Nutrients in porewater of sediment profile 13368-045

Total carbonate (Ct) concentrations were determined on-board ship during Discovery 222 (leg A) nd 226 cruises, using colourmetric methods (Johnsson et al., 1987) with a precision of 0.2% RSD (n=10) using a sample loop of 4ml. During Discovery 231, 236 and Meteor 42/2 cruises a newly developed system (based on infrared detection of (CO2) were used for determination of total carbonate (Goyet and Snover, 1993; OSullivan and Millero, 1998). The precision of this method was also 0.2% RSD (n=10) using a sample loop of 4ml. Samples were filtrated through disposable sterile cellulose acetate filters (0.45µm) and stored refrigerated in polyethylene vials (rinsed in MQ-water) until analysis on-board.总碳酸盐（Total carbonate, Ct）浓度的测定工作于“发现号”（Discovery）222航次（A航段）及226航次期间在船载现场完成，采用比色法（Johnsson等，1987），测定时使用4mL样品环，精密度达0.2%相对标准偏差（Relative Standard Deviation, RSD），平行样品数n=10。在“发现号”231、236航次及“流星号”（Meteor）42/2航次中，则采用基于二氧化碳红外检测的新开发系统开展总碳酸盐测定（Goyet与Snover, 1993；O'Sullivan与Millero, 1998）。该方法的精密度同样为0.2%相对标准偏差（RSD），测定时采用4mL样品环，平行样品数n=10。样品经0.45μm一次性无菌醋酸纤维素滤膜过滤后，置于经超纯水（MQ水）冲洗过的聚乙烯样品瓶中冷藏保存，直至船载现场分析。