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1.
The content of selenium and its chemical form in sea water 总被引:1,自引:0,他引:1
By using the new fluorometric method of determination of the total selenium ( Se), Se (IV) and Se (VI), the content of selenium in sea weter was determined in the western North Pacific. Results showed that the content of Se in surface water ranged from 0.06 to 0.12g l–1, while in deeper layers, the content increased to 0.20g l–1. It was found that Se (IV) showed rather uniform distribution with depth, while Se (VI) increased with depth to about three times that in the surface. The ratio of Se (IV) to the Se ranged from 0.5 to 0.8 in the surface and 0.4 to 0.6 in the deep. The coexistence of the hexa- and tetravalent ions of selenium was confirmed both in surface and deep layers. Some results of observations on the content of selenium in the coastal areas of Japan were also reported. 相似文献
2.
The Algal Growth Potential (AGP) of water samples collected off Gamagori in Mikawa Bay was measured from May 1978 through February 1979, and the limiting nutrient was determined using regression analysis and enrichment bioassays. The surface and bottom water samples had AGP that produced increments of chemical oxygen demand (COD) of 2.1 mg l–1 and 3.1 mg l–1, respectively, on average. These values ofCOD correspond to 46% and 97% of the average COD values of the raw water samples at the surface and bottom, respectively. Seasonal changes of AGP showed a close correlation with those of dissolved inorganic nitrogen (DIN) concentration. Enrichment bioassays showed that DIN was the most deficient nutrient. The DIN:phosphate-phosphorus (PO4
3–-P) ratios and DIN: dissolved phosphorus (DP) ratios in the water samples were below the cellular N:P ratios of the natural algal populations. These results suggest that AGP was mainly limited by DIN concentration. 相似文献
3.
Hirotaka Otobe 《Journal of Oceanography》1989,45(2):134-153
The downward short- and long-wave radiation fluxes at the sea surface (S, L) were measured aboard the R/VHakuho Maru, University of Tokyo, for the period of 117 days on six cruises from 1981 to 1985 in the western North Pacific near Japan. The upward fluxes of short- and long-wave radiation (S, L) were calculated by Payne's (1972) table and the Stefan-Boltzmann's law, respectively. The sensible and laten heat fluxes (Q
h
,Q
e
) were also estimated from an aerodynamic bulk method.From April to August, the daily mean value ofS varied with the amplitude of 100200 Wm–2. The value ofS was estimated approximately 6% ofS in all seasons. The difference betweenL andL was so small that the net radiation flux (Q
n
) was dominated byS. In addition, the net heat flux at the sea surface was also dominated byS due to small values ofQ
h
andQ
e
, and then the ocean was warmed at the rate of 111 Wm–2 in April and 63 Wm–2 in August in the Oyashio Area, and 132 Wm–2 in May and 164 Wm–2 in June in the Kuroshio Area, respectively.From September to March, a remarkable negative correlation between the day to day variation ofS and that ofL was observed except when an intense cold air outbreak occurred. It was found that the correlation was caused by the cloud climatological feature of the western North Pacific in this period.S was not a dominant factor in the net heat flux. The value ofQ
h
+Q
e
in the Kuroshio Area ranged from 260 Wm–2 to 630 Wm–2, much larger thanQ
n
which ranged from –8 Wm–2 to 92 Wm–2 in the leg mean values (each leg period was about 10 days). Then the ocean was cooled at the rate of –160–620 Wm–2 during this period. The net heat flux in the Kuroshio Area averaged over five legs from late November to February was –473 Wm–2. This value is 50100% larger than the climatological values reported so far.The temporal and spatial variability of radiation fluxes and heat fluxes during each leg was also discussed. 相似文献
4.
Environmental parameters that affect the growth ofChattonella antiqua were monitored throughout the outbreak period of this species around the Ie-shima Islands, the Seto Inland Sea, in the summer of 1987 (20 July–13 August). Averaged cell concentration ofC. antiqua over the water column (21 m) was below 10 cells· ml–1 on 20 July, gradually increased to reach the maximum of 250 cells·ml–1 on 7 August, and then rapidly decreased to the value of 30 cells·ml–1 on 13 August.Thermal stratifications were prominent from 20 July to 3 August and were destroyed after 4 August. Temperature and salinity were optimum for the growth ofC. antiqua throughout the survey period.At the bloom initiation period (20–21 July), concentrations of N- and P-nutrients (S
N
andS
P
) were high throughout the water column. From 22 July to 3 August, whenC. antiqua increased its populations,S
N
andS
P
at the depth of 0–5m were low but those at the depth of 10–20m kept a high value. After 4 August,S
n
andS
P
at the depth of 10–20m decreased rapidly due to wind mixing coupled with the nutrient uptake byC. antiqua. When the populations ofC. antiqua reached the maximum (7–9 August), N-nutrients were depleted throughout the water column but P-nutrients were not. Concentrations of vitamin B12 were almost in the same range as those of the previous years and were optimum for the growth ofC. antiqua.GP- value (growth potential of the seawater with respect to nitrogen and phos-phorus) was higher than 0.6 even at the surface layer (0–5 m) at the bloom-initiation period. During the bloom development period (22 July–3 August), GP at the surface layer (0–5m) was low (<0.2), but GP at the depth of 10–20m kept a rather high value (>0.4).In situ growth rates ofC. antiqua at the depth of 0 and 5m estimated from bottle experiments coincided well with the values expected from GP. A high value of GP at the surface layer in the initiation period and a shallow GP-cline in the development period, combined with the ability of diurnal vertical migration seemed to be at least one reason that natural populations ofC. antiqua grew at a rather high rate and formed red tides in the summer of 1987. 相似文献
5.
The interaction of selenium with mercury was studied in the shrimp Palaemon elegans. The release of 203HgCl2 (5·0 μg Hg per gramme body weight) from shrimp pretreated with selenium (SeO2 doses of 1·97, 3·95 and 7·90 μg Se per gramme fresh weight) was significantly decreased compared with the control group to which only 5·0 μg Hg/g had been administered.In the presence of HgCl2 (5·0 μg Hg per gramme fresh weight) the release of 75Se also diminished significantly at the higher stable Se pretreated dose (7·90 μg Se/g) while, at a lower selenium concentration, the release was not statistically different. Analyses for stable Hg and Se confirmed the decrease in rate of selenium loss in the presence of mercury which had been demonstrated with radiotracers.A dose of 7·9 μg Se per gramme fresh weight injected 12 h before exposure of the shrimp to the various mercuric chloride solutions did not produce a significant difference in the 24 h LC50 compared with the group not pretreated with selenium. However, during exposure to mercury at 3·8 mg/litre, the median lethal time (LT50) for the shrimp pretreated for 4 days with sublethal selenium (6·9 and 10·5 mg Se/litre) was delayed (19·2 and 33·2 h) compared with the group which was not pretreated. The results are discussed in relation to the role of selenium in the acutely toxic effects of inorganic mercury. 相似文献
6.
Yasuo Nakamura 《Journal of Oceanography》1985,41(1):33-38
Ammonium uptake kinetics and interactions between nitrate and ammonium uptake were examined inChattonella antiqua. After the addition of ammonium to the culture ofC. antiqua, the ammonium concentration decreased linearly with time. The ammonium uptake rate as a function of ammonium concentration followed the Michaelis-Menten equation; the maximal uptake rate was 2.0 pmol cell–1hr–1 and the half saturation constant, 2.2M. Although the ammonium uptake was not affected by nitrate, uptake of nitrate was rapidly (15min) suppressed by ammonium and a 50% reduction in nitrate uptake was observed at an ammonium concentration ofca. 2M. 相似文献
7.
The rates of the reduction of Cr(VI) with S(IV) were measured in deaerated NaCl solution as a function of pH, temperature and ionic strength. The rates of the reaction were found to be first order with respect to Cr(VI) and second order with respect to S(IV), in agreement with previous results obtained at concentrations two order higher than the present study. The reaction also showed a first-order dependence of the rates on the concentration of the proton and a small influence of temperature with an apparent energy of activation ΔHapp of 22.8 ± 3.4 kJ/mol. The rates were independent of ionic strength from 0.01 to 1 M. The rate of Cr(VI) reduction is described by the general expression
−d[Cr(VI)]/dt=k[Cr(VI)][S(IV)]2