Comparison of the Nitrate Levels in Water Bodies of Puerto Rico

Lysander Borrero and Eduardo Rivera

Abstract

Nitrate is a compound that is found in fertilizers, plants, urine, feces and many other

components. It can be found within the bodies of water; some have a higher concentration than

others. The bodies of water with higher concentration can cause serious diseases like blue baby

syndrome and even different types of cancer. By knowing this information, we collected samples

of water from a lake and a river for a period of five days during the morning and in the evening.

These samples were refrigerated and then analyzed to measure the concentration of nitrate. Our

results showed that the lake the concentrations were lower compared to the rivers, especially

after a precipitation event. In conclusion the nitrates levels rose after the precipitation just like

we stated in our hypothesis. Some of the factors that could have affected our results were the

storage of samples, the location, and agricultural or rural area.

Introduction

The main purpose of this investigation

was to measure the levels of nitrates in water

bodies. The nitrate molecule is composed of

one nitrogen atom and three hydrogen

atoms. Nitrates are soluble in water at

standard temperature and pressure. Also,

plants use nitrates as building blocks for the

formation of amino acids and DNA. But

since plants cannot produce nitrates, people

often use fertilizers, which are mostly

composed of nitrates, to help plants grow.

Using a great amount of fertilizers near a

water body can eventually end up inside of

it. If the fertilizers get in the water body, the

level of nitrates will rise up. High levels of

nitrates on water can affect humans in many

ways. Infants who drink water with high

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Comparison of the Nitrate Levels in Water Bodies of Puerto Rico

levels of nitrate can develop an acquired

form of the blue baby syndrome, also called

methemoglibinemia(Austin1999).

Methemoglobinemia is a blood disorder in

which the protein produced, methemoglobin,

has very little affinity with oxygen, unlike

hemoglobin. The problem with this disease

is that little oxygen reaches the body’s tissue

and gives the infant a blue colored skin.

Drinking water with high levels of nitrates

not only affects infants, but also adults. In

adults, nitrates can bind to N-nitroso

compounds found in the gastric juices of the

stomach. The most common cancers due to

high levels of nitrates are stomach cancer

and bladder cancer.

Through the process of our investigation, we

expect that the nitrate levels will rise after a

precipitation event in the lake and the river.

Our objective is to measure the levels of

nitrates in the water bodies after and

extreme precipitation event.

Methodology

The samples were taken within a

period of five days, from April 28th trough

May 2nd, one sample on the morning and one

on the evening. The samples were taken

from a lake and a river, both located in the

city of Caguas. The specific site of the lake

was in a housing community, called

Hacienda San Jose (figure 1A). The river

from where the sample was taken is called

“Rio Caguitas”. This river comes from

Aguas Buenas and passes through Caguas

and goes on to other cities. The specific site

where the sample was taken was in San

Antonio, very close to some houses (figure

2B). The sample was taken with a cup and

then it was stored in a refrigerator

until the nitrate levels were analyzed. The

dimethylphenol method using TNT 835

(containing sulfuric acid and phosphoric

acid) was performed. Later on, one milliliter

of the sample water was taken and placed

into the vial. Then we took 200 micro liters

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Comparison of the Nitrate Levels in Water Bodies of Puerto Rico

of Solution A (contains isopropanol) and

placed it in the vial also so that later we

mixed it three times causing an exothermic

reaction. Later the samples were left for

thirty minutes. After that, the vial was

extremely cleaned so the spectrophotometer

could read it accurately. Then vial was

inserted in the spectrophotometer and it

showed results of the levels of nitrates in the

sample.

Figure 1A

Figure 2B

Results

After the samples were analyzed in

the spectrophotometer, the ranges of nitrate

concentration were revealed. In the lake, the

nitrate concentrations were from 0.079 to

0.469 mg/L, as shown in table 2A. In the

river sample, the range of nitrate

concentrations was from 0.211 to 0.791

mg/L, as shown on table 3B.

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Comparison of the Nitrate Levels in Water Bodies of Puerto Rico

Lake Sample (Table 2A)

Date Time Nitrate Results

28/abril/2012 9:00 am 0.079 mg/L28/abril/2012 4:45 pm 0.111 mg/L29/abril/2012 7:15 am 0.122 mg/L29/abril/2012 4:30 pm 0.113 mg/L30/abril/2012 9:30 am 0.147 mg/L30/abril/2012 6:38pm 0.137 mg/L1/mayo/2012 6:47 am 0.137 mg/L1/mayo/2012 7:03 pm 0.469 mg/L2/mayo/2012 9:00 am 0.061 mg/L2/mayo/2012 6:48 pm 0.258 mg/L

River Sample (Table 3B)

Date Time Nitrate Results

28/abril/2012 11:35 am 0.303 mg/L28/abril/2012 5:32 pm 0.573 mg/L29/abril/2012 11:45 am 0.211 mg/L29/abril/2012 6:01 pm 0.540 mg/L30/abril/2012 6:28 am 0.628 mg/L30/abril/2012 6:27 pm 0.791 mg/L1/mayo/2012 6:37 am 0.706 mg/L1/mayo/2012 7:12 pm 0.470 mg/L2/mayo/2012 8:24 am 0.600 mg/L2/mayo/2012 8:21 pm 0.730 mg/L

The average of the concentration of nitrates

in the river was higher compared to the lake

samples, as shown in table 4. However, the

question is, did the levels of nitrate rose

when a precipitation event occurred? To

answer this question we did a table (table 4)

where we show you the nitrate levels before

and after a precipitation event. According to

the USGS (United Sates Geological Survey)

an extreme precipitation event occurred on

April 30th, 2012 I the afternoon (table 5).

The averages of both water bodies were

taken from April 28th in the morning and

April 30th, which is considered before

precipitation event. Through April 30th

evening and May 2nd evening, the Nitrate

levels rose in the lake sample after the

extreme precipitation event. Even though it

wasn’t an extreme difference, as shown in

table 6A, the nitrate levels rose in the river

sample and you can see the difference from

before and after the extreme precipitation

event, as shown in table 6B. Mainly you can

see that in both tables the nitrate levels did

rise after the precipitation occurred.

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Comparison of the Nitrate Levels in Water Bodies of Puerto Rico

Average of Nitrate Concentration (Table 4)

USGS Rain Gauge (Table 5)

Before and After Precipitation Event: Lake

Sample (Table 6A)

Before and After Precipitation Event: River

Sample (table 6B)

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Comparison of the Nitrate Levels in Water Bodies of Puerto Rico

Discussion

In conclusion the nitrate concentration

from the lake sample ranged from 0.079 to

0.469mg/L and the river sample from 0.211

to 0.769 mg/L. We can find a broader

amount of nitrates in fertilizers, which are

commonly used in agricultural areas and

since Rio Caguitas is near a rural area, the

fertilizers used near this location can end up

inside the river. However, the lake is not

near to any agricultural areas, so nitrates

from fertilizers do not end inside it. This

means that there is a higher probability that

the concentration of nitrates is higher in the

river than in the lake.

For future works, it would be good to take

samples of water when there is a dry out and

after an extreme precipitation event to

measure, analyze and compare the nitrate

levels. Also what would be good is to take

more samples so that we can have more data

and take samples from different sites in the

same body of water to see where the nitrate

levels are higher in that specific body of

water.

Acknowledgments

We will like to thank our mentor Dr.

Javier Arce and the Laboratory Technician

Ruby Otero. Also the RISE Program for

giving us the opportunity to participate in

this research.

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Comparison of the Nitrate Levels in Water Bodies of Puerto Rico

References

Hach Company. 2007. Nitrate. Revised

2010. Doc 316.53.01070. (p) 1-6

Kreitler C, Jones D. 1975. Natural Soil

Nitrate: The Cause of Nitrate Contamination

of Ground Water in Runnels County, Texas.

13 (1)

Self JR, Waskom RM. July 1995. Nitrates in

Drinking Water. Revised October 2008. Fact

Sheet No. 0.517

Austin A. 1999. Infantile

Methehemoglobinemia: Reexamining

the Role of Drinking Water Nitrates.

Environmental Health Perspectives

[Internet]; [Published 1999 June 1].

Volume(107):[approximately 4 p.].

Available on:

http://www.ncbi.nlm.nih.gov/pmc/articles/P

MC1566680/?page=1

United States Geological Survey:

http://waterdata.usgs.gov/pr/nwis/uv/?

dd_cd=01_00065&format=img_default&sit

e_no=50055225&set_arithscale_y=on&begi

n_date=20120425&end_date=20120502

http://waterdata.usgs.gov/pr/nwis/uv/?

dd_cd=03_00045&format=img_default&sit

e_no=50055225&set_arithscale_y=on&begi

n_date=20120425&end_date=20120502

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