ISO 15587的这一部分规定了使用硝酸作为消解剂从水样中提取微量元素的方法。该方法适用于悬浮固体浓度小于20g/l且以碳表示的总有机碳（TOC）浓度小于5g/l的所有类型的水。 硝酸消化法是经验性的，不一定能完全释放元素。然而，对于大多数环境应用，结果符合目的。 硝酸消化适用于以下物质的释放:Al*、As、B、Ba*、Be*、Ca、Cd、Co、Cr*、Cu、Fe*、Hg、K、Mg*、Mn、Mo、Na、Ni、P、Pb、Se、Sr、Tl、V*、Zn（星号表示与ISO 15587-1中规定的王水消化法相比，回收率可能较低）。只有当样品在消解后立即稳定时，它才适用于Ag的释放。硝酸消化不适用于Sb、Sn和难熔化合物如SiO2、TiO2和Al2O3的消化。 该方法是通用的，并且可以使用多种设备实施，条件是消化组合物不变，消化温度是已知的，并且消化持续时间与该温度一致。

This part of ISO 15587 specifies a method for extracting trace elements from a water sample using nitric acid as a digestion agent. The method is applicable to all types of waters with a suspended solids concentration of less than 20 g/l and a total organic carbon (TOC) concentration expressed as carbon of less than 5 g/l. The nitric acid digestion method is empirical and it might not necessarily release elements completely. However, for most environmental applications the result is fit for purpose. Nitric acid digestion is suitable for the release of: Al*, As, B, Ba*, Be*, Ca, Cd, Co, Cr*, Cu, Fe*, Hg, K, Mg*, Mn, Mo, Na, Ni, P, Pb, Se, Sr, Tl, V*, Zn (asterisk indicates a possible lower recovery compared to the aqua regia digestion method specified in ISO 15587-1). It is suitable for the release of Ag only if the sample is stabilized immediately after digestion. Nitric acid digestion is not suitable for Sb, Sn and for the digestion of refractory compounds such as SiO ₂, TiO₂ and Al₂O₃. The method is generic and may be implemented using a wide variety of equipment provided the digestion composition is unchanged, the digestion temperature is known, and the digestion duration is in accordance with this temperature.