Biochar as a Soil Amendment: Reduction in Mercury Transport from Hydraulic Mine Debris

Mercury mining and its use in gold mine operations left a legacy of contamination in northern California. Contaminated sediments and water continue to affect local and downstream ecosystems. To assess the efficacy of biochar-amended soils on decreasing Hg transport, biochar was used to amend rock and sediment columns and mesocosms to decrease suspended sediment and associated mercury (Hg) in storm water runoff from Sierra Nevada hydraulic mines. Mercury-contaminated storm water runoff and hydraulic mine debris were collected from two hydraulic mine sites in the Yuba River, California watershed. Mercury concentrations and turbidity were analyzed from storm water samples and hydraulic mine debris in three simulated storm runoff experiments using decomposed granite columns, sediment columns, and sediment mesocosms amended at 0%, 2%, or 5% biochar by weight. Columns containing hydraulic mine debris and mixed with 5% biochar had a significant (p < 0.05) reduction in filter-passed mercury (FHg) in the outflow as compared to control columns. To simulate saturated hydraulic mine debris runoff, mesocosms were filled with mine sediment and saturated with deionized water to generate runoff. Five percent biochar in mesocosm trays decreased FHg significantly (p < 0.001), but, because of the angle of the tray, sediment also moved out of the trays. Biochar was effective at reducing FHg from hydraulic mine discharge. Biochar in laboratory columns with decomposed granite or mine sediments was more effective at removing Hg than mesocosms.

An Integrated Investigation of Atmospheric Gaseous Elemental Mercury Transport and Dispersion Around a Chlor-Alkali Plant in the Ossola Valley (Italian Central Alps)

We present the first assessment of atmospheric pollution by mercury (Hg) in an industrialized area located in the Ossola Valley (Italian Central Alps), in close proximity to the Toce River. The study area suffers from a level of Hg contamination due to a Hg cell chlor-alkali plant operating from 1915 to the end of 2017. We measured gaseous elemental Hg (GEM) levels by means of a portable Hg analyzer during car surveys between autumn 2018 and summer 2020. Moreover, we assessed the long-term dispersion pattern of atmospheric Hg by analyzing the total Hg concentration in samples of lichens collected in the Ossola Valley. High values of GEM concentrations (1112 ng m−3) up to three orders of magnitude higher than the typical terrestrial background concentration in the northern hemisphere were measured in the proximity of the chlor-alkali plant. Hg concentrations in lichens ranged from 142 ng g−1 at sampling sites located north of the chlor-alkali plant to 624 ng g−1 in lichens collected south of the chlor-alkali plant. A north-south gradient of Hg accumulation in lichens along the Ossola Valley channel was observed, highlighting that the area located south of the chlor-alkali plant is more exposed to the dispersion of Hg emitted into the atmosphere from the industrial site. Long-term studies on Hg emission and dispersion in the Ossola Valley are needed to better assess potential impact on ecosystems and human health.

Development of a numerical model for predicting the volatilization flux from unsaturated soil

&lt;p&gt;In recent years, exposure to volatile chemical substances (VCSs) from contaminated soil has become a serious problem so it has become increasingly important to study the transport phenomena of VCSs. In this study we focused on the transport phenomena of VCSs at the boundary layer between the soil surface and the atmosphere, and defined it as volatilization flux, which express the amount of volatilized substances per unit volume per unit time. In order to estimate the phenomena of mercury transport in unsaturated soil and mercury released from soil to the atmosphere, it is necessary to consider in detail the spatiotemporal fluctuations of factors that affect the volatilization of mercury and the physical transport phenomena in soil.&lt;/p&gt;&lt;p&gt;The present study developed a model for predicting the volatilization flux from the unsaturated soil contaminated by VCSs. The model considers a series of phenomena under the unsaturated condition such as gas-liquid two-phase flow consisting of convection and diffusion. The effects of various transport phenomena on the surface soil on changes in the magnitude of this flux due to variations in meteorological factors such as temperature and soil moisture content were quantitatively evaluated. This developed prediction model can be utilized to estimate dynamic variations in the flux under real-environmental conditions.&lt;/p&gt;

In vitro function and in situ localization of Multidrug Resistance-associated Protein (MRP)1 (ABCC1) suggest a protective role against methyl mercury-induced oxidative stress in the human placenta

Methyl mercury (MeHg) is an organic highly toxic compound that is transported efficiently via the human placenta. Our previous data suggest that MeHg is taken up into placental cells by amino acid transporters while mercury export from placental cells mainly involves ATP binding cassette (ABC) transporters. We hypothesized that the ABC transporter multidrug resistance-associated protein (MRP)1 (ABCC1) plays an essential role in mercury export from the human placenta. Transwell transport studies with MRP1-overexpressing Madin-Darby Canine Kidney (MDCK)II cells confirmed the function of MRP1 in polarized mercury efflux. Consistent with this, siRNA-mediated MRP1 gene knockdown in the human placental cell line HTR-8/SVneo resulted in intracellular mercury accumulation, which was associated with reduced cell viability, accompanied by increased cytotoxicity, apoptosis, and oxidative stress as determined via the glutathione (GSH) status. In addition, the many sources claiming different localization of MRP1 in the placenta required a re-evaluation of its localization in placental tissue sections by immunofluorescence microscopy using an MRP1-specific antibody that was validated in-house. Taken together, our results show that (1) MRP1 preferentially mediates apical-to-basolateral mercury transport in epithelial cells, (2) MRP1 regulates the GSH status of placental cells, (3) MRP1 function has a decisive influence on the viability of placental cells exposed to low MeHg concentrations, and (4) the in situ localization of MRP1 corresponds to mercury transport from maternal circulation to the placenta and fetus. We conclude that MRP1 protects placental cells from MeHg-induced oxidative stress by exporting the toxic metal and by maintaining the placental cells' GSH status in equilibrium.

A scoping review of sources of mercury and its health effects among Pakistan’s most vulnerable population

Mercury and methyl mercury are poisonous to human body. In the recent times, exposure to mercury has been anthropogenic in nature. Within the past several decades, many incidences of mercury poisoning have been documented in several countries including Pakistan. Mercury has been ingested where it has been used to preserve crops, through the point and non-point source discharge into the surface water, and consequently entering the food chain. We conducted this scoping review of mercury and its health effects in Pakistan in order to raise the flag to a silent ongoing Minamata disease in the country. We conducted a systematic search of the available literature in Google Scholar, PubMed, and grey literature of unpublished theses and reports of various universities across the country. We found that in the northern Pakistan, suspended sediments were the major pathway of the riverine mercury transport. Sediments of Hunza and Gilgit River were found high in mercury concentrations. Gold mining leads to an increase in mercury concentration in soil and river waters flowing in this region. High concentrations up to 108 ng/L were found in Shimsal River. It is suspected that that high level of mercury transport may be leading to accumulation of mercury in major water bodies and lakes downstream. Occupational exposure to mercury and other heavy metals is common in an unregulated private sector of the country. Goldsmiths burn the amalgamated gold without personal protective measures. Direct exposure to the fumes of mercury leads to respiratory, dermatological, systemic and neurological ailments specific to mercury poisoning. We found good evidence of bioaccumulation of mercury in fish and fish products in Pakistan. The untreated waste water discharge is responsible to not only afflicted the fish but also the birds which feed on this fish. Further, the same untreated waste water from factories and agriculture runoffs affect vegetables grown in it. Studies looking at the biomarkers for mercury in humans have shown increased and even toxic levels of mercury among the most vulnerable populations of the country. Other sources of mercury exposure included mercury in traditional medicines and cigarette products. Though no evidence was found for its presence in drinking water, its existence in the food chain and occupational exposure pose great threat to the humans as well as animals.