Abatement of chlorinated compounds in groundwater contaminated by HCH wastes using ISCO with alkali activated persulfate.

In this work, in situ chemical oxidation (ISCO) with alkali activated persulfate has been tested for the elimination of HCH isomers and other chlorinated compounds in groundwater from Sabiñanigo (Sardas landfill), which was contaminated by solid and liquid wastes illegally dumped in the area by a company producing lindane. Due to the site lithology and the type of pollutants found in groundwater (HCHs and chlorobenzenes) alkali (NaOH) activated persulfate (PS) was selected as oxidant. The influence of variables such as PS concentration (42-200mM) and NaOH:PS molar ratio (2:1 to 4:1) on chlorinated compound abatement has been studied and a kinetic model to predict the composition of all chlorinated organic compounds (COCs) in the aqueous phase with time was obtained. It was found that a fast initial hydrodechlorination reaction took place in which HCH isomers reacted to trichlorobenzenes (mainly 1,2,4 TCB) at pH≥12. Mono-, di-, tri and tetrachlorobenzenes remaining were oxidized without producing aromatic intermediates. At the condition tested a first order kinetic model for COCs and PS concentration was obtained. Zero order alkali concentration was obtained while pH was being kept at 12 for the whole reaction time.

Remediation of aged diesel contaminated soil by alkaline activated persulfate.

The present work studies the efficiency of alkaline activated persulfate (PS) to remediate an aged diesel fuel contaminated soil from a train maintenance facility. The Total Petroleum Hydrocarbon (TPH) concentration in soil was approximately 5000mgkg-1 with a ratio of aliphatic:aromatic compounds of 70:30. Aromatic compounds were mainly naphtalenes and phenanthrenes. The experiments were performed in batch mode where different initial concentrations of persulfate (105mM, 210mM and 420mM) and activator:persulfate ratios (2 and 4) were evaluated, with NaOH used as activator. Runs were carried out during 56days. Complete TPH conversion was obtained with the highest concentration of PS and activator, whereas in the other runs the elimination of fuel ranged between 60 and 77%. Besides, the abatement of napthalenes and phenantrenes was faster than aliphatic reduction (i. e. after 4days of treatment, the conversions of the aromatic compounds were around 0.8 meanwhile the aliphatic abatements were 0.55) and no aromatic oxidation intermediates from naphtalenes or phenantrenes were detected. These results show that this technology is effective for the remediation of aged diesel in soil with alkaline pH.

Accumulation of mercury in Typha domingensis under field conditions.

Typha species is a common wetland plant used in the treatment of urban and industrial effluents. But, despite their widespread implementation, there are not many studies based on the behaviour of this plant growing in an areas affected by mercury. The present work investigates the ability of Typha domingensis to accumulate mercury under field conditions. The study area was along the Valdeazogues river which flows through the Almadén mining district (Ciudad Real, Spain) that is considered the largest mercury reservoir in the world. The mercury concentration in different plant fractions was measured as well as the available and total concentration in the bottom sediments. The results showed that the highest mercury concentrations were found in the belowground organs. T. domingensis had a high efficiency to accumulate mercury in their organs although available metal concentrations in the environment did not exceed 0.16 mg kg(-1). Bioaccumulation factors (BAF) ranged between 121 and 3168 in roots. Furthermore, significant correlations were found between mercury concentration in all plant organs and Hg in sediments (both total and available). These results demonstrated that T. domingensis could be used as a biomonitor as well as in phytoextraction technology in areas affected by mercury.