Mineralogical Study Of The Wild Carp's Otoliths From Baiyangdian Lake And Miyun Reservoir And Their Environmental Responses

In this paper, environment responses between carps'otolith minerals and their living environments, Baiyangdian lake, seriously polluted, and Miyun reservoir little polluted, were studied based on X-ray diffraction analysis (XRDA), thermoluminescence experiments, electron probe micro-analysis (EPMA), neutron activation analysis (NAA) and laser ablation inductively coupled plasma-mass spectrometry analysis (LA-ICPMSA).All samples from two sites are composed of vaterites, which divided into three different crystal structures: two types of hexagonal cells and one type of orthorhombic cell; while most samples with hexagonal cells. Though no obvious difference for otolith mineral types and their crystalline structures among the two sites at large, for the vaterites, with hexagonal cell, clear differences exist in these samples from two sites. The dimensions of samples'crystalline cells of vaterites in the otoliths from Miyun reservoir are more nearer to the standards than those from Baiyangdian lake; the a₀ and the cell volumes of the former is relatively bigger than the latter, but c0 are reverse. The a₀ and the cell volumes of the former are nearer to the standards than the latter.The thermoluminescence curve parameters of the fish otoliths from Baiyangdian Lake are greater than those from Miyun reservoir accordingly. At the same testing temperature, the escape probility (α) of the former is bigger than the latter, and energy gap (E) inversely.The results show that the main differences between the two sites are the contents of Sr, Zn, As and Ba, ordered by absolute size of correlation within Linar Discriminant Function. High positive correlation exists between Sr and Zn without influenced by otolith weight, which demonstrated that Sr and Zn maybe have the same manner to occupy ion sites in the crystalline structure; while As and Ba maybe have other manner to do it. If the Miyun Reservoir was regarded as no polluted and standard aquatic environment, the contents of As, Sr and Ba elements within otoliths from the Baiyangdian Lake show abnormal intermittently, Na waved intermittently, Zn abnormal continuously, Au unvaried at large, and K nearly same as the Miyun Reservoir. These abnormal contents of elements may be in relationship with intermissive drain contamination from local manufactories and domestic garbage.Trace elemental compositions for rings within otoliths were determined using LA-ICPMS. At large, from Sept. 2004 to the year of 2002, for the curve of elements concentrations within otoliths from the Baiyangdian Lake, elements concentrations vary relatively larger in the rings near the annuli than other rings; most elements concentrations are with moment high values near annuli. In the period from Sept. of 2004 to the year of 1997, the situation for the variations of elements concentrations within otoliths from the Miyun Reservoir mainly divided into two stages. From 2004 to 2003, elements contents varied relatively slightly; from the time, begin in the winter of 2002 and end in the beginning of 2003, to the year of 1997, elements contents varied relatively large; lots of elements concentrations appear high at the period of spring and summer season of a year.For the trace elements contents within otoliths, dynamic responses to aquatic environment hydrochemistry are different due to different otolith types. The contents of elements Sr, K, Na, Ba, Zn, Cr, Fe, As, Au in the asteriscus otoliths and the contents of elements Sr, Na, Ni, Cu, Zn, Pb, Cr, Co within the lapillus otoliths are under the influence of their concentrations in the water; these elements can be used as the target elements to monitor environmetal hydrochemistry.Carps'otolith minerals from these two sites are well responsed to the characteristics of their aquatic hydrochemistry. Distinct discriminations for trace elements concentration between two aquatic environments are shown by otoliths'mineral crystalline structures and their cell parameters, characteristics of thermoluminescence curves, and contents of trace elements. Elements'concentrations in different period in the water are revealed by contents of these elements within otoliths as well. These mineralogical characteristics can be used as reliable hydrochemical proxies; and otolith mineral is a kind of material to monitor aquatic environments.