Industrial Soil Along the Turag River Carries the Sharpest Heavy Metal Burden
Rapid industrial expansion in Gazipur District has left a measurable mark on the Turag River corridor. Soil and water collected from 18 sites in industrial and non-industrial zones showed a contamination pattern in which manganese and zinc dominated overall concentrations, while nickel and zinc became far more concentrated in the industrial belt near the river. The signal was not random. Spatial mapping, principal component analysis, hierarchical clustering, and correlation testing all pointed toward a common anthropogenic footprint in the industrial zone, especially near its northern boundary, where the heaviest clustering appeared. In the non-industrial sites, the distribution was more diffuse, consistent with multiple lower-intensity influences rather than a single dominant discharge source.
The study centers on five metals: Hg, Ni, Mn, Zn, and Co. Among them, nickel drew the most concern because its soil concentration pattern aligned most tightly with industrial activity. Zinc tracked alongside it, while mercury and cobalt remained part of the broader contamination profile rather than the strongest spatial drivers. In environmental toxicology, that type of clustering matters because it suggests shared release pathways from manufacturing, effluent discharge, or waste handling rather than background geochemistry alone.
Nickel Dominance in the Industrial Zone Raises the Most Concern
Soil means followed the same order in both zones: Mn > Zn > Ni > Co > Hg. The ranking itself is not the critical story. The concern lies in how nickel and zinc rose sharply in the industrial area and became spatially concentrated, while the non-industrial sites showed a less intense and less tightly focused distribution. Industrial wastewater is the most plausible pathway here, especially in a district with textile, dyeing, pharmaceutical, and metal-processing activity. Those sectors commonly generate heavy-metal-bearing waste streams, and untreated or partially treated effluent can carry contaminants into soil, sediment, and adjacent water.
The analysis also used inductively coupled plasma-mass spectrometry, which gives the study the analytical sensitivity needed to detect trace-level metals across a complex river corridor. Statistical clustering then helped separate likely shared sources from more scattered inputs. In practical terms, the industrial zone behaves like a contamination hotspot, not a uniform smear across the district. One sentence captures the pattern plainly: nickel and zinc clustered where industrial pressure was strongest.
Children Carried the Highest Modeled Soil Exposure
The human health assessment was restricted to non-carcinogenic risk, using chronic daily intake, hazard quotient, and hazard index models based on USEPA methods. Children consistently showed higher modeled soil intake than adults. In toxicology, body size, hand-to-mouth behavior, and soil ingestion assumptions can magnify exposure estimates in younger age groups, which is why pediatric risk screening often reveals the earliest warning signs of environmental harm.
The strongest signal came from nickel in the industrial zone, where the modeled hazard quotient reached 1.66 for children. The cumulative hazard index for children also exceeded the screening benchmark of 1 in both zones, measuring 2.32 in the industrial area and 1.31 in the non-industrial area. Those values do not diagnose illness in residents, but they do indicate that, under the model’s assumptions, combined soil exposure could be concerning for children. Adult estimates were lower, yet the child-focused pattern is enough to justify environmental follow-up.
The finding is especially relevant because the calculations were based on the < 0.5 mm soil fraction collected at 15–20 cm depth. That sampling approach is useful for environmental characterization, but it may not represent the exact soil that children contact at the surface, nor the airborne dust they inhale or ingest during daily activity. The modeled risk therefore deserves interpretation as a screening signal rather than a direct measurement of real-world dose.
Water Exposure Looked Less Dangerous Than Soil in This Survey
Water told a different story. All modeled hazard quotient and hazard index values for water remained below 1, which stayed under the study’s screening benchmark. This does not mean the water was clean; it means the calculated non-carcinogenic risk from the sampled water did not cross the threshold used in the model. Soil was the more troubling exposure medium, and the contrast between soil and water suggests that deposited contamination and sediment-bound metals may be more important than direct ingestion of river water in this setting.
That pattern fits the behavior of heavy metals in industrial river systems. Metals can settle into soil and sediment, persist there, and later re-enter food chains or dust pathways. A child living near the river may therefore face more risk from contaminated soil contact than from water alone, particularly in areas where industrial discharge has had time to accumulate on land surfaces and river margins.
Source Patterns Point Toward Industrial Control, Not Generalized Background Pollution
The combined PCA, HCA, correlation analysis, and spatial mapping support a common industrial source pattern in the contaminated zone. In contrast, the non-industrial sites appear to reflect a broader mixture of influences, likely including hydrological connectivity through the river system and possible movement of contaminants from upstream areas. Even so, the industrial zone stood apart in both concentration and spatial focus. The northern boundary of that zone carried the strongest signal, which is consistent with localized discharge or concentrated runoff entering the system at a particular point rather than a broad regional background trend.
That difference has direct policy implications. If the source is industrial effluent, the response has to include better waste treatment, discharge control, and site-level monitoring around the most affected river stretches. Environmental surveillance should not stop at the river water. Soil, sediment, and dust near residential and industrial margins all matter because they determine how contamination reaches people over time.
Peri-Urban Bangladesh Needs Child-Focused Environmental Surveillance
Gazipur has become one of Bangladesh’s most industrialized peri-urban districts, and the Turag River now functions as both a receiving waterway and an exposure corridor. This study adds evidence that the burden is not evenly spread. Industrial land use appears to intensify contamination, especially for nickel, and modeled child risk in soil exceeds the benchmark used in the analysis. The public health relevance is straightforward: children living near industrial riverbanks may be encountering a heavier environmental burden than adults, even when water estimates look less alarming.
The work also has a narrow but important limitation. Because the risk estimates were built from a specific soil fraction and sampling depth, they should not be read as a complete measure of human exposure at ground level. Airborne dust, surface soil, and food-chain transfer were outside the model’s direct reach. Even so, the study provides a concrete environmental warning for industrializing districts along the Turag River: source control, not passive observation, is the next step if local authorities want to prevent continued accumulation of heavy metals in children’s living environment.