Pollution characteristics and health risk assessment of metals in farmland soil around the largest realgar mining area in Asia

Background Heavy metal emissions from mining and smelting areas are a global problem, and health risks associated with heavy metal contamination of soils are of great concern. The long-term mining of the largest realgar mine in Asia has caused severe arsenic and other metal pollution to the surrounding rivers and soils. Objective To understand the levels of metal contamination and health risks in agricultural soils of villages surrounding the largest realgar mine in Asia, and to lay a good foundation for further necessary pollution control actions and decisions. Methods A field survey was conducted to collect soil samples according to the Technical rules for monitoring of environmental quality of farmland soil (NY/T 395-2012), and then inductively coupled plasma mass spectrometry was used to determine the contents of 28 heavy metals cadmium (Cd), arsenic (As), lead (Pb), mercury (Hg), chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), beryllium (Be), selenium (Se), cobalt (Co), antimony (Sb), molybdenum (Mo), vanadium (V), barium (Ba), thallium (Tl), boron (B) , bismuth (Bi), lithium (Li), manganese (Mn), strontium (Sr), calcium (Ca), rubidium (Rb), iron (Fe), magnesium (Mg), aluminum (Al), kalium (K), and titanium (Ti). Geoaccumulation index, single factor pollution index, and Nemerow comprehensive index were used to evaluate the degree and characteristics of single metal pollution and combined pollution in soil, respectively. A health risk assessment model was used to evaluate the risks of metals in soil to human health. Results The results of geoaccumulation index calculation revealed that 22 heavy metals were enriched in the soil, and the indexes of target heavy metals from high to low were Cd > Se > Pb >Hg > As > Co> Ni > Cu > Zn > Bi > Sb > Mo > Be> Cr > Ba >V > Li > Sr> Mn> Rb > Ca> Tl . The single factor pollution indexes of 17 heavy metals from high to low were Be > Cd > B > Mo > V > As > Ni > Cu > Pb > Zn > Co > Se > Tl > Ba > Cr > Hg > Sb. The Nemerow comprehensive index indicated all sampling points were graded as severe pollution. The mean of total non-carcinogenic health risk values and the mean of carcinogenic health risk values for the target heavy metals in the area were higher than the threshold (1) and the maximum acceptable risk (1.0×10–4), respectively. The total carcinogenic health risks for adults and children reached 1.1×10–3 and 1.67×10–3, respectively. The mean non-carcinogenic health risk values of As, Co, Cr, and Pb pollution w