Mercuric Hg(II) species form complexes with natural dissolved organic matter (DOM) such as humic acid (HA), and this binding is known to affect the chemical and biological transformation and cycling of mercury in aquatic environments. Dissolved elemental mercury, Hg(0), is also widely observed in sediments and water. However, reactions between Hg(0) and DOM have rarely been studied in anoxic environments. Here, under anoxic dark conditions we show strong interactions between reduced HA and Hg(0) through thiolate ligand-induced oxidative complexation with an estimated binding capacity of ∼3.5 μmol Hg/g HA and a partitioning coefficient >10 6 mL/g. We further demonstrate that Hg(II) can be effectively reduced to Hg(0) in the presence of as little as 0.2 mg/L reduced HA, whereas production of Hg (0) is inhibited by complexation as HA concentration increases. This dual role played by DOM in the reduction and complexation of mercury is likely widespread in anoxic sediments and water and can be expected to significantly influence the mercury species transformations and biological uptake that leads to the formation of toxic methylmercury.Hg-dissolved organic matter complex | environmental factors | methylation | redox M ercury (Hg) is well known to bioaccumulate and biomagnify as neurotoxic methylmercury (CH 3 Hg + ) in organisms, particularly fish (1-3). Biologically mediated production of CH 3 Hg + predominantly occurs under anaerobic conditions (4-8). However, the environmental factors that determine Hg availability to methylating bacteria and its transformation under these conditions remain poorly understood (1, 9-12). In particular, the coupled reactions between Hg redox transformation and complexation with natural dissolved organic matter (DOM) remain unclear, yet this process may critically control the speciation, biological uptake, and methylation of aqueous Hg in aquatic environments (9)(10)(11)(13)(14)(15)(16)(17). DOM occurs in all natural sediments and water, usually at concentrations much higher than Hg (1, 9). It is known to form exceptionally strong complexes with the oxidized mercuric species, Hg(II), due to its coordination with reduced sulfur (−S) or thiol (−SH) functional groups in DOM at relatively high DOM:Hg(II) ratios (11,(18)(19)(20)(21). Such complexation has been shown to limit Hg(II) availability for bacterial methylation (9, 22, 23); however, facilitated uptake and methylation are also reported, especially when Hg(II) is complexed with small molecular-weight thiol compounds such as cysteine (5,24).Although a large body of literature is now available on the interactions of oxidized Hg(II) species with DOM, reactions between reduced gaseous Hg(0) and DOM have rarely been examined in natural sediments and water where dissolved Hg(0) is also observed (16,17,(25)(26)(27)(28)(29)(30)(31). Hg(0) has a solubility of ∼56 μg/L in water (32). Its formation can be mediated biologically (25, 26, 33), chemically (34, 35), or photochemically in the aquatic environment (15-17, 27-31). However, the role pla...

Cis (Z)-β-carotenes with 25.3% 9Z-β-carotene were prepared for nanostructured lipid carriers (NLCs). The optimal conditions for NLC preparation using an orthogonal experimental method were as follows: the total lipid concentration was 9% (w/v), the surfactant concentration was 1.4% (w/v), the solid to liquid lipid ratio was 3:1 (w/w), and the homogenization pressure was set at 500 bar for three cycles. Under these conditions, the encapsulation efficiency (%) of the NLC was 95.64%, and the total β-carotene in NLCs was 2.9 mg/mL, which was significantly higher than those reported by others. The proportion of total Z-β-carotenes was as high as 53.3%, the particle size was 191 ± 6.46 nm, and the polydispersity index was 0.2 ± 0.03. Storage stability results indicated that the β-carotene-loaded NLC stabilizes both 9Z-β-carotene and total β-carotene from leakage and degradation during 21 days of storage at pH 3.5–7.5 at low temperatures (4 °C), especially for the more bioactive 9Z-β-carotene. The technique with an improved ratio of 9Z-β-carotene, loading capacity, water solubility, and bioaccessibility of the β-carotene NLC provides an effective strategy for β-carotene applications in functional foods or beverages and in nutraceutical preparations.

A waste-derived adsorbent was prepared from waste carbon that was obtained from the monosodium glutamate production, by microwave heating under ultrasonic spray conditions for removing methylene blue (MB) from wastewater.