1,721,013 research outputs found
A greenhouse trial to investigate the ameliorative properties of biosolids and plants on physicochemical conditions of iron ore tailings: implications for an iron ore mine site remediation
No full textAn iron ore mine site in Swaziland is currently (2015) in a derelict state as a consequence of past (1964–1988) and present (2011 – current) iron ore mining operations. In order to control problems associated with mine wastes, the Swaziland Water Services Corporation (SWSC) recently (2013) proposed the application of biosolids in sites degraded by mining operations. It is thought that this practice could generally improve soil conditions and enhance plant reestablishment. More importantly, the SWSC foresees this as a potential solution to the biosolids disposal problems.
In order to investigate the effects of biosolids and plants in soil physicochemical conditions of iron mine soils, we conducted two plant growth trials. Trial 1 consisted of tailings that received biosolids and topsoil (TUSB mix) while in trial 2, tailings received biosolids only (TB mix). In the two trials, the application rates of 0 (control), 10, 25, 50, 75 and 100 t ha−1 were used. After 30 days of equilibration, 25 seeds of Cynodon dactylon were sown in each pot and thinned to 10 plants after 4 weeks. Plants were watered twice weekly and remained under greenhouse conditions for 12 weeks, subsequent to which soils were subjected to chemical analysis.
According to the results obtained, there were significant improvements in soil parameters related to fertility such as organic matter (OM), water holding capacity (WHC), cation exchange capacity (CEC), ammonium (NH4+)(NH4+), magnesium (Mg2+), calcium (Ca2+) and phosphorus (PO4−PO4−). With regard to heavy metals, biosolids led to significant increases in soil total concentrations of Cu, Zn, Cd, Hg and Pb. The higher concentrations of Zn and Cu in treated tailings compared to undisturbed adjacent soils are a cause for concern because in the field, this might work against the broader objectives of mine soil remediation, which include the recolonization of reclaimed sites by soil-dwelling organisms.
Therefore, while biosolids contain important nutrients that may greatly improve physicochemical conditions and enhance vegetation reestablishment in mined soils, the threat of the build-up of higher levels of trace elements in treated tailings compared to surrounding adjacent soils must not be underestimate
Aflatoxins in the soil ecosystem: an overview of its occurrence, fate, effects and future perspectives
No full textAflatoxins are secondary metabolites produced by specific strains of fungi, especially Aspergillus spp. These natural toxins are mainly found in soil, decaying vegetation and food storage systems and are particularly abundant during drought stress. Aflatoxin contamination is one of the most important threats to food safety and human health due to its toxic, mutagenic and carcinogenic properties. Therefore, most research focuses on post-harvest contamination of aflatoxins in feed and food commodities but very limited information is available about aflatoxin contamination and its toxicological consequences in the soil ecosystem. Current regulations provide minimal options for the disposal of aflatoxin-contaminated crops, amongst which is the incorporation of residues into the soil for natural degradation. This form of mycotoxin loading into the soil could potentially change its physicochemical characteristics and biotic parameters. Recent studies suggest that as climate conditions change, the occurrence and geographical distribution of aflatoxins might increase, posing significant health risks to the soil ecosystem, food crop production and human health. This review will focus on studies that look at the environmental and toxicological consequences of aflatoxin contamination with the aim of clarifying the risk that aflatoxin contamination poses to soil ecosystems. Many aspects of aflatoxin occurrence, degradation and the effects of its transformation products in the soil environment are still unknown and remain an important area of research for soil health and productivity. A climatic approach, in terms of changes in soil moisture and air temperature, is important for future risk assessments of aflatoxin contaminatio
The enchytraeid reproduction test (ERT): a potentially quick and affordable tool for the assessment of metal contaminated soils in emerging economies
No full textThe enchytraeid reproduction test (ERT) was
used to assess the ecotoxicity of selected mine tailings and
agricultural soils from South Africa. The mine tailings had
higher cumulative metal concentrations than agricultural
soils. The most contaminated mine tailings significantly
reduced the survival of the oligochaete Enchytraeus doerjesi
whose reproduction was suppressed in all mine waste
substrates. Because it reliably singled out the most contaminated
substrate and was found easy to perform, we
suggest that the ERT could be a quick and affordable tool
for assigning intervention values for soil remediation in
emerging economies such as South Africa.http://link.springer.com/journal/12
Utilizing an Earthworm Bioassay (Eisenia andrei) to Assess a South African Soil Screening Value with Regards to Effects from a Copper Manufacturing Industry
No full textMetal contamination of soil due to industrialization has become an increasingly important problem in South Africa. This study aimed to investigate the potential impact of a copper (CuSO4·5H2O) production company on the soil environment. Bioassays using Eisenia andrei were performed to assess changes in biomass, reproduction and a biomarker, neutral red retention time, over a 28 day period. Earthworms exposed to soils from the Cu production site differed significantly (p < 0.05) from those exposed to soils 500 m and 5 km away in terms of the measured endpoints. These findings are consistent with the results from the chemical analysis which showed an elevated soil Cu content for both sites closest to the chemical production company compared to the reference site. The results confirm the importance and predictive value of using bioassays in conjunction with chemical analysis during soil quality assessments
The effects of different gold mine tailings on growth, reproduction and avoidance-behaviour of earthworms
No full textThe mining industry plays a key role in the economic development of South Africa as one of the largest exporters of valuable resources, such as gold, platinum group metals and other metals and minerals. Unfortunately, mining produces large volumes of solid waste in the form of tailing disposal facilities (TDFs), which contain a variety of metals that are hazardous to the soil environment. The aim of this study was to use earthworm bioassays and avoidance-behaviour tests to assess the effects of gold mine tailings on soil organisms. Six random soil samples were taken from four different sites on a gold mine viz. two different TDFs and two grassy pasture sites. Earthworms (Eisenia andrei) were exposed for a period of 28 days to the soils from these different sites. Soil from the TDFs was also diluted to 25%, 50%, 75% and 100%, respectively. Soil chemical analysis showed that the TDFs had the lowest pH levels and that only Cr concentrations were higher than proposed benchmarks in two of the sites. Earthworms exposed to the TDF material showed significantly lower earthworm biomass, allied with a very low cocoon production. The avoidance-behaviour test showed similar results, where earthworms generally preferred natural and control soils over the TDF material. It can be concluded, that even though the gold mine was inactive for a long period of time, it still remains a highly contaminated are
Soil mesofauna as bioindicators to assess environmental disturbance at a platinum mine in South Africa
No full textSouth Africa is rich in mineral resources and is one of the leading raw material exporters in the world. Mining is essential for economic development, but also has detrimental environmental consequences in the form of chemical waste products which are being dumped as tailings material. The aim of this study was to establish whether mesofauna could be utilized to assess the influence of the tailings disposal facility on the surrounding soil environment. The sampled soil was chemically analyzed and the extracted mesofauna identified. High metal concentrations on the tailings dam (Cu, Cr and Ni), apparently had the greatest influence on the soil mesofauna. Only a few mite species were abundant at the two sites on the tailings dam, representing the prostigmatic-, cryptostigmatic- and the mesostigmatic-taxa. Metal pollution is evident in the sites on the tailings dam facility and the number of species generally increased towards the more natural environment.http://dx.doi.org/10.1016/j.ecoenv.2012.09.02
Inadequate taxonomy and highly divergent COI haplotypes in laboratory and field populations of earthworms used in ecotoxicology. A case study
Full text linkDNA barcoding was used to investigate the phylogenetic delimitations of Eisenia sp field populations and laboratory cultures used in ecotoxicological research in South Africa. A total of three focal groups (used in published works) and two non-focal groups were assessed. These focal groups, including two laboratory cultures and one field population, have been referred to as Eisenia fetida in the literature. Phylogenetic analyses of the COI gene revealed that the taxonomy of these Eisenia sp had been incorrectly assigned since all the generated sequences grouped unequivocally with published sequences of E. andrei. Very high sequence divergence (> 25% K2P) found within E. andrei could signal the occurrence of hitherto non-described cryptic species. These findings are discussed with an emphasis on the possible consequences of using conspecific earthworms specimens with high molecular divergence in ecotoxicological bioassays. It is not clear whether unbeknownst to the researcher, the use of cryptic species in bioassays could jeopardise the quality of ecotoxicological investigations. Early evidence suggests that cryptic oligochaete species may respond differently to metal toxicity. The need for comparative ecotoxicological studies between E. andrei and E. fetida is also evidenced, especially in the light of recent numerous reports of cryptic oligochaete species. Ecotoxicologists are consequently encouraged, whenever possible, to make use of available genomic technologies to screen their laboratory stocks and available field populations for any molecular distinctiveness.http://africanzoology.journals.ac.za/pub/article/view/808/926http://africanzoology.journals.ac.za/pu
Molecular assessment of commercial and laboratory stocks of Eisenia spp. (Oligochaeta: Lumbricidae) from South Africa
Full text linkDNA barcoding was used to investigate laboratory and commercial stocks of Eisenia species from four provinces of South Africa. The COI gene was partially amplified and sequenced in selected earthworms from eight local populations (focal groups) and two European laboratory stocks (non-focal groups). Only nine COI haplotypes were identified from the 224 sequences generated. One of these haplotypes was found to belong to the megascolecid Perionyx excavatus. The remaining eight haplotypes belonged to the genus Eisenia, although only a single E. fetida haplotype, represented by six specimens, was found in one of the European populations. The other seven haplotypes, all occurring in South Africa, were E. andrei. One of the commercial stocks from South Africa and a laboratory culture from Europe were mixtures of E. andrei – P. excavatus and E. andrei – E. fetida, respectively. Previous allozyme studies have helped to suggest that some of the populations included in this study may be suffering from inbreeding depression, which could result in adverse consequences for both the vermiculture industry and ecotoxicological research in South Africa.http://africaninvertebrates.org/ojs/index.php/AI/article/view/327http://africaninvertebrates.org/ojs/index.php/AI/inde
Heavy metal threats to plants and soil life in Southern Africa: Present knowledge and consequences for ecological risk assessment
No full textIn recent times there has been remarkable development in the field of soil ecotoxicology and risk assessment (RA) models. It is, however, debatable if these RA models are robust representatives for worldwide relevance. In order to investigate this, the current overview aims to address heavy metal threats to soil life in southern Africa by investigating present knowledge and consequences for RA using research in southern Africa as a case. To this end, the focus is on southern African soils, soil life and living conditions. To critically discuss these issues, we report on extensive research conducted in the southern African context and looked how comparable these findings are to RA models employed in the western world. This is done by providing an inventory of selected studies focused on the ecotoxicity of metals towards soil life. It is concluded that there is a dearth of information on southern African soil life, most of which are laboratory-based studies carried out by a handful of researchers. Future research incorporating the available information into a soil ecosystem assessment procedure is paramount. It is recommended that a starting point to tackle this might be the development of holistic sight-specific guidelines for ecological risk assessment at larger spatial scales (km2) which takes into cognizance landscapes, vegetation and faunal characteristics.</p
Effect of biofumigants on soil microbial communities and ecotoxicology of earthworms (Eisenia andrei)
No full textBiofumigation is considered a good alternative to chemical fumigation because it can control crop pathogens and diseases with lower health and environmental risks than chemical fumigants. Glucosinolates are volatile compounds found in most Brassica species, and when hydrolysed, it forms a range of natural toxins including isothiocyanates that act as biofumigants. However, the effect of glucosinolates and their breakdown products on non-target and beneficial soil organisms is not well documented. Three biofumigants, broccoli, mustard and oilseed radish, were evaluated for their effect on earthworms (Eisenia andrei) and the soil microbial community. Sub-lethal endpoints, including growth and reproductive success of the earthworms, were monitored. Genotoxicity of the biofumigants towards earthworms was evaluated by means of the comet assay. Broccoli reduced earthworm reproduction while mustard induced more DNA strand breaks in earthworm cells compared to the control. Soil microbial community function and structure were evaluated by means of community level physiological profiling and phospholipid fatty acid analyses. The effects exerted by the biofumigants on the microbial community were the most pronounced within the first 14 days after application. Carbon substrate utilisation was most affected by the oilseed radish treatment and microbial community structure by the mustard treatmen
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