Ecological and Health Risk Assessment of Heavy Metals in Farmland in the South of Zhangbei County, Hebei Province, China

Abstract

The distribution of heavy metals in the agricultural areas from a cattle-producing area near the Zhangbei Dam grassland, Hebei province, China, was investigated for providing the basis for the control of pollution in a rural farmland. Fifty-three surface soil samples including 28 soils of potato and 25 soils of oats were collected and analyzed for the distribution of Cd, Cu, Pb, Zn, Cr, As, Hg, and Ni. Furthermore, the ecological risk of soils contaminated with heavy metals was evaluated by employing the single factor index, the Nemerow comprehensive pollution index and geo-accumulation index, and potential ecological hazard index. The results showed that the contents of the eight heavy metals in soil planted with potato were below the risk screening values. The single factor index in soils planted with hulless oats showed that the concentrations of Cd, Hg, and Ni surpassed the Chinese screening limits by 8%, 4%, and 8%, respectively. According to the geo-accumulation index, 4% of samples reached the level of medium ecological risk for Cd. According to the results of ecological risk assessment, the studied soils generally showed a mild pollution degree. According to the health risks assessment results, the carcinogenic risks should be considered non-negligible. Arsenic is the dominant carcinogenic pollutant for human beings in the county. The main sources of pollution are mining and application of fertilizers.

Exposure Factors in Health Risk Assessment of Heavy Metal(loid)s in Soil and Sediment

“…Most researchers take into account all three pathways of exposure (ingestion, inhalation, and dermal contact) [96][97][98][99][100] when assessing the health risk; however, since inhalation has the smallest share of the risk [43,44,59], some researchers based their study only on ingestion [4,59] or ingestion and dermal contact [9,10,44,[101][102][103]. Several terms are used to define the chronic intake of HMs, such as the chronic daily intake (CDI) [47,66,70,76,98,104,105], the average daily intake (ADI) [36,40,73,93,106], and the most commonly used the average daily dose (ADD) [5,37,52,67,107-109]. Less frequently used indices are D [39,43], daily intake of metals (DIM) [80], and Exp [101].…”

“…Another term encountered is ADD total , which represents the sum of all three ADD for different routes of exposure [102,107]. The term "ing" has been frequently employed to refer to the ingestion pathway [50,86,88,89,111,112], while other terms include "oral" [9,47,93], "uptake" [49], "ingestion" [58,73,113], "ingest" [19,70,80], and "soil ingestion" [91]. The most typical inhalation term is "inh" [8,46,51,68], but other terms such as "inhale" [70,74,80] and "inhalation" [22,49] are additionally used.…”

“…It is used only in the equation for inhalation, and the most common abbreviation is InhR [18,51,105], but the following are also used: IR inh [35,93], IR 2 [100], IR i [36,109], R inh [52,97], R inhal [67], IRa [112], and IR air [88,120]. The values for children ranged between 7.3 and 16.57, where the most often mentioned were 7.5 [47,51], 7.63 [68,113], 7.6 [39,107], and only occasionally 7.3 [38], 8.1 [112], 9.3 [87], 10 [73], 7.65 [100], and 16.57 [118]. For adults, that figure was slightly higher, and values ranged from 12.8 to 20; the most often used was the value 20 [13,18,98].…”

“…On the other hand, even essential HMs can be highly toxic and lead to serious health problems when they enter the human body in huge concentrations [44][45][46]. HMs can lead to damage of various organs [5], as well as the occurrence of cancer, because the increased risk of developing this disease is correlated with long-term exposure to HMs [47]. When HMs reach the cells, they affect their redox potential and, thus, interfere with the reactions taking place in the cells [45].…”

Assessment of Heavy Metal Contamination and Ecological Risk in Soil within the Zheng–Bian–Luo Urban Agglomeration

“…Although China's exploration into heavy metals in urban soil commenced relatively recently, contemporary scholars have diligently investigated the content, distribution, and sources of soil heavy metal pollution in numerous large-and medium-sized cities, including Haikou, Beijing, Nanjing, and Shanghai [16][17][18][19][20][21][22][23]. The single factor index method was employed to assess the heavy metal pollution of the soil near the river, revealing severe pollution in the area, particularly from Cd [24]. An investigation into eight heavy metals within Beijing's urban green spaces revealed that Cd, Cu, Zn, and Ni are markedly influenced by anthropogenic activities.…”