Mean Concentrations Of Ammonia Research Articles

Effects of Water Quality on Spatio-Temporal Diversity of Benthic Macro-Invertebrate Species along the Selected Shores of Lake Victoria, Homa-Bay County, Kenya

Human-induced landscape alterations impact the ecological integrity of water resources by adversely affecting fresh water ecosystems, water-quality, habitat structure, flow regime, and biotic interactions. For instance fresh-water Lake Victoria continues to be affected by massive discharge of waste-waters and other pollutants from the surrounding basin which interfere with the ecological balance leading to adverse impact on benthic macro-invertebrates especially along the lake shores. The objective of this study was to investigate the effect of water quality on the diversity of benthic macro-invertebrates along the shores of Lake Victoria in Homa-Bay County, Kenya. Samples were taken at various beaches including Oluch Kimira River Mouth, Homa Bay Sewage discharge point and Mbita East of course way shoreline and examined for water quality parameters and the species diversity of benthic macro-invertebrates at monthly intervals between September 2019 and Feb 2020. The study was conducted during dry and wet seasons to help determine any changes in waste water discharges, water quality and benthic macro-invertebrates’ characteristics. The results showed significant differences between various sites along the 3 different sites. During both wet and dry periods, Oluch Kimira and Homa Bay recorded low DO levels (4.0±0.46 to 6.2±0.19) MgL-1, while Mbita East of the course way throughout the period recorded DO level of (5.6±0.23 to 7.7±0.17) MgL-1. The mean concentration of Ammonia,NH4(µgL¯¹) during the dry season was (6.32 ±.3.55 to 8.79±3.02) and during the wet season 12.16± 0.92 to 22.50 ± 0.52. The county government should implement the findings of this study, which provides baseline data for evaluating the trends in water quality and related changes in benthic-macro invertebrates biodiversity in Lake Victoria shorelines in Homa Bay County. The findings will also help in making policy decisions in order to support environmental protection in Lake Victoria.

Determination of ammonia and hydrogen sulfide emissions from a commercial dairy farm with an exercise yard and the health-related impact for residents

Airborne emissions from concentrated animal feeding operations (CAFOs) have the potential to pose a risk to human health and the environment. Here, we present an assessment of the emission, dispersion, and health-related impact of ammonia and hydrogen sulfide emitted from a 300-head, full-scale dairy farm with an exercise yard in Beijing, China. By monitoring the referred gas emissions with a dynamic flux chamber for seven consecutive days, we examined their emission rates. An annual hourly emission time series was constructed on the basis of the measured emission rates and a release modification model. The health risk of ammonia and hydrogen sulfide emissions around the dairy farm was then determined using atmospheric dispersion modeling and exposure risk assessment. The body mass-related mean emission factors of ammonia and hydrogen sulfide were 2.13 kg a−1 AU−1 and 24.9 g a−1 AU−1, respectively (one animal unit (AU) is equivalent to 500 kg body mass). A log-normal distribution fitted well to ammonia emission rates. Contour lines of predicted hourly mean concentrations of ammonia and hydrogen sulfide were mainly driven by the meteorological conditions. The concentrations of ammonia and hydrogen sulfide at the fence line were below 10 μg m−3 and 0.04 μg m−3, respectively, and were 2–3 orders of magnitude lower than the current Chinese air quality standards for such pollutants. Moreover, the cumulative non-carcinogenic risks (HI) of ammonia and hydrogen sulfide were 4 orders of magnitudes lower than the acceptable risk levels (HI = 1). Considering a health risk criterion of 1E-4, the maximum distance from the farm fence line to meet this criterion was nearly 1000 m towards north-northeast. The encompassed area of the contour lines of the ambient concentration of ammonia is much larger than that of hydrogen sulfide. However, the contour lines of the ammonia health risk are analogous to those of hydrogen sulfide. In general, the ammonia and hydrogen sulfide emissions from the dairy farm are unlikely to cause any health risks for the population living in the neighborhood.

Distribution of nitrogen and phosphorus and estimation of nutrient fluxes in the water and sediments of Liangzi Lake, China.

Water samples and sediments from Liangzi Lake were taken and used to study the vertical distribution characteristics of nitrogen (N) and phosphorus (P) in both the overlying and pore water. Fluxes of ammonia (NH4+-N) and phosphate (PO43--P) were calculated using a one-dimensional transport-reaction model based on Fick's First Law. The results showed that the mean NH4+-N and NO3--N concentrations in the overlying water of Liangzi Lake were 2.59 and 0.46mgL-1, respectively. The mean PO43--P concentrations were lower than the detection limit. Both N and P displayed peaks at the sediment-water interface. For example, the mean concentration of ammonia in pore water in the surficial layer (0-5cm) was 4.29 ± 2.74mg·L-1, which was twice than that of the overlying water. Two PO43--P vertical profile regimes were identified; one had a gradually increasing trend, while the other first increased and then decreased. The mean orthophosphate concentration in the pore water of the surface layer (0-5cm) was 0.01 ± 0.01mg·L-1. The spatial distribution of ammonia flux values was highly heterogeneous. Using these data, the annual load contribution of autochthonous ammonia was calculated to be 481t a-1. Studying N and P pollution and fluxes in the lakes of urban drinking water sources facilitates the provision of protection measures.

Exposure level and emission characteristics of ammonia and hydrogen sulphide in poultry buildings of South Korea

The purpose of this study is to estimate the concentrations and emission rates of ammonia and hydrogen sulphide released from poultry buildings situated in South Korea by field investigation. Mean concentrations of ammonia and hydrogen sulphide emitted from poultry buildings were 18.8 (±4.90) ppm and 945 (±519) ppb for caged layer house, 15.2 (±3.21) ppm and 603 (±274) ppb for broiler house, and 6.45 (±1.85) ppm and 247 (±184) ppb for layer house with manure belt, respectively. Seasonal variations in concentrations of ammonia and hydrogen sulphide in poultry building were observed highest in winter, lowest in summer (p < 0.01). Based on animal unit (AU), mean emission rates of ammonia and hydrogen sulphide were 4493 (±2095) mg AU−1 h−1 and 4493 (±2095) mg AU−1 h−1, respectively. Those of ammonia and hydrogen sulphide in terms of poultry building area were 278 (±130) mg m−2 h−1 and 12.3 (±9.20) mg m−2 h−1, respectively. Exposure level and emission rate of ammonia and hydrogen sulphide were highest in caged layer house, followed by broiler house and layer house with manure belt (p < 0.05). This finding implicates that the caged layer house among types of poultry building in South Korea should be managed optimally to lessen generation of ammonia and hydrogen sulphide.

가축분뇨 자원화시설에서 발생되는 암모니아와 황화수소의 계절별 현장 평가

본 연구의 목적은 가축분뇨 자원화시설에서 배출되는 주요 악취물질을 대상으로 계절별 현장 방문 조사를 통해 전반적인 악취발생 현황을 파악하고 가축분뇨 자원화시설 운용시 효율적으로 적용될 수 있는 악취 저감대책을 설정하기 위한 기초 데이터 구축이다. 횡형 로터리 (Rotary) 교반방식의 퇴비화시설 내부의 암모니아 발생 농도는 봄철은 84.3 (<TEX>${\pm}15.2$</TEX>) ppm, 여름철은 115.2 (<TEX>${\pm}34.7$</TEX>) ppm, 가을철은 76.2(<TEX>${\pm}18.9$</TEX>) ppm, 겨울철은 38.1 (<TEX>${\pm}10.4$</TEX>) ppm으로 측정되었다. 분석 결과 여름철이 가장 높은 것으로 나타났고, 다음으로 가을철 > 봄철 > 겨울철인 것으로 조사되었다 (p<0.05). 반면 황화수소 발생 농도는 봄철은 7.46(<TEX>${\pm}2.24$</TEX>) ppm, 여름철은 9.42 (<TEX>${\pm}2.82$</TEX>) ppm, 가을철은 8.15 (<TEX>${\pm}3.06$</TEX>) ppm, 겨울철은 10.18 (<TEX>${\pm}4.11$</TEX>) ppm으로 측정되었다. 분석 결과 겨울철이 가장 높은 것으로 나타났고, 다음으로 여름철 > 가을철 > 봄철인 것으로 조사되었으나, 계절별 통계적 차이는 유의하지 않은 것으로 조사되었다 (p>0.05). The objective of this study is to measure the levels of ammonia and hydrogen sulfide in livestock manure composting facility according to seasonal condition. Mean concentrations of ammonia in livestock manure composting facility were 84.3 (<TEX>${\pm}15.2$</TEX>) ppm for spring, 115.2 (<TEX>${\pm}34.7$</TEX>) ppm for summer, 76.2 (<TEX>${\pm}18.9$</TEX>) ppm for autumn, and 38.1 (<TEX>${\pm}10.4$</TEX>) ppm for winter, respectively. Based on the results obtained from this study, the seasonal levels of ammonia in livestock manure composting facility were highest in summer followed by autumn, spring and winterroom (p<0.05). Mean concentrations of hydrogen sulfide in livestock manure composting facility were 7.46 (<TEX>${\pm}2.24$</TEX>) ppm for spring, 9.42 (<TEX>${\pm}2.82$</TEX>) ppm for summer, 8.15 (<TEX>${\pm}3.06$</TEX>) ppm for autumn, and 10.18 (<TEX>${\pm}4.11$</TEX>) ppm for winter, respectively. The livestock manure composting facility showed the highest levels of hydrogen sulfide in winter followed by summer, autumn and spring. However, there was no significant difference of hydrogen sulfide concentration among seasons (p>0.05).

Drinking Water Assessment on Ammonia Exposure Through Tap Water in Kampung Sungai Sekamat, Kajang

The study was intended to analyze ammonia and physicochemical characteristics (pH, temperature, conductivity, total dissolved solid and turbidity) in tap water in Kampung Sungai Sekamat, Kajang. This study was also to estimate the chronic daily intake (CDI) of ammonia exposure through tap water. A total number of 106 water samples were collected in Kampung Sungai Sekamat residents were involved in this study. Tap water analysis results showed that the mean concentration of ammonia was 0.03mg/L ± 0.19mg/L. Ammonia and physicochemical characteristics were below Malaysian Standard Drinking Water Quality (MSDWQ) except for pH and turbidity. A low positive significant correlation was observed between total dissolved solids and ammonia. Mean chronic daily intake (CDI) was 0.0007mg/day/kg ± 0.004mg/day/kg and below than provisional tolerable weekly intake.

Dissolved Nitrogen Survey in Groundwater Resources in Al-Ula village, Madina El Monawara, Saudi Arabia

Nitrogen contents contamination of groundwater is the subject of interest because of their hazard potential to human health. A water quality study was carried out on groundwater wells, which serves as drinking water sources in rural communities, in Al-Ula village of Madina El Monawara region, Kingdom of Saudi Arabia. The ammonia (NH3), nitrate (NO3 -) and nitrite (NO2 -) contents of water samples collected from 10 wells and 3 water sources were estimated using spectrophotometric techniques. Water samples were collected monthly from April 2012 to March 2013 and analyzed for different forms of nitrogen in water samples. Results showed that the mean concentration of ammonia, nitrate, and nitrite ranged from 0.042 to 0.0 mg/l, 2.6 to 0.6 mg/l, and 0.23 to 0.003 mg/l, respectively. The concentrations of nitrogen contents in the water samples were within the permissible limits of the World Health Organization (WHO) drinking water quality guidelines and Saudi Arabia Standards Organization (SASO). Therefore, our conclusion showed that these water resources are safe for human use.

Assessing the Relative Bioavailability of DOC in Regional Groundwater Systems

It has been hypothesized that the degree to which a hyperbolic relationship exists between concentrations of dissolved organic carbon (DOC) and dissolved oxygen (DO) in groundwater may indicate the relative bioavailability of DOC. This hypothesis was examined for 73 different regional aquifers of the United States using 7745 analyses of groundwater compiled by the National Water Assessment (NAWQA) program of the U.S. Geological Survey. The relative reaction quotient (RRQ), a measure of the curvature of DOC concentrations plotted versus DO concentrations and regressed to a decaying hyperbolic equation, was used to assess the relative bioavailability of DOC. For the basalt aquifer of Oahu, Hawaii, RRQ values were low (0.0013 mM(-2)), reflecting a nearly random relationship between DOC and DO concentrations. In contrast, on the island of Maui, treated sewage effluent injected into a portion of the basalt aquifer resulted in pronounced hyperbolic DOC-DO behavior and a higher RRQ (142 mM(-2)). RRQ values for the 73 aquifers correlated positively with mean concentrations of ammonia, dissolved iron, and manganese, and correlated negatively with mean pH. This indicates that greater RRQ values are associated with greater concentrations of the final products of microbial reduction reactions. RRQ values and DOC concentrations were negatively correlated with the thickness of the unsaturated zone (UNST) and depth to the top of the screened interval. Finally, RRQ values were positively correlated with mean annual precipitation (MAP), and the highest observed RRQ values were associated with aquifers receiving MAP rates ranging between 900 and 1300 mm/year. These results are uniformly consistent with the hypothesis that the hyperbolic behavior of DOC-DO plots, as quantified by the RRQ metric, can be an indicator of relative DOC bioavailability in groundwater systems.

The status of atmospheric concentrations of ammonia in an intensive dairy farming area in central Japan

(pp. 53–57) Atmospheric concentrations of ammonia were monitored for one year in an intensive dairy farming area and its environs in the Kanto region in central Japan. Passive samplers were used to collect gaseous ammonia in the atmosphere. A clear difference in concentrations was observed: they were high in the central farming area (3.2–36.2 µg N m−3) and low in its surrounding area (0.2–0.4 µg N m−3). Seasonal changes in concentrations were also witnessed · concentration reached a peak in April and May. A negative correlation was found between the annual mean of ammonia concentrations and the distance from the manure facilities of dairy farmers. Ammonia volatilization from manure was considered to be the primary factor that controlled the atmospheric concentrations of ammonia within 1 km of the manure facilities. The annual mean concentrations of ammonia positively correlated with the nitrogen concentrations in open-bulk precipitation. It was, therefore, suggested that ammonia emissions from dairy farming affected the wet deposition of nitrogen. On the other hand, both seasonal changes in precipitation and manure management performed by dairy farmers were considered to be the primary factors that induced seasonal changes in atmospheric ammonia concentrations.

축분 퇴비화시스템 운용방식에 따른 실내 대기오염 평가

본 연구는 환기 방식 및 교반 유무에 따른 축분 퇴비화 시스템 내 대기 및 작업 환경을 평가하기 위해 수행되었다. 측정대상 가스상 물질인 암모니아, 황화수소, 악취농도의 경우 자연환기-미교반시 2.45ppm, 19.96ppb, 15.8, 강제환기-미교반시 7.61ppmm 31.36ppb, 30.2, 자연환기-교반시5.50ppm, 14.69ppb, 46.4, 강제교화기- 교반시 30.12ppm, 39.91ppb, 205.5가 평균적으로 발생되는 것으로 분석되었다. 각 운용조건에 따른 흡입성 분진과 호흡성 분진의 평균 농도는 자연환기-미교반시 368.6<TEX>${\mu}g$</TEX>/<TEX>$m^3$</TEX>,96.0<TEX>${\mu}g$</TEX>/<TEX>$m^3$</TEX>, 강제화기-미교반시 283.9<TEX>${\mu}g$</TEX>/<TEX>$m^3$</TEX>, 119.5<TEX>${\mu}g$</TEX>/<TEX>$m^3$</TEX>, 자연환기-교반시 208.7<TEX>${\mu}g$</TEX>/<TEX>$m^3$</TEX>, 139.8<TEX>${\mu}g$</TEX>/<TEX>$m^3$</TEX>, 강제환기-교반시 209.2<TEX>${\mu}g$</TEX>/<TEX>$m^3$</TEX>, 131.7<TEX>${\mu}g$</TEX>/<TEX>$m^3$</TEX>인 것으로 조사되었다. 총 부유 박테리아와 곰팡이의 경우 자연환기-미교반시 28,673cfu/<TEX>$m^3$</TEX>, 22,507cfu/<TEX>$m^3$</TEX>, 강제환기-미교반시 7,462cfu/<TEX>$m^3$</TEX>,3,229cfu/<TEX>$m^3$</TEX>, 자연환기-교반시 19,592cfu/<TEX>$m^3$</TEX>, 26,376.29cfu/<TEX>$m^3$</TEX>, 강제환기-교반시 18,645cfu/<TEX>$m^3$</TEX>, 24,581cfu/<TEX>$m^3$</TEX>가 평균적으로 발생되는 것으로 분석되었다. 대체로 가스상 물질은 자연환기와 교반을 하지 않는 경우보다 강제환기와 교반을 하는 경우에 더 많이 발생되는 경향을 보였다. 또한 흡입성 분진과 총 부유박테리아의 경우, 자연환기-미교반시에 대체로 더 높게 발생된 반면, 호흡성 분진과 총 부유곰팡이의 경우 강제환기-교반시에 더 많이 발생되는 경향을 보였다. 내부 온도와 상대습도는 입자상 물질과 생물학상 오염물질 발생에 영향을 주는 것으로 분석되었고, 암모니아와 황화수소는 축분 퇴비화시 발생되는 악취 원인물질로 입증되었다. 물리적 요인인 온도와 상대습도는 축분 퇴비화 시스템내에서 주로 입자상 오염물질과 생물학상 오염물질의 발생량에 영향을 미치는 주요인자로 입증되었는데, 시스템 내부 온도와 상대습도가 높으면 이것들의 농도도 높아지는 것으로 분석되었다. Air quality in the livestock waste compost pilot plant at the Colligate Livestock Station was assessed to quantity the emissions of aerial contaminants and evaluate the degree of correlation between them for different operation strategies; with the ventilation types and agitation of compost pile, in this study. The parameters analyzed to reflect the level of air quality in the livestock waste compost pilot plant were the gaseous contaminants; ammonia, hydrogen sulfide, and odor concentration, the particulate contaminants; inhalable dust and respirable dust, and the biological contaminants; total airborne bacteria and fungi. The mean concentrations of ammonia, hydrogen sulfide, and odor concentration in the compost pilot plant without agitation were 2.45ppm, 19.96ppb, and 15.8 when it was naturally ventilated, and 7.61ppm, 31.36ppb, and 30.2 when mechanically ventilated. Those with agitation were 5.50ppm, 14.69ppb, and 46.4 when naturally ventilated, and 30.12ppm, 39.91ppb, and 205.5 when mechanically ventilated. The mean concentrations of inhalable and respirable dust in the compost pilot plant without agitation were 368.6<TEX>${\mu}g$</TEX>/<TEX>$m^3$</TEX> and 96.0<TEX>${\mu}g$</TEX>/<TEX>$m^3$</TEX> with natural ventilation, and 283.9<TEX>${\mu}g$</TEX>/<TEX>$m^3$</TEX> and 119.5<TEX>${\mu}g$</TEX>/<TEX>$m^3$</TEX> with mechanical ventilation. They were also observed with agitation to 208.7<TEX>${\mu}g$</TEX>/<TEX>$m^3$</TEX> and 139.8<TEX>${\mu}g$</TEX>/<TEX>$m^3$</TEX> with natural ventilation, and 209.2<TEX>${\mu}g$</TEX>/<TEX>$m^3$</TEX> and 131.7<TEX>${\mu}g$</TEX>/<TEX>$m^3$</TEX> with mechanical ventilation. Averaged concentrations of total airborne bacteria and fungi in the compost pilot plant without agitation were observed to 28,673cfu/<TEX>$m^3$</TEX> and 22,507cfu/<TEX>$m^3$</TEX> with natural ventilation, and 7,462cfu/<TEX>$m^3$</TEX> and 3,228cfu/<TEX>$m^3$</TEX> with mechanical ventilation. They were also observed with agitation to 19,592cfu/<TEX>$m^3$</TEX> and 26,376cfu/<TEX>$m^3$</TEX> with the natural ventilation, and 18,645cfu/<TEX>$m^3$</TEX> and 24,581cfu/<TEX>$m^3$</TEX> with the mechanical ventilation. It showed that the emission rates of gaseous pollutants, such as ammonia, hydrogen sulfide, and odor concentration, in the compost pilot plant operated with the mechanical ventilation and with the agitation of compost pile were higher than those with the natural ventilation and without the agitation. While the concentrations of inhalable dust and total airborne bacteria in the compost pilot plant with the natural ventilation and with the agitation, the concentrations of respirable dust and total airborne fungi in the compost pilot plant with the mechanical ventilation and agitation were higher than those with the natural ventilation and without the agitation of compost pile. It was statistically proved that indoor temperature and relative humidity affected the release of particulates and biological pollutants, and ammonia and hydrogen sulfide were believed primary malodorous compounds emitted from the compost pilot plant.

Farmers’ exposure to dusts and gases in modern Finnish cubicle cow houses

The occurrence of airborne dust, gases, microbes, endotoxin and bovine epithelial antigens (BEA, BDA20) was studied in 26 modern, mainly cubicle, cow houses. Air samples of total dust, total spores, endotoxin and bovine epithelial allergens were collected on membrane filters with portable or piston pumps and analyzed with appropriate methods. Concentrations of gases (ammonia, carbon dioxide, hydrogen sulfide) were measured with diffusion tubes. Airborne viable spores were collected with a cascade impactor on five selective culture media for the identification of xerophilic, mesophilic and thermotolerant fungi and thermophilic actinomycetes. The geometric mean concentrations of total dust, BEA and BDA20 were 0.2-1.9 mg/m3, 5.2-9.7 μg/m3 and 50-260 ng/m3, respectively. The mean concentrations of ammonia and carbon dioxide were between 2.8-15 ppm and 2200-3200 ppm, respectively. The geometric mean of endotoxins was 19 ng/m3 and the concentrations of fungi were at the 101-103 cfu/m3 level. In general, the variation in concentrations of total dust, viable fungi and endotoxin was large. The concentrations of total dust and fungi were lower than in earlier studies. Thus new cubicle houses provide a better working environment with regard to airborne hazards than the traditional cow houses.

EFFECT OF VENTILATION ON AMMONIA LEVELS IN COWHOUSES

The effect of ventilation on concentrations of ammonia in typical Finnish cowhouses was investigated. Temperature, relative humidity, and concentration of carbon dioxide also were measured. The measurements were made in autumn and winter at six farms, each with a cowhouse accommodating approximately 20 milk cows. A tracer-gas technique and multipoint equipment measured ventilation. Samples for airborne ammonia were collected in impinger flasks and analyzed by a gas-specific electrode. Ammonia was also measured at the same sites by diffusion tubes. The mean rate of ventilation varied from 2.2 to 6.5 room changes per hour and the mean concentration of ammonia from 4.2 to 15.4 ppm. The correlation between ventilation rates and concentrations of ammonia was poor, indicating that ammonia concentrations are also affected by other factors. In all except one cowhouse the ventilation rates were within established limits. The lowest concentrations of airborne ammonia were found in cowhouses equipped with a low exha...

Supplementation of grass hay with molasses in crossbred ( Bos taurus × Bos indicus) non-lactating cows: effect of timing of molasses supplements on feed intake, digestion, DM degradation and rumen fermentation

An experiment was carried out to evaluate the effects of timing of molasses supplementation on feed intake, diet digestibility, degradation of hay dry matter (DM), rumen pool size of total ingesta and neutral detergent fibre, and rumen fermentation. Four ruminally fistulated Friesian ( Bos taurus) × Boran ( Bos indicus) crossbred non-lactating cows, in a balanced 4 × 4 Latin square experiment, were given a basal diet (Diet C) of grass hay ad libitum and 2.0 kg DM of noug ( Guizotia abyssinica) cake per day. The other three diets were supplemented with 2.0 kg DM day −1 of sugar-cane molasses given at the same time as a meal of the basal diet (Diet M0), or 1 h after (Diet M1) or 2 h after (Diet M2) a meal of the basal diet. The DM intake of hay was highest (8 vs. 7 kg) when molasses was given at the same time as the basal diet. The effect of molasses on total DM intake was additive, so that the intake of total DM increased ( P < 0.001) the molasses supplement. The apparent digestibility of DM was increased from 0.57 to 0.61 by including molasses in the diets ( P < 0.01). The molasses diets had no significant effect ( P > 0.05) on the degradation parameters of DM of grass hay. Molasses supplements decreased ( P < 0.001) the mean concentration of ammonia from 14.6 to 9.9 mmol l −1. The molar proportion of acetate was lower in molasses-containing diets (714 vs. 659 mmol mol l −1, P < 0.001), and those of propionate (171 vs. 206 mmol mol l −1, P < 0.001) and butyrate (94 vs. 117 mmol mol l −1, P < 0.01) were higher.

Long-term effects of treated domestic wastewater on brown trout

A 12-month bioassay was conducted to determine the effects of unchlorinated, treated, domestic wastewater on survival, growth, swimming performance, and gill tissue of brown trout ( Salmo trutta). Ammonia was the toxicant of concern, because the facility's effluent periodically exceeded the U.S. Environmental Protection Agency's (EPA) recommended criterion. Juvenile brown trout (initial weight = 2 g), which were exposed to six concentrations (0–37%) of effluent, were fed a restricted ration, so that growth rates were similar to those of wild stream residents. At the highest effluent concentration, monthly mean concentrations of un-ionized ammonia ranged from 0.004 to 0.055 mg l −1 NH 3N (at. wt = 14); these concentrations exceeded the EPA criterion of 0.016 mg l −1 about 40% of the time. There were no significant effects of effluent concentration on survival, growth, or swimming performance of brown trout, but the degree of damage to gills was directly related to effluent concentration.

A relationship between the molar proportion of propionic acid and the clearance rate of the liquid phase in the rumen of the sheep

1. Four rumen-cannulated sheep were given a forage mixture (F) of chopped hay-ground, pelleted, dried grass (92:8, w/w) and two concentrate mixtures (C and S) of ground barley-ground hay-flaked maize (46:24:30 and 56:24:20, by wt respectively) in twenty-four hourly meals each day. Each of the diets was offered in successive periods of 16 d to give a feeding sequence F-S-C-S for one pair of sheep and C-S-F-S for the other pair. 2. The average composition (mol/100 mol) of the mixture of short-chain fatty acids, acetic, propionic and butyric, in the rumen was respectively 70-1, 18-5 and 7-5 with diet F, and 55-8, 24-8 and 13-6 with diet C. With diet S, the pattern of fermentation varied both between animals and in the same animal for different periods having either 'high' (28-39 mol/100 mol) or 'low' (16-21 mol/100 mol) proportions of propionic acid. On average when diet S followed diet F there was less propionic acid in the fermentation mixture than when diet S followed diet C (59-3 acetic, 22-2 propionic and 14-1 butyric as compared with 52-7, 29-4 and 13-1 respectively) but this trend was not significant and there was evidence of interactions between the feeding sequences and the individual sheep. 3. The mean concentrations of ammonia, sodium, potassium and chloride were similar for all diets but the pH and concentrations of calcium, magnesium and phosphorus tended to be higher and the buffering capacity lower for diet F than for diets C or S. In animals receiving diet S there was no relationship between the concentrations of minerals, the pH or buffering capacity and the pattern of fermentation except for ammonia, the concentration of which was high when the molar proportion of propionic acid was low. 4. Rumen volume, outflow rate and clearance rate, determined using polyethylene glycol, were higher for diet F than for diets C and S but within each diet, particularly for diet S, values varied considerably between sheep and between periods. 5. There was evidence of an interrelationship between the molar proportion of propionic acid in the fermentation products and the clearance rate, which indicated that the clearance rate may be an important factor influencing the pattern of fermentation in the rumen.