Water Chemistry

Physicochemical means the ______ and ______ properties of water.

physical; chemical

Physicochemical parameters affect aquatic organisms' ______ and ______.

survival; growth

Physicochemical parameters help describe ecosystem ______ and water ______.

health; quality

Physicochemical parameters help managers monitor ______ and guide water ______.

pollution; management

Most light is lost before entering water through ______.

reflection

As light travels deeper into water, its intensity ______ due to absorption and scattering.

decreases

______ occurs when a substance takes in light energy.

Absorption

______ occurs when light changes direction after hitting particles or molecules.

Scattering

______ is the cloudiness of water caused by particles scattering light.

Turbidity

Light scattering is affected by particle size, shape, composition, and ______.

concentration

Turbidity is measured in ______ or ______.

NTU; FNU

A ______ measures turbidity.

turbidimeter

High turbidity means the water is ______.

cloudier

TDS stands for ______ ______ ______.

Total dissolved solids

TSS stands for ______ ______ ______.

Total suspended solids

TDS measures ______ substances in water.

dissolved

TSS measures ______ particles in water.

suspended

The approximate size cutoff separating TDS and TSS is ______ micrometers.

2

Three broad categories of particles in water are ______, ______, and ______.

mineral; organic; biological

The ______ scale is used to classify water color.

Forel-Ule

The Forel-Ule scale helps citizen scientists record and compare water ______ consistently.

color

Clear, dark blue water often indicates relatively ______ water.

clear

Turquoise water can indicate clear water, shallow water, or ______ particles.

carbonate

Teal water can result from a mixture of blue and green coloration from particles or ______.

algae

Tea-brown water often indicates dissolved ______ matter from decaying vegetation.

organic

Red water can indicate pigmented microorganisms or ______ blooms.

algal

Bright pea-soup green water often indicates a dense ______ or cyanobacterial bloom.

algal

______ is when water becomes browner due to increased colored dissolved organic matter.

Browning

Browning in northern temperate lakes is often caused by increased dissolved organic matter entering from ______ and ______.

soils; wetlands

A ______ disk is used to measure water transparency.

Secchi

A Secchi disk is lowered until it disappears, then raised until it ______.

reappears

A deeper Secchi depth indicates greater water ______.

transparency

A shallow Secchi depth usually indicates lower water ______.

transparency

The Beer-Bouguer Law describes how light intensity ______ as it passes through water.

decreases

______ light is light that passes through water.

Transmitted

The light absorption coefficient measures how strongly a substance ______ light per unit distance.

absorbs

Surface water is usually warmest because it receives energy directly from ______.

sunlight

The ______ is the warm upper layer of a stratified lake.

epilimnion

The ______ is the middle layer of a stratified lake where temperature often decreases rapidly.

metalimnion

The ______ is the cold, deep layer of a stratified lake.

hypolimnion

Specific heat capacity is the energy needed to raise a substance's temperature by one degree per unit ______.

mass

Water's high specific heat capacity helps water temperatures change ______.

slowly

Freshwater is densest at approximately ______ °C.

4

Ice floats because it is ______ dense than liquid water.

less

Floating ice insulates the water below and helps prevent lakes from freezing ______.

solid

Conductivity is water's ability to conduct ______.

electricity

Dissolved ______ allow water to conduct electricity.

ions

An electrical conductivity meter or ______ measures conductivity.

probe

Common conductivity units are ______ and ______.

µS/cm; mS/cm

______ is the concentration of dissolved salts in water.

Salinity

Common salinity units include ______ and g/kg.

ppt

More dissolved ions generally mean higher ______.

conductivity

Higher conductivity often indicates higher ______.

TDS

Higher dissolved salt concentrations generally increase ______.

conductivity

Conductivity, salinity, and TDS are related but are not ______.

interchangeable

Freshwater generally has a salinity below about ______ ppt.

0.5

Hypersaline water generally has a salinity above about ______ ppt.

40

Hypersaline lakes form in arid areas because evaporation removes ______ while salts accumulate.

water

______ measures how acidic or basic water is.

pH

A pH below ______ is acidic.

7

A pH of ______ is neutral under typical reference conditions.

7

A pH above ______ is basic.

7

The pH scale is ______, meaning each unit represents a tenfold change in hydrogen ion activity.

logarithmic

A one-unit decrease in pH means hydrogen ion activity increases ______-fold.

ten

Many natural waters have a pH around ______ to ______.

6; 9

More dissolved CO₂ generally ______ pH.

lowers

Photosynthesis usually ______ pH by removing CO₂.

raises

Respiration usually ______ pH by releasing CO₂.

lowers

Bicarbonate has the chemical formula ______.

HCO₃⁻

Carbonate has the chemical formula ______.

CO₃²⁻

Warm water generally holds ______ dissolved CO₂ at equilibrium.

less

______ is water's ability to neutralize added acid.

Alkalinity

pH measures current acidity, while alkalinity measures resistance to ______.

acidification

Hard water contains relatively high concentrations of ______ and ______.

calcium; magnesium

Hardness and alkalinity are often both high, but they measure ______ properties.

different

______ means originating outside the ecosystem.

Allochthonous

______ means originating within the ecosystem.

Autochthonous

An example of allochthonous oxygen is atmospheric oxygen ______ into a lake.

dissolving

An example of autochthonous oxygen is oxygen produced by aquatic plants or ______.

algae

______ water holds more oxygen at saturation.

Colder

Higher pressure generally ______ oxygen solubility.

increases

Saltier water generally holds ______ oxygen at saturation.

less

Oxygen affects decomposition and the cycling of carbon, nitrogen, phosphorus, and other ______.

elements

DO stands for ______ ______.

dissolved oxygen

Dissolved oxygen is reported in ______ and percent saturation.

mg/L

DO in mg/L measures the mass of oxygen per ______ of water.

liter

Percent oxygen saturation compares actual oxygen to the expected ______ concentration.

equilibrium

BOD stands for biological oxygen ______.

demand

BOD measures oxygen consumed by microorganisms breaking down biodegradable ______ matter.

organic

BOD₅ measures biological oxygen demand over ______ days.

five

BOD is commonly measured by comparing dissolved oxygen before and after ______ days of incubation.

five

BOD is reported in ______ of oxygen.

mg/L

High BOD indicates high microbial oxygen ______.

demand

High BOD can deplete dissolved oxygen and stress or ______ aquatic organisms.

kill

DO measures oxygen currently available, while BOD measures oxygen that may be ______.

consumed