Testing soils and cornstalks to evaluate nitrogen management on the watershed scale

High nitrate (NO3-N) concentrations in Iowa rivers have been linked to areas of intensive row crop production, but they have not been experimentally linked to specific management practices used during row crop production. This study demonstrates how the late-spring test for soil NO3-N and the end-of-season test for cornstalk NO3-N can be used to measure N sufficiency levels across many fields and how the results can be used to evaluate management practices within a watershed. More than 3200 soil and cornstalk samples were collected over a 12-yr period from fields planted to corn (Zea mays L.) and already fertilized by farmers using their normal practices. Results showed that early-season rainfall and associated N losses were major factors affecting N concentrations in soils and cornstalks. Evidence for NO3-N movement from fields to rivers was provided by an inverse relationship between annual means for NO3-N concentrations in soils and rivers. Because these losses can be avoided by delaying N applications, the practice of applying N several weeks or months before plants grow was linked to inefficient use of fertilizer and manure N by crops. Results of the study demonstrate how aggregate analyses of soil and cornstalk samples collected across many farms and years make it possible to identify the major factors affecting N management outcomes and, therefore, N management practices that are likely to produce the best outcomes within a watershed or region. This approach seems to have unique potential to interrelate the management practices of farmers, the efficiency of N fertilization, and NO3-N concentrations in rivers.     

Songbird response to increased willow (Salix spp.) growth in Yellowstone's northern range

After nearly a century of height suppression, willows (Salix spp.) in the northern range of Yellowstone National Park, U.S.A., are increasing in height growth as a possible consequence of wolf (Canis lupus) restoration, climate change, or other factors. Regardless of the drivers, the recent release of this rare but important habitat type could have significant implications for associated songbirds that are exhibiting declines in the region. Our objective was to evaluate bird response to releasing willows by comparing willow structure and bird community composition across three willow growth conditions: height suppressed, recently released, and previously tall (i.e., tall prior to the height increase of released willows). Released and previously tall willows exhibited high and similar vertical structure, but released willows were significantly lower in horizontal structure. Suppressed willows were significantly shorter and lower in horizontal cover than released or previously tall willows. Bird richness increased along a gradient from lowest in suppressed to highest in previously tall willows, but abundance and diversity were similar between released and previously tall willows, despite lower horizontal cover in the released condition. Common Yellowthroat (Geothlypis trichas) and Lincoln's Sparrow (Melospiza lincolnii) were found in all three growth conditions; however, Yellow Warbler (Dendroica petechia), Warbling Vireo (Vireo gilvus), Willow Flycatcher (Empidonax traillii), and Song Sparrow (Melospiza melodii) were present in released and previously tall willows only. Wilson's Warbler (Wilsonia pusilla) was found in previously tall willows only, appearing to specialize on tall, dense willows. The results of our a priori habitat models indicated that foliage height diversity was the primary driver of bird richness, abundance, and diversity. These results indicate that vertical structure was a more important driver of bird community variables than horizontal structure and that riparian and willow-dependent bird species have responded positively to increased willow growth in the region.     

Metals and organotins in multiple bivalve species in a one-off global survey

The Galathea 3 expedition circumnavigated the globe in 2006-2007 and collected marine samples from six continents. Bivalves were collected from harbours, other impacted locations and reference sites, and samples from 57 sites were analyzed for metals and 47 for organotins, to assess current contamination levels on a global scale. Metal concentrations in nine bivalve species were normalised to the Mytilidae family using conversion factors based on cosampled species and literature bioconcentration factors. The lowest metal and tributyltin concentrations were below background assessment concentrations (BACs) agreed in the Oslo-Paris convention (OSPAR) for the North Sea, and at most harbours the concentrations were orders of magnitude above BACs. The lowest concentrations of Cd and Pb measured here suggest that the BACs should be lower in a worldwide context. The sources of metals were classified according to human impact using principal component analysis. High relative concentrations of Hg, Pb and P were source indicators for industrial activity and land use; Zn, organotins, Cd and Cu for shipping activities, and V for oil spills. Generally the concentration levels at reference sites were low, but not always lower than expected impacted areas. The most contaminated areas were harbours, where especially Copenhagen, St Croix and Sydney, can be considered hotspots of tributyltin as well as a number of metals.     

Evaluation of the readsorption of plutonium and americium in dynamic fractionations of environmental solid samples

A dynamic extraction system exploiting sequential injection (SI) for sequential extractions incorporating a specially designed extraction column is developed to fractionate radionuclides in environmental solid samples such as soils and sediments. The extraction column can contain up to 5 g of a soil sample, and under optimal operational conditions it does not give rise to creation of back pressure. Attention has been placed on studies of the readsorption problems during sequential extraction using a modified Standards, Measurements and Testing (SM&T) scheme with four-step sequential extractions. The degree of readsorption in dynamic and conventional batch extraction systems is compared and evaluated by using a double-spiking technique. A high degree of readsorption of plutonium and americium (>75%) was observed in both systems, and they also exhibited similar distribution patterns of the two radionuclides. However, the dynamic system is fully automated, eliminates manual separations, significantly reduces the operational time required, and offers detailed kinetic information.     

Degradation of zearalenone and ochratoxin A in three Danish agricultural soils

Degradation of two mycotoxins: zearalenone (ZON) produced by species of Fusarium and ochratoxin A (OTA) produced by species of Penicillium were followed in pot experiments using agricultural topsoils from Danish experimental farms: a sandy soil, a sandy clay soil and a gyttja soil with a high content of silt. Experiments with unplanted soil and pots planted with barley were included. Soil samples were withdrawn during a period of 225 days and analysed for the content of OTA and ZON. The degradation of both toxins consisted of an initial fast degradation followed by a slower transformation step and was described well by a sum of two first-order kinetic equations. The decay first-order rate constants for the first step (k1) were in the range 0.73-2.91 d(-1) for OTA and 0.0612-0.108 d(-1) for ZON, respectively. Half-lives (t0.5) for ZON using data from the first phase were between 6.4 and 11 days, whereas the half-lives for OTA were about 0.2-1 day. The slowest degradation was measured in soil rich in clay. After 225 days, neither OTA nor ZON was detected in any of the soil types. Generally, the degradation of ZON and OTA was faster in planted soil than in unplanted soil, probably due to higher microbial activity. Due to the fast degradation of ZON and OTA in surface soil leaching as soluble substances appears to be limited.     

Validation of FLACS against experimental data sets from the model evaluation database for LNG vapor dispersion

The siting of facilities handling liquefied natural gas (LNG), whether for liquefaction, storage or regasification purposes, requires the hazards from potential releases to be evaluated. One of the consequences of an LNG release is the creation of a flammable vapor cloud, that may be pushed beyond the facility boundaries by the wind and thus present a hazard to the public. Therefore, numerical models are required to determine the footprint that may be covered by a flammable vapor cloud as a result of an LNG release. Several new models have been used in recent years for this type of simulations. This prompted the development of the “Model evaluation protocol for LNG vapor dispersion models” (MEP): a procedure aimed at evaluating quantitatively the ability of a model to accurately predict the dispersion of an LNG vapor cloud.This paper summarizes the MEP requirements and presents the results obtained from the application of the MEP to a computational fluid dynamics (CFD) model – FLACS. The entire set of 33 experiments included in the model validation database were simulated using FLACS. The simulation results are reported and compared with the experimental data. A set of statistical performance measures are calculated based on the FLACS simulation results and compared with the acceptability criteria established in the MEP. The results of the evaluation demonstrate that FLACS can be considered a suitable model to accurately simulate the dispersion of vapor from an LNG release.     

Methane production during storage of anaerobically digested municipal organic waste

Anaerobic digestion of source-separated municipal organic waste is considered feasible in Denmark. The limited hydraulic retention in the biogas reactor (typically 15 d) does not allow full degradation of the organic waste. Storage of anaerobically digested municipal organic waste can therefore be a source of methane (CH4) emission that may contribute significantly to the potential global warming impact from the waste treatment system. This study provides a model for quantifying the CH4 production from stored co-digested municipal organic waste and estimates the production under typical Danish climatic conditions, thus quantifying the potential global warming impact from storage of the digested municipal organic waste before its use on agricultural land. Laboratory batch tests on CH4 production as well as temperature measurements in eight full-scale storage tanks provided data for developing a model estimating the CH4 production in storage tanks containing digested municipal organic waste. The temperatures measured in separate storage tanks on farms receiving digested slurry were linearly correlated with air temperature. In storage tanks receiving slurry directly from biogas reactors, significantly higher temperatures were measured due to the high temperatures of the effluent from the reactor. Storage tanks on Danish farms are typically emptied in April and have a constant inflow of digested material. During the warmest months the content of digested material is therefore low, which limits the yearly CH4 production from storage.     

Chemical and microbial characteristics of municipal drinking water supply systems in the Canadian Arctic

Drinking water in the vast Arctic Canadian territory of Nunavut is sourced from surface water lakes or rivers and transferred to man-made or natural reservoirs. The raw water is at a minimum treated by chlorination and distributed to customers either by trucks delivering to a water storage tank inside buildings or through a piped distribution system. The objective of this study was to characterize the chemical and microbial drinking water quality from source to tap in three hamlets (Coral Harbour, Pond Inlet and Pangnirtung—each has a population of <2000) on trucked service, and in Iqaluit (population ~6700), which uses a combination of trucked and piped water conveyance. Generally, the source and drinking water was of satisfactory microbial quality, containing Escherichia coli levels of <1 MPN/100 mL with a few exceptions, and selected pathogenic bacteria and parasites were below detection limits using quantitative polymerase chain reaction (qPCR) methods. Tap water in households receiving trucked water contained less than the recommended 0.2 mg/L of free chlorine, while piped drinking water in Iqaluit complied with Health Canada guidelines for residual chlorine (i.e. >0.2 mg/L free chlorine). Some buildings in the four communities contained manganese (Mn), copper (Cu), iron (Fe) and/or lead (Pb) concentrations above Health Canada guideline values for the aesthetic (Mn, Cu and Fe) and health (Pb) objectives. Corrosion of components of the drinking water distribution system (household storage tanks, premise plumbing) could be contributing to Pb, Cu and Fe levels, as the source water in three of the four communities had low alkalinity. The results point to the need for robust disinfection, which may include secondary disinfection or point-of-use disinfection, to prevent microbial risks in drinking water tanks in buildings and ultimately at the tap.     

Spatiotemporal variability in surface energy balance across tundra,snow and ice in Greenland

The surface energy balance (SEB) is essential for understanding the coupled cryosphere–atmosphere system in the Arctic. In this study, we investigate the spatiotemporal variability in SEB across tundra, snow and ice. During the snow-free period, the main energy sink for ice sites is surface melt. For tundra, energy is used for sensible and latent heat flux and soil heat flux leading to permafrost thaw. Longer snow-free period increases melting of the Greenland Ice Sheet and glaciers and may promote tundra permafrost thaw. During winter, clouds have a warming effect across surface types whereas during summer clouds have a cooling effect over tundra and a warming effect over ice, reflecting the spatial variation in albedo. The complex interactions between factors affecting SEB across surface types remain a challenge for understanding current and future conditions. Extended monitoring activities coupled with modelling efforts are essential for assessing the impact of warming in the Arctic.