Agricultural opportunities to mitigate greenhouse gas emissions

Agriculture is a source for three primary greenhouse gases (GHGs): CO(2), CH(4), and N(2)O. It can also be a sink for CO(2) through C sequestration into biomass products and soil organic matter. We summarized the literature on GHG emissions and C sequestration, providing a perspective on how agriculture can reduce its GHG burden and how it can help to mitigate GHG emissions through conservation measures. Impacts of agricultural practices and systems on GHG emission are reviewed and potential trade-offs among potential mitigation options are discussed. Conservation practices that help prevent soil erosion, may also sequester soil C and enhance CH(4) consumption. Managing N to match crop needs can reduce N(2)O emission and avoid adverse impacts on water quality. Manipulating animal diet and manure management can reduce CH(4) and N(2)O emission from animal agriculture. All segments of agriculture have management options that can reduce agriculture's environmental footprint.     

Challenges in quantifying biosphere-atmosphere exchange of nitrogen species

Recent research in nitrogen exchange with the atmosphere has separated research communities according to N form. The integrated perspective needed to quantify the net effect of N on greenhouse-gas balance is being addressed by the NitroEurope Integrated Project (NEU). Recent advances have depended on improved methodologies, while ongoing challenges include gas-aerosol interactions, organic nitrogen and N(2) fluxes. The NEU strategy applies a 3-tier Flux Network together with a Manipulation Network of global-change experiments, linked by common protocols to facilitate model application. Substantial progress has been made in modelling N fluxes, especially for N(2)O, NO and bi-directional NH(3) exchange. Landscape analysis represents an emerging challenge to address the spatial interactions between farms, fields, ecosystems, catchments and air dispersion/deposition. European up-scaling of N fluxes is highly uncertain and a key priority is for better data on agricultural practices. Finally, attention is needed to develop N flux verification procedures to assess compliance with international protocols.     

Estimated Variability of National Atmospheric Deposition Program/Mercury Deposition Network Measurements Using Collocated Samplers

The National Atmospheric Deposition Program/Mercury Deposition Network (MDN) provides long-term, quality-assured records of mercury in wet deposition in the USA and Canada. Interpretation of spatial and temporal trends in the MDN data requires quantification of the variability of the MDN measurements. Variability is quantified for MDN data from collocated samplers at MDN sites in two states, one in Illinois and one in Washington. Median absolute differences in the collocated sampler data for total mercury concentration are approximately 11% of the median mercury concentration for all valid 1999–2004 MDN data. Median absolute differences are between 3.0% and 14% of the median MDN value for collector catch (sample volume) and between 6.0% and 15% of the median MDN value for mercury wet deposition. The overall measurement errors are sufficiently low to resolve between NADP/MDN measurements by ±2 ng·l⁻¹ and ±2 μg·m⁻²·year⁻¹, which are the contour intervals used to display the data on NADP isopleths maps for concentration and deposition, respectively.     

Northern Idaho House Dust and Soil Lead Levels Compared to the Bunker Hill Superfund Site

House dust has been identified as a major exposure medium for lead (Pb) in children. High levels of Pb in soil and house dust have been recorded at the Bunker Hill Superfund Site (BHSS) in northern Idaho, an historic mining and smelting district. Soil and dust remediation at the site was required; however, regional background soil and dust Pb levels had not been well characterized. The objective of this survey was to determine background house dust Pb levels and to compare those levels with concentrations, and dust and Pb loading rates measured at the BHSS. Soil and house dust samples were collected in five towns demographically similar to the BHSS but unaffected by the mining industry. The background concentrations and loading rates were significantly lower than those observed at the site. House age was a significant factor affecting background soil and house dust Pb concentrations and loading rates.     

Bioaccumulation of anthropogenic contaminants by detritivorous fish in the Río de la Plata estuary: 1-aliphatic hydrocarbons

The temporal variability and bioaccumulation dynamics of C_12–25 n-alkanes, isoprenoids and unresolved aliphatic hydrocarbons (UCM) were studied in a detritivorous fish (Sábalo: Prochilodus lineatus) collected from 1999 to 2005 in the sewage impacted Buenos Aires coastal area. Fish muscles contain huge amounts of n-C_12–25 (165 ± 93, 70 ± 48 or 280 ± 134 μg g⁻¹, dry, fresh and lipid weight, respectively) and UCM (931 ± 560, 399 ± 288 and 1567 ± 802 μg g⁻¹) reflecting the chronic bioaccumulation of fossil fuels from sewage particulates. On a temporal basis, lipid normalized aliphatic concentrations peaked by the end of 2001–2002 during the rainiest period over the last four decades (1750 vs. 1083 ± 4.6 mm in 1999, 2004 and 2005), reflecting an enhanced exposition due to massive anthropogenic fluxes from Metropolitan Buenos Aires in wet years. The hydrocarbon composition in fish muscles is enriched in n-C_15–17 and isoprenoids relative to a fresh crude oil and settling particulates, with fresher signatures during the 2001–2002 maxima. Fish/settling material bioaccumulation factors (BAFs: 0.4–6.4 dry weight or 0.07–0.94 lipid-organic carbon) plotted against K_ow showed a parabolic pattern maximizing at n-C_14–18 and isoprenoids. The optimal bioaccumulation window corresponds to highly hydrophobic (log K_ow: 7.2–9.9), intermediate-size C_14–18 n-alkanes and C_15–20 isoprenoids (MW: 198–282; length: 17.9 to 25.4 Å) with melting points ranging from −19.8 to 28 °C. The uptake efficiency is inversely correlated to melting points and increased from 75% for n-C₂₅ to above 90% for n-C_14–15 and isoprenoids.     

HPLC-MSn and GC-MS methods to study sunlight and UV-lamp degradations of 1-amino-5-naphthalene sulfonate

HPLC-DAD, HPLC-MS/MS, GC-MS and spectrophotometric methods are employed to investigate the degradation process of sodium 1-amino-5-naphthalene sulfonate (1A5NS) aqueous solutions, when exposed to sunlight and UV-lamp (254 nm) irradiations. Experimental results show that both sunlight and 254 nm UV-lamp irradiations destroy the chemical and give rise to major degradation products, characterised by the same m/z ratios. Degradation times are lower for sunlight irradiation, for which a t(1/2) value of 137.4 min has been evaluated, in comparison with the value of t(1/2) of 26.8 min, observed for UV-lamp irradiation. The degradation pathway and the structures of the degradation products are proposed.     

Advanced oxidation processes for the treatment of olive-oil mills wastewater

In this work, the treatment of an actual industrial waste with three advanced oxidation processes (AOP) has been studied: conductive-diamond electrooxidation (CDEO), ozonation and Fenton oxidation. The wastewater comes from olive-oil mills (OMW) and contains a COD of nearly 3000 mg dm(-3). CDEO allowed achieving the complete mineralization of the waste with high current efficiencies. Likewise, both ozonation and Fenton oxidation were able to treat the wastes, but they obtained very different results in terms of efficiency and mineralization. The accumulation of oxidation-refractory compounds as final products excludes the use of ozonation and Fenton oxidation as a sole treatment technology. This confirms that besides the hydroxyl-radical mediated oxidation, CDEO combines other important oxidation processes such as the direct electro-oxidation on the diamond surface and the oxidation mediated by other electrochemically formed compounds generated on this electrode.     

XAFS studies of cobalt(II) binding by solid peat and soil-derived humic acids and plant-derived humic acid-like substances

This work has examined cobalt(II) binding by a variety of solid humic acids (HAs) isolated from peat, plant and soil sources at temperatures down to 60K. The results confirm that X-ray absorption near-edge spectroscopy (XANES) measurements cannot distinguish between aquo and carboxylato ligands in the inner coordination sphere of Co(II). However, between 1 and 2 inner-sphere carboxylato ligands can be detected in all the peat, plant and soil-derived HA samples by extended X-ray absorption fine structure (EXAFS) measurements, indicating inner-sphere coordination of HA-bound Co(II). The precision of C(carboxylate) detection is limited by the extent and quality of the data and the contribution from inner-sphere O to the Fourier transformed peaks used to detect carbon. Putative chelate ring formation is consistent with a relatively negative entropy change in step A, the stronger Co(II) binding step by HA functional groups, and could relate to 'non-exchangeable' metal binding by HSs.     

Plant senescence: a mechanism for nutrient release in temperate agricultural wetlands

The beneficial uptake of nutrients by wetland plants is countered to some extent by nutrient release back into the aquatic environment due to vegetative die-back. This current study examined whether Leersia oryzoides, a common wetland plant, exhibits luxury uptake of nutrients from simulated farm runoff. The study also tested whether with subsequent decomposition, these nutrients are released back into the water column. When exposed to elevated (>2mg/L N and P) runoff, L. oryzoides assimilated significantly higher concentrations of nitrogen (p<0.001) and phosphorus (p<0.001) in above-ground biomass as compared to non-enriched treatments (<0.05 mg/L N and P). Subsequently, senescence of enriched above-ground biomass yielded significantly higher concentrations of phosphorus (2.19+/-0.84 mg P/L). Using L. oryzoides as our model, this study demonstrates nitrogen and phosphorus sequestration during the growing season and release of phosphorus in the winter.     

Essential and non-essential element concentrations in two sleeper shark species collected in arctic waters

A number of elements/metals have increased in arctic biota and are of concern due to their potential toxicity. Most studies on elements in the Arctic have focused on marine mammals and seabirds, but concentrations in the Greenland shark (Somniosus microcephalus) and Pacific sleeper shark (Somniosus pacificus), the only two shark species known to regularly inhabit arctic waters, have never been reported. To address this data gap, concentrations and patterns of 25 elements were analyzed in liver of Greenland sharks collected about Cumberland Sound (n=24) and Pacific sleeper sharks collected about Prince William Sound (n=14). Several non-essential elements differed between species/locations, which could suggest geographical exposure differences or ecological (e.g., diet) differences between the species. Certain essential elements also differed between the two sleeper sharks, which may indicate different physiological requirements between these closely related shark species, although information on such relationships are lacking for sharks and fish.