Effects of different drying processes on the concentrations of metals and metalloids in plant materials.

6 p.The drying process of fresh plant materials may affect the porous structure, dehydration and a number of quality characteristics of these materials. Therefore, this study has investigated the effect of different drying processes on the variation of metal and metalloid concentrations in the dried plant materials. Seven varieties of native plant species collected from Sa˜o Domingos mine were analyzed by instrumental neutron activation analysis(INAA) to investigate the effects of freeze-drying (FD),ambient air-drying (AAD) and oven-drying (OD) process on the concentrations of metals and metalloids in the plant biomass. Comparison of ambient air-dried, oven-dried and freeze-dried preparations allows a phenomenological description of the dehydration artefacts. In the quantitative analysis of metals and metalloids, FD and OD plant samples show the higher concentrations of metals and metalloids when compared to those in the AAD plant biomass. The freeze-drying process is comparatively reliable for determination of metals and metalloids concentrations in plant materials.This research work was supported by the Fun- 242 dac¸a˜o para Cieˆncia e Tecnologia (FCT, Portugal) through research 243 contract PTDC/AMB/65462/2006—HYPERAS. The principal author 244 (H.M.A) thanks FCT for his post-doctoral grant.Peer reviewe

Arsenic-phosphorus interactions in the soil-plant-microbe system: dynamics of uptake, suppression and toxicity to plants

High arsenic (As) concentrations in the soil, water and plant systems can pose a direct health risk to humans and ecosystems. Phosphate (Pi) ions strongly influence As availability in soil, its uptake and toxicity to plants. Better understanding of As(V)-Pi interactions in soils and plants will facilitate a potential remediation strategy for As contaminated soils, reducing As uptake by crop plants and toxicity to human populations via manipulation of soil Pi content. However, the As(V)-Pi interactions in soil-plant systems are complex, leading to contradictory findings among different studies. Therefore, this review investigates the role of soil type, soil properties, minerals, Pi levels in soil and plant, Pi transporters, mycorrhizal association and microbial activities on As-Pi interactions in soils and hydroponics, and uptake by plants, elucidate the key mechanisms, identify key knowledge gaps and recommend new research directions. Although Pi suppresses As uptake by plants in hydroponic systems, in soils it could either increase or decrease As availability and toxicity to plants depending on the soil types, properties and charge characteristics. In soil, As(V) availability is typically increased by the addition of Pi. At the root surface, the Pi transport system has high affinity for Pi over As(V). However, Pi concentration in plant influences the As transport from roots to shoots. Mycorrhizal association may reduce As uptake via a physiological shift to the mycorrhizal uptake pathway, which has a greater affinity for Pi over As(V) than the root epidermal uptake pathway

Water Quality, Mitigation Measures of Arsenic Contamination and Sustainable Rural Water Supply Options in Bangladesh

Arsenic contamination of groundwater has created a serious public health issue in Bangladesh and West Bengal (India), because groundwater is widely used for drinking, household and agriculture purposes. Given the magnitude of the problem of groundwater contamination facing Bangladesh, effective, acceptable and sustainable solutions are urgently required. Different NGOs (Non-government organizations) and research organizations are using their extensive rural networks to raise awareness and conduct pilot projects. The implication of the results from the previous studies is robust, but coastly arsenic reduction technologies such as activated alumina technology, and As and Fe removal filters may find little social acceptance, unless heavily subsidized. This review paper analysed the quality of surface water and ground water, all mitigation measures and the most acceptable options to provide sustainable access to safe- water supply in the rural ares of Bangladesh. Although there are abundant and different sources of surface water, they can not be used for drinking and hosehold purposes due to lack of sanitation, high faecal coliform concentration, turibidity and deterioration of quality of surface water sources. There are a few safe surface water options; and also there are several methods available for removal of arsenic and iron from groundwater in large conventional treatments plants. This review paper presented a short description of the currently available and most sustainable technologies for arsenic and iron removal, and alternative water supply options in the rural areas

Flourescence Humic Substances in Arsenic Contaminated Groundwater of Bangladesh

In the past, only arsenic (As) concentrations in groundwater of Bangladesh were considered as having direct effects on the epidemical degrees of different types of diseases including arsenicosis, but the results of the present investigation indicated that fluorescence humic substance (HS) is also an important component of dissolved organic matter in groundwater of Bangladesh. Therefore, it is suspected that both fluorescent HS and As in groundwater may have effects on the biological toxicity. The evidence of presence of high fluorescent HS and As in groundwater of Faridpur supports the above synergistic effect. The spatial distribution of fluorescence HS and As in groundwater of Faridpur indicated that the variations may be related to local hydrogeological conditions

Biochar : an emerging panacea for remediation of soil contaminants from mining, industry and sewage wastes

Mine tailings, waste rock piles, acid mine drainage, industrial wastewater, and sewage sludge have contaminated a vast area of cultivable and fallow lands, with a consequence of deterioration of soil and water quality and watercourses due to the erosion of contaminated soils for absence of vegetative cover. High concentrations of toxic elements, organic contaminants, acidic soils, and harsh climatic conditions have made it difficult to re-establish vegetation and produce crops there. Recently, a significant body of work has focussed on the suitability and potentiality of biochar as a soil remediation tool that increases seed emergence, soil and crop productivity, above ground biomass, and vegetation cover on mine tailings, waste rock piles, and industrial and sewage waste-contaminated soils by increasing soil nutrients and water-holding capacity, amelioration of soil acidity, and stimulation of microbial diversity and functions. This review addresses: i) the functional properties of biochar, and microbial cycling of nutrients in soil; ii) bioremediation, especially phytoremediation of mine tailings, industrial waste, sewage sludge, and contaminated soil using biochar; iii) impact of biochar on reduction of acid production, acid mine drainage treatment, and geochemical dynamics in mine tailings; and iv) treatment of metal and organic contaminants in soils using biochar, and restoration of degraded land.12 page(s

Poultry Litter Biochar Increases Mycorrhizal Colonisation, Soil Fertility and Cucumber Yield in a Fertigation System on Sandy Soil

There is a continuing argument about the benefits of biochar on arbuscular mycorrhizal (AM) symbiosis, crop growth, yield, and fertility of soil. There is also limited research on the effects of biochar on AM colonization, cucumber yield, and soil fertility improvement. Therefore, this investigation aimed to determine the impact of poultry litter biochar (PLB) on colonization of roots by indigenous AM fungi in agricultural soil and their contribution to cucumber yield, nutrition, and soil fertility improvement. A field trial was conducted to assess the effect of PLB combined with compound poultry manure (CPM) and nitrophos (NP) fertilizer to investigate the response of treatments on nutrient-deficient sandy soils. Plant growth responses to biochar showed better plant growth and yield of cucumber. Application of biochar with and without CPM and NP reduced the negative impact of nutrient deficiency stress on cucumber growth. AM fungal colonization, soil fertility, and cucumber yield were improved with the combined application of biochar, CPM, and NP fertilizer. Post-harvest, soil C, N, P, K, Ca, Mg, S, Zn, Cu, Fe, and Mn increased with application of biochar applied with CPM and NP. Biochar application with CPM and NP also increased the percent root colonization of cucumber. Use of biochar with CPM and NP has the potential to improve plant growth, yield, nutrient uptake, and soil fertility. Further studies in various agro-ecological conditions would help utilize this technology in sustainable crop production

Influences of biochar and biochar-mineral complex on mycorrhizal colonisation and nutrition of wheat and sorghum

The high price of synthetic fertilisers and the price barrier for biochar as a soil amendment have encouraged the exploration of using biochar in fertiliser replacement formulations. Biochars coupled with fertilisers can be applied at lower application rates to achieve benefits in plant growth and nutrition, as well as soil biological fertility. It is necessary to evaluate the use of biochar as a fertiliser substitute. Therefore, this study investigated the comparative influences of biochars, including Acacia saligna (AS), Simcoa jarrah (SJ) and Wundowie jarrah (WJ), mineral fertiliser with microbes (MF + M), biochar-mineral complex (BMC) and their combination on mycorrhizal colonisation, growth and nutrition of wheat in a glasshouse experiment and sorghum in field conditions. BMC + MF + M treatment produced higher mycorrhizal colonisation than MF + M alone, indicating that BMC had a significant role in increasing mycorrhizal colonisation. SJ (treated with acetic acid) and MF + M treatments, as well as AS + MF + M application, showed similar effects on mycorrhizal colonisation, but lower colonisation than the BMC + MF + M treatment. Overall, the BMC + MF + M treatment supported the maximum shoot, root and total plant dry weight followed by AS + MF + M and WJ + MF + M. The MF + M treatment had the maximum shoot N and K concentrations, while BMC + MF + M application had the maximum shoot P concentration. AS + MF + M and WJ + MF + M treatments supported the maximum N uptake by wheat shoots, while BMC + MF + M supported the maximum P uptake. The results showed that biochars and BMCs could increase mycorrhizal colonisation, plant growth and nutrient uptake of wheat, particularly N, P, K, S and Zn. The field experiment confirmed that BMC application at a rate of 300 kg ha-1 could increase the yield of irrigated sorghum on a loam soil and provide better applied P use efficiency compared to a water-soluble fertiliser alone. These results indicated that biochar-based fertilisers might increase the resilience and sustainability of dryland cropping in environments such as in Western Australia and warrant further field evaluation

Arsenic Contamination in Groundwater of Bangladesh: Perspectives on Geochemical, Microbial and Anthropogenic Issues

A groundwater, sediment and soil chemistry and mineralogical study has been performed to investigate the sources and mobilization process of Arsenic (As) in shallow aquifers of Bangladesh. The groundwater from the shallow aquifers is characterized by high concentrations of Arsenic (47.5–216.8 µg/L), iron (0.85–5.83 mg/L), and phosphate, along with high electrical conductivity (EC). The groundwater has both very low oxidation-reduction potential (Eh) and dissolved oxygen (DO) values indicating reducing conditions. By contrast, the deep aquifers and surface waters (pond, canal) have very low concentrations of Arsenic ( < 6 µg/L), iron (0.12–0.39 mg/L), and phosphate along with a relatively low EC. Furthermore, the values of Eh and DO are high, indicating oxic to suboxic conditions. Arsenic is inversely correlated with Eh values in the upper aquifer, whereas no relationship in the deeper aquifer is observed. These results suggest that As mobilization is clearly linked to the development of reducing conditions. The clayey silt, enriched in Fe, Mn, Al oxides and organic matter, and deposited in the middle unit of shallow aquifers, contains moderately high concentrations of As, whereas the sediments of deep aquifers and silty mud surface soils from paddy fields and ponds contain a low content of As (Daudkandi area). Arsenic is strongly correlated with the concentrations of Fe, Mn and Al oxides in the core samples from the Daudkandi and Marua areas. Arsenic is present in the oxide phase of Fe and Mn, phyllosilicate minerals and in organic matter in sediments. This study suggests that adsorption or precipitation of As-rich Fe oxyhydroxide on the surface or inner sites of biotite might be responsible for As concentrations found in altered biotite minerals by Seddique et al. Microbially or geochemically mediated reductive dissolution of Fe oxyhydroxides is the main mechanism for As release. The reducing conditions are caused by respiratory decomposition of organic matter, either sedimentary or labile organic C. The process can be accelerated by agricultural activity and domestic organic wastes. An agricultural fertilizer can directly contribute As to groundwater as well as promote As mobilization by ion-exchange with phosphorus

Effects of enriched biochars containing magnetic iron nanoparticles on mycorrhizal colonisation, plant growth, nutrient uptake and soil quality improvement

At present, there is little commercial sale of biochar, since farmers find they can not gain a return on their investment in this amendment in the first few years after its application, because of the high cost associated with large application rates. To overcome this constraint, development of artificially aged enriched biochar-mineral complexes (BMCs), having a higher mineral content, surface functionality, exchangeable cations, high concentration of magnetic iron (Fe) nanoparticles, and higher water-extractable organic compounds has been undertaken by a combined team of researchers and a commercial company. Two biochars produced under different pyrolysis conditions were activated with a phosphoric acid treatment. A mixture of clay, chicken litter, and minerals were added to the biochar, and then this composite was torrefied at either 180 or 220 ◦C. In this study a pot experiment was carried out in glasshouse conditions to determine the effects of four different BMCs, with different formulations applied at rates of 100 and 200 kg ha−1 , on the mycorrhizal colonisation, wheat growth and nutrient uptake, and soil quality improvement. It was found that the phosphorus (P) and nitrogen uptake in wheat shoots were significantly greater for a low application rate of BMCs (100 kg ha−1 ). The present formulation of BMC was effective in enhancing growth of wheat at low application rate (100 kg ha−1 ). The increase in growth appeared due to an increase in P uptake in the plants that could be partly attributed to an increase in mycorrhizal colonisation and partly due to the properties of the BMC