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Acrylic acid (AA), a short-chain fatty acid found in the ocean, is derived from the microbial cleavage of dimethylsulfoniopropionate in addition to terrestrial input. The aqueous photochemical transformation of AA in natural seawater, artificial seawater, and Milli-Q water was studied under artificial light (using a photochemical reactor) and natural light (by exposure to sunlight). A degradation study on field seawater was conducted inside and outside Jiaozhou Bay, which is located in the north of China. Kinetic studies showed that the degradation and reaction rate of AA in natural seawater were obviously higher than those in the other aqueous media under artificial and natural light, with the degradation characteristics in artificial seawater and Milli-Q water being similar. The degradation and reaction rate of AA in natural seawater significantly increased with decreased concentration. AA in different media exhibited relatively lower reaction rates under natural light than those under artificial light. However, AA at different concentrations had similar degradation and reaction rates under these two irradiation types. Visible light seemed more efficient for the degradation reaction than ultraviolet A and ultraviolet B rays. The concentrations and degradation of AA inside and outside the Jiaozhou Bay showed significantly seasonal variations, and the photochemical and microbial degradation both showed the maximum rates in autumn. The photochemical reaction rates were found to be lower than the microbial degradation rates in four seasons. The photochemical degradation inside the bay was always lower than that outside. The photochemical transformation of AA depended on seawater composition and field conditions. [ABSTRACT FROM AUTHOR]

As the degradation products of dimethylsulfoniopropionate (DMSP), dimethylsulfide (DMS) and acrylic acid (AA) are crucial to the sulfur cycle in the ocean. However, the biogeochemical processes of DMSP, DMS, and AA remain unclear. A monthly investigation was conducted to determine the DMSP, DMS, and AA concentrations and related parameters in the surface water of Jiaozhou Bay, a semi-enclosed bay in the western Yellow Sea, from December 2010 to November 2011. The monthly mean concentrations of DMSP, DMS, and AA were in the ranges of 5.02–27.25 nmol L−1, 0.41–3.14 nmol L−1, and below the detection limit–301.75 nmol L−1, respectively, showing significant seasonal variations with higher concentrations in summer than in autumn. The results were attributed to a combination of biogenic factors, including phytoplankton, zooplankton, and bacteria, as well as environmental factors, such as temperature and nutrients. The DMSP, DMS, and AA concentrations were not significantly correlated with chlorophyll a and bacterial abundance because of the influence of the community structure and anthropogenic activities. DMS was mainly produced by the enzymatic cleavage of DMSP, whereas AA was affected primarily by terrigenous input. The monthly mean sea-to-air fluxes of DMS ranged from 0.74 (in Apr) to 6.55 (in Jan) μmol m−2 d−1 with an average of 2.80 μmol m−2 d−1. • DMSP, DMS, and AA showed significant seasonal variations. • Biogenic sulfur variation was a combination of biogenic and environmental factors. • The monthly mean sea-to-air fluxes of DMS was estimated. [ABSTRACT FROM AUTHOR]

Abstract: The composition and characterization of dissolved organic matter (DOM) and colloid organic matter (COM) in the coastal surface waters of Qingdao, China were examined. Water samples were collected in Spring 2008 from the Jiaozhou Bay and its adjacent area and fractionated into total dissolved (<0.45μm), colloidal (10kDa–0.45μm) and cutoff (<10kDa) fractions with the cross-flow ultrafiltration (CFF) system. The excitation–emission-matrix (EEM) spectral properties, the absorbance values at 254nm (A 254) and dissolved organic carbon (DOC) of the DOM were observed having the colloidal ratios of 8.7%, 6.2%, and 2.2%, respectively, and exhibiting a decreasing trend. Total dissolved carbohydrates (TCHO) and total hydrolysable amino acids (THAA) comprised 24% of the bulk DOC. Among them, the free monosaccharides (MCHO) and dissolved combined amino acids (DCAA）were the major fractions, followed by polysaccharides (PCHO) and dissolved free amino acids (DFAA). Colloidal TCHO and THAA concentrations were 3.2µM C and 0.3µM, respectively. They comprised ∼35% of the colloid organic carbon (COC), among which PCHO and DCAA were the dominating fractions. The dissolved carbohydrates and amino acids are mostly concentrated in the cutoff fraction. The A 254 values and DOC concentrations inside the Jiaozhou Bay were apparently higher than those outside, while pH and salinity were slightly lower, which might be due to the influence of terrestrial input and the semi-enclosed bay. The distribution pattern of TCHO was found having basically the same as the distributions of A 254 and DOC. [Copyright &y& Elsevier]