Over the last few decades, the concentration of cadmium (Cd) in the environment has increased considerably in many countries due to anthropogenic activities. Cd is one of the most toxic pollutants in the environment and affects many metabolic processes in plants. The main objective of this study was to evaluate the response of the production, nutritional, and enzymatic antioxidant system of two tomato genotypes (Calabash Rouge and CNPH 0082) grown in tropical soils that were treated with doses of Cd. Soil samples were collected from the layer of earth at a depth of 0–0.2 m in areas subjected to a minimum of human disturbance. The concentrations of Cd applied to the soil samples were 0, 1, 2, and 4 times (0, 3, 6, and 12 mg kg⁻¹ of Cd) the agricultural intervention value adopted by current environmental legislation in the state of São Paulo, Brazil. Analysis of superoxide dismutase, catalase, glutathione reductase, guaiacol peroxidase, and ascorbate peroxidase activities, formation of stress indicator compound (malondialdehyde—MDA and hydrogen peroxide), parameters of production—dry mass of the shoot and root system (here in after “shoots” and “roots”), as well as nutrition, and both the bioavailable and total levels of this metal in the soil were performed. When the bioavailable content and total levels of Cd in the soil increased as a result of this metal doses applied, the biomass of both shoots and roots decreased in both genotypes (with the exception of the CNPH 0082 grown in clay soil) and displayed lower SPAD (relative chlorophyll index) values when exposed to contaminated environments with Cd concentrations. Cadmium treatment resulted in nutritional imbalances, mainly in terms of N, P, and Mn metabolism. Plants subjected to an elevated available content of metal in the soil exhibited increases in content of MDA and hydrogen peroxide and increased activity of catalase, ascorbate peroxidase, and guaiacol peroxidase in plant tissues when grown in both clay soil and sandy soil. Cadmium was phytotoxic to the plants causing a nutritional imbalance, especially on the metabolisms of N, P, and Mn. An oxidative stress condition was established in response to the Cd treatments applied, which led to changes in peroxidase activity.

Onsite wastewater treatment systems (OWTSs) are commonly used to treat domestic wastewater in the Dickinson Bayou watershed, located between Houston and Galveston. The Dickinson Bayou is classified as “impaired” by the Texas Commission on Environmental Quality due to high levels of indicator bacterium, Escherichia coli. Failing OWTSs in the watershed are possible sources for the impairment of the bayou. Nearly all of the watershed is at risk to failing OWTSs due to high water table and clay content in the soil. The HYDRUS modeling software for water and solute flow through variably saturated media was used to simulate the performance of (1) conventional OWTSs, (2) aerobic treatment units (ATUs) with spray distribution, and (3) mounded OWTSs under conditions indicative of the Dickinson Bayou watershed. The purpose of the study was to simulate system performance under existing conditions. Simulation results indicated that both the conventional and ATU systems fail due to effluent ponding and E. coli transport to the land surface due to high water tables and clay soils in the watershed. Simulations indicated that conventional and ATU systems failed when rainfall intensity was greater than 0.25 cm/h. However, the model simulations indicate mound systems did not fail under existing conditions as they did not allow E. coli to reach the surface or ponding to occur. Consequently, mound systems can be considered as better systems in this watershed to minimize bacterial loadings.

Permeable pavements mitigate the impacts of urbanization on surface waters through pollutant load reduction, both by sequestration of pollutants and stormwater volume reduction through exfiltration. This study examined the non-winter water quality performance of two side-by-side permeable pavements in the Ohio snowbelt. The permeable interlocking concrete pavements were designed to drain impervious catchments 2.2 (large) and 7.2 (small) times larger than their surface area, were located over clay soils, and incorporated the internal water storage design feature. Nutrient reduction was similar to past studies—organic nitrogen and particulate phosphorus were removed through filtration and settling, while dissolved constituents received little treatment. Because of 16 and 32 % volume reductions in the small and large installations, respectively, nutrient loads were often significantly reduced but generally by less than 50 %. Aluminum, calcium, iron, magnesium, lead, chloride, and total suspended solids (TSS) concentrations and loads often increased after passing through the permeable pavements; effluent TSS loads were three- to five-fold higher than influent TSS loads. This was apparently due to seasonal release of clay- and silt-sized particles from the soils underlying the permeable pavement and inversely related to elapsed time since winter. The application of de-icing salt is thought to have caused deflocculation of the underlying soils, allowing particulates to exit with stormwater as it discharged from the underdrain of the permeable pavements. By autumn, both permeable pavements discharged metals and TSS concentrations similar to others in the literature, suggesting the de-icing effects lasted 3–6 months post-winter. Sodium may substantially affect the performance of permeable pavements following winter de-icing salt application, particularly when 2:1 clay minerals, such as vermiculites and smectites, predominate.

Ivermectin (IVM) is a broad-spectrum antiparasitic drug that is regularly employed in veterinary medicine. In this work, the sorption and desorption of IVM in two Brazilian soils (N1-sand and S2-clay) as well as its leaching capacity, dissipation under aerobic conditions, and degradation in aqueous solution by photocatalysis with TiO₂ in suspension were evaluated. The kinetic sorption curves of IVM were adjusted to a pseudo-second-order model. The sorption and desorption data were well fitted with the Freundlich isotherms in the log form (r > 0.96). The Freundlich sorption coefficient (K F ᵃᵈˢ) and the Freundlich desorption coefficient (K F ᵈᵉˢ) were 77.7 and 120 μg¹⁻¹/ⁿ (cm³)¹/ⁿ g⁻¹ and 74.5 and 138 μg¹⁻¹/ⁿ (cm³)¹/ⁿ g⁻¹, for soils N1 and S2, respectively. A greater leaching capacity of IVM was observed for the sandy soil N1 than for the clay soil S2. Under aerobic conditions, the dissipation (DT₅₀) at 19.3 °C was 15.5 days (soil N1) and 11.5 days (soil S2). Photocatalysis with UVC and TiO₂ in suspension resulted in the degradation of 98 % of IVM (500 μg L⁻¹) in water in 600 s. The toxicity (Daphnia similis) of the solutions submitted to the photocatalytic process was completely eliminated after 10 min.

High amounts of antibiotics are introduced in the soil environment by manure amendment, which is the most important spreading route in soil, with a potential ecotoxicological impact on the environment. The objectives of this study were (a) to assess the tetracycline (Tc) bioavailability in a clay and in a sandy soil, and (b) to evaluate the effects of the Tc and cow manure on the structure and function of soil microbial communities. Clay and sandy soils were spiked with Tc at the concentrations of 100 and 500 mg Tc kg⁻¹ soil, and were amended or not with cow manure. The clay soil showed greater Tc sorption capacity and bioavailable Tc was between 0.157 and 4.602 mg kg⁻¹ soil. Tc dose and time-dependent effects on soil microbial communities were investigated by fluorescein diacetate activity, phospholipid fatty acids analysis, as well as by Biolog community level physiological profile and microbial counts at 2, 7 and 60 days after Tc and/or manure addition. The added Tc caused detrimental effect on the microbial activity and structure, particularly in the short term at the highest concentrations. However, the Tc effect was transient‚ it decreased after 7 days and totally disappeared within 60 days. Cow manure shifted the bacterial structure in both soils, increased the microbial activity in clay soil and contributed to recover the microbial structure in Tc-spiked manure treatments.

Excess nitrogen loading has contributed to the impairment of major watersheds across North Carolina. Onsite wastewater systems (OWS) are a potential source of nitrogen to water resources, but more research is needed to determine their actual contributions, especially in the Piedmont region of the state. The objective of this study was to determine the total dissolved nitrogen (TDN) treatment efficiency of four OWS in clayey soils of the North Carolina Piedmont. Two OWS were conventional style, and two were single-pass sand filters. The four volunteered sites with OWS were instrumented with piezometers (27 total) for groundwater collection and analyses. Piezometers were installed within 1.5 m of each OWS and downgradient from the conventional OWS. Septic tank effluent, groundwater from the piezometers, sand filter effluent, and adjacent surface waters were sampled bimonthly (five times) during 2015. Samples were analyzed for TDN, NO₃ ⁻-N, NH₄ ⁺-N, chloride, dissolved organic carbon, and physical and chemical parameters on each sampling event. Groundwater samples collected 35 m downgradient from the two conventional OWSs had TDN concentrations and masses, on average, of 98 and 70 %, respectively, lower than septic tank effluent. Isotopic analysis of the natural abundance of δ¹⁵N and δ¹⁸O in NO₃ ⁻ in groundwater collected at the conventional OWS sites suggests that denitrification was a mass removal mechanism. The sand filter OWS reduced TDN concentrations by an average of 80 % and mass loading by 50 % prior to discharge to surface waters. Nitrogen management regulations in nutrient-sensitive watersheds should consider the contributions from OWS, especially direct discharge systems like sand filters. Improvements in the TDN treatment efficiency of direct discharge OWS would result in immediate surface water quality improvements.

A field investigation of contaminant transport beneath and around an uncontrolled landfill site in Huainan in China is presented in this paper. The research aimed at studying the migration of some chemicals present in the landfill leachate into the surrounding clayey soils after 17 years of landfill operation. The concentrations of chloride and sodium ions in the pore water of soil samples collected at depths up to 15 m were obtained through an extensive site investigation. The contents of organic matter in the soil samples were also determined. A two-dimensional numerical study of the reactive transport of sodium and chloride ion in the soil strata beneath and outside the landfill is also presented. The numerical modelling approach adopted is based on finite element/finite difference techniques. The domain size of approximately 300 × 30 m has been analysed and major chemical transport parameters/mechanisms are established via a series of calibration exercises. Numerical simulations were then performed to predict the long-term behaviour of the landfill in relation to the chemicals studied. The lateral migration distance of the chloride ions was more than 40 m which indicates that the advection and mechanical dispersion are the dominant mechanism controlling the contaminant transport at this site. The results obtained from the analysis of chloride and sodium migration also indicated a non-uniform advective flow regime of ions with depth, which were localised in the first few metres of the soil beneath the disposal site. The results of long-term simulations of contaminant transport indicated that the concentrations of ions can be 10 to 30 times larger than that related to the allowable limit of concentration values. The results of this study may be of application and interest in the assessment of potential groundwater and soil contamination at this site with a late Pleistocene clayey soil. The obtained transport properties of the soils and the contaminant transport mechanisms can also be used for the design of engineered barriers for the control of the long-term pollution of the site.