N and P in Runoff Water From Residential Landscapes in California.

Lawns and other planting covers are an important component of most urban landscapes. Use of N and P fertilizers around residential homes may cause contamination of runoff water by nitrate, phosphate and other N and P forms. This non-point source pollution may directly contribute to water quality impairment of urban surface streams and estuaries. To understand the dynamics and patterns of N and P loadings via urban runoff, we monitored levels of nitrate, phosphate, total-N and total-P, along with other water quality parameters, in runoff water from 8 neighborhoods in California for over two years. Four of the sampling sites were located in Sacramento County (Northern California), and 4 in Orange County (southern California). At each site, runoff water from 200-500 single-family homes was collected in a grab sample fashion at the storm drain outfall. Water samples were collected biweekly under dry weather conditions or immediately after a rain storm. Data were analyzed by considering spatial and temporal effects, including a monthly effect, as well as interactions with total suspended solids, total organic carbon, and sampling conditions (dry vs. storm).  This presentation will discuss the main findings of this study.