Phosphine Distribution Characteristics In The Sediments Of Jiaozhou Bay And Its Transformation And Release

Phosphine has been proved to be widespread in the environment; however, its function and status in the biogeochemical recycle has not been identified so far. Now people have focused attention on researches of phosphine not only in air and land, but also in lake and marsh. Nevertheless, little information is available on the function of phosphine in marine. Therefore, it is of great significance to make thorough study on its distribution characters in marine sediments and the transforming mechanism of phosphine so that evidences would be provided for its function in the phosphorus biogeochemical recycle. We have identified the distribution characteristics of phosphine and its relationship with the sedimental environment in Jiaozhou Bay. Results demonstrate that phosphine is a kind of gaseous phosphorus compound that is widespread in the sediment of Jiaozhou Bay, and its peak concentration reaches to 970.39 ng / kg (dry weight). The phosphine concentration and distribution were mainly affected by the organic phosphorous, the redox potential and the sediment composition. Moreover, an obvious regularity of distribution was observed that phosphine concentration in coastal sediments was higher than that in offshore's, and concentration within the Bay was higher than that of outside Bay. Results also reveal that phosphine concentration in such seriously polluted areas as culture farm and estuary was significantly higher than that in other investigated places. In sediment the higher concentration of organic phosphorus, the lower redox potential and smaller particle size, would be the more benefit to the existence of phosphine. The effects of environmental factors on the transforming process of phosphine in water are identified under controlled experimental conditions. Flasks containing manmade seawater are enriched with different volumes of phosphine, whose concentration is 100 ppm. The concentration changes of phosphine above the water are determined. Results demonstrate that the phosphine concentration decreases quickly at the first hours when the standard phosphine is enriched into the flask, and keeps constant thereafter. The simultaneous assay on phosphate and total phosphor in water shows increment in the system. The comparative study on the turnover rate suggests that most of the transformed phosphine exists in forms of orthophosphate in the water, and other transforming substances may be exist as some intermediate substances, such as hypophosphite, phosphite. The turnover rate is low under controlled experimental conditions, but increases when the oxygen is enriched into the experimental system, although the amount of transformed phosphine is still a little. Results also show that the transforming tendencies of phosphine are much similar in either natural seawater or fresh water. What's more, the initial concentration of phosphine does not significantly affect its turnover rate. A preliminary study on discharge of phosphine from the sediment is also carried out, and the discharging flux is estimated simultaneously. The simulating results under laboratory conditions show that the phosphine may be discharged from the sediment to the water and air. The discharging amount increases in pace with the environmental temperature increasing, and the pH affect the phosphine discharging. The discharing fluxes under different conditions are also estimated. Based on the results of the present study, it appears that the phosphine which is discharged into the water may transformed into the available phosphorous, which may have potential effects on marine eutrophication and the bloom organism proliferations, especially in those phosphorous limited marine areas. Further researches should be carried out to provide evidences for the hypothesis above described in controlled laboratory conditions, especially under natural conditions.