Study of zinc pollution in river water: Average mass balance based on irrigation schedule

Abstract

Aichi Prefecture, which has a dense industrial area, is one of the sites in Japan where the levels of zinc are elevated. However, currently, there is no clear evidence of the source of zinc in this prefecture. This study aims to assess zinc concentration and load in a river and identify the main sources of zinc pollution. We conducted a 20‐month survey to identify the temporal and spatial variation of zinc in river water, particularly in the Aizumame River. Using Flame Atomic Absorption Spectrometry, the total fraction of zinc concentrations was determined for nine sampling stations (five points in the mainstream and four points in the tributaries). The results show that the average of zinc concentration was lower during the irrigation period than in the non‐irrigation period. However, the load during the irrigation period was higher. During irrigation, the river discharges were higher resulting in a lower concentration. The highest zinc concentration was 0.139 mg/L in June 2017. Based on this study, the main zinc source was identified from industrial areas which on average contributed about 3,400 g/day into the mainstream. These results became more evident during the non‐irrigation period when only industrial discharges contributed zinc load into the mainstream.

An Assessment of Zinc Fluxes by Analyzing Monthly, Weekday, and Weekend Levels in a River

“…The industrial point sources may have contributed at least 67% of the total Zn fluxes (37 g km −2 d −1 ) and 70% of the D‐Zn fluxes (35 g km −2 d −1 ) on weekdays. Meanwhile, the industrial area along the Aizumame River in the Aichi Prefecture, discharged ≈68 g km −2 d −1 (57%) in 2017; [ 20 ] much higher than in the case of the Umeda River. Wen et al.…”

“…The river discharges were measured and calculated using a velocity‐area method according to Andarani et al. [ 20 ]…”

“…Previous research revealed that surveys undertaken on weekdays exhibited higher concentrations of contaminants. [ 20,21 ] Furthermore, Andarani et al. [ 20 ] found that throughout 2017, Zn concentrations in the most downstream point in the Aizumame River, located in Aichi Prefecture, exceeded the EQS.…”

“…[ 20,21 ] Furthermore, Andarani et al. [ 20 ] found that throughout 2017, Zn concentrations in the most downstream point in the Aizumame River, located in Aichi Prefecture, exceeded the EQS. The Zn fluxes in the Aizumame River were found to mostly originate from point sources of industrial wastewater, which contributed about 77.3 g km −2 d −1 .…”

“…The Zn fluxes in the Aizumame River were found to mostly originate from point sources of industrial wastewater, which contributed about 77.3 g km −2 d −1 . [20] The Zn concentrations in the river may also become elevated due to point or non-point (diffuse) sources. [19,22] Given that industrial facilities do not operate on weekends and holidays, it was possible to estimate the contribution of industrial point sources to the river by comparing the measurement results between weekdays and weekends.…”