Nitrogen critical loads and management alternatives for N-impacted ecosystems in California.

Empirical critical loads for N deposition effects and maps showing areas projected to be in exceedance of the critical load (CL) are given for seven major vegetation types in California. Thirty-five percent of the land area for these vegetation types (99,639 km(2)) is estimated to be in excess of the N CL. Low CL values (3-8 kg N ha(-1) yr(-1)) were determined for mixed conifer forests, chaparral and oak woodlands due to highly N-sensitive biota (lichens) and N-poor or low biomass vegetation in the case of coastal sage scrub (CSS), annual grassland, and desert scrub vegetation. At these N deposition critical loads the latter three ecosystem types are at risk of major vegetation type change because N enrichment favors invasion by exotic annual grasses. Fifty-four and forty-four percent of the area for CSS and grasslands are in exceedance of the CL for invasive grasses, while 53 and 41% of the chaparral and oak woodland areas are in exceedance of the CL for impacts on epiphytic lichen communities. Approximately 30% of the desert (based on invasive grasses and increased fire risk) and mixed conifer forest (based on lichen community changes) areas are in exceedance of the CL. These ecosystems are generally located further from emissions sources than many grasslands or CSS areas. By comparison, only 3-15% of the forested and chaparral land areas are estimated to be in exceedance of the NO(3)(-) leaching CL. The CL for incipient N saturation in mixed conifer forest catchments was 17 kg N ha(-1) yr(-1). In 10% of the CL exceedance areas for all seven vegetation types combined, the CL is exceeded by at least 10 kg N ha(-1) yr(-1), and in 27% of the exceedance areas the CL is exceeded by at least 5 kg N ha(-1) yr(-1). Management strategies for mitigating the effects of excess N are based on reducing N emissions and reducing site N capital through approaches such as biomass removal and prescribed fire or control of invasive grasses by mowing, selective herbicides, weeding or domestic animal grazing. Ultimately, decreases in N deposition are needed for long-term ecosystem protection and sustainability, and this is the only strategy that will protect epiphytic lichen communities.

Atmospheric deposition inputs and effects on lichen chemistry and indicator species in the Columbia River Gorge, USA.

Topographic and meteorological conditions make the Columbia River Gorge (CRG) an 'exhaust pipe' for air pollutants generated by the Portland-Vancouver metropolis and Columbia Basin. We sampled fog, bulk precipitation, throughfall, airborne particulates, lichen thalli, and nitrophytic lichen distribution. Throughfall N and S deposition were high, 11.5-25.4 and 3.4-6.7 kg ha(-1) over 4.5 months at all 9 and 4/9 sites, respectively. Deposition and lichen thallus N were highest at eastern- and western-most sites, implicating both agricultural and urban sources. Fog and precipitation pH were frequently as low as 3.7-5.0. Peak NO(x), NH(3), and SO(2) concentrations in the eastern CRG were low, suggesting enhanced N and S inputs were largely from particulate deposition. Lichens indicating nitrogen-enriched environments were abundant and lichen N and S concentrations were 2x higher in the CRG than surrounding national forests. The atmospheric deposition levels detected likely threaten Gorge ecosystems and cultural resources.

Effects of season and low-level air pollution on physiology and element content of lichens from the U.S. Pacific Northwest.

Lichens were collected from three low-elevation sites in the western Cascade Range: HJ Andrews, OR (clean) and Bull Run, OR, and Pack Forest, WA (moderately enhanced nitrogen and sulfur deposition). The latter sites were within 50 km of Portland and Seattle/Centralia urban-industrial areas, respectively. Tissue concentrations of sulfur, nitrogen, and other macronutrients; rates of net carbon uptake; concentrations of photosynthetic pigments; and thallus density were correlated with season and seasonal changes in Platismatia glauca. Ion concentrations in precipitation and total wet deposition were measured from natural settings. Concentrations of depositional ions in precipitation, including NO3- and NH4+, were generally highest at Bull Run and Pack Forest; SO4(2-) concentrations and acidity were highest at Pack Forest. Total wet deposition was higher in the winter rainy season than the dry summer season at all three sites. Lichens adapted physiologically and morphologically to the higher light intensity and the warm, dry climate of summer through decreased optimal water content for CO2 uptake, increased concentrations of carotenoids and increased thallus density. Compared to the clean site, the sites with enhanced deposition were associated in P. glauca with year-round higher tissue concentrations of N, S, K, and Na; higher concentrations of total chlorophyll and carotenoids; higher OD435/415 ratios; higher CO2 uptake and lower thallus density in summer; and a general absence of other sensitive lichens. These results indicate that moderate levels of fertilizing air pollutants can stimulate carbon uptake and provide protection against chlorophyll degradation in air pollution-tolerant lichens of the Pacific Northwest, especially during the dry summer season.

Simultaneous analysis of some amphetamine derivatives in urine by nonaqueous capillary electrophoresis coupled to electrospray ionization mass spectrometry.

A nonaqueous capillary electrophoresis method, coupled to UV and electrospray mass spectrometry (ESI-MS), is described for the simultaneous analysis of Ecstasy and other related derivatives. Several electrophoretic and ESI-MS parameters were systematically investigated, such as electrolyte nature and concentration, organic solvent and sheath liquid compositions, nebulization gas pressure and drying gas flow-rate. The best results were achieved with an acetonitrile-methanol (80:20, v/v) mixture containing 25 mM ammonium formate and 1 M formic acid, an applied voltage of 30 kV and a separation temperature of 15 degrees C. Under optimized CE-ESI-MS conditions, separation of the investigated drugs was performed in less than 6 min, with a high efficiency. Method precision based on migration time and peak area was determined and the limits of detection, which depend on the tested compound, were established between 20 and 70 ng ml(-1) in the selected ion monitoring mode. Finally, the described method was successfully applied to the analysis of amphetamines in urine after a liquid-liquid extraction.

Empirical and simulated critical loads for nitrogen deposition in California mixed conifer forests.

Empirical critical loads (CL) for N deposition were determined from changes in epiphytic lichen communities, elevated NO(3)(-) leaching in streamwater, and reduced fine root biomass in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) at sites with varying N deposition. The CL for lichen community impacts of 3.1 kg ha(-1) year(-1) is expected to protect all components of the forest ecosystem from the adverse effects of N deposition. Much of the western Sierra Nevada is above the lichen-based CL, showing significant changes in lichen indicator groups. The empirical N deposition threshold and that simulated by the DayCent model for enhanced NO(3)(-)leaching were 17 kg N ha(-1) year(-1). DayCent estimated that elevated NO(3)(-) leaching in the San Bernardino Mountains began in the late 1950s. Critical values for litter C:N (34.1), ponderosa pine foliar N (1.1%), and N concentrations (1.0%) in the lichen Letharia vulpina ((L.) Hue) are indicative of CL exceedance.

Separation of four isomeric tropane alkaloids from Schizanthus grahamii by non-aqueous capillary electrophoresis.

The potential of non-aqueous capillary electrophoresis was investigated for the separation of four isomeric tropane alkaloids, namely 3alpha-senecioyloxy-7beta-hydroxytropane, 3alpha-hydroxy-7beta-senecioyloxytropane, 3alpha-hydroxy-7beta-angeloyloxytropane and 3alpha-hydroxy-7beta-tigloyloxytropane extracted from Schizanthus grahamii. The composition of the organic solvent and the nature of the electrolyte were of considerable importance with respect to selectivity. Different organic solvents (i.e. methanol, ethanol, acetonitrile, tetrahydrofuran) and mixtures thereof were investigated. Moreover, different electrolytes such as formate, acetate and trifluoroacetate were tested. After optimisation, an electrolyte consisting of 1 M trifluoroacetic acid and 25 mM ammonium trifluoroacetate in methanol:ethanol (40:60, v:v) was selected. It provided an efficient separation of the four positional isomers as well as a good repeatability of migration time (RSD < 0.2%). The method was successfully used with electrospray MS to confirm the molecular mass of the tropane alkaloids.