Environmental magnetic studies on surface sediments: a proxy for metal and hydrocarbon contamination|
Venkatachalapathy, R.; Rajeswari, V.; Basavaiah, N. & Balasubramanian, T.
Visakhapatnam is one of the major port cities,
and it is developed into a hub of many large- and mediumscale
industries. Due to growing industrialization and
urbanization, coast is vulnerable to both organic and inorganic
micro-pollutants. Twenty-five surface sediments were
collected along the Visakhapatnam coast for the measurement
of texture size, petroleum hydrocarbons, trace metals
and environmental magnetic parameters. The percentage of
coarser particles was more in the northern region, whereas
the percentage of fine particles was increased toward south.
Elevated levels of petroleum hydrocarbons and trace metals
were attributed due to marine and land-based sources, in
particular, those were due to shipping activities, treated and
partially treated sewage and industrial wastes. The concentrations
of trace metals, petroleum hydrocarbons and
magnetic minerals were decreased from nearshore to seaward.
Our results revealed that the magnetic mineralogy is
dominated by magnetite with a small proportion of hematite,
and the grain size of magnetic minerals was in the range
of pseudo-single domain to multidomain nature with
detrital origin. From the principal component analysis, the
magnetic concentration and mineralogy-dependent parameters
co-vary with the heavy metal and PHC concentrations,
suggesting that the inputs of magnetic minerals, petroleum
hydrocarbons and heavy metals in the Visakhapatnam shelf
sediments were derived from the same anthropogenic
sources. Thus, the large magnetic dataset can be used to
reduce the number of chemical analysis; hence, environmental
magnetic parameters were used as a proxy for both
organic and inorganic micro-pollutants.
Environmental magnetism; Sediment texture; Petroleum hydrocarbon; Trace metals; Multivariate statistics