Particle-facilitated lead and arsenic transport in abandoned mine sites soil influenced by simulated acid rain.

The role of acid rain in affecting Pb and As transport from mine tailings was investigated by pumping simulated acid rain at a infiltration rate of 10.2 cm/h through soil columns. Simulated acid rain with pH of 3.0, 4.5 and 5.6 were used as leaching solutions. Results showed that 86.9-95.9% of Pb and 90-91.8% of As eluted from the columns were adsorbed by particles in the leachates. Scanning electron microscopy (SEM) analysis showed that particles released from the columns were mainly composed of flocculated aggregates and plate or rod shaped discrete grains. Transmission electron microscopy (TEM) coupled with energy dispersive X-ray analysis (EDX) showed that these particles were predominantly silicate minerals. Results from our experiments demonstrated that when rapid infiltration conditions or a rainstorm exist, particle-facilitated transport of contaminants is likely to the dominant metal transport pathway influenced by acid rain.

Application of sewage sludge compost on highway embankments.

More and more sewage sludge is being produced in China. Safe and economical methods for sewage sludge disposal should be found considering the increase in sewage treatment. In order to verify the feasibility of sludge disposal on newly built highway embankments, five treatments (0, 15, 30, 60 and 120 tons ha(-1)) of sewage sludge compost (SSC) were added to a silty-clay embankment soil on the Xi-Huang highway. The results showed that amendment with SSC increased soil available N, available P, organic matter, cation exchange capacity, and water content, and decreased soil bulk density. Application of SSC enhanced ryegrass growth and reduced runoff and soil erosion. Heavy metal losses from sediments in runoff remained constant or decreased relative to the control until a rate of 60 tons ha(-1) was exceeded, when heavy metal losses appeared to increase.

Characterization and control of odorous gases at a landfill site: a case study in Hangzhou, China.

Municipal solid waste (MSW) landfills are one of the major sources of offensive odors potentially creating annoyance in adjacent communities. At the end of May 2007, an odor pollution incident occurred at the Tianziling landfill site, Hangzhou, China, where the residents lodged complaints about the intense odor from the landfill, which drew a significant attention from the government. In this study, ambient air monitoring was conducted at the Tianziling landfill site. The main odor composition of the gas samples collected on June 1st 2007 and the reduction of various odorous gases from the samples collected on June 1st 2009 due to the applied odor control techniques were determined using gas chromatography-mass spectrometry (GC-MS). In addition, variations of primary odorous gaseous (NH(3) and H(2)S) concentrations at different locations in the landfill site from July 2007 to June 2009 were also investigated by using classical spectrophotometric methods. Results showed that a total of 68 volatile compounds were identified among which H(2)S (56.58-579.84 µg/m(3)) and NH(3) (520-4460 µg/m(3)) were the notable odor components contributing to 4.47-10.92% and 83.91-93.94% of total concentrations, respectively. Similar spatial and temporal shifts of H(2)S and NH(3) concentrations were observed and were significantly affected by environmental factors including temperature, air pressure and wind direction. Odor pollution was worse when high temperature, high humidity, low air pressure, and southeast, northeast or east wind appeared. Moreover, the environmental sampling points of the dumping area and the leachate treatment plant were found to be the main odor sources at the Tianziling landfill site. The odor control technologies used in this project had a good mitigating effect on the primary odorous compounds. This study provides long-term valuable information concerning the characteristics and control of odors at landfill sites in a long run.