The determination of 52 elements in marine geological samples by an inductively coupled plasma optical emission spectrometry and an inductively coupled plasma mass spectrometry with a high-pressure closed digestion method

An improved analytical method to determine the content of 52 major, minor and trace elements in marine geological samples, using a HF-HCl-HNO_3 acid system with a high-pressure closed digestion method（HPCD）, is studied by an inductively coupled plasma optical emission spectrometry（ICP-OES） and an inductively coupled plasma mass spectrometry（ICP-MS）. The operating parameters of the instruments are optimized, and the optimal analytical parameters are determined. The influences of optical spectrum and mass spectrum interferences, digestion methods and acid systems on the analytical results are investigated. The optimal spectral lines and isotopes are chosen, and internal standard element of rhodium is selected to compensate for matrix effects and analytical signals drifting. Compared with the methods of an electric heating plate digestion and a microwave digestion, a high-pressure closed digestion method is optimized with less acid, complete digestion,less damage for digestion process. The marine geological samples are dissolved completely by a HF-HCl-HNO_3 system, the relative error（RE） for the analytical results are all less than 6.0%. The method detection limits are 2–40μg/g by the ICP-OES, and 6–80 ng/g by ICP-MS. The methods are used to determine the marine sediment reference materials（GBW07309, GBW07311, GBW07313）, rock reference materials（GBW07103, GBW07104,GBW07105）, and cobalt-rich crust reference materials（GBW07337, GBW07338, GBW07339）, the obtained analytical results are in agreement with the certified values, and both of the relative standard deviation（RSD） and the relative error（RE） are less than 6.0%. The analytical method meets the requirements for determining 52 elements contents of bulk marine geological samples.

Calculation of photosynthetically available radiation using multispectral data in the Arctic

Photosynthetically Available Radiation（PAR） is an important bio-optical parameter related to marine primary production.PAR is usually measured by a broadband sensor and can also be calculated by multispectral data.When the PAR is calculated by multispectral data in polar region,four factors are possible error sources.PAR could be overestimated as the wavelengths of multispectral instrument are usually chosen to evade main absorption zones of atmosphere. However,both PARs calculated by hyperspectral and multispectral data are consistent with an error less than 1%.By the fitting function proposed here,the PAR calculated by multispectral data could attain the same accuracy with that by hyperspectral data.To calculate the attenuation rate of the PAR needs PAR_0, the PAR just under the surface.Here,an approach is proposed to calculate PAR_0 by the best fit of the irradiance profile of 1-5 m with a content attenuation coefficient under surface.It is demonstrated by theory and observed data in different time at same location that the attenuation coefficient of PAR is independent of the intensity of radiation.But under sea ice,the attenuation coefficient of PAR is a little bit different,as the spectrum of the light has been changed by selective absorption by the sea ice.Therefore,the difference of inclusions inside the sea ice will result in different PAR,and impact on the attenuation of PAR.By the results of this paper,PAR can be calculated reliably by multispectral data.