2008-09 Hong Kong Budding Scientists Award
(Secondary Section)
2nd Runner-up
The Y.W.C.A. Hioe Tjo Yoeng College
Topic: The risk of desertification
Prepared by:
Tsang Sau Ping 曾秀萍
Ng Chi Hei 伍志熹
Ng Hing Yu 吳慶瑜
Yip Ming Him 葉銘謙
Tsoi Ping Yuen 蔡秉源
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1. What is desertification?
Desertification is the degradation of land in arid and dry sub-humid areas, resulting primarily from
human activities and influenced by climatic variations. A major impact of desertification is biodiversity
loss and loss of productive capacity as the drylands are rich in genetic diversity of plants that can tolerate
extreme drought and disease. Desertification currently affects one-third of the world's population.
2. Desertification in China
Desertification has great influence on Chinese people. Annually, about 13,000,000 km2 of cropping lands
are threatened by wind and dust causing a decrease in cereal yield. This decrease in resources slows
down the economic development of the affected areas.
Information from the State Forestry Administration of China in 2006 indicates that 1,739,700 km2 of
land is under desertification in China. It occupies more than 30% of China and affects about 30
provinces, autonomous regions and municipalities. Recently, two deserts in north-central China
expanded and merged to form a larger desert overlapping Inner Mongolia and Gansu provinces.
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3. Causes of desertification in China
(i) Large temperature difference of the land
In Mainland China, like Mongolia, the morning temperatures are above 30 oC, but at night
temperatures fall to approximately 10 oC. Thus plants can hardly grow healthily and may die easily.
(ii) Inadequate rainfall
In Mongolia, the average rainfall of the whole year is about 400 mm. As a result, plants die due to a
lack of water.
(iii)Over grazing
Sheep tend to eat grass down to root level and hence the absorption of water is not possible.
Moreover, sheep rearing does affect the quality of soil adversely which further reduces land use.
(iv) Deforestation
Chinese loggers annually exceeded logging quotas by an average of 75 million m3. The loss of plant
cover means that the rain falls directly onto the ground washing away the fertile topsoil, nutrients and
minerals. Plant roots hold soil together to prevent its erosion. The decrease in the number of plants
thus increases the chance of wind or water erosion.
(v) Over-cultivation
With continuous planting, there is little chance for land to recover the loss of nutrients. This affects
the quality and amount of agricultural output.
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4. Action taken by the Chinese government
(i) Artificial rainfall
Owing to the scarcity of rain in Mongolia, the government is using chemicals such as silver iodide or
dry ice to facilitate condensation in moisture-laden clouds to create more rain.
(ii) Green Wall of China
A "Green Wall of China", is a series of human-planted forest in China, designed to resist the
expansion of the Gobi Desert. It will eventually stretch more than 4,480 kilometers in length, nearly
as long as the Great Wall of China.
(iii)Ban on grazing
China has decided to restrict grazing to special zones, in compliance with the 11th Five-Year
Programme (2006-2010) and to promote circle-grazing (except in certain tourist areas).
(iv) Ban on lumbering
Lumbering destroys the eco-system and increases desertification. Therefore the government has
banned lumbering. Farmers can use substitute materials like corn cobs for warmth and concrete for
building.
(v) Ban on picking Fat Choy
Fat Choy roots hold the soil together but farmers always pick Fat Choy for sale. If Fat Choy is picked,
soil becomes loose and will be washed away easily. As a result, the government has set up a law to
stop the picking of Fat Choy.
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5. Possible solutions to desertification in China
5.1 Adding Hydro gels in the sand to absorb water.
Hydrogel (slush powder) are super-absorbent materials that absorb extremely large amounts of a
liquid relative to its own mass. They are commonly used in making diaper and menstrual pads. To
produce hydrogels, two monomers, acrylic acid and acrylamide, are combined to form
polyacrylamide, a sponge-like substance, which is then mixed in soil. They could be used to conserve
water use in agriculture and forestry since they absorb aqueous solutions through hydrogen bonding
with water molecules. Our group tried growing some green beans and vegetables in sand using
hydrogels.
A.
To investigate the effects of hydrogels on growing plant in sand
I.
Apparatus and Chemicals
II.
Some sand
Some green beans
Vegetables seeds
Some hydrogels
Some water
Some pots
Procedures
1. Get hydrogel from the diapers and measure different amounts of hydrogels.
Hydrogel can be found in diapers.
Hydrogels absorbs water and
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2. Mix different amount of hydrogels in different pots which contain 160 g of sand.
3. Add water to pots until sand is saturated with water.
4. Put 3 green beans or vegetable seeds in each pot.
5. Place these pots in the sun without adding any water throughout the experiment.
6. Record the results after 21 days.
III. Results
After 21 days, the growth of the seedlings is shown below.
Amount of
Type of
Length of
hydrogel
plants
stem
0.0 g
Green beans
0 cm
0.1 g
Green beans
11 cm
0.2 g
Green beans
10 cm
0.3 g
Green beans
8 cm
0.4 g
Green beans
9 cm
0.5 g
Green beans
13 cm
0.0 g
Shang-hai
Pai-Tsai
0 cm
0.3 g
Shang-hai
Pai-Tsai
3 cm
0.0 g
Nai Lon PaiTsai
0 cm
0.3 g
Nai Lon PaiTsai
4 cm
Results
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B.
To investigate the maximum amount of water that hydrogels can absorb
I.
Apparatus and Chemicals
II.
Some Hydrogel
Some water
A filter funnel
Some pieces of filter paper
A Measuring cylinder
A beaker
Procedures
1. Add water into 0.1g hydrogel until the latter is saturated in a beaker.
2. Pour the solution into a funnel with filter paper to filter the hydorgel.
3. Measure the volume of the filtrate.
III. Results
Trial 1
Trial 2
Trial 3
Volume of water (cm3)
100
100
100
Water remaining (cm3 )
59
60
62
Water absorbed (cm3 )
41
40
38
Average
39.6 cm3
1.0 g of hydrogel from diapers can absorb about 400 cm3 of water.
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C.
I.
To investigate the effect of active ingredients of biodegradable diaper in growing plants
Apparatus and Chemicals:
Some hydrogel
Some corn starch powder
Some water
Some sand
2 pots
Green beans
II. Procedures:
1. Mix 0.3 g hydrogel with 0.0 g and 0.5 g corn starch in different pots which each contain
160 g of sand.
2. Add water to pots until the sand is saturated with water.
3. Put 3 green beans in each pot.
4. Place these pots in the sun without adding any water throughout the experiment.
5. Record the results after 21 days.
III. Results
Amount of
hydrogels
0.3 g
Amount of
corn starch
0.0 g
Type of
plants
Green beans
Length
of stem
8 cm
0.3 g
0.5 g
Green beans
12 cm
Results
One of the major component of biodegrable diapers is corn starch. From our experiment, the
presence of corn starch may provide nutrients for plant growth.
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5.2 Plant vegetations that can tolerate extreme drought
Larrea tridentata, Mesquite and Common Ragweed are plants that can tolerate desert climates.
They have small, narrow leaves to reduce water loss. Like legumes, they hold nitrogen in soil.
They grow quickly and absorb water efficiently.
6. Discussion
A small amount of hydrogel can retain a large amount of water in sand. With the building of
underneath water pipes that carry water to desert, we may provide good conditions for plants.
Growing plants thus helps prevent soil erosion. The transpiration of plants produces a cooling
effect to the surrounding, and help change the hot climate in the area affected by desertification.
Developers on Jumeira Islands use the technology in disposable diapers made of hydrogel to
plant the sandy soil of dry desert climate.
The development of biodegradable diaper is now in progress. The government may encourage
more families to use biodegradable diapers and then collect them from families, hospitals or
kindergartens. These can be sent to areas of desertification. Since biodegradable diapers can
break down by themselves, it reduces the problem of landfill. Besides, waste presence in
biodegradable diapers is nutritious to plants.
In our experiment, some vegetables can grow in sand with hydrogel. The government may
encourage farmers to plant different vegetables so as to balance the cost of using hydrogels with
the profit made. It can also provide food for people who live there.
The price of hydrogel is high. Terra Cottem, which is a soil conditioner containing hydrogel, is
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sold for erosion control in Iran for about US$2 per pound for about 50 square feet of land.
According to our experimental results, if we use 0.5g hydrogel for 160 g of sand, we should use
0.5 
160
 3.125 g hydrogel in 1 kg of sand. The cost is about US$4.4 per kg of sand. It is
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reasonable for applications like landscaping and tree nurseries, but still very expensive for
general agriculture. We suggest the government set up a national factory to produce hydrogel
massively to reduce cost.
Hydrogels (Polyacrylamide) is nontoxic, but acrylamide, one of its components is not. Trace
amounts of these toxins can kill plants. Careful manufacture is needed to ensure that the
acrylamide is completely reacted. Therefore, it is recommended that the government set up an
organization to monitor manufacturers.
In our experiments, we could not simulate the actual climate in desert like the temperature
difference between day and night, humidity and the amount of sunlight in Hong Kong. More
investigation has to be done on the use of hydrogel.
7. Conclusion
With the help of hydrogels, we can plant vegetation that protects soil from erosion in deserts and
fight desertification in China.
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8. Reference
1. 淺利義遠。《科學小神通》。台灣：尖端，1997。
2. NJ 4-H National Science Experiment Day, New Jersey Agricultural Experiment Station.
http://www.njaes.rutgers.edu/spotlight/4-hscience.asp
3. Superabsorbent polymer, Wikipedia. http://en.wikipedia.org/wiki/Superabsorbent_polymer
4. Larrea tridentata, Wikipedia.
http://en.wikipedia.org/wiki/Creosote_bush
5. Mesquite, Wikipedia.
http://en.wikipedia.org/wiki/Mesquite
6. Ambrosia artemisiifolia, Wikipedia:
http://en.wikipedia.org/wiki/Common_Ragweed
7. Common Ragweed, Weedy Wildflowers of Illinois.
http://www.illinoiswildflowers.info/weeds/plants/cm_ragweed.htm
8. Welwitschia mirabilis.
http://www.plantzafrica.com/plantwxyz/welwitschia.htm
9. Welwitschia, Wikipedia.
http://en.wikipedia.org/wiki/Welwitschia#Scientific_classification_according_to_different_so
urces
10. Combating Desertification in China
http://www.worldchanging.com/archives/008693.html
11. China says deforestation still a major environmental problem
http://www.terradaily.com/2005/050118102656.tgm9j244.html
12. Rain making for the Olympics 2008 in China
http://desertification.wordpress.com/2007/07/10/rain-making-for-the-olympics-2008-inchina-technorati-nara/
13. Now, Diaper Technology Takes On a Desert.
http://query.nytimes.com/gst/fullpage.html?res=9C07E1DD103AF933A15754C0A9629C8B
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14. China Losing War With Advancing Deserts
http://www.earth-policy.org/Updates/Update26.htm
15. The Consequences of Desertification
http://home.ica.net/~drw/env/d-page~2.htm
16. Traditional Knowledge and Practical Techniques for Combating Desertification in China
http://www.desertification.gov.cn/xinxi/book2/ctk-1.html
17. Agro-Conservation Project
http://www.greenglobal-resources.com/projects/antidesert.html
18. China Imposing Grazing Ban in Order to Save Pasture
http://www.redorbit.com/news/science/444882/china_imposing_grazing_ban_in_order_to_sa
ve_pasture/
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Comments
The report contained a comprehensive analysis of using hydrogels in
agriculture.
A panel of judges appreciated much on students'
attempt to delineate the practical issues associated with the use of
hydrogels, such as cost-analysis, toxicity and process of
commercialization.
It is worthwhile to consider using a ‘large’ plant instead of solely green
beams in the research. Perhaps, it may bring more ‘uncertainties’
from the experiments, but more uncovered facts or research-worthy
findings may shed light on further inquiries.
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