Changes of Soluble Nickel and Arsenic in Receiving Water with Rainfall-Runoff Inflow

Rainfall-runoff is the main source of pollution in the urban water environment. This study investigated the dynamic changes of soluble Nickel (Ni) and Arsenic (As) in the receiving water body after the rainfall and runoff of the Meishe River in Haikou. Field sampling and indoor analysis were used. Results revealed that the solid-liquid partitioning of Ni and As in the receiving water body is directly disturbed by the inflow of rainfall-runoff. The main source of the input is the suspended state, and the input of the dissolved state is smaller. The specific performance is as follows. Before the rainfall-runoff flows into the receiving water body, the ratio of soluble Ni and As to the total content reaches 55.67% and 94.77%, respectively. After the rainfall-runoff flows in, a series of dynamic changes of Ni and As occur in the receiving water body. The proportion of soluble Ni and As at the outlet decreases significantly and changes dramatically, reaching 20.97% and 76.92% of the total content, respectively. The proportion of soluble Ni and As in the downstream of the drainage outlet also decreases to a certain extent, reaching 47.23% and 88.38%, respectively. The data under different rainfall scenarios indicate that the long dry period, when the rainfall is less than 10 mm, is the main factor affecting the dynamic changes of soluble Ni and As. Furthermore, the long dry period, along with the peak time, and magnitude of the rain intensity are the major influencing factors of the response time and degree of soluble Ni and As to rainfall-runoff, when the rainfall amount ranges from 10-30 mm. The peak time of rainfall intensity is the main factor affecting the dynamic change of soluble Ni and As in the receiving waters when the rainfall amount is above 30 mm. The effects of rainfall-runoff on the soluble Ni and As in the receiving water are different. When the dry period is short and the maximum rainfall intensity is high, in receiving water, soluble As is less affected by rainfall-runoff, while soluble Ni is significantly affected.