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mongolia

Water-Quality Sample Processing 2005

Tasks:

Environmental samples may support the biotic collections in several ways:

  • To process raw field samples for later analysis, as well as preliminary field analyses for building context in the field
  • QA/QC:
    -Field duplicates every 10 samples (every third lake or so)
    -Field blanks every 20 samples (every sixth lake or so)
    -Lab DOC blanks -- acidified DI water in 5 sample bottles for duration of time from fieldwork to analyses, at ambient temperature (done in 2004 already)

Procedure:

Collect raw water sample from each sampling site in 500-mL amber plastic bottle, for processing back on shore. From this 500-mL field-sample bottle:

Sample splitting:

  • Lay out materials on work table
  • Label subsample analyses bottles -- typically 6 for each sample (TP/TN, DIC-13, O-18 and D, cations, anions, and NO3/NH4/DOC).
  • Unfiltered (raw) water:
    -TP/TN: Shake sample, measure out 20 mL of raw water in graduated cylinder, and pour into 60-mL HDPE bottle. No preservation should be necessary if we digest sample in this bottle. (For carry-on baggage, to reduce chance of sample loss under low pressure.)
    -Insurance bottle: 60-mL amber PP bottle, for miscellaneous use -- TIC, TOC, SRSi, etc. (+biocide; could be filtered later, too...) (Too bulky!! Not enough room to get this extra sample for each site.)
  • Filter water with 60-mL syringe filter:
    -Rinse filter holder with DI water, insert 0.45-u filter, and screw closed. Fill syringe by pulling out plunger, hold finger on tip, and fill from top of syringe, leaving a bit of air. Put plunger back in (keeping finger on tip), invert, and squirt out any air from the syringe. Attach to filter holder by luer-lock connection.
    -Use first half of first syringe for rinsing syringe, filter, and bottles
    -13C and DIC: 20-mL glass vials, septa & crimped tops (+2 drops HgCl2)
    -Stable water isotopes (18O and D): 20-mL plastic scint vials, conical caps (no preservative)
    -Anions: 15-mL amber PP bottles (no preservative)
    -Cations: 15-mL clear PP bottles (+2 drops high purity HCl)
    -DOC, Nitrate: 60-mL amber PP or HDPE bottles (+6 drops H2SO4)
    -Note -- generally, 1 drop of concentrated acid (HCl, H2SO4, or HNO3) per 10 mL of sample is sufficient to lower pH to below 2.
  • Total water volumes and sample bottles per site (excluding "insurance" sample):
    -Unfiltered: 20 mL -Filtered: 130 mL -Amounts for field analyses: Probably another 50-100 mL? -Bottle & filter rinsing, etc. -- about 50 mL? -Total raw sample needed would be about 250-300 mL, and so a 500 mL field bottle was generally sufficient in 2004. A 250-mL bottle will work in a pinch if you're careful.

Sample field analyses (all done on raw, unfiltered water):

  • Field parameters
    -For every lake, and some rivers and springs: YSI readings (T, SC, pH, and DO) should be obtained in situ, although SC may need to be obtained by dilution of very-high SC samples.
    -For rivers and springs, miscellaneous quick sample stops -- just T, SC, and pH with smaller probes (when getting the YSI out was too cumbersome)
  • Field analyses -- when possible
    -Color -- with hand-held colorimeter
    -Cl field test
    -SO4 field test
    -Alkalinity &/or carbonate
    -Hardness (Ca+Mg)
    -Notes -- I did some of these analyses from time to time, out of curiosity, but they generally were not necessary, as we’ll use the results from the full lab analyses done on these samples, rather than these rough field analyses. I had little field kits for these variables the first sampling year (2004), but generally just used simple test strips the second year (2005) to save space -- though these test strips are not very good. Contrary to popular opinion, alkalinity does not have to be done in the field if you get a good crimp seal on the amber glass vial for a good DIC analysis. Knowing DIC, field T, and field pH is enough to back-calculate alkalinity if desired. I have a spreadsheet to do these calculations -- both to calculate alkalinity from DIC, and to calculate DIC from alkalinity, as well as to determine carbonate speciation (though this spreadsheet doesn’t take into consideration all possible ion pairs with other ionic species -- it considers only the carbonate species).

General Notes:

  • For our 2005 samples, I ended up having all stable isotopes (O-18, D, and C-13) run on the same filtered, but unpreserved, sample, collected in a 20-mL plastic scint vial. This seemed to work just fine, though it would be better to add biocide (I think) to preserve the C-13 component, as long as this wouldn’t impact the other isotopes.
  • Consequently, I had both DIC and DOC run on the 20-mL amber-glass sample bottle (filtered and preserved with HgCl2), as a colleague had an instrument that could easily to both. Values appear to be quite good.
  • We also did some duplicate DOC analyses on the water from the 60-mL amber plastic bottle, just to check. This is generally OK, but you need to correct the results for the DOC that the water can acquire from the bottle itself. This is done by making some acidified blanks to get an average value for the amount of DOC from the bottles, which is subtracted from the analyses done on actual samples. Because of this bottle contamination, this is not the best way to get DOC, but it will give good enough values for survey work -- and reduces the number of glass bottles needed (which are heavy and can break…). On the other hand, if all DOC is done on the 20-mL amber-glass vials anyway, then I’d use smaller bottles for NO3/NH4 analyses -- probably only 20-mL. It was sometimes difficult to filter enough water for the 60-mL bottles.

Equipment and supplies:

  • Bottles -- minimum per year (assume 2-3 samples per lake for 30 lakes, plus extra spring and river sites):
    - 10 -- field sampling bottles -- five 500-mL, and five 250-mL.
    - 100 -- 60-mL HDPE bottles for TP/TN samples
    - 100 -- 60-mL amber PP or HDPE for insurance samples
    - 100 -- 20-mL scint vials + conical caps for stable water isotopes
    - 100 -- 20-mL glass vials + septa + crimped tops for 13C and DIC
    - 100 -- 60-mL PP or HDPE bottles for cations/DOC/nitrates
    - 100 -- 15-mL amber PP bottles for anions
    - 100 -- 15-mL PP bottles for cations
  • So -- what was left in Mongolia last year:
    - 60 -- 60-mL HDPE bottles (TP/TN)
    - 60 -- 60-mL PP or HDPE bottles (DOC/nitrates)
    - 100 -- 20-mL scint vials + conical caps (18O and D)
    - 60 -- 20-mL glass vials + septa + crimped tops (13C and DIC)
  • Add on 8% for field duplicates, and 2% for field blanks = 10% extra!!
  • Bottles -- what I need to take in 2005 (minimum):
    - 10 -- field sampling bottles?? Five 500-mL, and five 250-mL?
    - 40 + 10 -- 60-mL HDPE bottles for TP/TN samples
    - (a few? + 10) -- 20-mL scint vials + conical caps for stable water isotopes
    - 40 + 10 -- 20-mL glass vials + septa + crimped tops for 13C and DIC
    - 40 + 10 -- 60-mL PP or HDPE bottles for cations/DOC/nitrates
    - 100 + 10 -- 15-mL amber PP bottles for anions
    - 100 + 10 -- 15-mL PP bottles for cations
  • Chemicals
    - H2SO4 (conc.) -- for DOC/nitrate (and for cations if you want…)
    - HCl, high-purity (for cations, as Emi wanted)
    - Biocide -- ZnCl? Zn acetate? CuCl? (for C13-DIC samples)
    - DI water for field blanks: 110 mL per blank sample (cations, anions, DOC/NO3 -- not feasible for isotopes). Say, we do 20 lakes, 4 samples per lake = 80 samples, plus misc. springs and streams, for about 100 total samples. So, 2% would be two blanks, for a total of 250 mL of DI water needed. Bring along about 2-4 L of DI, I'd guess. The rest is for rinsing of filter holders, bottles, etc.
  • General supplies
    - Label tape and sharpies
    - Stretchy bottle-sealing tape
    - Stick-on labels -- plastic? paper may be stickier…?
    - DI water -- 2 L minimum (for rinsing, and diluting high-SC samples or other samples, and for taking blanks)
    - Graduated cylinder (25 mL, plastic; maybe also 50 mL?)
    - Sample container (cooler?)
    - Field forms (--> booklet?), or templates, for QW samples (with QW-ID code)
    - Field forms for biotic samples, to relate to QW samples
  • Filtering and sample splitting
    - Two in-line Nalgene filter holders, with Luer-Lok adaptor
    - 60-mL syringes with Luer-Lok tips
    - 45 mm 0.45 µ membrane filters
    - Glass fiber pre-filters, perhaps
    - Filter forceps
    - Crimping tool for 13C vials
    - Kit box (tackle box)
  • Field analyses
    - YSI sonde, standards
    - Turner AquaFluor field fluorometer, solid standard
    - Hach colorimeter (simple wheel comparitor)
    - Hach Cl kit
    - Hach SO4 kit
    - Hach alkalinity kit (dropper bottle or titrator & color indicator)
    - Hach hardness kit (Ca+Mg)