Surface ozone concentrations and exposures during growing season at the Lithuanian rural site

The surface ozone (O₃) data show an increase by 2.6 % per year during the period 1982–1994 at the rural site of Lithuania. WHO (World Health Organization), UN-ECE (United Nations Economic Commission for Europe), CES (Commission of the European Communities) guideline values for the protection of vegetation from adverse effects are exceeded during the growing season at the Preila coastal station. Ozone exposures for different concentration threshold are estimated during daylight hours in April-September. These values above 60 g/m³ varied between 10 000 and 43 000 (g/m³) ·h, above 80 g/m³ — between 1700 and 15 000 (g/m³) ·h, above 100 g/m³ — between 130 and 3700 (g/m³) ·h during separate years. Maximum hourly ozone values were observed from 116 to 228 g/m³ during this period.     

Bioaccumulation of selenium by floating aquatic plants

The degree to which floating aquatic plants concentrate Se in tissues was determined for four species grown in solutions containing various levels of Se. Results of this greenhouse study showed that all four plant species, Azolla caroliniana, Eichhornia crassipes, Salvinia rotundi folia, and Lemna minor absorbed Se quickly upon exposure to Se in water as concentrated as 2.5 g Se mL^–1, and attained maximum tissue concentrations within 1 to 2 weeks. Azolla absorbed Se to the highest tissue concentration (about 1000 g Se g^–1 dry matter) from the 2.5 g Se mL^–1 solution, followed by Salvinia (700 g Se g^–1), Lemna (500 g Se g^–1),and Eichhornia (300 g Se g^–1). Plant growth appeared unaffected by solution Se concentrations lower than about 1.25 g mL^–1. These results indicate potential for rapid Se movement from water into aquatic food chains, and for use of aquatic plants for Se removal in wastewater treatment systems.     

Acidic deposition,ecosystem processes,and nitrogen saturation in a high elevation Southern Appalachian watershed

High-elevation red spruce-Fraser fir forests in the Southern Appalachian mountains: 1) receive among the highest rates of atmospheric deposition measured in North America, 2) contain old-growth forests, 3) have shown declines in forest health, 4) have sustained high insect-caused fir mortality, and 5) contain poorly buffered soils and stream systems. High rates of nitrogen and sulphur deposition (1900 and 2200 Eq·ha^–1·yr^–1, respectively) are dominated by dry and cloud deposition processes. Large leaching fluxes of nitrate-nitrogen (100–1400 Eq·ha^–1·yr^–1) occur within the soil profile. We have expanded the study to the watershed scale with monitoring of: precipitation, throughfall, stream hydrology, and stream chemistry. Two streamlets drain the 17.4 ha Noland Divide Watershed (1676–1920m) located in the Great Smoky Mountains National Park. A network of 50 20x20 m plots is being used to assess stand structure, biomass, and soil nutrient pools. Nitrate is the predominant anion in the streamlets (weighted concentrations: 47 and 54 eq·L^–1 NO₃ ^–; 31 and 43 eq·L^–1 SO₄ ^2–). Watershed nitrate export is extremely high (1000 Eq·ha^–1 yr^–1), facilitating significant base cation exports. Stream acid neutralizing capacity values are extremely low (–10 to 20 eq·L^–1) and episodic acidifications (pH declines of a full unit in days or weeks time) occur. Annual streamwater sulfate export is on the order of 770 Eq·ha^–1yr^–1 or about one-third of total annual inputs, indicating there is net watershed sulfate retention. The system is highly nitrogen saturated (Stage 2, Stoddard, 1994) and this condition promotes both chronic and episodic stream acidification.     

The “shenandoah national park: Fish in sensitive habitats” (SNP: FISH) project. An integrated assessment of fish community responses to stream acidification

The Shenandoah National Park: Fish in Sensitive Habitats (SNP:FISH) project is a response to declining pH and acid neutralizing capacity in Shenandoah National Park (SNP) streams. SNP receives more atmospheric sulfate than any other USA national park, and pH had decreased to the point where early negative effects on fish were expected. SNP provides the opportunity to study the early stages of acidification effects on fish. Three different classes of geological formations yield streams with low-ANC (0 Eq/L), intermediate-ANC (60–100 Eq/L) or high-ANC (150–200 Eq/L) waters in SNP. This allows a comparison of responses across a water quality gradient in a small geographic area receiving similar deposition. Both chronic and episodic acidification occur in SNP streams. Biological effects are apparent in fish species richness, population density, condition factor, age, size, and bioassay survival. A primary project objective was to provide the necessary data for development and testing models for forecasting changes in fish communities resulting from changes in stream chemistry. Monitored variables include several which are predictive of acidification effects on SNP fish communities.     

Molybdenum reserves of seed,and growth and N2 fixation by Phaseolus vulgaris L.

Summary Plants grown from seed with high (1.5–7.3 g Mo seed^-1) and low (0.07–1.4 g Mo seed^-1) Mo contents were grown in the presence and absence of Mo in growth media (perlite) or in a flowing-solution culture, in a controlled environment. Neither the high (1.5 g Mo seed^-1) nor the low (0.1 g Mo seed^-1) Mo content in seed from a small-seeded genotype (BAT 1297) was able to prevent Mo deficiency (reduced shoot, root and nodule dry weight, N₂ fixation and seed production) in growth media without an external supply of Mo, whereas both the high (7.3 g Mo seed^-1) and the low (0.07 g Mo seed^-1) contents in seed were able to prevent Mo deficiency in a large-seeded genotype (Canadian Wonder). Responses to Mo treatment by the Two genotypes were inconsistent between the growth media and solution culture experiments. Seed with a large Mo content (3.5 g Mo seed^-1) from the Canadian Wonder genotype was unable to prevent Mo deficiency (reduced shoot and nodule dry weight and N₂-fixation) in a solution culture without an external source of Mo, whereas both the large (1.7 g Mo seed^-1) and the small (0.13 g Mo seed^-1) contents in seed prevented a deficiency in BAT 1297. Growing plants from seed with a small Mo content, without additional Mo, reduced the seed Mo content by 83–85% and seed production by up to 38% in both genotypes. Changes in seed size and increases in shoot, root and nodule dry weight occurred, but varied with the genotype and growth conditions. These effects were also observed in some cases where plants were grown with additional Mo, demonstrating that the amount of Mo in the seed sown can influence plant nutrition irrespective of the external Mo supply. Nodule dry weight, total N content of shoots and seed production were improved by using seed with a small Mo content (1.64–3.57 g Mo seed^-1) on acid tropical soils in Northern Zambia. Plants of both the large- and small-seeded genotypes grown from seed with a small Mo content (<1.41 g Mo seed^-1) had a smaller nodule weight, accumulated less N and produced less seed. The viability of seed with a small Mo content was lower (germination up to 50% less) than that of seed with a large Mo content.     

Ionic composition of rainwater and atmospheric aerosols in Sardinia,southern Mediterranean

The ionic composition of 55 aerosol samples and 31 precipitation events collected in a coastal site in southern Sardinia (Capo Carbonara, 39°06 N; 09°31 E) were compared. The samples were collected during one year period (Oct'90/Oct'91) and showed high variability in composition according to meteorological conditions. Rain and soluble part of aerosol showed a strikingly similar ionic composition: most significant anions were chlorine and sulphate, and sodium is the principal cations, followed by magnesium and calcium. The acid events are associated with N-NW trajectories (anthropogenic influxes from N. Europe) with avg. pH=4.65, non sea salt (nss) Ca=60 eq/l and NO₃/_nssSO₄=0.6. Southern precipitations are influenced by Saharan dust alkaline effects, with avg. pH=6.75,_nssCa=271 eq/l and NO₃/_nssSO₄=0.4. Na/Cl ratio in rain is similar to sea water (0.87), whilst in aerosols there is a Cl loss (Na/Cl=1.10), probably due to reaction with nitric acid. Total fluxes of Ca, Mg, NO₃ and SO₄ were 104, 9, 64 and 113 g/cm², and wet deposition exceeded (65–90%) dry deposition. Scavenging ratios (SR) as defined by the equation:SR=[(Ci)rain/(Ci)air] ^*d, (d=1200g/m³) were calculated, using geometric means (Ci) of precipitation and aerosols collected concurrently during the period (a total of 23 samples). The SR values are Ca=3400, Cl=2400, Na, K, SO₄=1700, Mg=1000 and NO₃=750. These numbers could be useful to infer total fluxes by using simply rainwater ionic composition in Mediterranean semi-arid sites like Sardinia.     

Disturbance effects on soil solution chemistry due to heating cable installation

Installation of heating cables for warming soil was used to evaluate the effect of disturbance on soil solution chemistry within a northern hardwood forest (Adirondack Mountains, New York). Differences in response among treatments suggested the importance of both the depth and timing of cable installation. There were increases (p>0.05) in many solutes within pilot study plots in which surrogate cable was installed at 15 cm depth. Most notably, mean nitrate concentrations for the 1st year following disturbance were 744 eq l^-1 at 15 cm depth compared to 7 eq l^-1 for the non-disturbed control. A comparison of pilot plots with 5 cm cable depth and an unheated soil-warming control plot with the same cable disturbance showed that the seasonality of soil disturbance may have a key role in response to disturbance. The soil solution response was diminished if installation occurred during the spring, a period of rapid uptake of nitrogen by vegetation. Mean nitrate concentrations were 176 eq l^-1 for 5-cm pilot plots (installed in fall 1991) versus 6 eq l^-1 for 5-cm, unheated soil-warming control plots (installed in spring 1992). Disturbance effects were attenuated over time and not generally apparent 1 year after installation.     

Identification of ergosterol in vesicular-arbuscular mycorrhizae

Summary Ergosta-5,7,22-tri-3-enol (ergosterol) was identified by gas chromatography-mass spectrometry in roots of berseem (Trifolium alexandrinum L., cv. Landsorte) and sweet corn (Zea mays L., cv. Honeycomb-F1) infected with the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus intraradices. The fungal-derived compound ergosterol was determined quantitatively in root extracts using reverse-phase high performance liquid chromatography. The concentrations of ergosterol in VAM-infected roots reached 72 g^-1 dry material in berseem and 52 g^-1 in sweet corn after 80 days of growth, whereas concentrations in non-infected roots remained below 8 g^-1 dry weight. Additionally, phytosterols such as -sitosterol, campesterol, and stigmasterol were detected in both infected and non-infected roots. Ergosterol, as a characteristic fungal substance, is proposed as an indicator of fungal biomass in the early stages of VAM infection.     

Technetium-99 toxicity in phaseolus vulgaris: Ultrastructural evidence for metabolic disorders

The influence of light intensity on the effects of 10^–6 mol L^{–1 99}Tc on growth, chlorophyll and carotenoid contents of bush bean plants was investigated. After germination and cotyledon excision, the plants were grown in a growth chamber either under low light (photosynthetic active radiation, PAR 144 E m^–2 s^–1) or higher light (PAR 307 E M^–2 s^–1) conditions. In plants grown under the higher light conditions, ⁹⁹Tc hardly affected CO₂-assimilation, dark respiration, pigment contents and growth. No toxicity symptoms were observed in these plants. Under low light conditions, ⁹⁹T c significantly decreased growth and the concentration of chlorophylls. Toxicity symptoms in the form of chlorosis and necrosis developed. Transmission electron microscopy (TEM) observations revealed alterations of chloroplast ultrastructure comparable to those described for plants slightly affected by paraquat toxicity or by Mo-deficiency. Our results indicate that in the low light plants ⁹⁹Tc induces damage in chloroplasts by peroxidation of membrane lipids.     

Effects of nitrification inhibitors on denitrification of nitrate in soil

Summary The influence of 28 nitrification inhibitors on denitrification of nitrate in soil was studied by determining the effects of different amounts of each inhibitor on the amounts of nitrate lost and the amounts of nitrite, N₂O and N₂ produced when soil samples were incubated anaerobically after treatment with nitrate or with nitrate and mannitol. The inhibitors used included nitrapyrin (N-Serve), etridiazole (Dwell), potassium azide, 2-amino-4-chloro-6-methylpyrimidine (AM), sulfathiazole (ST), 4-amino-1,2,4-triazole(ATC),2,4-diamino-6-trichloromethyl-s-triazine (CL-1580), potassium ethylxanthate, guanylthiourea (ASU), 4-nitrobenzotrichloride, 4-mesylbenzotrichloride, sodium thiocarbonate (STC), phenylmercuric acetate (PMA), and dicyandiamide (DCD).Only one of the nitrification inhibitors studied (potassium azide) retarded denitrification when applied at the rate of 10 g g^–1 soil, and only two (potassium azide and 2,4-diamino-6-trichloromethyl-s-triazine) inhibited denitrification when applied at the rate of 50 g g^–1 soil. The other inhibitors either had no appreciable effect on denitrification, or enhanced denitrification, when applied at the rate of 10 or 50 g g^–1 soil, enhancement being most marked with 3-mercapto-1,2,4-triazole. Seven of the inhibitors (potassium azide, sulfathiazole, potassium ethylxanthate, sodium isopropylxanthate, 4-nitrobenzotrichloride, sodium thiocarbonate, and phenylmercuric acetate) retarded denitrification when applied at the rate of 50 g g^–1 soil to soil that had been amended with mannitol to promote microbial activity.Reports that nitrapyrin (N-Serve) and etridiazole (Dwell) inhibit denitrification when applied at rates as low as 0.5 g g^–1 soil could not be confirmed. No inhibition of denitrification was observed when these compounds were applied at the rate of 10 g g^–1 soil, and enhancement of denitrification was observed when they were applied at the rate of 50 or 100 g g^–1 soil.     

Effect of drying and rewetting on mineralization and distribution of bacterial constituents in soil fractions

Summary Mineralization of ¹⁴C- and ¹⁵N-labelled whole bacteria, cytoplasm, and cell walls and their distribution in different soil fractions were studied during 211 days of incubation including two drying and rewetting cycles. With any of these three soil amendments, almost 60% of C derived from cellular constituents was released as CO₂, 15% was incorporated into the living microbial biomass and 25% was distributed into protected microbial metabolites or recalcitrant microbial products. The distribution of C and N derived from the amendments in the different soil fractions showed that constituents adsorbed on fine clay (<0.2 m were more rapidly decomposed than those adsorbed on silt (50-2 ) and coarse clay (2–0.2 ), indicating a faster organic matter turnover in fine clay than in silt and coarse clay. Although alternate soil drying and rewetting cycles did not significantly affect the mineralization of bacterial constituents, the cycles did have an important effect on the size and specific activities of newly formed microbial biomass. This suggests the presence of an active and a dormant fraction of soil biomass.     

Biogeochemistry of aluminum in a forest catchment in the Czech Republic impacted by atmospheric inputs of strong acids

The Lysina catchment in the Czech Republic was studied to investigate the biogeochemical response of Al to high loadings of acidic deposition. The catchment supports Norway spruce plantations and is underlain by granite and podzolic soil. Atmospheric deposition to the site was characterized by high H⁺ and SO₄ ^2– fluxes in throughfall. The volume-weighted average concentration of total Al (Al_t) was 28 mol L^–1 in the O horizon soil solution. About 50% of Al_t in the O horizon was in the form of potentially-toxic inorganic monomeric Al (Al_i). In the E horizon, Al_t increased to 71 mol L^–1, and Al_i comprised 80% of Al_t. The concentration of Al_t (120 mol L^–1) and the fraction of Al_i (85%) increased in the lower mineral soil due to increases in Al_i and decreases in organic monomeric Al (Al_o). Shallow ground water was less acidic and had lower Al_t concentration (29 mol L^–1). The volume-weighted average concentration of Al_t was extremely high in stream water (60 mol L^–1) with Al_i accounting for about 60% of Al_t. The major species of Al_i in stream water were fluorocomplexes (Al-F) and aquo Al³⁺. Soil solutions in the root zone were undersaturated with respect to all Al-bearing mineral phases. However, stream water exhibited Al_i concentrations close to solubility with jurbanite. Acidic waters and elevated Al concentrations reflected the limited supply of basic cations on the soil exchange complex and slow weathering, which was unable to neutralize atmospheric inputs of strong acids.     

Mercury in the Aquatic Environment of the Village of Caimito at the Mojana Region,North of Colombia

During May–September 1999, several aquatic environmental samples were collected from the village of Caimito, in the San Jorge River basin area, state of Sucre (Colombia), and analyzed for total mercury (T-Hg). Mean T-Hg concentration in sediments from surrounded marshes was 0.155 ± 0.016 g Hg/g. Low Hg concentrations were found in the phytoplanktivorous fish species Prochilodus magdalenae (0.087 ± 0.01 g Hg/g), while four-fold greater concentrations were found in all the carnivorous species. In average, T-Hg concentrations for fish samples did not exceed the limit consumption level (0.5 g Hg/g). However, risk assessment based on the hazard index suggested that the consumption of 0.1 kg per day of carnivorous fish could increase the risk of mercury poisoning in local population.     

Suppression of methane oxidation in aerobic soil by nitrogen fertilizers,nitrification inhibitors,and urease inhibitors

Concentrations of CH₄, a potent greenhouse gas, have been increasing in the atmosphere at the rate of 1% per year. The objective of these laboratory studies was to measure the effect of different forms of inorganic N and various N-transformation inhibitors on CH₄ oxidation in soil. NH ₄ ⁺ oxidation was also measured in the presence of the inhibitors to determine whether they had differential activity with respect to CH₄ and NH ₄ ⁺ oxidation. The addition of NH₄Cl at 25 g N g^-1 soil strongly inhibited (78–89%) CH₄ oxidation in the surface layer (0–15 cm) of a fine sandy loam and a sandy clay loam (native shortgrass prairie soils). The nitrification inhibitor nitrapyrin (5 g g^-1 soil) inhibited CH₄ oxidation as effectively as did NH₄Cl in the fine sandy loam (82–89%), but less effectively in the sandy clay loam (52–66%). Acetylene (5 mol mol^-1 in soil headspace) had a strong (76–100%) inhibitory effect on CH₄ consumption in both soils. The phosphoroamide (urease inhibitor) N-(n-butyl) thiophosphoric triamide (NBPT) showed strong inhibition of CH₄ consumption at 25 g g^-1 soil in the fine sandy loam (83%) in the sandy clay loam (60%), but NH ₄ ⁺ oxidation inhibition was weak in both soils (13–17%). The discovery that the urease inhibitor NBPT inhibits CH₄ oxidation was unexpected, and the mechanism involved is unknown.     

Effect of heavy metals on growth and survival of Macrophomina phaseolina (Tassi) Goid.

Summary The effects of Cd, Co, Ni and Zn on growth and survival of Macrophomina phaseolina were studied in vitro. Cd, Ni and Co at 500 g ml^–1 inhibited growth by 78.8%, 73.6% and 11.8%, respectively, after 4 days at 25 ± 1°C. The mycelial dry weight yield was enhanced by 2.1% at 100 g ml^–1 Zn. The population of the pathogen declined in soil amended separately with Cd, Co, Ni and Zn. Cd (4000 mg kg^–1) proved to be the most toxic, by completely inhibiting the survival of the pathogen in soil after 20 days.     

Condition factor and whole-body sodium concentrations in a freshwater fish: Evidence for acidification stress and possible ionoregulatory over-compensation

Condition factor, K, was measured for 1202 blacknose dace (Rhinichthys atratulus) from three streams in Shenandoah National Park (USA) of different acid neutralizing capacities (ANCs). K is a ratio of weight standardized to length; it is an indication of the health of the individuals in a population. R. atratulus condition factor in the low-ANC stream was found to be significantly lower (11%) than that of dace measured for fish from the intermediate- and high-ANC streams. This difference, according to the results of related investigations, is likely to be biologically significant. Whole-body sodium concentrations were measured as an additional test of sublethal stress in these streams. During summer base flow conditions, mean whole-body sodium concentrations of adult R. atratulus maintained in cages were found to be highest in the low-ANC stream and lowest in the high-ANC stream. The lower condition factor of dace in the low-ANC stream may be related to whole-body sodium concentration and ion regulation. Ion regulation in the low-ANC stream may be more metabolically costly because of chronic sublethal pH stress. R. atratulus may maintain high body Na⁺ concentrations in low ANC- and ionic strength waters in order to provide a buffer against large episodic pH depressions. The metabolic cost of this ionoregulatory over-compensation may necessitate the diversion of energy from somatic growth and explain the poorer condition of fish from such waters.     

Relation between sulphur concentrations in the Scots pine needles and the air in northernmost Europe

The SO₂ emissions from the Kola Peninsula in Arctic Russia (totalling around 600 Gg(SO₂) yr^–1 at the beginning of the 1990s) produce an atmospheric SO₂ concentration gradient to the northernmost Europe. This gradient covers the range from >50 g m^–3 in the vicinity of the sources to 1 g m^–3 in Finnish Lapland. In the present study, the measured sulphur concentrations in Scots pine needles were compared with the estimated distribution of atmospheric SO₂. The total sulphur concentrations in the needles ranged from 741 to 2017 mg kg^–1. Strongly elevated concentrations (> 1200 mg kg^–1) were found within 40 km from the smelters corresponding to an area where the annual mean atmospheric SO₂ concentration exceeded 10 g m^–3. The foliar sulphur concentrations (total, organic and inorganic) show a high correlation with the estimated mean SO₂ concentration distribution in the air. Consequently the foliar sulphur concentrations reflected the atmospheric sulphur load well. The data presented here show that uptake via stomata is an important deposition pathway also in the arctic conditions with a short growing season.     

The toxic mixing zone of neutral and acidic river water: Acute aluminium toxicity in brown trout (Salmo trutta L.)

Mixing of acid river water containing aluminium (pH 5.1, Al 345 g.l^–1) with neutral water of a lake (pH 7.0, Al 73 g.l^–1) resulted in water (pH 6.4, Al 245 g.l^–1) with a pH (6.4) and Al concentration (245 g.l^–1) expected to have low toxicity to fish on the basis of current Al toxicity models. However, under semi-field conditions the freshly mixed water (a few sec. after mixing) proved to be highly toxic to brown trout. The fish were exposed to the water at different places along a 30 m channel. At the beginning of the channel acid and neutral water were continuously mixed; the mixed water left the channel after 340 sec. The cells of the gills showed a highly increased rate of cell death by apoptosis and necrosis. Intercellular spaces were enlarged, and many leucocytes penetrated in these spaces. Mucus release was stimulated to depletion. Plasma chloride levels were hardly affected. There was a clear gradient in the deleterious effects on the fish along the channel. The fish at the beginning of the channel (about 12 sec. after mixing of the water), were severely affected, whereas the fish kept at the end of the channel (340 sec. after mixing) were only mildly affected. In the natural situation fish will relatively quickly pass through a mixing zone. In our study we therefore focused on the effects on fish after a 60 min exposure to a mixing zone (5 sec after mixing), with subsequent recovery in a region downstream of the confluence and in neutral water with low Al. The recovery in the downstream area (at the end of the channel, i.e. 5 min after mixing) was clearly hampered when compared to the recovery in neutral water with low aluminium. Thus, a short exposure to the toxic mixing zone followed by a stay in water downstream of this zone, as may occur in nature, is detrimental to migrating trout. We conclude that freshly mixed acid and neutral water contain toxic components during the first seconds to minutes after mixing, that can not be explained by current models on aluminium toxicity.     

Seasonal changes and the effects of fertiliser on some chemical,biochemical and microbiological characteristics of high-producing pastoral soil

Summary A 2-year study (1983–1984 to 1984–1985) was conducted to estimate temporal and seasonal changes and the effects of fertiliser on some soil chemical, biochemical and microbiological characteristics. The soil used was a Typic Vitrandept under grazed pasture. Soil samples were taken regularly to a depth of 75 mm from paired unfertilised and fertilised (500 kg ha^– 30% potassic superphosphate) plots. Except for organic C, fertiliser had little or no effect on the characteristics measured. Organic C averaged about 9.2% in unfertilised soil and was about 0.3% higher in the fertilised soil. The size of the microbial biomass fluctuated widely in the 1st year (3000 g C g^–1 in February to 1300 g C g^–1 in September) but there was less variation in the 2nd year (range 1900 g C g^–1 to 2500 g C g^–1 soil). CO₂ production values (10- to 20-day estimates averaged 600 g of CO₂-C g^–1 soil) were generally higher in spring compared to the rest of the year. Water extractable C increased over winter and declined through spring in both years (range 50 g C g^–1 soil to 150 g C g^–1 soil). Mineral-N flush values were higher in summer (300 g N g^–1 soil) and lower in winter months (200 g N g^–1 soil). The pattern of variation of microbial N values was one of gradual accumulation followed by rapid decline. This rapid decline in values occurred in spring and autumn (range 130–220 g N g^–1 soil). N mineralisation and bicarbonate-extractable N showed no clear trend; these values ranged from 100–200 and 122–190 g N g^–1 soil, respectively. There was a significant correlation (0.1%) between N mineralisation and bicarbonate-extractable N in the late summer-autumn-early winter period (February–August) in both years but not in spring. These results and their relationships to climatic factors and rates of pasture production are discussed.     

Selenium in Water,Sediment, Plants,Invertebrates, and Fish in the Blackfoot River Drainage

Nine stream sites in the Blackfoot River watershed in southeastern Idaho were sampled in September 2000 for water, surficial sediment, aquatic plants, aquatic invertebrates, and fish. Selenium was measured in these aquatic ecosystem components, and a hazard assessment was performed on the data. Water quality characteristics such as pH, hardness, and specific conductance were relatively uniform among the nine sites examined. Selenium was elevated in water, sediment, aquatic plants, aquatic invertebrates, and fish from several sites suggesting deposition in sediments and food web cycling through plants and invertebrates. Selenium was elevated to concentrations of concern in water at eight sites (>5 g/L), sediment at three sites (>2 g/g), aquatic plants at four sites (>4 g/g), aquatic invertebrates at five sites (>3 g/g), and fish at seven sites (>4 g/g in whole body). The hazard assessment of selenium in the aquatic environment suggested low hazard at Sheep Creek, moderate hazard at Trail Creek, upper Slug Creek, lower Slug Creek, and lower Blackfoot River, and high hazard at Angus Creek, upper East Mill Creek, lower East Mill Creek, and Dry Valley Creek. The results of this study are consistent with results of a previous investigation and indicate that selenium concentrations from the phosphate mining area of southeastern Idaho were sufficiently elevated in several ecosystem components to cause adverse effects to aquatic resources in the Blackfoot River watershed.