Nutrients in porewater of sediment profile M42/2_397-1

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Discovery 222（A航段）及226航次的科考船上完成，采用比色法（colourmetric methods），参照Johnsson等（1987）的研究方案，使用4mL进样环（sample loop），方法精密度为0.2%相对标准偏差（Relative Standard Deviation, RSD，n=10）。在Discovery 231、236及Meteor 42/2航次中，采用一套基于二氧化碳（CO₂）红外检测的新研发系统开展总碳酸盐测定，相关方法源自Goyet与Snover（1993）以及O'Sullivan与Millero（1998）的研究；该方法同样采用4mL进样环，其精密度亦为0.2%相对标准偏差（n=10）。所有样品均经0.45μm一次性无菌醋酸纤维素滤膜过滤，随后置于经超纯水（MQ-water）冲洗后的聚乙烯瓶中冷藏保存，直至完成船上分析。