Surface Water Chemistry Field Sampling

This protocol details the process for collecting and storing filtered water samples for the Biogeochemistry theme. Filtered water samples will be collected during regular sensor maintenance (AIMS Approach 1), distributed seasonal sampling (AIMS Approach 2), synoptic sampling (AIMS Approach 3), and the flow manipulation experiment (AIMS Approach 4). The approach to sampling water is described in general, as are the specific bottles, labels, filters/preservation approaches and sampling splitting for specific analyses. This protocol assumes you know where to sample. This protocol also does not cover ancillary field data parameters collected in real-time by sensors (e.g., dissolved oxygen, collected by a handheld sensor).

From this SOP, the following data types will be created: water anions, cations, ammonium, soluble reactive phosphate, dissolved organic carbon, dissolved organic matter, total suspended solids, alkalinity, and water isotopes. [AIMS rTypes: anions (ANIO), cations (CAIO), soluble reactive phosphate (SRPS), and ammonium (AMMO) together in Dissolved solutes (DISS). Dissolved organic carbon: DOCS; dissolved organic matter: DOMS; total suspended solids: TSSS; alkalinity: ALKA; water isotopes: WAIS]

Definitions and Variables¶

Key Terms

• Not applicable

Primary Data Values

• Anions (AIMS abbreviation ANIO): negatively charged dissolved material

  • Nitrate ($\text{NO}_3^-$), units: mg/L $\text{NO}_3$-N

  • Chloride ($\text{Cl}^-$), units: mg/L $\text{Cl}$

  • Bromide ($\text{Br}^-$), units: mg/L $\text{Br}^-$

  • Sulfate ($\text{SO}_4^{2-}$), units: mg/L $\text{SO}_4^{2-}$

• Cations (AIMS abbreviation CAIO): positively charged dissolved material

  • Calcium ($\text{Ca}^{2+}$), units: mg/L

  • Magnesium ($\text{Mg}^{2+}$), units: mg/L

  • Sodium ($\text{Na}^{1+}$), units: mg/L

  • Potassium ($\text{K}^{1+}$), units: mg/L

  • Silica ($\text{Si}$), units: mg/L

  • Ammonium ($\text{NH}_4^+$), units: ppb $\text{NH}_4$-N (AIMS abbreviation AMMO)

  • Soluble Reactive Phosphorus (AIMS abbreviation SRPS), units: ppb ($\text{PO}_4$-P)

  • Dissolved Organic Carbon (AIMS abbreviation DOCS), units: ppm

  • Dissolved organic matter fluorescence (AIMS abbreviation DOMS), units: RU

  • Total suspended solids (AIMS abbreviation TSSS), units: mg/L

  • Alkalinity (bicarbonate), units: mg/L

  • Water isotopes (AIMS abbreviation WAIS), units: ‰

Supplemental Data

• Not applicable

Safety Considerations¶

Field Safety Preparation

Follow any field precautions specific to your site or region. Always bring a personal water supply, sun protection (hat, sunscreen), animal protection (gaiters, bug spray), and field appropriate footwear. The greatest field safety concern during sample collection is the local weather conditions, which can change from the time of departure from the lab and arrival at the field site. We will use NEON’s contingency decision framework (Table 1) for water sampling for delays/rescheduling of weather related events impacting collection of surface water samples. Table 1: Potential field-related conditions and recommended actions.

Required Safety Precautions

This protocol requires handling acid to preserve samples. When using acid, use protective eyewear and gloves. Apply acid on a stable surface (e.g., table) using appropriate PPE and near a source of water for rinsing.

Personnel and Equipment¶

Checklist of equipment needed

• Labeled Sample Bottles (see Table 2 for specific size and numbers)

• Syringes (60 ml or 140 ml)

• Filters

  • Disposable luer-lok filters (Fisherbrand non-sterile 33mm, 0.45um Durapore PVDF membrane filters; for most chemistry samples)

    • Millipore Sigma Item SLHV033NS

  • Pre-ashed, weighed GF/F filters

    • VWR Catalog # 10199-602

  • 0.22 um PLUS filters

  • Reusable filter casings (for GF/F filters & cellulose acetate filters)

• Parafilm

• Cooler with ice packs

• Electric tape

• Sharpies

• Forceps or tweezers

• GPS

• Field Notebook/pencils

• Data sheet and clipboard

• Nitric Acid ($\text{HNO}_3$) bottle and dropper

• 6N Hydrochloric acid ($\text{HCl}$) bottle and dropper

• pH paper

• Waste receptacle

• Spare 2-3 4L bottles for back up sampling (if storms pop up)

• Spare 1-2L of deionized water for rinsing (as back up)

Additional Notes

• Estimated Time: The total time for collecting a full suite of samples will vary depending on the ease of filtering the water and the number of replicates needed. 30-60 minutes per sampling site is a good estimate.

• Allocation of effort (e.g., who does what, how many people needed to complete):

  • At least two people should be in the field together at all times for safety precautions. Assuming only two people are completing the sampling, use the following division of effort:

    • Person 1: filter water at 0.45 um (disposable filters) for anions, cations, SRP, and ammonium

    • Person 2: take unfiltered samples for TSS and isotopes first to minimize any benthic disturbance that may affect the sampling; filter water at 0.22 um (cartridge filters) for DOM first; filter water using GF/F filters (cartridge filter) for DOC

Standard Operating Procedures¶

Calibration and maintenance

• This is a collection/processing protocol and does not have a calibration step.

Preparing for Sampling

• This protocol involves collecting water samples for different approaches and analytes, all of which require different collection, labeling and preservation methods (Table 2).

• Prior to going into the field, ensure you have labels and bottles specific to the types of samples you’re collecting.

• Also ensure you have space in appropriate storage areas (e.g., freezers) to hold the samples until they can be sent to the university/lab that is responsible for processing.

Table 2: Water chemistry samples collected and associated preservation, containers, processing and approaches in AIMS.

Field Operations (step-by-step: what you do to maintain/collect samples in the field)

1. Note GPS coordinates (or site name), date, time, weather, collectors in field data sheet (printed on waterproof paper). Take a scan or photo of the datasheet after completing it, but before moving on to the next site.

2. At a predetermined specific sampling location, stand on the side of the stream (preferable; only possible in narrow channels) or in the mid-point (thalweg for wider channel) facing upstream.

   • If sampling multiple stream points, always sample moving from downstream to upstream to avoid contamination from upstream disturbance at downstream sampling locations.

3. Collect water into the syringe and rinse the syringe with stream water three times, dispelling water completely between rinses.

4. Collect a 60 ml syringe of water and attach a disposable filter

5. Push 5ml of water through the filter to rinse it, discarding the filtered water

6. Rinse the corresponding sample container (e.g., vial, bottle) with at least 5 ml of filtered water 3x. Cap the bottle and shake the filtered water to rinse the cap + bottle.

   • Fill anion, cation, SRP, and ammonium samples with water filtered using disposable filters using this method.

     • Ensure replicates are taken in the correct order (e.g., rep 1 first, rep 2 next, rep 3 last)

     • Fill the container to the appropriate level.

     • Make sure the label is clear and correct.

     • Immediately put on ice in the field.

     • Change filters when necessary; this will depend on the particle load in the water. If you are working on the same stream location, you can reuse a filter to fill multiple site bottles. Use a new filter in between different sites.

7. While Person 1 completes filtering for the disposable filtered samples, Person 2 should begin collecting unfiltered samples for TSS and water isotopes.

   • For TSS, triple rinse 1L dark bottle with stream water. Then fill to the shoulder with unfiltered stream water (these samples will be filtered in the lab). Be sure to sample upstream of your location and avoid any areas where sediment has been disturbed/entrained.

   • For water isotopes, rinse the glass bottles (with conical caps) three times. Fill and cap the bottle underwater with no headspace. Wrap cap/neck in parafilm and store in a dark place.

8. Person 2 can then filter samples with the 0.22um filter cartridge for the DOM Fluorescence samples. Repeat steps 2-5 above.

   • If you are doing a seasonal, synoptic, or drydown experiment sampling (Approaches 2-4), KEEP the filter which contains the microbial community from the water sample.

     • Detach the filter holder, add $\sim$10 ml of air to the syringe (be sure no water is in it), and then pump the air through the filter to slightly dry it. This makes removing the filter easier.

     • Using clean (dipped in ethanol) tweezers, carefully fold the filter in quarters and add to a pre-labeled PCR tube.

     • Store on dry ice or liquid nitrogen.

   • We do not collect microbial community samples for routine sensor maintenance checks (Approach 1), so the filter can be discarded.

9. Finally, Person 2 can filter samples with the GF/F filter cartridge for DOC.

   • Repeat steps 2-5 above to collect the DOC/TDN sample by filtering 60 ml into an opaque pre-labelled bottle.

10. Rinse the alkalinity bottle three times and fill with unfiltered water with no head space.

11. If additional preservation steps are required (e.g., acidification), return to that step after the collection of all samples.

Quality Assurance/Quality Control (including how to handle situations when something fails QA/QC)

• Complete reps in order (1 first, 3 last)

• Do all unfiltered samples first in case you stir anything up (isotopes, TSS)

• Sample upstream of where you have walked. If you disturb an area upstream, wait for particulates to settle out before taking samples.

• Read section 5.3 thoroughly.

Field or Lab datasheet/needed ancillary information

• Mark sample collection on the appropriate field data sheet.

YouTube Video Links

A series of videos were created to describe this protocol, which can be found here:

Sample Generated/Storage & Preservation¶

Processing and Preserving Samples

• See Table 2.

• Upon return to the lab:

  • Freeze anion & nutrient samples.

  • Acidify cations with nitric acid to 2%; store in cool/dark location

    • Acidify on the day of collection; it is fine to acidify in batch all of the samples collected at the end of the field day.

  • * Hold time is $\sim$2-3 months

  • Store isotopes in a dark place

  • Run DOM within 28 days.

    • Keep refrigerated, send on blue ice

  • Acidify DOC w/ 3 drops 6N $\text{HCl}$

    • Keep refrigerated. Ship on ice packs to ensure that samples stay cold but do not freeze.

    • Run within 28 days

  • TSS samples should be filtered in the lab within 48 hours of collection (24 hours preferred). Filters should immediately be placed in the drying oven and stored there until shipped.

• List of samples to dispose of once run:

  • DOC

  • MIMS

  • GHG

  • DOM

  • Alkalinity

  • If storage allows, please hold on to anions, cations, SRP, and ammonium [all frozen] and isotopes [shelf stable, in the dark].

Quality Assurance/Quality Control

• Complete reps in order (1 first, 3 last)

• Do all unfiltered samples first in case you stir anything up (isotopes, TSS)

• Sample upstream of where you have walked. If you disturb an area upstream, wait for particulates to settle out before taking samples.

• Read section 5.3 thoroughly.

Sample Transport back to the lab

• See Table 2.

Sample Tracking and Destination¶

Data Entry into sample Tracking System

• All samples collected must be recorded in the proper Sample Inventory sheet (microbial, biogeochemistry). The data inventory sheet tracks the following:

  • Sample ID, as defined by the Sample Naming SOP

  • Sample location

  • Variables measured (anion, cation, etc.)

  • Sample date and time

  • Date of shipment to processing lab

  • Confirmation of reception of shipment by processing lab

  • Storage location at current institution, if applicable

  • Additional notes

• Holding Timeline & Conditions: Reference information about processing in section 6.0

• Processing Lab Info (where are they ultimately headed?): Reference information about processing in section 6.0

Questions and Ownership¶

Point of contact for SOP

• Amy Burgin and Biogeochemistry Team, burginam@ku.edu

Contact for data ownership questions (if different than above)

• Same as above

Updates / Change Record¶

A running table of updates/changes made to the protocol

References¶