Keywords: ants: (i) biochemical oxygen demand (BOD) and ammonia; (ii) heavy metals; (iii) sewage-associated organic pollutants

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:

Acidiﬁcation pathway. The 1990s saw general reductions in mean concentrations of metals, BOD and ammonia (driven by the EU
pears to be associated with an improvement in ASPT (Johnson et al., 2019). This pattern is illustrated more generally in mean annual data for the
Fig. 2 presents a relative index of average annual occupancy for six inverte- ing stations with a mean annual discharge of >2 m3 s−1, in order to
29 national recording schemes or societies, which were processed using metic mean ammoniacal nitrogen and BOD concentrations (and their vari-
Shaded areas show the 95 % credible intervals of the posterior distribution of the geometric mean. The reversal in the downward trend for four groups coincides with the
spills to have occurred on 926 out of 7160 days (13 %) reported as no-
Fig. 3. Mean annual concentrations of (a) total ammoniacal N (NH+
sites for which data were available. Error bars show the range between the 10th Heavy metals, such as mercury, lead, cadmium, nickel, zinc and copper
2016), some agrochemicals, storm runoff from urban surfaces (Barco Data on median annual concentrations of zinc, lead, copper and nickel
Macklin, 2003). Many metals have moderate to very high ecotoxicity, there is a clear decrease in both the median concentration (by approxi-
both on their own (Taylor et al., 2000) and when present as mixtures mately a factor of three or more in all cases) and the range over this period.
Fig. 4. Median (50th percentile) concentrations of selected metals in lowland GB rivers at the tidal limit from 1980 to 2013. (a) Zinc; (b) lead; (c) copper; (d) nickel. The error
toxicologically-relevant concentrations. They are also known as emerging 2006 and 2016, the total number of prescriptions increased by 47 %,
contaminants, in recognition of the fact that their presence has only re- with the number of prescriptions per person increasing by 35 %
cently been detected. They include chemicals used in human and veterinary (Moody et al., 2016). In 2015/16 48 % of adults in England were taking
pharmaceuticals (so called Active Pharmaceutical Ingredients or APIs: at least one prescription medicine with 24 % of the population taking
a high tonnage surfactant used in laundry detergents is >90 % for trickling classes being analgesics, antibiotics, antidepressants, antifungals, anti-
ﬁlter plants: Holt et al., 1998, and >99 % for activated sludge plants: inﬂammatories, β-blockers, estrogens, lipid regulators and morphine deriv-
example, Baronti et al. (2000) report mean removal rates for E2 and EE2 diazinon, copper and zinc, which are also emitted by other sectors)
of 87 and 85 %, respectively, and a mean removal of estrone of only 61 % human and veterinary medicines have not been included in regulatory
low concentrations (Rand-Weaver et al., 2013). A wide range of effects pounds can then be transferred to surface waters. There is also increasing
life in up to 50 % and 4.5 % of river reaches are at risk from ibuprofen cals, there have been various introductions of other compounds used
2009). Modelling-based studies have indicated that up to 38 % of river where the solid phase often carries a net negative charge.
structure described in Section 3.1. shows a marked increase in the latter part of the 19th century, stable con-
limiting (typically when the ratio of available N to available phosphorus 55 % of land in England (DEFRA, 2018) and 2.4 % in Wales. However, an
in marine systems (Howarth and Marino, 2006) which means that riverine “set aside”). Such conversion may be particularly effective in riparian buffer
Fig. 5. Nitrate N concentrations in the river Thames at Teddington from 1868 to 2008 (adapted from Howden et al., 2010). The grey line shows the mean monthly
Average nitrate N concentrations measured at the tidal limit in the HMS ably peaked in the late 1980s with STPP contributing approximately 50 %
fer of southern England) have very long solute residence times. This is par- in detergents in the UK reduced by approximately 40 % (Glennie et al.,
ticularly the case where there is a deep unsaturated zone with few 2002). By 2009, detergents were estimated to contribute only 18 % of the
opportunities for solute to by-pass the rock matrix, which means that pulses P load to sewers (UKWIR, 2009). A comparable ﬁgure of 21 % was esti-
rated zone nitrate transport in the Alton Pancras catchment in Dorset, dishwashing detergents to wastewater P was 23 %. The phase out of P in
Chesapeake Bay (Sanford and Pope, 2013). range of factors including crop type, land use history (including previous
the transfer of P from agricultural soils). A mean reactive P concentration (e.g. Bateman et al., 2011) in excess of agronomic requirements (often re-
as high as 80–90 % but is typically lower (Morse et al., 1998). Naden eutrophication thresholds (Holman et al., 2008; Holman et al., 2010). It
et al. (2016) estimated a range for effective P removal in secondary waste- also means that some soils may be able to meet crop P requirements with-
water treatment of 53–63 %, based on measured P concentrations, although out additional fertiliser application (particularly if so-called P activators
content is relatively high and hydrological pathways are active. This means 1950s, peaked in the late 1980s and have since declined to current levels
tion effect) also suggests that sewage remains a major contributor to ele- Since the 1930s, a wide range of synthetic organic compounds has been
median and mean annual losses for 97 pesticide AI measured in 23 drainage
a maximum of about 10 %. However, even these small fractions may be
1978 1983 1988 1993 1998 2003 2008 2013 activities such as textile treatments, vegetable processing (e.g. Xie et al.,

Methods (brief)

of the natural system to the stressor of interest. samples (or samples of aquatic indicator fauna such as macroinvertebrates)
Water quality is controlled naturally by the amount and origin of precip- need to be collected and analysed in the laboratory. This is often expensive
itation and the contact between water and the vegetation, soil and rock and time-consuming, which restricts the frequency at which samples are
through which it travels along hydrological pathways to aquifers, streams, collected in most locations. Furthermore, although water quality is
number of anthropogenic factors. These include the accidental and inten- limited prior to the 1970s. It should also be noted that samples are never
degraded, volatilised or sorbed to sewage sludge) will depend on their river water samples (Crathorne et al., 1984). Since the late 1990s, over
This is, in part, because quantitative analysis of pesticides in water samples thresholds mean that overall changes in concentrations have little ecologi-
ticides in samples collected as frequently as twice per week over the period result from the emission of ammonia (NH3), predominantly from agricul-
and 2012 in the Nant Teyrn stream, Snowdon, north Wales (based on approximately weekly samples collected for the UK Environmental Change Network: Rennie et al.,
with increased FIO concentrations, so the presence of FIOs in a sample sig- health concern. Datasets on speciﬁc pathogen concentration in British riv-
stretch of river will now be sampled each year to record FIO concentrations Important drivers which have resulted in the deterioration of water
Bateman, A., van der Horst, D., Boardman, D., Kansal, A., Carliell-Marquet, C., 2011. Closing benthic communities in Colorado mountain streams. Ecol. Appl. 10, 626–638.
ecological and contemporary diatom assemblage data. Ecol. Indic. 37, 365–380. mass spectrometry. Environ. Sci. Technol. 18, 797–802.
Enserink, E.L., Maas-Diepeveen, J.L., Van Leeuwen, C.J., 1991. Combined effects of metals; an Hynes, H.B.N., 1960. The Biology of Polluted Waters. Liverpool University Press, Liverpool.
1800–2010. Sci. Total Environ. 572, 1471–1484. by-products in drinking water: a review and roadmap for research. Rev. Mutat.

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 -layout was 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.

Commit	Date	Change	Description
b01ec52c	2026-08-04	major	2 sections added
d49e450f	2026-08-03	major	5 sections added; narrative text revised