Research outline

Measurement of Greenhouse Gases and Nitrogen Oxide Emitted by Earth-Moving Machinery During Different Operations

Figure 1. Example of the changes
to exhaust gas regulations
for construction machinery

Figure 2. Measuring device

  Particulate matter (PM) and NOx (oxides of nitrogen) emitted by earth-moving machinery have been greatly decreased through the strengthening of the Act on Regulation, Etc. of Emissions from Non-road Special Motor Vehicles (commonly known as the “Off-road Law”) (Figure 1).

  While it is anticipated that earth-moving machinery that are equipped with PM and NOx suppression equipment, such as the diesel particulate filters (DPF) after-treatment device and urea selective catalytic reduction (Urea SCR) system, will be introduced into the market in the future when the 2014 interim control measures period ends, the greenhouse gas nitrous oxide (N2O) may be produced in the Urea SCR after-treatment system.

  Moreover, while regulation values in the Off-road Law are defined by engine unit in laboratory testing, the Japanese government is also reviewing domestic vehicle emissions (the 2012 Central Environment Council Review Report) based on regulations introduced in Europe through on-road testing and the same measures may be required for earth-moving machinery in the future. Thus, technology, regulations, and the like related to earth-moving machinery exhaust emissions are changing significantly. To respond quickly and precisely to these changes, the necessity is increasing to put into place methods that measure and evaluate emissions while machinery is operating as well as to clarify the total amount of greenhouse gasses and oxides of nitrogen (NOx) emitted from earth-moving machinery.

  The Public Works Research Institute is therefore developing a method to measure gases emitted from earth-moving machinery during actual operation (Figure 2). In the 2015 study, using a 20-ton hydraulic excavator with DPF installed and a Urea SCR system not installed as a test machine, we measured emissions of carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), nitrous oxide (N2O), and oxides of nitrogen (NOx) when the excavator was digging and loading, levelling the ground, moving, and idling, and we confirmed that gases, such as NOx, emitted from the motor were below the regulation values; the amount of emissions of CO2, CO, and NOx, were large during digging and loading when the engine load was great; emissions of N2O and CH4 were large during idling when the load was small; and greenhouse effect f by N2O and CH4 emissions were less than 1% of greenhouse effect from CO2 emissions.

  In the future, we plan to measure emissions from machines that has Urea SCR system installed.

(Contact: Advanced Technology Research Team)

What Affect Does Water Turbidity Have on Riverbed Algae and Ayu?

Picture 1. The experimental river

Picture 2. Cobblestones placed in the section
used for the experiment.
The perpendicular structures in the
center of the river are the wooden partitions.
The cobblestones can be seen on the
right of the boards.

Picture 3. Cobblestones that the ayu fed
from (right) and didn’t feed from (left).
The experiment was setup so that
the ayu could freely choose the
location to feed at.
We confirmed that the ayu selected
cobblestones with a small amount of
fine sediment build-up
(see the main text for details).
However, we were fascinated to see that
the cobblestones became quite polished due
to the ayu eating the algae off them.

  The Aqua Restoration Research Center is performing research to ascertain the habitat of the various creatures that live in rivers and use the results of that research to formulate methods to help with river management. For example, creatures that live in water are affected by the size of rocks on the riverbed, plants on the shore, geographical features of the riverbed, such as riffles and pools, and the quality and amount of food. Hence, we must consider how to conserve these elements in rivers and put them into practice when performing actual river works.

  One creature that lives in water is the ayu, for which its feed typifies the importance of these elements. Ayu feed on algae that accumulates on rocks on the riverbed. However, if river water becomes turbid and mud and silt build up on the algae, it is believed that the ayu will stop feeding on the algae. Therefore, we conducted experiments to see to what extent ayu stop feeding on the algae if fine sediment like mud and silt builds up on the algae.

  We used the experimental river at the Aqua Restoration Research Center to conduct the experiments. Cobblestones (of a roughly 15 cm diameter) with different amounts of fine sediment, algal biomass, and the like were placed in several sections on riverbed of the experimental river, and ayu feeding was monitored (Pictures 1 and 2). We confirmed that the ayu feed more on cobblestones with a lot of algae and a small amount of fine sediment rather than cobblestones covered in a lot of fine sediment and with a small amount of algae (Picture 3). Furthermore, in sections that had cobblestones covered in a lot of fine sediment and with a small amount of algae, the ayu tended to feed a lot on the algae growing on the wooden boards that were setup to separate the sections. We believe this is because fine sediment did not easily build up on the wooden boards and high quality algae grew on the boards.

  From these experiments we discovered that ayu tend to select feed based on the amount and quality of algae; that is, the amount of fine sediment build-up and biomass. In order to maintain a good amount and quality of algae that ayu feed on, not only must river turbidity levels be low, it is also necessary to ensure the current flows at a sufficient speed and depth, and an appropriate temperature and level of nutrient salt is maintained. In the future, we plan to help with the cultivation of a rich hydrological environment while considering measures for river management that take advantage of these results.

(Contact: Aqua Restoration Research Team)

For Conservation of the Habitats of Organisms in Brackish-Water Regions

Figure 1 The Teshio River

Figure 2 Variation in velocity distribution

Figure 3 Relationship between the elevation
of the salt water/fresh water boundary
and the river discharge

・Characteristics of brackish-water regions

  Brackish-water regions are those where river water and seawater mix. They have complex environments; some of their areas have features of both river water and seawater, and others have features of neither. Many of the organisms that inhabit brackish waters are found nowhere else. Freshwater clams (e.g., Corbicula japonica) are commonly found in such waters. However, they have become less abundant year after year. A moderate degree of salinity is said to be required in order for such clams to reproduce. However, much about the habitat of such clams has not been identified. For this reason, observations were conducted.

・Flow of the Teshio River

  Figure 1 shows the Teshio River and Panke Marsh in Hokkaido. Large freshwater clams are the specialty here. Studies are addressing how flood control safety can be secured while conserving clam resources on the Teshio River. Figure 2 shows the results of continuous observations of flow velocity distribution 7 km upstream from the river mouth of the Teshio River. Greens and blues represent downstreamward flow; yellows and reds represent upstreamward flow. It is found that, in the Teshio River, river water and seawater run in opposite directions as two separate layers: an upper layer and lower one. Also found is the following: in response to rainfall (the upper figure in Figure 2), the downstreamward flow velocity increases and the vertical distribution of flow velocity increases evenly (blue portions in the figure); that is, the flow velocity near the river bed shifts from upstreamward to downstreamward, which means that seawater which had been flowing upstreamward is forced downstreamward by the increase in freshwater. From these results, as shown in Figure 3, a method was developed in which the river discharge is used for estimating the elevation of the boundary between river water and seawater.

・Estimation of the boundary between salt water and fresh water

  The above mentioned method will allow the easy estimation of the elevation of the boundary, whose constant observation is difficult. Moreover, it will be possible to estimate situations in the past and to predict future situations once river discharge has been determined. Also, the continuous estimation of the elevation of the boundary will make it possible to understand how often the river bed at certain elevation has contact with seawater. The considerations above have led to an idea about why habitats suitable for clams have been decreasing: It is thought that increases in river discharge cause the boundary between the saltwater and fresh water to lower and the contact area with saltwater to decrease.

・Future developments

  In fact, increases in river discharge tend to be accompanied by decreases in the catch of clams on the Teshio River. Increases in river discharge are dependent on the quantity of water that pours into the river, i.e., the rainfall. A future challenge is how to conserve the habitat for freshwater clams in response to projected increases in rainfall while maintaining flood control safety.

(Contact: Watershed Environmental Engineering Research Team, Civil Engineering Research Institute for Cold Region)

200-Year Concrete Durability Tests for the First Tokachi Bridge

Photo 1. The first Tokachi Bridge

Photo 2. Exposure test of concrete girders

Figure 1. Compressive strength of concrete

1. Overview of the first Tokachi Bridge

  Construction of the first Tokachi Bridge (Photo 1) was planned by the Obihiro Flood Control Office of the Hokkaido Government in 1933, and the bridge was designed by Dr. Hideo Yokomichi, a Hokkaido Government engineer. That bridge was an RC Gerber girder bridge of 390m in length and 18m in width. It entered service in 1941. At the time of completion, it had the widest span in Japan, its area was the largest in the world, and its allowable compressive stress of concrete was 6.0-6.5 MPa which was among the highest in Japan at that time. Although this highway bridge was still sound when it was dismantled in 1996, its reconstruction was required for flood control safety reasons (because of planning changes from the 1980 revision of the Basic Plan for Implementation of Tokachi River System Construction).

2. Long-term durability test plan for the first Tokachi Bridge

  The first Tokachi Bridge was a valuable concrete structure of the time, since it retained its soundness for more than 50 years under the harsh conditions of temperatures often falling below -20 °C in winter. Moreover, as few studies anywhere in the world have addressed the very long-term strength and durability of concrete, plans were made to preserve some of the main girders in order to conduct tests on durability and other characteristics periodically until 2141, when the bridge will be 200 years old.

  Exposure tests are being conducted on the three inside girders (but not on either of the outside girders) from among the five main girders of the seventh clear span placed in the open air at the Bibi Exposure Test Site (Aza Misawa, Tomakomai City, Hokkaido) of the Civil Engineering Research Institute for Cold Region (Photo 2). Half of the girders are roofed, so that the study can investigate the material with and without exposure to water.

3. Examination results after the start of the tests conducted on the girders placed outside

  Since the first examination, conducted when the bridge was 55 years old and dismantled (1996-1997), 4 physical tests and 2 physicochemical tests have been conducted. Since the concrete girders were placed in the open air, although values differed by measurement points, the compressive strength has been on the increase, mainly at unroofed parts with water exposure (Figure 1). Unhydrated cement and volcanic ash were found inside hardened cement, and it is inferred that these have been contributing to the long-term increase in strength. The average depth of carbonation is about 15mm, and carbonation has scarcely advanced since the first examination.

4. Conclusion

  This study will continue to establish evaluation methods for predicting durability with higher accuracy.

(Contact: Materials Research Team, Civil Engineering Research Institute for Cold Region)