Origin of Paddy Fields and Functions for Environmental Remediation in the Urbanized Areas of Yangtze River Delta - Environmental Contamination: Health Risks and Ecological Restoration - page 403

1000

y = 48.936e -0.1761x

100

R 2 = 0.5944

Fengqiu
Nanjiing

10

Suzhou

1

Yingtan

0.1 0

10 20 30

CH 4 emission (mg CH 4 /m 2 /h)

FIGURE 18.7
Relationship.between.NO 2 .and.CH 4 .emission.from.paddy..(Adapted.from.Cai,.Z.C..et.al.,. Plant
Soil ,.196(1),.7,.1997.)

each. lasting. for. 2-3. days,. after. the. productive. tillering. stage.. As. a. result,.
many.ine.pores.will.appear.in.the.surface.soil.through.which.oxygen.can.
directly.get.into.the.sublayer.of.soils..The.most.commonly.adopted.practice.
for.paddy.ield.systems.in.China.is.the.annual.cropping.rotation.of.summer.
rice.and.winter.wheat/oil.rape.seed,.which.leads.to.dried-up.paddy.ields.
for.the.entire.winter..These.practices.reduce.methane.emissions.during.the.
summer.signiicantly,.ranging.from.33%.to.68%..According.to.these.results,.
the.annual.methane.production.from.Chinese.paddy.soil.(1990-2000).was.
recalculated. with. an. average. of. 5.93.Tg. CH 4 . (Cai. et. al.. 2000).. Meanwhile,.
NO 2 . emissions. from. paddy. soil. were. much. less. than. from. upland. soils,.
with. an. estimated. value.of.about.88.Gg. N/year,. being.approximately. 22%.
of.the.total.NO 2 .emissions.from.China..Results.have.revealed.that.the.NO 2 .
emission. rate. may. not. be. necessarily. related. to. the. N. fertilizer. rate,. but.
to.the.water.regime.instead,.where.the.emission.is.seen.occurring. mostly.
during.the.seasons.involving.cultivation.of.crops.other.than.rice.(61%)..The.
NO 2 .emission.factor.(amount.of.NO 2 .emission.from.unit.Nitrogen.applied).
of.paddy.soil.was.only.one.third.of.what.was.found.in.upland.soils.(Xing.
et.al..2002,.Xing.and.Zhu.2002);.thus,.it.can.be.inferred.that.the.emission.of.
methane.and.NO 2 .in.paddy.soils.show.a.mutually.contentious.relationship.
(Figure.18.7).(Cai.et.al..1997).

Coping with Disasters of Flooding and Water Lodging

During. the. end. of. May. 2010,. there. was. a. disastrous. lood. that. occurred.
in. a. large. area. of. Southern. China. with. the. local. media. reporting. several.
hundred. fatalities,. extensive. damage. to. roads. and. buildings,. and. huge.
economic. losses.. It. happened. not. long. after. a. severe. drought. disaster. that.
occurred.during.the.spring.season.in.Yunnan.and.Guizhou.provinces..The.
central.meteorological.observatory.issued.warnings.of.looding,.from.June.
to. August. (the. monsoon. season),. in. the. middle. and. lower. reaches. of. the.
Yangtze.River.Valley..Every.year.during.the.monsoon.season,.the.central.and.