Abstract
Phytoremediation has been widely used and is considered an environmentally friendly and efficient method for mitigating nitrogen (N) and phosphorus (P) loads. However, the technique is rarely employed in the Ningxia irrigation area, which suffers from serious N and P pollution. To investigate ways of protecting the aquatic environment in this region, we conducted in-situ experiments along an agricultural ditch in 2014 and 2015. During the pre-experiment in 2014, five single species floating-bed systems (Zizania latifolia, Oryza sativa, Ipomoea aquatica, Lactuca sativa and Typha latifolia) and one multi-species floating-bed system with three replicates were evaluated over about two months. I. aquatica performed best with respect to biomass accumulation and nutrient storage among all plant systems. Multi-species system was not superior to single species systems: 42% and 37% of the N and P storage in the multi-species system were achieved by I. aquatica. In the formal experiment during 2015, I. aquatica was tested again and performed excellently with respect to biomass production (1.06 kg/m2), N (27.58 g/m2) and P (2.34 g/m2) uptake. Thus, this study demonstrated that I. aquatica could be used to reduce N and P loads under saline and alkaline conditions in the Ningxia irrigation area.
Highlights
Agricultural non-point sources are regarded as important contributors to elevated nitrogen (N) and phosphorus (P) pollution in surface waters; which mainly caused by excessive application and the low use efficiency of fertilizers and pesticides in agricultural ecosystems[1,2,3,4,5]
Many plant species have been used for N and P removal, including Acorus calamus, Canna indica, Eichhornia crassipes, Ipomoea aquatica, Lactuca sativa, Lythrum salicaria, Oenanthe javanica, Oryza sativa, Phragmites australis, Sagittaria sagittifolia, Thalia dealbata, Typha latifolia and Zizania latifolia[25,26,27]
The study reported that the removal rates of total nitrogen (TN) and total phosphorus (TP) could reach 64% and 58% in a vegetated constructed ditch, and that C. indica and O. javanica exhibited higher nutrient storage than other plant species
Summary
Agricultural non-point sources are regarded as important contributors to elevated nitrogen (N) and phosphorus (P) pollution in surface waters; which mainly caused by excessive application and the low use efficiency of fertilizers and pesticides in agricultural ecosystems[1,2,3,4,5]. The consumption of fertilizer increased from 0.23 million tonnes in 1978 to 1.07 million tonnes in 2012 and pesticides from 1.6 kilotonnes to 8.1 kilotonnes, respectively[34] This region is characterized by serious soil salinization and alkalization due to low precipitation (180– 220 mm) and high evaporation (1000–1550 mm), and agricultural irrigation engineering almost relies on the Yellow River. According to the environment bulletin in recent years, the water quality of agricultural ditches is identified as being at “dangerously high levels” generally, which is mainly due to the high permanganate index, and high concentrations of ammonia nitrogen and TP36. These problems need to be addressed with proper measures. Target plant species were evaluated based on their potential for biomass accumulation and nutrient storage
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