Table 6.1: PRESERVATION and HOLDING TIMES for TIDAL and NONTIDAL PARAMETERS WQa Nontidal WQb Maximum Maximum Preservation Holding Preservation Holding Time Parameter Time Total dissolved phosphorus Freeze 28 days Cool, 6°C 28 days ≤ –20°C ≤ Dissolved orthophosphate Freeze 28 days Cool, 6°C 48 hrs. ≤ –20°C ≤ Particulate phosphorus Freeze 28 days Freeze, 28 days ≤ –20°C ≤ –20°C (filters) Nitrite Freeze 28 days Cool, 6°C 48 hrs. ≤ –20°C ≤ Cool, 6°C, and ≤ Nitrate + nitrite Freeze 28 days 28 days ≤ –20°C to pH<2 Cool, 6°C and ≤ Ammonia Freeze 28 days 28 days ≤ –20°C H2SO4 to pH<2 Total dissolved nitrogen Freeze 28 days Cool, 6°C 28 days ≤ –20°C ≤ Particulate nitrogen Freeze 28 days Freeze, 28 days ≤ –20°C ≤ –20°C (filters) Particulate carbon (filters) Freeze 28 days Freeze, 28 days ≤ –20°C ≤ –20°C Dissolved & total organic Cool, 6°C and ≤ Freeze 28 days 28 days ≤ –20°C carbon H2SO4 to pH<2 Chlorophyll a / Pheophytin Freeze 28 days Freeze, 28 days ≤ –20°C ≤ –20°C (filters) Suspended solids, Total Freeze 28 days Not Applicable ≤ –20°C − and Fixed Field filters – Suspended solids, Total & Cool, 6°C 7 days Cool, 6°C 7 days ≤ ≤ Fixed Water samples – Suspended Sediment Not Applicable Cool & Dark 120 days − Concentration Silicates Cool, 6°C 28 days Cool, 6°C 28 days ≤ ≤ Cool, 6°C and ≤ Not Total Phosphorus H2SO4 to pH<2. 28 days – Applicable Or freeze Cool, 6°C c Not ≤ Nitrogen 28 days – Applicable or freeze Not Cool, 6°C, and ≤ Total Kjeldahl Nitrogen 28 days – Applicable H2SO4 to pH<2
Table 6.1: PRESERVATION and HOLDING TIMES for TIDAL and NONTIDAL PARAMETERS Parameter WQa Nontidal WQb Preservation Maximum Holding Time Preservation Maximum Holding Time Total dissolved phosphorus Freeze ≤ –20°C 28 days Cool, ≤ 6°C 28 days Dissolved orthophosphate Freeze ≤ –20°C 28 days Cool, ≤ 6°C 48 hrs. Particulate phosphorus (filters) Freeze ≤ –20°C 28 days Freeze, ≤ –20°C 28 days Nitrite Freeze ≤ –20°C 28 days Cool, ≤ 6°C 48 hrs. Nitrate + nitrite Freeze ≤ –20°C 28 days Cool, ≤ 6°C, and to pH<2 28 days Ammonia Freeze ≤ –20°C 28 days Cool, ≤ 6°C and H2SO4 to pH<2 28 days Total dissolved nitrogen Freeze ≤ –20°C 28 days Cool, ≤ 6°C 28 days Particulate nitrogen (filters) Freeze ≤ –20°C 28 days Freeze, ≤ –20°C 28 days Particulate carbon (filters) Freeze ≤ –20°C 28 days Freeze, ≤ –20°C 28 days Dissolved & total organic carbon Freeze ≤ –20°C 28 days Cool, ≤ 6°C and H2SO4 to pH<2 28 days Chlorophyll a / Pheophytin (filters) Freeze ≤ –20°C 28 days Freeze, ≤ –20°C 28 days Suspended solids, Total and Fixed – Field filters Freeze ≤ –20°C 28 days Not Applicable − Suspended solids, Total & Fixed – Water samples Cool, ≤ 6°C 7 days Cool, ≤ 6°C 7 days Suspended Sediment Concentration Not Applicable − Cool & Dark 120 days Silicates Cool, ≤ 6°C 28 days Cool, ≤ 6°C 28 days Total Phosphorus Not Applicable – Cool, ≤ 6°C and H2SO4 to pH<2. Or freeze 28 days Nitrogen Not Applicable – Cool, ≤ 6°C c or freeze 28 days Total Kjeldahl Nitrogen Not Applicable – Cool, ≤ 6°C, and H2SO4 to pH<2 28 days
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