Search

The Indo-Gangetic Plain (IGP) region of India faces some of the most severe air pollution problems on Earth that threaten human health, food security, ecosystems, environmental sustainability, and the climate. The aim of this study is to identify and characterize the sources of key short-lived climate pollutants (SLCPs) – black carbon (BC), brown carbon (BrC), and ozone (O3) – as well as other pollutants [carbon monoxide (CO) and nitrogen oxides NOX= NO and NO2], and interlinked atmospheric processes of their formation and transformation at our long-term air pollution monitoring station in a remote rural IGP site, the Indo-Gangetic Plains Centre for Air Research and Education (IGP-CARE). Because of its location, measurements acquired at IGP-CARE provide otherwise new information on the key SLCPs in the IGP region at a remote and rural location. The year-long measurement data at this remote site provided new insights into the variability of SLCP concentration and interlinked atmospheric processes that affect air quality in the rural IGP region. Thirteen episodic events (E1–E13) of elevated BC and BrC concentrations were identified, which can largely be attributed to the local biomass burning activities in the neighboring rural communities. It is suggested that high concentrations of BrC were mostly primary in nature and thought to be co-emitted with BC from biomass burning. Also, secondary pollutant tropospheric O3showed elevated concentration. O3peaks were mostly attributed to local ozone formation. Nevertheless, on several occasions, O3emission was also attributed to regional urban areas. This study's most important finding is that BrC concentrations were relatively high throughout the year with very pronounced diurnal variation with distinct morning and evening peaks in general and a minimum at around noon time; this is hypothesized to be associated with daytime photochemical processes. Analyses using a conditional bivariate probability function (CBPF) and potential source contribution function (PSCF) suggest that regional sources likely affected the local concentrations of SLCPs. These results partly explain the high concentrations and spatial distributions of SLCPs at the local and regional scales at the IGP-CARE site in winter and autumn. In contrast, in the summer and monsoon seasons, strong convection likely favored the dilution of pollutants.

Die Konzentration von Ozon (O3) oberhalb und innerhalb der Vegetationsschicht von Gerste und Weizen wurde gemessen. Im Vergleich zur Konzentration in 1,1 m Höhe über dem Boden (0,1 m über der 1 m hohen Vegetationsschicht) war die Konzentration innerhalb der Vegetationsschicht um 20 % während des Tages bzw. 40 % nachts reduziert. Das galt sowohl für Gerste als auch für Weizen. Die Änderung in der OzonReduktion innerhalb des Pflanzenbestandes während der Stunden mit den höchsten Windgeschwindigkeiten (11:00-16:00 Uhr) wurde zum Teil durch den Effekt des Wasserdampfdruckdefizites auf die Stomata-Öffnung erklärt. Die Konzentrationsgradienten von Stickstoffdioxid (NO2) oberhalb und innerhalb der Vegetation waren schwächer aber ähnlich wie die von O3. Die Messungen zeigten eine Emission von Stickstoffmonoxid (NO) an. Während des Tages hatte die CO2-Konzentration ein lokales Minimum im oberen Bereich der Vegetationsschicht, was die Photosynthese-Aktivität von dem nicht verwelkten, oberen Teil der Vegetationsschicht widerspiegelt. Während der Nacht sind sehr hohe CO2-Konzentrationen innerhalb und direkt oberhalb der Vegetationsschicht, als Ergebnis der Kombination von Respiration und beschränkter Luftdurchmischung gemessen worden. In Open-Top-Kammern wurden keine O3-Gradienten, weder horizontal oberhalb der Vegetationsschicht, noch senkrecht innerhalb der Vegetationsschicht beobachtet.

Gas exchange was measured from 1 month before the onset of anthesis until the end of grain filling in field-grown spring wheat, Triticum aestivumL., cv. Vinjett, in southern Sweden. Two gsmodels were parameterised using these data: one Jarvis-type multiplicative gsmodel (J-model), and one combined stomatal-photosynthesis model (L-model). In addition, the multiplicative gsmodel parameterisation for wheat used within the European Monitoring and Evaluation Programme (EMEP-model) was tested and evaluated. The J-model performed well (R2=0.77), with no systematic pattern of the residuals plotted against the driving variables. The L-model explained a larger proportion of the variation in gsdata when observations of Anwere used as input data (R2=0.71) compared to when Anwas modelled (R2=0.53). In both cases there was a systematic model failure, with gsbeing over- and underestimated before and after anthesis, respectively. This pattern was caused by the non-parallel changes in gsand Anduring plant phenological development, with Anboth peaking and starting to decline earlier as compared to gs. The EMEP-model accounted for 41% of the variation in gsdata, with gsbeing underestimated after anthesis. We conclude that, under the climatic conditions prevailing in southern Scandinavia, the performance of the combined stomatal-photosynthesis approach is hampered by the non-parallel changes in gsand An, and that the phenology function of the EMEP-model, having a sharp local maximum at anthesis, should be replaced by a function with a broad non-limiting period after anthesis.Gas exchange was measured from 1 month before the onset of anthesis until the end of grain filling in field-grown spring wheat, Triticum aestivumL., cv. Vinjett, in southern Sweden. Two gsmodels were parameterised using these data: one Jarvis-type multiplicative gsmodel (J-model), and one combined stomatal-photosynthesis model (L-model). In addition, the multiplicative gsmodel parameterisation for wheat used within the European Monitoring and Evaluation Programme (EMEP-model) was tested and evaluated. The J-model performed well (R2=0.77), with no systematic pattern of the residuals plotted against the driving variables. The L-model explained a larger proportion of the variation in gsdata when observations of Anwere used as input data (R2=0.71) compared to when Anwas modelled (R2=0.53). In both cases there was a systematic model failure, with gsbeing over- and underestimated before and after anthesis, respectively. This pattern was caused by the non-parallel changes in gsand Anduring plant phenological development, with Anboth peaking and starting to decline earlier as compared to gs. The EMEP-model accounted for 41% of the variation in gsdata, with gsbeing underestimated after anthesis. We conclude that, under the climatic conditions prevailing in southern Scandinavia, the performance of the combined stomatal-photosynthesis approach is hampered by the non-parallel changes in gsand An, and that the phenology function of the EMEP-model, having a sharp local maximum at anthesis, should be replaced by a function with a broad non-limiting period after anthesis.

Leaf diffusive conductance for water ( g l) and twig xylem pressure ( ψ xt) was measured in juvenile silver birch, Betula pendula, under field conditions in southern Sweden. Data from one site were used to parameterise two different multiplicative models for g l (dependent data), and measurements from another site were used to validate these models (independent data). In addition, experiments were performed in controlled environments to validate the g l response functions used in the models. The driving variables in the D-model were photosynthetic photon flux density, air temperature and water vapour pressure deficit of the air ( D a), while the DH-model also included the accumulated hours after sunrise each day with D a above a certain threshold ( H). Both models satisfactorily predicted the variation in g l in dependent as well as in independent data, and the g l response functions used were supported by the experiments in controlled environments. The DH-model was more successful in predicting g l than the D-model by accounting for the observation that g l was lower at higher H under similar weather conditions. There was a considerable variation in maximum g l during the season, as well as between the two sites. On relatively warm and dry days ψ xt rapidly declined during the morning and then stabilized around a constant value until the late afternoon, with the stomatal regulation effectively preventing ψ xt from decreasing below this value. We suggest that these models could be used to simulate the g l in juvenile birch if maximum g l is locally estimated and if the response functions are not extrapolated beyond the climate range for this study.

Saplings of one clone of Norway spruce (Picea abies) were planted in pots and exposed to charcoal filtered (CF) air, non-filtered (NF) air or NF air plus extra ozone (NF+; ambient × 1.4) in open-top chambers (OTCs). The lowest and highest ozone concentrations were combined with low phosphorus (LP) supply. Ambient air plots without OTCs, and with and without pots, were also included. A long-term study was conducted with 756 trees (3–7 years old) harvested successively over four growing seasons. Ozone had a negative impact on tree growth, both in the high phosphorus (HP) supply and in the LP treatments. The ozone-induced decrease in biomass of the whole tree (NF+ relative to CF) was approximately 5% after four seasons, irrespective of phosphorus status. The corresponding decrease in biomass caused by LP, relative to HP, was 20% whatever the ozone treatment. LP also caused a shift in the shoot to root ratio, where root growth was favoured at the expense of the shoot. A weak effect of ozone treatment on the shoot to root ratio, favouring shoot growth, was found after three seasons, but was totally surpassed by the opposite effect of LP in the fourth season. The effect of OTCs and pots is also discussed.

Data from two Swedish and one Finnish open-top chamber experiments were combined to investigate effects of ozone exposure on potato (Solanum tuberosum L.) tuber content of starch, sucrose, fructose, glucose, malic, citric and ascorbic acids. The glucose, fructose and malic acid concentrations showed strong negative correlations with ozone exposure, while citric acid, consistently increased with ozone exposure. No ozone effects could be demonstrated on starch, sucrose or ascorbic acid concentrations. It is discussed to what extent the changes found in potato tuber composition can be explained in terms of ozone effects on tuber maturity. Ozone exposure was expressed as the accumulated exposure over a cut-off concentration of 40 nmol mol−1(AOT40) and as the accumulated uptake of ozone over an ozone uptake rate threshold of 7 nmol m−2s−1(CUO 7). The difference in ability of the exposure indices to explain observed effects was small.

Eight Nordic open-top chamber experiments with field-grown spring wheat were combined to obtain relationships between ozone exposure and yield loss. Two exposure indices, AOT30 and AOT40 (AOT = accumulated exposure over threshold), were tested. Strongly significant linear regressions between relative yield and exposure were obtained with both indices. The coefficient of determination (r2) was higher and the model assumptions of linear regression were satisfied to a larger extent with AOT30 than with AOT40. The exclusion of charcoal-filtered treatments from the analysis made little difference to the regressions. The AOT30 regression model predicted larger yield loss than the AOT40 regression model, especially for the range of exposures, which is likely to occur in the Nordic countries. The protein content of the grain increased with increasing ozone exposure in all eight experiments, but to a varying degree.

Die Lufttemperatur und die relative Luftfeuchtigkeit wurden während der totalen Sonnenfinsternis am 29. März 2006 bei Side in der Türkei (N36°45.95'; E31°23.71') gemessen. Die Lufttemperatur war um 5.0°C von Anfang der Finsternis bis zur Totalität gesunken und nahm wieder mit 4.3°C nach der Totalität zu. Eine Überschätzung des Temperatur-Abfalls während der Finsternis, durch einen Strahlungseffekt an der Temperaturmessung, von ~0.5°C kann nicht ausgeschlossen werden. Die relative Luftfeuchtigkeit zeigte während der Finsternis einen umgekehrten Verlauf im Vergleich zur Lufttemperatur. Der Dampfdruck veränderte sich nur wenig und nicht systematisch mit dem Verlauf der Verfinsterung.