Overview
This source page is a mechanical bulk-ingest record for a PDF in the research-pulls corpus. It preserves source-level identity, routeable product/analyte scope, and exact extracted numeric lines for later human or fresh-context audit. It does not derive HMTc thresholds, percentiles, or brand-by-brand comparisons.
Key numbers
The worker extracted the full PDF text with layout preservation twice and compared extraction hashes before commit. The following lines are copied from numeric/table-bearing regions of the PDF and retain the source units and wording where legible:
- historic point sources.1 Over 90% of atmospherically deposited both of which cause elevated groundwater levels, increased soil
- and likely MeHg formation and mobilization�caused by these ing Information, Table S1). The data were collected to identify
- develop after harvest,25 but erosion of soil-bound Hg can catchment; (2) decreasing mean elevation above the stream of
- = 21) and selective cutting (n = 2; Supporting Information, decadal time scales.
- Table S1). The 23 catchments included in this study originated All catchments were visited between May 2019 and October
- streams and artificial ditches. The catchments are distributed project leaders (Supporting Information, Table S1). In each
- forest (Supporting Information, Table S1). The site names immediately after harvest and were evaluated from conditions
- and FI7-CcSpShRh. Catchment sizes ranged from 0.5 ha and therefore served as a machine-free protection zone.
- Information (Table S2). organic soil horizon and the upper 5 cm of the mineral soil
- i.e., 4−22 years before the field visits of this study. We have (see the Supporting Information, Table S3). Single-use nitrile
- each core. Mean depths of the organic layer were calculated Cc, SE1-Lt, SE4-CcSp, SE5-CcSp, SE6-Cc, FI1-CcSp, FI2-
- The measurements (n = 12) were performed in groundwater concentrations in unharvested areas using a Control-Impact
- extraction with HNO3. Both the lab at NDSU and SLU excluded from the ΔMeHg/THg (n = 7) and ΔTHg/TOC (n
- measured THg concentrations in the soils with a Direct Hg = 5) OPLS analyses (see the Supporting Information, Table
- relation to the catchment area (% clear-cut). The hillslope identified as most influential for the model.55 While the VIP
- catchment (DHg) (ng/L) (MeHg) (ng/L) or (DHg) (%) (MeHg) (%) gradient (°) proportion (%) (1−5)
- Table S1). The hillslope gradient was calculated as the slope between the highest and lowest point in the harvested area. The proportion of the
- catchment that was harvested is a percentage of the full catchment. The soil disturbance classification from after the forest harvest ranges from 1 to
- not surprising, as we have data from rather few sites (n = 16)
- with rather many explanatory variables (n = 13). Also, some
- responses reported in the original studies (Table 1).
- Supporting Information, Table S6). These variables described Figure 2. First two components in the OPLS models explaining the
- analyses (Supporting Information, Table S6). Wheel ruts and stump harvest, but heavy disturbance does not necessarily
- elevated MeHg concentrations in stream waters by creating 3.1.2. Depth of the Organic Soil Layer and Mean
- increase of MeHg concentrations in stream waters after forest ditch water in the original study (Table 1).31 A high content of
- CcSp) had the highest soil disturbance classification (5) after bearing capacity.23 However, the mean penetration depth was
- the forestry operations (Table 1). However, this impact was not related to ΔMeHg/THg in the OPLS analyses.
- catchment with low hillslope gradient, the existing discharge 3.1.5. Soil Nutrient Status. The N content (%) of the soil
- little expansion of the discharge area and additional influence The catchments with highest N content (>1.8%; CA1-Cc, FI2-
- in stream waters prior to forest harvest, which may be the case had a C/N of 25 or lower (Supporting Information, Table S5).
- effects are less detectable.38 Even if forestry activities create quality that can drive MeHg formation.27,28 Studies of wetland
- high runoff rates that could promote MeHg mobilization to the varied between 24% (FI3-CcSp) and 100% (US4-Cc, US5-
- stream but may be counteracted by small areas of elevated CcRh, and FI5-CcSpShRh; Table 1), but this measure did not
- catchments with significant forest harvesting effects ranged Furthermore, MeHg stream water concentrations at site SE1
- between 1.1° and 8.7°, with a mean value of 4.7° (Table 1 and with only 4% harvested proportion in the catchment (not
- the lack of MeHg formation in the very steep (>15°) S2) increased by 340% after harvest activities. Although the
- trees left after forest harvest (US1-Cc, CA2-Sc, CA3-Sc, SE5- used instead of clear-cutting, with 30−50% of the basal area
- CcSp, and FI1-CcSp; Supporting Information, Table S1) or harvested. When not all trees are removed, the hydrological
- Supporting Information, Table S1). With little riparian increased mobilization of particle-bound Hg. Selective cutting
- MeHg formation hotspots close to the stream. No forestry at CA3-Sc (Table 1).
- the OPLS analyses. Based on catchment characteristics, CA1- two significant components that explained 69% of the
- Supporting Information, Table S7). Another study found that measures all created different conditions for Hg cycling.
Methods (brief)
- harvest may further increase the risk of elevated MeHg study, we collected soil samples and other site-specific data and
- and likely MeHg formation and mobilization�caused by these ing Information, Table S1). The data were collected to identify
- and straightened channels) water courses were sampled in the Information about types of trees present before the harvest, i.e.,
- mechanical site preparation (Sp), stump harvest (Sh), logging because the same person (K. Eklöf) collected the data from all
- (US4-Cc and US5-CcRh) to 785 ha (CA3-Sc). 2.3. Soil Sample Collection and Field Measures. Soil
- Forest harvest methods and subsequent forest operations samples were collected for chemical analyses from each
- US4-Cc, and US5-CcRh) or by mechanized harvesting however, no stream, as shallow groundwater samples were
- operations (all the rest). Cable logging was used in US1-Cc, collected in the original study. All soil samples were collected
- US2-Cc, and US3-Cc. Heavy forestry machines, including from the harvested area. Along each transect, samples were
- harvesters and forwarders, were used in the Fennoscandian and collected in three different zones: one in the perennial
- CcSpShRh. A detailed description of the forest operations location, samples were collected using a stainless steel soil
- 2.2. Field Observations of Site Characteristics. We horizon. Samples from the three transects were pooled per
- identified important site-specific characteristics that are zone, i.e., three samples of the organic layer from the discharge
- indicative of the relative sensitivity of an area to forest harvest, area were pooled into one sample and so on. In total, six
- as evidenced by increased THg and MeHg concentrations in pooled samples from each catchment were collected, except
- soil core were collected into new polypropylene Falcon tubes boxTool version 1.4.0 (Whitebox Geospatial Inc.) in ArcGIS
- USA and Canada, samples were shipped to the Forestry catchment following Lindsay (2016).52
- Forest Service Northern Research Station in Grand Rapids (for original studies, we collected data only for the harvested
Implications
This page makes the source discoverable for category-level evidence routing. Values remain source-native and should be used only with the stated matrix, species, basis, geography, and censoring context from the paper. The page does not convert total mercury to methylmercury or use total arsenic as inorganic arsenic.
Wiki pages this source may touch
Verification notes
- Identity check: DOI, raw handle, candidate cite-key, and SHA-256 were compared against existing
wiki/sources/pages before creation. - Full-PDF read:
pdftotext -layoutwas run on the full PDF twice; extracted text hashes matched before the page was written. - Numeric verification: numeric/table-bearing lines were selected mechanically from the verified extraction and preserved without unit conversion or rounding.
- Brand firewall: the worker skips PDFs when extracted numeric lines appear brand/manufacturer-sensitive; this page contains category-level or species-level evidence only.
- HMTc firewall: no threshold, percentile, pass/fail, clean/dirty, or certification math is stated.
Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.