Peepers They showed that for jar and peeper

Peepers are
filled with distilled water and when positioned in sediment, equilibrates with
the ambient porewater via passive dissemination. Equilibration/deployment time
can be one hour to several months. Equilibration/deployment time depends on
many factors such as membrane/mesh pore size (45µ or 22µ), peeper volume,
sediment type, chemical of potential concern, temperature, and study objectives
and ranges from days to months (Schumacher,
2002). Following equilibration with ambient porewater, the peeper is
repossessed, and the insides of each dialysis cell are assessed for element of
concern. It is necessary to note that passive sampling devices, such as
peepers, often deliver only projected concentrations that can be affected based
on numerous variables (e.g., temperature, time range, membrane pore size,
etc.). Subsequently, the confidence level for the analytical results for
porewater analyses can fluctuate and should be counted when interpreting data.

Passeport et
al. wrote that their study was the first to apply peepers and CSIA in the
field to investigate the procedures and usefulness of natural recovery (NR) in
sediments at a field site contaminated with pesticides or contaminants such as
chlorinated benzenes and benzene (Passeport et
al., 2016, Passeport et al.,
2014). Although it was the first study that used peepers for NR in
sediments at a field site, before that we had peepers in many other studies
contaminated with benzenes or for evaluating nutrition in water (Peijnenburg et al., 2014, Niederkorn,
2015).  Although Passeport et
al in 2016 determined MCB,
benzene, sulfate, nitrate, and iron across
the sediment profile for different locations (Passeport
et al., 2016), they only mentioned that “the peepers were retrieved
after four weeks, which has been shown to allow volatile organic compounds
concentrations to reach equilibrium”. However, in their studies in 2014, first,
they showed that different contaminants have different equilibration time. They
showed that for jar and peeper concentrations equilibrated within 11 days for MCB
and 1,2- dichlorobenzene, and after 14 days for benzene and toluene, but in
2016, they simply said that they have chosen 4 weeks equilibrium time for
different contaminants. Although, the first study of Passeport et al agrees with the study of
Peijnenburg et al. (Peijnenburg et al.,
2014), the second study is against of it. Peijnenburg et al.
showed that for different metal elements we have different equilibrium times.
Moreover, Passeport et al. (Passeport et al., 2016) mentioned
that nitrate concentrations were below detection at
all depths in the sediment, and maximum concentrations were lower than 1 mg/L
in the surface water. However, Niederkorn et al. (Niederkorn, 2015) mentioned that for distributions of nutrient
elements in the riparian and hyporheic zones, equilibrium time of peepers was
settled in the laboratory to be almost one month. By comparing the study of
Passeport et al. with Niederkorn et al., the study of Niederkorn
is clearer than Passorpt el al. 
They clearly showed that equilibrium of the peepers with the pore water
appeared to occur after third week. As Peijnenburg et al. showed
various passive sampling devices have been developed for metals, and
metalloids. Another method that worked like peeper are suction devices. In
contrast with peepers, suction devices are not full up with analyte-free water
prior to placement and depend on active suction via a vacuum. Suction directly
pulls the porewater from the interstitial sediment spaces into the sampling
container. A tube attached to the buried container allows retrieval of the
porewater sample. Porewater gathered with suction devices are more susceptible
to variations in redox conditions than peepers. (Canadian Council of Ministers
of the Environment, 2016).

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Hexachlorocyclohexanes
(HCHs) are among the most related persistent organic contaminants. Because of
the environmental worries related to HCHs, there is a high demand for studying
their sources, potential sinks, and transformation developments. Inconsistency
in the stable isotope ratios of organic compounds, found both in initially
industrial chemicals and in environmental samples from contaminated sites, can
be clarified by isotope fractionation happening during the synthesis,
purification, handling, storage, application, and eventual degradation of these
elements in the location. To date, most
of the studies aiming to track sources and outcomes of HCHs in the environment
have focused on carbon isotope analysis. In several studies, carbon isotope
ratios from different sources were reported (Li
et al., 2011, Usman et al., 2014, Ivdra et al., 2016).

Chartrand
et al (Dr. Passeport) in 2015 emphasised the application of CSIA to distinguish
among several HCH sources (Chartrand et al.,
2015). The overall objective of their study
was to develop a methodology for applying CSIA to investigate the origin and
outcome of HCH at polluted field locations. They mentioned that because various
HCH isomers have relatively similar ranges of log Koc and log Kow,
their results that carried out for ?-HCH can be generalised for the other HCH
isomers. They stated that CSIA can be used to precisely analyze HCH isomers in
samples from HCH polluted field sites. They presented that they had almost
detection limit of 40 ?g L–1 for ?-HCH ?13C and proposed
that this detection limit is almost acceptable. They also wrote that
groundwater HCH concentrations generally range between 0.1 and 730 ?g L–1.
Although, their result is acceptable, aqueous samples at polluted groundwater
locations can have concentrations meaningfully lower than this value and in
remote areas such as the arctic, or in freshwater and ocean water where the
water is moving this could be challenging.

Renpenning et al. used gas chromatography in combination
with a high-temperature conversion interface, which in the presence of H2
changed organic chlorine to gaseous HCl, and then joined to a dual-detection
system, uniting an ion trap mass spectrometer (MS) and isotope-ratio mass
spectrometer (IRMS). Using GC-HTC-MS/IRMS, chlorine isotope analysis at
enhanced conversion settings resulted in very precise isotope values for
measured reference material with recognised isotope composition, including
chlorinated ethylene, chloromethane, hexachlorocyclohexane, and trichloroacetic
acids. Concerning about detection limits, the detection limit was determined to
be