酸化过程对海洋沉积物中有机碳同位素分析的影响

Acid treatment effects on the carbon stable isotope values of marine sediments

海洋沉积物中有机碳同位素(δ13C)可以示踪海洋生态系统中有机质来源,对环境研究具有重要意义。分析沉积物中有机物的δ13C,需要对样品进行酸化,以去除无机碳的影响。由于不同来源的沉积物中无机碳的含量和组份存在差异,需要针对样品性质,优化酸化处理过程。本研究分别选取了无机碳含量不同的温带与热带河口、海湾沉积物样品,比较了3种不同酸化过程对有机物δ13C分析的影响。研究结果表明:方法1(酸洗法)中6%H_2SO_3和1mol/L H_3PO_4对无机碳含量较高的热带河口、海湾样品去除效率较低,而2mol/L HCl去除无机碳酸盐的效果较理想。方法2(酸蒸法)并不适用于无机碳含量较高的热带河口、海湾样品;而对于无机碳含量相对较低的温带河口、海湾样品,9h酸蒸较为适宜。方法3(非原位酸洗)的结果较方法1和方法2偏正,表明其对含13C丰富的有机组分破坏较小,且方法3中残留的酸对δ13C的分析没有影响。因此,方法3是去除海洋沉积物中无机碳较理想的方法。

Carbon stable isotope ratio（δ13 C）has been regarded as an important factor tracing the organic material sources in marine ecosystem.Prior to analysis,samples have to be decarbonated.Inorganic carbon content and component are different in different marine sediments,and appropriate decarbonate methods should be chosen to get exact results.This study compared the effects of three acid treatments onδ13C values during the decarbonation of estuarial and bay sediments with different inorganic carbon content.The results showed that for the first method（rinse method）,6% H2SO3 and 1mol/L H3PO4 could not remove inorganic carbon in high inorganic carbon content samples collecting from tropical estuarial and bay completely,while 2mol/L HCl could remove inorganic carbon in all marine sediments completely.The second method（fumigation method）is not suitable for sediment samples with high inorganic carbon content from tropical estuarial and bay,but could be used for sediments with lower inorganic carbon content,and it showed that 9his the best fumigate time.δ13 C values obtained from the third method（non-capsule method）showed more positive values compared to the other two methods,indicated that the third method did not damage the 13 C enriched materials.Also the residual acid showed not impact theδ13C values in the third method.The third method is confirmed as the most appropriate acid treatment for decarbonation of marine sediments.