## 3 Results and Discussion
### Concentrations of Heavy Metals and Arsenicals in Seaweeds  
In general, most seaweeds adsorb and accumulate minerals and trace elements from the environment they inhabit, and effectively accumulate heavy metals like Cd, Pb, and As. The concentrations of heavy metals are summarized in Table 4. The concentrations of total As were mostly dominant in all of the collected seaweeds (_Pyropia_, _Enteromorpha_, _Undaria_, _Saccharina_, and _Sargassum_), whereas the concentrations of the other contaminants were marginal (<1.0 mg/kg). The Cd concentrations of the seaweeds ranged from 0.023 to 0.232 mg/kg fw. _Sargassum_ spp. had slightly higher Cd concentrations than the other seaweeds. Among the brown algae variety of seaweeds, _Sargassum_ spp. is considered an effective biosorbent of heavy metals, including Cd, from contaminated effluents [29; 30; 31]. [PERSON] and [PERSON] [32] compared the biosorption behavior of various brown, green, and red seaweeds and reported that the brown seaweed _Sargassum_ spp. had excellent Cd absorption capabilities. In the present study, however, the Cd concentration in _Sargassum_ varied widely, from 0.046 to 0.232 mg/kg fw. _U. pinmatifida_ is also considered a suitable adsorbent for heavy metal pollutants [33; 34], but the Cd concentration of _U. pinmatifida_, including the other seaweeds, was below 0.1 mg/kg. The concentrations of Pb in the different seaweeds ranged from 0.025 to 0.222 mg/kg, and all samples were suitable for consumption under Chinese regulations (Pb < 1 mg/kg in seaweeds). These results were similar to those reported in other studies (<0.3 mg/kg fw) in ROK [35]. As mentioned above, the results of variability in heavy metal concentrations in seaweeds may be due to differences in bioabsorption, due to factors such as seasonal or local variations, algal growth conditions, environmental factors (temperature, salinity, light, and pH), and the presence of industrial complexes or cities nearby [36; 37]. The concentrations of total As in the examined seaweeds ranged from 1.020 to 20.524 mg/kg fw, and were generally higher compared with the other heavy metals. Total As concentrations are generally higher in marine organisms than in terrestrial organisms [38], and accordingly, seafood such as fish, shellfish, and seaweeds exhibit much higher total As contents when compared to other kinds of foods. A considerable portion of As ingested by humans originates from the variety of seafood included in their diet [39]. The As compounds are classified as largely belonging to two forms, organic and inorganic species, which differ greatly with respect to their toxicity [40]. Organic As compounds mainly comprise MMA, DMA, AsC, and AsB. Of these, MMA and DMA were rarely found in seaweeds, as shown in Table 4, while DMA was detected almost exclusively in fish viscera (such as stomach, intestines, liver, and gills) [41]. AsC in seaweeds was also detected in low concentrations because it is rapidly transformed into AsB through the process of As metabolism [42; 43]. In other words, AsC plays a minor role as a metabolic precursor of AsB in the marine ecosystem [44]. As shown in Tables 4 and 5, however, the As species in the tissues or muscles of crustaceans, cephalopods, fish, and shellfish, which are mainly consumed by humans, mostly present in the form of AsB, produced by the endpoint of the As cycle in the marine environment, depending on specific microbial organisms [45], which is known to be a non-toxic and easily excreted material. Inorganic As species, particularly arsenite As(III) and arsenate As(V), which are much more toxic than organic species, comprise a small proportion of the total As in seafood. In this study, a relatively low amount of inorganic As species compared with the total amount of As was shown in crustaceans, cephalopods, fish, and shellfish (Tables 4 and 5). Similarly, [PERSON] and [PERSON] [46] reported that As(III) and As(V) account for less than 3% of the total amounts of As in fish and crustaceans.