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:
- index (55.1%) was observed in the Nura River (“marginal water category”). Coal, soil, non-
- 25 populated cities in the country with ~320,000 citizens, consists of the Ural River water by 60% (4). In the summer of 2019, Uralsk
- than 40% of Kazakhstani citizens (>3.6 million people) live in rural areas (2,18). Assuming that most of them consume contaminated
- sampling points. The coordinates of each sampling point are provided in Tables S1–S3 in Supplementary Information (SI). As can be
- different water basins. Geographical information about the studied rivers is provided in Table 1. More detailed geographical infor
- polymer containers prewashed with nitric acid. Surface water samples were taken at a depth range of 0.1–0.5 m and within the
- temperature range of 0–30.2 ◦ C. From 8 sites along the Syr-Darya River, 724 water samples were collected. The largest number of
- below the limit of detection (LOD) of the analytical equipment used. The percentage of non-detects among 11 metals in three rivers is
- given in Table S4. 30% censoring was chosen as the maximum allowable censoring limit for the analysis of the data. The censored
- half of their respective detection limit (HDL) (27–29). Limits of detection (LOD) for each respective metal were chosen as the lowest
- detected concentration of the corresponding metal among datasets from three rivers (Table S5). Detailed information about the
- and were provided in Table S9. The following Formula (1) was then used to calculate the water quality index for each river.
- factors for oral and dermal exposure routes, which were used in the calculation of TS were provided in Tables S10 and S11.
- version factor (L/cm3 ); ET is the exposure time (h/event); Oral and dermal intakes are expressed in terms of mg/kg of body weight/
- The threshold range for carcinogenic risk was taken as 10− 6 − 10− 4 (31).
- Deterministic risk assessment was calculated based on median, mean, maximum, and 95th percentile concentrations of heavy
- ministic and stochastic risk assessments were provided in Table S12 for both age groups.
- 2 abundant Cr (VI) metal (170 μg/L). The least abundant metal in the Syr-Darya River is Hg which was detected with a median
- concentration of 0.02 μg/L and a maximum concentration of 0.08 μg/L. The distribution of trace metals in the Syr-Darya River is wide.
- Coefficients of variance ranging from 28.5% for Cu to 99.0% for Co prove that point concentrations of heavy metals were extensively
- River is 800 μg/L, the median is 96.7 μg/L, and the mean is 158.1 μg/L. Fe metal concentrations are extensively dispersed around the
- mean value with a coefficient of variation of 107% and a positive skewness. As was observed in the Syr-Darya River, the contaminant
- present at the lowest concentrations in the Nura River is Hg. Its maximum concentration in the river is 2.33 μg/L, and the median
- concentration is 0.03 μg/L. Point concentrations of Hg demonstrate the greatest dispersion around the mean value with the CV of
- 194%. Distribution curves of all heavy metals detected in the Nura River show positive skewness. This indicates that outliers of the
- up to 142%. Since Hg was absent in the analysis for the Ili River due to the numerous non-detects (55.6%), the least abundant con
- taminants in the river were Cr (VI) and Ni at mean detected concentrations of 0.91 μg/L and 0.81 μg/L, respectively.
- that exceeded Kazakhstan’s and US EPA limits (0.3 mg/L) were detected in four seasons. The highest concentrations were found in the
- spring and summer seasons. Among 502 samples checked for Fe content in the Syr-Darya River, 1.39% exceeded relevant regulations.
- seasons. 17.7% of checked samples were registered with unacceptable Fe concentrations. In the Nura River, among 482 water samples
- checked for Fe content, 19.5% exceeded Kazakhstan’s and US EPA standards. The magnitude of heavy metal concentrations varied in
- the range of 1.03–2.67 MAC. The lowest concentration of Fe was registered in winter in three rivers. Therefore, Fe content in the rivers
- River checked for Cd content, 41.4% of them showed concentrations higher than MAC set by Kazakhstan (1.1–3.5 times MAC). Un
- The variation of Cr (VI) in the Syr-Darya and Ili Rivers is depicted in Fig. 4. US EPA set MAC for Cr (VI) as 0.1 mg/L, while
- Kazakhstan and WHO set this threshold value as 0.05 mg/L. The highest concentration of Cr (VI) in the Syr-Darya River was observed
- in spring. 4.5% of 493 samples from the Syr-Darya River had Cr (VI) content which exceeded Kazakhstan’s MAC in all seasons by
- 1.2–3.4 times. Concentrations of Cr (VI) registered in the Ili River were within the acceptable range.
- Fig. 5 illustrates seasonal concentrations of Hg detected in the Syr-Darya and Nura Rivers. No unacceptable concentrations of Hg
- exceeding the concentration limits. Nevertheless, the percentage of these unacceptable values was low (0.85%) compared to the
- across rivers. This can be explained by the spatial variation of metals. In total, 64.4% of water samples from the Nura River contained
- were above the US EPA regulation, exceeding it by 1.02–1.5 times in 1.24% of all samples.
- centrations that exceed domestic and international regulations. The maximum concentration of Fe in the Ertis River was 0.71 mg/L,
Methods (brief)
- Seasonal variations Ili Rivers). Water samples were collected from three rivers within the 2014–2019 period by the
- rising. Previous studies determined concentrations of various heavy metals from water and fish samples in large water bodies in
- to Kazakhstan governmental sampling technical standards (25), the RSE “Kazhydromet” constantly collected surface water samples
- Syr-Darya, Nura, and Ili Rivers are demonstrated in Fig. S1, Fig. S2, and Fig. S3, respectively. Water samples were collected in 250 mL
- polymer containers prewashed with nitric acid. Surface water samples were taken at a depth range of 0.1–0.5 m and within the
- temperature range of 0–30.2 ◦ C. From 8 sites along the Syr-Darya River, 724 water samples were collected. The largest number of
- samples (2437 samples) were taken from 14 sampling sites along the Ili River. And in the Nura River, 2011 water samples were
- collected from 19 sampling sites. All collected samples were delivered to the laboratory at a cooling temperature of 2–5 ◦ C in amber
- In the laboratory, the presence of metals (Fe, Hg, Cd, Pb, As, Cu, Zn, Cr, Ni, Co, and Mn) in water samples was analyzed, according
- to the governmental standard (26). By this standard methodology, one part of the water samples was filtered through the 0.45 μm
- forms in water samples. Another part of the water samples was heated with an excess of nitric acid and hydrogen peroxide. Prepared
- solutions were filtered through the 12.5 cm filter paper and further directed to analyze the sample’s mass fraction of all metal forms.
- Analytical identification and quantification of the heavy metals in the samples were performed by flameless atomic absorption
- below the limit of detection (LOD) of the analytical equipment used. The percentage of non-detects among 11 metals in three rivers is
- half of their respective detection limit (HDL) (27–29). Limits of detection (LOD) for each respective metal were chosen as the lowest
- the guidelines for the total number of chosen parameters. The frequency (F2 ) represents the percentage of individual samples (tests)
- and TOC on the metal accumulation in surface sediments and soil samples (33,34). Therefore, the distance between sampling points is
- spring and summer seasons. Among 502 samples checked for Fe content in the Syr-Darya River, 1.39% exceeded relevant regulations.
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.