Developing a protocol to use remote sensing as a cost effective tool to monitor contamination of mangrove wetlands

Transcription

1 Developing a protocol to use remote sensing as a cost effective tool to monitor contamination of mangrove wetlands Johannes H. Schellekens, Fernando Gilbes-Santaella, Augustine Rodriguez-Roman, and Belyneth Deliz UPRM-Department of Geology XXVI Symposium of the PR DNER October 25, 2007

2 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

3 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

4 Remote sensing in mineral exploration or the search for chemical anomalies in the rocks andesite 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 basalts Kaolinite &alunite Ratio color map: blue = 1/7, green = 4/2, And red = 3/1 3 km Kaolinite&alunite

5 Remote sensing in mineral exploration or the search for chemical anomalies in the rock 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.

6 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 metals using vegetation

7 Reflectance of vegetation What electromagnetic radiation is reflected by the leaves? Physiological changes: chlorophyll synthesis

8 Reflectance of vegetation 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

9 Reflectance of vegetation Laboratory test Effects of Cucontamination on sorghum Obvious reflection increase in visible light Shift towards the blue wavelength of the infra red shoulder (blue-shift) 400 ppm CuSO 4 Control 100 ppm CuSO 4

10 Reflectance of vegetation 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

11 Importance of mangrove wetlands 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

12 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 noncontaminated mangroves Process the satellite images??

13 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 noncontaminated 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

14 Using remote sensing to detect heavy metals in substrate of mangroves Sampling substrate and leaves from the top of the canopy Scanning the standard and the leaves with the GER 1500 spectroradiometer

15 Examples of mangroves areas: Guayanilla: Close to industry Arecibo mangrove, next to urbanization, sewage treatment plant and electrical substation Punta Ballena: Pristine mangrove

16 Using remote sensing to detect heavy metals in substrate of mangroves 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

17 Metals in the substrate Ni Cu vs Ni in sediments Joyuda next to Ni-Co laterite Guanica pristine control Cu Contamination? Guayanilla Guanica Arecibo Joyuda

18 Metals in the substrate Co Co vs Cu in sediments Joyuda next to Ni-Co laterite Contamination? Guayanilla Guanica Arecibo Joyuda Cu

19 Metals in the substrate Pb vs Cu in sediments Pb Contamination? Guayanilla Guanica Arecibo Joyuda Cu

20 Metal transport in trees Transport from substrate to top of canopy 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 Average substrate Average bottom leaves Average middle leaves Average top leaves Ratio Top/substrate Observable transport from substrate to top of canopy

21 Metal transport in trees Transport from substrate to top of canopy Summary of top/substrate ratios for Rhizophora mangle Cu Ni Co Guayanilla 0.4 observable transport Joyuda 1.2 metal concentration in tree Punta Ballena 0.2 observable Guayanilla 0.01 very little uptake Joyuda 0.02 very little uptake Guayanilla 0.2 observable

22 Metal transport in trees Transport in the tree from bottom leaves to top of canopy Enrichment ratio within tree Divide metal content of top leave by metal content bottom leave Example Cu in Rhizophora mangle in Guayanilla Average substrate Average bottom leaves Average middle leaves Average top leaves Ratio Top/bottom When ratio > 1: Good transport in the tree and concentration of Cu in top of canopy

23 Metal transport in trees Transport 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

24 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

25 AVIRIS Advanced 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

26 NDVI Analyses NDVI NDVI GER data Punta Ballena stations Comparison GER 1500 and AVIRIS Stations 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

27 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

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