Impact of Long-Term Reclaimed Water Irrigation on the Distribution of Potentially Toxic Elements in Soil: An In-Situ Experiment Study in the North China Plain

Abstract

The widespread use of reclaimed water has alleviated the water resource crisis worldwide, but long-term use of reclaimed water for irrigation, especially in agricultural countries, might threaten the soil environment and further affect groundwater quality. An in-situ experiment had been carried out in the North China Plain, which aimed to reveal the impact of long-term reclaimed water irrigation on soil properties and distribution of potentially toxic elements (As, Cd, Cr, Hg, Zn and Pb) in the soil profile as well as shallow groundwater. Four land plots were irrigated with different quantity of reclaimed water to represent 0, 13, 22 and 35 years’ irrigation duration. Pollution Load Index (PLI) values of each soil layer were calculated to further assess the pollution status of irrigated soils by potentially toxic elements (PTEs). Results showed that long-term reclaimed water irrigation caused appreciable increase of organic matter content, and might improve the soil quality. High soil organic matter concentrations conduced to high adsorption and retention capacity of the soils toward PTEs, which could reduce the risk of PTEs leaching into deep layers or shallow groundwater. Highest levels of Cr, Pb and Zn were observed at 200–240 cm and 460–500 cm horizons in plots. Longer irrigation time (35 years and 22 years) resulted in a decreasing trend of As, Cd, Hg, Pb and Zn in lower part of soil profiles (>540 cm) compared with that with 13-years’ irrigation years. Long-term reclaimed water irrigation still brought about increases in concentrations of some elements in deep soil layer although their content in soils and shallow groundwater was below the national standard. Totally speaking, proper management for reclaimed water irrigation, such as reduction of irrigation volume and rate of reclaimed water, was still needed when a very long irrigation period was performed.

Assessment on micronutrient concentration after reclaimed water irrigation: A CASE study in green areas of Madrid*

“…The largest contribution of Zn by reclaimed water was responsible for the highest concentration of this element in soils (Table 2), which became significantly higher in PEMA_RW. The obtained difference of Zn Soil between PEMA_DW and PEMA_RW after 15 years (2.6 mg kg −1 ) was in accordance with Gu et al (2019), who reported an increase of 1.98 mg kg −1 of Zn in soils after 13 years of reclaimed water irrigation. Roca, Pazos, & Bech (2007) concluded that Zn (DTPA) remained adsorbed in soil without vertical displacement decreasing its bioavailability, which could explain the observed normal Zn concentration in cedar leaves in these study plots (Table 3).…”

Environmental Risk Assessment of Metals in the Volcanic Soil of Changbai Mountain

“…Because the samples were taken from forest soil, the organic matter content was high [49]. Because organic matter has a high affinity for metals [50], these results indicate that the soil has a strong ability to accumulate metals [51]. Volcanic glass and phosphate retention are important indicators of volcanic soil properties [52].…”

Integrative Effects of Treated Wastewater and Synthetic Fertilizers on Productivity, Energy Characteristics, and Elements Uptake of Potential Energy Crops in an Arid Agro-Ecosystem

“…), and, if applied to crops, can fulfill the plant nutrient requirement and decrease the use of synthetic fertilizers. Additionally, the old cultivated soil (L1) resulted in better growth and biomass traits compared to the virgin soil (L2 and L3) due to the higher organic matter and the contents of N, P, and K. The use of TWW for irrigation improves soil fertility and the physical and chemical properties [44][45][46] and could provide OM and nutrients to soils [17], thus improving crop production [47]. Macro-and trace-elements are equally important to plants and play multifarious roles in their growth and development.…”

“…Hence, the use of TWW for irrigation improves soil fertility and the chemical and physical properties of soil [44][45][46], and can provide soils with OM and nutrients (N, P, K, Ca, Mg, B, Zn, Cu, Mn, etc. ), thus improving crop production [17,47,54,55,59,61,62]. Wang et al [74] recorded a higher yield of wheat (Triticum aestivum L.), maize (Zea mays L.), millet (Pennisetum glaucum L.), apples (Malus domestica), and rapeseed (Brassica napus L.) when irrigated with TWW.…”