You are here:
ORGANIC CARBON FRACTIONS IN O AND B HORIZON SOLUTIONS FROM A NEW ENGLAND SPODOSOL: EFFECTS OF ACID TREATMENT
Citation:
David, M., G. Vance, J. Rissing, AND F. Stevenson. ORGANIC CARBON FRACTIONS IN O AND B HORIZON SOLUTIONS FROM A NEW ENGLAND SPODOSOL: EFFECTS OF ACID TREATMENT. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-89/196.
Description:
We examined the effects of H2SO4 and HNO3 on dissolved organic carbon (DOC), pH, and DOC fractions in extracts from Spodosol O and B horizon samples of a forest soil from eastern Maine. reliminary work with HNO3 at pH=3(1 to 24h shaking, ionic strength adjustment with NaNO3 (I=0.1 to 0.001) indicated rapid equilibration (1 h) of DOC in treatment solutions with B horizon samples, but that DOC levels in extracts from the O horizon increased continuously over time. n the remaining work, H2SO4 and HNO3 and their Na salts were added at a constant I of 0.01 and solutions were recovered after shaking for 16 h. he DOC in O horizon extracts decreased with increasing acidity, reaching a minimum at p[H] = 2(from ca. 5 mmol C L1 with no acid addition to ca. 2 mmol C L1. For the B horizon extracts, DOC increased with increasing acidity. ercent neutralization of added H+ ranged from 18 to 99% in the O horizon for acid treatments ranging from p[H]=1 to 4 respectively; B horizon values were 16 to 85% for H2SO4 and 2 to 70% for HNO3. he DOC in O horizon solutions was dominated by hydrophobic and hydrophilic acids (ca. 45 and 20% of DOC, respectively), which were altered by acidic inputs; primarily by a decrease in hydrophobic acids (45 to ca. 15-18% of DOC) and an increase in hydrophobic acids (ca. 20 to 35-40% of DOC) as acidity increased. For the B horizon, similar trends were observed, although hydrophobic/hydrophilic acid ratios were lower, indicating that hydrophobic acids have a lower solubility with increasing acidity. rom an environmental perspective, increasing acidic inputs through wet and dry deposition on forest Spodosols of New England may have significant consequences inthe solubilization and transport of metals and acidity because of differences in DOC fractions.