ABSTRACT:
New Hampshire Apple Orchards as a Source of Arsenic Contamination
Concern about high trace metal contamination in New Hampshire
water supplies has focused attention on the fate of both
natural and anthropogenic trace metals in the environment.
We investigate apple orchards as a possible source of As
in surface water and groundwater of New Hampshire. Lead
arsenate sprays were widely used as fungicides and insecticides
in apple orchards for more than a century and they represent
the largest single anthropogenic input of arsenic into the
environment. The applied As may 1) have remained in the
surface soil, 2) have moved downward in the soil column
and become stored in deeper soil horizons and/or regional
groundwater system, or 3) have been transported as a result
of overland surface runoff and/or erosion to surface reservoirs.
We examine these pathways using two types of samples collected
from a Southern New Hampshire apple orchard: soil profiles
from apple orchards having different pesticide application
(sprayed or not sprayed with lead arsenate) and land use
(tilled or untilled) history, and stream sediment cores
that may have accumulated sediments transported from nearby
apple orchards. Preliminary analyses provide the following
observations. First, apple orchards which used lead arsenate
pesticides contain significantly elevated As and Pb concentrations
(up to 80æg/g and 600æg/g, and about 1 and 2
orders of magnitude above the background levels, respectively)
in the surface soils. Second, As and Pb are generally limited
to the upper 10-15 cm of soil, showing little evidence of
downward transport. This suggests that As is largely chemically
immobile in the soil environment and that the main mechanism
for As removal from its source may be physical erosion.
We hypothesize that, if left undisturbed, lead arsenate
remains immobile in the soil column. However, any disturbances
that increase physical erosion of the soil may mobilize
the arsenic and lead and concentrate these metals in nearby
stream and lake sediments. We test this hypothesis by comparing
apple orchard sites with different land management history
(tilled versus untilled) and by examining stream sediment
samples potentially originating from As and Pb contaminated
soils.
Wong CK, Renshaw CE, Feng X, Sturup S. New Hampshire Apple
Orchards as a Source of Arsenic Contamination. American
Geophysical Union. May; A5, 2002.
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