Mexico in the International Reptile Skin Trade: a Case Study

This paper examines the role of Mexico as importer, manufacturer, producer and distributor centre of reptile skins from non-native and native species, through a combination of documentary research and survey methods. A number of key findings were derived from this study. Although Mexico has adopted the “System for the Conservation, Management and Sustainable Use of Wildlife” (SUMA), the country still relies on reptile skins from non-native species. In contrast, the smaller numbers of skins used from native species mainly derive from captive breeding schemes that although biologically sustainable, provide no incentive for habitat conservation. Sustainable use of reptile skins from native species could positively encourage conservation in Mexico. However, as a megadiverse country with potential to produce wildlife, Mexico will have to implement an appropriate regulatory framework to support local communities to promote the sustainable use of native species.     

Applying a Watershed-Level,Risk-Based Approach to Addressing Legacy Mercury Contamination in the South River,Virginia: Planning and Problem Formulation

In 2001, the DuPont Company and various Virginia regulatory agencies (Virginia) established the South River Science Team (SRST) as a multi-stakeholder and collaborative program to address legacy Hg contamination of the South River, Virginia. Specifically, the SRST began to apply a watershed-level risk-based assessment process to evaluate the potential impact of a former DuPont facility adjacent to the South River. Mercury had been found in facility soils in 1976 spawning numerous chemical and biological studies. However, prior to 1999, with the exception of a structured, long-term fish monitoring plan developed by Virginia, these studies were conducted by diverse, independent organizations resulting in limited scientific oversight and implementation, or interaction with the public. This article focuses on some key findings (e.g., defining/refining the issues, setting up the team, the role of the different stakeholders in making the process work) from the problem formulation and planning phase of this multi-stakeholder effort. The SRST effort draws heavily on the concepts of problem formulation (PF) and planning (as described by the U.S. Environmental Protection Agency) to guide the overall risk-based approach. PF is one of the most important steps in the process and, if done correctly can lead to a well-conceived and implemented assessment.     

Mercury (micro)biogeochemistry in polar environments

The contamination of polar regions with mercury that is transported as inorganic mercury from lower latitudes has resulted in the accumulation of methylmercury in the food chain of polar environments, risking the health of humans and wildlife. This problem is likely to be particularly severe in coastal marine environments where active cycling occurs. Little is currently known about how mercury is methylated in polar environments. Relating observations on mercury deposition and transport through polar regions to knowledge of the microbiology of cold environments and considering the principles of mercury transformations as have been elucidated in temperate aquatic environments, we propose that in polar regions (1) variable pathways for mercury methylation may exist, (2) mercury bioavailability to microbial transformations may be enhanced, and (3) microbial niches within sea ice are sites where active microorganisms are localized in proximity to high concentrations of mercury. Thus, microbial transformations, and consequently mercury biogeochemistry, in the Arctic and Antarctic are both unique and common to these processes in lower latitudes, and understanding their dynamics is needed for the management of mercury-contaminated polar environments.     

Mercury concentration in natural objects of west Siberia

In this paper we compare the accumulating capacities of various ecological indicators of mercury pollution in marsh and urban ecosystems and report experimental data on concentration of mercury in atmospheric air, urban soils, peat, lichens, mosses, mushrooms, and berries.     

Impacts of Reservoir Creation on the Biogeochemical Cycling of Methyl Mercury and Total Mercury in Boreal Upland Forests

The FLooded Upland Dynamics Experiment (FLUDEX) at the Experimental Lakes Area (ELA) in northwest Ontario was designed to test the hypothesis that methylmercury (MeHg) production in reservoirs is related to the amount, and subsequent decomposition, of flooded organic matter. Three upland forest sites that varied in the amounts of organic carbon stored in vegetation and soils (Low C, 30,870 kg C ha⁻¹; Medium C, 34,930 kg C ha⁻¹; and High C, 45,860 kg C ha⁻¹) were flooded annually from May to September with low-organic carbon, low-MeHg water pumped from a nearby lake. Within five weeks of flooding, MeHg concentrations in the reservoir outflows exceeded those in reservoir inflows and remained elevated for the duration of the experiment, peaking at 1.60 ng L⁻¹ in the Medium C reservoir. We estimated the net production of MeHg in each reservoir by calculating annual changes in pools of MeHg stored in flooded soils, periphyton, zooplankton, and fish. Overall, there was an initial pulse of MeHg production (range = 120–1590 ng m⁻² day⁻¹) in all FLUDEX reservoirs that lasted for 2 years, after which time net demethylation (range = 360–1230 ng MeHg degraded m⁻² day⁻¹) began to reduce the pools of MeHg in the reservoirs, but not back to levels found prior to flooding. Rates of MeHg production were generally related to the total amount of organic carbon flooded to create the reservoirs. Large increases in MeHg stores in soils compared to those in water and biota indicate that flooded soils were the main sites of MeHg production. This study should assist hydroelectric utilities and government agencies in making informed decisions about selecting sites for future reservoir development to reduce MeHg contamination of the reservoir fisheries.     

Bioaccessibility of Mercury in Soils

The initial risk assessment for the East Fork Poplar Creek (EFPC) floodplain in Oak Ridge, Tennessee, a superfund site heavily contaminated with mercury, was based on a reference dose for mercuric chloride. Mercuric chloride, however, is a soluble mercury compound not expected to be present in the floodplain, which is frequently saturated with water. Previous investigations had suggested mercury in the EFPC floodplain was less soluble and therefore potentially less bioavailable than mercuric chloride, possibly making the results of the risk assessment unduly conservative. A bioaccessibility study, designed to measure the amount of mercury available for absorption in a child's digestive tract (the most critical risk pathway endpoint), was performed on 20 soils from the EFPC floodplain. The average bioac-cessible mercury for the 20 soils was 5.3%, compared with 100% of the mercuric chloride subjected to the same conditions. The alteration of the procedure to more closely mimic conditions in the digestive tract did not significantly change the results. Therefore, the use of a reference dose for mercuric chloride at EFPC, and potentially at other mercury-contaminated sites, without incorporating a corresponding bioavailability adjustment factor may overestimate the risk posed by the site.     

Isolation and Characterization of Mercury Resistant Bacillus sp. from Soils with an Extensive History as Substrates for Mercury Extraction in Mexico

Metal phytoextraction assisted by bacteria plays an important role in bioremediation systems. In this work, mercury-resistant bacterial strains were isolated from soils with high levels of mercury (San Joaquin, Queretaro State, Mexico) and identified as Bacillus sp. based on the 16S rDNA gene sequence analysis. The bacterial strains were found to exhibit different multiple mercury-resistance and carbon source utilization characteristics. The mercury reduction ability was tested through a volatilization assay. The bacterial isolates were also evaluated for their ability to promote growth and mercury uptake in tomato plants. In a roll towel assay, the maximum vigor index of tomato plants was obtained with the inoculation of Bacillus sp. A2, A12, B11, B15 and C1, while in a pot assay, the maximum vigor index was obtained with the inoculation of Bacillus sp. A6, A7 and B20, compared with un-inoculated controls in the presence of HgCl₂. Maximum Hg accumulation in the roots and shoots of tomato plants was obtained only with Bacillus sp. A7 in the roll towel assay, whereas in the pot assay, maximum accumulation was obtained with Bacillus sp. A12 compared with un-inoculated controls. Our results show that mercury accumulation in tissue is enhanced by these plant growth promoting bacterial strains, which recommends their possible use as microbe-assisted phytoremediation systems in mercury-polluted soils.     

Mercury budget of an upland-peatland watershed

Inputs, outputs, and pool sizes oftotal mercury (Hg) were measured in a forested 10 hawatershed consisting of a 7 ha hardwood-dominatedupland surrounding a 3 ha conifer-dominatedpeatland. Hydrologic inputs via throughfall andstemflow, 13±0.4 g m^–2 yr^–1over the entire watershed, were about doubleprecipitation inputs in the open and weresignificantly higher in the peatland than in theupland (19.6 vs. 9.8 g m^–2 yr^–1). Inputs of Hg via litterfall were 12.3±0.7g m^–2 yr^–1, not different in thepeatland and upland (11.7 vs. 12.5 g m^–2yr^–1). Hydrologic outputs via streamflow were2.8±0.3 g m^–2 yr^–1 and thecontribution from the peatland was higher despiteits smaller area. The sum of Hg inputs were lessthan that in the overstory trees, 33±3 gm^–2 above-ground, and much less than eitherthat in the upland soil, 5250±520 gm^–2, or in the peat, 3900±100 gm^–2 in the upper 50 cm. The annual flux of Hgmeasured in streamflow and the calculated annualaccumulation in the peatland are consistent withvalues reported by others. A sink for Hg of about20 g m^–2 yr^–1 apparently exists inthe upland, and could be due to either or bothstorage in the soil or volatilization.     

Mercury biotransformations and their potential for remediation of mercury contamination

Bacterially mediated ionic mercury reduction to volatile Hg⁰ was shown to play an important role in the geochemical cycling of mercury in a contaminated freshwater pond. This process, and the degradation of methylmercury, could be stimulated to reduce the concentration of methylmercury that is available for accumulation by biota. A study testing the utility of this approach is described.Abbreviations Hg^R inorganic mercury resistance - Org-Hg organomercury - Org-Hg^R organomercury resistance - SRB sulfate reducing bacteria - Methyl-B12 methylcobalamine     

汞对水稻幼苗部分生理生化指标的影响

目的:探究Hg2 对水稻幼苗生长的影响。方法:通过水培实验,研究分析了水稻幼苗在不同浓度Hg2 (0~2.0mmol/L)胁迫下株高、鲜重、叶绿素含量和过氧化物酶(POD)活性的变化。结果:表明0.05mmol/L的Hg2 短时间内对水稻幼苗生长有一定的促进作用,高于0.05mmol/L的处理,随着Hg2 浓度的增加,植株生长明显受到限制。当Hg2 浓度≤0.1mmol/L时,POD活性先上升后下降,而Hg2 浓度≥0.5mmol/L时则持续降低。结论:Hg2 对水稻幼苗生长抑制程度与处理浓度和处理时间成正相关。     

The Influence of Long-term Mercury Exposure on Selenium Availability in Tissues: An Evaluation of Data

The precise mechanisms of mercury accumulation and retention are still unclear. Generally, the association of mercury with selenium is used to explain these phenomena. It seems that the presence of coaccumulated endogenous Se can protect cells from the harmful effects of Hg. However, as speculated by some authors, this binding of Se to Hg can also result in a relative deficiency of biologically available Se needed for selenoenzyme syntheses. Deriving from the assumption that Hg deposited in tissues is bound to Se in a 1:1 ratio, the quantity of non-Hg bound Se could be calculated by the difference between the molar contents of the two elements (Se_mol–Hg_mol). In this study we applied such an approach to the data from our previous investigation, where Hg and Se concentrations were determined in autopsy samples of mercury exposed retired Idrija mercury mine workers, Idrija residents living in a Hg contaminated environment and a control group with no known Hg exposure from the environment. Based on these data we tried to estimate the influence of Hg exposure on the physiologically available selenium content in selected tissues, particularly endocrine glands and brain tissues. Comparing the calculated values of (Se_mol– Hg_mol) it was found that for Idrija residents the values were similar to those of the control group and as expected, diminished values were found in some mercury-loaded organs of retired Idrija miners. It could be speculated that in Idrija residents Hg sequestration of selenium is sufficiently compensated by increased Se levels, but that particularly in active miners and in some organs of retired miners, the activity and/or synthesis of selenoenzymes could be disturbed. Part of the study was presented at the 7th International Conference on Mercury as a Global Pollutant, June 27–July 2, 2004 Ljubljana, Slovenia (Falnoga et al. 2000)     

大米草对有机汞的耐性、吸收及转化

大米草对营养液中氯化甲基汞(MeHgCl)毒性的临界浓度为15 uml/L,是烟草的3倍.氯化甲基汞处理后,植株体内有机汞总量在增加,而营养液中有机汞总量在减少,无机汞总量则明显增加.这些结果表明,大米草可以吸收有机汞,将有机汞部分地转化为无机汞,并且无机汞较多地积累在植株的地下部,同时有一部分通过扩散或分泌进入营养液中.大米草对汞的积累作用和把有机汞转化为无机汞的转化作用在环境污染的植物修复方面有重要的利用价值.     

Mercury deposits in neurons of the trigeminal ganglia after insertion of dental amalgam in rats

An amalgam filling was inserted into the first upper molar of 12 rats and the animals were killed after 3–9 months. Tissue sections from the trigeminal ganglia and the brain stem were then investigated with a sensitive histochemical technique to trace mercury deposits. Within the trigeminal ganglia, nerve cells with mercury deposits were observed in seven out of 12 rats, whereas no mercury was detected in sections from the brain stem. The mechanism responsible for the accumulation of mercury in neurons of the trigeminal ganglia is discussed.     

Mercury pollution in Tokuyama Bay

The sediments and aquatic life of Tokuyama Bay, Japan, have been polluted by mercury effluent from chloro-alkali plants. In total, about 380 tons mercury were released from these plants and 6.64 tons of mercury were discharged into the bay in waste waters between 1952 and 1975, when mercury cells were employed. A number of surveys to study mercury pollution and the effectiveness of control measures in this area were conducted in the early 1970's by our laboroatory and other agencies. Analysis of human hair from Tokuyama Bay residents contained less mercury than those in Minamata and Agano districts, Japan, where serious mercury poisoning had occurred, but were contaminated with more mercury than those in other unpolluted areas. No occurrence of Minamata disease has been reported in the Tokuyama district.Reclamation of mercury contaminated sediments began in 1975; dredging of the bay continued until 1977. Since then, the levels of mercury contamination in sediments and aquatic life have gradually decreased. Today there are no problems with respect to mercury pollution.In this paper, we describe and discuss mercury pollution in Tokuyama Bay with regard to the following aspects of research and pollution control: the history of mercury pollution; mercury discharge and its accumulation in sediments; behaviour of mercury in sediments; mercury contamination of fish; mercury and the health of local residents; and remedial actions.     

Sulfate-reducing Bacteria and Mercury Methylation in the Water Column of the Lake 658 of the Experimental Lake Area

Sulfate-reducing bacteria (SRB) appear to be the main mediators of mercury methylation in sediments, which are deemed to be major sites of methylmercury (MMHg) production. However, recent studies have also found significant MMHg formation in the water column of lakes across North America. To investigate the potential involvement of SRB in mercury methylation in the water column of a stratified oligotrophic lake, two of the main families of SRB (Desulfobacteraceae and Desulfovibrionaceae) were quantified by Real-Time Polymerase Chain Reaction of the 16S rRNA gene. MMHg production was measured applying a stable isotope technique using ¹⁹⁸HgCl. Methylation assays were conducted at different water depths and under stimulation with lactate, acetate or propionate and inhibition with molybdate. Desulfobacteraceae and Desulfovibrionaceae16S rRNA gene copies in control samples accounted for 0.05% to 33% and <0.01% to 1.12% of the total bacterial 16S rRNA, respectively. MMHg formation was as high as 0.3 ng L^?1 day^?1 and largest in lactate amended samples. Strain isolation was only achieved in lactate amended media with all isolated strains being SRB belonging to the Desulfovibrio genus according to their 16S rRNA gene sequence. Isolated strains methylated between 0.06 and 0.2% of ¹⁹⁸HgCl per day. Acetate and propionate did not stimulate mercury methylation as much as lactate. Two strains were identified as Desulfovibrio sp. 12ML1 (FJ865472) and Desulfovibrio sp. 12ML3 (FJ865473), based on partial sequences of their 16S rRNA and DSR gene. Methylation assays and bacteria characterization suggest that Desulfovibrionaceae is an important mercury methylators in Lake 658. Supplemental materials are available for this article. Go to the publisher's online edition of Geomicrobiology Journal to view the free supplemental file.     

Mercury Toxicity and the Mitigating Role of Selenium

Mercury is a well-known environmental toxicant, particularly in its most common organic form, methylmercury. Consumption of fish and shellfish that contain methylmercury is a dominant source of mercury exposure in humans and piscivorous wildlife. Considerable efforts have focused on assessment of mercury and its attendant risks in the environment and food sources, including the studies reported in this issue. However, studies of mercury intoxication have frequently failed to consider the protective effects of the essential trace element, selenium. Mercury binds to selenium with extraordinarily high affinity, and high maternal exposures inhibit selenium-dependent enzyme activities in fetal brains. However, increased maternal dietary selenium intakes preserve these enzyme activities, thereby preventing the pathological effects that would otherwise arise in their absence. Recent evidence indicates that assessments of mercury exposure and tissue levels need to consider selenium intakes and tissue distributions in order to provide meaningful risk evaluations.     

桂林市汽车尾气汞污染

采集了桂林市郊4条公路剖面大气、土壤和蔬菜各56件样品,分析测定了其汞含量,以了解桂林市郊汽车尾气汞污染状况.结果表明,公路剖面汞含量均呈对称单峰型分布.汽车尾气汞污染扩散的影响范围约200 m.大气汞含量与蔬菜和土壤的汞污染具有明显的相关性.公路系统汽车尾气汞污染强度随公路路龄、车流量增大而增强.公路系统汞污染主要来源于汽车尾气汞污染,根源于燃油富含汞.公路剖面土壤48%样品汞含量超过了国家无公害蔬菜基地土壤汞含量标准.桂阳公路剖面蔬菜汞含量是国家无公害农产品质量标准(0.29+0.03 μg·g-1)的1.1～1.7倍.表明,桂林市公路系统剖面已受到一定程度的汞污染.     

水蓼对汞积累与分布的水培实验

通过水培实验,研究不同浓度的汞(0、0.5、1、10、20和50μg·L-1)对水蓼生长的影响及水蓼的耐受性表现。结果表明:在所处理的浓度范围内,水蓼生长与生理表现未受影响。水蓼根部具有最强的汞富集能力,富集系数高达531.5%。培养液中的汞浓度与水蓼茎、叶和根中汞的富集量呈显著正相关。在同一浓度时,随着培养时间的增长,水蓼体内汞含量不断增加。水蓼茎、叶和根亚细胞中的汞分布规律表现为:细胞壁>细胞器>细胞液,细胞壁对进入植物体内的汞有很强的束缚作用,限制其进入细胞质内部。     

A Methodology to Assess the Amounts of Pesticidal Mercury Used Historically in New Jersey

A methodology using existing, accessible public information is presented for the estimation of amounts of mercury that may have been applied to soils historically on agricultural land in the U.S. Estimations based on national agricultural consumption data reported by the Bureau of Mines can be apportioned further to the state and county level. For comparison, estimates using crop recommendations are presented, which can be considered to provide an upper-bound estimate of amounts potentially used on individual farms. In New Jersey, approximately 318,000?lb of mercury as an active ingredient could have been applied on approximately 150,000 acres of cropland and golf courses in the period 1921 to 1990. Based on crop recommendations, as much as 600,000 to over 1,000,000?lb of mercury could have been applied.