ABSTRACT
This study provides insights regarding the selective metal leaching of brass in various tap water conditions, which benefits water utilities to predict the potential of metal released from brass water meters. The long-term time-dependent selective metal dissolution of brass with various ß phase fractions have not previously been investigated. In this study, a 201-d immersion experiment was carried out in low and high conductivity tap water (LCTW and HCTW, respectively). Three commercialized brass samples in different ß phase fractions (ß = 51%, ß = 43%, ß = 39%), named brass 51, brass 43, and brass 39, respectively, were used. The results showed that brass 51 had the most negative corrosion potential (-0.17 V) and the lowest polarization resistance (8.5 kΩ) compared to brass 43 and brass 39 (-0.04 V and 10.1-14.7 kΩ, respectively) in LCTW. This trend was verified by the 201-d immersion experiment in which brass 51 exhibited the highest zinc leaching rate (21-30 µg L-1 cm-2 d-1), followed by brass 43 and brass 39 (16-23 µg L-1 cm-2 d-1) in both waters. The leaching amounts of lead and copper were extremely low compared to zinc. In LCTW, the uniform corrosion (UC) mechanism dominated from day 1 to day 120. Afterwards, UC was replaced by the galvanic corrosion (GC) mechanism, with the selective leaching coefficient of Zn over Cu (SZn/Cu) increasing from 10 to 25 to 40-80. In HCTW, however, the SZn/Cu reached 300-1000, and the transition of UC to GC occurred earlier on day 30 due to the rapid formation of the ZnO layer on the brass surface that hindered the ion attack.
Subject(s)
Copper , Water , Lead , ZincABSTRACT
This study was designed to evaluate the anti-inflammatory effect of recombinant human kallistatin (Kal) on ulcerative colitis (UC) in the mouse model. Acute colitis was induced by administration of 4% dextran sodium suffate (DSS) to KM mice for 7 days. The mice were then randomized into 5 groups: model control, Kal 0.2 mg·kg(-1)·d(-1), 1.0 mg·kg(-1)·d(-1) and 2.0 mg·kg-1·d(-1) group, salazosulfapyridine (SASP) group. Ten age-matched normal KM mouse were administered with saline in the normal control. The weight, colon length, inflammation factor (MPO/SOD/MDA) and TNF-α/IL-10 levels among the five groups of mice were determined. The results showed that histological index score and MPO/MDA/TNF-α levels of high-dose Kal treatment group and SASP group were significantly lower compared with the model group (P < 0.01), but the weight, colon length, IL-10 level and SOD activity were significant higher than the model group (P < 0.01), approaching the normal group. These parameters showed that Kal can significantly relieve the UC state in a dose-dependent manner. This study demonstrates that Kal significantly remits UC in mice, and participates in the regulation of inflammatory cytokines TNF-α/IL-10 levels and has some antioxidant activity.
