Abstract
Abstract. Atmospheric nutrients have recently gained considerable attention as a significant additional source of new nitrogen (N) and phosphorus (P) loading to the ocean. The effect of atmospheric macro nutrients on marine productivity depends on the biological availability of both inorganic and organic N and P forms. During October 2006, the regional smoke haze episodes in Southeast Asia (SEA) that resulted from uncontrolled forest and peat fires in Sumatra and Borneo blanketed large parts of the region. In this work, we determined the chemical composition of nutrients in aerosols and rainwater during hazy and non-hazy days to assess their impacts on aquatic ecosystem in SEA for the first time. We compared atmospheric dry and wet deposition of N and P species in aerosol and rainwater in Singapore between hazy and non-hazy days. Air mass back trajectories showed that large-scale forest and peat fires in Sumatra and Kalimantan were a significant source of atmospheric nutrients to aquatic environments in Singapore and SEA region on hazy days. It was observed that the average concentrations of nutrients increased approximately by a factor of 3 to 8 on hazy days when compared with non-hazy days. The estimated mean dry and wet atmospheric fluxes (mg/m2/day) of total nitrogen (TN) were 12.72 ± 2.12 and 2.49 ± 1.29 during non-hazy days and 132.86 ± 38.39 and 29.43 ± 10.75 during hazy days; the uncertainty estimates are represented as 1 standard deviation (1σ) here and throughout the text. The estimated mean dry and wet deposition fluxes (mg/m2/day) of total phosphorous (TP) were 0.82 ± 0.23 and 0.13 ± 0.03 for non-hazy days and 7.89 ± 0.80 and 1.56 ± 0.65 for hazy days. The occurrences of higher concentrations of nutrients from atmospheric deposition during smoke haze episodes may have adverse consequences on receiving aquatic ecosystems with cascading impacts on water quality.
Highlights
Enrichment of nutrients in aquatic ecosystems can lead to undesirable effects including algal blooms and depletion of oxygen in the water
Vd at a particular vertical height was calculated as the inverse of the sum of a number of resistances (Seinfeld and Pandis, 2006) using the following equation: Vd = Ra + Rb + RaRbvs + vs where vs is the gravitational settling velocity (Seinfeld and Pandis, 2006), Ra is aerodynamic resistance refers to turbulent transport from the free atmosphere down to the receptor surface (Ra=9/[uσθ2], which is a function of wind speed, u and standard deviation of wind speed, σθ, Yamartino, 1984; Turner, 1986) and Rb is quasi-laminar layer resistance
The air quality categories based on PSI or API and the general health effects associated with different categories of air quality are summarized as follows: PSI or API up to 50:Good; 51–100:Moderate; 101–200:Unhealthy; 201–300:Very Unhealthy; >300:Hazardous
Summary
Enrichment of nutrients in aquatic ecosystems can lead to undesirable effects including algal blooms and depletion of oxygen in the water. Estimate DAD and WAD fluxes of N and P species during hazy and non-hazy days to the coastal waters in Singapore. There has been no systema3t1ic study to estimate the atmospheric deposition of nutrients in SEA despite recurring forest and peat fires in the region. Water quality models with the capability of simulating such scenarios in terms of shifts in the N:P ratio can provide insights into the effects of nutrient deposition on aquatic ecosystems. The present study is focused on quantification of water soluble nutrients (N and P species only) resulting from DAD (aerosol particulates) and WAD (rainwater) in SEA for the first time.
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