HOURLY AND SEASONAL TRENDS OF DISSOLVED TOTAL FE CONCENTRATIONS AT THE WINGFIELD PINES PASSIVE ACID MINE DRAINAGE TREATMENT FACILITY

Wingfield Pines is a passive acid mine drainage treatment facility operated by the Allegheny Land trust in Upper St. Clair, PA. Water is introduced to the system via a buried pipeline that transports contaminated water into a series of settling ponds beginning with pond 1 and ending when it empties into Chartiers Creek via the adjacent wetland. Samples were analyzed for total dissolved Fe using a Hach DR1900 portable spectrophotometer at the entrance to pond 1 (via pipeline) and the connection between pond 1 and pond 2 in March and again in July to discern differences to the efficiency of settling pond 1 based on hourly variation of water temperature and sunlight intensity during different seasons. Samples were collected at both sites in March, 2021 every hour over 13 consecutive hours along with bracketing samples collected the night prior to and the morning following the full sampling interval. Data from the entrance to pond 1 showed a pH range from 6.22-6.56 and total dissolved Fe range from 12.720mg/L-13.176mg/L with no apparent hourly trend. Data from the connection at pond 2 showed a pH range from 7.04-7.21 and total dissolved Fe concentrations of 0.615mg/L-2.531mg/L, with steady increase from pre-sunrise to the evening followed by a decrease at sunset. Samples collected at sunset the night before and following sunrise the morning after at the pond 2 connection were 2.570mg/L and 1.045 mg/L respectively, confirming the subsequent decrease in total dissolved Fe overnight. A second collection event occurred in July, 2021. The entrance to pond 1 had similar pH and total dissolved Fe to the March event with no hourly trend. The connection to pond 2 showed a pH range from 6.22-6.95 and dissolved total Fe ranged from 0.749mg/L-2.802mg/L. Total dissolved Fe showed no apparent trend at the pipeline entrance to pond 1 in all data sets. Total dissolved Fe reached a maximum at the pond 2 connection at 6pm just before sunset in March but reached a maximum at 1pm in July before a decrease and subsequent increase until sunset at 7pm. These trends are attributed to photoreduction causing an increase in dissolved Fe in both March and July and additional bacterial influence in July data when water is warm enough to sustain activity