Soil phosphorus dynamics following land application of unsaturated and partially saturated red mud and water treatment residuals

Interception of fertile soil phosphorus leaching with immobilization materials: Recent progresses, opportunities and challenges

The non-point source pollution induced by phosphorus (P) leaching from fertile soils is accelerating the eutrophication phenomena in aqueous ecosystems. Herein, to alleviate and intercept the P leaching from the fertile soils, diverse P immobilization materials (PIM) which can transform labile P into stable P via a range of physicochemical and biological interactions have been adopted and received increasing research interest. However, the remediation mechanisms of different PIMs were complex and vary with soil properties and PIM application methods. In this review, the P fraction and mobility characteristics of different fertile soils were first introduced. Then, three kinds of PIM including inorganic materials (e.g., clay minerals and red mud), organic materials (e.g., polyacrylamide), and composites (e.g., modified biochar) applied in soil P leaching interception were concluded. The key factors (i.e., soil pH, soil texture, organic matter content and variable soil moisture) influencing PIM performance and potential PIMs used for reducing soil P leaching were also introduced. Current review can favor for proposing more suitable and insightful strategies to regulate the fertile soil P and achieve the dual goals of improving the crop land quality and yield, and preventing agricultural non-point source pollution.

Comprehensive Application Technology of Bauxite Residue Treatment in the Ecological Environment: A Review

The emission of bauxite residue continues to grow with the increase of alumina production capacity, along with the large amounts of bauxite residue currently stored in stockpiles. The exposed problems of high yield, strong alkalinity, low comprehensive utilization rate, and threats to the ecological environment are becoming increasingly prominent. With the strict requirements of environmental protection, improving the comprehensive utilization rate of bauxite residue and bulk consumption of bauxite residue has become an urgent issue to be solved. A large number of researchers have conducted in-depth investigations into the application of bauxite residue over a wide range, and this paper summarizes its application in the environment in recent years, providing guidance for the high value and harmless application of bauxite residue, which can help reduce environmental pollution and human life and health hazards caused by bauxite residue.

Estimating dissolved phosphorus losses from legacy sources in pastures: The limits of soil tests and small-scale rainfall simulators

A legacy of using P fertilizers on grazed pastures has been enhanced soil fertility and an associated increased risk of P loss in runoff. Rainfall simulation has been extensively used to develop relationships between soil test P (STP) and dissolved P (DP) in runoff as part of modeling efforts scrutinizing the impact of legacy P. This review examines the applicability of rainfall simulation to draw inferences related to legacy P. Using available literature, we propose a mixing layer model with chemical transfer to describe DP mobilization from pasture soils where readily available P in the mixing layer is rapidly exhausted and contact time controls DP concentrations responsible for subsequent DP mobilization. That conceptual model was shown to be consistent with field monitoring data and then used to assess the likely effect of rainfall simulation protocols on DP mobilization, highlighting the influence of soil preparation, scale and measurement duration, and, most important, hydrology that can facilitate the physical transport of P into and out of surface flow. We conclude that rainfall simulation experimental protocols can have severe limitations for developing relationships between DP in runoff and STP that are subsequently used to estimate legacy P contributions to downstream water resources.