In the perennial river, environmental base flow, associated with environmental flow, is the base flow that should be maintained within the river channel throughout the year, especially in the dry season, to sustain basic ecosystem functions and prevent the shrinkage or discontinuity of a river. The functions of environmental base flow include eco-environmental functions, natural functions, and social functions. In this study, we provided a method based on these functions; this method estimated the function values per unit area, introduced the scarcity coefficient, multiplied by the corresponding water area, and summed over to quantify the value of environmental base flow from 1973 to 2015 in the Wei River Basin, the largest tributary of the Yellow River in Northwest China. We observed that there was a positive correlation between the total value of environmental base flow and its water yield, whereas this outcome was completely different in the benefit per unit discharge of environmental base flow, which was closely associated with the shortage of environmental base flow. This method can thus present the considerable value of environmental base flow in monetary terms in a simple and effective way and lay the foundation for further reasonable protection levels of environmental base flow.

Rain gardens have recently been studied as important low-impact development (LID) facilities that play a critical role in runoff volume reduction and pollutant purification. Approximately 16–40 rainfall events were monitored from March 2011 to October 2017 in order to determine the running effect of three rain gardens with respect to runoff volume reduction and pollutant purification. In particular, running fate analysis of rain gardens is the key focus in this study. Combined analyses revealed three key points. Firstly, performance assessment demonstrated that rain gardens effectively cut inflow volumes through the filter media; when the confluence area ratio was 6:1–20:1 (confluence ratio = roof area or road/garden area) and the rainfall was approximately 2.8–39.9 mm, the runoff volume reduction rate ranged from 9.8% to 100.0%. However, the average annual runoff reduction rate presented an initially increasing and then gradually decreasing trend with monitoring time. Secondly, according to water quality data in 54 rainfall events, the annual average concentration removal rate of NH₄⁺-N was relatively good, but generally decreased with monitoring time. The concentration removal rate of NO₃⁻-N and total phosphorus (TP) is unstable; however, the removal rate of total suspended solids (TSS) is better than that of total nitrogen (TN). Combined with runoff reduction, the pollutant load reduction by rain gardens is greater than 50%, although this decreases with increasing monitoring time. Thirdly, through the study of 7-year running effect on runoff reduction and pollutant purification, the “three-stage purification (TSP) concept” (periods of purification growth, stability, and attenuation) with respect to pollutant load reduction processes was finally proposed, and a curve chart was drawn for pollutant load reduction and rain garden operating fate (the “P–F” curve chart).

This study investigated the removal of cadmium (Cd) and lead (Pb) from the soil through phytoremediation using ryegrass combined with chelating agents. Soil leaching experiments were employed to determine the extraction efficiencies of chelating agents, including ethylenediaminetetraacetic acid (EDTA), citric acid (CA), sodium glutamate tetra acetate (GLDA), oxalic acid (OA), and diethylenetriaminepentaacetic acid (DTPA) on Cd and Pb. Soil pot experiments were conducted to determine the effects of five different chelating agents—GLDA, EDTA, DTPA, CA, and OA—on the growth of ryegrass and the enrichment of Cd and Pb. The main findings were as follows: (1) the extraction efficiencies for Cd and Pb in soil were found to be GLDA > EDTA > DTPA > CA > OA and EDTA > DTPA > GLDA > CA > OA, respectively. (2) The aminopolycarboxylic acid class of chelating agents significantly reduced Cd and Pb contents in the weak acid extractable and reducible states in the studied soil, yet were less effective in the extraction of their residue state. Using chelating agents increased the proportion of residual heavy metals while reducing those in the weak acid extractable and reducible states in the soil, thereby mitigating the harmful effects of these heavy metals on the soil ecology.