Authors:L. Yu, S. Wang, X. Jiang, N. Wang and C. Zhang
Combustion experiments of three typical seaweeds (Gracilaria cacalia, Enteromorpha clathrata and Laminaria japonica) have been studied using a DTA-60H Thermal Analyzer and the combustion processes and characteristics are studied. Thermogravimetric
experiments are carried out on the samples with 0.18 mm particle size at the heating rate of 20°C min−1.
The results indicate that the ignition mode of seaweed is homogeneous and the combustion process is composed of dehydration,
the pyrolysis and combustion of volatile, transition stage, the combustion of char as well as the reaction at high temperature.
And the combustion characteristic parameters are obtained such as ignition temperature, maximum rate of combustion, burnout
temperature etc. The combustion models of these seaweeds are also analyzed. The combustion characteristics and model differences
between the seaweed and woody biomass are caused by the differences of volatile components. The combustibility indexes of
seaweeds calculated are better than that of woody biomass, and the index of Gracilaria cacalia is the best. At last, activation energies are determined using Arrhenius model that is solved by binary linear regression
To examine the radionuclide concentrations in the environment, seaweeds were collected once a year since 1976 at two different places. A marked change was observed in the number of radionuclides in seaweeds. The increase of radionuclides is attributed to contamination by radioactive fallout from Chinese nuclear explosion tests. The radionuclide concentrations were strongly dependent on the species of seaweeds. A gradual decrease of the137Cs/40K activity ratio was observed in spite of the input of additional137Cs fallout from Chinese nuclear tests. This implies that the amounts of137Cs introduced into seawater by these detonations were small in comparison with those already contained in seawater. The cesium content in seawater was estimated by using specific activities of137Cs in seaweeds and137Cs concentration in seawater. The results show good agreement with the reported values by direct analysis of seawater.
Loss of99Tc in seaweed during dry ashing has been investigated. Two kinds of brown seaweeds labeled with99Tc were ashed for 24 or 48 h at 400, 450 and 500 °C, showing no correlation between the loss of99Tc and species, temperature and time of ashing. The averaged recovery of99Tc was 91.0±4.0%, indicating that most of the99Tc in the seaweed was retained within the matrix of the ash which was obtained under general conditions of ashing.
Authors:Y. Serfor-Armah, B. Nyarko, E. Osae, D. Carboo and F. Seku
Eight seaweed species were sampled for a two year period from June 1996 to August 1998 along the coast of Ghana which is being
washed by the gulf of Guinea (part of the Atlantic ocean). An analysis was made of the levels of fourteen chemical elements
namely: Al, As, Au, Ca, Cd, Fe, K, Mg, Mn, Na, Ni, Hg, V and Zn by instrumental neutron activation analysis (INAA). Apart
from As, Au, Cd, Fe, and Hg the elements were measured in all the seaweed species studied. Al, Ca, K, Mg, and Na generally
showed the highest concentrations in most of the species analysed while the Hg content was low. The results showed high variability
in and between species, among sampling sites and times of collection. The high values of metal concentration in the macroalgae
suggest that these marine organisms can be used as biological indicators for studying marine pollution.
Five samples of brown seaweed, collected from a variety of sites around northern Europe, were distributed to 14 laboratories
for analysis of99Tc. Consistency in results between laboratories was found to be strongly correlated with concentration levels, with results
diverging markedly at99Tc concentrations below 100 Bq·kg−1. No systematic differences were apparent between radiometric and mass based techniques but the results do suggest that the
use of Re as a tracer may lead to an underestimation of99Tc levels.
The National Institute of Standards and Technology (NIST) seaweed Standard Reference Material (SRM4359) was developed through
an intercomparison of 24 experienced laboratories. Several statistical techniques were evaluated for establishing reference
values using the laboratories’ reported values including mean, midmean, median, Type B On Bias (BOB), Graybill-Deal, Mandel-Paule,
Vangel-Rukhin, Cox and Maximum Likelihood. After reviewing the results from all these techniques, the median was chosen as
a suitably robust way to calculate reference values. The uncertainties for the median values were estimated using bootstrap
Authors:Y. Serfor-Armah, B. Nyarko, D. Carboo, E. Osae, S. Anim-Sampong and E. Akaho
Fourteen seaweed species were sampled from October 1997 to May 1999 along the rocky shores of Ghana, which is being washed by the Gulf of Guinea (part of the Atlantic Ocean). Instrumental neutron activation analysis (INAA) was used to measure the iodine levels in the species, with the basic aim of selecting seaweed species that are rich in iodine and hence can be used as supplement in the diet of humans. This is to help solve the problems associated with iodine deficiency disorders (IDD). The levels of iodine found in the seaweed species ranged between 55 to 804 ppm. The precision, expressed in terms of relative standard deviation, and accuracy of measurements are within ±5–10%. The results show high variability in and between species and among sampling sites. The high values of iodine concentrations in the macroalgae suggest that these marine organisms can be used as supplement in the diet of humans.
The estimation of the Re concentration factor (CF) has been carried out to provide additional field information on the biochemical similarities between Re and Tc. Re concentration in brown seaweed samples from the North Atlantic Coast were measured using ID-ICP-MS. The chemical yields were quantitative, and the concentrations were distributed within a narrow range of 65-80 ng/g d.w. CF of Re was approximately 1.2 . 104 on average, i.e., one order of magnitude less than that found for 99Tc.