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The vegetable greenhouse soils in Yanglou Town, Ruzhou City, Henan Province were taken as the research object in the present study to explore the difference in soil physical and chemical properties and the total and fraction of heavy metals of different planting years. The potential ecological risks of heavy metals in greenhouse soils with different planting years were assessed by using single and comprehensive potential ecological risk index methods. The results showed that the soil pH of vegetable greenhouses increased, and fertility factors such as organic matter, available phosphorus, and alkali-hydrolyzable nitrogen accumulated to a certain extent compared to the control group, whereas catalase showed a decreasing trend. Correlation analysis showed that the planting years were significant positively correlated with pH ( P <0.05) and organic matter ( P <0.01) and significant negatively correlated with catalase ( P <0.01). The amount of heavy metals in the vegetable greenhouse soils increased with the increase in planting years, among which Cu, Zn, and Cd increased most obviously, with maximum increases of 129.14%, 204.17%, and 161.11%, respectively. The proportion of acid-soluble and reducible heavy metals in the vegetable greenhouse soils also increased gradually with the planting years, and the proportion of residual heavy metals decreased correspondingly, which resulted in the heavy metals transforming into fractions easily absorbed by plants. The results of the single potential ecological risk index showed that Cd in vegetable greenhouse soils had a strong ecological risk with the increase in planting years, whereas Cu, Pb, Zn, and Ni were in the mild risk category. The comprehensive potential ecological risk index showed that the heavy metals in the vegetable greenhouse soils of different planting years have reached a strong or very strong ecological risk.

Surface farmland soil samples were collected from 135 different sites in a 64 km 2 area around a lead and zinc smelter in Jiaozuo City, China. The concentration of the selected heavy metals (Cu, Zn, Pb, Cr, Cd, Ni, V, and Co) was analyzed and the spatial distribution of these heavy metals in the farmland was determined using the kriging interpolation technique (ArcGis 10.1). The enrichment factor, potential ecological risk model, and potential health risk model were used to assess the contamination level and potential risk of heavy metals in farmland surface soil. The results show that the average contents of Cd, Pb, Cr, and Zn in farmland soil are higher than the background content of these metals in the Henan Province and the average content of Cd is 2.8 times higher than that of class Ⅱ of the environmental quality standard for soils in China (GB 15618-1995). The heavy metal contamination in the west of the study area is higher than that in the east and the soil around the lead and zinc smelter (within 3 km) is severely contaminated with Pb and Cd, which is consistent with the location of the industries causing the pollution. The enrichment factors show that the soil is severely contaminated with Cd; partial sampling points are seriously contaminated with Pb, Cu, and Zn; the Cr and Co pollution is small; and Ni and V are almost not affected by human activities. The results of the risk assessment indicate that Cd poses serious ecological and health risks, Pb and Cu pose serious ecological risks, and Cr poses a serious cancer risk.

Fifty-two dust samples were collected from four parks [Longting Park (P(L)), Tieta Park (P(T)), Qingmingshanghe Park (P(Q)), Xiangguosi Park (P(X))] located in Kaifeng City, China. Concentrations of Hg and As in dusts were measured by atomic fluorescence spectrometry (AFS), while Cr, Cu, Zn, Pb, Ni and Cd were analyzed by inductively coupled plasma mass-spectrometry (ICP-MS). The heavy metal pollution of dust was assessed using Geo-accumulation index (Igeo) and pollution load index (PLI). The health risk due to exposure to heavy metals in dust was assessed using the model recommended by USEPA. The non-carcinogen (HI) and carcinogen health risks (TCR) were also calculated to evaluate the potential risks to adults. The results showed that the average contents of Hg, Cu, Zn, Cd and Pb were much higher than those in control samples and the background values of fluvo-aquic soil in China. The samples were seriously polluted by Hg and Pb, besides, there was.moderate pollution, slight pollution of Cu and Zn, and no pollution of As, Cr and Ni. The PLI from the 4 Parks indicated that there was serious heavy metals pollution of dust in P(X), moderate pollution in P%, and slight pollution in P(T) and P(Q). The average HI of heavy metals in the four Parks was lower than one. The average HI decreased in the order of P(L) > P(X), > P(T) > P(Q), while the average TCR decreased in the order of P(L) > P(Q) > P(x) > P(T). The contribution rate of HQ(As) to HI was about 43.51% , and that of CR(As) to TCR was about 70.11%.

This investigation selected the city of Nanjing, Jiangsu province of China, as the study area, and analyzed the concentrations of organic carbon (OC) and black carbon (BC) of ten soils profiles in three different groups, by wet chemical oxidation methods. The results showed that the concentration of BC ranged from 0.22 g x kg(-1) to 32.19 g x kg(-1) in all urban soil profiles, and the average concentration of BC reached 4.35 g x kg(-1). The average concentration of BC of the first group from ancient residential areas was 0.91 g x kg(-1), and that of the second group affected by ancient industrial activities was 8.62 g x kg(-1), the third group influenced by the modern industrial and traffic emission was 3.72 g x kg(-1). The ratio of BC/OC ranged from 0.03 to 1.59 in all profiles, and the average was 0.29. The average ratio of BC/OC of three groups appeared in this order: the highest exists in the second group, followed by the third group, and the last is the first group. These data mean that some BC particles produced by local biomass and/or fossil fuel burning due to the industrial and transport activities during urbanization are recorded in soils. In addition, the contents of BC and the ratio of BC/OC may reflect different processes of human activities and pollution intensities of urban soils. It is concluded that the soil BC in urban area is mainly coming from fossil fuel burning, more specifically, BC in surface layer (present layer) is mainly from the exhaust particles of motor vehicles (especially diesel engine), while in ancient layer (cultural layer) it is possibly related to the historical coal use.

The vertical distribution of heavy metals in soils profiles is a result of heavy metals accumulation and migration under combining influence of edaphic factors and environmental conditions. It's an important basis for evaluation of heavy metals pollution and remediation of contaminated soils. By traditional sampling methods, i.e., soils were sampled according to pedogenetic horizons, only very general information about element migration can be learned. In the current study, three sites near a steel factory were selected to represent three types of land use, i.e. forest, dry land for vegetable cultivation and rice paddy field. Soils were sampled horizontally by high-resolution sampling method. In the top of 40 cm soils were sectioned in 2 cm intervals, then 5 cm intervals in next 40 cm, and 10 cm intervals in the last 20 cm of profile. Total content of Cu, Zn, Pb, Cr and Cd were determined, and the vertical distribution of Cu, Zn, Pb, Cr, Cd in every profile was analyzed. The results indicated that enrichment of heavy metals appeared in the upper most layer of the natural forest soil that without any anthropic disturbance, and this phenomenon proved that heavy metals were coming from atmospheric deposition. We found that Cu, Zn and Pb moved downward in a short distance, Cd migrated relatively faster than Cu, Zn and Pb, while Cr had no recognizable location of migration front. In the soil profiles of dry land and paddy field, there were influences of agricultural practice, the distribution and movement of metals were thus different form those of the forest soil. In cultivated layer heavy metals were evenly distributed because soils in the upper layer were mixed by cultivation, however, bellow the cultivated layer obvious migration took place again. It is concluded that different heavy metals have different mobility and there is such a relative order: Cd>Cu>Zn>Pb. The study shows that the distribution pattern can be obtained with the currently adopted high-resolution sampling method, than traditional horizon sampling, and more precise migration distance and rates can be estimated.