# Atomic Spectroscopy-Based Analysis of Heavy Metals in Seaweed Species
## 2 Atomic Spectroscopy-Based Heavy Metal Analysis Methods for Seaweed
### Atomic Emission Spectroscopy
#### 2.3.1 Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES)
A quantity of 0.1 mL of 50 ppm of Au and Lu mix was also added. Digestion was carried out at 190 \({}^{\circ}\)C for 15 min. Analysis of the metal elements As, Cd, Cr, Cu, Hg, Ni, and Pb was performed with ICP-OES. NIST-SRM 3232 for kelp powder was used for method validation, with recovery values ranging from 85.9 to 97.4. The concentrations of the seven metal elements measured in this study were in the order: Cr \(>\) Ni \(>\) Cd \(>\) Cu \(>\) As \(>\) Pb = Hg, where both Pb and Hg were not detected in any of the samples. The high concentration of Cr was hypothesized to be due to the increased levels of industrialization in these areas. The authors also assessed the health risk of seaweed consumption, based on consumption data in Mainland China, since most of the harvest from Sri Lanka is exported. [PERSON] et al. collected 64 seaweed samples of various species from the _Plueophyta_ group from three areas in the Canary Islands, Spain [5]. After the homogenization step, 3 g of each sample was dried in an oven at 70 to 75 \({}^{\circ}\)C for 24 h, then digested with 65% HNO\({}_{3}\) and incinerated in a muffle furnace at 420 \({}^{\circ}\)C for 24 h. The resulting ashes were dissolved in up to 25 mL of 1.5% HNO\({}_{3}\) and subject to ICP-OES analysis for the metal elements Cd, Fe, Ni, Pb, and V. Three reference materials (SRM 1515, SRM 1570a, and BCR 279) were used for method validation, and the recovery percentages were found to be over 94%. The authors concluded that the growing area is an important factor affecting seaweed metal concentrations, possibly due to the differences in marine currents and human activity. Among the various species, _P.uronic_ contained the highest concentrations of toxic metals and trace metals. While none of the metals analyzed (in all the seaweed samples) pose a health risk for human adults, assuming the daily consumption to be 5 g of dehydrated seaweed, estimated daily intake (EDI) of Pb in _P.aponic_ does reach as high as 57.2% of tolerable daily intake (TDI). Four species of seaweed were collected from the Wandoor area of Southern Andaman Island during three different seasons to assess the potential of seaweed to monitor heavy metal pollution in aquatic ecosystems [74]. Quantities of 0.5 g of each sample were digested with 5 mL aqua regia HCl and HNO\({}_{3}\) (3:1). The digested samples were filtered, diluted to 50 mL, and analyzed with ICP-OES for concentrations of Cd, Cr, Cu, Mn, Pb, and Zn. The average metal accumulation was ordered as Mn \(>\) Zn \(>\) Cu \(>\) Cr \(>\) Cd \(>\) Pb for three collection seasons. The highest accumulation was found in the seaweed species _P.aponica_, with 7.736 \(\upmu\)g/g of Mn. After comparing accumulation levels in brown and green algae from this study, the authors suggested that brown algae can be better used as a biomonitor for trace metal studies since they retained higher levels of all the metals reported in this paper. On the other hand, the authors also pointed out that, in a previous study [75], a green algae species was observed to have potential for metal uptake, especially Zn. Furthermore, based on the measured concentrations of all six metal elements and the calculated metal pollution index (MPI), the authors concluded that the Wandoor area of Southern Andaman Island remains mostly unaffected by industrial pollution. Seaweeds (eight species) were collected at various sites from the area of an abandoned intertidal copper and zinc mine in Brooksville, ME, USA [20]. The collection sites included two estuary locations where the mine was situated and locations with slower water movement, one waterfall site near the estuary outlet, and some clean sites. The seaweed samples were carefully cleaned to remove metal particulate contaminants, then rinsed, scraped, and bathed in a solution of 10% ethanol and 3.5% NaCl, followed by two baths in DI water while being gently scrubbed.