The
amelioration and remediation technology was developed on the
basis of research of phosphogypsum and utilization in the Haplic Chernozem
of South-European facies (Rostov Region). Phosphogypsum was utilized
via dispersed application into a soil layer of 20–45 cm with
intrasoil milling of this layer. The phosphogypsum utilization doses
were 0, 10, 20, and 40 t ha
–1
. The Pb analytical
content in soil solution was studied in the model experiment. The
soil solution Pb thermodynamic forms were calculated. The mathematical
chemical–thermodynamic model ION-2 was developed to calculate
the real soil solution (water extract) calcium-carbonate equilibrium
(CCE) ion forms, considering the ion pair association. The associated
ion pairs CaCO
3
0
, CaSO
4
0
, MgCO
3
0
, MgSO
4
0
, CaHCO
3
+
, MgHCO
3
+
, NaCO
3
–
, NaSO
4
–
, CaOH
+
, and MgOH
+
were accounted for in soil solution equilibrium
macroion form calculation. The procedure for the microelement ion
[including heavy metals (HMs)] equilibrium concentration in the soil
solution coefficient
k
as
calculation was
proposed to account for the real soil solution CCE, macroions, and
HM (including Pb) association. The Pb
2+
ion in soil solution
was mostly bound to associates PbOH
+
, Pb(OH)
2
0
, PbCO
3
0
, Pb(CO
3
)
2
2–
, and PbHCO
3
+
. The calculation of CCE and ion association in soil solution revealed
14.5–21.5 times HM passivation compared to HM water-soluble
values. The calculated HM activity in the soil solution in the example
of the Pb
2+
ion was less than 4% after phosphogypsum application
in the target amelioration layer of 20–45 cm. The studied phosphogypsum
doses were substantiated as environmentally safe. This was because
the real soil solution CCE provided HM ion form association and consequent
passivation. The dry steppe soil remediation after phosphogypsum application
was justified as highly probable. The intrasoil milling chemical soil-biological
engineering technology was developed for simultaneous soil amelioration
and remediation on the basis of the biogeosystem technique (BGT*)
transcendental methodology. The BGT*-based technology was tested in
the long-term field experiments and is capable of ensuring the priority
geophysical micro- and macroaggregate structure via intrasoil milling
and mixing of soil illuvial and transitional horizons. This helps
synthesize soil multilevel architecture, providing intrasoil-dispersed
environm...