New insight into the response and transport of nitrate in karst groundwater to rainfall events.

Although numerous studies focused on nitrate source, transformation and transport of river water in karst area have been reported, it's still unclear in understanding nitrate main source and transformation in karst groundwater system and how nitrate transport from soil to water during rainfall events in karst critical zone. In order to explore the response and transport of nitrate in karst groundwater to rainfall events, different depths of well water before, during and after rainfall event were sampled, and hillslope runoff, surface runoff of different land-use types during rainfall event were sampled synchronously at a typical karst agricultural catchment in Southwest China. Results showed that fluctuations of EC, pH and DO in deep borehole well (W1) and artesian well (W2) were small, on the contrary, variations of EC and DO in shallow well (W3) were large during sampling period.

Determining rainwater chemistry to reveal alkaline rain trend in Southwest China: Evidence from a frequent-rainy karst area with extensive agricultural production.

Rainwater chemistry plays an important role in the earth-surficial ecosystem, but studies on rainwater chemical composition of karst agro-ecosystem are rare. To explore the rainwater alkalization and the provenance of components responsible for neutralization, two-years chemical monitoring of rainwater was carried out in a karst agricultural catchment in Southwest China. The main findings suggest that SO, NO, Ca, and NH are the principal ions.

[Experimental Research of Hg (II) Removal from Aqueous Solutions of HgCl2 with Nano-TiO2].

Mercury removal from aqueous solutions of HgCl2 was studied by indoor simulation experiments, and the effects of three different diameter of particles of Nano-TiO2 ( Nano-Titanium Dioxide) at different dosage, pH, adsorption time and the initial concentration of Hg2+ on the mercury adsorption from simulated wastewater were investigated. The single factor experiments showed that the optimal conditions were: 7.5 g x L(-1) of 5 nm TiO2 or 2.

[Effect of Low Molecular Weight Organic Acids on the Chemical Speciation and Activity of Mercury in the Soils of the Water-Level-Fluctuating Zone of the Three Gorges Reservoir].

To investigate the effect of low molecular weight organic acids ( LMWOA) on the ability of migration and the species of mercury in the soil of the Water-Level-Fluctuating Zone of the Three Gorges Reservoir, citric acid, tartaric acid and oxalic acid were dded into the soil to conduct simulation experiments. The results showed that the percentage of exchangeable mercury increased with the increase of the concentration of citric acid, but the value declined slightly as the concentration of tartaric acid and oxalic acid increased. While all three acids elevated the bioavailability of mercury, which increased with the increase of the concentration of acids.

[Effects of Citric Acid on Activation and Methylation of Mercury in the Soils of Water-Level-Fluctuating Zone of the Three Gorges.Reservoir].

To investigate effects of the main component of vegetation root exudates-citric acid on activation and methylation of mercury in the soil of water-level-fluctuating zone (WLFZ) of the Three Gorges Reservoir area, simulation experiments were conducted by extracting and cultivating soil with different concentrations of citric acid. The results showed that after adding citric acid, the total mercury content in leaching solution before reaching peak were higher than that of the control, and increased with the increase of citric acid concentrations. The maximum amount of mercury complexes increased initially and then reached plateaus with the percentage against the total mercury in soil of 1.

[Concentrations and deposition fluxes of different mercury species in precipitation in Jinyun Mountain, Chongqing].

Concentrations of mercury (Hg) species in precipitation were measured during the period from April 2013 to March 2014 in Jinyun Mountain, Chongqing, and corresponding deposition fluxes were also estimated. The result showed that the ranges of concentration of total mercury (THg) , dissolved mercury (DHg), particulate mercury (PHg), reactive mercury (RHg), total methyl mercury (MeHg), dissolved methyl mercury (DMeHg), particulate methyl mercury (PMeHg) were 7.47-120.

[Concentrations and deposition fluxes of heavy metals in precipitation in core urban areas, Chongqing].

Concentrations and deposition fluxes of heavy metals in the precipitation of core urban areas of Chongqing were investigated for one year from December 2011 to November 2012. Precipitation samples were collected with an automated precipitation sampler from three sampling sites. Concentrations of 13 heavy metals were analyzed using ICP-MS.