Environmental Engineering Reference
In-Depth Information
spaces.and.outer.barriers.to.the.whole.root.when.exposed.to.pollution,.and.
the. changes. to. the. same. pollutant. were. species. speciic.. Pi. et. al.. (2010a).
investigated. the. variability. of. ROL. and. root. anatomy. among. three. man-
grove. species. under. the. inluence. of. wastewater. discharge. for. 105. days..
ROL.at.the.root.tip.of.
B. gymnorrhiza
.increased.from.22.44.ng/cm
2
/min.in.
the. fresh. water. control. to. 31.09.ng/cm
2
/min. when. receiving. normal. syn-
thetic. wastewater. (NW;. with. concentrations. of. dissolved. organic. carbon.
[DOC],.
NH -N
4
3
−
,.comparable.
to.the.primarily.settled.municipal.sewage.in.Hong.Kong).and.to.44.22.ng/
cm
2
/min. when. treated. with. strong. wastewater. (10. NW;. DOC,.
NH -N
,.
NO -N
,.total.Kjeldahl.N.[TKN],.and.
PO -P
4
+
3
−
,.
4
+
3
−
.at.concentrations.of.60,.25,.0.5,.45,.and.5.mg/L,.
respectively),.which.however.did.not.change.the.“tight”.barrier.pattern.of.
B. gymnorrhiza
.(Figure.17.1A)..However,.for.
E. agallocha
,.discharge.of.waste-
water.caused.a.decrease.in.ROL.at.the.root.tip.but.an.increase.at.the.root.
base,. resulting. in. a. shifting. in. its. barrier. type. from. “tight”. to. “partial”.
(Figure.17.1B)..Such.a.trend.was.even.more.signiicant.for.
Acanthus ilicifolius
,.
leading.to.its.barrier.type.changing.from.“tight”.to.“weak”.(Figure.17.1C)..
The. changes. in. barrier. types. due. to. wastewater. discharge. were. related.
to. the. root. anatomy.. Among. the. three. species,.
Acanthus ilicifolius
. had. the.
highest. proportions. of. the. cross-sectional. area. of. aerenchyma. air. spaces,.
suggesting. that. internal. oxygen. transfer. to. the. root. tip. was. the. fastest..
However,.the.area.of.aerenchyma.air.spaces.in.the.root.tip.of.
Acanthus ilici-
folius
. treated. with. 10. NW. was. signiicantly. reduced,. whereas. the. area. of.
,.TKN,.and.
PO -P
4
NO -N
3
−
FV
FV
FV
NV
10 NV
B. gymnorrhiza
NV
10 NV
E. agallocha
NV
10 NV
A. ilicifolius
60
60
60
50
50
50
40
40
40
30
30
30
20
20
20
10
10
10
0
0
0
0 2
Distances from root tip (cm)
4
6
8
0 2
Distance from root tip (cm)
4
6
8
0 2
Distance from root tip (cm)
4
6
8
O
2
O
2
O
2
O
2
O
2
O
2
O
2
O
2
(A)
(B)
(C)
FIGURE 17.1
Changes.in.ROL.pattern.along.the.lateral.roots.of.mangrove.species.after.receiving.different.
strengths.of.wastewater.for.105.days:.(A).“Tight”.barrier,.(B).“partial”.barrier,.and.(C).“weak”.
barrier.. FW,. fresh. water;. NW,. normal. wastewater;. 10. NW,. 10. times. of. NW.. (Modiied. from.
Pi,.N..et.al.,.
Int. J. Phytoremediat
.,.12,.468,.2010a.)
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