Chemicals leached from concrete are an important way that urban stormwater can influence water quality. In this study, we evaluated the weathering properties of sidewalk samples and tested how carbonation (exposure to elevated levels of gaseous CO₂) can be used to simulate natural aging of concrete. The experiments focused on acid neutralizing capacity (ANC), which is known to be released by concrete in large amounts, and Cr(VI), because of its established carcinogenicity and prevalence in concrete. Chemical weathering of crushed sidewalk samples was measured with upflow recirculating columns carrying simulated acid rain. The weathering rate of ANC from four different samples was found to decrease after 1 week of exposure to a 5% carbon dioxide atmosphere and to remain constant thereafter through 8 weeks of carbonation treatment. In contrast, weathering of chromium (VI) increased after exposure to a 5% carbon dioxide atmosphere for 1 week, though it also remained stable from then through 8 weeks of carbonation. Almost all ions approached steady state after 2.5 h in the recirculation columns irrespective of carbonation time. The main contributor of ANC was Ca²⁺ ion, though this was partly balanced by an unexpectedly high amount of SO₄²⁻. A notable exception to the temporal leaching pattern was largely un-ionized Si, which continued to increase in concentration for at least 3 days of recirculation. Si levels were also higher than is generally observed for aluminosilicate weathering in small watersheds, a novel finding.

Mass transport and residence time of saline water from road salt applications in soil columns composed of Toyoura sand and weathered granite sand were investigated by simulations and in laboratory experiments. Both are sands found in Japan, especially the weathered granite sand. The Toyoura sand has a fairly uniform particle size of 0.1 to 0.4 mm diameter, and a saturated hydraulic conductivity Kₛ = 0.0296 cm/s, while the weathered granite sand used consisted of 13% fine materials (silt and clay) and 87% coarse materials (sand and gravel) with a saturated hydraulic conductivity Kₛ = 0.00393 cm/s. A model was developed to simulate rinsing of brine from a soil column. Assuming a steady, homogeneous flow induced by rainwater infiltration into the soil column, the model was found to match the experimental results for Toyoura sand very well. The normalized salt concentration in the effluent from the 40 cm tall soil column remained constant until about t = 500 s; the concentration then decreased with time quickly and, finally, approached zero. For the weathered granite sand, however, the salt concentrations in the effluent simulated by the model with assumption of homogeneous flow are inconsistent with the experimental data collected. A substantial delay occurs in mass transport of salt from the column, which is different from the Toyoura sand. The delay is attributed to shifts in “active” and “inactive pores” created in the soil due to fine particles such as silt and clay. The proportion of “active pores” and “inactive pores” is not constant but variable with time due to physical and/or electrochemical processes such as pore-size distributions and salt depletion in the soil. A modified model presented, using a time-variable active pore parameter k(t), can reproduce the experimental results for salt mass left in the soil better.

The trace metal pollution in the environment is a highly concerned issue in these days. One of the important causes of trace metal pollution is the exhaust gases released from the vehicles on the roads. These dangerous gases pose life-threatening effects on the forage plants grown along the roadside as these plants are at direct risk to these trace metals. The aims of the present study were to determine the cobalt (Co) concentrations in soil, forages, and blood plasma of the buffaloes and to evaluate the Co deficiencies and toxicities in these samples. All samples were collected from six sites (Faisalabad roadside, Bhalwal roadside, Shaheenabad roadside, Mateela roadside, 50 Chak roadside, and Dera Saudi-control) of Sargodha city. The Co concentrations in these samples were determined by atomic absorption spectrophotometer (AA-6300 Shimadzu Japan). In soil samples, Co level ranged from 1.958 to 3.457 mg/kg in the six sampling sites. The highest Co level was observed at site 6 and the lowest at site 2. In forage samples, Co level ranged from 0.770 to 2.309 mg/kg in the six sampling sites. The highest Co level was observed at site 3 and the lowest at site 2. In blood plasma samples, Co level ranged from 2.644 to 4.927 mg/kg in the six sampling sites. The highest Co level was observed at site 1 and the lowest at site 3. The results showed higher Co values in the samples collected from the site IV while the bioconcentration factor for forage-soil was found highest in the samples collected from Site III. On the other hand, a correlation was found positively significant when soil and forage were correlated, and it was found negatively significant when blood and forage were correlated.

To investigate the emission characteristics of the dissolved N₂O in distilled water and activated sludge mixture, the total volume mass transfer coefficients of N₂O in distilled water and activated sludge mixture were determined by batch experiments. The results indicated a difference between emission processes of N₂O in distilled water and activated sludge mixture. At different initial N₂O concentrations, the total volume mass transfer coefficients of N₂O in distilled water were relatively stable, while the total volume mass transfer coefficients of N₂O in activated sludge mixture increased with increasing initial N₂O concentrations, due to endogenous denitrification by microorganisms in the mixture. Since N₂O was reduced and consumed by heterotrophic bacteria in activated sludge, biochemical reactions were involved in the transfer process of N₂O escaping from the mixture to the atmosphere. Therefore, use of distilled water was suggested to determine the total volume mass transfer coefficient in experiments calculating N₂O emission rates for biological nitrogen removal processes.

This article identifies environmental factors that explain most of the dynamic year-to-year changes in mercury concentrations of young-of-year (YOY) yellow perch (Perca flavescens) in study reservoirs. Mercury concentrations in fish, collected each fall, were measured for 9 years in four reservoirs in northeastern Minnesota. Three to 4 years of data were also obtained for two natural lakes and one other reservoir. Average annual concentrations varied considerably from year to year with a mean change of 39% between consecutive years across all lakes. Those averages show a similar time trend for each lake over the years and suggest that important factors influencing mercury bioaccumulation change annually and are also experienced in common over the study region. Three factors satisfying that description are precipitation depth, water level, and average air temperature. This article reveals that all three have statistically significant correlations with observed mercury concentrations. Moreover, multiple regressions indicate that maximum water levels and average air temperatures explain most of the observed variations. Regressions employing precipitation depth and temperature are less significant.

The use of engineered nanomaterials (ENMs) increases concerns relating to their fate, behavior, and toxicity due to their increased exposure to the environment. These ENMs end up in wastewater treatment plants (WWTPs), and the bacteria in these systems are sensitive to compounds such as heavy metals, which reduces the functionality of the WWTP. In this work, the fate and behavior of Bi₂O₃-BiVO₄ in a WWTP using the OECD 303A guideline was studied. The Bi₂O₃-BiVO₄ NPs were synthesized through a hydrothermal and impregnation method. X-ray diffraction showed monoclinic phases of both Bi₂O₃ and BiVO₄ NPs. The effect of Bi₂O₃-BiVO₄ NPs was monitored using chemical oxygen demand (COD) and 5-day biological oxygen demand (BOD₅). The COD and BOD₅ for the sludge retention time where the NPs were added was > 70%. This showed that the NPs had no effect on the functionality of the treatment processes as it was further affirmed by the TPC measurements. Inductively coupled plasma–optical emission spectroscopy (ICP-OES) showed that the fate of the NPs was through the activated sludge than the effluent, whereby 90% of Bi and V were absorbed in the activated sludge and 10% in the effluent. The results indicate that the NPs have the potential to permeate through the environment segments through the wastewater sludge compared to the effluent. XRD analysis of the test sludge showed that the crystal phases of the heterojunction remained unchanged, and this could ascertain that the treatment conditions did not transform the NPs into toxic forms.

Water resource engineers extensively use regional flood frequency analysis to compute the discharge at ungauged sites with limited flow records in the river basins. Frequency and magnitude are the two important factors required to be analyzed for an effective assessment of flood disaster risk management. Globally, many linear clustering techniques are employed to categorize the watershed which are ineffective when dealing with noise and outliers. The present study overcomes this by proposing a relatively new nonlinear clustering algorithm based on hierarchical estimation of densities (NLCAHD) for the Cauvery basin, where the Homogeneity test (H) is enforced to identify the group of stations with same populations. Discordancy measure is carried out for screening the data in order to eliminate the conflicting sites from the group. The whole basin is classified into six homogeneous clusters, while the goodness of fit measure tests the data to distinguish the preferred distribution for the purpose of calculating the growth curves. A comparative study is made with the other linear algorithms such as K-means and C-means, which reveals the better performance of the proposed nonlinear model for identifying the homogeneous regions, in arriving at precise estimates of flood quantiles for various return periods up to 160 years.

The calix[4]resorcinarene macrocycles are excellent oligomers for the design of amphiphilic derivatives; they can form self-assemblies and stable sensing networks. Owing to their favorable properties, they are the focus of many exploitations and studies ranging from biological controls to heavy metal ion sensing. In this perspective, two calix[4]resorcinarene derivatives, namely: C-dec-9-en-1-ylcalix[4]resorcinarene (ionophore I) and C-undecylcalix[4]resorcinarene (ionophore II) were used to form stable ultra-thin Langmuir monolayer films at the air/water interface; their interactions with different harmful metal cations (Cd²⁺, Pb²⁺, Hg²⁺, and Cu²⁺) were studied and highlighted via the pressure-area (Π-A) isotherms. The obtained results in the current investigation showed a dependence of both macrocycle interactions on the metal cation concentration in the subphase, confirming their complexation. In addition, the ionophore (I) exhibited high selectivity towards Pb²⁺ and Cu²⁺ cations, whereas the ionophore (II) showed tendency to bind with Cu²⁺ cations over others, approving the potential applicability of these macrocycles as ion selective chemical sensors.

Evaluation of the human exposure risk to semivolatile organic compound (SVOC) levels in soil from automobile workshops in Awka was investigated. Soil samples were collected in both dry and rainy seasons. Solvent extraction of the soil samples was carried out using n-hexane: acetone mixture (1:1). Concentrations of SVOCs were determined using gas chromatography-mass spectrometry. There were higher concentrations of SVOCs in the dry season than in the rainy season. The concentrations of the SVOCs were compared with standards for industrial soils. Concentrations of pentachlorophenol in the samples for dry and rainy seasons were below the Canadian Council of Ministers of Environment (CCME) acceptable limit of 7.6 mg/kg. Eighty percent of soil samples for the dry season and all the soil samples for the rainy season had benzo(a)pyrene concentrations lower than the CCME acceptable limit of 0.7 mg/kg. However, incremental lifetime cancer risk (ILCRdₑᵣ) of PAHs and pentachlorophenol for dry seasons exceeded 1.0 × 10⁻⁶ WHO acceptable limit in all the sampling stations, which indicates potential risk via dermal contact. ILCRs of pentachlorophenol were above 1.0 × 10⁻⁶ in 60% of the samples for soil ingestion and all the samples for dermal contact. Hazard quotient of phenolics, phthalates, 1,3-dichlorobenzene and 1,4-dichlorobenzene for soil samples were less than 1 for both seasons, which indicates no non-cancer risk. Results suggest that the SVOCs were highest at the centre of the automobile workshop and the main route of exposure was dermal contact with the soil.

This study proposed the optimization of a laccase-mediator system to reduce pesticide levels (bentazone, carbofuran, diuron, clomazone, tebuconazole, and pyraclostrobin) on aqueous medium. Firstly, the mediator concentration of 1 mM was established (average removal of 36%). After that, seven redox-mediating compounds, namely, 2,20-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, caffeic acid, chlorogenic acid, p-coumaric acid, ferulic acid, gallic acid, protocatechuic acid, and vanillin, were compared regarding their removal efficiency. The highest removal (77%) was achieved with the laccase-vanillin system. After this screening, the optimization was carried out by a 2² full factorial design. Variables under study were the enzyme (laccase) activity and vanillin concentration. Maximum removal (53–85%) was achieved with 0.95 U/mL laccase and 1.8 mM vanillin. Pesticide removal in reaction media was fitted to the first-order kinetics equation with an average half-time life of 2.2 h. This is the first study of the use of this natural compound as a mediator in the degradation of the pesticides under investigation. The results of this study contribute, with alternative methods, to decrease pesticide levels since they are highly persistent in aqueous samples and, as a result, mitigate the environmental impact.