排序方式: 共有2条查询结果,搜索用时 0 毫秒
1
1.
New Procedure for Extraction of Ammonium from Natural Waters for 15N Isotopic Ratio Determinations
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A new method for extracting ammonium from natural waters for 15N isotopic ratio determination is described. The method employs the conversion of the ammonium nitrogen into indophenol, which is then concentrated onto an octadecylsilane column. The method shows accuracy and precision comparable to those of other methods described in the literature. Some results from field experiments on the Swedish west coast are presented. 相似文献
2.
Gustavson Kim; Garde Kristine; Wangberg Sten-Ake; Selmer Johanne-Sophie 《Journal of plankton research》2000,22(8):1501-1511
The impact of UV-B radiation (290315 nm) on bacterialactivity and abundance in coastal water was studied in mesocosmexperiments in May 1994 and May 1995 at Kristineberg MarineResearch Station, Sweden. Mesocosms (6 m3) containing naturalpelagic communities were exposed either to ambient irradiation(AMB), ambient irradiation with enhanced UV-B (+UV) (0.7 W m24 h every day around noon), or ambient irradiation screenedfor UV-B (UV). Bacterial activity in the mesocosms wasmeasured by means of thymidine incorporation in short-term testsduring incubations at ambient irradiation, at ambient irradiationwith enhanced UV-B, and at ambient irradiation screened forUV-B. In +UV mesocosms, bacterial activity was significantlystimulated when incubated at ambient radiation. The stimulatingeffect was suggested to be due to an increase in carbon or nutrientsupply through a photodegradation of recalcitrant dissolvedorganic material (DOM). Low attenuation coefficients for UV-Band PAR (400700 nm) in the +UV mesocosms supported thishypothesis. The bacterial activity in +UV mesocosms, however,was inhibited when incubations were made at enhanced UV-B irradiation,implying that the bacteria had become more sensitive to UV-Bradiation. The increased sensitivity to UV-B exposure in bacterialassemblages that already had been exposed and stressed by UV-Bradiation is suggested to be due to an overburdening of theenergy-consuming DNA repair mechanism. The data suggest thatincreased UV-B radiation, which might occur with ozone depletion,may both stimulate and suppress bacterial activity in coastalwaters, implying that the net outcome of enhanced UV-B radiationcould be an unchanged bacterial activity. 相似文献
1