『Abstract
Urbanization on the small subtropical island of Oahu, Hawaii
provides an opportunity to examine how anthropogenic activity
affects the composition of material transferred from land to ocean
by streams. This paper investigates the variability in concentrations
of trace elements (Pb, Zn, Cu, Ba, Co, As, Ni, V and Cr) in streams
of water sheds on Oahu, Hawaii. The focus is on water and suspended
particulate matter collected from the Ala Wai Canal watershed
in Honolulu and also the Kaneohe Stream watershed. As predicted,
suspended particulate matter controls most trace element transport.
Elements such as Pb, Zn, Cu, Ba and Co exhibit increased concentrations
within urbanized portions of the watersheds. Particulate concentrations
of these elements vary temporally during storms owing to input
of road runoff containing elevated concentrations of elements
associated with vehicular traffic and other anthropogenic activities.
Enrichments of As in samples from predominantly conservation areas
are interpreted as reflecting agricultural use of fertilizers
at the boundaries of urban and conservation lands. Particulate
Ni, V and Cr exhibit distributions during storm events that suggest
a mineralogical control. Principal component analysis of particulate
trace element concentrations establishes eigenvalues that account
for nearly 80％ of the total variance and separates trace elements
into 3 factors. Factor 1 includes Pb, Zn, Cu, Ba and Co, interpreted
to represent metals with an urban anthropogenic enrichment. Factor
2 includes Ni, V and Cr, elements whose concentrations do not
appear to derive from anthropogenic activity and is interpreted
to reflect mineralogical control. Another, albeit less significant,
anthropogenic factor includes As, Cd and U and is thought to represent
agricultural inputs. Samples collected during a storm derived
from an offshore low-pressure system suggest that downstream transport
of upper watershed material during tradewind-derived rains results
in a 2-3-fold dilution of the particulate concentrations of Pb,
Zn and Cu in the Ala Wai canal watershed.』
1. Introduction
2. Methods
2.1. Sample collection
2.2. Sample processing and analysis
3. Results and discussion
3.1. Dissolved trace elements in low flow samples
3.2. Dissolved trace elements during storm flow
3.3. Pb,Zn, Cu, Ba and Co in suspended particulate matter from
storm water samples
3.4. Arsenic in suspended particulate matter collected during
storms
3.5. Particulate Ni, V and Cr
3.6. Sampling of a “Kona” storm
3.7. Principal components analysis
3.8. Particulate and dissolved metal loads
4. Conclusions
Acknowledgements
Appendix A. Dissolved metal concentrations for individual
water samples from selected storms in the Ala Wai Canal watershed
Appendix B. Concentrations of SPM and trace elements in SPM
in storm water samples from the Ala Wai Canal watershed
Appendix C. Concentrations of trace elements in SPM in storm
water samples from the Kaneohe Stream watershed
References