QUALITY ASSURANCE/QUALITY CONTROL Maryland Department of Natural Resources followed specific procedures to ensure that the Mainstem component of the Chesapeake Bay Water Quality Monitoring Program design was properly implemented and managed with sufficient accuracy, precision and detection limits. Accuracy (closeness to the true value) of collected data was controlled and assured by proper use, calibration and maintenance of both field and laboratory equipment for the measurement of physical and chemical parameters. The procedures to control and assure the accuracy of field measurements involved the calibration of field instruments, the verification of calibrations, and equipment maintenance. Most of the details of how data acquired with YSI sondes were quality assured and quality controlled are described in the process description elements in the Lineage portion of this metadata record.
Daily quality control checks, which included the running of blanks and standards, were used to control and assure laboratory accuracy. Accuracy of Chesapeake Biological Laboratory, Nutrient Analytical Services Laboratory (CBL NASL) results was also assessed through DNR's participation in the Chesapeake Bay Coordinated Split Sample Program (CSSP) a split sampling program in which five laboratories involved in Chesapeake Bay monitoring analyze the coordinated split samples. CSSP was established in June 1989 to establish a measure of comparability between sampling and analytical operations for water quality monitoring throughout the Chesapeake Bay and its tributaries. DNR followed the protocols in the Chesapeake Bay Coordinated Split Sample Program Implementation Guidelines (EPA 1991) and its revisions. Split samples were collected quarterly. Results were analyzed by appropriate statistical methods to determine if results differed significantly among labs. If a difference occurred, discussions began regarding techniques and potential methods changes to resolve discrepancies.
ADDITIONAL COMMENTS
January 2018: When the dissolved oxygen sensor used at station CB5.1W was post calibrated, the measurement was high by 0.17 mg/l. There was no pycnocline at station CB5.2 and the above pycnocline and below pycnocline water samples were collected at 1/3 and 2/3 of total water column depth. A ship passed when sampling operations at station CB5.2 were conducted and surface conductivity readings changed by 900 micro Siemens/cm while on station. Surface and above pycnocline samples were collected from a single bottle at both station CB4.1C and station CB3.3C. Station CB3.1 surface conductivity shifted approximately 2,500 micro Siemens/cm during sampling operations.
February 2018: LI-COR measurements were not made at station CB5.1W because sea conditions were too rough. The 0.5m and 1.0m samples at station CB5.1W were collected from the same water bottle. The water quality sonde dissolved oxygen sensor was slow to stabilize at station CB3.1. The absence of a pycnocline at stations CB5.2 and CB5.1, led to above pycnocline and below pycnocline water sample collections at 1/3 and 2/3 of total water column depth at each location.
March 2018: There were no known attribute accuracy issues during March.
April 2018: A ship passed prior to sampling at station CB4.3C. The survey vessel drifted during operations at station CB4.2E and it was not possible to maintain the normal station depth. Surface conductivity changed during sampling at station CB5.3. Surface and 1.0m water samples were collected from a single bottle at each of the following stations: CB4.3E, CB4.3C, CB4.3W, CB4.2W, CB4.2C, CB4.2E, CB4.1E, CB4.1C and CB4.1W. There were no pycnoclines at station CB5.2 and station CB2.2 and above and below pycnocline samples were collected from 1/3 and 2/3 of total station water column depth. Rain fell the night prior to sample collection at stations CB2.1 and CB1.1. The sampling vessel drifted during operations at station CB4.1E and the sampling sonde/pump array struck bottom at 22m depth. Concern about touching bottom at station CB4.3E necessitated a bottom sample at 21m depth. Similar concerns resulted in a shallower than normal bottom sample at station CB4.1C.
May 2018: The cruise report noted heavy rainfall on 12-May-2018, an algal bloom, the preceding week, which covered the entire bay and an unusual flat calm. A bottom dissolved oxygen reading of 0.96 mg/l at station CB3.2 was noted. LI-COR readings were characterized as possibly unreliable. On 16-May-2018 the data sonde pH sensor response time was slow and the dissolved oxygen sensor readings slowly crept lower when below 1.0 mg/l. Station CB4.3E surface and 1m water samples were collected from the same depth. Station CB4.1E surface and above pycnocline water samples were collected from the same bottle. Since there was no pycnocline at station CB2.2, above pycnocline and below pycnocline samples were collected at 1/3 and 2/3 of total station water column depth.
June 2018: The first June cruise was conducted June 4-6. Due to issues with the sample refrigerator door 4-Jun-2018, samples were stored in the food refrigerator. A replacement sample refrigerator was installed 5-Jun-2018. Scoping is a term used to describe situations when strong currents and or winds make it difficult to maintain the water quality data sonde at a depth long enough for readings to stabilize. Scoping was noted at station CB4.1E. A slight H2S odor was noted in bottom water samples collected at stations CB4.1E and CB3.3C. Station CB4.1C 8m depth water temperature was double checked. Bottom and below pycnocline water samples at station CB2.2 were collected from the same bottle.
The second June cruise was conducted June 25-27. Meter scoping was noted at stations CB5.3 and CB5.2. The CB5.3 and CB5.2 surface and 1.0m water samples were collected at the same depth. Meter scoping at station CB4.4 prevented getting bottom water quality measurements at the 29m depth. An odor of H2S was observed in bottom water samples collected at stations CB4.4 and CB4.3W. Similarly, H2S odors were logged in below pycnocline and bottom samples at stations CB4.3E, CB4.3C, CB4.2C, CB4.1E, CB4.1C and CB3.3C. Sample freezer problems resulted in unfrozen samples on 26-Jun-2018 and 27-Jun-2018. A conductivity change was noted after the below pycnocline water sample was collected at station CB5.1. A ship passed prior to sample collection at station CB3.2. At station CB3.2, the sonde/pump sampling array touched bottom at 12 m and the surface and 1m sample waters were collected at the same depth. There was no pycnocline at station CB2.2 and above pycnocline and below pycnocline samples were collected at 1/3 and 2/3 of total station water column depth. The response time of the water quality sonde pH sensor was characterized as slow at stations CB2.1 and CB1.1.
July 2018: During the first July survey (July 9-11), hydrogen sulfide odors were noted in bottom and below pycnocline sample waters collected at stations CB5.1, CB4.4, CB4.3E, CB4.3C, CB4.2C, CB4.1E, CB4.1C and CB3.3C. Station CB5.3 dissolved oxygen results at 4m depth were double checked with a second meter. There was no pycnocline at station CB2.2 and the above pycnocline and below pycnocline water samples were collected at 1/3 and 2/3 of station total water column depth, respectively.
Water column measurements only (no pigment or nutrient samples) were collected the second July 2018 cruise (July 26 and 27), except at upper Bay stations CB1.1, CB2.1, CB2.2, CB3.1 and CB3.2. CB3.3E, CB3.3C and CB3.3W where nutrient and chlorophyll samples were collected to assess the impact of historic high flow and releases from Conowingo Dam. Approximately 20 gates of the Conowingo dam were open and water flowed through the gates at a rate of 400,000 cubic feet per second. There was lots of floating debris at stations CB2.1 and CB1.1 and the waters were completely fresh. Observations were made regarding heavy rainfall during the week preceding sample collection at stations CB1.1, CB2.1, CB2.2, CB3.1, CB3.2, CB3.3C, CB3.3E and CB3.3W. There was no pycnocline at station CB2.2 and above pycnocline and below pycnocline sample waters were collected from 1/3 and 2/3 of total station water column depth, respectively. Rain showers, during the night prior to sampling, were noted at stations CB3.3C, CB3.3E and CB3.3W. Surface water conductivity changed during the hydrocast at station CB3.3C.
August 2018: On the first survey (August 6-8), a slight hydrogen sulfate odor in bottom sample water was noted at station CB4.1C. Above pycnocline and surface samples were collected from different sample bottle at station CB4.1E. Lack of a pycnocline at stations CB2.1 and CB3.1 resulted in collection of above pycnocline and below pycnocline samples from 1/3 and 2/3 of total station water column depth, respectively. The sonde/pump sampling array hit bottom at 12m depth when sampling at station CB3.2 and the bottom sample was collected at 11m. Station CB3.2 dissolved oxygen results at 3m and 4m were double checked with a second meter. At station CB4.4, the sonde/pump sampling array hit bottom while collecting bottom water samples. During sampling operations at station CB4.4, at 10m depth, it was necessary to quickly bring gear aboard and move north to avoid a squall. The vessel returned to station 15 minutes later and resumed sampling at 10m.
During the second cruise (August 21, 22 and 24), the sonde/pump array hit bottom at 24m depth at station CB3.3C. When station CB4.1C was sampled, pH 3m results were double checked with a second sonde. Rain began falling during sampling operations at station CB4.1C. Surface and 1m samples were collected at the same depth at stations CB4.1C, CB4.1W, CB4.2W, CB4.3W and CB4.4. There was no pycnocline at station CB2.2 and above pycnocline and below pycnocline samples were collected at 1/3 and 2/3 of total water column depth, respectively. Station CB5.1 conductivity readings at 9m were unstable.
September 2018: Mainstem survey samples are, ideally, collected over the course of three consecutive days. A hurricane (Hurricane Florence), weather and schedule conflicts required the September cruise to be sampled outside this preferred window. Stations CB4.1C, CB4.1W, CB4.2C and CB4.2W were sampled 17-Sep-2018. Stations CB2.2 and CB2.3 were sampled 19-Sep-2018. Stations CB4.3C, CB4.3W, CB4.4, CB5.2 and CB5.3 were sampled 25-Sep-2018. A slight odor of hydrogen sulfate was noted at station CB4.1C. Meter scoping was an issue during station CB4.2C sampling and conductivity was unstable at 12m, 11m and 10m depths. Surface and 1m samples were collected at the same depth when stations CB4.1W, CB4.2C, CB4.2W, CB4.3C and CB4.3W were sampled. There was no pycnocline at station CB2.2 and above pycnocline and below pycnocline water samples were collected at 1/3 and 2/3 of total station water column depth, respectively. The below pycnocline sample at station CB3.2 was collected from the wrong depth and should have been collected at 6m depth. Station CB4.4 conductivity readings were unstable at 14m depth.
October 2018: The station CB4.4 below pycnocline sample should have been collected at 20m depth but was collected at 19m due to a shift in water quality data sonde readings.
November 2018: Post-survey calibration tests of the conductivity sensor, used for stations CB4.3C, CB4.2C, CB4.1C, CB3.3C and CB3.2, returned results 3,600 micro ohms/cm higher than the 24,280 micro ohms/cm standard. The issue was determined to be due to a bad dissolved oxygen sensor affecting conductivity/temperature sensor results. There were no pycnoclines at stations CB3.1 and CB2.1 and above pycnocline and below pycnocline samples were collected from 1/3 and 2/3 of total station water column depths. Stations CB3.1, CB2.2, CB2.1 and CB1.1 were sampled using a small boat and water samples were processed at the dock at Betterton.
December 2018: The station CB4.3C below pycnocline sample water should have been collected at 12m and the above pycnocline sample should have been collected at 6m. Station CB4.1C surface and above pycnocline water samples were collected from the same bottle. At both station CB2.1 and station CB1.1, slow responses of pH sensor, due to very cold water, were noted.