Environmental Engineering Reference
In-Depth Information
Chapter 6
P
HOSPHORUS
R
ELEASE FROM THE
S
OILS
IN THE
Y
ELLOW
R
IVER
D
ELTA
:
D
YNAMIC
F
ACTORS
AND
I
MPLICATIONS FOR
E
CO
-R
ESTORATION
Gang Xu
1
, Junna Sun
1
, Yu Wu
1
and Hong-Bo Shao
1,2
1
Key Laboratory of Coastal Biology & Bioresources Utilization,Yantai Institute of
Coastal Zone Research (YIC),
Chinese Academy of Sciences (CAS), Yantai, China
2
Institute for Life Science,
Qingdao University of Science & Technology (QUST), Qingdao, China
A
BSTRACT
Root-released organic acids are reported to increase P availability in the soil based
on batch extraction or incubation results. Recently, some research raised the question
about the results because of the drawbacks in extraction experiment, for example, the
excessively high water-soil ratio and high-intensity mechanical oscillation are far
different from the actual soil environment. In this study a dynamic study of P release
from soil was conducted to offset these shortcomings and to get more exactly information
of the role of organic acids in P availability in soil. The results show that organic acids in
different concentrations significantly affected P release. In a concentration of 10mmol L
-
1
, no significant differences can be observed among citric acid, malic acid and acetic acid
in terms of their effect on the total release amount of soil P. By comparing the maximum
P release amount of different organic acids, the sequence was citric acid>malic
acid>oxalic acid>acetic acid. However, when the initial concentration of organic acids
was reduced to 1mmol L
-1
, both the total release amount and the maximum release
amount of soil P significantly declined, and the decline degree for different organic acids
were citric acid<malic acid<oxalic acid & acetic acid (amount of P leached is 0). When
the concentration of organic acids is 0.1mmol L
-1
, for the leaching volume applied for the
experiment, no P has been leached in the leaching solution of any of the four types of
organic acids. Given that oxalic acid tends to form calcium oxalate with soil calcium, the
total release amount of soil P in the case of oxalic acid is lower than that in the cases of
