Relationships of Eutrophication to the Distribution of Mercury and to the Potential for Methylmercury Production in the Peat Soils of the Everglades

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• 作者：Panchabi Vaithiyanathan ; Curtis J. Richardson ; Rathi G. Kavanaugh ; Chris B. Craft ; and Tamar Barkay
• 刊名：Environmental Science & Technology
• 出版年：1996
• 出版时间：August 1996
• 年：1996
• 卷：30
• 期：8
• 页码：2591 - 2597
• 全文大小：343K
• 年卷期：v.30,no.8(August 1996)
• ISSN：1520-5851

文摘

Elevated mercury concentrations have been reportedin fish and wildlife from the Everglades in recentyears. The hypothesis that eutrophication caused bythe impact of phosphorous- (P) rich agriculturalrunoff stimulated methylmercury accumulation wasput forward because eutrophication had beenshown to be a cause for methylmercury accumulationin other ecosystems. We tested this hypothesis byobtaining total mercury (Hg_T) concentrationsandaccumulation rates and estimating the potential formicrobial methylation and methylmercury degradation in peat soils collected along a P gradient in waterconservation area 2A (WCA-2A). A negative correlation observed between Hg_T and Pconcentrationsin soils (r² = 0.64) was explained byincreased peataccretion rates in a nutrient-enriched area (7.1-7.5 mmyr^-1) as compared to an unenriched area(1.92-2.50 mm yr^-1), estimated using lead-210 andcesium-137 dating. Total Hg accumulation rates (post-1964)were comparable for the enriched and unenriched sites(29-30 and 29-37 µg m^-2yr^-1, respectively). Thus,calculations of Hg_T accumulation rates areconfounded by differences in peat accretion rates inthe Everglades. Potential rates for both methylation(2.3-48.6 ng g^-1day^-1) and demethylation(6.5-113.2ng g^-1 day^-1) werehigher in samples from WCA-2A than in samples collected in an area of the Evergladesthat had never been exposed to nutrients. However,trends suggesting the relationships of theseactivities to the P gradient in WCA-2A were notdetected, and methylation to demethylation ratios didnot correlate with soil P concentrations. The resultssuggest that (i) nutrient-enriched agricultural runofforiginating upstream of WCA-2A did not contributesignificantly to Hg_T built up in the northernEvergladesand (ii) eutrophication did not affect the potentialfor net methylmercury formation in peatsoils.