Environmental assessment of the impact of sodium-containing superabsorbent polymers on soil water dynamics: A review

Abstract:

Agriculture is facing acute water scarcity as a consequence of climate change, which necessitates a shift toward adopting sustainability‑oriented practices in crop production. One of the key pillars of such sustainability is reducing irrigation water use, which can be achieved by adopting soil amendments that enhance the soil’s ability to retain moisture (soil water). Sodium containing superabsorbent polymers (SAPs) have been found to influence soil water retention but their full range of effects on soil water movement and long term environmental impacts is not fully understood, and, hence, they are not widely employed on a large-scale scale. This research holds great significance as it offers a comprehensive overview of the mechanisms behind the impact of these polymers on permeability, water retention, infiltration, and evaporation, helping farmers and researchers choose the best polymer for their soil and environment, ultimately contributing to improved water use efficiency and agricultural productivity in arid and semi-arid areas. Selected studies demonstrated that adding SAPs at varying concentrations (0.05% - 2500 mg kg^-1) achieved significant increases in maximum water holding capacity (WHC_max) ranging from 34.9% to 205%, and reduced erosion rates by up to 99.57%; however, effects varied based on polymer type (PAA loses effectiveness over time, whereas PAM remains stable, or composites provide better balance), application concentration, and soil properties, as sodium alginate hydrogel and composite polymers exhibited superior balance between water retention and permeability. The selection of the optimal polymer depends on soil type and environmental conditions, and the research emphasizes the necessity of long-term field studies to assess sustainability and environmental impacts, develop unified mathematical models, and evaluate the economic feasibility of local applications.