Application of Isotope Tracer Technique in Source Apportionment of Heavy Metal Pollution in Soil

The formation of heavy metal pollution in soil is closely related to human production and life. In order to effectively control heavy metal pollution and repair damaged soil,the pollution source should be known and judged first. Based on the preliminary analysis of major sources of soil heavy metal pollution in soil,combined with relevant literatures on heavy metal pollution source of soil or sediment at home and abroad in recent years,application progress of isotope tracer technique,especially lead isotope tracer technique,in the study of heavy metal pollution sources in soils and sediments were reviewed. The key points of future isotope tracer technology in the field of heavy metal pollution source apportionment were prospected.

Quantifying the ambient formaldehyde sources utilizing tracers

Formaldehyde（HCHO） is one of the most important intermediate products of atmospheric photochemical reactions in the troposphere, therefore understanding of HCHO sources is essential for effective ozone control measures. The objective of this work is to distinguish between primary and secondary sources of HCHO. Based on about one month of online measurements in winter in Ziyang,Sichuan, the multi-linear regression analysis of ambient concentrations of HCHO and possible tracers（acetonitrile, propane and peroxyacetyl nitrate） was performed. The results show that during winter in Ziyang, biomass burning contributed an average of 53.2% to ambient HCHO levels, while secondary processes contributed about 30.1%, and vehicular sources accounted for 7.1%.

Stable isotope tracers identify sources and transformations of mercury in rice (Oryza sativa L.) growing in a mercury mining area

Methylmercury (MeHg) contaminated rice is a global issue, particularly in mercury-polluted areas, posing a potential threat to human health. The sources and transformations of mercury (Hg) species in rice are critical points that are not yet fully understood. In this study, field experimental pots together with a stable Hg isotope tracing technique were used to provide direct evidence of the sources and transformations of Hg species in rice plants. Enriched inorganic Hg (IHg) isotope (200Hg(NO3)2) was spiked into paddy soils, and the concentrations of inorganic Hg tracer (I200Hg), MeHg tracer (Me200Hg), and ambient Hg species (IHg and MeHg) were measured in the tissues of rice plants and their corresponding soil samples during the rice growing season. Here, we show that, in addition to the atmosphere, the soil is an important source of IHg to rice grains and was previously largely underestimated. We also show that MeHg is formed in paddy soil via microbial IHg methylation, absorbed through the rice root, translocated from the root to above-ground parts, and finally accumulated in rice grains. Although in vivo methylation of IHg in rice plants is unlikely to occur during the rice growing season, we observed in vivo demethylation of MeHg in the above-ground parts of rice plants, possibly via photolytic demethylation. Promoting in vivo demethylation of MeHg may be an effective approach to mitigate MeHg accumulation in rice grains.