Peace and Myakka River Water Quality Summary 2002 - Southwest ...

on the initial day of field work; the remaining stations were sampled over the followingtwo days.Water quality parameters monitored included: specific conductance, pH, temperature,dissolved oxygen (DO), total organic carbon (TOC), nitrate+nitrite nitrogen, ammonianitrogen, total ammonia+organic nitrogen (TKN), dissolved ortho-phosphate (PO 4 ), totalphosphorus (TP), chlorophyll a, color (PCU), total suspended solids (TSS), and turbidity(NTU).Hydrographic parameters (specific conductance, salinity, pH, temperature, and DO)were measured in the field using multi-probe Hydrolab or YSI instruments that werecalibrated at the beginning and end of each field day.Water samples were collected at a depth of 0.5m at each gaging station andtransported on ice to the analytical laboratory. Concentrations of dissolved orthophosphatewere determined using samples that were field-filtered, immediately followingcollection, through 0.45 µm membrane filters and stored on ice until analysis. Samplesused for chlorophyll analysis were filtered in the laboratory immediately followingsample delivery, using Gellman A/E (1 µm) glass fiber filters, and the filters andattached algal cells were stored frozen prior to chlorophyll extraction. All sampling,sample preservation and transport, and chain of custody procedures were performed inaccordance with an EPA-approved quality assurance plan and with existing state(FDEP) and regional (SWFWMD) quality assurance requirements. Chemical analyseswere performed by three laboratories (SWFWMD, FDEP, and EQL, Inc.), using EPAapprovedanalytical methods.Data quality was assessed and reported on a quarterly basis by SWFWMD staff (e.g.,CHEC 2000, 2001). The most significant issues involved the accuracy and precision ofa number of total nitrogen determinations made by the SWFWMD laboratory, using anew analytical method, during 1999. Data points affected by these QA concerns havebeen omitted from the analyses performed for this report. The greatest impact of theseomissions has been the creation of data gaps in the estimates of TN loads and yields(Table 3 and Fig. 4) for the 1999 water year.5