RESUMO
Mangroves and saltmarshes are biogeochemical hotspots storing carbon in sediments and in the ocean following lateral carbon export (outwelling). Coastal seawater pH is modified by both uptake of anthropogenic carbon dioxide and natural biogeochemical processes, e.g., wetland inputs. Here, we investigate how mangroves and saltmarshes influence coastal carbonate chemistry and quantify the contribution of alkalinity and dissolved inorganic carbon (DIC) outwelling to blue carbon budgets. Observations from 45 mangroves and 16 saltmarshes worldwide revealed that >70% of intertidal wetlands export more DIC than alkalinity, potentially decreasing the pH of coastal waters. Porewater-derived DIC outwelling (81 ± 47 mmol m-2 d-1 in mangroves and 57 ± 104 mmol m-2 d-1 in saltmarshes) was the major term in blue carbon budgets. However, substantial amounts of fixed carbon remain unaccounted for. Concurrently, alkalinity outwelling was similar or higher than sediment carbon burial and is therefore a significant but often overlooked carbon sequestration mechanism.
RESUMO
Short-term increases in air pollution levels are linked to large adverse effects on health and productivity. However, existing regulatory monitoring systems lack the spatial or temporal resolution needed to capture localized events. This study uses a dense network of over 100 sensors, deployed across the city of Chicago, Illinois, to capture the spread of smoke from short-term structural fire events. Examining all large structural fires that occurred in the city over a year (N = 21), we characterize differences in PM[Formula: see text] concentrations downwind versus upwind of the fires. On average, we observed increases of up to 10.7 [Formula: see text]g/m[Formula: see text] (95% CI 5.7-15.7) for sensors within 2 km and up to 7.7 [Formula: see text]g/m[Formula: see text] (95% CI 3.4-12.0) for sensors 2-5 km downwind of fires. Statistically significant elevated concentrations were evident as far as 5 km downwind of the location of the fire and persisted over approximately 2 h on average. This work shows how low-cost sensors can provide insight on local and short-term pollution events, enabling regulators to provide timely warnings to vulnerable populations.
RESUMO
Understanding the different scales of temporal variability is crucial to improve the knowledge of the biogeochemical processes in the land-ocean interface. In this study, we evaluated the role of continental runoff and intrusion of oceanic water masses in the trophic state of the Bay of Santa Catarina Island (BSCI) over the last three decades (1993-2019) by using multiple biogeochemical and eutrophication assessment tools. The sub-watersheds of BSCI showed high concentrations of nutrients, fecal coliform and chlorophyll-a, directly correlated to the number of inhabitants. Worst-case scenarios were found in summer and fall seasons due to sewage inputs caused by mass tourism and the inefficiency or even absence of treatment systems, boosted by strong rainfall. The intrusion of the South Atlantic Central Water and the Plata Plume Water into the BSCI favored autotrophy in the summer and heterotrophy in the winter, coupled with low and high residence time, respectively. El Niño events enhanced rainfall and continental runoff, exporting elevated nutrients and phytoplankton biomass loads from the eutrophic rivers to the continental shelf. The pattern reverses during La Niña, when chlorophyll and nutrient peaks were detected inside the bay. Eutrophication evaluation indicated that the trophic state oscillated from moderate to high and that these conditions tend to remain the same in future scenarios due to the moderate residence time of the water, anthropogenic pressures, periodic algal blooms and the intrusion of nutrient-rich oceanic water masses. Management actions, such as the improvement of the wastewater treatment system and wetlands restoration, are needed in order to mitigate eutrophication and the loss of ecosystem services and functions.
