Developing a protocol to use remote sensing as a cost ...gers.uprm.edu/pdfs/pres_dnr07.pdf · sensing as a cost effective tool to monitor contamination of mangrove wetlands ... –

Developing a protocol to use remote sensing as a cost effective tool to monitor

contamination of mangrove wetlandsJohannes H. Schellekens, Fernando Gilbes-Santaella,

Augustine Rodriguez-Roman, and Belyneth Deliz

UPRM-Department of Geology

XXVI Symposium of the PR DNEROctober 25, 2007

Outline

– Remote sensing in mineral exploration or the search for chemical anomalies in the rocks

– The effect of chemical anomalies on vegetation– Reflectance of vegetation– Mangroves

• Importance of mangroves• Reflectance of mangroves

– Remote sensing to monitor mangroves for metal contamination

• Initial results

– Conclusions

Remote sensing in mineral exploration or the search for

chemical anomalies in the rocks

• The use of images from spaceborne platforms for mineral exploration has the advantage of large area or synoptic coverage which allows for portrayal of the Earth on regional basis.

• Use of different spectral bands allows to enhance special features (e.g. TM images)

TM 4/2 bright areas mark denser vegetation

TM 7/5 hook-shaped area coincides with general altered zone. Band 7: hydrous minerals absorb radiation - dark

3 km

Ratio color map: blue = 1/7, green = 4/2,And red = 3/1

basalts

andesite

Kaolinite&alunite

Kaolinite&alunite

• Kaolinite & alunite areas are a possible indication of a gold deposit

• Quantitative analysis of multispectral bands allows the distinction and enhancement of certain compositional properties

3 km


chemical anomalies in the rocks

• The direct observation of rocks and alteration zones in the tropics is hampered by the presence of thick soils and dense vegetation.

• However remote sensing techniques have been developed to make use of the vegetation.


chemical anomalies in the rock

The effects of metals in the substrate of vegetation gives two types of responses in the vegetation:

•Taxonomic response•Growth or non-growth of plant species

•Structural response•Including: Chlorophyll

synthesis

Remote sensing of metalsusing vegetation

Reflectance of vegetation

• Physiological changes: chlorophyll synthesis

What electromagnetic radiation is reflected by the leaves?

• Studies of reflectance patterns and metal content of substrate yielded varying results

• Red spruce shows an increase in reflection in visible light and reduction in the Infra red.

• This is not always the same for every tree species


• Laboratory test– Effects of Cu-

contamination on sorghum

– Obvious reflection increase in visible light

– Shift towards the blue wavelength of the infra red shoulder (blue-shift)


Control

100 ppmCuSO4

400 ppmCuSO4

http://en.wikipedia.org/wiki/Image:Sorghum.jpg

• Remote sensing for mineral deposits using changes in the vegetation works, but with a lot of variables

• The use of vegetation is based on the detection of chemical anomalies in the substrate that influence pigments (e.g. chlorophyll) production

• Can the technique also be used to detect metal contamination in mangrove wetlands??

• A work in progress


• Why mangroves?– The health of mangrove wetlands is of critical

importance to society in tropical marine regions; e.g. coastal protection, wildlife refuge, nursery for marine life

– Mangroves provide >10% of essential dissolved carbon in the oceans – influences global warming

– Mangrove wetlands have a more simple composition than the average tropical forest and may allow the use of remote sensing to detect anomalies

Importance of mangrove wetlands

Using remote sensing to detect heavy metals in substrate of mangroves

• The problem has three parts:– Contamination in substrate?

• Chemical analyses of “soils”– Do the contaminants influence

the leaves?• Chemical analyses of the top

leaves• Measuring reflectance spectra of

the top leaves– Can we see the difference using

satellite images?• Comparing reflectance spectra

of contaminated and non-contaminated mangroves

• Process the satellite images

?

?

Remote sensing to monitor mangroves for metal

contamination

The proposed research:• Using selected mangrove areas

– Chemical analyses of the “soils” (As, Cd, Cr, Pb, Hg, Ni, Co)– Analyse top leaves of canopy

• Chemical analyses of the top leaves• Measuring reflectance spectra of the top leaves

– Compare reflectance spectra of contaminated and non-contaminated mangroves

– Process the satellite images using the differences in reflectance– If successful:

• Write a protocol to process the images and discern possibly contaminated areas

• Enter data in GIS as guide to monitors

Sampling substrate and leaves from the top of the canopy


Scanning the standard and the leaves with the

GER 1500 spectroradiometer

Guayanilla:Close to industry

Punta Ballena:Pristine mangrove

Arecibo mangrove, next to urbanization, sewage treatment plant and electrical substation

Examples of mangroves areas:


• Pilot projects– Comparison of known heavy metal contaminated

mangroves with non-contaminated mangroves• Joyuda Lagoon next to Ni-Co laterite• Guayanilla reported Hg contamination• Arecibo in watershed with porphyry copper deposits• Guanica and Punta Ballena pristine environments

– Study of the transport of metals from the substrate to higher levels in the red mangrove

• Rhizophora mangle (red mangrove) Guayanilla and Joyuda – Use of AVIRIS

• Punta Ballena

Metals in the substrate

Cu vs Ni in sediments

020406080

100120140160180200

0 50 100 150 200

Cu

Ni

GuayanillaGuanicaAreciboJoyuda

Joyuda next to Ni-Co laterite

Guanica pristine control Contamination?

Co vs Cu in sediments

02468

101214161820

0 50 100 150 200

Cu

Co


Contamination?Joyuda next to Ni-Co laterite


Pb vs Cu in sediments

0

5

10

15

20

25

0 50 100 150 200

Cu

Pb


Contamination?


• Metal transport substrate to top of canopy– Enrichment ratio

• Divide metal content of top leave by metal content substrate• Example Cu in Rhizophora mangle in Guayanilla

Metal transport in treesTransport from substrate to top of canopy

Average substrate

Average bottom leaves

Average middle leaves

Average top leaves

Ratio Top/substrate

98.4 31.2 33.7 40.1 0.41

Observable transport from substrate to top of canopy

Metal transport in treesTransport from substrate to top of canopy

• Summary of top/substrate ratios for Rhizophora mangle– Cu

• Guayanilla 0.4 observable transport• Joyuda 1.2 metal concentration in tree• Punta Ballena 0.2 observable

– Ni • Guayanilla 0.01 very little uptake• Joyuda 0.02 very little uptake

– Co • Guayanilla 0.2 observable

• Enrichment ratio within tree– Divide metal content of top leave by metal content

bottom leave– Example Cu in Rhizophora mangle in Guayanilla

Metal transport in treesTransport in the tree from bottom leaves

to top of canopy

Average substrate

Average bottom leaves

Average middle leaves

Average top leaves

Ratio Top/bottom

98.4 31.2 33.7 40.1 1.3

When ratio > 1: Good transport in the tree and concentration of Cu in top of canopy

Metal transport in treesTransport from within tree

to top of canopy

• Summary of top/bottom ratios for Rhizophora mangle

– Cu Guayanilla 1.3: good transport• Joyuda 1.4: good transport

– Ni Guayanilla 0.3: little transport• Joyuda 0.4: little transport

– Co Guayanilla 2.5: very good transport

– Cd Guayanilla 0: no transport

– Pb Guayanilla 0.9: good transport

– Cr Guayanilla 1.3: good transport

Summary

– In order to use mangrove as a monitor plant using remote sensing, the tree has to take up the metal from the substrate and transport it to the top of the canopy

– The present data suggest:• Rhizophora mangle can be used to monitor for Cu,

Co, and possibly Pb and Cr, but not for Ni and Cd• Avicennia germinans (black mangrove) can be

used to monitor for Cu, Co and Cd

AVIRISAdvanced Visible and InfraRed Imaging

Spectrometer

• A NDVI image was created with the red band #29 (635.9 nm) and infrared band #51 (825.6 nm)

• NDVI can be determined per pixel

• Comparison of AVIRIS NDVI and NDVI measured with spectroradiometer showed that single trees produce too high NDVI with AVIRIS NDVI image of Punta Ballena at Guanica

State Forest produced in ENVI

NDVI Analyses

GER data Punta Ballena

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1 2 3 4 5 6 7 8 9

stations

NDV

I

Comparison GER 1500 and AVIRIS

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1 2 3 4 5 6 7

Stations

ND

VI

• NDVI measured using the GER 1500 spectroradiometer

• Comparison average station 1-6 and station 7-9 with AVIRIS results

• In stations 1-6 single trees allowed reflectance of beach sand

Conclusions

• The substrate of mangrove swamps does contain considerable amounts of heavy metals.

• Not all metals are taken up by mangroves– Cu, Co, Pb, Cr are taken up by Rhizophora mangle– Ni and Cd do not

• The reflectance spectra of mangroves when measured on the ground yield a wide range of reflectance spectra

• Averaging of these spectra seem to yield consistant results

• AVIRIS can be used, but ground truthing has to take into account the pixel size

Acknowledgments

– Dr. Arturo Massol– Ms. Elba Diaz– This work is funded by Sea Grant– Supported by the UPRM-Dept. of Geology

Documents

Developing a protocol to use remote sensing as a cost ...gers.uprm.edu/pdfs/pres_dnr07.pdf · sensing as a cost effective tool to monitor contamination of mangrove wetlands ... –