Effects of Cd and Pb on soil microbial community structure and activities

Background, aim, and scope  

Soil contamination with heavy metals occurs as a result of both anthropogenic and natural activities. Heavy metals could have long-term hazardous impacts on the health of soil ecosystems and adverse influences on soil biological processes. Soil enzymatic activities are recognized as sensors towards any natural and anthropogenic disturbance occurring in the soil ecosystem. Similarly, microbial biomass carbon (MBC) is also considered as one of the important soil biological activities frequently influenced by heavy metal contamination. The polymerase chain reaction–denaturing gradient gel electrophoresis (DGGE) has recently been used to investigate changes in soil microbial community composition in response to environmental stresses. Soil microbial community structure and activities are difficult to elucidate using single monitoring approach; therefore, for a better insight and complete depiction of the soil microbial situation, different approaches need to be used. This study was conducted in a greenhouse for a period of 12 weeks to evaluate the changes in indigenous microbial community structure and activities in the soil amended with different application rates of Cd, Pb, and Cd/Pb mix. In a field environment, soil is contaminated with single or mixed heavy metals; so that, in this research, we used the selected metals in both single and mixed forms at different application rates and investigated their toxic effects on microbial community structure and activities, using soil enzyme assays, plate counting, and advanced molecular DGGE technique. Soil microbial activities, including acid phosphatase (ACP), urease (URE), and MBC, and microbial community structure were studied.     

Physico-chemical removal of iron from semi-aerobic landfill leachate by limestone filter

Limestone has been proven effective in removing metals from water and wastewater. A literature review indicated that limestone is capable of removing heavy metals such as Cu, Zn, Cd, Pb, Ni, Cr, Fe and Mn are through a batch process or by filtration technique. The removal capability is reported at up to 90%. However, to date most of the studies have been focused on synthetic wastewater. The present study attempts to investigate the suitability of limestone to attenuate total iron (Fe) from semi aerobic leachate at Pulau Burung Landfill Site in Penang, Malaysia. Iron was found in significant quantities at the landfill site. The study also aims to establish the Fe isotherm and breakthrough time of the proposed limestone filter for post-treatment to the migrating landfill leachate before its release to the environment. The Fe isotherms were established using a batch equilibrium test, while the breakthrough characteristics were determined using continuous flow permeating through a limestone column. The latter was used in order to simulate the continuous flow of leachate that would occur in the proposed limestone filter. The limestone media used in the experiment contain more than 90% CaCO3 with particle sizes ranging from 2 to 4 mm. Four filter columns (each 150 mm in diameter and 1000 mm depth) were installed at the landfill site. Metal loadings were kept below 0.5 kg /m3 day and the experiment was run continuously for 30 days. Initial results indicated that 90% of Fe can be removed from the leachate based on retention time of 57.8 min and surface loading of 12.2 m3/m2 day. For the batch study on the Fe isotherm, the results indicated that limestone is potentially useful as an alternative leachate treatment system at a relatively low cost.     

A comprehensive review of technologies used to improve the performance of PV systems in a view of cooling mediums,reflectors design,spectrum splitting,and economic analysis

Environmental Science and Pollution Research - Solar photovoltaic panels are increasingly being used throughout the world, particularly in Egypt, where a station has been constructed in the city of...     

A review on application of activated carbons for carbon dioxide capture: present performance,preparation, and surface modification for further improvement

Environmental Science and Pollution Research - The atmosphere security and regulation of climate change are being continuously highlighted as a pressing issue. The crisis of climate change owing to...     

Indicator-Based Approach for Assessing the Vulnerability of Freshwater Resources in the Bagmati River Basin,Nepal

To assess the vulnerability of water resources in the Bagmati River Basin in Nepal, this paper adopts an indicator-based approach wherein vulnerability is expressed as a function of water stress and adaptive capacity. Water stress encompasses indicators of water resources variation, scarcity, and exploitation and water pollution, whereas adaptive capacity covers indicators of natural, physical, human resource, and economic capacities. Based on the evaluation of eleven indicators, which were aggregated into eight vulnerability parameters, an increasingly stressful situation and lack of adaptive capacity became evident. Considerable spatial variation in indicator values suggests differential policy options. While the northern parts need attention to reduce pollution loading and conserve vegetation cover, the southern parts need improvements in physical capacity, i.e. water infrastructures. The comprehensive and easily interpretable findings of the study are expected to help decision makers reach sound solutions to reduce freshwater resources vulnerability in the Bagmati River Basin, Nepal. With its inherent flexibility, the approach has demonstrated its potential for application in different times and areas for monitoring and comparison purposes.     

Fenton degradation of dialkylphthalates: products and mechanism

Contamination of wastewater by organic pollutants is a major worldwide issue. For instance plastic additives such as phthalates are found in wastewater. Efficient techniques are thus needed to clean wastewaters. The Fenton reaction involving H₂O₂ and Fe(II) salts can be used to treat polluted water. During the Fenton reaction pollutants are decomposed directly by hydroxyl radicals. In some cases toxic by-products are produced. Here dimethyl phthalate, diethyl phthalate, and dipropyl phthalate by-products formed during the Fenton reaction were studied. Fenton degradation of selected phthalates yielded numerous transformation products such as hydroxylated phthalates. The hydroxylation reaction occurred at the aromatic ring of phthalates and yielded mono- and dihydroxylated phthalates. For monohydroxylated phthalate, 3-hydroxy- and 4-hydroxydialkylphthalates are the main transformation products. In addition to hydroxylated derivatives, aliphatic chain degraded mono- and dihydroxylated phthalates were also detected.     

Statistical analysis of PM10 concentrations at different locations in Malaysia

Malaysia has experienced several haze events since the 1980s as a consequence of the transboundary movement of air pollutants emitted from forest fires and open burning activities. Hazy episodes can result from local activities and be categorized as "localized haze". General probability distributions (i.e., gamma and log-normal) were chosen to analyze the PM(10) concentrations data at two different types of locations in Malaysia: industrial (Johor Bahru and Nilai) and residential (Kota Kinabalu and Kuantan). These areas were chosen based on their frequently high PM(10) concentration readings. The best models representing the areas were chosen based on their performance indicator values. The best distributions provided the probability of exceedances and the return period between the actual and predicted concentrations based on the threshold limit given by the Malaysian Ambient Air Quality Guidelines (24-h average of 150 μg/m(3)) for PM(10) concentrations. The short-term prediction for PM(10) exceedances in 14 days was obtained using the autoregressive model.     

Rapid release of heavy metals and anions from polyethylene laminated paper cups into hot water

Polyethylene laminated disposable paper cups are commonly used as a container for hot drinks, yet there is limited knowledge on the transfer of contaminants from the cup to the drink. Here we poured 95^?C hot water in 14 cups, to simulate the preparation of hot beverage for daily use. We studied the water composition after 15 min by inductively coupled plasma mass spectrometry (ICP-MS) and ion chromatography. Results show the presence of metals such as vanadium, chromium, copper, cobalt and arsenic at concentration ranging from 0.04 to 1.80 µg/L. Nitrate, nitrite, chloride, bromate, fluoride and sulfate ions were also detected at concentration from 0.003 to 49.21 mg/L. All concentrations are below the WHO maximum permissible limits in drinking water. However, the levels of vanadium at 1.24 µg/L and fluoride ions at 1.03 mg/L are likely to induce a health risk by bioaccumulation after long-term water ingestion. Therefore paper cups composition should be modified to avoid the release of contaminants in hot drinks.