Saline melt water from road salt applications that has percolated into a fine sandy soil in winter is rinsed out of the soil by infiltrating rainwater in the following warmer seasons. This sequence of saturated and unsaturated flow processes associated with saline water transport in a fine sandy soil was studied by simulation and exploratory laboratory experiments. Experiments in soil columns of 300-μm sand revealed that two rinses of pure water, each of one pore volume, were sufficient to reduce the salt concentration by 99% of its original value in the soil column. Simulated time variations of salt concentration in the effluent from the column agreed with experimental results. Based on simulated and experimental results, a sandy soil must become saturated to experience pore water flow in order to efficiently rinse saline snowmelt water. Depending on the saturated hydraulic conductivity and the soil depth, days, weeks, or months of freshwater infiltration in summer are needed to rinse saline melt water from an unsaturated sandy soil after road salt applications in winter. This explains findings of significant salt concentrations in surface and shallow groundwater during summer months, long after road salt application and infiltration has ceased.

This study was carried out to examine heavy metal accumulation in rice grains and brassicas and to identify the different controls, such as soil properties and soil heavy metal fractions obtained by the Community Bureau of Reference (BCR) sequential extraction, in their accumulation. In Guangdong Province, South China, rice grain and brassica samples, along with their rhizospheric soil, were collected from fields on the basis of distance downstream from electroplating factories, whose wastewater was used for irrigation. The results showed that long-term irrigation using the electroplating effluent has not only enriched the rhizospheric soil with Cd, Cr, Cu, and Zn but has also increased their mobility and bioavailability. The average concentrations of Cd and Cr in rice grains and brassicas from closest to the electroplating factories were significantly higher than those from the control areas. Results from hybrid redundancy analysis (hRDA) and redundancy analysis (RDA) showed that the BCR fractions of soil heavy metals could explain 29.0 and 46.5 % of total eigenvalue for heavy metal concentrations in rice grains and brassicas, respectively, while soil properties could only explain 11.1 and 33.4 %, respectively. This indicated that heavy metal fractions exerted more control upon their concentrations in rice grains and brassicas than soil properties. In terms of metal interaction, an increase of residual Zn in paddy soil or a decrease of acid soluble Cd in the brassica soil could enhance the accumulation of Cd, Cu, Cr, and Pb in both rice grains and brassicas, respectively, while the reducible or oxidizable Cd in soil could enhance the plants’ accumulation of Cr and Pb. The RDA showed an inhibition effect of sand content and CFO on the accumulation of heavy metals in rice grains and brassicas. Moreover, multiple stepwise linear regression could offer prediction for Cd, Cu, Cr, and Zn concentrations in the two crops by soil heavy metal fractions and soil properties.

The use of treated grey water (GW) for home gardens, peri-urban agriculture and landscaping is becoming popular in many water stressed countries such as Oman. This study aims to investigate the treatment efficacy, health and chemical concerns, cost-benefits and maintenance protocol of a GW treatment system as well as the effect of irrigation with GW on crop yield. Therefore, a decentralized homemade GW treatment system was installed in a newly constructed house in Muscat, Oman and studied over a 2-year period. The treated GW was found to be suitable for irrigation as per Omani standards. GW when mixed with kitchen effluent substituted the use of nutrient supplements for plants and did not show any harmful chemical or biological contamination. The capital cost of the system was around US $980, and the annual operating cost was US $78 with annual income and savings from the system being around US $572 indicating a payback period of nearly 2 years. It was found that the system required simple but regular maintenance particularly cleaning of the top layer of the filter. It can be concluded from this study that such a GW system should be technically, economically and environmentally feasible in Oman. Also, wider acceptance by the general public to the idea of GW reuse will help in mitigating the water shortage problem of the country to some extent.

Plants of the urban environment are exposed to a wide range of pollutants, including heavy metals. This research studies in situ the eco-physiological and antioxidant responses of holm oak (Q. ilex) leaves to Pb and Cd to assess the mechanisms of metal tolerance in this species, widely used as biomonitor. Leaves of plants grown at parks and roadsides were analyzed for photosynthetic activity, Pb and Cd concentration in tissues and cell-free extracts, thiol groups, D1 and Rubisco protein content, ascorbic acid (AsA) amount, and catalase (CAT) activity. The main results evidenced that Cd concentration was higher in leaves collected at the park out from the downtown; whereas Pb was most abundant in leaves sampled at the roadside nearby the highway. Pb in cell-free extracts was higher in park than in roadside leaves. Although Cd in the leaf tissues was twofold lower than Pb, it was more abundant than Pb in cellular extracts deprived of all particulate matter. Leaves responded to different concentration of Cd and Pb modulating some eco-physiological and biochemical traits, roadside leaves showed reduced leaf lamina, higher content of photosynthetic pigments, hydrogen peroxide, and AsA, as well as higher CAT activity compared to park leaves. In the roadside leaves, a stress condition for photosynthetic apparatus can be hypothesized on the basis of the decline of photochemical activity, the increase of NPQ, and the reduction of Rubisco and D1 protein content. The elevated presence of thiol groups in these leaves suggests a possible role of Pb and Cd in activation of antioxidant responses.

The total petroleum hydrocarbon (TPH) extraction potential of organic solvents including dichloromethane (DCM), pentane, hexane, methanol, ethanol, propanol, and acetone was investigated along with the effect of water content in solvents for their efficiency of extraction. The extent of TPH extraction was analyzed using various extraction schemes (i.e., solvent/solid ratio, treatment time, extraction method, solvent/water ratio) to better understand the physical and chemical factors controlling TPH release from contaminated soils. More TPH was extracted with increasing solvent/solid ratio and increasing time. The extent of TPH extracted also varied depending on the extraction method, solvent type, and solvent/water ratio, but was highest when using the total extraction method and 100% DCM. However, the efficiency of TPH extraction decreased dramatically with the increase in the water content in organic solvents. The results also showed that TPH extraction using DCM was the best option for achieving cost-effective, eco-friendly outcomes along with remediation goals. DCM used in solvent extraction to remediate diesel-contaminated soils showed low toxicity, low cost, high recycling potential, and high efficiency compared to the other solvents tested in this study.

Air sparging (AS) is one of the most efficient techniques for remediating saturated soils and groundwater contaminated with volatile organic compounds. Most studies have focused on how the subsurface conditions control the AS process; however, the “side-effects” of AS that feed back to subsurface environment have not been well addressed. This paper studied the perturbation of porous media induced by AS and the consequent multi-parameter changes with the support of Miller soil box and resistivity test, and Darcy experiment and tracer breakthrough test. The Miller soil box test shows that the resistivity response can be credibly used as a non-intrusive method to indicate the porosity change, and that the porosity-resistivity data can be well fitted using Archie equation (R ² > 0.98). Based upon the electricity measurement and above quantitive relationship, it was found that the porosity increased near the air injection point and decreased near the upper boundary of the column due to the upward-transport of particles during air sparging. The changes in porosity were found to be directly proportional to the air injection rate, and the maximum absolute variation of porosity was up to 0.104 at the air flow rate of 20 ml/min, while it did not change in the absence of AS. Both the hydraulic conductivity and dispersion coefficient increased after AS perturbation as the preferential flow pathway formed. The two parameters changed from 3.40 m/d and 0.110 to 6.13 m/d and 0.288, respectively, at 20 ml/min. This work provides useful insight into the changes in flow and transport properties of porous media induced by AS, which then help to understand the instability of air flow and the parameter-uncertainty analysis in related AS model.

PLFA analysis was conducted to profile microorganisms and trace sulfate-reducing bacteria (SRB) in water samples from an offshore oil reservoir. From the results of spiked phospholipid standards, more than 90% of the phospholipids were recovered before the treatment of fatty acid methyl ester (FAME) derivatization while the relative standard deviations (RSD) were below 8.0%. The water samples from the injection well and four producing wells exhibited various reducing conditions and were further subjected to PLFA analysis. Fourteen kinds of phospholipid fatty acids were detected in the five wellbores and the concentrations of total fatty acids ranged from 368.4 to 3468.9 ng/L. Possible SRB biomarkers and significant phospholipid fatty acids associated with SRB including C14:0, i-C15:0, a-C15:0, C15:0, C16:1 (cis-9), C17:0, C18:1 (cis-9), C18:1 (cis-11) and C18:0 were selected for determining the presence of SRB species and evaluating the sulfate-related microbial biomass. The possible existence of SRB genera Desulfobacter, Desulfotomaculum, Desulfovibrio, and sulfur-oxidizing bacteria (SOB) in the reservoir were proposed based on PLFA profiles. The highest biomass was found in the most reducing well where very limited SOB biomarkers were found. Results indicated that the presence of SRB and SOB species was closely associated with the redox environment of the reservoir wellbores. The species distribution patterns were interpreted to elucidate the biological souring process.

The cost effective maintenance of underwater pressure pipes for sewage disposal in Austria requires the detection and localization of leakages. Extrusion of wastewater in lakes can heavily influence the water and bathing quality of surrounding waters. The Distributed Temperature Sensing (DTS) technology is a widely used technique for oil and gas pipeline leakage detection. While in pipeline leakage detection, fiber optic cables are installed permanently at the outside or within the protective sheathing of the pipe; this paper aims at testing the feasibility of detecting leakages with temporary introduced fiber optic cable inside the pipe. The detection and localization were tested in a laboratory experiment. The intrusion of water from leakages into the pipe, producing a local temperature drop, served as indicator for leakages. Measurements were taken under varying measurement conditions, including the number of leakages as well as the positioning of the fiber optic cable. Experiments showed that leakages could be detected accurately with the proposed methodology, when measuring resolution, temperature gradient and measurement time were properly selected. Despite the successful application of DTS for leakage detection in this lab environment, challenges in real system applications may arise from temperature gradients within the pipe system over longer distances and the placement of the cable into the real pipe system.

Disposal and management of abattoir wastewater have been a long-term concern in a high meat-consuming country like Australia. Land-based application of wastewater is considered to be the most economically viable disposal method and is widely used by abattoirs. In this study, we assessed the effects of long-term abattoir wastewater irrigation on soil physical and chemical characteristics of calcareous soils. Soil samples were collected from 16 different locations with seven 5 cm depths intervals down to 35 cm. Soil properties including soil type, bulk density, moisture holding capacity, pH, electrical conductivity (EC), nitrogen (N), phosphorus (P), carbon (C) and micronutrients were measured. Soil characteristics were compared with non-irrigated soils. The study area receives annually about 327 ML of wastewater with high concentration of N and P (186 and 30.4 mg/L). Overall, the site retained 0.6 t N/ha, 0.1 t P/ha and 0.4 t of K per hectare. Irrigation for over a decade onto the study site has caused a significant change in the soil fertility. Soil total N was increased by 82% compared to non-irrigated. Similarly, soil total P concentration was increased more than sixfold. The overall results showed that the abattoir wastewater irrigation to soil caused very significant changes in soil nutrient levels. These changes indicate need to recapture the surplus nutrient, in particular N, to avoid potential leaching and off-site effects.

A strengthened constructed rapid infiltration (SCRI) system is a sewage treatment system derived from a constructed rapid infiltration (CRI) system. The SCRI tank structure primarily includes saturated and non-saturated layers. The degradation of the chemical oxygen demand (COD) and the conversion of ammonia nitrogen (NH₄⁺-N) are primarily performed in a non-saturated layer. To study the COD and NH₄⁺-N removal process in a non-saturated layer, two organic glass columns with a radius of 2.5 cm and a height of 70 cm were loaded with layers of soil from the Shunyi district of Beijing. The primary goal of this research is to quantify the removal effect factors and the relationship of the COD and NH₄⁺-N in the non-saturated layer. The SCRI system functioned successfully under a wetting-drying ratio of 1:5 with hydraulic loading at 1.0 m³/ (m²·d) for over 2 months. Our results show that the removal rate of NH₄⁺-N is approximately 69.11%, and the removal efficiency of COD is approximately 90.46%. The removal of COD is only slightly affected by pH, while the removal of NH₄⁺-N is greatly influenced by pH.