Biogeochemical Impacts of a Black Carbon Wet Deposition Event in Halong Bay, Vietnam

Abstract

Black carbon (BC) is emitted to the atmosphere during biomass, biofuel, and fossil fuel combustion, and leaves the atmosphere via dry or wet deposition on land and on the ocean. On a global scale, wet deposition accounts for about 80% of the total atmospheric BC inputs to the ocean. The input of BC particles to the ocean can enrich surface waters with carbon and associated elements, and owing to high porosity and surface-active properties, BC can alter biogeochemical cycles by sorbing dissolved compounds and promoting aggregation. The rain-mediated input of BC to the ocean and its consequences on nutrient concentrations and particle dynamics were studied in Halong Bay, Vietnam, during a 24-h cycle impacted by short and heavy rainfall events. This study suggests that once introduced in the surface ocean via wet deposition, BC sorbs dissolved organic matter (DOM) and stimulates aggregation processes. The observed wet deposition events were characterized by sudden and pulsed inputs of BC particles that created a thin layer of sinking surface-active aggregates, acting as a net-like scavenger for DOM, nutrients (especially phosphate), and small particles. In addition, the wet deposition events coincided with an enrichment of nutrients in the surface microlayer, with an excess input of nitrogen relative to phosphorus leading to an increase of the molar N:P ratio from 24:1 to 37:1. In the underlying water, the molar N:P ratio also increased (i.e., from 39:1 to 64:1), and this can be attributed to the preferential scavenging of dissolved P-compounds on sinking BC-aggregates.

Evidence for Fossil Fuel PM1 Accumulation in Marine Biota

“…In a wet deposition study in Halong Bay, Vietnam, the input of atmospheric BC to the ocean resulted in the sorption of various compounds, including dissolved nitrogen and phosphorus from seawater. 15 Such high nutrient-containing particles may be incorporated into marine animals. This observation is supported by our PM 1 data.…”

“…Additionally, in contrast to previous investigations on atmospheric PM, high P levels were always detected in our aquatic biological samples (Table , Figure , and Table S1). In a wet deposition study in Halong Bay, Vietnam, the input of atmospheric BC to the ocean resulted in the sorption of various compounds, including dissolved nitrogen and phosphorus from seawater . Such high nutrient-containing particles may be incorporated into marine animals.…”

“…It was also reported that, near an oil-fired power plant area, the soot deposition favored the growth of particle-attached bacteria but not viral and free living ones . In a wet deposition study in Halong Bay, Vietnam, BC particles in the ocean were also found to adsorb surrounding dissolved organic matter, nutrients (such as N and P), and small particles . In aquatic animals, the adverse effects of atmospheric PM 2.5 were evaluated in the laboratory with the nematode Caenorhabditis elegans, the freshwater snail Parafossarulus striatulus, the rotifer Brachionus calyciflorus, and generated inferior locomotion, feeding, growth, fertility, survival, etc.…”

Utilization of Soot and 210 Po-210 Pb Disequilibria to Constrain Particulate Organic Carbon Fluxes in the Northeastern South China Sea

“…Indeed, the countries rounding the SCS contributed more than one third of the global BC emissions (Bond et al, 2013). Wet precipitation delivers large amounts of BC to the SCS (Mari et al, 2019). In addition, previous studies have shown that the higher DBC concentrations in the upper 100 m of the SCS (avg.…”

Influence of atmospheric deposition on biogeochemical cycles in an oligotrophic ocean system

“…Free viruses, richer in P than N relative to hprok, could adsorb, like DOM, onto dust particles and constitute a P export source. Indeed, free viruses adsorb onto black carbon particles, possibly reducing viral infection (Mari et al, 2019;Malits et al, 2015). However, particle quality is a determining factor for DOM or microbial attachment, and what has been shown for black carbon particles is not necessarily true for dust particles.…”