| The ocean is an important passway for the global material cycles. Marinephytoplankton is an important carrier for the cycle of metal elements. The elementcomposition of phytoplankton is depended on their species, biomass andenvironmental factors. The imigration and transport of elements in marine organismsplays an important role for biogeochemical cycle. The study of metal content ofmarine phytoplankton can provide the foundimental information for understanding thecycle of metal elements.The phytoplankton samples were collected with a plankton-net from the coastalsea near Qingdao. The metal contents of the phytoplankton samples were measuredwith an inductive coupled plasma-atomic emission spectrometer (ICP-AES) after aciddigestion. The distribution characteristics of metal of phytoplankton sample and theinfluence factors were discussed base on the results of determination. Laboratoryculture of selected phytoplankton species was carried out to detect the influence of Cu,Zn levels on the growth rates and metal element composition. In order to dissolve theproblem of the insufficiency of the natural phytoplankton samples, a microflownebulizer was applied in ICP-AES. The working conditions of the microflow neblizerwere optimized to minimize the consumption of the samples. The main results andconclusions are shown as follows:(1) The application of the microflow nebulizer in ICP-AES reduced theconsuption of the test samples. It consumed one third or less of the sample amounts ofthe normal nebulizers, and the analytical efficiency was thus increased. The optimalworking conditions were obtained as follows: the nebulizer gas pressure was0.2MPa,the RF power was1150W, the peristaltic pump rotary speed was25r/min, and theauxiliary gas flow rate was0.5L min-1. The response intensities, the background values and the detection limits using the microflow nebulizer were compared withthose using a normal nebulizer under their optimal working conditions. Detectionlimits and the standerd deviation of the elements measured by the both neblizers werecomparable. Good results were obtained from the analyses of three kinds of samples,i.e., an extract of marine sediment, a phytoplankton sample and a sample of suspendedparticulate matters.(2) It showed the general pattern that the contents of metal elements were higherin phytoplankton samples from the nearshore stations than those from the offshorestations in Qingdao coastal sea. In terms the contents of unit quality samples of Al, Ca,Fe, Mg were relatively high, and the contents of Mn, Ti, Ba, Cr, Cu, Sr, V, Zn, Co, Niand P were relatively low. The contents of Fe, Ba, Cr, Cu and Zn were higher insidethe Jiaozhou bay than those of the outside stations. The content of Zn was high ineach station.(3) The phytoplankton samples were affected by the coexistence of clay mineralconglutination.Because the sampling region was coastal sea, and the biomass was stillin lower level in the early spring, the effect of the clay minerals conglutination wasmore significient. In order to eliminate the influence of clay minerals, correction withAl was applied. Fe, Mn, Ti, Ba, Co, Sr and V contents were mainly affected by theclay minerals, while Cr, Ni, Zn were hardly affected by this conglutination. Ca, Mg,Cr, Cu and Ni were affected both by biological production and clay mineralsconglutination. Corrections of the clay mineral conglutination to Ca, Mg, Cr, Cu andNi were carried out. The average composition of elements of the phytonplanktonsamples was (P1Mg0.97Ca0.32)1000Zn10.4Cu0.16Cr6.1Ni4.0. The enrichment factor value(EF) indicated that Cr, Cu, Ni and Zn had obvious biological enrichment inphytoplankton samples.(4) A dominate species in Qingdao coastal sea, Skeletonema costatum, and twobait microalgae Platmonas Phaeodactylum and Tetraselrnis subcordiforus werechoosen for culture experiments,which were carried out under changing Cu and Zn(two elements of obvious biological enrichment) levels. The results showed that the growth rates of the cultured algae were little affected by the level of Cu and Zn. Thehigh Cu level might limit the absorption of Ca in Tetraselrnis subcordiforus and theabsorption of Cu in Skeletonema costatum. The high and low Zn levels might limit theabsorption of Fe in Skeletonema costatum, the absorption of Sr in Tetraselrnissubcordiforus and the absorption of Cu in Phaeodactylum. The increase of Zn levelmight limit the absorption of Ca and Zn by skeletonema costatum. The range ofmetals concents were smaller in different Cu and Zn levels than those in differentnutrient levels, which indicate that the affect of the Cu, Zn levels on metal uptakewere smaller than those of the nutrient levels.(5) The element composition from the culture algae was (P1Fe0.38Mg14Ca0.36)1000Zn6.9Mn19Cu0.63V0.56Cr3.0Ni2.5Ba3.4Co0.21. It showed small difference with that fromthe collected phytoplankton samples. This phenomenon implicated the stability ofelement composition of phytoplankton, which might be formed during the long periodof growth and reproduce in a relatively stable environment. |
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