WATER QUALITY ASSESSMENT OF LOS ANGELES RIVER WATERSHED

The Los Angeles River is an effluent-dominated water body during the dry season. The three waste water treatment plants (WWTP) including the Tillman, Burbank, and Glendale waste water treatment plants discharge the majority of the volume flowing in the LA River during the dry period. These WWTPs discharge nitrate, phosphate and other cations and anions. The water samples for chemical and physical analysis were collected to assess the recent pollutant deposition processes in response to extensive human activity in wet and dry seasons. The general trend of the results shows that the concentrations of anions are higher during the dry season than during the wet season. Anion concentration values (ppm) for anions in the dry season ranging 5.5-16,027 (Cl), 0-1.0 (F), 0-21(NO3), 0-1.6 (PO4), and 13.3-2,312 (SO4); whereas the values (ppm) for anions in the wet season ranging 3.4-5,860 (Cl), 0-0.66 (F), 0-17 (NO3), 0-0.67 (PO4), 7.9- 745 (SO4). Dry season concentrations values for trace metals were obtained with values (ppb) ranging 0.9-10 (Ni), 0.8-62 (Zn), 1-4 (As), 0-1 (Pb) and 0-3 (Se). As for the wet data trace metals in parts per billion ranging 0.001-0.008 (Ni), 0.000001-0.038 (Zn), 0.0016-0.016 (As), 0.00099-0.0058 (Pb), 0.000001-0.0093 (Se). The most likely sources for chlorides are the three WWTPs in the Sepulveda, Burbank, and Glendale area as well as the tidal effect in the region closer to the ocean. Nitrate sources can be from human activities including agriculture as well as WWTPs. In general the trend of concentrations for both anions and metals are higher during the dry season sampling than the wet period of the river watershed. Higher concentrations during the dry period may be attributed to the fact that the three WWTPs discharged the majority of the volume of water (75%) of the volume flowing in the LA River. On the other hand, the low concentrations during the wet period may be due to increase of water discharge in the rainy season.