Geology topics

Donald S. Ross

Publications and source records attributed to Donald S. Ross.

9 recordsLinked to original sources

USGS2025

Long‑term monitoring of mercury in Vermont’s forest soils: Trends over 20 years in near–surface horizons

Mercury is a soil pollutant of widespread concern, usually derived from airborne deposition. A long–term forest soil monitoring program began in 2002 at five sites (elevation 590–1140 m) in Vermont, USA. Total mercury (THg) and soil organic carbon (SOC) were assessed in the uppermost humified soil layer, either an Oa or A horizon. Sampling occurred every 5 years from ten subplots at each site. Tree species ranged from deciduous, mixed deciduous/conifer, to all conifer. After five samplings, the site means for THg ranged from 167 to 447 µg kg –1 and increased linearly with elevation ( R 2 = 0.78). One site had a significant temporal increase in THg of 3.9 µg kg –1 yr –1 ( p = 0.02). Overall SOC site means ranged from 133 to 434 g kg –1 . One site showed a significant temporal increase in SOC ( p = 0.01). The mean ratio of THg:SOC was similar at four of the sites (1318–1518 µg kg –1 ) but much lower (648 µg kg –1 ) at the site with the highest SOC and the temporal increase in THg. Within individual subplots, THg increased up to a maximum SOC concentration of ~ 320 g kg –1 and usually decreased above that threshold. Although both wet and dry mercury deposition in the northeast USA have declined, no evidence of declining soil THg concentration was found, likely due to strong retention by SOC. Continued monitoring is essential considering ongoing changes in deposition and future changes in the source–sink balance of mercury.

Vermont↗

USGS2021

Long-term monitoring of Vermont’s forest soils: Early trends and efforts to address innate variability

Long-term monitoring of forest soils is necessary to understand the effects of continued environmental change, including climate change, atmospheric deposition of metals, and, in many regions, recovery from acidic precipitation. A monitoring program was initiated in 2002 at five protected forest sites, primarily Spodosol soils, in Vermont, northeastern USA. Every 5 years, ten soil pits were sampled from random subplots in a 50 × 50-m plot at each site. Samples were taken by genetic horizon and, to reduce variability and improve comparability, from four specific layers: the combined Oi/Oe layer, the combined Oa/A layer, the top 10 cm of the B horizon, and 60–70 cm below the soil surface (usually the C horizon). The samples were archived and a subset analyzed for carbon, nitrogen, and exchangeable cations. After four sampling campaigns, the average coefficients of variation (CVs) at each site had a broad range, 10.7% for carbon in the Oa/A horizon to 84.3% for exchangeable Ca 2+ in the B horizon. An investigation of variability within the upper 10 cm of the B horizon across a 90-cm soil pit face showed similar CVs to the entire site, emphasizing the need for consistent and careful sampling. After 15 years, temporal trends were significant in the Oa/A and B horizons at two of the five sites, with one site showing an increase in carbon concentration in both layers along with increases in both exchangeable Ca 2+ and Al 3+ in the B horizon, perhaps linked to recovery from acidification. The monitoring program plans to continue at 5-year intervals for the next century.

Vermont↗

USGS2018

In the path of the hurricane: Impact of Hurricane Irene and Tropical Storm Lee on watershed hydrology and biogeochemistry from North Carolina to Maine, USA

Although many climate predictions suggest that the frequency and intensity of large storm events might increase in the coming decades, few studies document the full impact of such events along their path. Here, we synthesize information on the impact of Hurricane Irene (formed August 21 2011) and Tropical Storm Lee (formed August 30, 2011) on erosion and sediment transport, lake metabolism, riparian hydrology and biogeochemistry, and stream water quality, from North Carolina to Maine. In almost all cases, these storms generated unprecedented changes in water quality (concentrations, loads), from tenfold increases in DOC and 100-fold increases in POC in Maryland, to 100-fold increases in TSS concentrations in Pennsylvania. Overbank flooding and up to 200-year streamflow events were recorded in New York and Vermont. In many cases, particulate loads (e.g. POC, PP, TSS) occurring during Irene and Lee represented more than 30% of the annual load. The dominance of particulate exports over solutes during Irene and Lee is consistent with the mobilization of normally immobile sediment pools, and massive erosion as reported at many locations across the Northeastern US. Several studies reported long lasting (> 1 year) effects of Irene and Lee on cyanobacterial blooms, erosion, or stream suspended sediment concentrations. However, this review also highlighted the lack of a consistent strategy in terms of methods, and measured water quality parameters. This strongly hinders our ability to fully assess the large-scale impact of such events on our environment, and ultimately their impact on our economy and society.

Biogeochemistry↗

USGS2017

Deposition of mercury in forests across a montane elevation gradient: Elevational and seasonal patterns in methylmercury inputs and production

Global mercury contamination largely results from direct primary atmospheric and secondary legacy emissions, which can be deposited to ecosystems, converted to methylmercury, and bioaccumulated along food chains. We examined organic horizon soil samples collected across an elevational gradient on Whiteface Mountain in the Adirondack region of New York State, USA to determine spatial patterns in methylmercury concentrations across a forested montane landscape. We found that soil methylmercury concentrations were highest in the midelevation coniferous zone (0.39 ± 0.07 ng/g) compared to the higher elevation alpine zone (0.28 ± 0.04 ng/g) and particularly the lower elevation deciduous zone (0.17 ± 0.02 ng/g), while the percent of total mercury as methylmercury in soils decreased with elevation. We also found a seasonal pattern in soil methylmercury concentrations, with peak methylmercury values occurring in July. Given elevational patterns in temperature and bioavailable total mercury (derived from mineralization of soil organic matter), soil methylmercury concentrations appear to be driven by soil processing of ionic Hg, as opposed to atmospheric deposition of methylmercury. These methylmercury results are consistent with spatial patterns of mercury concentrations in songbird species observed from other studies, suggesting that future declines in mercury emissions could be important for reducing exposure of mercury to montane avian species.

New York↗

USGS2016

Methods of soil resampling to monitor changes in the chemical concentrations of forest soils

Recent soils research has shown that important chemical soil characteristics can change in less than a decade, often the result of broad environmental changes. Repeated sampling to monitor these changes in forest soils is a relatively new practice that is not well documented in the literature and has only recently been broadly embraced by the scientific community. The objective of this protocol is therefore to synthesize the latest information on methods of soil resampling in a format that can be used to design and implement a soil monitoring program. Successful monitoring of forest soils requires that a study unit be defined within an area of forested land that can be characterized with replicate sampling locations. A resampling interval of 5 years is recommended, but if monitoring is done to evaluate a specific environmental driver, the rate of change expected in that driver should be taken into consideration. Here, we show that the sampling of the profile can be done by horizon where boundaries can be clearly identified and horizons are sufficiently thick to remove soil without contamination from horizons above or below. Otherwise, sampling can be done by depth interval. Archiving of sample for future reanalysis is a key step in avoiding analytical bias and providing the opportunity for additional analyses as new questions arise.

Journal of Visualized Experiments↗

USGS2016

Enriched groundwater seeps in two Vermont headwater catchments are hotspots of nitrate turnover

Groundwater seeps in upland catchments are often enriched relative to stream waters, higher in pH, Ca 2+ and sometimes NO 3 ¯. These seeps could be a NO 3 ¯ sink because of increased denitrification potential but may also be ‘hotspots’ for nitrification because of the relative enrichment. We compared seep soils with nearby well-drained soils in two upland forested watersheds in Vermont that are sites of ongoing biogeochemical studies. Gross N transformation rates were measured over three years along with denitrification rates in the third year. Gross ammonification rates were not different between the seep and upland soils but gross nitrification rates were about 3 × higher in the seep soils. Net nitrification rates trended higher in the upland soils and NO 3 ¯ consumption (gross—net) was 8 times higher in the seep soils. The average denitrification rate for seep soils was about equal to the difference in NO 3 ¯ consumption between seep and upland soils, suggesting denitrification can make up the difference. Temporal variation in seep water NO 3 ¯ concentration was correlated with watershed outlet NO 3 ¯ concentration. However, it is not clear that in-seep processes greatly altered seep water NO 3 ¯ contribution to the streams. Seep soils appear to be hotspots of both nitrification and denitrification.

Vermont↗

USGS2015

Inter-laboratory variation in the chemical analysis of acidic forest soil reference samples from eastern North America

Long-term forest soil monitoring and research often requires a comparison of laboratory data generated at different times and in different laboratories. Quantifying the uncertainty associated with these analyses is necessary to assess temporal changes in soil properties. Forest soil chemical properties, and methods to measure these properties, often differ from agronomic and horticultural soils. Soil proficiency programs do not generally include forest soil samples that are highly acidic, high in extractable Al, low in extractable Ca and often high in carbon. To determine the uncertainty associated with specific analytical methods for forest soils, we collected and distributed samples from two soil horizons (Oa and Bs) to 15 laboratories in the eastern United States and Canada. Soil properties measured included total organic carbon and nitrogen, pH and exchangeable cations. Overall, results were consistent despite some differences in methodology. We calculated the median absolute deviation (MAD) for each measurement and considered the acceptable range to be the median 6 2.5 3 MAD. Variability among laboratories was usually as low as the typical variability within a laboratory. A few areas of concern include a lack of consistency in the measurement and expression of results on a dry weight basis, relatively high variability in the C/N ratio in the Bs horizon, challenges associated with determining exchangeable cations at concentrations near the lower reporting range of some laboratories and the operationally defined nature of aluminum extractability. Recommendations include a continuation of reference forest soil exchange programs to quantify the uncertainty associated with these analyses in conjunction with ongoing efforts to review and standardize laboratory methods.

Ecosphere↗

USGS2013

Measuring environmental change in forest ecosystems by repeated soil sampling: a North American perspective

Environmental change is monitored in North America through repeated measurements of weather, stream and river flow, air and water quality, and most recently, soil properties. Some skepticism remains, however, about whether repeated soil sampling can effectively distinguish between temporal and spatial variability, and efforts to document soil change in forest ecosystems through repeated measurements are largely nascent and uncoordinated. In eastern North America, repeated soil sampling has begun to provide valuable information on environmental problems such as air pollution. This review synthesizes the current state of the science to further the development and use of soil resampling as an integral method for recording and understanding environmental change in forested settings. The origins of soil resampling reach back to the 19th century in England and Russia. The concepts and methodologies involved in forest soil resampling are reviewed and evaluated through a discussion of how temporal and spatial variability can be addressed with a variety of sampling approaches. Key resampling studies demonstrate the type of results that can be obtained through differing approaches. Ongoing, large-scale issues such as recovery from acidification, long-term N deposition, C sequestration, effects of climate change, impacts from invasive species, and the increasing intensification of soil management all warrant the use of soil resampling as an essential tool for environmental monitoring and assessment. Furthermore, with better awareness of the value of soil resampling, studies can be designed with a long-term perspective so that information can be efficiently obtained well into the future to address problems that have not yet surfaced.

Journal of Environmental Quality↗

USGS2010

Flow path studies in forested watersheds of headwater tributaries of Brush Brook, Vermont

An investigation was undertaken into how headwater tributaries of Brush Brook, Vermont, could have average p H differences of almost two units (4.75 and 6.7). Sampling along four tributaries revealed that most of one tributary, below an area of seeps, had consistently higher p H, Ca 2+ , Mg 2+ , and K + , and lower Al than other sites. Bedrock mapping showed numerous fractures in vicinity of the seeps. A portion of this tributary's watershed and a portion of an acid tributary's watershed were intensively mapped for soil depth. Sampling showed the widespread existence of dense basal till in the watershed of the acid tributary but none in that of the near-neutral stream. Lateral flow, found above the dense till, was chemically similar to that of the acid tributary and to solutions sampled from soil B horizons. There were no differences in the average p H of nonseep soils sampled from either watershed. Flow paths are hypothesized to be through the B horizons in the acid tributaries and from below the soil profile in the near-neutral tributary. The acid catchment should be more sensitive to environmental change.

Vermont↗