迟的状况,表明该暴露可能存在潜在影响。尽管如此,2个物种的最大绝对生长速率并未改变,表明其均可恢复。1.5 mg/L下的蝾螈共生藻(Oophila sp.)和100 mg/L下的浮萍(Lemna minor)经过24 h的暴露并未显示显著反应。24 h 5 mg/L暴露之后的恢复期中,大型蚤显示出潜在的死亡率。然而存活个体的生殖终端指标并未受到影响。结果表明在沉积物的存在下MON 0818的快速损耗可以减轻对于被暴露生物的效果,在不小于环境中可能出现的MON 0818浓度情况下,24 h暴露以后的生物的完全恢复是可能的。
精选自Jose L. Rodriguez-Gil, Ryan Prosser, Gregory Hanta, David Poirier, Linda Lissemore, Mark Hanson, Keith R. Solomon. Aquatic hazard assessment of MON 0818, a commercial mixture of alkylamine ethoxylates commonly used in glyphosate-containing herbicide formulations. Part 2: Roles of sediment, temperature, and capacity for recovery following a pulsed exposure. Environmental Toxicology and Chemistry: Volume 36, Issue 2, pages 512–521, July 2017. DOI: 10.1002/etc.3558
详情请见http://onlinelibrary.wiley.com/wol1/doi/10.1002/etc.3558/full
     

Development and Evaluation of a Method to Determine Indicator Microorganisms in Air Emissions and Residue from Medical Waste Incinerators

To allow testing of microbial destruction in medical waste incinerators, methods were developed to determine indicator microorganisms (Bacillus Stearothermophilus spores) in incinerator air emissions and residue. The emission trapping train consisted of a water cooled glass probe and impingers containing a neutral phosphate buffer. In field tests, spores were injected directly into the probe, and results showed that approximately 60 percent of the spores were recovered. Spores were analyzed with adequate precision using a microbial membrane filter unit. Lab experiments indicated that spores were stable in neutral pH phosphate buffer for up to 20 days, and heat shocking samples (heating to 80°C for 20 minutes) reduced spore numbers in acidic or basic buffer. Laboratory tests also showed that 60 to 70 percent of spores initially added to ash were recovered up to 22 days after addition of the spores. In addition, lab tests showed that spores can be effectively recovered from residue test pipes spiked with indicator spores.     

Pilot-Scale Evaluation of an Incinerability Ranking System for Hazardous Organic Compounds

The U.S. Environmental Protection Agency’s (EPA) hazardous waste incinerator performance standards specify a minimum destruction and removal efficiency (DRE) for principal organic hazardous constituents (POHCs) designated in the incinerator waste feed. In the past, selection of appropriate POHCs for incinerator trial burns has been based largely on their heats of combustion. Attempting to improve upon this approach, the University of Dayton Research Institute (UDRI), under contract to the EPA Risk Reduction Engineering Laboratory, has developed a thermal stability-based ranking of compound "incinerability". The subject study was conducted to evaluate the laboratory-developed ranking system in a pilot-scale incinerator.

Mixtures of POHCs, spanning the ranking scale from most- to least-difficult to destroy (Class 1 to Class 7, respectively), were prepared and combined with a clay-based sorbent matrix. These mixtures were then fed into the rotary kiln incineration system at the U.S. EPA Incineration Research Facility (IRF). In a series of five tests, the following conditions were evaluated: baseline/ typical operation; thermal failure (quenching); mixing failure (overcharging); matrix failure (low feed H/CI ratio); and a worst-case combination of the three failure modes.

Under baseline conditions, mixing failure, and matrix failure, kiln-exit DREs for each compound were comparable from test to test. Operating conditions in these 3 modes appeared to be sufficient to effect considerable destruction (greater than 99.99 percent DRE) of all compounds. As a result, separation of the highest-ranked POHCs from the lowest-ranked POHCs according to observed DRE was not possible; a correlation between POHC ranking and DRE could not be confirmed.

A correlation between predicted and observed incinerability was more evident for the thermal failure and worst-case conditions. Kiln-exit DREs for the four POHCs predicted to be most stable (those in Classes 1 and 2) ranged from 99% to 99.99% under these conditions, and were generally lower than DREs for the POHCs predicted to be more easily destroyed. Statistically significant correlations above the 99 percent and 93 percent confidence intervals were identified for the thermal-failure and worst-case tests, respectively.     

Lessons from the 2006 Louisiana health and population survey

The 2005 hurricane season caused extensive damage and induced a mass migration of approximately 1.1 million people from southern Louisiana in the United States. Current and accurate estimates of population size and demographics and an assessment of the critical needs for public services were required to guide recovery efforts. Since forecasts using pre-hurricane data may produce inaccurate estimates of the post-hurricane population, a household survey in 18 hurricane-affected parishes was conducted to provide timely and credible information on the size of these populations, their demographics and their condition. This paper describes the methods used, the challenges encountered, and the key factors for successful implementation. This post-disaster survey was unique because it identified the needs of the people in the affected parishes and quantified the number of people with these needs. Consequently, this survey established new population and health indicator baselines that otherwise would have not been available to guide the relief and recovery efforts in southern Louisiana.     

Nanoparticle aggregation: challenges to understanding transport and reactivity in the environment

Unique forms of manufactured nanomaterials, nanoparticles, and their suspensions are rapidly being created by manipulating properties such as shape, size, structure, and chemical composition and through incorporation of surface coatings. Although these properties make nanomaterial development interesting for new applications, they also challenge the ability of colloid science to understand nanoparticle aggregation in the environment and the subsequent effects on nanomaterial transport and reactivity. This review briefly covers aggregation theory focusing on Derjaguin-Landau-Verwey-Overbeak (DLVO)-based models most commonly used to describe the thermodynamic interactions between two particles in a suspension. A discussion of the challenges to DLVO posed by the properties of nanomaterials follows, along with examples from the literature. Examples from the literature highlighting the importance ofaggregation effects on transport and reactivity and risk of nanoparticles in the environment are discussed.     

Sources of nitrate yields in the Mississippi River Basin

Riverine nitrate N in the Mississippi River leads to hypoxia in the Gulf of Mexico. Several recent modeling studies estimated major N inputs and suggested source areas that could be targeted for conservation programs. We conducted a similar analysis with more recent and extensive data that demonstrates the importance of hydrology in controlling the percentage of net N inputs (NNI) exported by rivers. The average fraction of annual riverine nitrate N export/NNI ranged from 0.05 for the lower Mississippi subbasin to 0.3 for the upper Mississippi River basin and as high as 1.4 (4.2 in a wet year) for the Embarras River watershed, a mostly tile-drained basin. Intensive corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] watersheds on Mollisols had low NNI values and when combined with riverine N losses suggest a net depletion of soil organic N. We used county-level data to develop a nonlinear model ofN inputs and landscape factors that were related to winter-spring riverine nitrate yields for 153 watersheds within the basin. We found that river runoff times fertilizer N input was the major predictive term, explaining 76% of the variation in the model. Fertilizer inputs were highly correlated with fraction of land area in row crops. Tile drainage explained 17% of the spatial variation in winter-spring nitrate yield, whereas human consumption of N (i.e., sewage effluent) accounted for 7%. Net N inputs were not a good predictor of riverine nitrate N yields, nor were other N balances. We used this model to predict the expected nitrate N yield from each county in the Mississippi River basin; the greatest nitrate N yields corresponded to the highly productive, tile-drained cornbelt from southwest Minnesota across Iowa, Illinois, Indiana, and Ohio. This analysis can be used to guide decisions about where efforts to reduce nitrate N losses can be most effectively targeted to improve local water quality and reduce export to the Gulf of Mexico.     

Size Distribution and Sources of Aerosol in Launceston,Australia, during Winter 1997

ABSTRACT

As part of a pilot study into the chemical and physical properties of Australian fine particles, a suite of aerosol samples was collected at Ti Tree Bend in Launceston, Tasmania, during June and July 1997. This period represents midwinter in the Southern Hemisphere, a period when aerosol sources in Launceston are dominated by smoke from domestic wood burning. This paper describes the results from this measurement campaign, with the aim of assessing the effect of wood smoke on the chemical and physical characteristics of ambient aerosol. A micro orifice uniform deposit impactor (MOUDI) was used to measure the size distributions of the aerosol from 0.05 to 20 n m aerodynamic diameter. Continuous measurements of fine particle mass were made using a PM_2.5 tapered element oscillating microbalance (TEOM) and light scattering coefficients at 530 nm were measured with nephelometers.

Mass size distributions tended to be bimodal, with the diameter of the dominant mode tending to smaller sizes with increases in total mass. Non-sea salt potassium and polycyclic aromatic hydrocarbons (PAHs) were used as chemical tracers for wood smoke. Wood smoke was found to increase absolute particle mass (enough to regularly exceed air quality standards), and to concentrate mass in a single mode below 1 μm aerodynamic diameter. The acid-base equilibrium of the aerosol was altered by the wood smoke source, with free acidity hydrogen ion, non-sea salt sulfate, and ammonium concentrations being higher and the concentration of all species, including nitrate (to differing extents), focused in the fine particle size ranges. The wood smoke source also heavily influenced the aerosol scattering efficiency, adding to a strong diurnal cycle in both mass concentration and light scattering.     

Furazolidone residues in chicken and swine tissues after feeding trials

Abstract

Broiler chickens and swine fed furazolidone in their diet were sacrificed, and samples of liver, kidney, skin/fat and muscle were harvested and analyzed for furazolidone residue. Chickens fed 200 g of furazolidone/ton of feed were withdrawn from treatment 21, 14, 7, 5, 3, or 0 days before slaughter. Birds withdrawn from medication more than 5 days prior to slaughter had no residues in any of the tissues sampled. One of the 12 birds in each of the 5 day and 3 day withdrawal groups had detectable residues in the skin/fat. Seven of the 12 birds in the 0 day withdrawal group had residues of <2 ppb in skin/fat samples. Chickens fed 400 g furazolidone/ton of feed were withdrawn from treatment 0 days before slaughter. Residues of 0.7 to 3.5 ppb were found in the skin of these birds; residues were not found in other tissues. Swine were fed 300 g furazolidone/ton of feed for 2 weeks or 150 g/ton for 5 weeks. They were withdrawn from treatment 10, 7, 5, 3, or 0 days before slaughter. Tissue samples taken from these swine did not contain detectable furazolidone residues.     

Concentrations of polychlorinated biphenyls in water from US Lake Ontario tributaries between 2004 and 2008

Research on the environmental fate and transport of PCBs in Lake Ontario basin depends, among other aspects, on the availability of representative data sets for upstream sources, but data are lacking for most US Lake Ontario tributaries. In this study, water samples were collected between September 2004 and October 2008 from five tributaries and were analyzed for 209 polychlorinated biphenyls (PCB) with high-resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) following EPA Method 1668A. Total PCB concentrations ranged between 0.31 and 42.75 ng L⁻¹. Congeners between Di and Hexa PCBs accounted between 70 and 99% of the total PCB. The tributary with highest PCB concentrations presented similar pattern and percentage levels to Aroclor 1242. Total average loads for the sampling events ranged between 1.85 g d⁻¹ and 59.08 g d⁻¹. PCB concentrations were evaluated against other variables and other studies (including different matrices) to better understand their transport. The methodology used is reliable to assess PCB contamination in surface water.