C.Y. Lan

Acidification of lead/zinc mine tailings and its effect on heavy metal mobility

The acid-forming potential of lead/zinc (Pb/Zn) mine tailings at Lechang City of Guangdong Province was studied using both net acid generation (NAG) and acid-base accounting (ABA) methods. The pyritic and total sulfur contents of the tailings were 12.6% and 18.7%, respectively. The mean acid neutralization capacity (ANC) was 63.5 kg H2SO4/t while three oxidized tailings samples had an ANC less than zero. The NAG and net acid production potential (NAPP) values were 220 and 326 kg H2SO4/t, and both the NAG and NAPP results indicated that the tailings had a high acid-forming potential. NAG was more accurate than NAPP in predicting acid-forming potential of the tailings due to uncompleted oxidization of pyritic sulfur. Analysis of samples from two profile tests indicated that acidification mainly occurred at the surface (0-20 cm) and had little effects at deep layer of the tailings. Total concentrations of Pb, Zn, Cu, and Cd were increased greatly with depth at the acidified tailings profile, while heavy metal concentrations at different depths of nonacidified tailings profile were similar. The results indicated that depletion of heavy metals at the acidified surface was due to acidification. The diethylenetetramine pentaacetic acid (DTPA)-extractable Pb, Zn, Cu, and Cd concentrations of acidified tailings surface (0-20 cm) were significantly higher than those of nonacidified tailings, which further revealed that acidification enhanced the mobility of heavy metals in the tailings.

Lime and pig manure as ameliorants for revegetating lead/zinc mine tailings : a greenhouse study

Abstract The Lechang lead/zinc mine is located at the north of Guangdong Province in southern China. The residual tailings from the extraction of lead/zinc ores were permanently stored in tailings ponds which required revegetation to reduce their impact on the environment. Therefore, a greenhouse study was conducted to evaluate the effects of lime (0.5, 1.0, 2.0 and 4.0 t ha−1) and pig manure (12.6, 25.2, 37.8, 50.3 and 75.5 t ha−1) amendment on the revegetation of the Pb Zn mine tailings using Agropyron elongatum (tall wheatgrass) and Trifolium repens (clover). The results showed that the applications of lime or pig manure increased pH, reduced electrical conductivity (EC) and DTPA-extractable concentrations of Zn, Pb and Cd in the tailings. Compared with tailings without amendment, application of lime alone (2 t ha−1) did not improve growth of either species. However, using lime with supplemental fertilizer (150 kg ha−1 of N) improved shoot growth of A. elongatum, especially at lime amendment rates of 0.5 and 4.0 t ha−1 + 150 kg ha−1 of N, but it did not improve root growth of either plant species. When compared with the tailings amended with lime (2 t ha−1) only, tailings receiving pig manure (25.2–50.3 t ha−1) and 2 t ha−1 of lime effectively improved shoot and root growth and reduced tailings toxicity to seedlings of T. repens, especially at 50.3 t ha−1 of pig manure. However, only tailings receiving 37.8 t ha−1 of pig manure and 2 t ha−1 of lime significantly increased shoot and root dry weight of A. elongatum. Plant tissue analysis showed that applications of lime and pig manure did not significantly reduce Zn, Pb and Cd uptake and accumulation in A. elongatum. However, higher pig manure amendment rates (> 25.2 t ha−1) significantly reduced Pb content in shoots of T. repens.

Trace Metal Contents (Al, Cu and Zn) of Tea: Tea and Soil from Two Tea Plantations, and Tea Products from Different Provinces of China

The present project aims to investigate the possible contamination of teas with the trace metals: Al, Cu and Zn. Tea bushes sampled from two tea plantations in the northern part of Guangdong Province accumulated higher concentrations of Cu and Zn in young leaves, and of Al in old leaves. The analysis of the three metals in tea produced in different provinces indicated higher Al levels in those obtained from Guangdong and Yunnan Provinces, which may be due to the lower soil pH in these areas. Green tea had the lowest Al concentration among the four types of tea studied, as only the bud and two young leaves are used, whereas older leaves are used for other types of tea (black, Oolong and Puerh tea). The transfer of Al, Cu and Zn from soil to different parts of tea bushes was low in general, except for Zn at Lechang tea plantation which next to a Pb/Zn mine, where a higher transfer was observed from young leaves to tea products, indicating possible metal contamination during tea processing. However, low concentrations of Cu and Zn (less than 0.07 mg Cu L-1 and 0.17 mg Zn L-1), and moderate amounts of Al (2.1-2.5 mg L-1) were obtained in the tea liquor (1% hot water extracts).

Constitutional tolerance to heavy metals of a fiber crop, ramie (Boehmeria nivea), and its potential usage.

It is observed that ramie (Boehmeria nivea), an economic fiber crop, can establish and colonize metal-contaminated sites in China. Metal tolerance and accumulation by ramie originating from 13 metal-contaminated and 4 clean sites in China were compared under field and hydroponic conditions. All selected populations and germplasms displayed good growth performance under diverse metal-contaminated habitats; while growth responses, metal accumulation and tolerance were similar among the 8 populations and 2 germplasms when exposed to solutions containing elevated As, Cd, Pb, or Zn in the laboratory. These revealed that ramie possesses a certain degree of constitutional metal tolerance. To our knowledge, this is the first report of constitutional metal tolerance possessed by a fiber crop. Ramie can be considered as a good candidate for both fiber production and phytoremediation of sites contaminated by multi-metals, as it accumulates relative low metal concentrations, but possesses both high biomass and high economic value.

Reclamation of Pb/Zn mine tailings at Shaoguan, Guangdong Province, People's Republic of China: The role of river sediment and domestic refuse

Abstract The Fankou Pb/Zn tailings pond was abandoned in 1978, resulting in a 20 ha tailings pile requiring stabilization. The major constraints in rehabilitation are heavy metal (Pb, Zn, Cu and Cd) toxicity and poor nutrient conditions. A greenhouse study was conducted to evaluate the ameliorating role of river sediment, domestic refuse and inorganic fertilizers in the revegetation of the tailings. River sediment and refuse were mixed with tailings at rates of 30%, 60% and 90% (w/w) respectively, and NPK fertilizer was also applied at four levels. Their effects on the growth of Stylo-santhes guianensis cv Graham were evaluated. River sediment and refuse amendments significantly increased dry matter yields but inorganic fertilizer had no effect. Tailings amended with 90% refuse, 30% and 60% river sediment produced higher yields. In general, plants grown on tailings amended with 30% river sediment accumulated the greatest amounts of Pb, Zn, Cu and Cd.

Effects of zinc (zinc sulfate) on Rhizobia-earleaf acacia (Acacia auriculaeformis) symbiotic association

Abstract This project was aimed at investigating the feasibility of using a legume woody plant Acacia auriculaeformis to reclaim Zn-contaminated areas. The effects of different concentrations of Zn, applied as zinc sulfate, on nodulation (%) and nitrogen fixation activity of the A. auriculaeformis symbiont Rhizobium strain (AA9108) and on growth of the host plant in solution culture conditions were studied. The EC10 and EC50 values (effective concentration to reduce the growth by 10% and 50%, respectively) for AA9108 were 373.6 mg l−1 and 638.9 mg l−1, respectively. Nodule formation was inhibited by 10% and 50% at Zn levels of 62.9 mg l−1 and 115.6 mg l−1, respectively. EC10 and EC50 values for N2-fixation activity were 4.7 mg l−1 and 38.6 mg l−1, respectively. Growth of host plant was the most sensitive (EC10 and EC50 values were 0.6 mg l−1 and 18.3 mg l−1, respectively). Screening Zn-tolerant varieties of the genus Acacia is therefore a prerequisite for using this genus in revegetation of Zn-contaminated areas.

Development of eight polymorphic microsatellite markers by FIASCO-based strategy for a arsenic-hyperaccumulator Chinese brake fern

Chinese Brake fern (Pteris vittata) is the first identified and well-known arsenic-hyperaccumulator. It is widely distributed in areas of temperate zone as diploid and of subtropics-tropics zone as tetraploid. Screening 60 individuals from Southern China, eight polymorphic microsatellite markers were developed for the first time by employing fast isolation by AFLP of sequences containing repeats protocol (FIASCO). The number of alleles for each marker ranged from two to seven and one to four bands per individual. Furthermore, five of the loci possess more than two alleles per individual. The results suggested these microsatellite markers provide a useful tool for studying the ongoing genetic variability of this specie as well as mating systems.

Revegetation of lead/zinc mine tailings at shaoguan, guandong province, China: phytotoxicity of the tailings

Abstract The Shaoguan lead/zinc mine is located in Guangdong Province, south of China. The residual tailing materials from the extraction of lead and zinc ores have been retained in a tailing pond since 1986 as a slurry. The operation ceased in 1978 and the tailings became arid in 1980 with a pH of 10. The pH of the tailings was further reduced to 7.8 in 1993 with a limited number of plant species and a sparse coverage. This article is an attempt to study the major constraints for the natural colonization of plants on the tailings, evaluated by the phytotoxicity. There are only 12 plant species thriving in the tailings, Neyrudia reyaudinana, Imperta cylindraca, Rhus chinensis, and Pteridium aquilium being the most common species, with a relatively higher coverage. The adverse edaphic factors seemed to govern plant establishment and colonization on the tailings. These included the high concentrations of heavy metals (Pb 34300, Zn 36500, Cu 251 and Cd 83 mg/kg, total concentrations), lack of organic matter and nitrogen. A pot trial was conducted by growing a grass species Stylosanthes guianensis cv Graham on tailings mixed with sand at the ratio of 0, 25, 50, 75 and 100% (w/w). There were evident chlorosis and stunting symptoms at 25% tailings. Plant growth was inhibited at 50% tailings upward. A subsequent toxicity test was conducted using seeds of Brassica chinensis growing in a series of 0.1 M HCl extracts of tailings (Tailings: HCl=1:5 w/v; and diluted 1-, 5-, 10-, and 20-fold), with adjustment of pH to 7. The effects of tailing extracts on root elongation of B. chinensis matched the results of the pot trial, which indicated the possibility of using the root elongation test as a fast screening method for assessing soil toxicity. A column leaching experiment was also conducted to investigate the effects of acid precipitation on the mobility of heavy metals (Pb, Zn, Cu, Cd). The results indicated that acidic precipitation gave rise to the release of a higher concentration of heavy metals, which might cause soil and groundwater contamination.