Concentrations In July Research Articles

Jun localization in cytosolic and nuclear compartments in brain–pituitary system of the frog, Rana esculenta: an analysis carried out in parallel with GnRH molecular forms during the annual reproductive cycle

The presence of c-jun like mRNA was assessed in the brain of the frog, Rana esculenta, during the annual sexual cycle. In parallel, Jun protein and GnRH molecular form (mammalian and chicken II also indicated as GnRH1 and GnRH2, respectively) activity was studied in order to establish possible relationships. Northern blot analysis of total RNA reveals the presence of a 2.7 kb c-jun-like mRNA. Western blots, carried out on cytoplasmic and nuclear protein extracts, show the presence of Jun immunoreactive band of 39 kDa in brain and pituitary. Fluctuations of c- jun-like mRNA and Jun immunoreactive protein (cytoplasmic and nuclear) levels in brains during the year indicate relationships among transcription, translation, and nuclear activity. In particular, mRNA levels increase gradually from September until November when Jun protein concentration peaks in cytosolic extracts. Conversely, the nuclear protein reaches highest concentration in July when the cytosolic level shows low values. Immunocytochemical studies confirm the presence of Jun immunoreactivity in both cytoplasmic and nuclear compartments of several brain areas, including those primarily involved in gonadotropin discharge (e.g., anterior preoptic area and preoptic nucleus). GnRH molecular forms and Jun are colocalized in anterior preoptic area and preoptic nucleus. Moreover, during the period characterized by GnRH release, Jun levels strongly decrease in nuclei. Finally, we show that treatments with a GnRH analog (buserelin, Hoechst, Frankfurt) increase Jun levels in brain nuclear extracts.

Water quality in the Red Sea coastal waters (Egypt): Analysis of spatial and temporal variability

In order to provide a background picture of the water quality of the Egyptian Red Sea a number of hydrological and chemical parameters have been measured bimonthly in 2000. Few data are available on this area, which is apparently subjected to an increasing human impact due to recreational (swimming and diving), industrial (mainly phosphate shipping and industry) and fishing/harbor activities. The results of the present study indicate that changes in the salinity and pH were not significant with highly oxygenated seawaters. The levels of suspended solids (as total suspended matter, TSM) and chlorophyll-a (Chl-a) were generally low and showed an homogeneous distribution in the study region. The ratio of chlorophyll-a to total suspended matter concentrations increased between November and March and decreased from May to September. Chlorophyll-a was significantly correlated with transparency and total suspended matter concentrations in July, September and November. Nitrogen, phosphorus and reactive silicate concentrations were generally low, and allowed classifying the Egyptian Red Sea coastal water as oligotrophic to mesotrophic. The middle region of the study area, which was located between Safaga and Qusair displayed relatively high phosphate contents when compared with other coastal areas. The high values of N:P ratios indicate that PO 4 -P is the limiting factor for phytoplankton growth in the Red Sea coastal waters, with the possible exception of the middle region. Significant relationships were found between chlorophyll-a concentrations and nutrient levels in different sampling periods. Spatial distribution patterns of the studied variables revealed that productivity of the Red Sea coastal waters is mostly controlled by phosphate concentrations, salinity, temperature and dissolved oxygen.

Use of Natural 35 S to Trace Sulphate Cycling in Small Lakes, Flattops Wilderness Area, Colorado, U.S.A.

Measurements of the cosmogenically-produced 35S, a radioisotope of sulphur (t1/2 = 87 days), are reported for the Ned Wilson Lake watershed in Colorado. The watershed contains two small lakes and a flowing spring presumed to be representative of local ground water. The watershed is located in the Flattops Wilderness Area and the waters in the system have low alkalinity, making them sensitive to increases in acid and sulphate deposition. Time series of 35S measurements were made during the summers of 1995 and 1996 (July–September) at all three sites. The system is dominated by melting snow and an initial concentration of 16–20 mBq L-1 was estimated for snowmelt based on a series of snow samples collected in the Rocky Mountains. The two lakes had large initial 35S concentrations in July, indicating that a large fraction of the lake water and sulphate was introduced by meltwater from that year's snowpack. In 1995 and 1996, 35S concentrations decreased more rapidly than could be accounted for by decay, indicating that other processes were affecting 35S concentrations. The most likely explanation is that exchange with sediments or the biota was removing 35S from the lake and replacing it with older sulphate devoid of 35S. In September of 1995 and 1996, 35S concentrations increased, suggesting that atmospheric deposition is important in the sulphate flux of these lakes in late summer. Sulphur-35 concentrations in the spring water were highly variable but never higher than 3.6 mBq L-1 and averaged 2 mBq L-1. Using a simple mixing model, it was estimated that 75% of the spring water was derived from precipitation of previous years.

Role of climate feedback on methane and ozone studied with a Coupled Ocean‐Atmosphere‐Chemistry Model

We present results from two experiments carried out with a coupled ocean‐atmosphere‐tropospheric chemistry model run continously over the period 1990 to 2100. In the control experiment, climate is unforced, but emissions of trace gases to the chemical model increase in line with an illustrative scenario for future trace gas emissions with medium high growth. In the climate change experiment trace gas emissions are identical to the control, but climate is also forced using greenhouse gas concentrations and SO2 emissions from the same scenario. Global average methane in the climate change experiment increased from 1670 ppbv in 1990 to 3230 ppbv by 2100, compared to 3650 ppbv by 2100 in the control. The methane increase in the control experiment is therefore 27% more than in the control. This difference is due to both temperature and OH changes which increase the rate of methane oxidation and act in the opposite direction to the negative feedback of methane on itself through OH. Mid‐latitude northern hemisphere ozone concentrations in July for the mid‐troposphere rose from 39 ppbv in 1990s to 64 ppbv in the 2090s in the control experiment and to 49 ppbv in the climate change experiment. The direct role of climate change is therefore predicted to be a negative feedback on the radiative forcing from the change to tropospheric ozone and methane concentrations.

Analysis of air pollution in two major Korean cities: trends, seasonal variations, daily 1-hour maximum versus other hour-based concentrations, and standard exceedances

This study considers the characteristics of carbon monoxide (CO), nitrogen dioxide (NO 2), ozone (O 3) and sulfur dioxide (SO 2) in two major South Korean cities, including the capital city of Seoul, over a time period of 7–8 years. Changes in the annual mean and percentiles of the daily 1-h maximum and other hour-based concentrations varied according to the compound and city type. Seasonal variations varied according to the compound, yet not with the city type. Both Seoul and Taegu exhibited lower O 3 concentrations in July compared to other summer months. There was a high degree of correlation between the daily 1- and 8-h maximum or daily mean concentrations of all compounds in both cities, with an R 2 of 0.66–0.90 at p<0.0001. It was indicated that for CO and O 3, the 8-h standard was more stringent than the 1-h standard, while for NO 2 and SO 2, the 1-h standard was more stringent than the 24-h standard. The correlation coefficients between the daily 1-h maximum and daily mean concentrations decreased as the maximum concentration values of NO 2, O 3 , and SO 2 increased in the two cities. For all the target compounds, Seoul recorded a substantially higher frequency of days with concentrations above the relevant 1-, 8-, and 24-h standards compared to Taegu.

Distribution and air–sea gas exchange of dimethyl sulphide at the European western continental margin

Abstract The concentrations of dissolved dimethyl sulphide (DMS) were measured on cruises aboard the R/V Meteor from Las Palmas, Gran Canaria, to Bremen, Germany (7–22 September 1994) and aboard the R/V Valdivia from Cork, Ireland, to Hamburg, Germany, via Cascais, Portugal (14 July–1 August 1995). The arithmetic means (ranges) of the DMS concentrations were 2.8 nM (0.6–33.4 nM, n =208) in September 1994 and 7.2 nM (2.9–38.5 nM, n =393) in July 1995. The distribution of dissolved DMS was characterised by higher mesoscale variability in July than in September. Patches of elevated DMS concentration were consistently associated with frontal regions along the Celtic Sea margin and on the shelf as well as with wind-driven upwelling along the Iberian margin. The pronounced difference between July and September concentrations is attributed to the seasonal pattern of dissolved DMS in the study area. DMS concentrations showed little correlation with chlorophyll a (chl a ), 19′-hexanoyloxy-fucoxanthin, or other selected chemotaxonomic pigment biomarkers. On the contrary, the chlorophyll-normalised DMS concentrations in July 1995 (45 nmol DMS/μg chl a ) were about a factor of 5.5 higher than those in September 1994 (8 nmol DMS/μg chl a ). Our results and a compilation of presently available data suggest that the DMS-to-chlorophyll ratios follow a sinusoidal pattern with peak values around July. The implications of these findings are discussed in relation to seasonal changes in DMS cycling and sea-to-air fluxes along the western European continental margin.

Organic compounds in the extrapalial fluid and haemolymph of Anodontacygnea (L.) with emphasis on the seasonal biomineralization process

Bivalve mollusks, such as the freshwater mussel Anodonta cygnea, show seasonal changes in calcification. This cycle of calcification must either be a cause or a consequence for seasonal fluctuations in the organic composition of the animal’s fluids, haemolymph and extrapallial fluid, the liquid media for biomineralization. We monitored the fluids of A. cygnea, throughout a 1-year cycle, for the presence of organic constituents, known to be important for biomineralization, such as proteins, glycosaminoglycans (GAGs) and hexosamines. Proteins were subjected to further study, namely through the total amino acid determination and fraction separation by agarose gel electrophoresis. GAG levels were fairly constant throughout the year, with a maximum concentration in July and a minimum in January, a feature also detected for glucosamine, although with higher fluctuations. Proteins showed highly increased concentrations during June and July, both in total amounts and individual fractions. All fractions showed similar trends throughout the year, with lowest general levels in October, the starting month of a period when some fractions were not detectable at all. All fractions ended this low period in May, when a sometimes-important increase could be detected. As to the total amino acid composition of the fluids, the general trend followed that of proteins, except for ornithine (Orn), a non-proteic amino acid. The overall fluctuations detected in the biological fluids of A. cygnea suggest that the main variation related to the calcification cycle must be quantitative, since no different compounds appear in specific periods, to achieve also specific results.

Effects of Restoration Thinning on Presettlement Pinus ponderosa in Northern Arizona

AbstractIn the 100 years following the arrival of Euro‐American settlers in northern Arizona, Pinus ponderosa (ponderosa pine) forests changed from open, low‐density stands to closed, high‐density stands. The increase in tree density has been detrimental to the vigor of old‐growth trees that established before settlement (presettlement trees). In this study, we examined whether the vigor of presettlement trees could be improved by restoring the original stand structure by thinning the ponderosa pines that established after settlement (postsettlement trees). The restoration treatment caused the following changes in the presettlement trees and their environment in the first year following thinning: an increase in volumetric soil water content between May and August, an increase in predawn xylem water potential in July and August, a decrease in midday xylem water potential in June and August, an increase in net photosynthetic rate in August, an increase in foliar nitrogen concentration in July and August, and an increase in bud and needle size. The results show that the thinning restoration treatment improved the condition of presettlement ponderosa pines by increasing canopy growth and the uptake of water, nitrogen, and carbon.

Seasonal accumulation of ultraviolet‐B screening pigments in needles of Norway spruce (Picea abies (L.) Karst.)

Conifer needles are highly effective in screening ultraviolet‐B radiation (280–320 nm). This ability is mainly attributed to the presence of flavonoids and hydroxycinnamic acids in the epidermal tissue. In two field cabinet experiments with two different clones of Norway spruce we assessed the seasonal accumulation of UV‐B screening pigments under near‐ambient, and close‐to‐zero UV‐B irradiation. At the beginning of needle development, i.e. in June, kaempferol 3‐O‐glucoside was the dominant UV‐B screening pigment. It was replaced during needle differentiation by the more effective diacylated flavonol glucosides, particulary kaempferol 3‐O‐(3",6"‐O‐di‐p‐coumaroyl)‐glucoside, which reached highest concentrations in July. In addition to the soluble pool of diacylated flavonol glucoside derivatives, a cell wall‐bound UV‐B screen in the epidermal cell walls was formed during needle differentiation, consisting mainly of p‐coumaric acid and kaempferol 3‐O‐glucoside. An effect of UV‐B radiation on the accumulation of diacylated flavonol glucosides was only observed in 1996 with clone 2, when the concentrations of kaempferol 3‐O‐(3",6"‐O‐di‐p‐coumaroyl)‐glucoside were significantly higher in July and August under field, and near‐ambient than under close‐to‐zero UV‐B irradiance. For wall‐bound p‐coumaric acid and kaempferol 3‐O‐glucoside UV‐B radiation enhanced the concentrations of these compounds by approximately 20% in relation to the concentrations in close‐to‐zero UV‐B‐treated plants in both field cabinet experiments.

Irrigation and Fertilizer Application Methods Affect Performance of High-density Peach Orchards

Seven treatment combinations of irrigation and fertilizer were compared in a high-density (606 trees/ha) management system for peach [Prunus persica (L.) Batsch cv. Harrow Beauty/Bailey] on Fox sand in southwestern Ontario. Each treatment combination had an irrigation component (N = nonirrigated, D = drip irrigated, or M = microsprinkler irrigated) and a fertilizer placement component (B = banded fertilizer, L = low fertigation, or H = high fertigation). NB and DB are commonly used systems in Ontario, while the other five treatment combinations were experimental. Total soil water in the top 110 cm of soil was lowest under NB but was never at the permanent wilting point. Trunk cross-sectional area was largest under DH and DB, smallest under ML and NB, and intermediate for the other three treatment combinations. No symptoms of N or K deficiency or toxicity were noted for any of the fertilizer treatments. Leaf analyses in July and September indicated that most major and minor elements were in the adequate to slightly excess range. However, there were no significant treatment effects on leaf nutrient concentrations in July or September when averaged over the five years, except for Mg in July. There were large and significant year effects on leaf nutrient concentrations but no significant treatment × year interactions. During the first four cropping years, there were no significant treatment effects, averaged over years, for total yield, marketable yield, or cumulative yield efficiency; however, there were large year effects but no treatment × year interactions for these factors. There was no detectable yield advantage for D vs. M irrigation. B application of N and K promoted no higher yields than fertigation equivalent to the B rate or 50% of this rate. Fertigation of N and K during the first 4 years of this experiment did not provide a detectable yield advantage to warrant the added cost and labor associated with this system compared with the B applications of N and K.

The Braer oil spill—Hydrocarbon concentrations in intertidal organisms

The concentrations of non-specific narcotic toxins such as the aromatic hydrocarbons toluene, naphthalene and phenanthrene were determined in specimens of limpets ( Patella vulgata) and razor shells ( Ensis spp.) collected from Shetland at the time of the Braer oil spill (84 000 t of Gullfaks production crude) and 3, 6 and 15 months after the spill. The analytical methods involved the use of deuterated analogues of the toxins to account for losses of analytes during recovery by steam distillation and determination by cryogenic GC-MS selected ion monitoring of molecular ions. Although the organisms were impacted by oil, the concentrations of total determinants in dead razor shells collected just after the oil spill were below the tissue effective concentrations for 50% reduction in filtering activity (TEC 50) for mussels (the most valid toxicological data available for comparative purposes). A portion of the unresolved monoaromatic hydrocarbons of Gullfaks crude would probably add to the burden of toxins, but this was not measured in this study. The distribution of aromatic hydrocarbons in the organisms (phenanthrenes > naphthalenes > toluene) was the reverse of that in the oil and correlates with the expected bioconcentration behaviour of hydrophobic organics whereby less water soluble compounds with higher octanol-water partition coefficients are concentrated. Concentrations of naphthalene to methylphenanthrenes in limpets collected in January at the time of the spill from sites close to the wreck were well below the TEC 50 values for mussels but comparison with the lower concentrations in limpets from a more remote site in Shetland indicated that the oil had impacted organisms near to the spill, consistent with intertidal survey data. Comparison with limited literature data for limpets and more extensive data for mussels also supported this conclusion, as did the identification of the oil residues in the limpets by biomarker fingerprinting. As with the razor shells, bioconcentration of the more hydrophobic compounds was observed. Concentrations in Shetland limpets generally decreased with increasing distance from the spill site. Concentrations of aromatic hydrocarbons decreased with time after the spill, such that by July concentrations were at what can reasonably be assumed to be background levels, comparable to the concentrations found at all times in the more remote site. Concentrations in a limited number of samples collected 15 months after the spill, following a further winter of storms in which sediment-sorbed oil could have been reintroduced to the limpets, showed no increase.

亜熱帯太平洋域小笠原諸島母島において測定された大気中の過酸化水素濃度

Concentrations of gaseous H 2 O 2 and O 3 have been measured at Ogasawara Hahajima Island located 1000 km south of Tokyo in April and July 1995. In April, when the Ogasawara Islands was covered with the continental air mass, O 3 and H 2 O 2 concentrations were high. Although O 3 concentration in July. was significantly lower than that in April, the mean H 2 O 2 concentration in July was higher than in April. This may be due to a difference in the solar radiation. Hydrogen peroxide concentration was usually higher in daytime than at night. However, the increases of H 2 O 2 concentrations were sometimes observed in the nighttime when the relative humidity was low. The nocturnal decrease of H 2 O 2 concentration was strongly dependent on the relative humidity; in other words, H 2 O 2 concentration is somewhat inversely proportional to the relative humidity. The loss of H 2 O 2 at night is caused by a heterogeneous process in the marine atmosphere. The heterogeneous loss rate was estimated at 0.3 to 6.5 × 10 -5 s -1 and was greatly influenced by the relative humidity. This process may significantly: affect HO x concentrations in the marine atmosphere.

Effect of repeated sprays of 6-benzyladenine on the formation of sylleptic shoots in apple in the fruit-tree nursery

In 1992 growing shoot tips of nursery trees of the apple cultivar ‘Red Boskoop’ on rootstock M.9 (budded August 1991 at 15 cm) were sprayed four or eight times at weekly intervals with 50, 100, 200, or 400 p.p.m. 6-benzyladenine (BA), starting when scion length was 35 cm. The eight BA treatments were compared with untreated controls and with plants sprayed once with the standard branching agent Promalin, a mixture of equal quantities of BA and GA 4+7 (gibberellins A 4 and A 7), 1000 p.p.m. of each hormone being used. All sprays contained the wetter Tween 20 at 1% v/v. Except for 50 p.p.m., all BA treatments increased the number of laterals and the more so the higher the concentration and the number of sprays. Eight sprays with 200 and 400 p.p.m. BA and four with 400 p.p.m. BA gave more laterals than a Promalin application. The most active BA treatments enlarged the zone of lateral emergence by 50 cm. The treatments did not or hardly affected stem diameter or length and there was no temporary slowing down of the growth of the stem tip that could explain the extra development of laterals. Neither Promalin nor the 50 or 100 p.p.m. BA sprays affected flower-bud formation, but continuing the use of higher BA concentrations in July by spraying eight times proved detrimental.

Lead, arsenic, cadmium and copper in Lake Asososca, Nicaragua

The present study of lead, arsenic, cadmium and copper was carried out between July 1991 and April 1992 in the water and sediment of Lake Asososca. The concentrations of lead in water were within normal limits for drinking water, but significant differences from month to month were found. No significant difference was found either between the concentrations at each sample station or between the concentrations at each sample depth. Arsenic concentrations were within a relatively normal range, but the concentrations in July was significantly lower than in the rest of the year. Cadmium and copper concentration levels were normal. In the superficial sediment of the lake, the cadmium and copper concentration levels were similar in the whole lake. The lead and arsenic contents in sediment were significantly higher at the pumping station than at the rest of the sampling points.

DISTRIBUTION AND GRAIN‐SIZE PARTITIONING OF METALS IN BOVFOM SEDIMENTS OF AN EXPERIMENTALLY ACIDIFIED WISCONSIN LAKE1

ABSTRACT: A study of concentrations and distribution of major and trace elements in surficial bottom sediments of Little Rock Lake in northern Wisconsin included examination of spatial variation and grain‐size effects. No significant differences with respect to metal distribution in sediments were observed between the two basins of the lake, despite the experimental acidification of one of the basins from pH 6.1 to 4.6. The concentrations of most elements in the lake sediments were generally similar to soil concentrations in the area and were well below sediment quality criteria. Two exceptions were lead and zinc, whose concentrations in July 1990 exceeded the criteria of 50 μg/g and 100 μg/g, respectively, in both littoral and pelagic sediments. Concentrations of some elements, particularly Cu, Pb, and Zn, increased along transects from nearshore to midlake, following a similar gradient of sedimentary organic carbon. In contrast, Mn, Fe, and alkali/alkaline‐earth elements were at maximum concentrations in nearshore sediments. These elements are less likely to partition to organic particles, and their distribution is more dependent on mineralogical composition, grain size, and other factors. Element concentrations varied among different sediment grain‐size fractions, although a simple inverse relation to grain size was not observed. Fe, Mn, Pb, and Zn were more concentrated in a grain‐size range 20–60 tm than in either the very fine or the coarse fractions, possibly because of the aggregation of smaller particles cemented together by organic and Fe/Mn hydrous‐oxide coatings.

Aspects of delayed harvest of ‘Hass’ avocado (Persea americanaMill.) fruit in a cool subtropical climate. II. Fruit size, yield, phenology and whole-tree starch cycling

SummaryWhen avocado fruit of the late maturing ‘Hass’ were tree-stored until November (early summer) in the cool, mesic, subtropical Natal midlands, fruit size at a warmer site increased with most fruit of count 18 (211 to 235 g) in July and count 14 (266 to 305 g) in November. This compared with the majority of fruit at a cooler site averaging count 16 (236 to 265 g) in August and count 14 in November. Results also showed that late hanging did not necessarily result in lower yields of the following season‘s crop. In fact where fruit were left to hang late, high yields were recorded in the third consecutive year of the trial. Annual average trunk bark starch concentrations, sampled monthly, although significantly higher in July (early) harvested trees (ca. 4.8%) were not depressed much in trees harvested in August, September, October and November (ca. 4.1%). In addition, there were no significant differences in annual average trunk bark starch concentrations from August to November. The harvest by month interactions showed that although starch concentrations in July harvested trees reached the highest peaks (ca. 12%) they subsequently dropped to the lowest troughs (ca. 2%) indicating that starch was probably allocated to vegetative growth in preference to the following season‘s crop. These results suggest that under good management and the experimental conditions of this study, late hanging of ‘Hass’ fruit may be practised without a significant depression of tree vigour.

BORON AFFECTS LOWBUSH BLUEBERRY FRUIT SET AND YIELD

Five lowbush blueberry (Vaccinium Angustifolium Ait.) clones with leaf tissue boron levels below 20 ppm were selected in a commercial lowbush blueberry field in Washington County, Maine. Four 2.4 M2 treatment plots established on each clone received a foliar spray of Solubor at 0, 200, 400 or 600 ppm boron in September. The terminal 3.8 cm of stem, sampled in November, had increased concentrations of boron with increasing rates of boron application. Boron sprays also increased boron leaf tissue concentrations in July of the crop year. Ten stems with four flower buds were tagged in each treatment plot to determine the effect of boron treatments on fruit set and berry size. Fruit set was the same for each bud, but the number of blossoms and fruit per bud was greater on buds below the terminal. Yield increased in response to boron application up to 400 ppm, due to increases in fruit set, berry number and berry size of three of the five clones.

Supplemental corn grain for steers grazing native rangeland during summer.

Effects of supplemental corn grain on forage OM intake (FOMI), digesta kinetics, ruminal fermentation patterns, in vitro OM digestibility (IVOMD), and in situ OM digestion were examined in steers grazing summer blue grama rangeland in northeastern New Mexico during July and August 1988. Sixteen ruminally cannulated steers (average BW 507 kg) were allotted to four treatments and individually fed whole-shelled corn at 0, .2, .4, and .6% of BW in a complete random design with repeated measurements over time. Forage OMI decreased linearly (P = .02) with increasing levels of supplemental corn; however, a tendency toward greater FOMI, as well as faster particulate and fluid passage, was observed when corn was fed at .2% of BW compared with 0, .4, or .6% of BW. Molar proportions of butyrate increased (P less than .10) but molar proportions of acetate and propionate, ruminal pH, and total VFA concentration did not change (P greater than .10) with added corn. Added corn linearly decreased (P less than .10) ruminal ammonia N concentrations in July, but patterns were inconsistent in August. A cubic response (P less than .05) for in situ OM disappearance with added corn was noted after 24, 72, and 96 h of incubation. Supplemental whole corn fed at .2% of BW had no detrimental effects and tended to increase FOMI. However, supplemental corn fed at .4 or .6% of BW decreased FOMI compared with 0 or .2% of BW.

Implications of AAOE observations for proposed chemical explanations of the seasonal and interannual behavior of Antarctic ozone

A number of numerical experiments using different assumptions on the initial odd nitrogen content and the efficiencies and durations of heterogeneous reactions is selected based on the simulations of the observed trace gas concentrations during the Airborne Antarctic Ozone Experiment (AAOE) in 1987 (Rodriguez et al., this issue). The model is used to calculate the seasonal behavior of O3 in 1987 and its possible interannual variations as the chlorine content of the atmosphere increases from 1 to 6 ppbv. The seasonal behavior in 1987 is compared with the total ozone mapping spectrometer (TOMS) and AAOE data. In all the cases considered, the catalytic cycle associated with the formation and photolysis of Cl2O2 could account for more than half of the photochemical removal of O3 within the Antarctic vortex through mid‐September. The reaction of BrO with ClO, which accounts for 15–20% of the removal in the same period, tends to play a more important role toward the end of September, when the concentration of ClO is expected to decrease. The detailed behavior of the calculated O3 depends on the assumptions for the spatial and temporal extent of denitrification, the initial concentrations of odd nitrogen species sequestered in the vortex in July, and the efficiencies and durations of the heterogeneous reactions in the months that follow. Additional observations of ClO, odd nitrogen species, and O3 similar to those obtained in the campaign covering the period in July and October will be useful in providing additional constraints to narrow down the possibilities. There is no simple relationship between the increase in chlorine level and the interannual decrease in Antarctic O3. It is difficult to explain both the 40% decrease in October mean O3 within the hole since 1979 and the much slower decrease prior to the mid‐1970s without invoking effects from interannual variations of heterogeneous activities and initial odd nitrogen concentrations in July. Such effects must be isolated before the observed trends in the Antarctic O3 hole in the past 8 years can be used to predict future behavior of O3 based solely on projected increase in the chlorine content of the atmosphere.

Foliar nutrient status in relation to sugar maple dieback and decline in the Quebec Appalachians

Forty-five mature sugar maple (Acersaccharum Marsh.) stands growing on soils associated with a wide range of geological formations in the Quebec Appalachians were sampled in both early to mid-July and mid- to late August 1985. The average level of forest decline, as indicated by foliage density, was 15%, ranging from 1 to 69%. The foliar concentrations of N, P, Ca, Mg, Mn, Fe, Zn, and B in July were generally adequate while K concentrations were &lt;0.55% in nine sites (20% of the sites). Mean K concentrations in July and August were 0.68% and 0.62%, respectively, with only one value in excess of 0.90% in July, which is below most K concentrations reported in the literature for sugar maple. Results are presented for two distinct regions within the study area. Most stands with foliar K levels less than 0.55% in July exhibited high levels of decline (15–69%) while the majority of stands with K in excess of this concentration showed low levels of decline. These data suggest that K deficiency (sometimes accompanied by an acute P deficiency) influences the integrity of forest ecosystems and may play a significant role in the decline of the deciduous forest in the Quebec Appalachians.