Long and short-term exposure to particulate matter (PM) are linked to adverse heath endpoints. Evidence indicates that PM composition such as metals and organic carbon (OC) might drive the health effects. As airborne pollutants show significant intracity spatiotemporal variation, mobile sampling and distributed monitors are utilized to capture the variation pattern. The measurements are then fed to develop models to better characterize the relationship between exposure and health outcomes. Two sampling campaigns were conducted. One was sole mobile sampling in 2013 summer and winter in Pittsburgh, PA. Thirty-six sites were chosen based on three stratification variables: traffic density, proximity to point sources, and elevation. The other one was hybrid sampling network, incorporating a mobile sampling platform, 15 distributed monitors, and a supersite. We designed two case studies (transect and downtown), selected 14 neighborhoods (~1 km2), and conducted sampling in 2016 summer/fall and winter. Spatial variation of PM2.5 mass and composition was studied in the 2013 campaign. X-ray fluorescence (XRF) was used to analyze concentrations of 26 elements: Na, Mg, Al, Si, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Zr, Cd, Sb, and Pb. Trace elements had a broad range of concentrations from 0 to 300 ng/m3. Comparison of data from mobile sampling with stationary monitors showed reasonable agreement. We developed Land use regression (LUR) models to describe spatial variation of PM2.5, Si, S, Cl, K, Ca, Ti, Cr, Fe, Cu, and Zn. Independent variables included traffic influence, land-use type, and facility emissions. Models had an average R2 of 0.57 (SD = 0.16). Traffic related variables explained the most variability with an average R2 contribution of 0.20 (SD = 0.20). Overall, these results demonstrated significant intra-urban spatial variability of fine particle composition. Spatial variation of OC was based on the 2013 campaign as well. We collected organic carbon (OC) on quartz filters, quantified different OC components with thermaloptical analysis, and grouped them based on volatility in decreasing order (OC1, OC2, OC3, OC4, and pyrolyzed carbon (PC)). We compared our ambient OC concentrations (both gas and particle phase) to similar measurements from vehicle dynamometer tests, cooking emissions, biomass burning emissions, and a highway traffic tunnel. OC2 and OC3 loading on ambient filters showed a strong correlation with primary emissions while OC4 and PC were more spatially homogenous. While we tested our hypothesis of OC2 and OC3 as markers of fresh source exposure for Pittsburgh, the relationship seemed to hold at a national level. Land use regression (LUR) models were developed for the OC fractions, and models had an average R2 of 0.64 (SD = 0.09). We demonstrate that OC2 and OC3 can be useful markers for fresh emissions, OC4 is a secondary OC indicator, and PC represents both biomass burning and secondary aerosol. People with higher OC exposure are likely inhaling more fresh OC2 and OC3, since secondary OC4 and PC varies much less drastically in space or with local primary sources. With the 2016 hybrid sampling campaign, we addressed the intracity exposure patterns, as they could be more complex than intercity ones because of local traffic, restaurants, land use, and point sources. This network studied a wide range of pollutants (CO2, CO, NO2, PM1 mass and composition, and particle number PN). Mobile measurements and distributed monitors show good agreement. PN hotspots are strongly associated with restaurants and highway traffic. PN at sites with large local source impacts tends to have larger diurnal variation than daily variation, while CO in downtown center shows the opposite trend. PN exhibits the largest spatial and temporal variations. Spatial variation is generally larger than temporal variation among all five pollutants (CO2, NO2, CO, PN, and PM1). These findings provide quantitative comparison between spatial and temporal variation in different scales, and support the theoretical validity of developing long-term exposure models from short-term mobile measurement. A combined sampling network with mobile and distributed monitor could prove more valuable in studying intracity air pollution. In the 2016 hybrid sampling campaign, we also studied spatial variability of air pollution in the vicinity of monitors. Monitoring network is essential for protecting public health, though evaluation is needed to assess spatial representativeness of monitors in different environments. Mobile sampling was conducted repeatedly around 15 distributed monitors. Substantial short-range spatial variability was observed. Spatial variation was consistently larger than temporal variation for NO2 and CO at different sites. Ultrafine particles were highly dynamic both in space and time. PM1 was less spatially and temporally variable. Urban locations had more frequent episodic source plume events compared with background sites. Using a single monitor measurement to represent surrounding ~1 km2 areas could introduce an average daily exposure misclassification of 46 ppb (SD = 26) for CO (30% of regional background), 3 ppb (SD = 2) for NO2 (43% of background), 4007 #/cm3 (SD = 1909) for ultrafine particle number (64% of background), and 1.2 μg/m3 (SD = 1.0) for PM1 (13% of background). Exposure differences showed fair correlation with traditional land use covariates such as traffic and restaurant density, and the magnitude of misclassification could be even bigger for urban neighborhoods.

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Entre les fleuves Amazone et Orénoque, la frange côtière atlantique de l’Amérique du Sud (1500 km) est considérée comme la plus vaseuse au monde, conséquence des apports de sédiments en suspension de l’Amazone. Malgré la forte variabilité et l’instabilité de ces vasières uniques au monde, elles apparaissent comme des écosystèmes très productifs et sont des habitats clés dans l’accomplissement du cycle de vie des espèces de poissons et d’oiseaux qui les exploitent. Cependant, les connaissances sur les communautés biologiques qui y sont associées restent au niveau exploratoire. Ce travail de thèse vise donc à décrire la structure de l’endofaune benthique intertidale des vasières guyanaises et à définir son fonctionnement dans des environnements vaseux tropicaux très instables. Comme prévu, la forte instabilité des sédiments a entraîné une très faible diversité des assemblages de la macrofaune et de la méiofaune. Néanmoins, les communautés benthiques des vasières guyanaises ont montré une abondance remarquablement élevée avec la dominance d'espèces opportunistes de petites tailles. 39 taxons de la macrofaune ont été trouvés tandis que la méiofaune était moins diversifiée avec la présence de 34 taxons. Le tanaidacée Halmyrapseudes spaansi et le polychète Sigambra grubii sont les deux espèces de macrofaune les plus abondantes, largement réparties le long de la côte guyanaise. De même, le nématode Pseudochromadora spp., suceur d’épistrate, et Halomonhystera sp. 1 (non deposit feeders) étaient les deux espèces de méiofaune les plus abondantes sur chacune des stations. La distribution des communautés benthiques sont spécifiques aux sites d’étude et varie saisonnièrement. Les assemblages en zone estuarienne (Sinnamary) étaient plus diversifiées que dans la zone de vasière nue (Awala), alors que les abondances des communautés benthiques étaient toujours plus élevées en saison humide qu’en saison sèche. Les facteurs abiotiques et biotiques ont influencé significativement les communautés benthiques. Néanmoins, les changements dans la structure de la communauté benthique induits par la disponibilité des sources alimentaires (chl a) et la pression de prédation étaient tout aussi importantes que les variations des assemblages imposées par les paramètres abiotiques (teneur en eau, salinité ...). En particulier, une forte corrélation a été trouvée entre la méiofaune et le microphytobenthos. Les mesures isotopiques de différents compartiments des vasières ont non seulement révélé le rôle central du microphytobenthos dans la composition du régime alimentaire de la méiofaune, mais ont également montré l'importance écologique de la méiofaune comme principale source de nourriture pour les petits oiseaux limicoles et les poissons côtiers. La méiofaune et le microphytobenthos rentrent dans le régime alimentaire de trois poissons côtiers en grande proportion, alors que les oiseaux limicoles migrateurs présentaient une plus grande diversité de proies. Cependant, la contribution relative des tanaidacées dans le régime alimentaire des oiseaux limicoles était étonnamment faible. Le travail de thèse a permis d'améliorer notre compréhension de la structure de l’endofaune benthique intertidale des vasières guyanaises et de définir son fonctionnement dans des environnements vaseux tropicaux très instables. Ce travail a permis de construire, pour la première fois, un modèle conceptuel de réseau trophique des vasières intertidales mobiles guyanaises. / Locating between the Amazon and Orinoco Rivers, the 1500 km-long Atlantic coastline of South America are considered as the muddiest areas in the world due to the large discharge of suspended sediment from the Amazon. Despite the extreme morphodynamics of these ecosystems, the Guianas mudflats are important feeding zones for many shorebirds and fish. However, the state of knowledge on benthic organisms associated with these highly unstable environments is still at an exploratory stage. This study, therefore, aims to describe the structure and dynamics of the intertidal benthic infauna in the Guianas mudflats and to define its functioning in such highly unstable tropical muddy environments. As expected, the high instability of the sediment resulted in very low diversity of both macrofauna and meiofauna assemblages. Nonetheless, the infauna communities of the Guianas mudflats showed remarkably high abundance with the predominance of small-sized opportunistic species. A total of 39 operational taxonomic units of macrofauna was recorded while meiofauna was less diverse with the occurrence of 34 taxa. The tanaid Halmyrapseudes spaansi and the polychaeta Sigambra grubii are the two most abundant macrofauna species, which widely distributed along the Guianas coast. Likewise, the nematodes epistrate feeder Pseudochromadora spp. and non-deposit feeders Halomonhystera sp. 1 were the principal components of meiofauna communities in every station. The distribution patterns of the infauna were both site-specific and seasonal variation. The assemblages in estuarine habitat were more diverse than in the bare mudflat habitat, while infauna abundances in the WS were always higher than in the DS. Both abiotic and biotic factors significantly influenced the benthic communities. Nevertheless, the changes in benthic community structure induced by food source availability (chl a) and predation pressure were more prominent than the assemblage variations imposed by abiotic parameters (mud content, salinity…). Particularly, the tight coupling between meiofauna and MPB was observed in both distribution patterns and trophic structures. The isotopic measurements of different intertidal compartments not only revealed the pivotal role of MPB on structuring meiofaunal coummunities, but also indicated the ecological importance of meiofauna as the main food source for the small shorebirds and coastal fish. Meiofauna and MPB entered the diet of three coastal fish in great proportion, whereas the migrating shorebirds showed a wider diet breadth. The isotopic ratios were perfectly matched with the feeding guilds assigned by morphological features. However, the relative contribution of tanaids to the top epibenthic predators were surprisingly lower than expected. The thesis has increased our understanding of the Guianas infauna communities, and revealed for the first time a conceptual food web model of these unique intertidal mudflats.

In this investigation we analyzed the spatiotemporal variation of ecosystem service values (ESVs) and its correlation with numerous environmental factors (EFs) for the karst region of Northwest Guangxi, China, from 1985 to 2005 using remote sensing, geographic information systems (GIS) and statistical techniques. The results indicate that historically ESVs for this karst region decreased from 1985 (109.652 billion Yuan) to 1990 (88.789 billion Yuan) and then increased at the turn of the twenty-first century. However, the ESVs in both 2000 (103.384 billion Yuan) and 2005 (106.257 billion Yuan) never achieved the level recorded in 1985. The total of nutrient cycling, organic production and gas regulation combined were 72.69, 64.57, 70.18 and 72.10% of ESVs in 1985, 1990, 2000 and 2005, respectively. In contrast, the ESVs of water conservation, soil reservation, recreation and culture were determined to be relatively low contributing only 17.44, 23.82, 19.26 and 24.76% of total ESVs, respectively, during these four years. With regards to the spatial distribution of ESVs, larger values were recorded in the west and smaller ones recorded in the east. The most significant factors that were deemed to influence ESVs are annual rainfall, per capita cropland, slope and vegetation coverage. Annual rainfall and slope exert a negative force, whereas per capita cropland and vegetation coverage exert a positive force on ESVs. The results of the study would suggest that ecosystem conditions of this important karst region have been improved as the result of the implementation of rocky desertification control policies.

Understanding and modeling microbial responses and feedbacks to climate change is hampered by a lack of a framework in the pelagic environment by which to link local mechanism to large scale patterns. Where terrestrial ecology draws from landscape theory and practice to address issues of scale, the pelagic seascape concept is still in its infancy. We have applied the patch mosaic paradigm of landscape ecology to the study of the seasonal and interannual variability of the North Pacific to facilitate comparative analysis between pelagic ecosystems and provide spatiotemporal context for eulerian time-series studies. Using multivariate, 13-year climatologies of sea surface temperature, photosynthetically active radiation, and chlorophyll a derived from remote sensing observations, we classified hierarchical seascapes at monthly and interannual scales. These dynamic, objectively-determined seascapes offer improved hydrographic coherence relative to oceanic regions with subjectively defined and static boundaries (Chapter 2) and represent unique biogeochemical functioning (Chapter 2) and microbial communities (Chapter3). Furthermore they provide consilience between satellite studies and in situ observations (Chapter 4) and allow for objective comparison of ecosystem forcing (Chapters, 4 and 5). In Chapter 2, we rigorously tested the assumption that satellite-derived seascapes describe regions of biogeochemical coherence. The seasonal cycle of the North Pacific was characterized at three levels of spatiotemporal hierarchy and broader relevance of monthly ���resolved seascapes was assessed through analysis of variance (ANOVA) and multiple linear regression (MLR) analyses of nutrient, primary productivity, and pCO��� data. Distinct nutrient and primary productivity regimes were well-characterized in the coarsest two levels of hierarchy (ANOVA, R�� = 0.5-0.7). Finer scale partitioning was more relevant for pCO���. MLR analyses revealed differential forcing on pCO��� across seascapes and hierarchical levels and a 33 % reduction in mean model error with increased partitioning (from 18.5 ��atm to 12.0 ��atm pCO���). In Chapter 3 we verified the seascapes with in situ collections of microbial abundance and structure. Flow cytometry data was collected from two long term time series and several cruises spanning thousand kilometers of the NE Pacific; these data allowed us to quantify spatiotemporal patterns. In addition, multiple response permutation analysis revealed differences in community structure across discrete seascapes, in terms of both absolute and relative abundances. Principal component analysis of the assemblage supported seascape divisions and revealed structure along environmental gradients with strong associations with chlorophyll a and sea surface temperature and, to a lesser extent, with mixed layer depth and mean photosynthetically active radiation in the mixed layer. Differences of assemblage structure between seascapes and strength of environmental forcing were strong in the subarctic and transition zones, but less pronounced in the subtropics, suggesting satellite-detected changes in bulk properties that may be associated with local physiology or interannual shifts in seascape boundaries. Based on the work presented in Chapter 4, we discovered that interannual shifts in the boundaries of a transition seascape and two distinct oligotrophic subtropical seascapes affect the variability observed at benchmark time series Station ALOHA; the latter two seascapes oscillate in their contributions to the expansion of the entire subtropics. On interannual scales, in situ phytoplankton abundance (as measured by chl-a), net primary productivity (NPP), and the relative abundance of eukaryotic phytoplankton and Synechococcus sp. increased during periods of encroachment by the transition seascape. Conversely, the relative abundance of Prochlorococcus increased and chl ���a and NPP decreased when the highly oligotrophic seascape encroached on Station ALOHA. The dynamic range (~6 million km��) of subtropical expansion is born almost entirely by the transition zone - resulting in a transfer of ~1.2 Pg of total primary C production between a system primed for export production and one dominated by the microbial loop. In Chapter 5, we investigated multiple factors that contribute to the effectiveness of the biological pump in the transition seascape. Near-continuous measurements of net primary production (NPP), net community production (NCP) and several ecophysiological variables were collected in across subarctic, transition, and subtropical seascapes of the Northeast Pacific during August and September of 2008. Mesoscale processes and shifts in community structure contributed to high export efficiency in the subtropical seascape; the convergence of assemblage structure, high biomass, moderate NPP: NCP and high NCP contributed to biologically mediated air-sea exchange in the transition seascape. Furthermore, NPP and NCP were strongly spatially coupled in both the transition (r[subscript 1, 39]=0.70; p<0.0001) and subtropical seascapes (r[subscript 1, 45]= 0.68, p<0.0001), suggesting the possibility for empirical modeling efforts. This dissertation provides a first step to characterize the seascape variability in the NE Pacific and to understand the modulation of primary and export production in a critical transition region. The multivariate seascape approach described here provides spatiotemporal context for in situ studies and allows objective comparisons of systems' responses to climatic forcing. An integrated ocean observing system will require insight from in situ observations and experiments, ecosystem models, and satellite remote sensing. The results highlighted in this dissertation suggest that the pelagic seascape framework, through its capacity to scale both context and mechanism, may serve as an important and unifying component of such an observing system. / Graduation date: 2013