胶州湾沉积物中氮与磷的来源及其生物地球化学特征

SOURCE AND BIOGEOCHEMICAL CHARACTERISTICS OF NITROGEN AND PHOSPHORUS IN JIAOZHOU BAY SEDIMENTS

通过对比分析和相关分析对沉积物中氮、磷含量、OC∶TN、TN∶TP进行了研究,探讨了胶州湾沉积物中氮、磷的来源及其生物地球化学特征。研究表明,胶州湾表层沉积物中总氮、总磷的变化趋势一致,即从湾内到湾外含量依次降低,其中总氮依次为0.41、0.25、0.20mg/g,总磷的含量依次为0.29、0.24、0.22mg/g。在整个柱状样中总氮、总磷平均含量的变化也和表层基本一致,有机氮在大部分层次占总氮的50%—70%,无机磷所占总磷的比例一般大于60%。根据沉积物OC∶TN比、氮、磷的垂直分布可以判断湾内和湾口沉积物中的氮主要是陆源的,海洋自生的氮分别占28.9%和13.1%,湾外的氮主要是自生的,海洋自生的氮占62.1%。与氮相比,磷主要是陆源的,但在湾外海洋自生磷的比例明显高于湾内。悬浮颗粒物的组成也证明了湾内沉积物中氮、磷主要是陆源的。沉积物中OC∶TN值的垂直变化也反映了近年来胶州湾物质来源的变化特征,即河流来沙急剧减少,沿岸倾倒垃圾不断增多,后者已经取代前者成为胶州湾主要的沉积物来源。另外,沉积物中TN和TN∶TP的垂直变化也和近年来胶州湾水体中营养盐含量的变化相一致。胶州湾不同地区氮、磷的沉积通量相差很大,湾口的沉积通量最大,而湾外的沉积通量最小;在表层沉积物中,氮的矿化速率高于磷,有机磷的矿化速率大于无机磷,但有机氮的矿化速率并不一定大于无机氮。OC、pH、Eh、Es等环境因素影响氮、磷的矿化,但在不同海区影响程度并不相同。

Nitrogen and phosphorus in sediment play an important role in marine ecosystem, so many studies focused on it. The source and biogeochemical characteristics of nitrogen and phosphorus were discussed using the field data on content and vertical distribution of TN, TP, ON, OP, IN, IP, OC ： TN, TN： TP in sediments obtained from the Jiaozhou Bay. The results obtained imply both the total nitrogen and the total phosphorus in surface layer of sediment decrease when moving from the inner bay to the outer bay. The concentration of total nitrogen in surface layer sediment was 0.41, 0.25, 0.20mg/g, and of total phosphorus is 0.29,0.24,0.22mg/g in inner bay, bay mouth and outer bay respectively. In general, organic nitrogen occupy 50%-70% of total nitrogen and inorganic phosphorus account for more than 60 % of total phosphorus. The vertical distributions of N and P are more completed than horizontal distribution. The ratio of TOC：TN can be used to deduce the source of organic matter in sediment. According to the ratios of TOC ： TN, organic matter from terrene account for 71.1% in station B3, 86.9 % in station D4, 37.9% in station D7, respectively. So Nitrogen accumulated in sediment of the inner bay and the bay mouth mainly come from terrene by vertical distribution of N, P and OC：TN, and the portion of autogenetic N is 28.9 % and 13.1%, respectively. However, in the outer bay N is mainly of autogenetic constituting 62.1% of total nitrogen. In contrast to N, phosphorus mainly contributes from terrene; however the percentage of autogenetic P in the outer bay is remarkably higher than that in the inner bay. The date on suspended particle confirms that N and P in sediment of the inner bay are also mainly originated from terrene. The vertical variation of the OC ： TN ratio in sediment of the Jiaozhou Bay reflects the change of materials source over recent years. The sand input from rivers has decreased sharply, however the garbage input from Qingdao and surrounding regions has permanently increased. Thus, currently the garbage input substituting sand input, is the main source of sedimentation. The vertical distribution of TN, TP contents and TN： TP ratio are in accordance with the increased trend of nutrient content in seawater of the Jiaozhou Bay. The sedimentation fluxes vary spatially. The sedimentation flux is the highest in the bay mouth and the lowest in the outer bay. In same region, the sedimentation flux is obvious difference between organic nitrogen, organic phosphorous and inorganic nitrogen, inorganic phosphorus in same region because of their different content. Nitrogen and phosphorus in inner bay release from sediment to sea water according to diagenetic rate, which indicate that N and P in sediment is an important source of N and P in sea water in inner Bay. However, N and P in sea water may transport to sediment in outer bay. Diagenetic rate of N is higher than that of P, whereas diagenetic rate of organic phosphorus is higher than that for inorganic phosphorus. However, the diagenitic rate of organic nitrogen was found to be not always higher than that of inorganic nitrogen, and the diagenitic rate of inorganic nitrogen was far higher than that of organic carbon sometimes, which indicated that inorganic nitrogen play a neglected role in the movement of nitrogen. OC, pH, Eh, Es can affect diagenetic rate; however their influence is different in various.