We collect water samples in high-density polyethylene collection bottles that have been acid-cleaned. All sampling bottles are soaked in 10% hydrochloric acid (HCl) for 3 days prior to use, rinsed with deionized water (DIW) and dried prior to sampling.
Each bottle is rinsed with ambient surface water three times, and dipped so that the mouth of the bottle is below the water surface when it is filled with surface water. During the exploratory phase of HCOOS (2007), samples were processed in the field and the monthly sampling effort was divided into thirds to minimize time between sample collection and processing because of the large number of sampling sites in the following order:
1st round: perimeter sites (OM1, OM2, OB, TM, RM1, RM2, RM3, OCN1, OCN2 and River)
2nd round: Stakes 1, 3, 6, 7, and 8
3rd round: Stakes 9, 13, 15, 16, and 18
Samples were stored on ice in coolers immediately after collection and dropped off at the to the field laboratory to be processed while next round was collected.
The entire water collection effort averaged five hours, and it is likely that temporal and spatial changes occurred within the water column over the time of sample collection. The current optimized sampling strategy is streamlined so that all samples can be collected at once, at neap tide (minimal change in tidal state during sampling); total sampling time is 1.5 to 2 hours. Samples are stored on ice in coolers immediately after collection and transported back to the lab at UH for processing.
Although our YSI measures turbidity, we also directly measure the amount of total suspended solids (TSS) collected on filters. We use 47 mm diameter, 0.2 µm pore size Pall GHP® filters and XX filter rigs.
- Soak GHP filters, filter screens and petri dishes for at least two days in 10% HCl then rinsed with DI water
- Pre-weigh the filters
- Place on plastic filter screens in plastic Millipore® (47 mm) diameter petri dishes and allow to dry
- Once samples are collected, pour into filter rigs and use negative vacuum pressure to pull the water through the filter.
- The particle loaded TSS filter is allowed to air dry for two days.
- Dry weight values are collected for 4 days; the sample is judged to be completely dry when variability between replicate daily weight values is less than 2%.
Amount of TSS = (particle loaded TSS filters) - (pre-weighed filters)
Filters are archived for subsequent geochemical analysis (link to TSS protocol page coming soon)
Filtrate generated from collection of TSS samples is collected in 2 x 100-mL splits in acid-cleaned polypropylene bottles. One split is acidified to pH 1 with trace-metal clean HCl and stored refrigerated (AR) and the other is stored filtered and frozen (FF). Filtrates are analyzed for dissolved inorganic and organic nutrients, DOC, trace metals, and other solutes, as summarized in Table 2.