The Study Of Akali Metal Contamination In Road Side Soil

The Study of Akali Metal Contamination in Road Side Soil

Abstract

Six soil samples were taken from a roadside that was expected to exhibit

characteristic of road salt contamination. This contamination is characterized

by the presence of magnesium, calcium and sodium. The relationship between akali

metal concentration and distance from the pavement was examined and determined

to be nonexistent. Additionally, atomic absorbtion and atomic emission

spectroscopy were compared and and atomic absorbtion was found to be 1.89 times

as sensitive as atomic emission.

Introduction

A common technique in snow and ice removal on roadways is the application of

magnesium, calcium, and sodium chloride salts to the surface of the road. When

the ice melts it dissolves these salts and causes them to migrate into soil that

is adjacent to the pavement. Over time, the accumulation akali metal salts can

change the chemical profile of the soil which can lead to detrimental biological

effects. Flame atomic spectroscopy provides a technique that can quantify metal

concentrations in the extracts of the soil samples and consequently examine the

relationship between distance from the point of road salt application and akali

metal concentrations.

Experimental

Soil preparation: Six surface soil samples were collected at the intersection of

Cold Spring Lane and the exit ramp of Interstate 83, in northwest Baltimore city.

These samples were collected at distances from the roadway of 0m, 2m, 4m, 6m,

10m, and 20m. These samples were dried in a convection oven at 110°C for over 24

hours then crushed. Aliquots of approximately one gram were weighed and then

extracted with 10.0 mL of 1M ammonium acetate. The extract was filtered with an

inline filter disc with a pore size of 5mm and then diluted to 100.0 mL.

Instrumental: The extracts were analyzed for Ca, Na, and Mg using a Varian model

AA-3 flame atomization spectrophotometer with a diffraction grating

monochromator. Data was collected with a Houston Instrument chart recorder. An

acetylene/air reducing flame was used for all determinations (10 psi acetylene/7

psi air). Two replicates of each sample were made and averaged for both AA and

AE. The analysis was seperated into two methods; atomic absorbtion (AA) and

atomic emission (AE). The emission intensities and absorbances were determined

from the measured peak height obtained from the chart recordings. Atomic

Emission: Na and Ca concentrations in the soil were determined using AE. The

spectrophotometer was calibrated using the standard series method for both

elements. Regression analysis was performed on the calibration data to provide a

functional relationship between emision intensity and concentration.

Results and Conclusions:

Sodium: The atomic line used in the analysis for sodium was at 589.0 nm. The

relationship between emision intensity and concentration was found to be