Vegetative buffers for fan emissions from poultry farms: 1. temperature and foliar nitrogen

This study sought to evaluate the potential of trees planted around commercial poultry farms to trap ammonia (NH₃), the gas of greatest environmental concern to the poultry industry. Four plant species (Norway spruce, Spike hybrid poplar, Streamco willow, and hybrid willow) were planted on eight commercial farms from 2003 to 2004. Because temperature (T) can be a stressor for trees, T was monitored in 2005 with data loggers among the trees in front of the exhaust fans (11.4 to 17.7 m) and at a control distance away from the fans (48 m) during all four seasons in Pennsylvania. Norway spruce (Picea abies) foliage samples were taken in August 2005 from one turkey and two layer farms for dry matter (DM) and nitrogen (N) analysis. The two layer farms had both Norway spruce and Spike hybrid poplar (Populus deltoides × Populus nigra) plantings sampled as well allowing comparisons of species and the effect of plant location near the fans versus a control distance away. Proximity to the fans had a clear effect on spruce foliar N with greater concentrations downwind of the fans than at control distances (3.03 vs. 1.88%; P ≤ 0.0005). Plant location was again a significant factor for foliar N of both poplar and spruce on the two farms with both species showing greater N adjacent to the fans compared to the controls (3.75 vs. 2.32%; P ≤ 0.0001). Pooled foliar DM of both plants was also greater among those near the fans (56.17, fan vs. 44.67%, control; P ≤ 0.005). Species differences were also significant showing the potential of poplar to retain greater foliar N than spruce (3.52 vs. 2.55%; P ≤ 0.001) with less DM (46.00 vs. 54.83%; P ≤ 0.05) in a vegetative buffer setting. The results indicated plants were not stressed by the T near exhaust fans with mean seasonal T (13.04 vs. 13.03°C, respectively) not significantly different from controls. This suggested poultry house exhaust air among the trees near the fans would not result in dormancy stressors on the plants compared to controls away from the fans.     

Vegetative buffers for fan emissions from poultry farms: 2. ammonia, dust and foliar nitrogen

This study evaluated the potential of trees planted around commercial poultry farms to trap ammonia (NH(3)) and dust or particulate matter (PM). Norway spruce, Spike hybrid poplar, hybrid willow, and Streamco purpleosier willow were planted on five commercial farms from 2003 to 2004. Plant foliage was sampled in front of the exhaust fans and at a control distance away from the fans on one turkey, two laying hen, and two broiler chicken farms between June and July 2006. Samples were analyzed for dry matter (DM), nitrogen (N), and PM content. In addition, NH(3) concentrations were measured downwind of the exhaust fans among the trees and at a control distance using NH(3) passive dosi-tubes. Foliage samples were taken and analyzed separately based on plant species. The two layer farms had both spruce and poplar plantings whereas the two broiler farms had hybrid willow and Streamco willow plantings which allowed sampling and species comparisons with the effect of plant location (control vs. fan). The results showed that NH(3) concentration h(- 1) was reduced by distance from housing fans (P < or = 0.0001), especially between 0 m (12.01 ppm), 11.4 m (2.59 ppm), 15 m (2.03 ppm), and 30 m (0.31 ppm). Foliar N of plants near the fans was greater than those sampled away from the fans for poplar (3.87 vs. 2.56%; P < or = 0.0005) and hybrid willow (3.41 vs. 3.02%; P < or = 0.05). The trends for foliar N in spruce (1.91 vs. 1.77%; P = 0.26) and Streamco willow (3.85 vs. 3.33; P = 0.07) were not significant. Pooling results of the four plant species indicated greater N concentration from foliage sampled near the fans than of that away from the fans (3.27 vs. 2.67%; P < or = 0.0001). Foliar DM concentration was not affected by plant location, and when pooled the foliar DM of the four plant species near the fans was 51.3% in comparison with 48.5% at a control distance. There was a significant effect of plant location on foliar N and DM on the two layer farms with greater N and DM adjacent to fans than at a control distance (2.95 vs. 2.15% N and 45.4 vs. 38.2% DM, respectively). There were also significant plant species effects on foliar N and DM with poplar retaining greater N (3.22 vs. 1.88%) and DM (43.7 vs. 39.9%) than spruce. The interaction of location by species (P < or = 0.005) indicated that poplar was more responsive in terms of foliar N, but less responsive for DM than spruce. The effect of location and species on foliar N and DM were not clear among the two willow species on the broiler farms. Plant location had no effect on plant foliar PM weight, but plant species significantly influenced the ability of the plant foliage to trap PM with spruce and hybrid willow showing greater potential than poplar and Streamco willow for PM(2.5)(0.0054, 0.0054, 0.0005, and 0.0016 mg cm(- 2); P < or = 0.05) and total PM (0.0309, 0.0102, 0.0038, and 0.0046 mg cm(- 2), respectively; P < or = 0.001). Spruce trapped more dust compared to the other three species (hybrid willow, poplar, and Streamco willow) for PM(10) (0.0248 vs. 0.0036 mg cm(- 2); P < or = 0.0001) and PM(> 10) (0.0033 vs. 0.0003 mg cm(- 2); P = 0.052). This study indicates that poplar, hybrid willow, and Streamco willow are appropriate species to absorb poultry house aerial NH(3)-N, whereas spruce and hybrid willow are effective traps for dust and its associated odors.     

Vegetative buffers for fan emissions from poultry farms: 1. temperature and foliar nitrogen

This study sought to evaluate the potential of trees planted around commercial poultry farms to trap ammonia (NH(3)), the gas of greatest environmental concern to the poultry industry. Four plant species (Norway spruce, Spike hybrid poplar, Streamco willow, and hybrid willow) were planted on eight commercial farms from 2003 to 2004. Because temperature (T) can be a stressor for trees, T was monitored in 2005 with data loggers among the trees in front of the exhaust fans (11.4 to 17.7 m) and at a control distance away from the fans (48 m) during all four seasons in Pennsylvania. Norway spruce (Picea abies) foliage samples were taken in August 2005 from one turkey and two layer farms for dry matter (DM) and nitrogen (N) analysis. The two layer farms had both Norway spruce and Spike hybrid poplar (Populus deltoides x Populus nigra) plantings sampled as well allowing comparisons of species and the effect of plant location near the fans versus a control distance away. Proximity to the fans had a clear effect on spruce foliar N with greater concentrations downwind of the fans than at control distances (3.03 vs. 1.88%; P < or = 0.0005). Plant location was again a significant factor for foliar N of both poplar and spruce on the two farms with both species showing greater N adjacent to the fans compared to the controls (3.75 vs. 2.32%; P < or = 0.0001). Pooled foliar DM of both plants was also greater among those near the fans (56.17, fan vs. 44.67%, control; P < or = 0.005). Species differences were also significant showing the potential of poplar to retain greater foliar N than spruce (3.52 vs. 2.55%; P < or = 0.001) with less DM (46.00 vs. 54.83%; P < or = 0.05) in a vegetative buffer setting. The results indicated plants were not stressed by the T near exhaust fans with mean seasonal T (13.04 vs. 13.03 degrees C, respectively) not significantly different from controls. This suggested poultry house exhaust air among the trees near the fans would not result in dormancy stressors on the plants compared to controls away from the fans.     

Growth and Foliar Nitrogen Status of Four Plant Species Exposed to Atmospheric Ammonia

A chamber study was conducted to evaluate the growth response and leaf nitrogen (N) status of four plant species exposed to continuous ammonia (NH₃) for 12 weeks (wk). This was intended to evaluate appropriate plant species that could be used to trap discharged NH₃ from the exhaust fans in poultry feeding operations before moving off-site. Two hundred and forty bare-root plants of four species (Juniperus virginiana (red cedar), Gleditsia triacanthos var. inermis (thornless honey locust), Populus sp. (hybrid poplar), and Phalaris arundinacea (reed canary grass) were transplanted into 4- or 8-L polyethylene pots and grown in four environmentally controlled chambers. Plants placed in two of the four chambers received continuous exposure to anhydrous NH₃ at 4 to 5 ppm while plants in another two chambers received no NH₃. In each of the four chambers, 2 to 4 plants per species received no fertilizer while the rest of the plants were fertilized with a 100 ppm solution containing 21% N, 7% phosphorus, and 7% potassium. The results showed that honey locust was the fastest-growing species. The superior growth of honey locust among all species was also supported by its total biomass, root, and root dry matter (DM) weights. For all species there was a trend for plants exposed to NH₃ to have greater leaf DM than their non-exposed counterparts at 6 (43.0 vs. 30.8%; P = 0.09) and 12 wk (47.9 vs. 36.6%; P = 0.07), and significantly greater (P ≤ 0.05) leaf N content at 6 (6.44 vs. 3.67%) and 12 wk (7.05 vs. 3.51%) when exposed to NH₃. Numerically greater leaf DM due to NH₃ exposure was also consistently measured in poplar at both sampling periods. Hybrid poplar, as well as honey locust and reed canary grass, deposited 1.5 to 2-fold greater N in their leaves than red cedar tissues as a result of NH₃ exposure compared to non-exposed plants. Regardless of the effect of NH₃ on foliar color and damage score of the plants, the increase of foliar N content (g 100 g^?1 of fresh foliage weight) after NH₃ exposure at 6 and 12 wk was 0.45 and 0.87 for grass,1.25 and 1.34 for locust, and 2.67 and 6.09 for poplar. However, only honey locust likely benefited from ambient NH₃ as indicated by its consistent leaf color quality and lower damage score, compared with other species that were adversely affected by atmospheric NH₃.     

Growth and foliar nitrogen status of four plant species exposed to atmospheric ammonia

A chamber study was conducted to evaluate the growth response and leaf nitrogen (N) status of four plant species exposed to continuous ammonia (NH3) for 12 weeks (wk). This was intended to evaluate appropriate plant species that could be used to trap discharged NH3 from the exhaust fans in poultry feeding operations before moving off-site. Two hundred and forty bare-root plants of four species (Juniperus virginiana (red cedar), Gleditsia triacanthos var. inermis (thornless honey locust), Populus sp. (hybrid poplar), and Phalaris arundinacea (reed canary grass) were transplanted into 4- or 8-L polyethylene pots and grown in four environmentally controlled chambers. Plants placed in two of the four chambers received continuous exposure to anhydrous NH3 at 4 to 5 ppm while plants in another two chambers received no NH3. In each of the four chambers, 2 to 4 plants per species received no fertilizer while the rest of the plants were fertilized with a 100 ppm solution containing 21% N, 7% phosphorus, and 7% potassium. The results showed that honey locust was the fastest-growing species. The superior growth of honey locust among all species was also supported by its total biomass, root, and root dry matter (DM) weights. For all species there was a trend for plants exposed to NH3 to have greater leaf DM than their non-exposed counterparts at 6 (43.0 vs. 30.8%; P = 0.09) and 12 wk (47.9 vs. 36.6%; P = 0.07), and significantly greater (P 相似文献   

Treatment of landfill leachate by irrigation of willow coppice - Plant response and treatment efficiency

Landfill leachates usually need to be treated before discharged, and using soil-plant systems for this has gained substantial interest in Sweden and in the UK. A three-year field study was conducted in central Sweden to quantify plant response, treatment efficiency and impact on groundwater quality of landfill leachate irrigation of short-rotation willow coppice (Salix). Two willow varieties were tested and four irrigation regimes in sixteen 400-m² plots. The willow plants did not react negatively, despite very high annual loads of nitrogen (≤2160 kg N/ha), chloride (≤8600 kg Cl/ha) and other elements. Mean annual growth was 1.5, 9.8 and 12.6 tonnes DM/ha during years 1-3. For one of two willow varieties tested, relative leaf length accurately predicted growth rate. Irrigation resulted in elevated groundwater concentrations of all elements applied. Treatment efficiency varied considerably for different elements, but was adequate when moderate loads were applied.     

Experimental investigation of vegetative environment buffers in reducing particulate matters emitted from ventilated poultry house

Scientists have effectively proved that vegetative environment buffers (VEBs) can be used for reducing dust emissions from livestock buildings, but they have seen fewer tests in poultry farms. A field research was conducted to assess the effectiveness of VEBs on reducing downwind transport of particulate matter (PM) from a ventilated poultry house in Changchun. Five plant species transferred from local area were used to establish five diverse VEBs and separately installed outside of the ventilation fans in summer 2017. The five plant species were Winged Euonymus (WE), Malus Spectabilis (MS), Padus Maackii (PAA), Acer Saccharum Marsh (ASM), and Padus Virginiana “Red Select Shrub” (PV_RSS). The mass concentrations of PM_2.5 and PM₁₀ (particulate matter with an aerodynamic diameter of 2.5 μm and 10 μm or less, respectively) were monitored at downwind and upwind sampling locations around the VEB. The results showed that with the presenting of VEBs, the particle concentrations at the downwind sampling point were significantly reduced compared with that at the upwind sampling point (p < 0.05). Specifically, compared to the control test without VEB, the VEB with PV_RSS had the best PM concentration reduction rate (CRR) of 47.24%±4.33% and 41.13%±5.83% for PM_2.5 and PM₁₀, respectively. The rough surface of plant leaves may help intercept more PM, though it was also affected by other factors (such as the blade angle, the interaction with wind) needed to be further investigated. The VEB with PV_RSS, which presented the best capacity of CRR, selectively intercepted PM, mainly related to the elements of N, Na, Mg, P, S, and Cl.

Implications: Five plant species, including WE, PAA, MS, ASM, and PV_RSS, were evaluated as VEBs to mitigate particulate emissions from outside of a ventilated poultry house in Changchun. They all significantly reduced particulate matter emissions. However, the PV_RSS presented the best capability of trapping fine and coarse particles: PM_2.5 and PM₁₀, respectively, while the PAA was the worst one. The microstructure of leaves affected particle deposition and remaining on the leaves, and PV_RSS selectively intercepted particulate matter mainly related to certain elements.     

Responses of Hybrid Poplar Trees to Sulfur Dioxide Fumigation

This paper verifies the presence of significant interclonal variation in the tolerance of hybrid poplar (Populus deltoides Bartr. cv. Angulata × P. trichocarpa Torr. and Gray) to sulfur dioxide fumigation. Rooted stem cuttings of four hybrid poplar clones were exposed to 5 ppm sulfur dioxide for 0, 3, 6, 9, or 12 hours in controlled environment chambers. Multivariate analyses were made from the shoot growth measurements recorded for 4 weeks before and after fumigation and on the data of foliar injury induced by sulfur dioxide. The following factors were statistically significant in determining growth response and foliar injury: (1) genotype; (2) duration of treatment; and (3) interaction between genotype and hours of fumigation. All partial correlations between foliar injury and subsequent shoot growth were positive and significant. Sufficient genetic variation appears to exist in this Populus hybrid to encourage selection of clones tolerant to short-term exposures of high levels of sulfur dioxide.     

Stable isotope signatures reflect competitiveness between trees under changed CO2/O3 regimes

Here we synthesize key findings from a series of experiments to gain new insight on inter-plant competition between juvenile beech (Fagus sylvatica) and spruce (Picea abies) under the influence of increased O₃ and CO₂ concentrations. Competitiveness of plants was quantified and mechanistically interpreted as space-related resource investments and gains. Stable isotopes were addressed as temporal integrators of plant performance, such as photosynthesis and its relation to water use and nitrogen uptake. In the weaker competitor, beech, efficiency in space-related aboveground resource investment was decreased in competition with spruce and positively related to Δ¹³C, as well as stomatal conductance, but negatively related to δ¹⁸O. Likewise, our synthesis revealed that strong belowground competition for water in spruce was paralleled in this species by high N assimilation capacity. We suggest combining the time-integrative potential of stable isotopes with space-related investigations of competitiveness to accomplish mechanistic understanding of plant competition for resources.     

Influence of additives in the end‐use mixes of tebufenozide on deposition,adhesion and persistence in spruce foliage

Abstract

A commercial flowable formulation of tebufenozide, RH‐5992 2F [N'‐t‐butyl‐N'‐(3,5‐dimethylbenzoyl)‐N‐(4‐ethylbenzoyl) hydrazine], was diluted with water, water and canola oil, and water and the methyl ester of canola oil, to provide six end‐use mixes with concentrations of 35 and 70 g of active ingredient (Al) litre^‐1. The mixes were applied at 70 and 140 g Al ha^‐1 over white spruce [Picea glauca (Moench) Voss] seedlings in a laboratory spray chamber and foliar concentrations of tebufenozide were determined over a 60‐d period. At intervals of time post‐spray, seedlings were sprayed with monosized droplets of Sunspray®11N as rainfall, and the amount of tebufenozide knocked off from foliage was determined. The potential energy of adhesion (PEA) of the Al particles on the foliage increased with time and varied according to the type of end‐use mix, its viscosity and the dosage sprayed.

The end‐use mixes were applied over white spruce trees under field conditions and persistence of tebufenozide was investigated. DT₅₀ values were influenced by the type of mix and dosage sprayed. Oil‐containing mixes and higher dosages increased the PEA of tebufenozide particles.     

Assessing the potential for rhizoremediation of PCB contaminated soils in northern regions using native tree species

Rhizosphere bioremediation of polychlorinated biphenyls (PCBs) offers a potentially inexpensive approach to remediating contaminated soils that is particularly attractive in remote regions including the Arctic. We assessed the abilities of two tree species native to Alaska, Salix alaxensis (felt-leaf willow) and Picea glauca (white spruce), to promote microbial biodegradation of PCBs via the release of phytochemicals upon fine root death. Crushed fine roots, biphenyl (PCB analogue) or salicylate (willow secondary compound) were added to microcosms containing soil spiked with PCBs and resultant PCB disappearance, soil toxicity and microbial community changes were examined. After 180 d, soil treated with willow root crushates showed a significantly greater PCB loss than untreated soils for some PCB congeners, including the toxic congeners, PCB 77, 105 and 169, and showed a similar PCB loss pattern (in both extent of degradation and congeners degraded) to biphenyl-treated microcosms. Neither P. glauca (white spruce) roots nor salicylate enhanced PCB loss, indicating that biostimulation is plant species specific and was not mediated by salicylate. Soil toxicity assessed using the Microtox bioassay indicated that the willow treatment resulted in a less toxic soil environment. Molecular microbial community analyses indicated that biphenyl and salicylate promoted shifts in microbial community structure and composition that differed distinctly from each other and from the crushed root treatments. The biphenyl utilizing bacterium, Cupriavidus spp. was isolated from the soil. The findings suggest that S. alaxensis may be an effective plant for rhizoremediation by altering microbial community structure, enhancing the loss of some PCB congeners and reducing the toxicity of the soil environment.     

Evaluation of Vegetation Near Coal-burning Power Plants in Southwestern Pennsylvania. II. Ozone Injury on Foliage of Hybrid Poplar

The objective of this study was to determine if the incidence or severity of foliar injury induced by regional, ambient ozone was influenced by local emissions from a complex of coal-burning power plants in southwestern Pennsylvania. Plantings of an ozonesensitive hybrid poplar clone {Populus maximowizii x trichocarpa, clone NE 388) were established in 1972 at various distances and directions from the power plants. Foliar injury caused by ambient ozone was evaluated annually from 1973 to 1990 in early to mid- August. Data are presented for the 12-year period, 1979 to 1990 inclusive, for which the most complete data sets were available. Injury from ambient ozone varied spatially and temporally, but with little relationship to power plant location. There was an apparent negative relationship between emission trends and ozone-induced symptoms, but only for one power plant. The correlation between annual mean levels of ozone-induced stipple and frequency of days (per year) with a 1-hr ozone maximum exceeding 0.04 ppm was weak, but significant. Ozone-induced bifacial necrosis was not observed on the foliage of the hybrid poplar during the drought year of 1988 in spite of record high levels of ozone; however, ozoneinduced stipple was observed.     

Concentration,size, and density of total suspended particulates at the air exhaust of concentrated animal feeding operations

Total suspended particulate (TSP) samples were seasonally collected at the air exhaust of 15 commercial concentrated animal feeding operations (CAFOs; including swine finishing, swine farrowing, swine gestation, laying hen, and tom turkey) in the U.S. Midwest. The measured TSP concentrations ranged from 0.38 ± 0.04 mg m^?3 (swine gestation in summer) to 10.9 ± 3.9 mg m^?3 (tom turkey in winter) and were significantly affected by animal species, housing facility type, feeder type (dry or wet), and season. The average particle size of collected TSP samples in terms of mass median equivalent spherical diameter ranged from 14.8 ± 0.5 µm (swine finishing in winter) to 30.5 ± 2.0 µm (tom turkey in summer) and showed a significant seasonal effect. This finding affirmed that particulate matter (PM) released from CAFOs contains a significant portion of large particles. The measured particle size distribution (PSD) and the density of deposited particles (on average 1.65 ± 0.13 g cm^?3) were used to estimate the mass fractions of PM₁₀ and PM_2.5 (PM ≤10 and ≤2.5 μm, respectively) in the collected TSP. The results showed that the PM₁₀ fractions ranged from 12.7 ± 5.1% (tom turkey) to 21.1 ± 3.2% (swine finishing), whereas the PM_2.5 fractions ranged from 3.4 ± 1.9% (tom turkey) to 5.7 ± 3.2% (swine finishing) and were smaller than 9.0% at all visited CAFOs. This study applied a filter-based method for PSD measurement and deposited particles as a surrogate to estimate the TSP’s particle density. The limitations, along with the assumptions adopted during the calculation of PM mass fractions, must be recognized when comparing the findings to other studies.

Implications: The concentration, size, and density of TSP samples varied greatly with animal species, housing facility type, feeder type, and season, suggesting that PM emission data derived from limited measurements may not be readily applied to estimate the overall emission from concentrated animal feeding operations (CAFOs). This study also affirmed that particles released from CAFOs is of relatively high density (~1.65 g cm^?3) and with diameter mostly larger than 10 µm, indicating that regular PM abatement devices, such as cyclones, fabric filters, or even a simple downward-facing exhaust duct, may be employed to mitigate the TSP emission with acceptable efficiency.     

Optical and thermal characteristics of carbonaceous aerosols measured at an urban site in Gwangju,Korea, in the winter of 2011

Carbonaceous components (organic carbon [OC] and elemental carbon [EC]) and optical properties (light absorption and scattering) of fine particulate matter (aerodynamic diameter <2.5 μm; PM_2.5) were simultaneously measured at an urban site in Gwangju, Korea, during the winter of 2011. OC was further classified into OC1, OC2, OC3, and OC4, based on a temperature protocol using a Sunset OC/EC analyzer. The average OC and EC concentrations were 5.0 ± 2.5 and 1.7 ± 0.9 μg C m^?3, respectively. The average single-scattering albedo (SSA) at a wavelength of 550 nm was 0.58 ± 0.11, suggesting that the aerosols observed in the winter of 2011 had a local warming effect in this area. During the whole sampling period, “stagnant PM” and “long-range transport PM” events were identified. The light absorption coefficient (b_abs) was higher during the stagnant PM event than during the long-range transport PM event due to the existence of abundant light-absorbing OC during the stagnant PM event. In particular, the OC2 and OC3 concentrations were higher during the stagnant PM event than those during the long-range transport event, suggesting that OC2 and OC3 might be more related to the light-absorbing OC. The light scattering coefficient (b_scat) was similar between the events. On average, the mass absorption efficiency attributed to EC (σ_EC) was 9.6 m² g^?1, whereas the efficiency attributed to OC (σ_OC) was 1.8 m² g^?1 at λ = 550 nm. Furthermore, the σ_EC is comparable among the PM event days, but the σ_OC for the stagnant PM event was significantly higher than that for the long-range transport PM event (1.7 vs. 0.5).

Implications: Optical and thermal properties of carbonaceous aerosol were measured at Gwangju, and carbonaceous aerosol concentration and optical property varied between “stagnant PM” and “long-range transport PM” events. More abundant light absorbing OC was observed during the stagnant PM event.     

Effect of sunlight radiation,rainfall and droplet spectra of sprays on persistence of bacillus thuringiensis deposits after application of dipel® 76af formulation onto conifers

Abstract

The effect of sunlight radiation, rainfall and droplet spectra of sprays on per ‐sistence of a Bacillus thuringiensis subspp. kurstaki (Btk) formulation, DiPel^® 76AF, was examined after application onto spruce [Picea glauca (Moench) Voss] foliage. The investigation consisted of three studies: (i) Study I: a laboratory microcosm study to examine the photostability of DiPel 76AF deposits on foliage after different periods of exposure to two radiation intensities, (ii) Study II: a laboratory microcosm study to examine the rainfastness of foliar deposits after exposure to different amounts of rainfall consisting of two separate droplet spectra, and (iii) Study III: a field microcosm study to investigate the influence of two different droplet spectra of DiPel 76AF sprays on foliar persistence of Btk under natural weathering conditions. In all studies, persistence of Btk was investigated both by bioassay [using spruce budworm (Choristoneura fumiferana Clemens)] and total protein assay.

The findings of Study I indicated that bioactivity of foliar deposits decreased with increasing duration of exposure to radiation, and with increasing radiation intensity. The half‐life (DT₅₀, the exposure period required for 50% of the initial bioactivity to disappear) was 5.1 d for the low intensity, and 3.9 d for the higher intensity. In contrast with the bioassay results, the total protein levels [determined by the bicinchoninic acid (BCA) method] showed no decrease with increasing duration of exposure, or with increasing radiation intensity.

The findings of Study II indicated that bioactivity of foliar deposits decreased with increasing cumulative rainfall. A new term, RF₅₀ [the amount of rain (in mm) required to washoff 50% of the initial deposit], was introduced to understand the relationship between rainfall intensity and reduction in bioactivity. When the same amount of rain was applied in different droplet sizes, the RF₅₀ value was high (5.2 mm) for the small rain droplets, and was low (2.9 mm) for the large rain droplets. Similar to the bioassay results, the total protein concentrations (determined by the BCA method) decreased with increasing amount of rain and with increasing rainfall intensity. The RF₅₀ value (obtained using ng protein /cm²) was 5.4 mm for the small rain droplets, and was 3.4 mm for the large rain droplets.

The field microcosm study indicated that when DiPel 76AF was applied in small droplets (D_v.5 of 65 μm), the persistence of bioactivity was ca 8.0 d, whereas when it was applied in large droplets (D_v.5 of 130 nm) it was ca 11 d. Bioactivity decreased with time after spray, and the DT₅₀ was 1.98 d for the spray of small droplets, and 2.87 d for that of large droplets. Similar to the bioactivity, the total protein concentrations also decreased with time after spray, and the DT₅₀ values for the small and large droplet spectra were 3.45 and 6.07 d respectively.     

Plant phenology, growth and nutritive quality of Briza maxima: responses induced by enhanced ozone atmospheric levels and nitrogen enrichment

An assessment of the effects of tropospheric ozone (O₃) levels and substrate nitrogen (N) supplementation, singly and in combination, on phenology, growth and nutritive quality of Briza maxima was carried out. Two serial experiments were developed in Open-Top Chambers (OTC) using three O₃ and three N levels. Increased O₃ exposure did not affect the biomass-related parameters, but enhanced senescence, increased fiber foliar content (especially lignin concentration) and reduced plant life span; these effects were related to senescence acceleration induced by the pollutant. Added N increased plant biomass production and improved nutritive quality by decreasing foliar fiber concentration. Interestingly, the effects of N supplementation depended on meteorological conditions and plant physiological activity. N supplementation counteracted the O₃-induced senescence but did not modifiy the effects on nutritive quality. Nutritive quality and phenology should be considered in new definitions of the O₃ limits for the protection of herbaceous vegetation.     

Ammonia emissions from different pig production scales and their temporal variations in the North China Plain

ABSTRACT

Pig production systems in China are shifting from small to industrial scale. Significant variation in housing ammonia (NH₃) emissions can exist due to differences in diet, housing design, and management practices. However, there is a knowledge gap regarding the impacts of farm-scale in China, which may be critical in identifying hotspots and mitigation targets. Here, continuous in-situ NH₃ concentration measurements were made at pig farms of different scales for sows and fattening pigs over periods of 3–6 days during two different seasons (summer vs. winter). For the sow farms, NH₃ emission rates were greater at the small farm (summer: 0.52 g pig^?1 hr^?1; winter: 0.21 g pig^?1 hr^?1) than at the large farm (summer: 0.34 g pig^?1 hr^?1; winter: 0.12 g pig^?1 hr^?1). For the fattening pig farms, NH₃ emission rates were greater at the large farm (summer: 0.22 g pig^?1 hr^?1; winter: 0.16 g pig^?1 hr^?1) than at the small farm (summer: 0.19 g pig^?1 hr^?1; winter: 0.07 g pig^?1 hr^?1). Regardless of farm scale, the NH₃ emission rates measured in summer were greater than those in winter; the NH₃ emission rates were greater in the daytime than at the nighttime; a positive relationship (R² = 0.06–0.68) was established between temperature and NH₃ emission rate, whereas a negative relationship (R² = 0.10–0.47) was found between relative humidity and NH₃ emission rate. The effect of farm-scale on indoor NH₃ concentration could mostly be explained by the differences in ventilation rates between farms. The diurnal variation in NH₃ concentration could be partly explained by ventilation rate (R² = 0.48–0.78) in the small traditional farms and by emission rate (R² = 0.26–0.85) in the large industrial farms, except for the large fattening pig farm in summer. Overall, mitigation of NH₃ emissions from sow farms should be a top priority in the North China Plain.

Implications: The present study firstly examined the farm-scale effect of ammonia emissions in the North China Plain. Of all farms, the sow farm was identified as the greatest source of ammonia emission. Regardless of farm scale, ammonia emission rates were observed to be higher in summer. Ammonia concentrations were mostly higher in the large industrial farms partly due to lower ventilation rates than in the small traditional farms.     

Historical nitrogen content of bryophyte tissue as an indicator of increased nitrogen deposition in the Cape Metropolitan Area, South Africa

Information on changes in precipitation chemistry in the rapidly expanding Cape Metropolitan Area (CMA) of South Africa is scarce. To obtain a long-term record of N deposition we investigated changes in moss foliar N, C:N ratios and nitrogen isotope values that might reflect precipitation chemistry. Tissue from 9 species was obtained from herbarium specimens collected between 1875 and 2000 while field samples were collected in 2001/2002. There is a strong trend of increasing foliar N content in all mosses collected over the past century (1.32-1.69 %N). Differences exist between ectohydric mosses which have higher foliar N than the mixohydric group. C:N ratios declined while foliar δ¹⁵N values showed no distinct pattern. From relationships between moss tissue N and N deposition rates we estimated an increase of 6-13 kg N ha⁻¹ a⁻¹ since 1950. Enhanced N deposition rates of this magnitude could lead to biodiversity losses in native ecosystems.     

Canopy leaching of nutrients and metals in a mountain spruce forest

Precipitation and throughfall fluxes of major ions, nutrients (C, N, P), and metals (Al, Fe, Mn), and the chemical composition of litter fall and living plant tissue in Norway spruce stands (the Bohemian Forest; Czech Republic), were used to evaluate how microbial processes and decay of plant tissue in canopies influence canopy leaching (CL) of elements. Proton exchange for Mg²⁺, Ca²⁺, and K⁺ in decaying biomass and co-transport of Ca²⁺ and K⁺ out of plant cells with organic acid anions were the most likely processes contributing to CL of base cations. The CL of total P and N (and also NO₃^?) was minor. Important proportions of the N and P mineral forms were transformed to organic forms by microbial processes (primary and bacterial production), with the respective CL of ?13.9 and 16.4 mmol m^?2 yr^?1 for NH₄⁺ and organic N, and ?0.33 and 0.22 mmol m^?2 yr^?1 for dissolved reactive P (DRP) and organic P. Most of particulate P and N in throughfall (～90%) originated from microbial DRP and NH₄⁺ transformations, but particulate C mostly came from the fragmentation of plant tissue (58%). Among metals, CL was not observed for Al, was small for Fe (0.3 mmol m^?2 yr^?1), and greatest for Mn (0.9 mmol m^?2 yr^?1) due to leaching from decaying tissue by acidic precipitation.     

Day-of-Week Patterns of Particulate Matter and Its Chemical Components at Selected Sites in California

Abstract

This paper analyzes day-of-week variations in concentrations of particulate matter (PM) in California. Because volatile organic compounds (VOCs) and oxides of nitrogen (NO_x) are not only precursors of ozone (O₃) but also of secondary PM, it is useful to know whether the variations by day of week in these precursors are also evident in PM data. Concentrations of PM ≤10 μm (PM₁₀) and ≤2.5[H9262]m in aerodynamic diameter (PM_2.5) were analyzed. PM concentrations exhibit a general weekly pattern, with the maximum occurring late in the workweek and the minimum occurring on weekends (especially Sunday); however, this pattern does not prevail at all sites and areas. PM nitrate (NO₃ ^-) data from Size Selective Inlet (SSI) samplers in the South Coast Air Basin (SoCAB) tend to be somewhat lower on weekends compared with weekdays. During 1988–1991, the weekend average was lower than the weekday average at 8 of 13 locations, with an average decrease of 1%. During 1997–2000, the weekend average was lower than the weekday average at 10 of 13 locations, with an average decrease of 6%. The weekend averages are generally lower than weekday averages for sulfates, organic carbon, and elemental carbon. Because heavy-duty trucks typically represent a major source of elemental carbon, the weekend decrease in heavy-duty truck traffic may also result in a decrease in ambient elemental carbon concentrations.