『Abstract
Incidental losses of dissolved reactive phosphorus (DRP) to a
surface waterbody originate from direct losses during land application
of fertilizer, or where a rainfall event occurs immediately thereafter.
Another source is the soil. One way of immobilising DRP in runoff
before discharge to a surface waterbody, is to amend soil within
the edge of field area with a high phosphorus (P) sequestration
material. One such amendment is iron ochre, a by-product of acid
mine drainage. Batch experiments utilising two grassland soils
at two depths (topsoil and sub-soil), six ochre amendment rates
(0, 0.15, 1.5, 7.5, 15 and 30 g kg-1 mass per dry weight
of soil) and five P concentrations (0, 5, 10, 20 and 40 mg L-1)
were carried out. A proportional equation, which incorporated
P sources and losses, was developed and used to form a statistical
model. Back calculation identified optimal rates of ochre amendment
to soil to ameliorate a specific DRP concentration in runoff.
Ochre amendment of soils (with no further P inputs) was effective
at decreasing DRP concentrations to acceptable levels. A rate
of 30 g ochre kg-1 soil was needed to decrease DRP
concentrations to acceptable levels for P inputs of ≦10 mg L-1,
which represents the vast majority of cases in grassland runoff
experiments. However, although very quick and sustained metal
release above environmental limits occurred, which makes it unfeasible
for use as a soil amendment to control P release to a waterbody,
the methodology developed within this paper may be used to test
the effectiveness and feasibility of other amendments.
Keywords: Phosphorus; Adsorption; Ochre; Water quality』
1. Introduction
2. Materials and methods
2.1. Ochre and soil collection and analysis
2.2. Physical characterisation of the soil and ochre
2.3. pH, lime requirement, C/N ratio and background nutrient
and metal status of soil and ochre
2.4. Batch experiment with soil and ochre amendment
2.5. Data analysis
3. Results and discussion
3.1. Physical characterisation of soil
3.2. STP, pH and C/N ratio
3.3. Plost and Prunoff
3.4. Metal mobilisation during batch experiments
4. Conclusions
Acknowledgements
References