Degree of phosphorus saturation of an Oxisol amended with biosolids in a long-term field experiment

When applied to agricultural soils, phosphate fertilizers and the mineral or organic compounds present in solid and/or liquid waste may raise phosphorus (P) content and increase soil P saturation. The degree of phosphorus saturation (DPS) is a good indicator of potential P loss from agricultural soils. The purpose of this study was to calculate the DPS of samples from an Oxisol amended for 5 years with biosolids and mineral fertilizer. DPS was calculated based on P, iron, and aluminum extracted by ammonium oxalate and oxalic acid (DPS_ox) or by Mehlich-1 solution (DPS_M1). Treatments included NPK mineral fertilization (175 kg ha^?1 of P), B1?=?19.02 t ha^?1 of biosolids (350 kg ha^?1 of P), B2?=?38.17 t ha^?1 of biosolids (703 kg ha^?1 of P), B3?=?76.26 t ha^–1 of biosolids (1,405 kg ha^?1 of P), and a control (no P added). Water-extractable P (WEP) was also measured. Critical levels of DPS_ox and DPS_M1 (21 and 24 %, respectively) were only achieved in the topsoil (0–0.1 m) at the highest biosolid dose. Concentration of WEP was positively correlated to DPS_ox and DPS_M1. The DPS_M1 method may be an alternative to DPS_ox for assessing the environmental risk of P loss from soil into surface runoff.     

China's grazed temperate grasslands are a net source of atmospheric methane

A budget for the methane (CH₄) cycle in the Xilin River basin of Inner Mongolia is presented. The annual CH₄ budget in this region depends primarily on the sum of atmospheric CH₄ uptake by upland soils, emission from small wetlands, and emission from grazing ruminants (sheep, goats, and cattle). Flux rates for these processes were averaged over multiple years with differing summer rainfall. Although uplands constitute the vast majority of land area, they consume much less CH₄ per unit area than is emitted by wetlands and ruminants. Atmospheric CH₄ uptake by upland soils was ?3.3 and ?4.8 kg CH₄ ha^?1 y^?1 in grazed and ungrazed areas, respectively. Average CH₄ emission was 791.0 kg CH₄ ha^?1 y^?1 from wetlands and 8.6 kg CH₄ ha^?1 y^?1 from ruminants. The basin area-weighted average of all three processes was 6.8 kg CH₄ ha^?1 y^?1, indicating that ruminant production has converted this basin to a net source of atmospheric CH₄. The total CH₄ emission from the Xilin River basin was 7.29 Gg CH₄ y^?1. The current grazing intensity is about eightfold higher than that which would result in a net zero CH₄ flux. Since grazing intensity has increased throughout western China, it is likely that ruminant production has converted China's grazed temperate grasslands to a net source of atmospheric CH₄ overall.     

Organic compound emissions from a landfarm used for oil and gas solid waste disposal

Solid or sludgy hydrocarbon waste is a by-product of oil and gas exploration and production. One commonly used method of disposing of this waste is landfarming. Landfarming involves spreading hydrocarbon waste on soils, tilling it into the soil, and allowing it to biodegrade. We used a dynamic flux chamber to measure fluxes of methane, a suite of 54 nonmethane hydrocarbons, and light alcohols from an active and a remediated landfarm in eastern Utah. Fluxes from the remediated landfarm were not different from a polytetrafluoroethylene (PTFE) sheet or from undisturbed soils in the region. Fluxes of methane, total nonmethane hydrocarbons, and alcohols from the landfarm in active use were 1.41 (0.37, 4.19) (mean and 95% confidence limits), 197.90 (114.72, 370.46), and 4.17 (0.03, 15.89) mg m^?2 hr^?1, respectively. Hydrocarbon fluxes were dominated by alkanes, especially those with six or more carbons. A 2-ha landfarm with fluxes of the magnitude we observed in this study would emit 95.3 (54.3, 179.7) kg day^?1 of total hydrocarbons, including 11.2 (4.3, 33.9) kg day^?1 of BTEX (benzene, toluene, ethylbenzene, and xylenes).

Implications: Solid and sludgy hydrocarbon waste from the oil and gas industry is often disposed of by landfarming, in which wastes are tilled into soil and allowed to decompose. We show that a land farm in Utah emitted a variety of organic compounds into the atmosphere, including hazardous air pollutants and compounds that form ozone. We calculate that a 2-ha landfarm facility would emit 95.0 ± 66.0 kg day^?1 of total hydrocarbons, including 11.1 ± 1.5 kg day^?1 of BTEX (benzene, toluene, ethylbenzene, and xylenes).     

Effect of land-use change on CH4 and N2O emissions from freshwater marsh in Northeast China

The wetlands play an important role in global carbon and nitrogen storage, and they are also natural sources of greenhouse gases such as methane (CH₄) and nitrous oxide (N₂O). Land-use change is an important factor affecting the exchange of greenhouse gases between wetlands and the atmosphere. However, few studies have investigated the effect of land-use change on CH₄ and N₂O emissions from freshwater marsh in China. Therefore, a field study was carried out over a year to investigate the seasonal changes of the emissions of CH₄ and N₂O at three sites (Deyeuxia angustifolia marsh, dryland and rice field) in the Sanjiang Plain of Northeast China. Marsh was the source of CH₄ showing a distinct temporal variation. Maximum fluxes occurred in June and the highest value was 20.69 ± 2.57 mg CH₄ m^?2 h^?1. The seasonal change of N₂O fluxes from marsh was not obvious, consisted of a series of emission pulses. The marsh acted as a N₂O sink during winter, while became a N₂O source in the growing season. The results showed that gas exchange between soil/snow and the atmosphere in the winter season contributed greatly to the annual budgets. The winter season CH₄ flux was about 3.24% of the annual flux and the winter uptake of N₂O accounted for 13.70% of the growing-season emission. Conversion marsh to dryland resulted in a shift from a strong CH₄ source to a weak sink (from 199.12 ± 39.04 to ?1.37 ± 0.68 kg CH₄ ha^?1 yr^?1), while increased N₂O emissions somewhat (from 4.07 ± 1.72 to 4.90 ± 1.52 kg N₂O ha^?1 yr^?1). Conversion marsh to rice field significantly decreased CH₄ emission from 199.12 ± 39.04 to 94.82 ± 9.86 kg CH₄ ha^?1 yr^?1 and N₂O emission from 4.07 ± 1.72 to 2.09 ± 0.79 kg N₂O ha^?1 yr^?1.     

Saline irrigation and Zn amendment effect on Cd phytoavailability to Swiss chard (Beta vulgaris L.) grown on a long-term amended agricultural soil: a human risk assessment

Crops, particularly in the Northeast region of Mexico, have to cope with increasing soil salinization due to irrigation. Chloride (Cl^?) concentration has been strongly related to enhance cadmium (Cd) uptake by plants due to increased solubility in the soil solution. The effect of irrigation with slightly saline water from a local well was evaluated in this work on the accumulation and translocation of Cd in Swiss chard (Beta vulgaris L.) grown in soil historically amended with stabilized sewage sludge under a regime of phosphorus and zinc fertilization. A factorial pot experiment was conducted with two phosphate fertilizer levels (PF, 0 and 80 kg ha^?1 dry soil, respectively), two Zn levels (0 and 7 kg ha^?1 dry soil), and two sources of water for irrigation deionized water (DW) and slightly saline well water (WW) from an agricultural site. Additionally, a human risk assessment for Cd ingestion from plants was assessed. Results showed that Cl^? salinity in the WW effectively mobilized soil Cd and increased its phytoavailability. A higher level of Cd was found in roots (46.41 mg kg^?1) compared to shoots (10.75 mg kg^?1). Although the total content of Cd in the edible parts of the Swiss chard irrigated with WW exceeded permissible recommended consumption limit, bioavailable cadmium in the aboveground parts of the plant in relation to the total cadmium content was in the range from 8 to 32 %. Therefore, human health risks might be overestimated when the total concentration is taken into account.     

Approximation and spatial regionalization of rainfall erosivity based on sparse data in a mountainous catchment of the Yangtze River in Central China

In densely populated countries like China, clean water is one of the most challenging issues of prospective politics and environmental planning. Water pollution and eutrophication by excessive input of nitrogen and phosphorous from nonpoint sources is mostly linked to soil erosion from agricultural land. In order to prevent such water pollution by diffuse matter fluxes, knowledge about the extent of soil loss and the spatial distribution of hot spots of soil erosion is essential. In remote areas such as the mountainous regions of the upper and middle reaches of the Yangtze River, rainfall data are scarce. Since rainfall erosivity is one of the key factors in soil erosion modeling, e.g., expressed as R factor in the Revised Universal Soil Loss Equation model, a methodology is needed to spatially determine rainfall erosivity. Our study aims at the approximation and spatial regionalization of rainfall erosivity from sparse data in the large (3,200 km²) and strongly mountainous catchment of the Xiangxi River, a first order tributary to the Yangtze River close to the Three Gorges Dam. As data on rainfall were only obtainable in daily records for one climate station in the central part of the catchment and five stations in its surrounding area, we approximated rainfall erosivity as R factors using regression analysis combined with elevation bands derived from a digital elevation model. The mean annual R factor (R _a) amounts for approximately 5,222 MJ?mm?ha^?1?h^?1?a^?1. With increasing altitudes, R _a rises up to maximum 7,547 MJ?mm ha^?1?h^?1 a^?1 at an altitude of 3,078 m a.s.l. At the outlet of the Xiangxi catchment erosivity is at minimum with approximate R _a?=?1,986 MJ?mm?ha^?1?h^?1?a^?1. The comparison of our results with R factors from high-resolution measurements at comparable study sites close to the Xiangxi catchment shows good consistance and allows us to calculate grid-based R _a as input for a spatially high-resolution and area-specific assessment of soil erosion risk.     

Nitrogen and plant population change radiation capture and utilization capacity of sunflower in semi-arid environment

The combination of nitrogen and plant population expresses the spatial distribution of crop plants. The spatial distribution influences canopy structure and development, radiation capture, accumulated intercepted radiation (Sa), radiation use efficiency (RUE), and subsequently dry matter production. We hypothesized that the sunflower crop at higher plant populations and nitrogen (N) rates would achieve early canopy cover, capture more radiant energy, utilize radiation energy more efficiently, and ultimately increase economic yield. To investigate the above hypothesis, we examined the influences of leaf area index (LAI) at different plant populations (83,333, 66,666, and 55,555 plants ha^?1) and N rates (90, 120, and 150 kg ha^?1) on radiation interception (Fi), photosynthetically active radiation (PAR) accumulation (Sa), total dry matter (TDM), achene yield (AY), and RUE of sunflower. The experimental work was conducted during 2012 and 2013 on sandy loam soil in Punjab, Pakistan. The sunflower crop captured more than 96% of incident radiant energy (mean of all treatments), 98% with a higher plant population (83,333 plants ha^?1), and 97% with higher N application (150 kg ha^?1) at the fifth harvest (60 days after sowing) during both study years. The plant population of 83,333 plants ha^?1 with 150 kg N ha^?1 ominously promoted crop, RUE, and finally productivity of sunflower (AY and TDM). Sunflower canopy (LAI) showed a very close and strong association with Fi (R ² = 0.99 in both years), PAR (R ² = 0.74 and 0.79 in 2012 and 2013, respectively), TDM (R ² = 0.97 in 2012 and 0.91 in 2013), AY (R ² = 0.95 in both years), RUE for TDM (RUE_TDM) (R ² = 0.63 and 0.71 in 2012 and 2013, respectively), and RUE for AY (RUE_AY) (R ² = 0.88 and 0.87 in 2012 and 2013, respectively). Similarly, AY (R ² = 0.73 in 2012 and 0.79 in 2013) and TDM (R ² = 0.75 in 2012 and 0.84 in 2013) indicated significant dependence on PAR accumulation of sunflower. High temperature during the flowering stage in 2013 shortened the crop maturity duration, which reduced the LAI, leaf area duration (LAD), crop growth rate (CGR), TDM, AY, Fi, Sa, and RUE of sunflower. Our results clearly revealed that RUE was enhanced as plant population and N application rates were increased and biomass assimilation in semi-arid environments varied with radiation capture capacity of sunflower.     

Monitoring the Multi-Year Carbon Balance of a Subarctic Palsa Mire with Micrometeorological Techniques

This article reports a dataset on 8 years of monitoring carbon fluxes in a subarctic palsa mire based on micrometeorological eddy covariance measurements. The mire is a complex with wet minerotrophic areas and elevated dry palsa as well as intermediate sub-ecosystems. The measurements document primarily the emission originating from the wet parts of the mire dominated by a rather homogenous cover of Eriophorum angustifolium. The CO₂/CH₄ flux measurements performed during the years 2001–2008 showed that the areas represented in the measurements were a relatively stable sink of carbon with an average annual rate of uptake amounting to on average ?46 g C m^?2 y^?1 including an equally stable loss through CH₄ emissions (18–22 g CH₄–C m^?2 y^?1). This consistent carbon sink combined with substantial CH₄ emissions is most likely what is to be expected as the permafrost under palsa mires degrades in response to climate warming.     

A field trial of nutrient stimulation of methanotrophs to reduce greenhouse gas emissions from landfill cover soils

Landfills are among the major sources of anthropogenic methane (CH₄) estimated to reach 40?×?10⁹kg per year worldwide by 2015 (IPCC, 2007 IPCC. 2007. Intergovernmental Panel on Climate Change, Synthesis Report on Contributions of Work Groups 1, 2, and 3 to the Fourth Assessment Report Core Writing Team, Edited by: Pauchar, R.K. and Reisinger, A. Geneva, Switzerland: IPCC.  [Google Scholar]). A 2½-year field experiment was conducted at a closed landfill in western Michigan where methanotrophs, methane-consuming bacteria, were stimulated by nutrient addition to the soil without significantly increasing biogenic nitrous oxide (N₂O) production. The effects of the nitrogen amendments (KNO₃ and NH₄Cl), phenylacetylene (a selective inhibitor of nitrifying bacteria that contribute to N₂O production), and a canopy (to reduce direct water infiltration) on the vertical soil gas profiles of CH₄, CO₂, and O₂ were measured in the top meter of the soil. Methane and nitrous oxide fluxes were calculated from the corresponding soil gas concentration gradients with respect to depth and a Millington–Quirk diffusivity coefficient in soil derived empirically from soil porosity, water content, and diffusivity coefficients in air from the literature. Methane flux estimates were as high as 218.4 g m^?2 day^?1 in the fall and 12.8 g/m^?2 day^?1 in the summer. During the spring and summer, CH₄ fluxes were reduced by more than half by adding KNO₃ and NH₄Cl into the soil as compared to control plots, while N₂O fluxes increased substantially. The concurrent addition of phenylacetylene to the amendment decreased peak N₂O production by half and the rate of peak methane oxidation by about one-third. The seasonal average methane and N₂O flux data were extrapolated to estimate the reduction of CH₄ and N₂O fluxes into the atmosphere by nitrogen and inhibitor addition to the cover soils. The results suggest that such additions coupled with soil moisture management may provide a potential strategy to significantly reduce greenhouse gas emissions from landfills.

Implications The results of a 2½-year study of effects of nutrient stimulation on methane oxidation in landfill cover soils demonstrates that nutrient addition does decrease methane emissions. The work further underscores the control which soil moisture exerts on methane oxidation. Water management is critical to the success of methane oxidation strategies.     

Wet precipitation chemistry at a high-altitude site (3,326 m a.s.l.) in the southeastern Tibetan Plateau

This paper presents the results of wet precipitation chemistry from September 2009 to August 2010 at a high-altitude forest site in the southeastern Tibetan Plateau (TP). The alkaline wet precipitation, with pH ranging from 6.25 to 9.27, was attributed to the neutralization of dust in the atmosphere. Wet deposition levels of major ions and trace elements were generally comparable with other alpine and remote sites around the world. However, the apparently greater contents/fluxes of trace elements (V, Co, Ni, Cu, Zn, and Cd), compared to those in central and southern TP and pristine sites of the world, reflected potential anthropogenic disturbances. The almost equal mole concentrations and perfect linear relationships of Na⁺ and Cl^? suggested significant sea-salts sources, and was confirmed by calculating diverse sources. Crust mineral dust was responsible for a minor fraction of the chemical components (less than 15 %) except Al and Fe, while most species (without Na⁺, Cl^?, Mg²⁺, Al, and Fe) arose mainly from anthropogenic activities. High values of as-K⁺ (anthropogenic sources potassium), as-SO₄ ^2?, and as-NO₃ ^? observed in winter and spring demonstrated the great effects of biomass burning and fossil fuel combustion in these seasons, which coincided with haze layer outburst in South Asia. Atmospheric circulation exerted significant influences on the chemical components in wet deposition. Marine air masses mainly originating from the Bay of Bengal provided a large number of sea salts to the chemical composition, while trace elements during summer monsoon seasons were greatly affected by industrial emissions from South Asia. The flux of wet deposition was 1.12 kg?N?ha^?1?year^?1 for NH₄ ⁺–N and 0.29 kg?N?ha^?1?year^?1 for NO₃ ^?–N. The total atmospheric deposition of N was estimated to be 6.41 kg?N?ha^?1?year^?1, implying potential impacts on the alpine ecosystem in this region.     

Effect of compost and manure amendments on zinc soil speciation, plant content, and translocation in an artificially contaminated soil

The addition of organic matter in soil can modify the bioavailability of heavy metals. A greenhouse pot experiment was carried out using an edible plant species Eruca vesicaria L. Cavalieri grown on an artificially contaminated soil with Zn (665 mg?kg^?1). In this study, the effect of compost at 20 t?ha^?1 (C20) and at 60 t?ha^?1 (C60), manure at 10 t?ha^?1 (M10) and at 30 t?ha^?1 (M30), and chemical fertilizers (NPK) on Zn fate in a soil–plant system was evaluated. At the end of the experiment, the main growth parameters and Zn content in plants were determined. In addition, Zn speciation in the soil was assessed using the original Community Bureau of Reference sequential extraction and diethylene triamine pentaacetic acid extraction. Zinc, though an essential element for plant growth, caused toxicity effects in plants grown on control and manure treatments, while in the compost treatments, plants showed no visual toxicity symptoms. The concentrations of Zn in roots were similar for all treatments, while significant differences were observed for shoots. In fact, in the compost treatments, plants showed the lowest Zn concentration in shoots. Zinc speciation seems not to be affected by the applied treatments. Indeed, Zn plant content and translocation to shoots seems to be affected. Compost amendments significantly reduced Zn content and translocation in comparison to other treatments.     

Remediation of acid mine drainage (AMD)-contaminated soil by Phragmites australis and rhizosphere bacteria

Experiments were conducted to assess the impact of citric acid (CA) and rhizosphere bacteria on metal uptake in Phragmites australis cultured in a spiked acid mine drainage (AMD) soil. Rhizosphere iron-oxidizing bacteria (Fe(II)OB) enhanced the formation of Fe plaque on roots, which decreased the uptake of Fe and Mn. CA inhibited the growth of Fe(II)OB, decreased the formation of metal plaque, raised the metal mobility in soil, and increased the accumulation of metals in all tissues of the reeds. The higher the CA dosage, the more metals accumulated into reeds. The total amount of metals in reeds increased from 7.8?±?0.5?×?10^?6 mol plant^?1 (Mn), 1.4?±?0.1?×?10^?3 mol plant^?1 (Fe), and 1.0?±?0.1?×?10^?4 mol plant^?1 (Al) in spiked soil without CA to 22.2?±?0.5?×?10^?6 mol plant^?1 (Mn), 3.5?±?0.06?×?10^?3 mol plant^?1 (Fe), and 5.0?±?0.2?×?10^?4 mol plant^?1 (Al) in soil added with 33.616 g C₆H₈O₇·H₂O for per kilogram soil. CA could be effective at enhancing the phytoremediation of metals from AMD-contaminated soil.     

FTIR gas-phase kinetic study on the reactions of some acrylate esters with OH radicals and Cl atoms

Acrylate esters are α,β-unsaturated esters that contain vinyl groups directly attached to the carbonyl carbon. These compounds are widely used in the production of plastics and resins. Atmospheric degradation processes of these compounds are currently not well understood. The kinetics of the gas phase reactions of OH radicals with methyl 3-methylacrylate and methyl 3,3-dimethylacrylate were determined using the relative rate technique in a 50 L Pyrex photoreactor using in situ FTIR spectroscopy at room temperature (298?±?2 K) and atmospheric pressure (708?±?8 Torr) with air as the bath gas. Rate coefficients obtained were (in units cm³ molecule^?1 s^?1): (3.27?±?0.33)?×?10^?11 and (4.43?±?0.42)?×?10^?11, for CH₃CH═CHC(O)OCH₃ and (CH₃)₂CH═CHC(O)OCH_3, respectively. The same technique was used to study the gas phase reactions of hexyl acrylate and ethyl hexyl acrylate with OH radicals and Cl atoms. In the experiments with Cl, N₂ and air were used as the bath gases. The following rate coefficients were obtained (in cm³ molecule^?1 s^?1): k₃ (CH₂═CHC(O)O(CH₂)₅CH₃?+?Cl)?=?(3.31?±?0.31)?×?10^?10, k₄(CH₂═CHC(O)OCH₂CH(CH₂CH₃)(CH₂)₃CH₃?+?Cl)?=?(3.46?±?0.31)?×?10^?10, k₅(CH₂═CHC(O)O(CH₂)₅CH₃?+?OH)?=?(2.28?±?0.23)?×?10^?11, and k₆(CH₂═CHC(O)OCH₂CH(CH₂CH₃)(CH₂)₃CH₃?+?OH)?=?(2.74?±?0.26)?×?10^?11. The reactivity increased with the number of methyl substituents on the double bond and with the chain length of the alkyl group in –C(O)OR. Estimations of the atmospheric lifetimes clearly indicate that the dominant atmospheric loss process for these compounds is their daytime reaction with the hydroxyl radical. In coastal areas and in some polluted environments, Cl atom-initiated degradation of these compounds can be significant, if not dominant. Maximum Incremental Reactivity (MIR) index and global warming potential (GWP) were also calculated, and it was concluded that these compounds have significant MIR values, but they do not influence global warming.     

Impacts of feedlot floor condition,deposition frequency,and inhibitors on N2O and CH4 emissions from feedlot dung and urine patches

Patches of dung and urine are major contributors to the feedlot gas emissions. This study investigated the impacts of dung deposition frequency (partly reflecting animal stocking density of a feedlot), dairy feedlot floor conditions (old floor indicated with the presence of consolidated manure pad [CMP] vs. new floor with the absence of consolidated manure pad [CMPn]), and application of dicyandiamide (DCD) and hydroquinone (HQ) on nitrous oxide (N₂O) and methane (CH₄) emissions from patches in the laboratory, and the integrative impacts were expressed in terms of global warming potential (CO₂-equivalent). Dung deposition frequency, feedlot floor condition, and application of inhibitors showed inverse impacts on N₂O and CH₄ emissions from patches. Greenhouse gas (GHG) emissions from the dung, urine, and dung+urine patches on the CMP feedlot surface were approximately 7.48, 87.35, and 7.10 times those on the CMPn feedlot surface (P < 0.05). Meanwhile, GHG emissions from CMP and CMPn feedlot surfaces under high deposition frequency condition were approximately 10 and 1.7 times those under low-frequency condition. Moreover, application of HQ slightly reduced the GHG emission from urine patches, by 14.9% (P > 0.05), while applying DCD or DCD+HQ significantly reduced the GHG, by 60.3% and 65.0%, respectively (P < 0.05). Overall, it is necessary to include feedlot management such as animal stocking density and feedlot floor condition to the process of determining emission factors for feedlots. In the future, field measurements to quantitatively evaluate the relative contribution of nitrification and denitrification to the N₂O emissions of feedlot surfaces are highly required for effective N₂O control.

Implications: This study shows that feedlot CH₄ and N₂O emissions inversely respond to the dicyandiamide (DCD) application. Applying DCD significantly reduces GHG emissions of feedlot urine patches. Feedlot floor condition and stocking density strongly impact feedlot GHG emissions. Including feedlot floor condition and stocking density in the feedlot EF determining process is necessary.     

Moist Olive Husks Addition to a Silty Clay Soil: Influence on Microbial and Biochemical Parameters

To investigate the effects of moist olive husks (MOH-residues) on soil respiration, microbial biomass, and enzymatic (o-diphenoloxidase, β-glucosidase, dehydrogenase and alkaline phosphatase) activities, a silty clay soil was incubated with 0 (control), 8 × 10³ (D), 16 × 10³ (2D) and 80 × 10³ (10D) kg ha^?1 of MOH-residues on a dry weight basis. Soil respiration and microbial biomass data indicated that the addition of MOH-residues strongly increased microbial activity proportionally to the amounts added. Data of qCO₂ suggested that the respiration to biomass ratio of the microbial population was strongly modified by MOH-residues additions during the first 90 days of incubation. The qCO₂ data suggested a low efficiency in energy yields from C oxidation during the first 2 months of soil incubation. qFDA seemed to be relatively unaffected for treatments D and 2D as compared to the control, but was significantly lowered by the application of 10D, showing the lowest hydrolytic activity of microbial biomass in this treatment up to 360 days of incubation.

o-Diphenoloxidase activity was delayed, and this delay was extended with the addition of larger quantities of MOH-residues. Alkaline phosphatase, β-glucosidase and dehydrogenase activities were in line with the findings on microbial biomass changes and activities. The biological and biochemical data suggest that the addition of a large quantity of MOH-residues (80 × 10³ kg ha^?1) strongly modifies the soil characteristics affecting the r- and K-strategist populations, and that these changes last for at least the 360 days of incubation. The data also suggest that application rates exceeding 16 × 10³ kg ha^?1 are not recommended until the agro-chemical and -physical functions of the soil are further studied.     

Concentration and dissipation of chlorantraniliprole and thiamethoxam residues in maize straw,maize, and soil

To study the dissipation rates and final residual levels of chlorantraniliprole and thiamethoxam in maize straw, maize, and soil, two independent field trials were conducted during the 2014 cropping season in Beijing and Anhui Provinces of China. A 40% wettable powder (20% chlorantraniliprole?+?20% thiamethoxam) was sprayed onto maize straw and soil at an application rate of 118 g of active ingredient per hectare (g a.i.ha^?1). The residual concentrations were determined by ultra-high-performance liquid chromatography–tandem mass spectrometry. The chlorantraniliprole half-lives in maize straw and soil were 9.0–10.8 and 9.5–21.7 days, respectively. The thiamethoxam half-lives in maize straw and soil were 8.4–9.8 and 4.3–11.7 days, respectively. The final residues of chlorantraniliprole and thiamethoxam in maize straw, maize, and soil were measured after the pesticides had been sprayed two and three times with an interval of 7 days using 1 and 1.5 times the recommended rate (72 g a.i. ha^?1 and 108 g a.i. ha^?1, respectively). Representative maize straw, maize, and soil samples were collected after the last treatment at pre-harvest intervals of 7, 14, and 28 days. The chlorantraniliprole residue was below 0.01 mg kg^?1 in maize, between 0.01 and 0.31 mg kg^?1 in maize straw, and between 0.03 and 1.91 mg kg^?1 in soil. The thiamethoxam residue concentrations in maize, maize straw, and soil were <0.01, <0.01, and 0.01–0.03 mg kg^?1, respectively. The final pesticide residues on maize were lower than the maximum residue limit (MRL) of 0.02 mg kg^?1 after a 14-day pre-harvest interval. Therefore, a dosage of 72 g a.i. ha^?1 was recommended, as it can be considered safe to human beings and animals.     

Mitigating Global Warming Potentials of Methane and Nitrous Oxide Gases from Rice Paddies under different irrigation regimes

A field experiment was conducted in Bangladesh Agricultural University Farm to investigate the mitigating effects of soil amendments such as calcium carbide, calcium silicate, phosphogypsum, and biochar with urea fertilizer on global warming potentials (GWPs) of methane (CH₄) and nitrous oxide (N₂O) gases during rice cultivation under continuous and intermittent irrigations. Among the amendments phosphogypsum and silicate fertilizer, being potential source of electron acceptors, decreased maximum level of seasonal CH₄ flux by 25–27 % and 32–38 % in continuous and intermittent irrigations, respectively. Biochar and calcium carbide amendments, acting as nitrification inhibitors, decreased N₂O emissions by 36–40 % and 26–30 % under continuous and intermittent irrigations, respectively. The total GWP of CH₄ and N₂O gases were decreased by 7–27 % and 6–34 % with calcium carbide, phosphogypsum, and silicate fertilizer amendments under continuous and intermittent irrigations, respectively. However, biochar amendments increased overall GWP of CH₄ and N₂O gases.     

Methane biofiltration in the presence of ethanol vapor under steady and transient state conditions: an experimental study

Methane (CH₄) removal in the presence of ethanol vapors was performed by a stone-based bed and a hybrid packing biofilter in parallel. In the absence of ethanol, a methane removal efficiency of 55 ± 1% was obtained for both biofilters under similar CH₄ inlet load (IL) of 13 ± 0.5 g_CH4 m^?3 h^?1 and an empty bed residence time (EBRT) of 6 min. The results proved the key role of the bottom section in both biofilters for simultaneous removal of CH₄ and ethanol. Ethanol vapor was completely eliminated in the bottom sections for an ethanol IL variation between 1 and 11 g_ethanol m^?3 h^?1. Ethanol absorption and accumulation in the biofilm phase as well as ethanol conversion to CO₂ contributed to ethanol removal efficiency of 100%. In the presence of ethanol vapor, CO₂ productions in the bottom section increased almost fourfold in both biofilters. The ethanol concentration in the leachate of the biofilter exceeding 2200 g_ethanol m^?3 _leachate in both biofilters demonstrated the excess accumulation of ethanol in the biofilm phase. The biofilters responded quickly to an ethanol shock load followed by a starvation with 20% decrease of their performance. The return to normal operations in both biofilters after the transient conditions took less than 5 days. Unlike the hybrid packing biofilter, excess pressure drop (up to 1.9 cmH₂O m^?1) was an important concern for the stone bed biofilter. The biomass accumulation in the bottom section of the stone bed biofilter contributed to 80% of the total pressure drop. However, the 14-day starvation reduced the pressure drop to 0.25 cmH₂O m^?1.     

Measuring and modeling nitrous oxide and methane emissions from beef cattle feedlot manure management: First assessments under Brazilian condition

Intensive beef production has increased during recent decades in Brazil and may substantially increase both methane (CH₄) and nitrous oxide (N₂O) emissions from manure management. However, the quantification of these gases and methods for extrapolating them are scarce in Brazil. A case study examines CH₄ and N₂O emissions from one typical beef cattle feedlot manure management continuum in Brazil and the applicability of Manure-DNDC model in predicting these emissions for better understand fluxes and mitigation options. Measurements track CH₄ and N₂O emissions from manure excreted in one housing floor holding 21 animals for 78 days, stockpiled for 73 days and field spread (360 kg N ha^?1). We found total emissions (CH₄ + N₂O) of 0.19 ± 0.10 kg CO₂eq per kg of animal live weight gain; mostly coming from field application (73%), followed housing (25%) and storage (2%). The Manure-DNDC simulations were generally within the statistical deviation ranges of the field data, differing in ?28% in total emission. Large uncertainties in measurements showed the model was more accurate estimating the magnitude of gases emissions than replicate results at daily basis. Modeled results suggested increasing the frequency of manure removal from housing, splitting the field application and adopting no-tillage system is the most efficient management for reducing emissions from manure (up to about 75%). Since this work consists in the first assessment under Brazilian conditions, more and continuous field measurements are required for decreasing uncertainties and improving model validations. However, this paper reports promising results and scientific perceptions for the design of further integrated work on farm-scale measurements and Manure-DNDC model development for Brazilian conditions.     

Identification and quantification of methyl halide sources in a lowland tropical rainforest

In conjunction with the OP3 campaign in Danum Valley, Malaysian Borneo, flux measurements of methyl chloride (CH₃Cl) and methyl bromide (CH₃Br) were performed from both tropical plant branches and leaf litter in June and July 2008. Live plants were mainly from the Dipterocarpaceae family whilst leaf litter samples were representative mixtures of different plant species. Environmental parameters, including photosynthetically-active radiation, total solar radiation and air temperature, were also recorded. The dominant factor determining magnitude of methyl halide fluxes from living plants was plant species, with specimens of the genus Shorea showing persistent high emissions of both gases, e.g. Shorea pilosa: 65 ± 17 ng CH₃Cl h^?1 g^?1 (dry weight foliage) and 2.7 ± 0.6 ng CH₃Br h^?1 g^?1 (dry weight foliage). Mean CH₃Cl and CH₃Br emissions across 18 species of plant were 19 (range, <LOD ?76) and 0.4 (<LOD ?2.9) ng h^?1 g^?1 respectively; fluxes from leaf litter were 1–2 orders of magnitude smaller per dry mass. CH₃Cl and CH₃Br fluxes were weakly correlated. Overall, the findings suggest that tropical rainforests make an important contribution to global terrestrial emissions of CH₃Cl, but less so for CH₃Br.