Pre-combustion CO2 capture from natural gas power plants,with ATR and MDEA processes

Among the various configurations of fossil fuel power plants with carbon capture, this paper focuses on pre-combustion techniques applied to natural gas combined cycles. With more detail, the plant configuration here addressed includes: (i) the steam reforming of natural gas, based on an air-blown autothermal process, following a recuperative pre-reforming treatment, (ii) the water gas shift producing CO₂ and H₂, (iii) the separation of CO₂ by means of a mixed physical–chemical absorption system using a MDEA solution, and (iv) a hydrogen fuelled combined cycle.Similar configurations have been studied quite extensively, being among the most attractive for full-scale realizations in a near-mid term future. This paper proposes a detailed thermodynamic study and optimization of the plant configuration, bringing to a reliable performance estimation based on today's best available technology as far as the various plant sections are concerned (gas and steam turbine, natural gas reforming process, CO₂ separation). The predicted LHV efficiency for the base configuration is about 50%. Being this value at the top of the range quoted in the open literature studies (35–50%), the paper includes a quite extensive sensitivity analysis, showing that more conservative assumptions may bring to significantly poorer performance, especially considering the pretty large number of operating parameters involved in the process.     

Transfer of development rights,growth management,and landscape conservation in Virginia

Urban sprawl in Virginia has led to the loss of wildlife habitat and agricultural land, reduced water quality, and to severe traffic congestion. We conducted a survey to identify the tools being used by the state's localities to manage growth and protect land from development, and the factors that influence interest in particular planning goals and strategies. More specifically, we sought to explore the level of interest in using the transfer of development rights (TDR). Almost every locality in Virginia has stated goals of protecting green space and agricultural land but very few have pursued a TDR programme since it became legal to do so in 2006. However, the main tools being used by planning departments are of limited effectiveness, particularly with regard to ensuring permanent or even long-term land preservation. More broadly, they are reflective of a reactive response to individual development proposals rather than a proactive, comprehensive approach to planning.     

Impact of natural resources,trade openness,and economic growth on CO2 emissions in oil-exporting countries: A panel autoregressive distributed lag analysis

This study explores the impact of natural resource exploitation, trade openness, and economic growth on carbon emissions in a sample of oil-exporting nations for the period 1971–2014. To examine this relationship, we used the panel autoregressive distributed lag model and a set of econometric techniques accounting for cross-sectional dependence. Our results indicate that the exploitation of natural resources and trade openness have a long-term negative impact on environmental quality. Furthermore, our analysis confirms the validity of the Kuznets Environmental Curve for oil-exporting countries. An assessment of causality reveals a bidirectional link between natural resources, economic growth, and CO₂ emissions, as well as a unidirectional link between trade openness and CO₂ emissions. In the light of our findings, appropriate policies could include the imposition of more stringent regulations on the exploitation of natural resources, the application of taxes on carbon emissions, and the promotion of clean and renewable technologies. Greater international cooperation is also needed to address these environmental issues on a global scale.     

Influence of manure application on surface energy and snow cover: model development and sensitivities

Winter landspreading is an important part of manure management in the U.S. Upper Midwest. Although the practice is thought to lead to excessive P runoff losses, surprisingly little has been learned from field experiments or current water quality models. We captured knowledge gained from winter manure landspreading experiments by modifying a mechanistic snow ablation model to include manure. The physically based, modified model simulated the observed delay in snow cover disappearance and surface energy balance changes caused by application of the manure. Additional model simulations of surface energy balance estimates of radiation and turbulent fluxes showed that during intense melting events the manure on top of snow significantly reduced the energy available for melt of the snow underneath, slowing melt. The effect was most pronounced when snowmelt was driven by both relatively high solar radiation and turbulent heat fluxes. High absorbed shortwave radiation caused significant warming of the manure, which led to substantial losses in turbulent fluxes and longwave radiation. Simulations of snowmelt also showed that manure applications between 45 and 100 Mg ha(-1) significantly reduced peak snowmelt rates, in proportion to the manure applied. Lower snowmelt rates beneath manure may allow more infiltration of meltwater compared with bare snow. This infiltration and attenuated snowmelt runoff may partially mitigate the enhanced likelihood of P runoff from unincorporated winter-spread manure.     

Influence of ethnicity on recreation and natural environment use patterns: Managing recreation sites for ethnic and racial diversity

Management of natural environment sites is becoming increasingly complex because of the influx of urbanized society into wildland areas. This worldwide phenomenon impacts a wide range of countries. In southern California ethnicity is often a major factor influencing recreation site use and behavior at sites in the wildland-urban interface. This study investigated the role of ethnicity and race on the use patterns, perception of environment, and recreation behaviors at an outdoor recreation site visited by an ethnically diverse population. Two research questions were asked: (1) What ethnic groups engage in outdoor recreation at this site, and (2) what differences can be assigned to these various groups? Data were collected from 250 recreationists during 1991. Three major ethnic groups were identified, and statistically significant differences were found in the importance of site attributes, activity participation, and in preferred and actual communication channels. Management implications and strategies based on group differences are discussed.     

Survival,reproduction, and recruitment of woody plants after 14 years on a reforested landfill

With the advent of modern sanitary landfill closure techniques, the opportunity exists for transforming municipal landfills into urban woodlands. While costs of fullscale reforestation are generally prohibitive, a modest planting of clusters of trees and shrubs could initiate or accelerate population expansions and natural plant succession from open field to diverse forest. However, among woody species that have been screened for use on landfills, these ecological potentials have not yet been investigated. We examined a 14-yr-old landfill plantation in New Jersey, USA, established to test tolerance of 19 species of trees and shrubs to landfill environments. We measured survivorship, reproduction, and recruitment within and around the experimental installation. Half of the original 190 plants were present, although survival and growth rates varied widely among species. An additional 752 trees and shrubs had colonized the plantation and its perimeter, as well as 2955 stems of vines. However, the great majority (>95%) of woody plants that had colonized were not progeny of the planted cohort, but instead belonged to 18 invading species, mostly native, bird-dispersed, and associated with intermediate stages of secondary plant succession. Based on this evidence, we recommend that several ecological criteria be applied to choices of woody species for the restoration of municipal landfills and similar degraded sites, in order to maximize rapid and economical establishment of diverse, productive woodlands.     

Environmental degradation of the Obra-Renukoot-Singrauli Area,India, and its impact on natural and derived ecosystems

Summary Vast stretches of the Obra—Renukoot—Singrauli region were once covered with natural forests. The tribal dwellings were small and interspersed. However, there has been rapid industrialisation in recent years. Quarrying for limestone, the establishment of a cement factory, thermal power stations and the construction of the G.B. Pant Sagar reservoir have resulted in a rapid build up of human population, the displacement of the original population, deforestation and conversion of natural forest ecosystems into savanna and marginal croplands. The converted ecosystems are under immense biotic stresses such as lopping, grazing, etc.The rainfall is meagre and erratic, the soils are highly weathered and impoverished, consequently the natural forests, as well as the derived ecosystems, are fragile. Signs of desertification are widespread. A rapid depletion in the wildlife has occurred. The establishment of thermal power stations and chemical and cement factories has also resulted in large scale gaseous air pollution, particularly of SO₂ and HF, pollution due to particulate matter through fly ash and cement dust, and that due to liquid effluents. Surface coal mining has caused extensive damage to the natural ecosystems with growing dumps of overburden. The latter needs to be stabilised.This integrated research project on environmental degradation and its impact on air, soil, water and vegetation was divided into five sub-projects, each supervised by a principal investigator. These sub-projects were: (i) Industrial air pollutants and their effects on ecosystem structure and function; (ii) Analysis of structure and functioning of forest ecosystems; (iii) Analysis of structure and functioning of savanna and agroecosystems; (iv) Analysis of structure and functioning of watershed and water-bodies; and (v) Impact of land-use system, socio-economic- demographic conditions, and environmental perception and behavioural management. In these studies dynamics of plant biomass, productivity and nutrients, and biochemical—physiological responses of plants to pollution were emphasised. Environmental perceptions of the native and displaced populations were also studied.The paper outlines a range of recommendations which should help to improve the environmental quality of the region.This article summarises a Man and the Biosphere research project which was sponsored by the Ministry of Environment and Forests of the Government of India. The team of principal investigators comprised Professors J.S. Singh, D.N. Rao, R.S. Ambasht, K.P. Singh, B.S. Gupta and M. Agrawal. The study was coordinated by Professor J.S. Singh, Professor of Botany at Banaras Hindu University.     

A comparative study on cost analysis,efficiency, and process mechanism of effluent treatment plants in Bangladesh

Investigations were conducted into the treatment of effluents produced during manufacturing processes at both a chemicals production facility and a paint manufacturing facility. A comparison of costs of wastewater treatment at both facilities was also performed. The untreated effluents from both facilities were high in biological oxygen demand (BOD), chemical oxygen demand (COD), and total dissolved solids (TDS). In addition, the effluents from the two facilities deviated significantly in dissolved oxygen (DO) content and pH levels. However, both facilities ultimately released treated wastewater with allowable amounts or levels of BOD, COD, TDS, DO, and pH as permitted by the Department of the Environment, Ministry of Environment and Forests, Bangladesh (DOE). The effluent treatment plants (ETP) at both facilities contained combinations of chemical and biological treatment processes. The treatment processes used at the chemicals production facility and at the paint manufacturing facility were continuous and semi‐batch processes, respectively. The biological treatment section of the ETP at the chemicals production facility has both anaerobic and aerobic units, while the paint manufacturing facility has only an aerobic unit. Annual installation and operation costs of the ETP at the chemicals production facility was Bangladeshi Taka (Tk) 1,300,000 ($16,667 US dollars) and Tk 800,000 ($10,257), respectively. The annual installation and operation costs of the ETP at the paint manufacturing facility were Tk 3,050,000 ($39,103) and Tk 6,200,000 ($79,488), respectively.     

The Influence of Road Infrastructure and Traffic on Soil,Water, and Air Quality

Polluting substances are spread as a consequence of the construction and use of roads. This article provides a summary of the substances with which traffic pollutes the environment on a local, regional and global level. The mechanisms of dispersion of pollutants to soil and groundwater are described. Based on environmental quality requirements established in rules and regulations in the Netherlands, the paper discusses mitigating measures necessary to limit the distribution of pollutants along highways. Most of the data in this article come from original research carried out by or by order of the Road and Hydraulic Institute. For comparison, other data from the Netherlands have been included. It is shown that source-oriented measures (volume and technical) will have more effect on environmental quality than measures with regard to treating runoff. The use of porous asphalt instead of nonporous asphalt on highways in the Netherlands has environmental benefits. The article also pays attention to combined use of the roadside verges for treatment of runoff using ecological engineering techniques in the form of natural processes in helophyte filter systems in combination with enhancement of ecological values along highways.     

Technetium: A toxic waste product of the nuclear fuel cycle: Effects on soybean growth and development

Technetium-99 (⁹⁹Tc) is formed in significant amounts (6.2% fission yield) during fission in both nuclear reactors and nuclear bombs. The effects of technetium on soybeans (Glycine max) were studied in relation to (a) cytochemical events in the apical meristems of germinating seedlings; (b) growth responses to 0, 0.04, 0.2, 1.0, 5.0, and 20.0 ppm Tc; (c) growth responses to varying levels of Tc after a prior 5-day germination on Tc-free media, and (d) response to Tc in the presence of added manganese.By 20 days, reductions in growth were evident at all levels of Tc except 0.04 ppm (Experiment 2). Root growth was most severely affected, and seedling abnormality at 20 ppm was fivefold greater than that of the controls. The effect of 20 ppm Tc was evident at 10 days when the accumulated absorption dose was approximately 25 rads. The first evidence of damage at this dose was a delay in the initiation of the first trifoliate leaf. The shoot meristem size was 1.2-fold smaller than that of the control; however, there was no cytological evidence of radiation-induced damage. Observation of mitotic figures did not reveal any chromosome aberrations, micronuclei, or chromosome bridges. The lowest level of Tc showing toxicity was 0.2 ppm which resulted in a 31% reduction in growth at 20 days. The accumulated dose was 0.5 rad (0.025 rad/day) and thus it seems unlikely that the rapid inhibition of growth and development is due to radiological toxicity. It is quite probable that the growth effects are due to chemical toxicity possibly due to nutrient competition and/or substitution in uptake or metabolism. However, extremely low doses of radiation have been shown to delay the onset of DNA synthesis (possibly by membrane effects) inTradescantia and until the actual mechanism of Tc inhibition is determined a radiation effect cannot be totally ruled out.This research was partially supported by ERDA Contract EY-76-S-02-4139     

Influence of different organic amendments on the degradation, metabolism, and adsorption of terbuthylazine

The behavior of the herbicide terbuthylazine (TA) was studied in a clay loam soil after the addition of different organic amendments (OAs). Addition of poultry compost (PC) and urban sewage sludge (USS) retarded degradation of TA with half-life values of 60.3 and 73.7 d, respectively. In contrast, addition of corn straw (CS) did not significantly alter the degradation of TA (half-life 55.5 d) compared with its degradation in nonamended soils (half-life 57.3 d). Sterilization of amended and nonamended soils resulted in a partial inhibition of TA degradation, indicating that biotic and abiotic processes are involved in TA degradation in soil. Degradation of TA led to the formation of desethyl-terbuthylazine, which was detected in low amounts (<8% of the initially applied TA) in all soils. Adsorption of TA was relatively low, with Kd values ranging from 2.31 L kg(-1) in the nonamended soil to 3.93 L kg(-1) in the soil amended with USS. In general, Kd values increased with increasing soil organic carbon content. The dissolved organic matter extracted from the OAs did not appear to interact with the pesticide or the soil surfaces, suggesting that it would not probably facilitate herbicide transport. Desorption studies indicated a slight hysteresis of TA desorption in the amended soils compared with TA desorption in the nonamended soil, which was entirely reversible. These findings might have practical implications for the environmental fate of TA in agricultural soils, where the studied OAs are commonly used.     

Differences in the effects of simulated sea aerosol on water relations, salt content, and leaf ultrastructure of rock-rose plants

White-leaf rock-rose (Cistus albidus L.) and Montpellier rock-rose (C. monspeliensis L.) plants were sprayed 2 to 3 min per day over a 7-d period, in an unheated plastic greenhouse, with different aqueous solutions containing deionized water alone (control); an anionic surfactant (sodium dodecylbenzenesulfonate 82.5%, 50 mg L(-1)) (S1); a solution simulating the composition of sea aerosol (S2); and a solution simulating sea aerosol with anionic surfactant (S3). White-leaf rock-rose was more sensitive to sea aerosol, showing greater leaf damage and markedly decreased growth, and the presence of surfactant enhanced the phytotoxic effect leading to greater increases in mortality. Montpellier rock-rose did not appear to be more adversely affected when surfactant was used in combination with sea aerosol, and manifested slight or less severe symptoms than white-leaf rock-rose. There was a significant increase in leaf turgor potential in the plants treated with both sea aerosol treatments by osmotic adjustment effect. The decrease in photosynthesis level seems to be due to both stomatal and nonstomatal factors. The results of microscopical analysis of Montpellier rock-rose plants show that sea aerosol treatment caused alterations in the chloroplast structure, reducing the starch grain and swelling the thylakoid membranes. The results of this study indicated that Montpellier rock-rose was more tolerant to sea aerosol than white-leaf rock-rose, showing a lower reduction in plant growth and less leaf damage, probably because of its ability to compartmentalize the toxic ions at the intracellular level.     

Influence of nutrient levels on uptake and effects of mercury, cadmium, and lead in water spinach

In Southeast Asia the aquatic macrophyte water spinach (Ipomoea aquatica Forsk.) is a popular vegetable that is cultivated in freshwater courses. These often serve as recipients for domestic and other sorts of wastewater that often contain a variety of pollutants, such as heavy metals. In addition, fertilizers are frequently used where water spinach is cultivated commercially for the food market. To estimate the importance of ambient nutrient concentrations for accumulation of mercury (Hg), cadmium (Cd), and lead (Pb) in water spinach, plants were exposed to nutrient solutions of different strength and with varying metal concentrations. Metal-induced toxic effects, which might possibly affect the yield of the plants, were also studied. The lower the nutrient strength in the medium was, the higher the metal concentrations that accumulated in the different plant parts and the lower the metal concentration in the medium at which metal-induced toxic effects occurred. Accordingly, internal metal concentrations in the plants were correlated to toxic effects. Plants exposed to metals retained a major proportion of the metals in the roots, which had a higher tolerance than shoots for high internal metal concentrations.     

Influence of aeration implements, phosphorus fertilizers, and soil taxa on phosphorus losses from grasslands

Attenuation of rainfall within the solum may help to move contaminants and nutrients into the soil to be better sequestered or utilized by crops. Surface application of phosphorus (P) amendments to grasslands may lead to elevated concentrations of P in surface runoff and eutrophication of surface waters. Aeration of grasslands has been proposed as a treatment to reduce losses of applied P. Here, results from two small-plot aeration studies and two field-scale, paired-watershed studies are supplemented with previously unpublished soil P data and synthesized. The overall objective of these studies was to determine the impact of aeration on soil P, runoff volume, and runoff P losses from mixed tall fescue [Lolium arundinaceum (Schreb.) Darbysh.]-bermudagrass (Cynodon dactylon L.) grasslands fertilized with P. Small-scale rainfall simulations were conducted on two soil taxa using three types of aeration implements: spikes, disks, and cores. The-field scale study was conducted on four soil taxa with slit and knife aeration. Small-plot studies showed that core aeration reduced loads of total P and dissolved reactive P (DRP) in runoff from plots fertilized with broiler litter and that aeration was effective in reducing P export when it increased soil P in the upper 5 cm. In the field-scale study, slit aeration reduced DRP losses by 35% in fields with well-drained soils but not in poorly drained soils. Flow-weighted concentrations of DRP in aerated fields were related to water-soluble P applied in amendments and soil test P in the upper 5 cm. These studies show that the overall effectiveness of mechanical soil aeration on runoff volume and P losses is controlled by the interaction of soil characteristics such as internal drainage and compaction, soil P, type of surface-applied manure, and type of aeration implement.     

The impact of direct and indirect experiences on the development of environmental knowledge, attitudes, and behavior

This study employed a mixed-methods design to examine the relationship between nature experience type (e.g., direct and indirect) and learning outcomes (e.g., environmental knowledge, attitudes, and behavior) associated with an environmental education, international immersion program for adolescents. Longitudinal data from 108 participant and 49 comparison group members were analyzed to test the study’s hypotheses. Additionally, qualitative data were analyzed using grounded theory methodology to assess participants’ perceptions of these processes. The findings indicate that environmental knowledge increased more than environmental attitudes during the indirect portion of the program (i.e., preparatory program) whereas the direct portion (i.e., international workshop) produced similar levels of knowledge and attitude growth. Further, while attitudes were more strongly associated with behavior during the indirect component of the program, the strength of the relationships between attitudes and behavior, and knowledge and behavior were similar during the direct portion of the experience. A synthesis of the findings suggests that the program’s direct experiences catalyzed environmental knowledge into a stronger motivating force than it had been during the indirect experiences. The qualitative findings also provide insights into the characteristics of direct experiences. These findings offer important insights for both theory and practice related to the use of direct and indirect nature experiences to develop environmental knowledge, attitude, and behaviors.     

Monitoring and management of streambank erosion and natural revegetation on the lower Gordon River,Tasmanian Wilderness World Heritage Area,Australia

The wash from high-speed tourist cruise launches causes erosion of the formerly stable banks of the lower Gordon River within the Tasmanian Wilderness World Heritage Area. Speed and access restrictions on the operation of commercial cruise vessels have considerably slowed, but not halted erosion, which continues on the now destabilized banks. To assess the effectiveness of restrictions, bank erosion and natural revegetation are monitored at 48 sites using erosion pins, survey transects, and vegetation quadrats. The subjectively chosen sites are grouped on the basis of geomorphology and bank materials. The mean measured rate of erosion of estuarine banks slowed from 210 to 19 mm/year with the introduction of a 9 knot speed limit. In areas where cruise vessels continue to operate, alluvial banks were eroded at a mean rate of 11 mm/yr during the three-year period of the current management regime. Very similar alluvial banks no longer subject to commercial cruise boat traffic eroded at the slower mean rate of 3 mm/yr. Sandy levee banks have retreated an estimated maximum 10 m during the last 10–15 years. The mean rate of bank retreat slowed from 112 to 13 mm/yr with the exclusion of cruise vessels from the leveed section of the river. Revegetation of the eroded banks is proceeding slowly; however, since the major bank colonizers are very slow growing tree species, it is likely to be decades until revegetation can contribute substantially to bank stability.     

Changing effluent chemistry affect survival,growth and physiological function of <Emphasis Type="Italic">Acacia nilotica</Emphasis> seedlings in northwestern region of India

Recycling and conservation efforts for water are the need of the day because of the lack of new water sources and the ever-increasing demand for drinking water. Seedlings of Acacia nilotica L. were irrigated with: canal water (T₁, control); municipal effluent (T₂); textile effluent (T₃); steel effluent (T₄); textile + municipal effluent in 1:1 ratio (T₅); steel + municipal effluent in 1:2 ratio (T₆); steel + textile in 1:2 ratio (T₈) and steel + municipal + textile in 1:2:2 ratio (T₇) with views to observe effluents effect on the seedlings and its adaptability and to recommend safe disposal of these effluents. Seedlings in T₆, T₇ and T₈ showed 50% lesser height and collar diameter than those in control. Seedlings in T₂ attained greatest height, collar diameter, numbers of branches and produced 140 g dry biomass seedling⁻¹. Highest concentration of manganese (Mn), iron (Fe), copper (Cu) and zinc (Zn) and lowest concentration of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) in the seedlings of T₄, T₆, T₇ and T₈ resulted in nutritional imbalance, mineral toxicity and reduction in photosynthetic (Pn) and transpiration (E) rates and caused seedling mortality. Seedlings of T₃ had highest sodium concentration and low concentration of Ca, Mg and micronutrients resulting in nutritional imbalance, augmented chlorosis and reduced gas exchange and biomass by half as compared to control. Increased growth, Pn and E and biomass in seedlings of T₅ over T₃ and survival period in T₆, T₇ and T₈ seedlings suggested a beneficial effect of effluents mixing. Unscientific disposal should be avoided and toxic concentration of metal ions␣may be reduced for long-term application and harmless disposal of effluents in afforestation and urban development.     

Effect of river sediment on phosphorus chemistry of similarly aged natural and created wetlands in the Atchafalaya Delta, Louisiana, USA

The goal of wetland creation is to produce an artificial wetland that functions as a natural wetland. Studies comparing created wetlands to similarly aged natural wetlands provide important information about creation techniques and their improvement so as to attain that goal. We hypothesized that differences in sediment phosphorus accretion, deposition, and chemistry between created and natural wetlands in the Atchafalaya Delta, Louisiana, USA were a function of creation technique and natural river processes. Sediment deposition was determined with feldspar marker horizons located in created and natural wetlands belonging to three age classes (<3, 5-10, and 15-20 yr old). Phosphorus fractions were measured in these deposited sediments and in suspended and bedload sediment from the Atchafalaya River. Bedload sediment had significantly lower iron- and aluminum-bound, reductant-soluble, and total phosphorus than suspended sediment due to its high sand percentage. This result indicates that wetlands artificially created in the Atchafalaya Delta using bedload sediment will initially differ from natural wetlands of the same age. Even so, similarities between the mudflat stratum of the <1- to 3-yr-old created wetland and the mudflat stratum of the 15- to 20-yr-old natural wetland support the contention that created wetlands in the Atchafalaya Delta can develop natural characteristics through the deposition of river suspended sediment. Differences between three created wetland strata, the 15- to 20-yr-old willow stratum and the <1- to 3-yr-old willow and mixed marsh strata, and their natural counterparts were linked to design elements of the created wetlands that prevented the direct deposition of the river's suspended sediment.     

Influence of Llamas, Horses, and Hikers on Soil Erosion from Established Recreation Trails in Western Montana, USA

/ Various types of recreational traffic impact hiking trails uniquely and cause different levels of trail degradation; however, trail head restrictions are applied similarly across all types of packstock. The purpose of this study was to assess the relative physical impact of hikers, llamas, and horses on recreational trails. Horse, llama, and hiker traffic were applied to 56 separate plots on an existing trail at Lubrecht Experimental Forest in western Montana. The traffic was applied to plots at intensities of 250 and 1000 passes along with a no-traffic control under both prewetted and dry trail conditions. Soil erosion potential was assessed by sediment yield and runoff (using a Meeuwig type rainfall simulator), changes in soil bulk density, and changes in soil surface roughness. Soil moisture, slope, and rainfall intensity were recorded as independent variables in order to evaluate the extent that they were held constant by the experimental design. Horse traffic consistently made more sediment available for erosion from trails than llama, hiker, or no traffic when analyzed across wet and dry trail plots and high and low intensity traffic plots. Although total runoff was not significantly affected by trail user, wet trail traffic caused significantly greater runoff than dry trail traffic. Llama traffic caused a significant increase in sediment yield compared to the control, but caused erosion yields not significantly different than hiker traffic. Trail traffic did not increase soil compaction on wet trails. Traffic applied to dry trail plots generally resulted in a significant decrease in soil bulk density compared to the control. Decreased soil bulk density was negatively correlated with increased sediment yield and appeared to result in increased trail roughness for horse traffic compared to hiker or llama traffic. Differences described here between llama and horse traffic indicate that trail managers may want to consider managing packstock llamas independent of horses.KEY WORDS: Recreational impacts; Sediment yield; Trail degradation