The management and monitoring of the quality of water resources in the Mekelle area are challenging, due to both geogenic and anthropogenic impacts. The extent of these impacts and the sources of pollution in this area have not been thoroughly investigated. In this article, a mapping of water resources vulnerability was carried out using the DRASTIC method and a modified DRASTIC vulnerability map was produced. Single-parameter and map-removal sensitivity analyses were performed on the relevant rates and weights. A final DRASTIC vulnerability index, varying from 54 to 140, was divided into four vulnerability classes: low (225.7 km2), medium (302.8 km2), high (307.2 km2), and very high (187.6 km2); the values in the parentheses indicate the corresponding areal coverage of each class. Similarly, a modified DRASTIC vulnerability index, ranging from 91 to 192, was divided into four vulnerability classes: low (166.4 km2), medium (266.8 km2), high (338.0 km2), and very high (252.2 km2) Nitrates were used to validate both models. in which moderate positive correlations (with Pearson’s correlation coefficient, r) of 0.681 and 0.702 were calculated for the DRASTIC and modified DRASTIC indices, respectively. A comparison of the two maps showed that significant sources of pollution are located in areas with high to very high vulnerability. The results of this research work can be used for the protection and monitoring of groundwater resources in the Mekelle area.

Trihalomethanes (THMs) are toxic disinfection by-products, formed in the reaction of chlorine with organic matter. This work aimed to study THM formation during a unique case study of managed aquifer recharge (MAR) with chlorinated desalinated seawater. THM formation was tested in the field, along a 3.0 m deep vadose zone gallery. Two small-scale experiments were conducted in the site, with untreated and with bromide spiked desalinated seawater. These were accompanied by a large-scale, ~1-month long operational MAR event. In the small-scale experiments, THM concentrations were shown to increase with bromide concentrations, with increasing dominance of the brominated species. Nevertheless, concentrations remained within the single µg/L range, which is an order of magnitude lower than drinking water regulations. Such low THM concentrations were also determined in the large-scale event. In both cases, THM formation occurred in the ponding water, without significant formation or degradation in the upper 3.0 m of the vadose zone. This study shows that MAR with chlorinated (<0.5 mg/L) desalinated seawater through sandy infiltration basins does not pose a threat to drinking water quality at this site.

Rationale Chloroform, a probable human carcinogen, is commonly detected in various concentration levels in many surface water and groundwater sources. Compound‐specific chlorine stable isotope analysis (Cl‐CSIA) is significant in investigating the fate of chlorinated contaminants in the environment. Analytical conditions should, however, be thoroughly examined for any isotopic fractionation. In this study, we simultaneously optimize three analytical parameters for a robust online Cl‐CSIA of chloroform using the Taguchi design of experiments. Methods For Cl‐CSIA, a purge‐and‐trap autosampler coupled to a gas chromatograph in tandem with a quadrupole mass spectrometer, with electron ionization in selected ion monitoring (SIM) mode, was used. Using the Taguchi method, the dominant parameter affecting the results of Cl‐CSIA for chloroform was identified through concurrent investigation of the signal‐to‐noise ratios (S/N) of three parameters, each at three levels: purging time (5, 10, 15 min), transfer time (80, 120, 160 s), and dwell time (20, 60, 100 ms). Moreover, the optimum combination of the levels was identified. Results The purging time, with a maximum S/N, resulted in the highest influence on the isotope ratios determined. It was further refined through additional experiments to sufficiently extract chloroform from the aqueous phase. Accordingly, 8 min of purging time, 120 s transfer time and 100 ms dwell time were the optimum conditions for Cl‐CSIA of chloroform. Post‐optimization, a precision of ±0.28 ‰ was achieved for 8.4 nmol of chloroform (equivalent to 0.89 μg or approx. 25 nmol Cl‐mass on column). Conclusions A simple online method for Cl‐CSIA of chloroform was optimized with the Taguchi design of experiments. The Taguchi method was very useful for the optimization of the analytical conditions. However, the purging conditions should be fine‐tuned and selected so that sufficient extraction of a target compound is confirmed to acquire a stable and higher precision of the method.

&lt;p&gt;&lt;strong&gt;Natural constraints and the damaged Meli gold mining: forecasting impact on the water resources quality of the Meli area and the surroundings, Tigray&amp;#160; &lt;/strong&gt;&lt;/p&gt; &lt;p&gt;&amp;#160;Kaleab Adhena Abera &lt;sup&gt;1&lt;/sup&gt;, Berhane Abrha &lt;sup&gt;2&lt;/sup&gt;,&amp;#160; Tesfamichael Gebreyohannes &lt;sup&gt;2&lt;/sup&gt;, Abdelwassie Hussien &lt;sup&gt;2&lt;/sup&gt; , &amp;#160;Miruts Hagos &lt;sup&gt;2&lt;/sup&gt;, Gebremedhin Berhane &lt;sup&gt;2&lt;/sup&gt;, and Kristine Walraevens &lt;sup&gt;1&lt;/sup&gt;&lt;/p&gt; &lt;p&gt;&lt;strong&gt;&lt;sup&gt;1&lt;/sup&gt;&lt;/strong&gt;&lt;strong&gt; &lt;/strong&gt;Laboratory for Applied Geology and Hydrogeology, Department of Geology, Ghent University, Belgium (kaleabadhena.abera@ugent.be)&lt;/p&gt; &lt;p&gt;&lt;strong&gt;&lt;sup&gt;2&lt;/sup&gt;&lt;/strong&gt; Department of Geology, School of Earth Science, Mekelle University, Ethiopia&lt;/p&gt; &lt;p&gt;&lt;strong&gt;&amp;#160;&lt;/strong&gt;&lt;/p&gt; &lt;p&gt;&lt;strong&gt;Abstract&lt;/strong&gt;: Meli is the only modern gold mining site in the Tigray region, Northern Ethiopia. Water resources of this area and the surroundings are currently very susceptible to pollution by toxic chemicals than ever before, due to both the natural geological setup of the area and anthropogenic impacts, specifically because of the recent war in northern Ethiopia. The war that was started on November 03, 2020, resulted in the complete destruction of the mining company and tailings dam due to bombing. This potentially could lead to the uncontrolled movement of wastewater from the dam to the environment. The area is characterized by quite complex geology and associated geological structures. In addition to the direct flow of contaminant plumes to downstream areas as surface water, the naturally existing geological fractures, as well as faults, could also act as conduits and increase the infiltration rate of the pollutants to the groundwater resource. In this research, integrated geological, structural, and remote sensing methods were applied. Mapping of geology and geological structures was compiled using both Spot and Landsat satellite images and a physical field survey conducted before the war started. Metavolcanics, metasediments, granite, and sandstone are the identified lithologies in the area. The detailed fracture measurement helps determine the possible flow direction of water and the pollutants. Totally, 110 structural measurements were taken, and the area is affected by a series of Neoproterozoic structures. These include WNW&amp;#8211;ESE striking compression, NE &amp;#8211;SW striking exfoliation fractures, and variably oriented faults. Moreover, structures such as folds, minor strike-slip faults, and joints were observed. The chemicals used in the gold mining company were evaluated. The Meli area tailing dam contains wastewater with a very high concentration of cyanide, caustic soda, heavy metals, and salts which are very toxic. The possible impact of these pollutants on water resources was forecasted and threat-solving mechanisms were proposed. The result of this research work will serve as a baseline for further pollution impact studies at a larger catchment scale and as an input for groundwater resource pollution modeling works of the Meli area and the surroundings.&lt;/p&gt;

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