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Particle Size Dependent Heavy Metals in Road Dusts from Maanshan City, China
Siping Niu,Xiaolong Song,Jianghua Yu,Xuan Wang,Jianjun Lian 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.5
In this study the road dusts (RDs) <1,000 μm from Maanshan City, China were characterized from the prospects of size fractionated pollution by heavy metals (HMs). Particulates with size <75 μm, 75 − 125 μm, 125 − 250 μm, 250 − 500 μm and 500 − 1,000 μm averagely accountedfor 35.7±11.7%, 14.6±11.0%, 25.3±12.5%, 11.6±8.8% and 12.8±12.9% of the total weight, respectively. This result implies the gravimetric percentage was overall declined with increasing granular size, following gamma distribution function (p < 0.001). It was observed that the highest contents of Zn, Ni, Pb and Cd occurred with the fine RDs <75 μm while Cu with these <125 μm, suggesting HMs preferred to be associated with the fine particulates. Cu, Zn, Ni, Pb, Cr and Cd were present in RDs with bulk contents of 68±30 mg/kg, 285±122 mg/kg, 23±16 mg/kg, 53±21 mg/kg, 432+297 mg/kg and 0.56±0.39 mg/kg, which resulted in geo-accumulation index (Igeo) values as -1.04, 2.35, -2.38, 0.38, 1.54 and 0.18, respectively. Hence, it can be concluded that the RDs had only been significantly polluted by Zn. Person correlation analysis suggests those HMs ubiquitously present in RDs had size-dependent sources.
Effect of sampling duration on the performance evaluation of a stormwater wetland
Niu, Siping,Park, Kisoo,Kim, Youngchul IWA Publishing 2015 Water Science & Technology Vol.71 No.3
<P>In this study, the effect of sampling duration on the performance estimate for a stormwater wetland over both rainy and dry days was evaluated for the appropriate design of sampling duration. As the cumulative percentage volume (V-p), the ratio of cumulative stormwater volume concerning time to the total stormwater volume, varied between 60 and 100%, generally, the inflow total suspended solids, turbidity and total chemical oxygen demand (TCOD) event mean concentrations (EMCs) did not vary significantly, whereas the total nitrogen (TN) and total phosphorus (TP) EMCs were relatively stable. Compared to the inflow, the corresponding outflow EMCs changed much less as V-p changed. And these variations both from inflow and outflow EMCs did not result in significant changes in the removal efficiencies. The investigation during the dry days between two consecutive storm events showed that outflow pollutants did not change to a considerable extent after 1 day of the previous rainfall event. This study identifies the possibility of shortening the rainy sampling duration, because the performance of stormwater wetlands is usually estimated based on removal efficiencies rather than pollutant concentrations. Also, the sampling during dry days should be performed at least 1 day after a rainfall event.</P>