Influences of stormwater concentration infiltration on soil nitrogen, phosphorus, TOC and their relations with enzyme activity in rain garden.

Abstract

Rain garden is a typical facility with many applications in urban low impact development (LID). It plays an important role in regulating runoff water quantity and quality. Two rain gardens with the discharge ratios of 20:1 and 15:1 were used as studied facilities. Seven soil sampling events were conducted from April 2017 to February 2019 to study the influences of stormwater concentration infiltration in rain gardens on soil nitrogen (N), phosphorus (P) and TOC and their relations with enzymes. The results showed that the contents of soil TN and NO2-N\xa0+\xa0TON in gardens gradually decreased with time, while those of NH3-N and TP increased with time. The content of NO3-N varied greatly with time, and there was no obvious rule. TOC increased first and then decreased. Vertical distributions of N, P and TOC showed that the contents of NH3-N, NO2-N\xa0+\xa0TON and TN at 0-50\xa0cm were high, so the upper soil was the sensitive area to the influence of stormwater concentration infiltration in rain gardens. The content of NH3-N decreased gradually with the increase of soil depth, but those of NO3-N and TP increased with the soil depth. Therefore, NO3-N and TP migrated down with water infiltration in soil, and preventing NO3-N and P leaching was critical for effective N and P removal though rain gardens. Soil urease (SU), sucrose (SS), protease (SP) and acid phosphatase (SAP) had a good linear relationship with N, P and TOC, and R2were all greater than 0.5.