Effects of pasture renovation on hydrology, nutrient runoff, and forage yield

Proper pasture management is important in promoting optimal forage growth and reducing runoff and nutrient loss. Pasture renovation is a management tool that improves aeration by mechanically creating holes or pockets within the soil. Pasture renovation was performed before manure application (poultry litter or swine slurry) on different pasture soils and rainfall simulations were conducted to identify the effects of pasture renovation on nutrient runoff and forage growth. Renovation of small plots resulted in significant and beneficial hydrological changes. During the first rainfall simulation, runoff volumes were 45 to 74% lower for seven out of eight renovated treatments, and infiltration rates increased by 3 to 87% for all renovated treatments as compared with nonrenovated treatments. Renovation of pasture soils fertilized with poultry litter led to significant reductions in dissolved reactive P (DRP) (74-87%), total P (TP) (76-85%), and total nitrogen (TN) (72-80%) loads in two of the three soils studied during the first rainfall simulation. Renovation did not result in any significant differences in forage yields. Overall, beneficial impacts of renovation lasted up to 3 mo, the most critical period for nutrient runoff following manure application. Therefore, renovation could be an important best management practice in these areas.     

美国西雅图地区城市边缘湖泊的富营养化

引言 近50年来美国住宅开发大量增加.所增住宅很多集中在市区,美国几乎80%的人口现今居住在城里[1].当人们从农村地区和市中心向城市边缘和郊区迁移时,城市变得越来越大,人口增加、地区扩大[1].在城市扩建时,开发商把农业用地和林区的土地转变成城市和城郊[2,3].于是,在城市的边缘、在城乡结合部常常夹杂着被建筑工地、新开发的住宅和商业网点所分割的小块农田和林地以及现在被城市扩建所吞噬的过去十分偏僻的住宅[1,2].     

Isotope tracing of submarine groundwater discharge offshore Ubatuba, Brazil: results of the IAEA-UNESCO SGD project

Results of groundwater and seawater analyses for radioactive ((3)H, (222)Rn, (223)Ra, (224)Ra, (226)Ra, and (228)Ra) and stable (D and (18)O) isotopes are presented together with in situ spatial mapping and time series (222)Rn measurements in seawater, direct seepage measurements using manual and automated seepage meters, pore water investigations using different tracers and piezometric techniques, and geoelectric surveys probing the coast. This study represents first time that such a new complex arsenal of radioactive and non-radioactive tracer techniques and geophysical methods have been used for simultaneous submarine groundwater discharge (SGD) investigations. Large fluctuations of SGD fluxes were observed at sites situated only a few meters apart (from 0cmd(-1) to 360cmd(-1); the unit represents cm(3)/cm(2)/day), as well as during a few hours (from 0cmd(-1) to 110cmd(-1)), strongly depending on the tidal fluctuations. The average SGD flux estimated from continuous (222)Rn measurements is 17+/-10cmd(-1). Integrated coastal SGD flux estimated for the Ubatuba coast using radium isotopes is about 7x10(3)m(3)d(-1) per km of the coast. The isotopic composition (deltaD and delta(18)O) of submarine waters was characterised by significant variability and heavy isotope enrichment, indicating that the contribution of groundwater in submarine waters varied from a small percentage to 20%. However, this contribution with increasing offshore distance became negligible. Automated seepage meters and time series measurements of (222)Rn activity concentration showed a negative correlation between the SGD rates and tidal stage. This is likely caused by sea level changes as tidal effects induce variations of hydraulic gradients. The geoelectric probing and piezometric measurements contributed to better understanding of the spatial distribution of different water masses present along the coast. The radium isotope data showed scattered distributions with offshore distance, which imply that seawater in a complex coast with many small bays and islands was influenced by local currents and groundwater/seawater mixing. This has also been confirmed by a relatively short residence time of 1-2 weeks for water within 25km offshore, as obtained by short-lived radium isotopes. The irregular distribution of SGD seen at Ubatuba is a characteristic of fractured rock aquifers, fed by coastal groundwater and recirculated seawater with small admixtures of groundwater, which is of potential environmental concern and has implications on the management of freshwater resources in the region.     

The Smogless Automobile

Demands for high performance and reliability of electrostatic precipitators for collection of fly ash from low sulfur fuels has led to rapid escalation of sizes and uncertainties in sizings of cold-side precipitators. This has led to utilization of the so-called “hot-side” precipitator. The underlying concept of hot-side precipitation is the avoidance of the necessity to operate the precipitator under high resistivity conditions. Data on in-situ measurements of resistivity of low sulfur fuel ash, as well as performance parameters of a number of operating installations, will be reviewed. These data will demonstrate the reduced sensitivity of hot-side precipitator sizing to fuel conditions. Other advantages of hot-side precipitators will be discussed.

Operating experience with hot-side precipitators has focused on structural problems which are peculiar to the larger, higher temperature installations. The nature and solution of these problems will be discussed. General comparative economics of hot-side and cold-side precipitators as they relate to fuel properties will be reviewed.     

Reducing ammonia emissions and volatile fatty acids in poultry litter with liquid aluminum chloride

This study was a pen trial in which the effects of adding different rates of liquid aluminum chloride (AlCl₃) on litter pH, total volatile fatty acids (VFAs), and ammonia (NH₃) fluxes was evaluated. Liquid AlCl₃ treatments used in this study were sprayed on the rice hull surface at rates of 100 g, 200 g, and 300 g liquid AlCl₃/kg rice hulls; untreated rice hulls served as controls. Litter pH, total VFAs, and NH₃ fluxes were all lowered (P< 0.05) by all of the liquid AlCl₃ treatments compared with controls during certain times of the 5 week study. However, there were no significant differences among treatments on litter pH at the end of the study (from 3 to 5 weeks) or NH₃ fluxes at beginning of the study (0 to 3 weeks). Total VFAs were reduced 16 %, 29 %, and 53 % by 100 g liquid AlCl₃/kg rice hulls, 200 g liquid AlCl₃/kg rice hulls, and 300 g liquid AlCl₃/kg rice hulls, respectively. Liquid AlCl₃additions reduced NH₃ fluxes by 35 %, 57 % and 67 %, respectively, at the low, medium and high rates. In summary, these results indicate that adding liquid aluminum chloride to rice hulls would be a useful tool in reducing the negative environmental impact of poultry litter. It should be noted that the decreased VFA production and NH₃ volatilization was chiefly associated with reduction in litter pH.     

Defining Indicators and Standards for Tourism Impacts in Protected Areas: Cape Range National Park,Australia

Visitors’ perceptions of impacts and acceptable standards for environmental conditions can provide essential information for the sustainable management of tourist destinations, especially protected areas. To this end, visitor surveys were administered during the peak visitor season in Cape Range National Park, on the northwest coast of Western Australia and adjacent to the iconic Ningaloo Reef. The central focus was visitors’ perceptions regarding environmental conditions and standards for potential indicators. Conditions considered of greatest importance in determining visitors’ quality of experience included litter, inadequate disposal of human waste, presence of wildlife, levels of noise, and access to beach and ocean. Standards were determined, based on visitors’ perceptions, for a range of site-specific and non-site-specific indicators, with standards for facilities (e.g., acceptable number of parking bays, signs) and for negative environmental impacts (e.g., levels of littering, erosion) sought. The proposed standards varied significantly between sites for the facilities indicators; however, there was no significant difference between sites for environmental impacts. For the facilities, the standards proposed by visitors were closely related to the existing situation, suggesting that they were satisfied with the status quo. These results are considered in the context of current research interest in the efficacy of visitor-derived standards as a basis for protected area management.     

Progressive nitrogen limitation of ecosystem processes under elevated CO2 in a warm-temperate forest

A hypothesis for progressive nitrogen limitation (PNL) proposes that net primary production (NPP) will decline through time in ecosystems subjected to a step-function increase in atmospheric CO2. The primary mechanism driving this response is a rapid rate of N immobilization by plants and microbes under elevated CO2 that depletes soils of N, causing slower rates of N mineralization. Under this hypothesis, there is little long-term stimulation of NPP by elevated CO2 in the absence of exogenous inputs of N. We tested this hypothesis using data on the pools and fluxes of C and N in tree biomass, microbes, and soils from 1997 through 2002 collected at the Duke Forest free-air CO2 enrichment (FACE) experiment. Elevated CO2 stimulated NPP by 18-24% during the first six years of this experiment. Consistent with the hypothesis for PNL, significantly more N was immobilized in tree biomass and in the O horizon under elevated CO2. In contrast to the PNL hypothesis, microbial-N immobilization did not increase under elevated CO2, and although the rate of net N mineralization declined through time, the decline was not significantly more rapid under elevated CO2. Ecosystem C-to-N ratios widened more rapidly under elevated CO2 than ambient CO2 indicating a more rapid rate of C fixation per unit of N, a processes that could delay PNL in this ecosystem. Mass balance calculations demonstrated a large accrual of ecosystem N capital. Is PNL occurring in this ecosystem and will NPP decline to levels under ambient CO2? The answer depends on the relative strength of tree biomass and O-horizon N immobilization vs. widening C-to-N ratios and ecosystem-N accrual as processes that drive and delay PNL, respectively. Only direct observations through time will definitively answer this question.     

Carcinogenicity of diesel exhaust as tested in strain a mice

Groups of strain A mice were exposed to diesel exhaust by inhalation and diesel particulate by intraperitoneal injection. The animals were exposed from seven to eight weeks and then sacrificed 26–30 weeks postexposure. Other animals were exposed for up to seven months by the inhalation route. Some animals were promoted using urethane at a dose below which tumors would occur. There was no increase in incidence of pulmonary adenomas in the animals exposed to either diesel exhaust or diesel particulate over the control animals. In the animals which were promoted using urethane at a low dose, there was a significant increase in pulmonary adenomas. Diesel particulate was found in the lungs and bronchial lymph nodes of animals exposed to diesel exhaust 26–30 weeks after cessation of exposure.     

FECAL COLIFORM AND STREPTOCOCCUS CONCENTRATIONS IN RUNOFF FROM GRAZED PASTURES IN NORTHWEST ARKANSAS1

ABSTRACT: Agricultural practices such as cattle grazing and animal manure application can contribute to relatively high runoff concentrations of fecal coliform (FC) and fecal streptococcus (FS). Available information, however, is inconsistent with respect to the effects of such practices as well as to measures that can discriminate among candidate sources of FC and FS. The objective of this study was to assess the effects of grazing, time of year, and runoff amounts on FC and FS concentrations and to evaluate whether FCIFS concentration ratios are consistent with earlier values reported as characteristic of animal sources. Runoff from four Northwest Arkansas fields was sampled and analyzed for fecal coliform (FC) and fecal streptococcus (FS) for nearly three years (1991–1994). Each field was grazed and fertilized, with two fields receiving inorganic fertilizer and two receiving animal manure. Runoff amount had no effect on runoff concentrations of FC or FS. There were no consistent relationships between the presence of cattle and FC and FS runoff concentrations. Both FC and FS concentrations were affected by the season during which the runoff occurred. Higher concentrations were observed during warmer months. Runoff FC concentrations exceeded the primary contact standard of 200 cfu/100 mL during at least 89 percent of all runoff events and the secondary contact standard of 1000 cfu/100 mL during at least 70 percent of the events. Ratios of FC to FS concentrations varied widely (from near zero to more than 100), confirming earlier findings that FC/FS ratios are not a reliable indicator of the source of FC and FS.     

Mitigation of chlorpyrifos runoff using constructed wetlands

Constructed wetlands have been proposed as a potential best management practice (BMP) to mitigate effects of pesticide-associated agricultural runoff. Wetland mesocosms (14 m x 59-73 m) were amended with chlorpyrifos to simulate a storm runoff event at concentrations of 73, 147 and 733 microg/l. Water, sediment and plant samples collected weekly for 12 weeks indicated that chlorpyrifos rapidly sorbed to sediment and plant material, with approximately 47-65% of measured chlorpyrifos mass retained within the first 30-36 m of wetland mesocosms. Of the measured mass, approximately 55% and 25% were retained by sediments and plants, respectively. A field-scale evaluation of a constructed wetland's mitigation capability was performed in the Lourens River watershed of Cape Town, South Africa. Results indicate that the wetland was able to retain and considerably decrease the concentration (and hence toxicity) of chlorpyrifos and suspended sediment entering the receiving waterbody (Lourens River). This research provides fundamental answers concerning constructed wetland capabilities that are necessary for constructing field-scale systems within agricultural watersheds.