Beibei Hu

Health risk assessment on heavy metals in urban street dust of Tianjin based on trapezoidal fuzzy numbers

ABSTRACT The aims of this article were to investigate heavy metals concentrations in urban street dust of Tianjin, to examine spatial variations of heavy metals pollution, and to assess their health risk to local populations. Urban street dust samples were collected from 144 typical crossroads in an urban area of Tianjin. Levels of heavy metals were determined by atomic absorption spectrophotometer analyzer. Given comprehensive consideration of the complexity and uncertainty of health risk assessment, trapezoidal fuzzy number was introduced to assess the health risk of heavy metals in the urban street dust of Tianjin. The results showed that the pollution of heavy metals in the urban street dust of Tianjin was serious. The relatively serious metal pollution tended to be located in the center, north, northeast, and southeast of the study area. The research indicated that heavy metals in street dust had caused non-cancer hazard to children but had not caused non-cancer or cancer hazard to adults. The direct ingestion of dust via hand-mouth contact behaviors was the major exposure pathway for health risk.

Carbon dioxide and methane dynamics in a human‐dominated lowland coastal river network (Shanghai, China)

Evasion of carbon dioxide (CO2) and methane (CH4) in streams and rivers play a critical role in global carbon (C) cycle, offsetting the C uptake by terrestrial ecosystems. However, little is known about CO2 and CH4 dynamics in lowland coastal rivers profoundly modified by anthropogenic perturbations. Here, we report results from a long-term, large-scale study of CO2 and CH4 partial pressures (pCO2 and pCH4) and evasion rates in the Shanghai river network. The spatiotemporal variability of pCO2 and pCH4 were examined along a land-use gradient and the annual CO2 and CH4 evasion were estimated to assess its role in regional C budget. During the study period (August 2009 – October 2011), the overall mean pCO2 and median pCH4 from 87 surveyed rivers were 5846±2773 μatm and 241 μatm, respectively. Internal metabolic CO2 production and DIC input via upstream runoff were the major sources sustaining the widespread CO2 supersaturation, coupling pCO2 to biogeochemical and hydrological controls, respectively. While CH4 was oversaturated throughout the river network, CH4 hotpots were concentrated in the small urban rivers and highly discharge-dependent. The Shanghai river network played a disproportionately important role in regional C budget, offsetting up to 40% of the regional terrestrial net ecosystem production (NEP) and 10% of net C uptake in the river-dominated East China Sea fueled by anthropogenic nutrient input. Given the rapid urbanization in global coastal areas, more research is needed to quantify the role of lowland coastal rivers as a major landscape C source in global C budget.

Greenhouse gases emission from the sewage draining rivers

Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) concentration, saturation and fluxes in rivers (Beitang drainage river, Dagu drainage rive, Duliujianhe river, Yongdingxinhe river and Nanyunhe river) of Tianjin city (Haihe watershed) were investigated during July and October in 2014, and January and April in 2015 by static headspace gas chromatography method and the two-layer model of diffusive gas exchange. The influence of environmental variables on greenhouse gases (GHGs) concentration under the disturbance of anthropogenic activities was discussed by Spearman correlative analysis and multiple stepwise regression analysis. The results showed that the concentration and fluxes of CO2, CH4 and N2O were seasonally variable with >winter>fall>summer, spring>summer>winter>fall and summer>spring>winter>fall for concentrations and spring>summer>fall>winter, spring>summer>winter>fall and summer>spring>fall>winter for fluxes respectively. The GHGs concentration and saturation were higher in comprehensively polluted river sites and lower in lightly polluted river sites. The three GHGs emission fluxes in two sewage draining rivers of Tianjin were clearly higher than those of other rivers (natural rivers) and the spatial variation of CH4 was more obvious than the others. CO2 and N2O air-water interface emission fluxes of the sewage draining rivers in four seasons were about 1.20-2.41 times and 1.13-3.12 times of those in the natural rivers. The CH4 emission fluxes of the sewage draining rivers were 3.09 times in fall to 10.87 times in spring of those in the natural rivers in different season. The wind speed, water temperature and air temperature were related to GHGs concentrations. Nitrate and nitrite (NO3-+NO2--N) and ammonia (NH4+-N) were positively correlated with CO2 concentration and CH4 concentration; and dissolved oxygen (DO) concentration was negatively correlated with CH4 concentration and N2O concentration. The effect of human activities on carbon and nitrogen cycling in river is great.

Assessment of Heavy Metal Pollution and Potential Ecological Risk in Soils of Tianjin Sewage Irrigation Region, North China

The aim of the study was to investigate heavy metals concentrations in wheat field soils of Tianjin sewage irrigation region, and evaluate the potential ecological risk of heavy metals pollution. ICP-OES was employed to analyze the heavy metals concentrations in wheat field soils of Tianjin sewage-irrigation region. The grading standard of Tianjin soil environmental quality was used as the assessment foundation for soils and Lars Hakanson’s potential ecological hazards index method was used to evaluate the heavy metals pollution potential ecological risk in soils. The results showed that: Cd concentrations in soils ranged from 0.03 mg•kg-1 to 1.17 mg•kg-1, with an average value of 0.46 mg•kg-1; Zn concentrations in the soils ranged from 62 mg•kg-1 to 307 mg•kg-1, with an average value of 129.08 mg•kg-1. The concentrations of Cd and Zn in the soils exceeded second grade standards of Tianjin soil environment quality, so the soil was polluted. The other heavy metal elements, such as Cu, Pb, Cr and Ni, were all lower than second level of Tianjin soil environment quality standards, meaning that the soil was not contaminated by these heavy metals. The heavy metal concentrations were relatively rich in saline wet fluvo-aquic soil and clayification fluvo-aquic soil. Based on Lars Hakanson’s potential ecological hazards index method, Cd had heavily ecological risk in soils and was the main pollutant, while the other heavy metals had lightly ecological risk. Ecological risk of total heavy metals pollution was moderate. The heavy metals were most likely from wastewater irrigation. The pollutants in the soils came mainly from sewage irrigation. The waste water treatment technology should involve steps to remove heavy metals causing risk to human health.